Atomic clocks are crucial to many modern technologies including satellite navigation and telecoms networks, and are also used in fundamental research. The most commonly used clock is based on caesium-133. It uses microwave radiation to excite an electron between two specific hyperfine energy levels in the atom’s ground state. This radiation has a very precise frequency, which is currently used to define the second as the SI unit of time.

Atomic clocks are currently being supplanted by the optical clocks, which use light rather than microwaves to excite atoms. Because optical clocks operate at higher frequencies, they are much more accurate than microwave-based timekeepers.

Despite the potential of optical atomic clocks, the international community has yet to use one to define the second. Before this can happen, metrologists must be able to compare the timekeeping of different types of optical clocks across long distances to verify that they are performing as expected. Now, as part of an EU-funded project, researchers have made a highly coordinated comparison of optical clocks across six countries in two continents: the UK, France, Germany, Italy, Finland and Japan.

Time flies

The study consisted of 38 comparisons (frequency ratios) performed simultaneously with ten different optical clocks. These were an indium ion clock at LUH in Germany; ytterbium ion clocks of two different types at PTB in Germany; a ytterbium ion clock at NPL in the UK; ytterbium atom clocks at INRIM in Italy and NMIJ in Japan; a strontium ion clock at VTT in Finland; and strontium atom clocks at LTE in France and at NPL and PTB.

To compare the clocks, the researchers linked the frequency outputs from the different systems using two methods: radio signals from satellites and laser light travelling through optical fibres. The satellite method used GPS satellite navigation signals, which were available to all the clocks in the study. The team also used customized fibre links, which allowed measurements with 100 times greater precision than the satellite technique. However, fibres could only be used for international connections between clocks in France, Germany and Italy. Short fibre links were used to connect clocks within institutes located in the UK and Germany.

A major challenge was to coordinate the simultaneous operation of all the clocks and links. Another challenge arose at the analysis stage because the results did not always confirm the expected values and there were some inconsistencies in the measurements. However, the benefit of comparing so many clocks at once and using more than one link technique is that it was often possible to identify the source of problems.

Wait a second

The measurements provided a significant addition to the body of data for international clock comparisons. The uncertainties and consistency of such data will influence the choice of which optical transition(s) to use in the new definition of the second.  However, before the redefinition, even lower uncertainties will be required in the comparisons. There are also several other very different criteria that need to be met as well, such as demonstrating that optical clocks can make regular contributions to the international atomic time scale.

Rachel Godun at NPL, who coordinated the clock comparison campaign, says that repeated measurements will be needed to build confidence that the optical clocks and links can be operated reliably and always achieve the expected performance.  She also says that the community must push towards lower measurement uncertainties to reach less than 5 parts in 10¹⁸ – which is the target ahead of the redefinition of the second.  “More comparisons via optical fibre links are therefore needed because these have lower uncertainties than comparisons via satellite techniques”, she tells Physics World.

Pierre Dubé of Canada’s National Research Council says that the unprecedented number of clocks involved in the measurement campaign yielded an extensive data set of frequency ratios that were used to verify the consistency of the results and detect anomalies. Dubé, who was not involved in the study, adds that it significantly improves our knowledge of several optical frequency ratios and our confidence in the measurement methods, which are especially significant for the redefinition of the SI second using optical clocks.

“The optical clock community is strongly motivated to obtain the best possible set of measurements before the SI second is redefined using an optical transition (or a set of optical transitions, depending on the redefinition option chosen)”, Dubé concludes.

The research is described in Optica.

The post New definition of second ticks closer after international optical-clock comparison appeared first on Physics World.

In materials science, the yield point represents a critical threshold where a material transitions from elastic to plastic deformation. Below this point, materials like glasses can return to their original shape after stress is removed. Beyond it, however, the deformation becomes permanent, reflecting irreversible changes in the material’s internal structure. Understanding this transition is essential for designing materials that can withstand mechanical stress without failure, an important consideration in fields such as civil engineering, aerospace and electronics.

Despite its importance, the yield point in amorphous materials like glasses has remained difficult to study due to the challenges in precisely controlling and measuring the stress and strain required to trigger it. Traditional mechanical testing methods often lack the resolution needed to observe the subtle atomic-scale changes that occur during yielding.

In this study, the authors present a novel approach using X-ray irradiation to induce yielding in germanium-selenium glasses. This method allows for fine-tuned control over the elasto-plastic transition, enabling the researchers to systematically investigate the onset of plastic deformation. By combining experimental techniques with theoretical modelling, they characterize both the thermodynamic behaviour and the atomic-level structural and dynamical responses of the glasses during and after irradiation.

One of the key findings is that glasses processed through this method become stable against further irradiation, an effect that could be highly beneficial in environments with high radiation exposure, such as space missions or nuclear facilities. This work not only provides new insights into the fundamental physics of yielding in disordered materials but also opens up potential pathways for engineering radiation-resistant glassy materials.

Do you want to learn more about this topic?

Theories of glass formation and the glass transition by J S Langer (2014)

The post Probing the yield point in glasses via controlled irradiation appeared first on Physics World.

Quantum repeaters are essential components of quantum networks, enabling long-distance entanglement distribution by temporarily storing quantum states. This temporary storage, facilitated by quantum memory, allows synchronization with other network operations and the implementation of error correction protocols, marking a significant advancement over classical repeaters, which merely amplify and retransmit signals. 

Unlike classical systems, quantum repeaters mitigate photon loss, a major source of error in quantum communication. However, widely known quantum repeater designs often suffer from limitations such as the need for high phase stability and an inability to generate strongly entangled states. 

In this work, the authors propose a novel protocol based on post-matching, a technique originally developed in quantum cryptography to verify and secure transmitted information. Their theoretical framework offers new insights into both quantum communication and cryptographic systems, contributing to the advancement of quantum information theory and technology. 

Do you want to learn more about this topic?

Explore our Focus on Quantum Entanglement: State of the Art and Open Questions

The post Quantum memory meets cryptography appeared first on Physics World.

Nonlinearity refers to behaviour that deviates from a simple, proportional relationship and cannot be accurately described by linear equations. This concept is fundamental to understanding complex systems across various scientific disciplines, including meteorology, epidemiology, chemistry, and quantum mechanics. 

In the field of quantum optics, achieving nonlinearity at the single-photon level is essential for the development of advanced quantum information protocols. Such nonlinearity enables more precise control over information transmission, facilitates faster and more scalable quantum networks, and enhances the security of quantum communication. 

Rydberg atoms, which are atoms in highly excited states, exhibit strong long-range interactions. These interactions, particularly the Rydberg blockade effect, make them promising candidates for inducing strong nonlinear interactions between photons. However, a key challenge lies in achieving this nonlinearity in a controllable and efficient manner, rather than relying on probabilistic or inefficient methods. 

In this work, the authors introduce a novel approach for precisely engineering Rydberg states to enable continuous tuning of single-photon nonlinearity. This tunability represents a significant advancement, with potential applications spanning fundamental physics and the development of next-generation quantum technologies. 

Do you want to learn more about this topic?

Probing quantum correlations in many-body systems: a review of scalable methods by Irénée Frérot, Matteo Fadel and Maciej Lewenstein (2023)

The post Shaping light with engineered Rydberg states appeared first on Physics World.

Supersymmetry is a theoretical framework in which every fermion and boson has a corresponding partner particle, known as a superpartner. These superpartners share the same energy spectrum but differ in their spin properties. The transformations between these particles are governed by mathematical operators called supercharges. Although superpartners have not yet been observed experimentally, their discovery would have significant implications for fundamental physics. 

Twisted bilayer materials, such as graphene and transition metal dichalcogenides, have attracted attention for their unusual electronic and topological properties. In this study, the authors investigate how supersymmetry manifests in these systems by analysing different energy modes associated with twisted bilayers. 

They find that superpartners can exhibit both trivial and nontrivial topological energy bands. Furthermore, they demonstrate that supersymmetry can spontaneously break due to interactions between charged particles, known as Coulomb interactions. 

This research provides new insights into the interplay between topology, symmetry, and interactions in low-dimensional materials, and opens up new possibilities for exploring supersymmetry in condensed matter systems. 

Do you want to learn more about this topic?

Desperately seeking supersymmetry (SUSY) by Stuart Raby (2004)

The post Exploring supersymmetry through twisted bilayer materials appeared first on Physics World.

The Lipkin-Meshkov-Glick model is a theoretical framework used to describe systems of many interacting spins in an external magnetic field. It has been widely applied to study quantum phase transitions, entanglement, and collective spin behaviour. When extended to two modes, the model allows particles to tunnel between two degenerate energy levels, offering insights into quantum systems with multiple states. 

In this study, the authors propose a chiral two mode version of the model using a pair of surface acoustic wave cavities. The chirality in the system preserves the separation between the two modes and prevents them from mixing. By applying specially designed chiral optical drives, the researchers are able to simulate long range asymmetric spin interactions.

This setup enables the simulation of complex quantum phenomena such as time crystal behaviour and ion trap like interactions, without the need for traditional trapping techniques. The work presents a novel approach to engineering and exploring chiral quantum systems using acoustic hybrid platforms.  

Do you want to learn more about this topic?

Time crystals: a review by Krzysztof Sacha and Jakub Zakrzewski (2018)

The post Chiral spin dynamics and time crystals in acoustic systems appeared first on Physics World.

Developing a unified theory for liquid behaviour has long been a challenge due to the complex interactions between particles and the constantly changing dynamic disorder within liquids. Current approaches rely on empirical equations of state derived from experiments, which are often specific to individual systems and cannot be easily transferred to others. Compared to the well-established thermodynamic models for solids and gases, our understanding of liquids remains significantly underdeveloped. 

In this study, the authors take a foundational step toward creating a general equation of state for liquids based on phonon theory. If successful, such a model could have wide-ranging applications in planetary science, industrial processes, chemical engineering, and condensed matter physics. 

The authors provide a detailed explanation of how they approached this complex problem and apply their theoretical framework to experimental data for argon and nitrogen. The results show strong agreement, suggesting that the model has the potential for broad applicability. 

This work represents a significant advance in the theoretical understanding of liquids and opens the door to a more unified and transferable approach to liquid thermodynamics. 

Do you want to learn more about this topic?

Collective modes and thermodynamics of the liquid state by K Trachenko and V V Brazhkin (2015)

The post Toward a unified equation of state for liquids based on phonon theory appeared first on Physics World.

One of the key challenges in building scalable quantum computers is managing noise during operations in order to improve accuracy. Decoherence, which arises from systematic errors and environmental interactions, disrupts quantum information and limits performance. 

Several strategies exist to reduce decoherence. One approach is dynamical decoupling, which averages out noise through carefully timed control pulses. Another is quantum error correction, which detects and corrects faults in a quantum computation. In this study, the authors explore a third approach by leveraging the symmetry of quantum systems to create decoherence-free subspaces. These subspaces isolate quantum information from environmental noise. 

The authors investigate how these decoherence-free subspaces can be integrated with existing error protection techniques. They construct a logical qubit within a decoherence-free subspace using a specially designed pulse sequence. When combined with dynamical decoupling, this method improves the fidelity of quantum states by up to 23% compared to physical qubits. 

This research presents a practical and effective way to incorporate decoherence-free subspaces into quantum error management, offering a promising path toward more reliable quantum computing. 

Do you want to learn more about this topic?

Quantum algorithms for scientific computing by R Au-Yeung, B Camino, O Rathore and V Kendon (2024)

The post Decoherence-free subspaces for scalable quantum error management appeared first on Physics World.

Time crystals are an intriguing state of matter in which a system exhibits periodic motion even in its lowest energy state. This challenges conventional expectations in physics. These systems arise when time translation symmetry is broken, a principle that normally ensures physical laws remain unchanged over time. 

Unlike ordinary systems, time crystals can exhibit persistent oscillations without absorbing net energy over time. This makes them a subject of great interest in condensed matter physics and a promising candidate for future technologies such as quantum computing, sensing, superconductivity, and energy storage. 

Time crystals can be classified as either discrete or continuous. An external periodic force drives discrete time crystals, while continuous time crystals emerge from the collective and self-sustained oscillations of particles. 

In this study, the authors demonstrate a method for converting a continuous time crystal into a discrete one using a process known as subharmonic injection locking. This technique synchronizes the system’s oscillations with a fraction of the driving frequency. It enables the first observation of a transition between continuous and discrete time crystal states in a system that is not in equilibrium. 

This research provides new insights into the behaviour of time crystals and introduces a powerful approach for controlling and manipulating these unusual phases of matter. 

Do you want to learn more about this topic?

Time crystals: a review by Krzysztof Sacha and Jakub Zakrzewski (2018)

The post Manipulating time crystals between continuous and discrete states appeared first on Physics World.

A strange metal is a type of material that exhibits unusual electrical properties, challenging our conventional understanding of how metals conduct electricity.

In these metals, electrons lose their individual identities, acting collectively in a soup, in which all particles are connected through quantum entanglement. 

Prof. Chung, National Yang Ming Chiao Tung University

Many so-called high temperature superconductors, such as doped cuprates, transition from their superconducting state to a strange metal state as they increase in temperature beyond a critical point. (Note that ‘high’ in this context means above −196.2 °C, the boiling point of liquid nitrogen!)

It has long been thought that revealing the mystery of the strange metal state is the key to understanding the mechanism for high-temperature conductivity. This could lead to understanding what would be required to make a truly room temperature superconductor.

In this new paper, the researchers used a cutting-edge theoretical framework to provide a microscopic description of the strange metal state, focusing on how local charge fluctuations near a critical transition, play a key role.

Their theoretical predictions for quantities such as the specific heat coefficient and the single-particle spectral function in the strange metal state agree well with experimental observations.

This work therefore brings us much closer to understanding how superconductivity emerges from the strange metal state in the cuprates – an open problem in condensed matter physics since the 1990s.

The post How does a strange metal become a room temperature superconductor? appeared first on Physics World.

Most complex carbon molecules – such as those necessary for life – actually exist in two forms. The normal one and its mirror image. The left-handed version and the right-handed version.

Despite containing the same atoms, these two molecules usually have vastly different properties. For example, one might be used as a therapeutic drug, while the other could be inactive or even harmful.

Separating them is therefore very important for several reasons, particularly in the fields of chemistry, biology, and medicine. However, due to the lack of differences in the physical properties of the two molecules, this is usually quite difficult.

When any molecule is exposed to light, its quantum energy levels are split apart because of the interaction.

In this paper, the team found that when this light is circularly polarised, the splitting is different for the two mirrored molecules. They also went on to find that this effect led to different photochemical reactions for each molecule, further providing ways to distinguish them.

These effects could then be used as new methods for separating these mirrored molecules in medicine and beyond.

The post What’s the difference between a left-handed molecule and a right-handed one? appeared first on Physics World.

Ever since graphene was first studied in the 2000s, scientists have been interested 2D materials because of their new and interesting electrical and optical properties as well as their potential applications in superconductivity, magnetism and next generation electronics.

In recent years, a new family of these materials has emerged, with a strange new feature: correlated flat bands. Electrons in these bands have the same energy regardless of their movement or position within the material.

In this new work, the researchers used cutting edge theory and computer simulation techniques to understand these types of materials with and predict their properties. In particular, they focused on the interplay between smectic order and topological order.

The term smectic is used when talking about liquid crystals (that’s the same liquid crystal that you find in an LCD TV) . The word just means a state in which the particles are oriented in parallel and arranged in well-defined planes. It’s heavily influenced by the individual particles’ shape structure and charge.

Topological order on other hand is a global type of particle arrangement and is caused by the collective entanglement of all the particles in a system as a whole. It’s very much a quantum phenomenon, and is therefore sometimes unintuitive, strange, and complex.

Usually, these two different types of order are seen to compete with each other, but this study looks at what happens if they exist together.

Based on the results, the team expects several new phase transitions to occur in these systems.

Ultimately, experiments will be required to confirm their predictions. What’s for certain though, is that given how comprehensive this work is, the experimentalists now have a lot of work to do.

The post The different ways of ordering electrons in two dimensional materials. appeared first on Physics World.

Shear-induced structural transitions happen when the structure of a material changes due to the application of force. It’s a phenomenon observed in various systems, including metals like aluminium and iron, molecular crystals such as ice and quartz, and even the Earth’s mantle.

A better understanding of how it works could lead to an improvement in the processing and fabrication of materials with more control on defect formation.

Measuring microscopic processes like this is usually challenging because electron microscopy cannot resolve individual atoms’ motions in bulk solids, and the strong shear force makes things especially difficult.

Here, the researchers used colloidal crystals, allowing them to observe transitions at the single-particle level. As a soft material (one that can easily be deformed), colloid crystals are particularly well-suited for this type of study.

They found that under certain conditions, a liquid layer formed around the growing new crystal structure. This phenomenon is known as “virtual melting” because it occurs well below the effective melting temperature. This liquid layer facilitates the transition by reducing the strain energy at the interface between the old and new crystal structures.

Virtual melting has been proposed in theory and simulation, but had never been directly observed in experiments before. The team’s results not only represent the first experimental observation of this process but also help us to better understand under what circumstances it takes place.

The study has potential applications across various fields, including metallurgy, materials science, and geophysics. The concept of virtual melting could also provide new a new way of thinking about stress relaxation and phase transitions in other systems.

The post Virtual melting accompanies shear-induced crystal transitions appeared first on Physics World.

Protons and neutrons in atomic nuclei are themselves made up of fundamental particles known as quarks. These quarks are held together by the strong interaction via force carriers called gluons.

When heavy atomic nuclei collide at high energies close to the speed of light, these constituent particles can break free from each other. The resulting substance, called a quark–gluon plasma, exhibits collective flowlike behaviour much like an everyday liquid.  Unlike a normal viscous liquid however, these near-perfect fluids lose very little energy as they flow.

Researchers are very interested quark–gluon plasmas because they filled the entire Universe just after the Big Bang before matter as we know it was created.

The CMS Collaboration of scientists at CERN routinely create this state of matter for a very brief moment by colliding large nuclei with each other.  In this paper, the researchers used sound waves as a way of understanding the plasma’s fundamental properties.

Sound is a longitudinal wave that produces compressions and rarefactions of matter in the same direction as its movement. The speed of these waves depends on the medium’s properties, such as its density and viscosity. It can, therefore, be used as a probe of the medium.

The team were able to show that the speed of sound in their quark–gluon plasma was nearly half the speed of light – a measurement they made with record precision compared to previous studies.

The results will help test our theories of the fundamental forces that hold matter together, allowing us to better understand matter in the very early Universe as well as future results at particle colliders.

The post Measuring the speed of sound in quark–gluon plasmas at CERN appeared first on Physics World.

Historically, the majority of studies in condensed matter physics have focused on Hermitian systems – closed systems that conserve energy. However, in reality, dissipative processes or non-equilibrium dynamics are commonly present and so real-world systems are anything but Hermitian.

Recently however people have begun to study non-Hermitian systems in detail and have found a range of interesting topological properties. The term topology was originally used to refer to a branch of mathematics describing geometric objects. Here, however, it means the study of the electron band structure in solids, as well as periodic motion more generally.

Topological arguments are often used to determine universal material properties such as conductivity or magnetic susceptibility. For example, topological insulators are insulating in the bulk but have conducting surface or edge states and can be used in a range of applications, such as quantum computing.

Previous work on non-Hermitian band topology has been restricted to one system at a time, or one property at a time. There’s been no way to link between materials or scenarios and no generalisation.

A research team formed of scientists from the Freie Universität Berlin, the Perimeter Institute, and Stockholm University have now brought everything together by using symmetry arguments to build a general, comprehensive theoretical framework for these exciting new systems.

Predictions made by the authors’ analysis will lead to a better understanding of condensed matter physics and hopefully to new developments in a range of fields including optics, acoustics, and electronics.

The post How to make new materials by predicting their universal electronic structure appeared first on Physics World.

A molecular machine is an assembly of molecular components that produces mechanical movements in response to specific stimuli, similar to everyday objects like hinges and switches.

The power of what can be accomplished with these machines in biology is huge. They are responsible for everything from muscle contraction to DNA replication.

Attaining the same precise control over molecular motion with artificial molecular machines, is currently an active area of research.

Researchers from the August Chełkowski Institute of Physics have been studying one component of these machines – rotary molecular motors. As the name suggests, these machines convert chemical or electrochemical energy into mechanical work by rotating one part relative to another.

The team built their motors out of phenylene molecules within a solid crystal and studied them with a technique called broadband dielectric spectroscopy.

This measures how a material responds to a varying electrical field.  In addition to imaging rotational motion, it can detect interactions between the molecular machine and its environment.

The team found several key markers within their data that reflected the strength of these interactions and therefore how well the molecular rotors were able to rotate. Using these markers will be important in optimising the design of future molecular rotors and brings us one step closer towards artificial molecular machines.

The post How to make a motor the size of a molecule appeared first on Physics World.

New techniques have recently allowed the study of the behaviour of electrons in a similar way to how photons are studied in traditional optics. This emerging area of research – called quantum electron optics – focuses on manipulating and controlling electron waves to create phenomena such as interference and diffraction.

These wavelike electrons are fundamentally quantum in nature. This means that they can emit light in unique ways when shaped and modulated by lasers.

In this work, the team found that the rate of light emission by electrons does not depend on the shape of the electron wave, while the quantum state of the emitted light does.

Essentially, this means that by changing the shape of the electron wave, they can control the characteristics of the light produced. The emitted light exhibits non-classical quantum properties, differing significantly from the light we encounter daily, which follows classical physics rules.

To produce a much stronger photon signal, the researchers also took advantage of superradiance, where multiple electrons emit light in a coordinated manner, resulting in a much stronger emission than the sum of individual emissions. Another purely quantum effect.

The excitement around this research is based on its potential to advance quantum computing and communication by providing new tools for controlling the many quantum states that are required to make them work.

It could also lead to the development of new light sources with special properties, useful in a whole range of scientific and technological applications.

The post How wavelike electrons produce quantum light appeared first on Physics World.

Quantum systems tend to become less “quantum-y” as they interact with their environment. So when developing a mathematical description, it’s usually simpler just to view them as being closed off from their surroundings.

But ‘open’ systems are more realistic and sometimes even more interesting. Open quantum systems can be modelled using the so-called Lindblad equation, which describes the quantum evolution with time as both energy and coherence are lost to the environment.

Scientists from Tsinghua University have expanded the Lindblad equation to track the time evolution in an open system of a quantum property that that has become the hottest topic in condensed-matter physics: topology. Topology has formed the basis of numerous exotic states of matter over the last few decades. Now researchers show that an open system can undergo a topological transition as a result of dissipation, or loss.

The post Tracking the evolution of quantum topology appeared first on Physics World.

Ensuring that different clocks are giving the same time is crucial to enable electronic systems to talk to each other. But what is the cost of this synchronisation at the thermodynamic level?

To answer this question, scientists from the East China Normal University in Shanghai studied two tiny resonating membranes inside an optical cavity. Such optomechanical systems can exhibit quantum properties even on a macroscopic scale, and so they’re an ideal platform for studying ultrasensitive metrology and nonequilibrium thermodynamics. Each of the membranes represented a nanomechanical clock, and the two could be synchronised by increasing their coupling strength by adding more light to the cavity. In this way, the team was able to measure the dependence of the degree of synchronisation on the overall entropy cost.

They hope that this experimental investigation will serve as a starting point to explore synchronisation in navigation-satellite and fibre-optic systems with the aim of improving clock performance.

The post Synchronising two clocks comes at a thermodynamic cost appeared first on Physics World.

The Earth is not a perfect sphere. This makes very precise modelling of our planet’s gravitational field rather tricky. To simplify the maths, scientists can consider a so-called Brillouin sphere: the smallest planet-centred sphere that completely encloses the mass composing the planet. In the case of the Earth, the Brillouin sphere touches the Earth at a single point—the top of Mount Chimborazo in Ecuador. The gravitational field outside the sphere can be accurately simulated by combining a series of simple equations called a spherical harmonic expansion.

But does this still hold true for the field inside the Brillouin sphere, which by definition includes the planet’s surface? Scientists from Ohio State University and the University of Connecticut say “no”. The team presented an analytical and numerical study that demonstrates clearly how and why the spherical harmonic expansion leads to prediction errors.

However, all is not lost. Their ultra-accurate simulations of the gravity field offer guidance toward a new mathematical foundation of gravity modelling. An upgraded simulator, which accounts for density variations within planets, will allow rigorous testing of proposed alternative ways to represent the gravity field beneath the Brillouin sphere.

The post Accounting for planetary density variations helps simulate the gravitational field appeared first on Physics World.

Periodic changes in celestial bodies provide astronomers with a great deal of information about the universe. Sporadic alterations in a star’s brightness could be a signature of it being part of a binary system or indicate the presence of an orbiting planet. And the periodic rotation of objects in the Kuiper Belt tells us about planet formation and the development of our solar system. But these changes are rarely perfectly regular, so astronomers have developed a range of statistical methods to characterize aperiodic observations.

Now, mathematical statisticians from North Carolina State University have compared the robustness of these various methods for the first time. The team investigated the success of four different methods using the same simulated data, and were able to develop a list of recommended usage and limitations that will be essential guidance for all observation astronomers.

The post Periodic changes in celestial bodies give away the galaxy’s secrets appeared first on Physics World.

Are you in the field of AI for science? Now, you have a new place to share your latest work to the world.  IOP Publishing has partnered with the Songshan Lake Materials Laboratory in China to launch a new “diamond” open-access journal to showcase how artificial intelligence (AI) is driving scientific innovation. AI for Science (AI4S) will publish high-impact original research, reviews, and perspectives to highlight the transformative applications and impact of AI.

The launch of the interdisciplinary journal AI4S comes as AI technologies become increasingly integral to scientific research — from drug discovery to quantum computing and materials science.

AI is one of the most dynamic and rapidly expanding areas of research so much so that in the last five years the topic has expanded by nearly ten times the rate of general scientific output.  

Gian-Marco Rignanese from École Polytechnique de Louvain (EPL) in Belgium, who is the editor-in-chief of Al4S, says he is “very excited” by AI’s transformative potential for science. “It is really disrupting the way research is being performed. AI excels at processing and analyzing large volumes of data quickly and accurately,” he says. “This capability enables researchers to gain insights – or identify patterns – that were previously difficult or impossible to obtain.”

Rignanese adds that AI is also accelerating simulations making them “closer to the real world” and large language models and neuro-linguistic programming are changing our way to apprehend the existing literature. “Generative AI holds a lot of promises,” he says.

Rignanese, whose research focuses on investigating and designing advanced materials for electronics, energy storage and energy production in which he uses first-principles simulations and machine learning, says that AI4S “not only targets high standards in terms of quality of the published research” but that it also recognizes the importance of sharing data and software.

The journal recognizes the rapid and multifaceted growth of AI. Notably, in 2025 both the chemistry and physics Nobel prizes went to the science of AI. Research funding is also increasing, with both the US Department of Energy (DOE) and National Science Foundation (NSF) allocating more resources to this field in 2025 than ever before.

In China, AI is emerging as a major priority in which the science community is poised to become a driving force in global development. Reflecting this, AI4S is co-led by editor-in-chief Weihua Wang from the Songshan Lake Materials Laboratory. Songshan Lake Materials Laboratory is a new and leading institute for advanced materials research and innovation that is preparing to focus intensively on AI in the near future.

“Our primary goal with AI for Science is to provide a global forum where scientists can share their cutting-edge research, innovative methodologies, and transformative perspectives,” says Wang “The field of AI in scientific research is not only expanding but also evolving at an unprecedented pace, making it vital for professionals to connect and collaborate.”

Wang expressed his optimistic vision for the future of AI in scientific research. “We want AI for Science to be instrumental in creating a more connected and collaborative global community of researchers,” he adds. “Together, we can harness the transformative power of AI to address some of the world’s most pressing scientific challenges and make the field even more impactful.”

Wang notes that the inspiration behind the journal is the potential impact of AI on scientific discovery. “We believe that AI has the power to revolutionize the way research is conducted,” he says. “By providing a space for open dialogue and collaboration, we hope to enable scientists to leverage AI technologies more effectively, ultimately accelerating innovation and improving outcomes across various fields.”

The scope of AI4S is broad yet focused, catering to a wide array of interests within the scientific community. Wang explains that the journal covers various topics. These include: AI algorithms adapted for scientific applications; AI software and toolkits designed specifically for researchers; the importance of AI-ready datasets; and the development of embodied AI systems. These topics aim to bridge the gap between AI technology and its applications across disciplines like materials science, biology, and chemistry.

AI4S is also setting new standards for author experience. Submissions are reviewed by an international editorial board together with the support of a 22-member advisory board composed of leading scientists and engineers. The journal also promises a rapid turnaround in which once accepted, articles are published within 24 hours and assigned a citable digital object identifier (DOI). In addition, from 2025 to 2027, all article publication charges are fully waived, paid for by the Songshan Lake Materials Laboratory.

AI4S joins a growing number of journals focused on machine learning and AI. This includes the IOP’s Machine Learning Series: Machine Learning: Science and Technology; Machine Learning: Engineering; Machine Learning: Earth; and Machine Learning: Health.

“AI is a new approach to science which is really exciting and holds a lot of promises,” adds Rignanese, “so I am convinced that there is room for a journal accompanying this new paradigm.”

For more information or to submit your manuscript, click here.

The post New open-access journal <I>AI for Science</I> aims to revolutionize scientific discovery appeared first on Physics World.

Ekaterina Shanina, a PhD student at the University of California, Davis, has won the Physics in Medicine & Biology Early Career Researcher Award for her research paper describing a novel brain phantom for positron emission tomography (PET).

Shanina’s study was chosen by Physics in Medicine & Biology’s editorial board as the “best paper” (based on the quality of scientific content and peer review ratings) in the journal’s Early Career Researcher Focus Collection 2024 – a programme established to support and highlight the work of emerging researchers in the medical physics and biomedical engineering community.

“The initiative recognises that early-career researchers often produce cutting-edge, high-impact work but may not yet have widespread visibility,” says Emma Harris, a guest editor on the collection. She explains that while the collection itself showcases a broad range of high-quality work, the award was introduced to further recognise an outstanding contribution from an early-career author – defined this year as someone who completed their PhD in 2018 or later.

“The award serves to highlight exceptional research that stands out for originality, rigour or impact,” says Harris, from the UK’s Institute of Cancer Research and Royal Marsden NHS Trust. “[It will] promote prestige and visibility to the awardee within the international research community, and provide a tangible form of encouragement and recognition that can support academic career progression.”

A new phantom for high-performance PET

In her award winning paper, PICASSO: a universal brain phantom for positron emission tomography based on the activity painting technique, Shanina describes a unique PET phantom called PICASSO and shows how it can be used to model realistic static and dynamic neuroimaging PET studies with excellent quantitative accuracy.

PET imaging offers an invaluable tool for studying the brain, prompting recent interest in developing advanced high-resolution PET scanners dedicated to brain imaging. Such developments create an associated requirement for appropriate imaging phantoms to evaluate and optimize scanner performance. The PICASSO phantom aims to meet these needs.

“UC Davis has been collaborating with Yale University and United Imaging Healthcare to develop a new high-performance brain PET scanner called the NeuroEXPLORER,” Shanina explains. “This scanner has high spatial resolution, which renders the most commonly used anthropomorphic brain phantom – the Hoffman phantom – unsuitable for evaluating its performance. At the same time, we wanted to explore the activity painting technique to create this unconventional phantom for PET imaging.”

Most physical PET phantoms need to be filled with a radioactive solution, which means that they can only model one type of tracer and making changes to the phantom structure is challenging. Such phantoms also require walls to separate different regions, which interferes with quantitative image evaluation, and designs with complex internal cavities are hard to fill without residual air bubbles.

“Our PICASSO phantom overcomes many of these limitations,” says Shanina.

It works by moving a ²²Na point source around within the field-of-view of a PET scanner to “paint” one high-statistics dataset. The motion of the radioactive source is controlled by a robotic arm and contrast levels are defined by computationally sampling the acquired dataset. This approach can efficiently generate phantoms with arbitrary static and dynamic activity distributions in the brain (or other body regions) using a single PET acquisition.

“PICASSO uses a single dataset acquired with a sealed point source to efficiently generate a variety of activity distributions of various complexities and with arbitrarily fine features,” Shanina explains. “There’s no need for cumbersome phantom preparation, there are no cold walls or air bubbles, and the data contain some of the scanner parameters that are difficult to model analytically. We can even use it to model dynamic studies, which is a very challenging task for conventional phantoms.”

Since the paper was published last year, Shanina and colleagues have extended the two-dimensional PICASSO phantom into a 3D version that can generate whole-brain images. “We are also working on an exciting new application for the phantom, using it to model different time-of-flight resolutions of PET scanners,” she says. “To our knowledge, you cannot do this with any other phantoms that are not simulations.”

Shanina tells Physics World that she is “honoured and humbled” to win the Early Career Researcher Award. “I am very happy that this work keeps attracting people’s attention and interest,” she says. “Of course, I don’t do this all by myself. I am very grateful to have Simon Cherry and Jinyi Qi as my advisors supporting and encouraging me on this journey.”

The post PhD student Ekaterina Shanina wins Early Career Researcher Award for PET phantom study appeared first on Physics World.

Two distinctive features of materials known as quantum double-exchange ferromagnets are purely due to quantum spin effects and multiorbital physics, with no need for the lattice vibrations previously invoked to explain them. This theoretical result could lead to new insights into these technologically important materials, as it suggests that some of their properties may arise from interactions hitherto regarded as less important.

Quantum double-exchange ferromagnets have interested scientists since the late 1980s, when physicists led by Albert Fert and Peter Grünberg found that their electrical resistance depends strongly on the magnitude of an external magnetic field. This phenomenon is known as giant magnetoresistance (GMR), and its discovery led to an enormous increase in the storage capacity of modern hard-disk drives, which incorporate GMR structures into their magnetic field sensors. It also led, in 2007, to a Nobel Prize for Fert and Grünberg.

Modelling strategies

Despite these successes, however, physicist Jacek Herbrych of the Institute of Theoretical Physics at Wrocław University of Science and Technology in Poland, who led the new research effort, says that these materials remain somewhat mysterious. “They are theoretically complex, and even today, there is no exact solution to fully solve these systems,” he says.

The key question, Herbrych continues, is how Coulomb interactions between many individual electrons lead to the electron spins in these ferromagnets becoming aligned. “Physicists broadly distinguish two mechanisms,” he explains. “For insulating ferromagnets, the Goodenough-Kanamori rules (based on electron shell occupancy and geometrical arguments) can predict spin alignment. For metallic ferromagnets, the double-exchange mechanism is more appropriate.”

In this latter case, Herbrych explains, the electrons’ motion and the alignment of their spins are intrinsically linked, and the electrons often occupy multiple orbitals. This means they need to be modelled in a fundamentally different way.

The approach Herbrych and his colleagues took, which they describe in Rep. Prog. Phys., was conceptually simple, using a basic yet realistic model of interacting electrons to predict the quantum behaviour of electron spins. “In quantum mechanics, ‘simple’ can quickly become complex, however,” Herbrych notes. “Materials in which the double-exchange mechanism dominates typically exhibit multiorbital behaviour, as mentioned. A minimal model must therefore include electron mobility (or ‘itinerancy’), Coulomb interactions and orbital degrees of freedom.”

Two distinctive features

Herbrych and colleagues identified the two-orbital Hubbard-Kanamori model and the Kondo lattice model with interactions as fitting these requirements. They then used these models to explore two distinctive features of quantum double-exchange ferromagnets.

Both features involve magnons, which are collective oscillations of the materials’ spin magnetic moments. In basic “toy” models of ferromagnets, magnons exhibit a well-defined energy-momentum correspondence known as the dispersion relation. Quantum double-exchange ferromagnets, however, experience a phenomenon known as magnon mode softening: at short wavelengths, their magnons become nearly dispersionless, or momentum independent. “This implies that there are fundamental differences between long- and short-distance spin dynamics,” Herbrych says. “Magnons can travel over long distances but appear localized at short scales.”

The second distinctive feature is called magnon damping. This occurs when magnons lose coherence, meaning that the standard picture of spin flips propagating through the material’s lattice breaks down. “It was previously thought that Jahn-Teller phonons (lattice vibrations) were responsible for these features, and that a classical spin model with phonons would do, but our work challenges this view,” says Herbrych. “We show that these phenomena can arise purely from quantum spin effects and multiorbital physics, without requiring lattice vibrations.”

This is, he tells Physics World, “a remarkable result” as it suggests that some experimental features of quantum double-exchange ferromagnets may arise from interactions previously considered secondary.

Limitations and extensions

The researchers’ present work is restricted to one dimension, and they acknowledge that extending it to two or three dimensions will be a challenge. “Still, our approach offers a conceptual framework that can be approximately extended to higher dimensions,” Herbrych says. “The results not only provide insights into the physics of strongly correlated systems, but also into the interplay of competing phases, such as ferromagnetism, orbital order and superconductivity, observed in these materials.”

The post New mechanism explains behaviour of materials exhibiting giant magnetoresistance appeared first on Physics World.

• To hear the author read an extract from the diaries and reflect on the power of “flash fiction”, check out the Physics World Stories podcast.

The post Heisenberg (not) in Helgoland: where two paths diverge appeared first on Physics World.

As few as five electrons in a semiconductor can exhibit collective behaviour, forming a “Coulomb liquid”, according to researchers in Europe. This extends the study of correlated systems to electron plasmas, and could lead to the study of other exotic phases of matter.

A conventional plasma is a hot, ionized gas of free electrons and positive ions. However, the conduction band of a semiconductor can be considered a one-component plasma. “The effect of the positive charges, as they are locked into the lattice, can be modelled as a uniform background of positive charge,” says team member Vyacheslavs Kashcheyevs of the University of Latvia in Riga. In conventional electronics and semiconductor physics, the conduction band is modelled as a 2D Fermi gas of non-interacting particles, with the Coulomb interaction between the electrons neglected.

The new work focused on electron–electron correlations in the conduction band of gallium arsenide at millikelvin temperatures. The team created a Y-shaped junction. Electrons emitted from a quantum dot were steered through the device by an externally-generated surface acoustic wave (SAW) potential. Part-way through, the path divided, and each electron could either go left or right. The number taking each path was measured by separate quantum dots. The researchers are uncertain, and the model is agnostic, about the extent to which the randomness of left or right arose from quantum mechanics.

When no more than one electron was loaded into each potential minimum, each electron’s choice was random, and the number of electrons counted at each detector after multiple trials could be modelled by a binomial distribution. However, when the researchers tuned the apparatus such that each minimum contained multiple electrons, they found changes in the distribution, with groups of particles less likely to travel to the same detector than would be naïvely expected.

Calculating “cumulants”

The researchers quantified the changes in the distributions using probability theory, calculating “cumulants” of the distributions. “We not only have a cumulant of order two, which would say that two particles are repulsing,” says Hermann Sellier of Institut Néel in Grenoble, France, who led the experimental research. “We have a cumulant of order four for four particles or five for five particles, showing that each particle is talking to all the other particles of the droplet. That’s much stronger and something that has not been measured before.”

This shows, say the researchers, that the 2D electron gas condenses into a strongly correlated Coulomb liquid. This a phase of matter seen in quark–gluon plasma, which is created by the high-energy collision of heavy ions, but never previously identified in electronic matter.

“It’s not like you have atoms which, below a certain temperature, go from the gas phase to the liquid phase because of an attractive interaction,” explains Sellier. “We say that the correlated behaviour is like that of a liquid, but a very special liquid made of repulsive interactions. You push on the right, it pushes on the left.” This is possible only at low temperatures because heating increases the entropy to the point where the correlated state of matter is disfavoured.

The team now wants to look at larger systems approaching the macroscopic limit. They believe similar systems could potentially be used to study many-body physics with other, exotic particles such as anyons – quasiparticles that have properties intermediate to bosons and fermions. Potential technological applications include cold atom quantum simulation.

Considerable interest

Ravi Rau of Louisiana State University in the US says, “It is an interesting method, novel to me, of controlling electron droplets and being able to measure correlations of two, three and up to a maximum of five-particles so far, and addressing the general question of the transition in few-body systems to the statistical limit from explicit dynamics when the number of particles is small”. He adds, “This study, such a system, and the results presented will of course be of considerable interest.”

Rau does however, note that very similar results were achieved in the past in studies of electron collisions with cold atoms and molecules. “[That technique] went under the name of COLTRIMS (cold target recoil-ion momentum spectroscopy) allowed measuring multiple differential cross sections and studying electron–electron correlations in atoms,” he says. “It was the exact analogue of this [work], except that instead of an artificially created and controlled droplet cluster, the electrons were naturally inside the atom.”

The researchers acknowledge the similarity, and thank Rau for bringing the previous work to their attention. However, Kashcheyevs argues that the new work has a generality that allows it to tackle new problems, finding the scaling law that connects the properties of individual electrons to the properties of incompressible Coulomb plasma. “Applying our method at lower temperatures in the future can probe the quantum regime of the phase diagram of this electronic fluid, which is known to support exotic quasiparticles impossible in the 3D vacuum of the Standard Model,” he says.

The research is described in Nature.

The post Coulomb liquid emerges from five electrons in a semiconductor appeared first on Physics World.

New observations support the idea that hot, diffuse threads of gas called cosmic filaments connect clusters of galaxies across the cosmos. That is the conclusion of Konstantinos Migkas at Leiden University and colleagues who say that their study strengthens the idea that much of the normal matter in the universe resides in these structures.

About 5% of the universe’s mass–energy content appears to be baryonic matter – the familiar nuclei and particles that make up atoms and molecules. The rest is believed to be dark energy and dark matter, which are both hypothetical entities. Although they know what baryonic matter is, astronomers have a poor understanding of where much of it is distributed in the universe.

Combining the Standard Model of cosmology with the rigid constraints enforced by observations of cosmic microwave background radiation tells us that structures including stars, black holes, and gas clouds account for around 60% of baryonic matter in the universe. This leaves 40% of baryonic matter unaccounted for.

Previously, cosmologists have argued that this discrepancy could point to a fundamental error in the Standard Model. Recently, however, a growing body of evidence suggests that this matter could be found in vast yet elusive structures, hidden deep within intergalactic space.

On a WHIM

“Large-scale structure simulations of the universe tell us this material should reside within long strings of gas called ‘cosmic filaments’, which connect clusters of galaxies,” Migkas explains. “These missing baryons should be found in the so-called ‘warm-hot intergalactic medium’ (WHIM).”

Despite being extremely sparse, models also predict that the WHIM should be extremely hot – primarily heated by shock waves produced as matter collapses into the large-scale cosmic web, as well as by phenomena including active galactic nuclei and mergers between galaxy clusters. As a result, these cosmic filaments should be emitting a faint yet detectable X-ray signal.

On top of this, the Standard Model places tight theoretical constraints on several physical properties of the WHIM – including its density, temperature, and composition. If X-rays are indeed being emitted by cosmic filaments, these properties should be encoded in their energies, intensities, and frequency spectra – providing astronomers with a clear target in their search for the elusive structures.

These X-ray signals have so far evaded detection because they are extremely faint compared to powerful X-ray signals such as those coming from supermassive black holes

To overcome this, researchers combined data from two of the world’s most advanced X-ray observatories. One is the Suzaku satellite, which was jointly operated by JAXA and NASA and was very good at detecting very faint signals. The other is the ESA’s XMM-Newton, which is very good at observing powerful X-ray signals.

Eliminating black holes

“Combining the two instruments, we carefully and appropriately eliminated the contaminating signal of the black holes throughout our filament,” Migkas explains. “This enabled us to isolate the signal of WHIM and measure its density and temperature for the very first time with such accuracy.”

For an observational target, Migkas’ team searched for cosmic filaments in the Shapley supercluster. This vast structure around 650 million light-years from the Milky Way contains one of the highest concentrations of galaxies in the known universe.

With the combined abilities of Suzaku and XMM-Newton, the researchers detected an X-ray signal indicating the presence of a filament – consistent with predictions of the Standard Model. As they expected, this intergalactic material was extremely hot and sparse: boasting temperatures close to 10 million Kelvin, while containing just around 10 electrons per cubic metre.

“We also found that on average, the filament is around 40 times denser than the average density of the universe – which is pretty empty in general – and around 1000 times less dense than the cores of the four-galaxy cluster it connects,” Migkas describes. Despite having gone undetected so far, this filament also carries a total mass around 10 times that of the Milky Way – making it a vast reservoir of previously hidden matter.

“For the very first time, our work confirms the validity of the predictions of the Standard Model of cosmology regarding the properties of a big part of the missing baryons,” Migkas concludes.

The research is described in Astronomy and Astrophysics.

The post X-rays reveal a cosmic filament appeared first on Physics World.

What skills do you use every day in your job?

Beyond the technical skills tied to specific aspects of my research, my work involves continuously engaging a balance of creativity, critical thinking and curiosity. Creativity alone isn’t enough – in physics, ideas must ultimately stand up to scrutiny. Something is either right or it isn’t, so the goal is to let your imagination run free, while keeping it anchored to scientific rigour.

This balance becomes especially important when it comes to defining your own research direction. Early in your career, you’re usually handed a problem to work on. But, over time, you have to learn to ask your own questions, and formulating good ones is much harder than it sounds.

In the beginning, most of the ideas you come up with turn out either to be flawed or have already been explored. The alternative is to stay in safe territory and do incremental work, which certainly has its place, but it’s difficult to build a research career on that alone.

What helps is staying curious. Finding a meaningful research question often means diving into unfamiliar literature, following sparks of interest, and carving out time to read and think critically. It also means being open to inspiration from other people’s work, not just from research that overlaps with your own, but potentially from entirely different areas.

To me, one of the most precious traits in research is the ability to keep your curiosity alive

I’ve seen how easy it can be to fall into the trap of only valuing ideas that align with your own. To me, one of the most precious traits in research is the ability to keep your curiosity alive: to remain open to surprise, ready to recognize when you’re wrong, be willing to learn, and to be excited by someone else’s discovery, even when it has nothing to do with your own work.

What do you like best and least about your job?

What I like best is the freedom. I get to choose what my next research project will be about, and sometimes that process starts in the simplest of ways. I see an exciting talk at a conference, become fascinated by a new idea, and find myself reading everything I can about it. I’ll come back, pitch it to a student, and if they’re excited too, we explore it together.

When I start something new, I often feel like an imposter, venturing into foreign territory and trying to operate as if I know my way around, but as time goes on, things start to fall into place. Eventually, you reach the point where you create something new that others in the field may find interesting or inspiring in turn. That moment – when a once-distant topic becomes something you have actually contributed to – is deeply rewarding.

What I like least is answering e-mails. As a student, I couldn’t understand why some professors took ages to reply. Now I do. Some days, my inbox just fills up endlessly, and responding thoughtfully to every message would take the whole day. It’s a balancing act, deciding when to say yes and when to say no, and learning to say no in a considerate and fair way takes time and emotional energy. You want to be generous with your time, especially when someone genuinely needs help, but finding this balance can be exhausting. It’s an important part of the job, but I wish it took up a bit less space.

What do you know today that you wish you’d known at the start of your career?

That everyone feels like an imposter sometimes. When I started out as a student, I looked around and assumed everyone else was an expert, while I was just trying to find my way, painfully aware of how much I didn’t know. Over time, you do gain confidence in certain areas, but research constantly pushes you in new directions. That means learning new things, starting from scratch, and feeling like an imposter all over again.

The first time I heard the term “imposter syndrome”, it felt like a revelation. Just knowing that this feeling had a name, and that others experienced it too, was validating. Does this mean I feel less like an imposter now? Not really. But I’ve come to understand that it’s part of the process. It means I’m still learning, still being challenged, still exploring new directions. And if that feeling never goes away entirely, maybe that’s a good sign.

The post Ask me anything: Giulia Rubino – ‘My work involves continuously engaging a balance of creativity, critical thinking and curiosity’ appeared first on Physics World.

Scientists have discovered a centrosymmetric crystal that behaves as though it is chiral – absorbing left- and right-handed circularly-polarized light differently. This counterintuitive finding, from researchers at Northwestern University and the University of Wisconsin-Madison in the US, could help in the development of new technologies that control light. Applications include brighter optical displays and improved sensors.

Centrosymmetric crystals are those that look identical when reflected through a central point. Until now, only non-centrosymmetric crystals were thought to exhibit differential absorption of circularly-polarized light, owing to their chirality – a property that describes how an object differs from its mirror image (such as our left and right hands, for example).

In the new work, a team led by chemist Roel Tempelaar studied how a centrosymmetric crystal made from lithium, cobalt and selenium oxide interacts with circularly polarized light, that is, light with an electromagnetic field direction that rotates in a helical or “corkscrew-like” fashion as it propagates through space. Such light is routinely employed to study the conformation of chiral biomolecules, such as proteins, DNA and amino acids, as they absorb left- and right-handed circularly polarized light differently, a phenomenon known as circular dichroism.

The crystal, which has the chemical formula Li₂Co₃(SeO₃)_4, was first synthesized in 1999, but has not (to the best of the researchers’ knowledge) been discussed in the literature since.

 A photophysical process involving strong chiroptical signals

Tempelaar and colleagues found that the material absorbed circularly polarized light more when the light was polarized in one direction than in the other. This property, they say, stems from a photophysical process involving strong chiroptical signals that invert when the sample is flipped. Such a mechanism is different to conventional chiroptical response to circularly polarized light and has not been seen before in single centrosymmetric crystals.

Not only does the discovery challenge long-held assumptions about crystals and chiroptical responses, it opens up opportunities for engineering new optical materials that control light, says Tempelaar. Potential applications could include brighter optical displays, polarization-dependent optical diodes, chiral lasing, more sensitive sensors and new types of faster, more secure light-based communication.

“Our work has shown that centrosymmetric crystals should not be dismissed when designing materials for circularly polarized light absorption,” Tempelaar tells Physics World. “Indeed, we found such absorption to be remarkably strong for Li₂Co₃(SeO₃)₄.”

The researchers say they took on this study after their theoretical calculations revealed that Li₂Co₃(SeO₃)₄ should show circular dichroism. They then successfully grew the crystals by mixing cobalt hydroxide, lithium hydroxide monohydrate and selenium dioxide and heating the mixture for five days in an autoclave at about 220 °C.

The “tip of the iceberg”

“This crystal is the first candidate material that we resorted to in order to test our prediction,” says Tempelaar. “The fact that it behaved the way it does could just be a great stroke of luck, but it is more likely that Li₂Co₃(SeO₃)₄ is just the tip of the iceberg spanning many centrosymmetric materials for circularly polarized light absorption.”

Some of those compounds may compete with current champion materials for circularly polarized light absorption, through which we can push the boundaries of optical materials engineering, he adds. “Much remains to be discovered, however, and we are eager to progress this research direction further.”

“We are also interested in incorporating such materials into photonic structures such as optical microcavities to amplify their desirable optical properties and yield devices with new functionality,” Tempelaar reveals.

Full details of the study are reported in Science.

The post Symmetric crystals can absorb light asymmetrically appeared first on Physics World.

Quantum technology is rapidly growing with job demand tripling in the US along with venture capital bringing in billions of dollars into the field. That is according to the inaugural Massachusetts Institute of Technology (MIT) Quantum Index Report 2025, which finds, however, that large-scale commercial applications for quantum computing still remain “far off”.

Carried out by the Initiative on the Digital Economy (IDE) at MIT, the report is a result of data collection from academia, industry and policy sources. It sets out to track, measure and visualize trends across several areas such as education, funding, research and development.

One aim of the report is to reduce the complexity of quantum technology and to make the field more accessible and inclusive for entrepreneurs, investors, designers, teachers and decision makers. This in turn, the report says, can help to shape how the technology is developed, commercialized and governed.

The inaugural edition focusses on quantum computing and networks, due to their higher potential impact compared to quantum sensing and simulation. The report says that $1.6bn has been raised by quantum-computing firms in 2024 compared with $621m by quantum-software companies.

The report also finds that jobs in the quantum sector have increased with demand tripling in the US since 2018. This has led to a higher number of education initiatives, with Germany having the most Master’s degrees that include “quantum” in the name.

A ‘community-led project’

The report says that corporations and universities dominate innovation efforts, claiming up to 91% of quantum computing patents. When it comes to academic research, the report finds that while China produces the most papers in quantum computing, US research tends to have a greater impact and influence.

The report also indexes and analyzes published data on over 200 quantum processing units (QPUs) from 17 countries to provide insight into how the performance of different types of quantum computers can be verified. The report finds that despite QPUs making impressive progress in performance, they remain far from meeting the requirements for running large-scale commercial applications such as chemical simulations or cryptanalysis.

Principal investigator Jonathan Ruane from MIT Sloan calls the report a “community-led project” and encourages people to contribute additional data. He says that while a report will be published annually, data on its website will be updated “as often as input is given”.

The post Large-scale commercial applications of quantum computing remain a distant promise, claims report appeared first on Physics World.

Students at the University of Manchester in the UK have created a 30,500-piece LEGO model of the iconic Lovell Telescope to mark the 80th anniversary of the Jodrell Bank Observatory.

Jodrell Bank was established in 1945 in Cheshire in northwest England by the English radio astronomer Bernard Lovell, who became the observatory’s first director, a position he held until 1980.

The Lovell Telescope at Jodrell Bank was built in 1957, and at 76.2 m in diameter was the largest steerable dish radio telescope in the world. That year it also became the only instrument capable of tracking the Soviet Union’s Sputnik 1 rocket.

The Lovell Telescope was originally known as the “250 ft telescope” before becoming the Mark I telescope around 1961 and then in 1987 was renamed the Lovell Telescope.

It was given a Heritage Grade I listing in 1988 and in 2019 Jodrell Bank was granted UNESCO World Heritage status.

To the next level

The LEGO model has been designed by Manchester’s undergraduate physics society and is based on the telescope’s original engineering blueprints. Student James Ruxton spent six months perfecting the design, which even involved producing custom-designed LEGO bricks with a 3D printer.

Ruxton and fellow students began construction in April and the end result is a model weighing 30 kg with 30 500 pieces and a whopping 4000-page instruction manual.

“It’s definitely the biggest and most challenging build I’ve ever done, but also the most fun,” says Ruxton. “I’ve been a big fan of LEGO since I was younger, and I’ve always loved creating my own models, so recreating something as iconic as the Lovell is like taking that to the next level!”

The model will now go on display in a “specially modified cabinet” at the university’s Schuster building. It will take pride of place alongside a decade-old LEGO model of CERN’s ATLAS detector.

“Jodrell Bank has always been a symbol of bold innovation – pushing the boundaries of science and engineering from its earliest days,” notes particle physicist Chris Parkes, who is head of physics and astronomy at Manchester. “What the students have created with this Lego build is a perfect reflection of that spirit. It’s not just a model; it’s a celebration of Manchester’s history of discovery and a testament to the creativity, precision, and ambition that continue to define our scientific community today.”

The post Students mark Jodrell Bank anniversary with epic LEGO model of the Lovell Telescope appeared first on Physics World.

Grid operators around the world are under intense pressure to expand and modernize their power networks. The International Energy Authority predicts that demand for electricity will rise by 30% in this decade alone, fuelled by global economic growth and the ongoing drive towards net zero. At the same time, electrical transmission systems must be adapted to handle the intermittent nature of renewable energy sources, as well as the extreme and unpredictable weather conditions that are being triggered by climate change.

High-voltage capacitors play a crucial role in these power networks, balancing the electrical load and managing the flow of current around the grid. For more than 40 years, the standard dielectric for storing energy in these capacitors has been a thin film of a polymer material called biaxially oriented polypropylene (BOPP). However, as network operators upgrade their analogue-based infrastructure with digital technologies such as solid-state transformers and high-frequency switches, BOPP struggles to provide the thermal resilience and reliability that are needed to ensure the stability, scalability and security of the grid.

“We’re trying to bring innovation to an area that hasn’t seen it for a very long time,” says Dr Mike Ponting, Chief Scientific Officer of Peak Nano, a US firm specializing in advanced polymer materials. “Grid operators have been using polypropylene materials for a generation, with no improvement in capability or performance. It’s time to realize we can do better.”

Peak Nano has created a new capacitor film technology that address the needs of the digital power grid, as well as other demanding energy storage applications such as managing the power supply to data centres, charging solutions for electric cars, and next-generation fusion energy technology. The company’s Peak NanoPlex™ materials are fabricated from multiple thin layers of different polymer materials, and can be engineered to deliver enhanced performance for both electrical and optical applications. The capacitor films typically contain polymer layers anywhere between 32 and 156 nm thick, while the optical materials are fabricated with as many as 4000 layers in films thinner than 300 µm.

“When they are combined together in an ordered, layered structure, the long polymer molecules behave and interact with each other in different ways,” explains Ponting. “By putting the right materials together, and controlling the precise arrangement of the molecules within the layers, we can engineer the film properties to achieve the performance characteristics needed for each application.”

In the case of capacitor films, this process enhances BOPP’s properties by interleaving it with another polymer. Such layered films can be optimized to store four times the energy as conventional BOPP while achieving extremely fast charge/discharge rates. Alternatively, they can be engineered to deliver longer lifetimes at operating temperatures some 50–60°C higher than existing materials. Such improved thermal resilience is useful for applications that experience more heat, such as mining and aerospace, and is also becoming an important priority for grid operators as they introduce new transmission technologies that generate more heat.

“We talked to the users of the components to find out what they needed, and then adjusted our formulations to meet those needs,” says Ponting. “Some people wanted smaller capacitors that store a lot of energy and can be cycled really fast, while others wanted an upgraded version of BOPP that is more reliable at higher temperatures.”

The multilayered materials now being produced by Peak Nano emerged from research Ponting was involved in while he was a graduate student at Case Western Reserve University in the 2000s, where Ponting was a graduate student. Plastics containing just a few layers had originally been developed for everyday applications like gift wrap and food packaging, but scientists were starting to explore the novel optical and electronic properties that emerge when the thickness of the polymer layers is reduced to the nanoscale regime.

Small samples of these polymer nanocomposites produced in the lab demonstrated their superior performance, and Peak Nano was formed in 2016 to commercialize the technology and scale up the fabrication process. “There was a lot of iteration and improvement to produce large quantities of the material while still maintaining the precision and repeatability of the nanostructured layers,” says Ponting, who has been developing these multilayered polymer materials and the required processing technology for more than 20 years. “The film properties we want to achieve require the polymer molecules to be well ordered, and it took us a long time to get it right.”

As part of this development process, Peak Nano worked with capacitor manufacturers to create a plug-and-play replacement technology for BOPP that can be used on the same manufacturing systems and capacitor designs as BOPP today. By integrating its specialist layering technology into these existing systems, Peak Nano has been able to leverage established supply chains for materials and equipment rather than needing to develop a bespoke manufacturing process. “That has helped to keep costs down, which means that our layered material is only slightly more expensive than BOPP,” says Ponting.

Ponting also points out that long term, NanoPlex is a more cost-effective option. With improved reliability and resilience, NanoPlex can double or even quadruple the lifetime of a component. “The capacitors don’t need to be replaced as often, which reduces the need for downtime and offsets the slightly higher cost,” he says.

For component manufacturers, meanwhile, the multilayered films can be used in exactly the same way as conventional materials. “Our material can be wound into capacitors using the same process as for polypropylene,” says Ponting. “Our customers don’t need to change their process; they just need to design for higher performance.”

Initial interest in the improved capabilities of NanoPlex came from the defence sector, with Peak Nano benefiting from investment and collaborative research with the US Defense Advanced Research Projects Agency (DARPA) and the Naval Research Laboratory. Optical films produced by the company have been used to fabricate lenses with a graduated refractive index, reducing the size and weight of head-mounted visual equipment while also sharpening the view. Dielectric films with a high breakdown voltage are also a common requirement within the defence community.

The post Nanostructured plastics deliver energy innovation appeared first on Physics World.

A computational paradigm that can accurately simulate interactions between powerful laser beams and quantum fluctuations in a vacuum has been unveiled by researchers in the UK and Portugal. Led by Lily Zhang at the University of Oxford, the team hopes that their solver could lead to important new insights into the quantum nature of the vacuum.

Quantum electrodynamics (QED) provides a detailed picture of how light and matter interact, and has withstood decades of experimental scrutiny. So far, however, evidence for one of the theory’s key predictions about the nature of the vacuum has remained elusive.

Far from being empty, the vacuum contains a sea of virtual particles that are associated with quantum fluctuations. These particle–antiparticle pairs spontaneously pop into existence before annihilating almost instantly.

QED predicts that virtual particles create nonlinearities within the vacuum that can interact with powerful laser pulses. Underlying this effect is photon–photon scattering, something that particle physicists have tried to observe for several decades in accelerator experiments.

Powerful lasers

“So far, there has been no successful direct tests of photon–photon scattering,” Zhang explains. “However, the global emergence of multi-petawatt lasers has rekindled interest in testing the vacuum using just light itself.” For these experiments to succeed, robust analytical tools which can model the quantum vacuum’s responses to such immensely powerful lasers will be crucial.

So far, researchers have used computational tools that can only model simplified laser setups using 2D models. Zhang’s team addressed these limitations using a numerical technique called the Yee scheme. This is used to solve Maxwell’s equations of electromagnetism and is already widely used in plasma simulation. The method works by separately calculating electric and magnetic fields at staggered times and positions, ensuring greater stability and accuracy.

“The key challenge here is the nonlinear terms, which depend on the electromagnetic fields themselves,” Zhang explains. “We addressed this by combining the Yee scheme with an iterative loop that updates the nonlinear response at each time step until the solution converges.” Once integrated with a state-of-the-art plasma simulation code, the team was left with a fully 3D solver, capable of simulating arbitrary laser interactions within a vacuum.

To test their platform’s performance, they benchmarked it against existing theoretical predictions of vacuum birefringence, which is an effect triggered when a vacuum is distorted by and intense laser pulse that “pumps” the vacuum. In the context of photon–photon scattering, QED predicts that that these distortions will cause the light in a weaker probe beam to split into two separate rays, each with a different polarization and refractive index.

In addition, the team extended their solver to modelling four-wave mixing, which is a more complex effect whereby three input light beams interact in a vacuum to generate a fourth beam.

Tracking asymmetries

“The real-time simulation capability allowed us to track the evolving properties of this output signal, including its size, intensity, and duration, and link these to physical conditions at earlier stages of the interaction,” Zhang explains. “For instance, asymmetries in the signal beam were traced back to asymmetries in the interaction region, which is clearly observable from the simulation data.”

Just as the team hoped, their simulations of birefringence and four-wave mixing both closely matched their theoretical predictions – clearly showcasing their platform’s advanced capabilities.

For now, Zhang and colleagues hope that their solver could vastly reduce the computing resources required to develop robust 3D simulations of laser–vacuum interactions, making them far more efficient and accessible in turn. With its high flexibility in simulating arbitrary laser configurations, the team is now confident that their platform could soon be used to studying a diverse array of quantum vacuum effects – including birefringence, four-wave mixing, and many others.

“Looking ahead, we’re using the solver to explore new regimes, including novel beam profiles and exotic field interactions,” Zhang says. “Its structure also allows for easy extension to other nonlinear theories, such as Born–Infeld electrodynamics and axion-like particle fields. Ultimately, our goal is to create a versatile simulation platform for probing fundamental physics in the quantum vacuum.”

The research is described in Communications Physics.

The post Quantum vacuum fluctuations illuminated by new computational technique appeared first on Physics World.

Superfluorescence is a collective quantum phenomenon in which many excited particles emit light coherently in a sudden, intense burst. It is usually only observed at cryogenic temperatures, but researchers in the US and France have now determined how and why superfluorescence occurs at room temperature in a lead halide perovskite. The work could help in the development of materials that host exotic coherent quantum states – like superconductivity, superfluidity or superfluorescence – under ambient conditions, they say.

Superfluorescence and other collective quantum phenomena are rapidly destroyed at temperatures higher than cryogenic ones because of thermal vibrations produced in the crystal lattice. In the system studied in this work, the researchers, led by physicist Kenan Gundogdu of North Carolina State University, found that excitons (bound electron–hole pairs) spontaneously form localized, coherence-preserving domains. “These solitons act like quantum islands,” explains Gundogdu. “Excitons inside these islands remain coherent while those outside rapidly dephase.”

The soliton structure acts as a shield, he adds, protecting its content from thermal disturbances – a behaviour that represents a kind of quantum analogue of “soundproofing” – that is, isolation from vibrations. “Here, coherence is maintained not by external cooling but by intrinsic self-organization,” he says.

Intense, time-delayed bursts of coherent emission

The team, which also includes researchers from Duke University, Boston University and the Institut Polytechnique de Paris, began their experiment by exciting lead halide perovskite samples with intense femtosecond laser pulses to generate a dense population of excitons in the material. Under normal conditions, these excitons recombine and emit light incoherently, but at high enough densities, as was the case here, the researchers observed intense, time-delayed bursts of coherent emission, which is a signature of superfluorescence.

When they analysed how the emission evolved over time, the researchers observed that it fluctuated. Surprisingly, these fluctuations were not random, explains Gundogdu, but were modulated by a well-defined frequency, corresponding to a specific lattice vibrational mode. “This suggested that the coherent excitons that emit superfluorescence come from a region in the lattice in which the lattice modes themselves oscillate in synchrony.”

So how can coherent lattice oscillations arise in a thermally disordered environment? The answer involves polarons, says Gundogdu. These are groups of excitons that locally deform the lattice. “Above a critical excitation density, these polarons self-organize into a soliton, which concentrates energy into specific vibrational modes while suppressing others. This process filters out incoherent lattice motion, allowing a stable collective oscillation to emerge.”

The new work, which is detailed in Nature, builds on a previous study in which the researchers had observed superfluorescence in perovskites at room temperature – an unexpected result. They suspected that an intrinsic effect was protecting excitons from dephasing – possibly through a quantum analogue of vibration isolation as mentioned – but the mechanism behind this was unclear.

In this latest experiment, the team determined how polarons can self-organize into soliton states, and revealed an unconventional form of superfluorescence where coherence emerges intrinsically inside solitons. This coherence protection mechanism might be extended to other macroscopic quantum phenomena such as superconductivity and superfluidity.

“These effects are foundational for quantum technologies, yet how coherence survives at high temperatures is still unresolved,” Gundogdu tells Physics World. “Our findings provide a new principle that could help close this knowledge gap and guide the design of more robust, high-temperature quantum systems.”

The post Soliton structure protects superfluorescence appeared first on Physics World.

This episode of the Physics World Weekly podcast features Hannah Earley, a mathematician and physicist who is chief technical officer and co-founder of Vaire Computing.

The company is developing hardware for reversible computing, a paradigm with the potential to reduce significantly the energy required to do computations – which could be a boon for power-hungry applications like artificial intelligence.

In a conversation with Physics World’s Margaret Harris, Earley talks about the physics, engineering and commercialization of reversible computing. They also chat about the prototype chips that Vaire is currently working on and the company’s plans for the future.

The post Reversible computing could help solve AI’s looming energy crisis appeared first on Physics World.

A new experiment has offered the clearest view yet of how gluons behave inside atomic nuclei. Conducted at the Thomas Jefferson National Accelerator Facility in the US, the study focused on a rare process called photoproduction. This involves high-energy photons interacting with protons confined in nuclei to produce J/psi mesons. The research sheds light on how gluons are distributed in nuclear matter and is a crucial step toward understanding the nature of protons within nuclei.

While gluons are responsible for generating most of the visible mass in the universe, their role inside nuclei remains poorly understood. These massless particles mediate the strong nuclear force, which binds quarks as well as protons and neutrons in nuclei. Gluons carry no electric charge and cannot be directly detected.

The theory that describes gluons is called quantum chromodynamics (QCD) and it is notoriously complex and difficult to test – especially in the dense, strongly interacting environment of a nucleus. That makes precision experiments essential for revealing how matter is held together at the deepest level.

Probing gluons with light

The Jefferson Lab experiment focused on photoproduction, a process in which a high-energy photon strikes a particle and creates something new, in this case, a J/psi meson.

The J/psi comprises a charm quark and its antiquark and is especially useful for studying gluons. Charm quarks are much heavier than those found in ordinary matter and are not present in protons or neutrons. Therefore, they must be created entirely during the interaction, making the J/psi a particularly clean and sensitive probe of gluon behaviour inside nuclei.

Earlier studies had observed this process using free protons. This new experiment extends the approach to protons confined in nuclei to see how that environment affects gluon behaviour. The modification of quarks inside nuclei has been known since the 1980s and is called the EMC effect. However, much less is known about how gluons behave under the same conditions.

“Protons and neutrons do behave differently when they are bound inside nuclei than they do on their own,” says Jackson Pybus, now a postdoctoral fellow at Los Alamos National Laboratory and one of the experiment’s collaborators. “The nuclear physics community is still trying to work out the mechanisms behind the EMC effect. Until now, the distribution of high-momentum gluons in nuclei has remained an unexplored area.”

Pybus and colleagues used Jefferson Lab’s Experimental Hall D, which delivers an intense beam of high-energy photons. This setup had previously been used to study simpler systems, but this was the first time it was applied to heavier nuclei.

“This study looked for events where a photon strikes a proton inside the nucleus to knock it out while producing a J/psi,” Pybus explains. “By measuring the knocked-out proton, the produced J/psi, and the energy of the photon, we can reconstruct the reaction and learn how the gluons were behaving inside the nucleus.” This was done using the GlueX spectrometer.

Unexpected signals

Significantly, the experiment was accessing the “threshold” region – where the photon has just enough energy to produce a J/psi meson. Near-threshold interactions are particularly valuable because they are highly sensitive to the gluon structure of the target. Creating a heavy charm-anticharm pair requires a large energy transfer so interactions in this region reveal how gluons behave when little momentum is available. This is a regime where theoretical uncertainties in QCD are especially large.

Even more striking were the observations below this threshold. In so-called “sub-threshold” photoproduction, the incoming photon does not carry enough energy to produce the J/psi on its own, so it must draw additional energy from the internal motion of protons or from the nuclear medium itself. This is a well-understood mechanism in principle, but the rate at which it occurred in the experiment came as a surprise.

“Our study was the first to measure J/psi photoproduction from nuclei in the threshold region,” Pybus said. “The data indicate that the J/psi is produced more commonly than expected from protons that are moving with large momentum inside the nucleus, suggesting that these fast-moving protons could experience significant distortion to their internal gluons.”

The sub-threshold results were even harder to explain. “The number of subthreshold J/psi exceeded expectations,” Pybus added. “That raises questions about how the photon is able to pick up so much energy from the nucleus.”

Towards a deeper theory

The results suggest that gluons may be modified inside nuclei in ways that are not described by existing models – suggesting a new frontier in nuclear physics.

“This study has given us the first look at this sort of rare phenomenon that can teach us about the gluon inside the nucleus – just enough data to point to unexpected behaviours,” said Pybus. “Now that we know this measurement is possible, and that there are signs of interesting and unexplored phenomena, we’d like to perform a dedicated measurement focused on pinning down the sort of exotic effects we’re just now glimpsing.”

Follow-up experiments, including those planned at the future Electron-Ion Collider, are expected to build on these results. For now, this first glimpse at gluons in nuclei reveals that even decades after QCD’s development, the inner workings of nuclear matter remain only partially illuminated.

The research is described in Physical Review Letters.

The post Photon collisions provide a glimpse of gluons inside nuclei appeared first on Physics World.

Modern-day communications rely on both fibre-optic cables and wireless radiofrequency (RF) microwave communications. Reaching higher data transmission capabilities is going to require technologies that can efficiently process and convert both optical and microwave signals in a small and energy-efficient package that’s compatible with existing communication networks.

Microwave photonics (MWP) is one of the frontrunning technologies, as it can perform signal processing tasks within the optical domain. Current MWP approaches, however, are typically power intensive and often require many off-chip devices to achieve the desired device capabilities and functionalities – so are not very scalable. Researchers from Belgium and France have now managed to overcome some of these limitations, reporting their findings in Nature Communications.

“We wanted to demonstrate that photonic chips can be as versatile as electronic chips, and one of the fields where the two overlap is that of microwave photonics,” one of the paper’s lead authors, Wim Bogaerts from Ghent University, tells Physics World.

A photonic engine

The researchers have created a photonic engine that processes microwave and optical signals and can convert the signals between the two domains. It is a silicon chip that can generate and detect optical and analogue electrical signals. The chip uses a combination of tuneable lasers (created by using an optical amplifier with on-chip filter circuits), electro-optic modulators and photodetectors, low-loss waveguides and passive components, and a programmable optical filter – which enables the chip to filter signals in both domains.

“We managed to integrate all key functionalities for manipulation of microwave signals and optical signals together on a single silicon chip and use that chip as a programmable engine in different experimental demonstrations,” says Bogaerts.

This setup allowed the researchers to operate the chip as a black-box microwave photonics processor, where the user can process high-frequency RF signals, without being exposed to the internal optical operations (they are hidden).

Optical signals from an external optical fibre are coupled to the chip using a grating coupler and high-speed RF signals are fed into the chip using electro-optic modulators. The RF signal is imprinted into an optical carrier wavelength – which is generated by the on-chip laser – and the signal is then processed on the chip using an optical filter bank. The signal then gets converted back into an RF signal using photodetectors.

All of the signals travelling into and out of the chip can be confined to the RF domain, so the chip doesn’t require any external optical components, unlike many other MWP devices. Moreover, the signals are locally programmed and tuned using thermo-optic phase shifters, enabling users to select any combination of microwave and optical inputs and outputs across the chip.

Extensive applications

The researchers used the photonic engine to create multiple systems that showcase its different optical and RF signal processing capabilities and demonstrate a potential pathway towards smaller MWP systems for high-speed wireless communication networks and microwave sensing applications.

As well as being used for simple light-tuning applications, the chip can also perform optical-to-electrical signal conversion, electrical-to-optical signal conversion, microwave frequency doubling, and microwave/optical filtering and equalization. These functions allow it to be used as a transmitter, receiver, optical/microwave filter, frequency converter or a tuneable opto-electronic oscillator.

When asked about the future of the chip, Bogaerts states that “we plan combine this functionality with more general purpose photonic circuits to enable even more functions and applications to help product developers roll out new photonic products as easily as new electronics products”.

Some other potential applications for the chip that have been touted – but not physically tested in this study – include RF instantaneous frequency measuring, radio-over-fibre links, RF phase tuning, optical and RF switching, optical sensing and signal temporal computing. With so many possibilities, this small-scale and low-power chip could become increasingly important as technologies such as communications advance further.

The post Single silicon chip processes optical and microwave signals appeared first on Physics World.

The development of advance quantum materials and devices often involves making measurements at very low temperatures. This is crucial when developing single-photon emitters and detectors for quantum technologies. And even if a device or material will not be used at cryogenic temperatures, researchers will sometimes make measurements at low temperatures in order to reduce thermal noise.

This R&D will often involve optical techniques such as spectroscopy and imaging, which use lasers and free-space optics. These optical systems must remain in alignment to ensure the quality and repeatability of the measurements. Furthermore, the vibration of optical components must be kept to an absolute minimum because motion will degrade the performance of instrumentation.

Minimizing vibration is usually achieved by doing experiments on optical tables, which are very large, heavy and rigid in order to dampen motion. Therefore, when a cryogenic cooler (cryocooler) is deployed on an optical table it is crucial that it does not introduce unwanted vibrations.

Closed-cycle cryocoolers offer an efficient way to cool samples to temperatures as low as ~2 K to 4 K (−272 °C to −269 °C). Much like a domestic refrigerator or air conditioner, these cryocoolers involve the cyclic compression and expansion of a gas – which is helium in cryogenic systems.

In 2010 Montana Instruments founder Luke Mauritsen, a mechanical engineer and entrepreneur, recognized that the future development of quantum materials and devices would rely on optical cryostats that allow researchers to make optical measurements at very low temperatures and at very low levels of vibration. To make that possible, Mauritsen founded Montana Instruments, which in 2010 launched its first low-vibration cryostats. Based in Bozeman, Montana, the company was acquired by Sweden’s Atlas Copco in 2022 and it continues to develop cryogenic technologies for cutting-edge quantum science and other demanding applications.

Until recently, all of Montana’s low-vibration optical cryostats used Gifford–McMahon (GM) cryocoolers. While these systems provide low temperatures and low vibrations, they are limited in terms of the cooling power that they can deliver. This is because operating GM cryocoolers at higher powers results in greater vibrations.

To create a low-vibration cryostat with more cooling power, Montana has developed the Cryostation 200 PT, which is the first Montana system to use a pulse-tube cryocooler. Pulse tubes offer similar cooling powers to GM cryocoolers but at much lower vibration levels. As a result, the Cryostation 200 PT delivers much higher cooling power, while maintaining very low vibrations on par with Montana’s other cryostats.

Montana’s R&D manager Josh Doherty explains, “One major reason that a pulse tube has lower vibrations is that its valve motor can be ‘remote’, located a short distance from coldhead of the cryostat. This allows us to position the valve motor, which generates vibrations, on a cart next to the optical table so its energy can be shunted to the ground, away from the experimental space on the optical table.”

However, isolating the coldhead from the valve motor is not enough to achieve the new cryostat’s very low levels of vibration. During operation, helium gas moves back and forth in the pulse tube and this causes tiny vibrations that are very difficult to mitigate. Using its extensive experience, Montana has minimized the vibrations at the sample/device mount and has also reduced the vibrational energy transferred from the pulse tube to the optical table. Doherty explains that this was done using the company’s patented technologies that minimize the transfer of vibrational energy, while at the same time maximizing thermal conductance between the pulse tube’s first stage and second stage flanges and the sample/device mounting surface(s). This includes the use of flexible, high-thermal-conductivity links and flexible vacuum bellows connections between the coldhead and the sample/device.

Doherty adds, “we intentionally design the supporting structure to de-tune it from the pulse tube vibration source”. This was done by first measuring the pulse-tube vibrations in the lab to determine the vibrational frequencies at which energy is transferred to the optical table. Doherty and colleagues then used the ANSYS engineering/multiphysics software to simulate designs of the pulse tube support and the sample mount supporting structures.

“We optimized the supporting structure design, through material choices, assembly methods and geometry to mismatch the simulated natural frequencies of the support structure from the dominant vibrations of the source,” he explains.

As a result, the Cryostation 200 PT delivers more that 250 mW cooling power at 4.2 K, with a peak-to-peak vibrational amplitude of less than 30 nm. This is more than three times the cooling power delivered by Montana’s Cryostation s200, which offers a similarly-sized sample/device area and vibrational performance.

The control unit has a touchscreen user interface, which displays the cryostat temperature, temperature stability and vacuum pressure.

The cryostat has multiple feedthrough options that support free-space optics, RF and DC electrical connections, optical fibres and a vacuum connection. The Cryostation 200 PT supports Montana’s Cryo-Optic microscope objective and nanopositioner, which can be integrated within the cryostat. Also available is a low working distance window, which supports the use of an external microscope.

According to Montana Instrument senior product manager Patrick Gale, the higher cooling power of the Cryostation 200 PT means that it can support larger experimental payloads – meaning that a much wider range of experiments can be done within the cryostat. For example, more electrical connections can be made with the outside world than had been possible before.

“Every wire that you bring into the cryostat increases that heat load a little bit,” explains Gale, adding, “By using a 1 W pulse tube, we can cool the system down faster than any of our other systems”. While Montana’s other systems have typical cooling times of about 10 h, this has been reduced to about 6 h in the Cryostation 200. “This is particularly important for commercial users who are testing multiple samples in a week,” says Gale. “Saving that four hours per measurement allows a user to do two tests per day, versus just one per day.”

According to Gale, applications of the Cryostation 200 PT include developing ion traps for use in quantum computing, quantum sensing and atomic clocks. Other applications related to quantum technologies include the development of photonic devices; spin-based devices included those based on nitrogen-vacancies in diamond; quantum dots; and superconducting circuits.

The post New optical cryostat combines high cooling capacity, low vibrations and large sample area appeared first on Physics World.

It was a crisp, chilly morning in Bombay (Mumbai) on 4 December 2024 as delegates made their way to the Indian Institute of Technology, Bombay (IITB) for the opening day of the Women in Optics and Photonics in India-Asia (WOPI) conference. The cool, air-conditioned auditorium was soon packed with almost 300 people – mostly female postgraduate students and researchers – with notepads in hand and lanyards around their necks, eager to learn from the talks ahead.

The three-day event was organized by the IITB and sponsored by institutions, companies and publishers, including IOP Publishing, which publishes Physics World. Aimed at highlighting female voices that often go unheard, the meeting brought together scientists and experts from all over the world.

Yet not everything went according to plan. Although the room was full of curious students, each time the floor opened for questions, nervous glances were exchanged. A few moments of silence lingered as though everyone was waiting for a “better” question to come along. The silence rung of missed opportunities.

This kind of reticence is not new. From classrooms and labs to meetings, we see hesitance by students, and especially female students, everywhere. Growing up, I was told to look up the basics first and only ask so-called “high-level” questions. Good advice in theory but not if you’re already unsure of your place in the room. Add to that a dismissive answer such as “You should have known this by now” and the urge to speak up is nipped right in the bud.

Perhaps the hesitation is understandable. We live in a world where every answer is an Internet search away. Why ask a “silly” question when everyone else probably already knows better – or at least looks like they do? Yet asking questions is a fundamental part of learning. Science doesn’t move forward because people stay quiet until they have the perfect question, it moves because someone dares to ask – even when they aren’t sure.

Another contributing factor to such silence is imposter syndrome –  the feeling that you don’t deserve to be there and aren’t good at your work. Multiple studies have shown that women consistently score higher on measures of imposter syndrome than men. Women in technical fields such as engineering, science and maths also report lower self-efficacy than men, regardless of actual performance or ability – so not only do we question whether we belong but we also underestimate ourselves.

All of this means women are less likely to ask questions or speak up when uncertain. But for a scientist, uncertainty is the norm. We spend most of our time sitting with the unknown and with it the need to ask questions and chip away at it. Yet the very process of scientific inquiry can feel to women like a trap.

A new way

So what can we do differently? Events like WOPI create time and space not just for presenting research and innovation, but for mentorship, for insight into the real-world machinery of science. It’s not just about “What are you working on?” but also “Where are you heading, and who’s with you?”

WOPI 2024 modelled a new approach to inclusivity by running panel sessions that included the families of successful leaders to showcase the kind of support that is necessary to “make it”. Women were invited who fearlessly shared their stories of pivoted careers and/or failures, while acknowledging the challenges that they encountered along the way. It reminded us that you don’t just grow by knowing but by asking, exploring and doing.

But we need to do more. Encouraging young female scientists today means accounting for the weight of cultural expectations, social atmosphere and gender-based tendencies. Events and conferences need to go beyond formal settings to highlight not just the science but the scaffolding that holds it all together – networking, informal mentorship, vulnerability and visibility. This must be integrated into the very fabric of all scientific events, not just those for women.

The real pulse of the WOPI conference was in the moments after the talks – students lining up to talk to speakers. Nervous, curious and determined to ask their questions anyway. That moment stayed with me. It was steadfast curiosity that had survived immense self-doubt and fear of speaking in front of an audience.

Hopefully at the next WOPI meeting to be held in India in 2026, students will be much more confident in asking questions. So, to every student: don’t wait for the perfect moment. Ask the question that’s been sitting at the edge of your mind, making you wonder. After all, that is where discovery starts.

The post Speak up: why your questions matter more than ever appeared first on Physics World.

A new statistical physics analysis of the French labour market has revealed that the vast majority of occupations act as so-called condenser occupations. These structural bottlenecks attract workers from many other types of jobs, but offer very limited options for further mobility. This finding could help explain why changing jobs in response to shocks like technological change or economic crises is often so slow, say scientists at the Ecole Polytechnique in Paris, who performed the study.

“By pinpointing where mobility gets ‘stuck’, we provide a new lens to understand – and potentially improve – the adaptability of labour markets,” explains Max Knicker of the EconophysiX lab, who led this new research effort.

Knicker and colleagues borrowed a concept from statistical physics known as the “fitness and complexity” framework, which is used to study the structure of economies and ecosystems. In their work, the researchers treated occupations as nodes in a network and analysed real transition data – that is, how workers actually moved between different jobs in France from 2012 to 2020. The data came from official sources and were provided by the National Institute of Statistics and Economic Studies through the Secure Data Access Center (CASD).

“In total, we had access to information on about 30 million workers and employers in France, whom we tracked over a 10-year period,” explains Knicker. “We also worked with high-resolution administrative data from INSEE (the French National Institute of Statistics), and specifically the BTS-Postes (Base Tous Salariés-Postes).”

Two key metrics

The researchers assigned a score for each occupation and developed two key metrics. These were: accessibility, which measures how many different jobs “feed into” a given occupation; and transferability, which measures how many different jobs someone can move to from that occupation.

By studying the network of job flows with these metrics, they observed hidden patterns and constraints in occupational mobility and identified four main clusters, or categories, of jobs. The first are defined as “diffuser” occupations and have high transferability but low accessibility. “These require specific training to enter, but that training allows for transitions to many other areas,” explains Knicker. “This means they are more difficult to get into, but offer a wide range of exit opportunities.”

The second group are called “channel” occupations. These are both hard to enter and offer few onward transitions, he says. “They often involve highly specialized skills, such as specific types of machine operation.”

The third class are “hubs” and are both widely accessible and highly transferable – so much so that they act as central nodes in the transition network. “This class includes jobs like retail sellers, which require a broad, yet not highly specialized skill set,” says Knicker.

The fourth and last category is the most common type and dubbed “condenser” occupations. “Workers from many different backgrounds can easily enter these, but they can’t easily get out afterwards,” explains Knicker. “Examples of such jobs include caregiving roles.”

A valuable tool for policymakers

The researchers explain that they undertook their study to answer a broader question: why do some economies adapt quickly to shocks while others struggle? “Despite increasing attention to issues like automation or the green transition, we still lacked tools to diagnose where worker mobility breaks down,” says Knicker. “A key challenge was dealing with the sheer complexity and size of the labour flow data – we analysed over 250 million person–year observations. Another was interpreting the results in a meaningful, policy-relevant way, since the transition network is shaped by many intertwined factors like skill compatibility, employer preferences and worker choices.”

The new framework could become a valuable tool for policymakers seeking to make labour markets more responsive, he tells Physics World. “For example, by identifying specific occupations that function as bottlenecks, we can better target reskilling efforts or job transition programmes. It also suggests that simply increasing training isn’t enough – what matters is where people are coming from and where they can go next.”

The researchers also showed that the structure of job transitions itself can limit mobility. Over time, this could inform the design of more strategic labour interventions, especially in the face of structural shocks like AI-driven job displacement, states Knicker.

Looking forward, the Ecole Polytechnique team plans to extend its approach by studying how the career paths of individual workers evolve over time. This, says Knicker, will be done using panel data, not just year-to-year snapshots as in the present analysis. He and his colleagues are also interested in linking their metrics to wage dynamics – for example, does low transferability make workers more vulnerable to exploitation or wage stagnation? “Finally, we hope to explore whether similar bottleneck structures exist in other countries, which could reveal whether these patterns are universal or country-specific.”

Full details of the analysis are reported in the Journal of Statistical Mechanics Theory and Experiment.

The post Statistical physics reveals how ‘condenser’ occupations limit worker mobility appeared first on Physics World.