Pulses of laser light can cause any material – including insulators – to develop a relatively large magnetic moment. This effect, which has been demonstrated for the first time by an international team of researchers, shows that laser light can induce quantum behaviour even at room temperature, not just under the extremely cold conditions usually required. While primarily of interest for fundamental science, the technique could also have applications for faster, more efficient magnetic data storage.
In their experiments, Stefano Bonetti of Stockholm University and the Ca’ Foscari University of Venice and colleagues started with a relatively simple idea. By applying laser light that is both circularly polarized – that is, its polarization traces out a corkscrew-like shape as it propagates – and resonant with the frequency of atomic oscillations within a material, they figured they could drive these oscillations in a circular pattern and thus induce a magnetic moment.
The researchers were encouraged in their thinking by theoretical research, which predicted that atoms moving in circular patterns could indeed induce magnetization in almost any material. “Given my expertise in magnetism and my recent investigations into phonon dynamics (lattice vibrations), I believed that my laboratory would be an ideal setting to experiment with this concept,” Bonetti says.
Polarized light source induces large magnetic moments
Before they could begin, the researchers first had to develop a new polarized light source with a frequency in the required terahertz (far-infrared) range. Once the source was ready, they used it to fire short, intense pulses at a sample of strontium titanate (SrTiO3). At room temperature, this material is a paraelectric diamagnet with a cubic perovskite lattice structure. The researchers chose it because some of its atoms vibrate at terahertz frequencies – specifically, at 3 THz with a bandwidth of 0.5 THz.
The team found that these light pulses induced a phenomenon known as dynamic multiferroicity. Multiferroicity occurs when several properties of a material each have their own preferred states. For example, a multiferroic material might have magnetic moments that point in one direction, and electric charge that also shifts in a certain direction. Importantly, the two phenomena are independent of each other.
Though predicted by theory, this phenomenon had never been demonstrated experimentally. Bonetti reports that the experiment also yielded a surprise: the magnetic moments induced in the material were 10 000 times larger than theory predicts.
Magnetic data storage applications
The researchers say their discoveries could find use in magnetic data storage technologies, where there is great interest in novel methods of encoding magnetic information. This is because magnetic domains could be switched by a fast, lower-power electric field, rather than by an electric current (an energy-intensive and relatively slow process) as conventional domains are.
These two marine giants rarely clash head-to-head. But great white sharks’ hunting habits for large prey can help unlock secrets about how they communicate with each other.
New observations of the flavour composition of atmospheric neutrinos have revealed no conclusive evidence for the minuscule, short-lived black holes that have been predicted by some theories of quantum gravity. The study was done by researchers using the IceCube Neutrino Observatory at the South Pole and the result places some of the tightest constraints ever on the nature of quantum gravity.
Developing a viable theory of quantum gravity is one of the greatest challenges in physics. Today, gravity is described very well by Albert Einstein’s general theory of relativity, which is incompatible with quantum theory. One important difference is that general relativity invokes space–time curvature to explain gravitational attraction while quantum theory is based on flat space–time.
Finding a way forward is challenging because the two theories work at very different energy scales, which makes doing experiments that test theories of quantum gravity very difficult.
“Creative measurements”
“In recent years, creative measurements have been devised to search for the tiny influence of quantum gravity: either via the use of extreme precision in laboratory experiments, or by exploiting the highly energetic particles produced in the distant universe,” explains Thomas Stuttard at the University of Copenhagen, who is a member of the IceCube collaboration.
Among these new theories is the idea that the quantum effects of uncertainty, combined with energy fluctuations in the vacuum of space, could have a tangible effect on the curvature of space–time, as described by general relativity. This could result in the creation of “virtual black holes”. If they exist, these microscopic objects would decay on the order of Planck time. This is about 10−44 s and is the smallest interval of time that can be described by current physical theories.
As a result, virtual black holes would be impossible to detect in the lab. But, if they really exist, researchers predict that they should interact with neutrinos, altering how the particles change flavour states via the phenomenon of neutrino oscillation.
Cubic kilometre of ice
The team searched for evidence of these interactions in data collected by the IceCube Neutrino Observatory, located at the South Pole. As the world’s largest neutrino observatory, IceCube consists of thousands of sensors positioned throughout a cubic kilometre of Antarctic ice.
These sensors detect distinctive flashes of light created by charged leptons that are produced why neutrinos interact with the ice. In this latest study, the team focussed on IceCube detections of high-energy neutrinos produced when cosmic rays interact with Earth’s atmosphere.
Stuttard explains that their search is not the first of its type. “This time, however, we were able to exploit the naturally high energy and large propagation distance of these ‘atmospheric’ neutrinos (rather than earthbound neutrino sources such as particle accelerators or nuclear reactors), as well as the high statistics afforded by the vast detector size. This enabled us to search for effects far weaker than can be probed by any previous study.”
Flavour composition
In their study, the team examined the flavour composition of over 300,000 neutrinos, observed by IceCube over an 8-year period. They then compared this result with the composition they expected to find if the neutrinos had indeed interacted with virtual black holes on their journey through the atmosphere.
Even with the extreme sensitivity offered by IceCube, the results were not any different from the flavour compositions predicted by the current model of neutrino oscillation. For now, this means that the theory of virtual black holes remains without any conclusive evidence.
However, this null result did allow the team to place new limits on the maximum possible strength of black hole–neutrino interactions, which are orders of magnitude more stringent than the limits set in previous studies.
“Aside from quantum gravity, the result also serves to demonstrate that the neutrino does appear to remain truly unperturbed by its environment even after travelling thousands of kilometres, even for neutrino energies exceeding any man-made collider,” says Stuttard. “This was a remarkable demonstration of quantum mechanics over truly macroscopic distances.”
More broadly, the team’s findings place new constraints on the theory of quantum gravity as a whole, constraints that are currently few and far between. “Whilst this work rejects certain scenarios, quantum gravity as a concept is certainly not excluded,” Stuttard adds. “The true nature of quantum gravity may differ from the assumptions made in this study, or the effects may be weaker or more strongly suppressed with energy than previous thought.”
Eager explorer Florence Downs enjoys showcasing the opportunities of engineering to young people. (Courtesy: Florence Downs)
What skills do you use every day in your job?
As an editor, the largest part of my job is doing just that – editing. Most broadly, I spend my time working out how to communicate a story as clearly as possible to the reader. A lot of the time that might just involve a bit of rearrangement and grammatical wrangling. Sometimes it calls for more of a rewrite, and the writer in me can’t help but get excited for those moments. I write shorter pieces for the magazine too, so am trying to develop my approaches to storytelling, interviewing and other more “writerly” skills.
Applying a curious mindset definitely helps me to spot what a story (no matter how long or short) could be missing. Having a scientific background helps a lot with that. Being happy to get stuck into a new subject – if you can call that a skill – is something that’s come in handy in every job I’ve had and that was definitely honed during my physics degree. Without it, it would have been impossible to hop between scientific disciplines and, eventually, find myself in the world of engineering.
As with any job, there’s always a degree of plate spinning. Managing all the smaller aspects of the role – from newsletters to web analytics – is vital.
What do you like best and least about your job?
I love so many things about it. Probably the main one is that I am constantly learning. Every day I get to satisfy my burning curiosities – learn about new technologies and how engineers are making the world a better place. I’m a bit of a magpie so thankfully it’s part and parcel of this job to be drawn to shiny and interesting things.
There’s also the process of seeing an article germinate and eventually take shape. It’s very creative (and a lot of fun) thinking about what to cover and how to guide a piece in the right direction. At the same time, it’s a collective effort, and that comes down to everyone who feeds into it, from our editorial board and team to freelance writers.
I’m grateful to be learning from lots of inspiring people – engineers at all stages of their careers and creative science communicators and writers. Inspiration comes from the other side too. It’s all too often that I’ll interview someone and the amount they’ve achieved before turning 25 will blow my mind.
What I like least is that there’s not enough time in the day to pursue all the article and project ideas we have. It can be a tough call choosing something to prioritize and having to put something else to one side for now.
What do you know today that you wish you knew when you were starting out in your career?
Definitely this: stop worrying so much and know that everything will work out. I’ve learned so much from each stage of my career and would love to tell my past self just to enjoy it. That, incidentally, was also some of the best advice I was given about my PhD viva.
The oncology information system (OIS) lies at the heart of all cancer care, managing the entire clinical pathway – from patient registration, to treatment scheduling and delivery, to follow-up. The software revolution has transformed cancer care from paper-based charts and records to today’s fully digitized processes. But an OIS can do so much more: it can collect data to analyse and learn from, automate tasks and data processing, and intuitively guide users to the information that they need.
A case in point is RayCare, the OIS from oncology software specialist RaySearch Laboratories. RayCare is now used in clinics across three continents, in many cases supporting the entire chain of cancer patient management and in others, coexisting with the hospital information system or working alongside another OIS.
First launched in 2017, RayCare was built from the ground up with the users’ needs in mind. “RayCare originated as a customer need,” explains RayCare chief functionality owner Eeva-Liisa Karjalainen. “We already had our RayStation treatment planning system, which was very well received in terms of its speed and quality, and some of our customers reached out to ask why we didn’t have an OIS software as well. In parallel, we saw a need to combine the OIS and the planning software to achieve important radiotherapy goals such as efficient management of adaptive treatments.”
In response, the company set up a clinical advisory board with various hospitals and spent hundreds of hours working with nine clinics worldwide to define not just how an OIS should perform today, but what they’d like it to do in the future and how to achieve that. The aim was to not build something that already existed, but to create a system that would be useful for the future of cancer care.
Eeva-Liisa Karjalainen “We see the software opportunity as a game changer.” (Courtesy: RaySearch)
At the ESTRO 2024 meeting, the company is launching RayCare 2024A, a major release that will offer a range of top-level enhancements requested by users. This includes a completely new workspace to design and manage treatment courses and scheduling from RayCare. “This brings the advantage that, together with digital workflow support and the integration with RayStation, we can make the whole treatment management process more user-friendly and more efficient,” Karjalainen explains.
And herein lies the key attribute of RayCare: its ability to increase efficiency while maintaining or improving the quality of patient care – a pressing task for cancer clinics worldwide. With an ageing population, hospitals face the challenge of providing high-quality cancer care to an increasing number of patients with a static level of resources. RayCare can help balance available resources against this increasing need for care.
Saving time through automation
RayCare’s “active workflows” provide support for the activities required throughout the entire patient pathway. Unlike prior systems, in which users had to check off finished tasks from a list and inform the next person in the workflow, RayCare actively monitors everything that happens within the system. When a task has been completed, the software automatically opens up the next task in the workflow, assigns that task to the responsible user and informs them that their next step is ready to perform.
This approach reduces lead times between activities and minimizes time spent on manual interactions. Critically, the active workflows also provide a vital safety check, by ensuring that no tasks are forgotten.
To increase efficiency further, RayCare incorporates a wide range of inherent automation features. In general, all data that should be available throughout the RaySearch systems are automatically shared and available where the user needs them, to minimize errors and the need for manual work. For instance, after a planning CT is acquired and received in RayCare, it automatically becomes available within the treatment planning system.
Next-generation OIS RayCare provides support for all tasks throughout the entire treatment pathway. (Courtesy: RaySearch)
There’s also support for automation by use of scripting that allows users to easily configure the software to run specified actions automatically. A typical use case is to instigate generation of a treatment plan in RayStation directly from RayCare, getting it ready for a physician to review without needing any manual interaction.
“A recent example from one of our customers is the performing of scripted quality controls of a treatment plan, checking off a multitude of parameters that were previously checked manually and only pushing the plan onto an additional review if any of those checks failed,” says Karjalainen. “If the plan is within all of the quality measures, no one needs to do anything and it can go straight for approval. Otherwise it can be passed back to another staff member for review.”
Karjalainen points out that while it’s possible to use advances in radiotherapy hardware to treat more patients, for example by delivering radiation faster to reduce fraction times, the big efficiency savings will inevitably come from the automation and organizational support that software such as RayCare brings. “We see the software opportunity as a game changer,” she adds.
Patient-centred approach
Ultimately, RayCare is designed to provide a patient-centred approach based on the concept of a single oncology workflow. Patients often require more than one treatment modality in their cancer care, including surgery or medical oncology as well as radiotherapy. RayCare aims to ensure that staff in all of these disciplines can access the same patient data from one system.
“We want to bring all of these users to RayCare, to centre them around the patient and not have to transport information between different systems or institutions, which is more error prone and also shifts more responsibility to the patient,” Karjalainen explains.
The RayCare architecture already incorporates the framework to enable this type of comprehensive cancer care. And in the future, it will offer specific features such as scheduling for chemotherapy and dedicated workspaces to manage medical oncology and surgical information. This approach should enable better cross-disciplinary communication and reduce the burden on both the hospital and the patient.
“In the long term, the hope is that all activities related to oncology care would be conducted using RayCare. It will not only be the software for the radiotherapy department, but also the software for the surgery and medical oncology departments. Within one system, you could review the toxicities, the data, the outcomes and get a cohesive view on the patient’s history,” says Karjalainen. “At the same time, we are strong advocates for enabling clinics to select the best software or hardware for their clinical needs, independent of vendor. RayCare is designed to communicate with other hospital systems as one of the building blocks of the ecosystem.”
RaySearch’s commitment to supporting open interfaces and open competition is reflected in the company’s co-founding last year of the organization UniteRT, a collaboration of radiation therapy technology vendors that share the mission of complete freedom of choice for the customers.
Echoing this strong focus on supporting future technologies, RaySearch is also working on the automation of online adaptive radiotherapy, a longstanding and important clinical goal for the radiotherapy community. Online adaptive radiotherapy – in which a treatment plan is adapted to the patient’s current anatomy during the course of their treatment – requires the ability to perform extremely fast planning and replanning.
ESTRO 2024 will see the company present some of the first pieces of this project, the newly reworked fast replanning in RayStation. And in one of the next major software releases, this capability will be integrated into the RayCare software. “Truly efficient online adaptive radiotherapy is something that I’m really looking forward to becoming a reality in our RayCare clinics,” says Karjalainen.
Diabetes, weight loss and now heart health: A new family of drugs is changing the way scientists are thinking about obesity — and more uses are on the horizon
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