Damage to the spinal cord can disrupt communication between the brain and body, with potentially devastating effects. Spinal cord injuries can cause permanent loss of sensory, motor and autonomic functions, or even paralysis, and there’s currently no cure. To address this inadequacy, researchers at Chalmers University of Technology in Sweden and the University of Auckland in New Zealand have developed an ultrathin bioelectric implant that improved movement in rats with spinal cord injuries.
The implant works by delivering a low-frequency pulsed electric field (EF) across the injury site – an approach that shows promise in promoting regeneration of axons (nerve fibres) and improving outcomes. Traditional EF treatments, however, rely on metal electrodes that are prone to corrosion. In this latest study, described in Nature Communications, the researchers fabricated stimulation electrodes from sputtered iridium oxide films (SIROF), which exhibit superior durability and stability to their metal counterparts.
The team further enhanced the EF treatment by placing the electrodes directly on the spinal cord to deliver stimulation directly to the injury site. Although this subdural positioning requires more invasive surgery than the epidural placement used previously, it should deliver stronger stimulation while using an order of magnitude less power than epidural electrodes.
“We chose subdural stimulation because it avoids the shunting effect of cerebrospinal fluid, which is highly conductive and can weaken the electric field when electrodes are placed epidurally,” explains co-lead researcher Lukas Matter from Chalmers University of Technology. “Subdural placement puts the electrodes directly on the spinal cord, allowing for stronger and more precise stimulation with lower current.”
Restoring motionand sensation
Matter and collaborators tested the implants in rats with spinal cord injuries, using 200 μm diameter SIROF electrodes placed on either side of the injury site. The animals received 1 h of EF treatment daily for the first 7–11 days, and then on weekdays only for up to 12 weeks.
To compare EF treatment with natural healing (unlike humans, rats can recover after spinal cord injury), the researchers assessed the hind-limb function of both treated and non-treated rats. They found that during the first week, the non-treated group recovered faster than the treated group. From week 4 onwards, however, treated rats showed significantly improved locomotion and coordination compared with non-treated rats, indicating greater recovery of hind-limb function.
The treated rats continued to improve until the end of the study (week 12), while non-treated rats showed no further improvement after week 5. At week 12, all of the treated animals exhibited consistent coordination between front and hind limbs, compared with only 20% of non-treated rats, which struggled to move smoothly.
The team also assessed the recovery of mechanical sensation by touching the animals’ paws with a metal filament. Treated rats withdrew their paws faster than non-treated rats, suggesting a recovery of touch sensitivity – though the researchers note that this may reflect hypersensitivity.
“This indicates that the treatment supported recovery of both movement and sensation,” says co-lead researcher Bruce Harland from the University of Auckland in a press statement. “Just as importantly, our analysis confirmed that the treatment did not cause inflammation or other damage to the spinal cord, demonstrating that it was not only effective but also safe.”
Durable design
To confirm the superior stability of SIROF electrodes, the researchers performed benchtop tests mimicking the in vivo treatment. The SIROF electrodes showed no signs of dysfunction or delamination, while platinum electrodes corroded and failed.
“Platinum electrodes are prone to degradation over time, especially at high charge densities, due to irreversible electrochemical reactions that cause corrosion and delamination, ultimately compromising their long-term stability,” says Matter. “SIROF enables reversible charge injection through surface-bound oxidation states, minimizing the generation of potentially toxic stimulation byproducts and enhancing their stimulation capabilities.”
In contrast with previous studies, the researchers did not see any change in axon density around the lesion site. Matter suggests some possible reasons for this finding: “The 12-week time point may have been too late to capture early signs of regeneration. The injury itself created a large cystic cavity, which may have blocked axon growth. Also, electric field treatment might improve recovery through protective or alternative mechanisms, not necessarily by promoting new axon growth”.
The researchers are now developing an enhanced version of the implant with larger electrodes based on the conductive polymer PEDOT, which enables higher charge densities without compromising biocompatibility. This will allow them to assess a broader range of field strengths and pulse durations in order to determine the optimal treatment conditions. They also plan to test the implant in larger animal models, and hope to elucidate the mechanisms underlying the locomotion improvement using ex vivo models.
As for the possibility of future clinical implementation, senior author Maria Asplund of Chalmers University envisions a temporary, possibly biodegradable, subdural implant that safely delivers low-frequency EF therapy. “This could be implanted early after spinal cord injury to support axon regrowth and reduce the follow-up damage that occurs after the injury itself,” she tells Physics World.
Scientists in Switzerland and Japan have uncovered what they say is the first direct evidence that materials at the bottom of the Earth’s mantle flow like a massive river. This literally “ground-breaking” finding, made by comparing seismic data with laboratory studies of materials at high pressures and temperatures, could reshape our understanding of the dynamics at play deep within our planet’s interior.
For over half a century, one of the greatest unresolved mysteries in geosciences has been a phenomenon that occurs just above the boundary where the Earth’s solid mantle meets its liquid core, says Motohiko Murakami, a geophysicist at ETH Zurich who led the new research effort. Within this so-called D” layer, the velocity of seismic waves passing through the mantle abruptly increases, and no-one is entirely sure why.
This increase is known as the D” discontinuity, and one possible explanation for it is a change in the material the waves are travelling through. Indeed, in 2004, Murakami and colleagues at the Tokyo Institute of Technology’s department of earth and planetary sciences suspected they’d uncovered an explanation along just these lines.
In this earlier study, the researchers showed that perovskite – the main mineral present in the Earth’s lower mantle – transforms into a different substance known as post-perovskite under the extreme pressures and temperatures characteristic of the D” layer. Accordingly, they hypothesized that this phase change could explain the jump in the speed of seismic waves.
Nature, however, had other ideas. “In an experimental study on seismic wave speeds across the post-perovskite phase transition we conducted three years later, such a sharp increase in velocity was not observed, bringing the problem back to square one,” Murakami says.
Post-perovskite crystals line up
Subsequent computer modelling revealed a subtler effect at play. According to these models, the hardness of post-perovskite materials is not fixed. Instead, it depends on the direction of the material’s crystals – and seismic waves through the material will only speed up when all the crystals point in the same direction.
In the new work, which they detail in Communications Earth & Environment, Murakami and colleagues at Tohoku University and the Japan Synchrotron Radiation Research Institute confirmed this in a laboratory experiment for the first time. They obtained their results by placing crystals of a post-perovskite with the chemical formula MgGeO3 in a special apparatus designed to replicate the extreme pressures (around 1 million atmospheres) and temperatures (around 2500 K) found at the D” depth nearly 3000 km below the Earth’s surface. They then measured the velocity of lab-produced seismic waves sent through this material.
These measurements show that while randomly-oriented crystal samples do not reproduce the shear wave velocity jump at the D” discontinuity, crystals oriented along the (001) slip plane of the material’s lattice do. But what could make these crystals line up?
Evidence of a moving mantle
The answer, Murakami says, lies in slow, convective motions that cause the lower mantle to move at a rate of several centimetres per year. “This convection drives plate tectonics, volcanic activity and earthquakes but its effects have primarily been studied in the shallower region of the mantle,” he explains. “And until now, direct evidence of material movement in the deep mantle, nearly 3000 km beneath the surface, has remained elusive.”
Murakami explains that the post-perovskite mineral is rigid in one direction while being softer in others. “Since it naturally aligns its harder axis with the mantle flow, it effectively creates a structured arrangement at the base of the mantle,” he says.
According to Murakami, the discovery that solid (and not liquid) rock flows at this depth does more than just solve the D” layer mystery. It could also become a critical tool for identifying the locations at which large-scale mantle upwellings, or superplumes, originate. This, in turn, could provide new insights into Earth’s internal dynamics.
Building on these findings, the researchers say they now plan to further investigate the causes of superplume formation. “Superplumes are believed to trigger massive volcanic eruptions at the Earth’s surface, and their activity has shown a striking correlation — occurring just before two major mass extinction events in Earth’s history,” Murakami says.
Being able to understand – and perhaps even predict – future superplume activity could therefore “provide critical insights into the long-term survival of humanity”, he tells Physics World. “Such deep mantle processes may have profound implications for global environmental stability,” he says. “By advancing this research, we aim to uncover the mechanisms driving these extraordinary mantle events and assess their potential impact on Earth’s future.”
Congress approved a budget reconciliation bill that includes nearly $10 billion for NASA human spaceflight programs and could also lead to the transfer of a space shuttle to Houston.
In this week’s episode of Space Minds we bring you a special panel discussion on the future of commercial lunar exploration which was recorded live during the build-up to a historic moon landing.
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According to a recent white paper from the UK’s National Association of Disabled Staff Networks, 22% of working-age people in the UK have a disability compared to less than 7% of people working in science. At the upper echelons of science, only 4% of senior academic positions are filled with people with disabilities and just 1% of research grant applications to UK Research and Innovation are from researchers who disclose being disabled.
Based at Lancaster University, Doddato tells Physics World’s Michael Banks about the challenges facing scientists with disabilities – and calls for decision makers to engage with the issues and to remove barriers.
Quantum computers promise to revolutionize technology, but first they must overcome decoherence: the loss of quantum information caused by environmental noise. Topological quantum computers aim to do this by storing information in protected states called Majorana modes, but identifying materials that can support these modes has proved tricky and sometimes controversial.
Researchers in the US and Ireland have now developed a method that could make it easier. Using a modified form of scanning tunnelling microscopy (STM) with a superconducting tip, they built a tool that maps subtle features of a material’s internal quantum state – an achievement that could reveal which materials contain the elusive Majorana modes.
Going on a Majorana hunt
Unlike regular particles, a Majorana particle is its own antiparticle. It is also, strictly speaking, hypothetical – at least in its fundamental form. “So far, no one has definitively found this particle,” says Séamus Davis of University College Cork, who co-led the research with Dung-Hai Lee of the University of California, Berkeley. However, Davis adds, “all serious theorists believe that it should exist in our universe”.
Majorana modes are a slightly different beast. Rather than being fundamental particles, they are quasiparticle excitations that exhibit Majorana-like properties, and theory predicts that they should exist on the edges or surfaces of certain superconducting materials. But not every superconductor can host these states. The material must be topological, meaning its electrons are arranged in a special, symmetry-protected way. And unlike in most conventional superconductors, where electrons pair up with their spins pointing in opposite directions, the paired electrons in these materials have their spins aligned.
To distinguish these characteristics experimentally, Davis, Lee and colleagues invented what Davis calls “a new type of quantum microscope”. This special version of STM uses a superconducting tip to probe the surface of another superconductor. When the tip and sample interact, they produce telltale signals of so-called Andreev bound states (ABSs), which are localized quantum states that arise at boundaries, impurities or interfaces within a material.
The new microscope does more than just detect these states, however. It also lets users tweak the coupling strength between tip and sample to see how the energy of the ABS changes. This is critical, as it helps researchers determine whether the superconductor is chiral, meaning that the movement of its electron pairs has a preferred direction that doesn’t change when time runs backward. This breaking of time-reversal symmetry is characteristic of Majorana surface states. Hence, if a certain material shows both ABSs and chirality, scientists know it’s the material they’re looking for: a so-called topological superconductor.
Gonna catch a big one?
To demonstrate the method, the team applied it to uranium ditelluride (UTe₂), a superconductor with the desired electron pairing that was previously considered a strong candidate for topological superconductivity. Alas, measurements with the new microscope showed that UTe₂ doesn’t fit the bill.
“If UTe2 superconductivity did break time reversal and sustain a chiral state, then we would have imaged Majoranas and proven it is a topological superconductor,” says Davis. “But UTe2 does not break that symmetry.”
Despite this disappointment, Steven Kivelson, a theoretical physicist at Stanford University in the US who was not involved in the research, says that studying UTe₂’s superconducting state could still be useful. “Searching for topological superconductors is interesting in its own right,” he says.
While some physicists are sceptical that topological superconductors will deliver on their quantum computing potential, citing years of ambiguous data and unfulfilled claims, that scepticism doesn’t necessarily translate to disinterest. Even if such materials never lead to a working quantum computer, Kivelson believes understanding them is still essential. “One doesn’t need these sexy buzzwords to justify the importance of this work,” he says.
According to Davis, the value of the team’s work lies in the tool it introduces. The Andreev STM method, especially when combined with tip tuning and quasiparticle interference imaging, allows researchers to identify topological superconductors definitively. The technique also offers something more commonly-used bulk techniques cannot achieve: a real-space, high-resolution view of the superconductor’s pairing symmetry, including node imaging and phase variation across the material’s surface.
The team is now using its method to survey other candidate materials, including UPt₃, which Davis describes as “the most likely one” to show the right properties. “If we find one which has Majoranas on the surface, that will open the door to applications,” he says.
The “strategic objective”, Davis adds, would be to get away from trying to create Majorana modes in engineered systems such as nanowires layered with superconductors, as companies such as Microsoft and Nokia are doing. Finding an intrinsic topological superconductor would, he suggests, be simpler.
When Werner Heisenberg travelled to Helgoland in June 1925, he surely couldn’t have imagined that more than 300 researchers would make the same journey exactly a century later. But his development of the principles of quantum mechanics on the tiny North Sea island proved so significant that the crème de la crème of quantum physics, including four Nobel laureates, attended a five-day conference on Helgoland in June to mark the centenary of his breakthrough.
Just as Heisenberg had done, delegates travelled to the German archipelago by boat, leading one person to joke that if the ferry from Hamburg were to sink, “that’s basically quantum theory scuppered for a generation”. Fortunately, the vessel survived the four-hour trip up the river Elbe and 50 km out to sea – despite strong winds almost leading to a last-minute cancellation. The physicists returned in one piece too, meaning the future of quantum physics is safe.
These days Helgoland is a thriving tourist destination, offering beaches, bird-watching and boating, along with cafes, restaurants and shops selling luxury goods (the island benefits from being duty-free). But even 100 years ago it was a popular resort, especially for hay-fever sufferers like Heisenberg, who took a leave of absence from his post-doc under Max Born in Göttingen to seek refuge from a particularly bad bout of the illness on the windy and largely pollen-free island.
Where it all began Quantum physicists gather at the top of Helgoland’s main island to view a plaque installed in 2000 by the Max Planck Society near the spot where Werner Heisenberg said he formulated the principles of quantum mechanics in June 1925. (Courtesy: Matin Durrani)
More than five years in the making, Helgoland 2025 was organized by Florian Marquardt and colleagues at the Max Planck Institute for the Science of Light and Yale University quantum physicist Jack Harris, who said he was “very happy” with how the meeting turned out. As well as the quartet of Nobel laureates – Alain Aspect, Serge Haroche, David Wineland and Anton Zeilinger – there were many eager and enthusiastic early-career physicists who will be the future stars of quantum physics.
Questioning the foundations
When quantum physics began 100 years ago, only a handful of people were involved in the field. As well as Heisenberg and Born, there were the likes of Erwin Schrödinger, Paul Dirac, Wolfgang Pauli, Niels Bohr and Pascual Jordan. If WhatsApp had existed back then, the protagonists would have fitted into their own small group chat (perhaps called “The Quantum Apprentices”). But these days quantum physics is a far bigger endeavour.
Helgoland 2025 covered everything from the fundamentals of quantum mechanics to applied topics such as sensors and quantum computing.
With 31 lectures, five panel debates and more than 100 posters, Helgoland 2025 had sessions covering everything from the fundamentals of quantum mechanics and quantum information to applied topics such as sensors and quantum computing. In fact, Harris said in an after-dinner speech on the conference’s opening night in Hamburg that he and the organizing team could easily have “filled two or three solid programmes with people from whom we would have loved to hear”.
Harris’s big idea was to bring together theorists working on the foundational aspects of quantum mechanics with researchers applying those principles to quantum computing, sensing and communications. “[I hoped they] would enjoy talking to each other on an equal footing,” he told me after the meeting. “These topics have a lot of overlap, but that overlap isn’t always well-represented at conferences devoted to one or the other.”
In terms of foundational questions, speakers covered issues such as entanglement, superposition, non-locality, the meaning of measurement and the nature of information, particles, quantum states and randomness. Nicholas Gisin from the University of Geneva said physics is, at heart, all about extracting information from nature. Renato Renner from ETH Zurich discussed how to treat observers in quantum physics. Zeilinger argued that quantum states are states of knowledge – but, if so, do they exist only when measured?
Italian theorist and author Carlo Rovelli, who was constantly surrounded in the coffee breaks, gave a lecture on loop quantum gravity as a solution to marrying quantum physics with general relativity. In a talk on quantizing space–time, Juan Maldacena from the Institute for Advanced Study in Princeton discussed information loss and black holes, saying that a “white” black hole the size of a bacterium would be as hot as the Sun and emit so much light we could see it with the naked eye.
Quantum pioneers Helgoland 2025 featured talks, posters and discussions in the island’s Nordseehalle, where the four Nobel laureates in attendance signed a book marking the occasion (from left to right – Anton Zeilinger, Alain Aspect, Serge Haroche and David Wineland). (Courtesy: Matin Durrani)
Markus Aspelmeyer from the University of Vienna spoke about creating non-classical (i.e. quantum) sources of gravity in table-top experiments and tackled the prospect of gravitationally induced entanglement. Jun Ye from the University of Colorado, Boulder, talked about improving atomic clocks for fundamental physics. Bill Unruh from the University of British Columbia discussed the nature of particles, concluding that: “A particle is what a particle detector detects”.
It almost came as a relief when Gemma de les Coves from the Universitat Pompeu Fabra in Barcelona flashed up a slide joking : “I do not understand quantum mechanics.”
Applying quantum ideas
Discussing foundational topics might seem self-indulgent given the burgeoning (and financially lucrative) applications of quantum physics. But those basic questions are not only intriguing in their own right – they also help to attract newcomers into quantum physics. What’s more, practical matters like quantum computing, code breaking and signal detection are not just technical and engineering endeavours. “They hinge on our ability to understand those foundational questions,” says Harris.
In fact, plenty of practical applications were discussed at Helgoland. As Michelle Simmons from the University of New South Wales pointed out, the last 25 years have been a “golden age” for experimental quantum physics. “We now have the tools that allow us to manipulate the world at the very smallest length scales,” she said on the Physics World Weekly podcast. “We’re able for the first time to try and control quantum states and see if we can use them for different types of information encoding or for sensing.”
One presenter discussing applications was Jian-Wei Pan from the University of Science and Technology of China, who spoke about quantum computing and quantum communication across space, which relies on sustaining quantum entanglement over long distances and times. David Moore from Yale discussed some amazing practical experiments his group is doing using levitated, trapped silica microspheres as quantum sensors to detect what he called the “invisible” universe – neutrinos and perhaps even dark matter.
Nergis Mavalvala from the Massachusetts Institute of Technology, meanwhile, reminded us that gravitational-wave detectors, such as LIGO, rely on quantum physics to tackle the problem of “shot noise”, which otherwise limits their performance. Nathalie de Leon from Princeton University, who admitted on the final day she was going a bit “stir crazy” on the island, discussed quantum sensing with diamond.
Outside influences
Helgoland 2025 proved that quantum physicists have much to shout about, but also highlighted the many challenges still lying in store. How can we move from systems with just a few quantum bits to hundreds or thousands? How can quantum error correction help make noisy quantum systems reliable? What will we do with an exponential speed-up in computing? Is there a clear border between quantum and classical physics – and, if so, where is it?
By cooping participants together on an island with such strong historical associations, Harris hopes that Helgoland 2025 will have catalyzed new thinking. “I got to meet a lot of people I had always wanted to meet and re-connect with folks I’d been out of touch with for a long time,” he said. “I had wonderful conversations that I don’t think would have happened anywhere else. It is these kinds of person-to-person connections that often make the biggest impact.”
Natural beauty Helgoland’s main island is a popular tourist spot, with attractions including beaches and the 47m sea stack known as Lange Anna. (Courtesy: Matin Durrani)
Occasionally, though, the outside world did encroach on the meeting. To a round of applause, Rovelli said that physicists must keep working with Russian scientists, and warned of the dangers of demonizing others. Pan, who had to give his talk on a pre-recorded video, said it was “with much regret” that he was prevented from travelling to Helgoland from China. There were a few rumbles about the conference being sponsored in part by the US Air Force Office of Scientific Research and the Army Research Office.
Quantum physicists would also do well to find out more about the philosophy of science. Questions like the role of the observer, the nature of measurement, and the meaning of non-locality are central to quantum physics but are philosophical as much as scientific. Even knowing the philosophy relevant to the early years of quantum physics is important. As Elise Crull from the City University of New York said: “Physicists ignore this early philosophy at their peril”.
Towards the next century
The conference ended with a debate, chaired by Tracy Northup from the University of Innsbruck, on the next 100 years of quantum physics, where panellists agreed that the field’s ongoing mysteries are what will sustain it. “When we teach quantum mechanics, we should not be hiding the open problems, which are what interest students,” said Lorenzo Maccone from the University of Pavia in Italy. “They enjoy hearing there’s no consensus on, say the Wigner’s friend paradox. They seem engaged [and it shows] physics is not something dead.”
The importance of global links in science was underlined too. “Big advances usually come from international collaboration or friendly competition,” said panellist Gerd Leuchs from the Max Planck Institute for the Science of Light. “We should do everything we can to keep up collaboration. Scientists aren’t better people but they share a common language. Maintaining links across borders dampens violence.”
Leuchs also reminded the audience of the importance of scientists admitting they aren’t always right. “Scientists are often viewed as being arrogant, but we love to be proved wrong and we should teach people to enjoy being wrong,” he said. “If you want to be successful as a scientist, you have to be willing to change your mind. This is something that can be useful in the rest of society.”
I’ll leave the final word to Max Lock – a postdoc from the University of Vienna – who is part of a new generation of quantum physicists who have grown up with the weird but entirely self-consistent world of quantum physics. Reflecting on what happened at Helgoland, Lock said he was struck most by the contrast between what was being celebrated and the celebration itself.
“Heisenberg was an audacious 23-year-old whose insight spurred on a community of young and revolutionary thinkers,” he remarked. “With the utmost respect for the many years of experience and achievements that we saw on the stage, I’m quite sure that if there’s another revolution around the corner, it’ll come from the young members of the audience who are ready to turn the world upside down again.”
Tracy Northup and Michelle Simmons appear alongside fellow quantum physicist Peter Zoller on the 19 June 2025 edition of the Physics World Weekly podcast
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As the number of cancer cases continues to grow, radiation oncology departments are under increasing pressure to treat more and more patients. And as clinical facilities expand to manage this ongoing growth, and technology developments increase the complexity of radiotherapy delivery, there’s an urgent need to optimize the treatment workflow without ramping up time or staffing requirements.
To enable this level of optimization, radiation therapy departments will require an efficient quality management system that can handle both machine and patient quality assurance (QA), works seamlessly with treatment devices from multiple vendors, and provides the time savings required to ease staff workload.
Driven by growth
A case in point is the Moffitt Cancer Center in Florida, which in 2018 shifted all of its QA to SunCHECK, a quality management platform from Sun Nuclear that combines hardware and software to streamline treatment and delivery system QA into one centralized platform. Speaking at a recent Sun Nuclear webinar, clinical physicist Daniel Opp explained that the primary driver for this switch was growth.
Daniel Opp “Having one system means that we’re able to do tests in the same way across all our linacs.” (Courtesy: D Opp)
“In 2018, our physicians were shifting to perform a lot more SBRT [stereotactic body radiation therapy]. Our leadership had plans in motion to add online adaptive planning as well as expand with opening more radiation oncology centres,” he explained.
At that time, the centre was using multiple software platforms and many different imaging phantoms to run its QA, with physicists still relying on manual measurements and qualitative visual assessments. Now, the team performs all machine QA using SunCHECK Machine and almost all patient-specific QA [PSQA] using SunCHECK Patient.
“Our QA software and data were fractured and all over the place,” said Opp. “The move to SunCHECK made sense as it gave us the ability to integrate all measurements, software and databases into a one-stop shop, providing significant time savings and far cleaner record keeping.”
SunCHECK also simplifies QA procedures by consolidating tests. Opp explained that back in 2018, photon tests on the centre’s linacs required five setups, 12 measurements and manually entering values 22 times; SunCHECK reduced this to one setup, four measurements and no manual entries. “This alone gives you an overview of the significant time savings,” he said.
Another benefit is the ability to automate tests and ensure standardization. “If you tell our large group of physicists to do a picket fence test, we’ll all do it a little differently,” Opp explained. “Having one system on which we’re all running the same tests means that we’re able to do the test in the same way across all our linacs.”
Opp noted that SunCHECK displays all required information on an easy-to-read screen, with the patient QA worklist on one side and the machine QA worklist on the other. “You see a snapshot of the clinic and can figure out if there’s anything you need to take care of. It’s very efficient in letting you know when something needs your attention,” he said.
Sansourekidou initiated the switch to SunCHECK after joining UNM in 2020 as its new director of medical physics. At that time the cancer centre was treating about 1000 patients per year. But high patient numbers led to a long waiting list – with roughly three months between referral and the start of treatment – and clear need for the facility to expand.
Patricia Sansourekidou “We saw huge time savings for both monthly and daily QA.” (Courtesy: P Sansourekidou)
Assessing the centre’s QA procedures in 2020 revealed that the team was using a wide variety of QA software, making routine checks time consuming. Monthly linac QA, for example, required roughly 32 files and took about 14 hours to perform. In addition, Sansourekidou noted, physicists were spending hours every month adjusting the machines. “One day it was the energy that was off and then the output was off; I soon realised that, in the absence of appropriate software, we were making adjustments back and forth,” she said. “More importantly, we had no way to track these trends.”
Sansourekidou concluded that the centre needed an improved QA solution based on one unified platform. “So we went on a physics hunt,” she said. “We met with every vendor out there and Sun Nuclear won the request for proposal. So we implemented SunCHECK Machine and SunCHECK Patient.”
Switching to SunCHECK reduced monthly QA to just 4–5 hours per linac. “We’re saving about nine hours per linac per month; that’s 324 hours per year when we could be doing something else for our patients,” said Sansourekidou. Importantly, the new software enables the team to visualize trends and assess whether a genuine problem is present.
For daily QA, which previously required numerous spreadsheets and systems, SunCHECK’s daily QA template provides time savings of about 60%. “At six in the morning, that’s important,” Sansourekidou pointed out. Annual QA saw roughly 33% time savings, while for the 70% of patients requiring PSQA, time savings were about 25%.
Another “unexpected side effect” of deploying SunCHECK, said Sansourekidou, is that the IT department was happy to maintain one platform. “Every time we have a new physicist, it’s much easier for our IT department to set them up. That has been a huge benefit for us,” she said. “Additionally, our service engineers are happy because we are not spending hours of their time adjusting the machine back and forth.”
“Overall, I thought there were great improvements that really helped us justify the initial investment – not just monetary, but also time investment from our physics team,” she said.
Efficiency savings QA times before and after implementing SunCHECK at the UNM Comprehensive Cancer Center. (Courtesy: Patricia Sansourekidou)
Phantom-free QA
For Opp, one of the biggest features enabled by SunCHECK was the move to phantom-free PSQA, which saves a lot of time and eliminates errors that can be inherent to phantom-based QA. In the last year, the Moffitt team also switched to using DoseCHECK – SunCHECK’s secondary 3D dose calculation algorithm – as the foundation of its quality checks. Alongside, a RayStation script checks plan deliverability to ensure that no problems arise once the patient is on the table.
“We don’t do our pre-treatment QA anymore. We rely on those two to get confidence into the final work and then we run our logs off the first patient fraction,” Opp explained. “We have a large physics group and there was natural apprehension, but everybody got on board and agreed that this was a shift we needed to make. We leveraged DoseCHECK to create a better QA system for ourselves.”
Since 2018, both patient workload and staff numbers at the Moffitt Cancer Center have doubled. By the end of 2025, it will also have almost doubled its number of treatment units. The centre has over 100 SunCHECK users – including therapists, dosimetrists and physicists – and Opp emphasized that the system is robust enough to handle all these users doing different tasks at different times without any issues.
As patient numbers increase, the time savings conferred by SunCHECK help reduce staff workload and improve quality-of-life for users. The centre currently performs about 100 PSQA procedures per week, which would have taken about 37 hours using previous QA processes – a workload that Opp notes would not be managed well. SunCHECK reduced the weekly average to around seven hours.
Similarly, linac QA previously required two or three late nights per month (or one full day on the weekend). “After the switch to SunCHECK, everybody’s pretty much able to get it done in one late night per month,” said Opp. He added that the Moffitt Cancer Center’s continuing growth has required the onboarding of many new physicists – and that it’s significantly easier to train these new staff with all of the QA software in one centralized platform.
Enabling accreditation
Finally, accreditation is essential for radiation oncology departments to demonstrate the ability to deliver safe, high-quality care. The UNM Comprehensive Cancer Centre’s previous American College of Radiology (ACR) accreditation had expired before Sansourekidou’s arrival, and she was keen to rectify this situation. And in March 2024 the centre achieved ASTRO’s APEx accreditation.
“SunCHECK helped with that,” she said. “It wasn’t the only reason, there were other things that we had to improve, but we did come across as having a strong physics programme.”
Achieving accreditation also helps justify the purchase of a totally new QA platform, Sansourekidou explained. “The most important thing to explain to your administration is that if we don’t do things the way that our regulatory bodies advise, then not only will we lose our accreditation, but we will fall behind,” she said.
Sansourekidou emphasized that the efficiency gains conferred by SunCHECK were invaluable for the physics team, particularly for out-of-hours working. “We saw huge time savings for both monthly and daily QA,” she said. “It is a large investment, but improving efficiency through investment in software will really help the department in the long term.”
Hundreds of physicists gathered on the island of Helgoland in June to celebrate the centennial anniversary of the invention of quantum mechanics by the physicist Werner Heisenberg. The event – Helgoland 2025 – is a centrepiece of the International Year of Quantum Science and Technology and it drew 300 quantum physicists with plenary talks and panel discussions ranging from philosophical puzzles like Wigner’s friend to state-of-the-art experiments in quantum computing.
In 1925 Heisenberg travelled to the island, off the coast of Germany, to recover from hay fever. While there he put together a mathematical framework for quantum mechanics that gave up the “visualizability” of quantum phenomena and strictly focused on “observables”. Heisenberg’s mythical stay on Helgoland is traditionally celebrated as the birth of quantum mechanics.
I attended the event as a philosopher of science with a background in quantum mechanics, and I was keen to learn more about participants’ views about the relationship between philosophy and physics. Quantum information theory lives at the intersection of philosophy and physics, as the field has been one of the primary drivers of renewed progress in the philosophy of quantum mechanics and its interpretations.
Renowned for being the financial powerhouse of quantum computing, quantum-information theory is flush with funding for building computers promising “quantum advantage”. Isaac Chuang from Massachusetts Institute of Technology bluntly told the audience that these computers currently do not serve any important economic function. The theory behind the boom in quantum computing has been equally important for philosophers and physicists looking for a compelling list of axioms from quantum mechanics, akin to Einstein’s postulates for relativity.
Like most scientific pursuits, quantum information did not begin with practical ends in mind, but with honest questions about nature. In the 1990s it was closer to foundational issues about the meaning of quantum mechanics. The growth of this philosophical-physical discipline called “quantum foundations”, while not a moneymaker, has made the field more introspective about concepts in desperate need of elucidation. Terms such as measurement, superposition, nonlocality and the metaphysics of quantum states are hotly debated in the community.
As has happened multiple times, Nobel laureates Alain Aspect and Anton Zeilinger sparred at Helgoland over the ontology of quantum states. Zeilinger defended the viewpoint that quantum states are states of knowledge, while Aspect defended nonlocality on pragmatic grounds. When Markus Aspelmeyer from the University of Vienna finished his talk on looking for gravitationally induced entanglement, he was asked what this phenomenon could mean if quantum states are only knowledge.
None of the talks attempted to fix a consensus about foundational questions. As the British philosopher Ludwig Wittgenstein wrote in his 1969 book On Certainty, “At the foundation of well-founded belief lies belief that is not founded.” Talks by Christopher Fuchs from the University of Massachusetts Boston and Robert Spekkens from the Perimeter Institute for Theoretical Physics in Canada underscored that we must be willing to dissect the theory to find what makes quantum mechanics truly quantum, and this will reveal what is special about nature. This patience for not jumping the gun on quantum ontology has paid off.
Spekkens showed that many phenomena taken to be uniquely quantum – the uncertainty relations, interference and wave–particle duality – are not the root of the mystery and can be accounted for classically. He referred to remaining phenomena as the “thin film” of quantum mechanics, such as Bell inequality violations, that cannot be accounted for in any classical theory. The pedagogical strategy of making quantum theory look as classical as possible was picked up in a panel discussion on the last day. The panellists suggested that physics educators not sensationalize the theory and use the most intuitive, “classical” reasoning available.
While at Helgoland, I had a discussion with philosopher Elise Crull from City College of New York and IBM quantum physicist Charles Bennett about the philosophy of science. Crull said how physics and philosophy can support each other, as physics was once a branch of natural philosophy. In fact, in her classes, Crull says she shows students how philosophically engaged the pioneers of quantum mechanics were – for example, how Bohr and Einstein were broadly familiar with Kantian philosophy.
Bennett, meanwhile, told the story of how he built up the field of quantum information theory by calculating the amount of energy necessary for computing with a quantum bit. He emphasized that one of a scientist’s great virtues is the joy of being wrong. We do not have to back down from the truth and we can also believe it is important to humanize others. If we can admit that we’re wrong, then non-scientists can too.
Renewed hope
Moral concerns surrounding the culture of science surfaced throughout the conference. It was lost on no-one, for instance, that the vast majority of participants at the conference were men. Crull made this explicit during the opening banquet, when she flashed a slide that slowly populated with the overlooked or outright forgotten voices of women in the invention of quantum mechanics. The slide was completely full by the end. The organization Diversity in Quantum noted that it is examining workplace diversity in quantum sciences and quantum technologies.
Through the celebration, the gravity of our current political environment crept into the otherwise momentous gathering. The invention of quantum mechanics converged with arguably the darkest moment in human history. Among its many moral atrocities, the political ascent of Nazism fractured the intellectual centres of Europe and severely damaged the reputation of German science. The conference saw numerous participants cite the importance of international collaboration and inclusivity in their talks. During the closing remarks of the conference, Časlav Brukner, who is scientific director of the Institute for Quantum Optics and Quantum Information in Vienna, told the crowd, “Love is wise. Hatred is foolish.”
Natural philosophy Back in 1925, the island of Helgoland provided Werner Heisenberg a peaceful location to walk and think. A century later, it hosted hundreds of physicists discussing and contemplating quantum mechanics. (Courtesy: Matin Durrani)
I felt refreshed by the air of solidarity among participants after months of Donald Trump’s cartoonish vitriol towards education and academic freedom. However, I worry that scientists are still too confident that the acceptance of scientific truth is inevitable, as if the status quo will be easily restored in a few years. I have taught physics classes in rural areas where a distrust in scientific institutions resonated with my students, who openly doubted not only the science of evolution and climate change, but also the seemingly exotic features of relativity, or whether human beings landed on the Moon.
I often found that explaining the facts does not change students’ minds because the entire enterprise of science, the meaningfulness of scientific inquiry, often strikes non-scientists as alien and disconnected from the context in which they live. As suggested by Wittgenstein, many of our core beliefs go unexamined and end up in a blind spot. It is difficult to know what our common ground really is, but without it, facts are not salient to us.
They do not look like “facts” at all without a significant amount of education and preparation, not just in terms of technical background but also the culture of scientific inquiry. We require training and acculturation to know how a piece of information is supposed to count as “evidence” for a conclusion. Nothing inevitable follows from the possession or dissemination of facts. It takes a community of peers, not just experts, to recontextualize the facts in terms of our common ground.
I left the conference with renewed hope that quantum physics is thriving but also concerned that scientists are in for a long fight to depoliticize factual information. It is essential that this fight humanizes those who disagree with us as much as it draws a line in the sand against the spreading of falsehoods. Science is not really the default setting for how humans think about the world. As many historians of science point out, a belief in the possibility of science at all, over all its competitors in the history of the world, is quite extraordinary.
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.
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.
Schematic of experiment (Courtesy: Jacopo Baglioni/University of Padova)
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.
Connexion
