A research team headed up at Linköping University in Sweden and Cornell University in the US has succeeded in recycling almost all of the components of perovskite solar cells using simple, non-toxic, water-based solvents. What’s more, the researchers were able to use the recycled components to make new perovskite solar cells with almost the same power conversion efficiency as those created from new materials. This work could pave the way to a sustainable perovskite solar economy, they say.
While solar energy is considered an environmentally friendly source of energy, most of the solar panels available today are based on silicon, which is difficult to recycle. This has led to the first generation of silicon solar panels, which are reaching the end of their life cycles, ending up in landfills, says Xun Xiao, one of the team members at Linköping University.
When developing emerging solar cell technologies, we therefore need to take recycling into consideration, adds one of the leaders of the new study, Feng Gao, also at Linköping. “If we don’t know how to recycle them, maybe we shouldn’t put them on the market at all.”
To this end, many countries around the world are imposing legal requirements on photovoltaic manufacturers, to ensure that they collect and recycle any solar cell waste they produce. These initiatives include the WEEE directive 2012/19/EU in the European Union and equivalent legislation in Asia and the US.
Perovskites are one of the most promising materials for making next-generation solar cells. Not only are they relatively inexpensive, they are also easy to fabricate, lightweight, flexible and transparent. This allows them to be placed on top of a variety of surfaces, unlike their silicon counterparts. And since they boast a power conversion efficiency (PCE) of more than 25%, this makes them comparable to existing photovoltaics on the market.
A shorter lifespan
One of their downsides, however, is that perovskite solar cells have a shorter lifespan than silicon solar cells. This means that recycling is even more critical for these materials. Today, perovskite solar cells are disassembled using dangerous solvents such as dimethylformamide, but Gao and colleagues have now developed a technique in which water can be used as the solvent.
Perovskites are crystalline materials with an ABX3 structure, where A is caesium, methylammonium (MA) or formamidinium (FA); B is lead or tin; and X is chlorine, bromine or iodine. Solar cells made of these materials are composed of different layers: the hole/electron transport layers; the perovskite layer; indium tin oxide substrates; and cover glasses.
In their work, which they detail in Nature, the researchers succeeded in delaminating end-of-life devices layer by layer, using water containing three low-cost additives: sodium acetate, sodium iodide and hypophosphorous acid. Despite being able to dissolve organic iodide salts such as methylammonium iodide and formamidinium iodide, water only marginally dissolves lead iodide (about 0.044 g per 100 ml at 20 °C). The researchers therefore developed a way to increase the amount of lead iodide that dissolves in water by introducing acetate ions into the mix. These ions readily coordinate with lead ions, forming highly soluble lead acetate (about 44.31 g per 100 ml at 20 °C).
Once the degraded perovskites had dissolved in the aqueous solution, the researchers set about recovering pure and high-quality perovskite crystals from the solution. They did this by providing extra iodide ions to coordinate with lead. This resulted in [PbI]+ transitioning to [PbI2]0 and eventually to [PbI3]− and the formation of the perovskite framework.
To remove the indium tin oxide substrates, the researchers sonicated these layers in a solution of water/ethanol (50%/50% volume ratio) for 15 min. Finally, they delaminated the cover glasses by placing the degraded solar cells on a hotplate preheated to 150 °C for 3 min.
They were able to apply their technology to recycle both MAPbI3 and FAPbI3 perovskites.
New devices made from the recycled perovskites had an average power conversion efficiency of 21.9 ± 1.1%, with the best samples clocking in at 23.4%. This represents an efficiency recovery of more than 99% compared with those prepared using fresh materials (which have a PCE of 22.1 ± 0.9%).
Looking forward, Gao and colleagues say they would now like to demonstrate that their technique works on a larger scale. “Our life-cycle assessment and techno-economic analysis has already confirmed that our strategy not only preserves raw materials, but also appreciably lowers overall manufacturing costs of solar cells made from perovskites,” says co-team leader Fengqi You, who works at Cornell University. “In particular, reclaiming the valuable layers in these devices drives down expenses and helps reduce the ‘levelized cost’ of electricity they produce, making the technology potentially more competitive and sustainable at scale,” he tells Physics World.
Quantum technologies are flourishing the world over, with advances across the board researching practical applications such as quantum computing, communication, cryptography and sensors. Indeed, the quantum industry is booming – an estimated $42bn was invested in the sector in 2023, and this amount is projected to rise to $106bn by 2040.
With academia, industry and government all looking for professionals to join the future quantum workforce, it’s crucial to have people with the right skills, and from all educational levels. With this in mind, efforts are being made across the US to focus on quantum education and training, with educators working to introduce quantum concepts from the elementary-school level, all the way to tailored programmes at PhD and postgraduate level that meet the needs of potential employers in the area. Efforts are being made to ensure that graduates and early-career physicists are aware of the many roles available in the quantum sphere.
“There are a lot of layers to what has to be done in quantum education,” says Emily Edwards, an electrical and computer engineer at Duke University and co-leader of the National Q-12 Education Partnership. “I like to think of quantum education along different dimensions. One way is to think about what most learners may need in terms of foundational public literacy or student literacy in the space. Towards the top, we have people who are very specialized. Essentially, we have to think about many different learners at different stages – they might need specific tools or might need different barriers removed for them. And so different parts of the economy – from government to industry to academia and professional institutions – will play a role in how to address the needs of a certain group.”
Engaging young minds
To ensure that the US remains a key global player in quantum information science and technology (QIST), the National Q-12 Education Partnership – launched by the White House Office of Science and Technology Policy and the National Science Foundation (NSF) – is focused on ways to engage young minds in quantum, building the necessary tools and strategies to help improve early (K-12) education and outreach.
To achieve this, Q-12 is looking at outreach and education in middle and high school by introducing QIST concepts and providing access to learning materials and to inspire the next generation of quantum leaders. Over the next decade, Q-12 also aims to provide quantum-related curricula – developed by professionals in the field – beyond university labs and classrooms, to community colleges and online courses.
Edwards explains that while Q-12 mainly focuses on the K-12 level, there is also an overlap with early undergraduate, two-year colleges – meaning that there is a wide range of requirements, issues and unique challenges to contend with. Such a big space also means that different companies and institutions have varying levels of funding and interests in quantum education research and development.
“Academic organizations, for example, tend to work on educational research or to provide professional development, especially because it’s nascent,” says Edwards. “There is a lot of the activity in the academic space, within professional societies. We also work with a number of private companies, some of which are developing curricula, or providing free access to different tools and simulations for learning experiences.”
The role of the APS
The American Physical Society (APS) is strongly involved in quantum education – by making sure that teachers have access to tools and resources for quantum education as well as connecting quantum professionals with K-12 classrooms to discuss careers in quantum. “The APS has been really active in engaging with teachers and connecting them with the vast network of APS members, stakeholders and professionals, to talk about careers,” says Edwards. APS and Q-12 have a number of initiatives – such as Quantum To-Go and QuanTime – that help connect quantum professionals with classrooms and provide teachers with ready-to-use quantum activities.
Role model The Quantum To-Go programme matches scientists, engineers and professionals in quantum information science andt technology with classrooms across the US to inspire students to enter the quantum workforce. (Courtesy: APS)
Claudia Fracchiolla, who is the APS’s head of public engagement, points out that while there is growing interest in quantum education, there is a lack of explicit support for high-school teachers who need to be having conversations about a possible career in quantum with students that will soon be choosing a major.
“We know from our research that while teachers might want to engage in this professional development, they don’t always have the necessary support from their institution and it is not regulated,” explains Fracchiolla. She adds that while there are a “few stellar people in the field who are creating materials for teachers”, there is not a clear standard on how they can be used, or what can be taught at a school level.
Quantum To-Go
To help tackle these issues, the APS and Q-12 launched the Quantum To-Go programme, which pairs educators with quantum-science professionals, who speak to students about quantum concepts and careers. The programme covers students from the first year of school through to undergraduate level, with scientists visiting in person or virtually.
It’s a really great way for quantum professionals in different sectors to visit classrooms and talk about their experiences
Emily Edwards
“I think it’s a really great way for quantum professionals in different sectors to visit classrooms and talk about their experiences,” says Edwards. She adds that this kind of collaboration can be especially useful “because we know that students – particularly young women, or students of colour or those from any marginalized background – self-select out of these areas while they’re still in the K-12 environment.”
Edwards puts this down to a lack of role models in the workplace. “Not only do they not hear about quantum in the classroom or in their curriculum, but they also can’t see themselves working in the field,” she says. “So there’s no hope of achieving a diverse workforce if you don’t connect a diverse set of professionals with the classroom. So we are really proud to be a part of Quantum To-Go.”
Quantum resources
With 2025 being celebrated as the International Year of Quantum Science and Technology (IYQ), both Q-12 and the APS hope to see and host many community-driven activities and events focused on young learners and their families. An example of this is Q-12’s QuanTime initiative, which seeks to help teachers curate informal quantum activities across the US all year round. “Education is local in the US, and so it’s most successful if we can work with locals to help develop their own community resources,” explains Edwards.
A key event in the APS’s annual calendar of activities celebrating IYQ is the Quantum Education and Policy Summit, held in partnership with the Q-SEnSE institute. It aims to bring together key experts in physics education, policymakers and quantum industry leaders, to develop quantum educational resources and policies.
Quantum influencers Testifying before the US House Science Committee on 7 June 2023 were (from left to right) National Quantum Coordination Office director Charles Tahan, former Department of Education under secretary for science Paul Dabbar, NASA quantum scientist Eleanor Rieffel, Quantum Economic Development Consortium executive director Celia Merzbacher, and University of Illinois quantum scientist Emily Edwards (now at Duke University). (Courtesy: House Science Committee)
Another popular resource produced by the APS is its PhysicsQuest kits, which are aimed at middle-school students to help them explore specific physics topics. “We engaged with different APS members who work in quantum to design activities for middle-school students,”says Fracchiolla. “We then worked with some teachers to pilot and test those activities, before finalizing our kits, which are freely available to teachers. Normally, each year we do four activities, but thanks to IYQ, we decided to double that to eight activities that are all related to topics in quantum science and technology.”
To help distribute these kits to teachers, as well as provide them with guidance on how to use all the included materials, the APS is hosting workshops for teachers during the Teachers’ Days at the APS Global Physics Summit in March 2025. Workshops will also be held at the APS Division of Atomic, Molecular and Optical Physics (DAMOP) annual meeting in June.
“A key part of IYQ is creating an awareness of what quantum science and technology entails, because it is also about the people that work in the field,” says Fracchiolla. “Something that was really important when we were writing the proposal to send to the UN for the IYQ was to demonstrate how quantum technologies will supports the UN’s sustainable development goals. I hope this also inspires students to pursue careers in quantum, as they realize that it goes beyond quantum computing.”
If we are focusing on quantum technologies to address sustainable development goals, we need to make sure that they are accessible to everyone
Claudia Fracchiolla
Fracchiolla also underlines that having a diverse range of people in the quantum workforce will ensure that these technologies will help to tackle societal and environmental issues, and vice versa. “If we are focusing on quantum technologies to address sustainable development goals, we need to make sure that they are accessible to everyone. And that’s not going to happen if diverse minds are not involved in the process of developing these technologies,” she says, while acknowledging that this is currently not the case.
It is Fracchiolla’s ultimate hope that the IYQ and the APS’s activities taken together will help all students feel empowered that there is a place for them in the field. “Quantum is still a nascent field and we have the opportunity to not repeat the errors of the past, that have made many areas of science exclusive. We need to make the field diverse from the get go.”
The Stand Up for Science demonstration at Washington Square Park in New York City on Friday 7 March 2025 had the most qualified speakers, angriest participants and wickedest signs of any protest I can remember.
Raucous, diverse and loud, it was held in the shadow of looming massive cuts to key US scientific agencies including the National Institutes of Health (NIH), the National Science Foundation (NSF), and the National Oceanic and Atmospheric Administration (NOAA)
Other anti-science actions have included the appointment of a vaccine opponent as head of the US Health and Human Services and the cancellation of $400m in grants and contracts to Columbia University.
I arrived at the venue half an hour beforehand. Despite the chillingly cold and breezy weather, the park’s usual characters were there, including chess players, tap dancers, people advertising “Revolution Books” and evangelists who handed me a “spiritual credit card”.
But I had come for a more real-world cause that is affecting many of my research colleagues right here, right now. Among the Stand Up For Science demonstrators was Srishti Bose, a fourth-year graduate student in neuroscience at Queens College, who met me underneath the arch at the north of the park, the traditional site of demonstrations.
She had organized the rally together with two other women – a graduate student at Stony Brook University and a postdoc at the Albert Einstein College of Medicine. They had heard that there would be a Stand Up for Science rally on the same day in Washington, DC, and thought that New York City should have one too. In fact, there were 32 across the US in total.
The trio didn’t have much time, and none of them had ever planned a political protest before. “We spent 10 days frantically e-mailing everyone we could think of,” Srishti said, of having to arrange the permits, equipment, insurance, medical and security personnel – and speakers.
Speaking out Two of the protestors in Washington Square in Greenwich Village, New York. (Courtesy: Robert P Crease)
I was astounded at what they accomplished. The first speaker was Harald Varmus, who won the 1989 Nobel Prize for Physiology and Medicine and spent seven years as director of the NIH under President Barack Obama. “People think medicine falls from the sky,” he told protestors, “rather than from academics supported by science funding.”
Another Nobel-prize-winner who spoke was Martin Chalfie from Columbia University, who won the 2008 Nobel Prize for Chemistry.
Speaker after speaker – faculty, foundation directors, lab heads, faculty, postdocs, graduate students, New York State politicians – ticked off what was being lost by the budget cuts targeting science.
It included money for motor neurone disease, Alzheimer’s, cancer, polio, measles, heart disease research, climate science, and funding that supports stipends and salaries for postdocs, grad students, university labs and departments.
Lisa Randall, a theoretical physicist at Harvard University, began with a joke: “How many government officials does it take to screw in a light bulb? None: Trump says the job’s done and they stay in the dark.”
Randall continued by enumerating programme and funding cuts that will turn the lights out on important research. “Let’s keep the values that Make America Great – Again,” she concluded.
The crowd of 2000 or so demonstrators were diverse and multi-generational, as is typical for such events in my New York City. I heard at least five different languages being spoken. Everyone was fired up and roared “Boo!” whenever the names of certain politicians were mentioned.
I told Bose about the criticism I had heard that Stand Up for Science was making science look like a special-interest group rather than being carried out in the public interest.
She would have none of it. “They made us an interest group,” Bose insisted. “We grew up thinking that everyone accepted and supported science. This is the first time we’ve had a direct attack on what we do. I can’t think of a single lab that doesn’t have an NSF or NIH grant.”
Seriously funny Many of the demonstrators held messages aloft. (Courtesy: Robert P Crease)
Lots of signs were on display, many fabulously aggressive and angry, ranging from hand-drawn lettering on cardboard to carefully produced placards – some of which I won’t reproduce in a family magazine.
“I shouldn’t have to make a sign saying that ‘Defunding science is wrong’…but here we are” said one. “Go fact yourself!” and “Science keeps you assholes alive”, said others.
Two female breast-cancer researchers had made a sign that, they told me, put their message in a way that they thought the current US leaders would get: “Science saves boobs.”
I saw others that bitterly mocked the current US president’s apparent ignorance of the distinction between “transgenic” and “transgender”.
“Girls just wanna have funding” said another witty sign. “Executive orders are not peer reviewed”; “Science: because I’d rather not make shit up”; “Science is significant *p<0.05” said others.
The rally ended with 20 minutes of call-and-response chants. Everyone knew the words, thanks to a QR code.
“We will fight?”
“Every day!”
“When science is under attack?”
“Stand up, fight back!”
“What do we want?”
“Answers”
“When do we want it?”
“After peer review!”
After the spirited chanting, the rally was officially over, but many people stayed, sharing stories, collecting information and seeking ideas for the next moves.
“Obviously,” Bose said, “it’s not going to end here.”
A few months ago, I attended a presentation and reception at the Houses of Parliament in London for companies that had won Business Awards from the Institute of Physics in 2024. What excited me most at the event was hearing about the smaller start-up companies and their innovations. They are developing everything from metamaterials for sound proofing to instruments that can non-invasively measure pressure in the human brain.
The event also reminded me of my own experience working in the small-business sector. After completing my PhD in high-speed aerodynamics at the University of Southampton, I spent a short spell working for what was then the Defence and Evaluation Research Agency (DERA) in Farnborough. But wanting to stay in Southampton, I decided working permanently at DERA wasn’t right for me so started looking for a suitable role closer to home.
I soon found myself working as a development engineer at a small engineering company called Stewart Hughes Limited. It was founded in 1980 by Ron Stewart and Tony Hughes, who had been researchers at the Institute of Sound and Vibration Research (ISVR) at Southampton University. Through numerous research contracts, the pair had spent almost a decade developing techniques for monitoring the condition of mechanical machinery from their vibrations.
By attaching accelerometers or vibration sensors to the machines, they discovered that the resulting signals can be processed to determine the physical condition of the devices. Their particular innovation was to find a way to both capture and process the accelerometer signals in near real time to produce indicators relating to the health of the equipment being monitored. It required a combination of hardware and software that was cutting edge at the time.
Exciting times
Although I did not join the firm until early 1994, it still had all the feel of a start-up. We were located in a single office building (in reality it was a repurposed warehouse) with 50 or so staff, about 40 of whom were electronics, software and mechanical engineers. There was a strong emphasis on “systems engineering” – in other words, integrating different disciplines to design and build an overarching solution to a problem.
In its early years, Stewart Hughes had developed a variety of applications for their vibration health monitoring technique. It was used in all sorts of areas, ranging from conveyor belts carrying coal and Royal Navy ships travelling at sea to supersized trucks working on mines. But when I joined, the company was focused on helicopter drivetrains.
In particular, the company had developed a product called Health and Usage Monitoring System (HUMS). The UK’s Civil Aviation Authority required this kind of device to be fitted on all helicopters transporting passengers to and from oil platforms in the North Sea to improve operational safety. Our equipment (and that of rival suppliers – we did not have a monopoly) was used to monitor mechanical parts such as gears, bearings, shafts and rotors.
For someone straight out of university, it was an exciting time. There were lots of technical challenges to be solved, including designing effective ways to process signals in noisy environments and extracting information about critical drivetrain components. We then had to convert the data into indicators that could be monitored to detect and diagnose mechanical issues.
As a physicist, I found myself working closely with the engineers but tended to approach things from a more fundamental angle, helping to explain why certain approaches worked and others didn’t. Don’t forget that the technology developed by Stewart Hughes wasn’t used in the comfort of a physics lab but on a real-life working helicopter. That meant capturing and processing data on the airborne helicopter itself using bespoke electronics to manage high onboard data rates.
After the data were downloaded, they had to be sent on floppy disks or other portable storage devices to ground stations. There the results would be presented in a form to allow customers and our own staff to interpret and diagnose any mechanical problems. We also had to develop ways to monitor an entire fleet of helicopters, continuously learning and developing from experience.
If it all sounds as if working in a small business is plain sailing, well it rarely is. A few years before I joined, Stewart Hughes had ridden out at least one major storm when it was forced to significantly reduce the workforce because anticipated contracts did not materialize. “Black Friday”, as it became known, made the board of directors nervous about taking on additional employees, often relying on existing staff to work overtime instead.
This arrangement actually suited many of the early-career employees, who were keen to quickly expand their work experience and their pay packet. But when I arrived, we were once again up against cash-flow challenges, which is the bane of any small business. Back then there were no digital electronic documents and web portals, which led to some hairy situations.
I can recall several occasions when the company had to book a despatch rider for 2 p.m. on a Friday afternoon to dash a report up the motorway to the Ministry of Defence in London. If we hadn’t got an approval signature and contractual payment before the close of business on the same day, the company literally wouldn’t have been able to open its doors on Monday morning.
Being part of a small company was undoubtedly a formative part of my early career experience
At some stage, however, the company’s bank lost patience with this hand-to-mouth existence and the board of directors was told to put the firm on a more solid financial footing. This edict led to the company structure becoming more formal and the directors being less accessible, with a seasoned professional brought in to help run the business. The resulting change in strategic trajectory eventually led to its sale.
Being part of a small company was undoubtedly a formative part of my early career experience. It was an exciting time and the fact all employees were – literally – under one roof meant that we knew and worked with the decision makers. We always had the opportunity to speak up and influence the future. We got to work on unexpected new projects because there was external funding available. We could be flexible when it came to trying out new software or hardware as part of our product development.
The flip side was that we sometimes had to flex too much, which at times made it hard to stick to a cohesive strategy. We struggled to find cash to try out blue sky or speculative approaches – although there were plenty of good ideas. These advantages come with being part of a larger corporation with bigger budgets and greater overall stability.
That said, I appreciate the diverse and dynamic learning curve I experienced at Stewart Hughes. The founders were innovators, whose vision and products have stood the test of time, still being widely used today . The company benefited many people not just the staff who led successful careers but also the pilots and passengers on helicopters whose lives may potentially have been saved.
Working in a large corporation is undoubtedly a smoother ride than in a small business. But it’s rarely seat-of-the-pants stuff and I learned so much from my own days at Stewart Hughes. Attending the IOP’s business awards reminded me of the buzz of being in a small firm. It might not be to everyone’s taste, but if you get the chance to work in that environment, do give it serious thought.
Researchers from the Amazon Web Services (AWS) Center for Quantum Computing have announced what they describe as a “breakthrough” in quantum error correction. Their method uses so-called cat qubits to reduce the total number of qubits required to build a large-scale, fault-tolerant quantum computer, and they claim it could shorten the time required to develop such machines by up to five years.
Quantum computers are promising candidates for solving complex problems that today’s classical computers cannot handle. Their main drawback is the tendency for errors to crop up in the quantum bits, or qubits, they use to perform computations. Just like classical bits, the states of qubits can erroneously flip from 0 to 1, which is known as a bit-flip error. In addition, qubits can suffer from inadvertent changes to their phase, which is a parameter that characterizes their quantum superposition (phase-flip errors). A further complication is that whereas classical bits can be copied in order to detect and correct errors, the quantum nature of qubits makes copying impossible. Hence, errors need to be dealt with in other ways.
One error-correction scheme involves building physical or “measurement” qubits around each logical or “data” qubit. The job of the measurement qubits is to detect phase-flip or bit-flip errors in the data qubits without destroying their quantum nature. In 2024, a team at Google Quantum AI showed that this approach is scalable in a system of a few dozen qubits. However, a truly powerful quantum computer would require around a million data qubits and an even larger number of measurement qubits.
Cat qubits to the rescue
The AWS researchers showed that it is possible reduce this total number of qubits. They did this by using a special type of qubit called a cat qubit. Named after the Schrödinger’s cat thought that illustrates the concept of quantum superposition, cat qubits use the superposition of coherent states to encode information in a way that resists bit flips. Doing so may increase the number of phase-flip errors, but special error-correction algorithms can deal with these efficiently.
The AWS team got this result by building a microchip containing an array of five cat qubits. These are connected to four transmon qubits, which are a type of superconducting qubit with a reduced sensitivity to charge noise (a major source of errors in quantum computations). Here, the cat qubits serve as data qubits, while the transmon qubits measure and correct phase-flip errors. The cat qubits were further stabilized by connecting each of them to a buffer mode that uses a non-linear process called two-photon dissipation to ensure that their noise bias is maintained over time.
According to Harry Putterman, a senior research scientist at AWS, the team’s foremost challenge (and innovation) was to ensure that the system did not introduce too many bit-flip errors. This was important because the system uses a classical repetition code as its “outer layer” of error correction, which left it with no redundancy against residual bit flips. With this aspect under control, the researchers demonstrated that their superconducting quantum circuit suppressed errors from 1.75% per cycle for a three-cat qubit array to 1.65% per cycle for a five-cat qubit array. Achieving this degree of error suppression with larger error-correcting codes previously required tens of additional qubits.
On a scalable path
AWS’s director of quantum hardware, Oskar Painter, says the result will reduce the development time for a full-scale quantum computer by 3-5 years. This is, he says, a direct outcome of the system’s simple architecture as well as its 90% reduction in the “overhead” required for quantum error correction. The team does, however, need to reduce the error rates of the error-corrected logical qubits. “The two most important next steps towards building a fault-tolerant quantum computer at scale is that we need to scale up to several logical qubits and begin to perform and study logical operations at the logical qubit level,” Painter tells Physics World.
According to David Schlegel, a research scientist at the French quantum computing firm Alice & Bob, which specializes in cat qubits, this work marks the beginning of a shift from noisy, classically simulable quantum devices to fully error-corrected quantum chips. He says the AWS team’s most notable achievement is its clever hybrid arrangement of cat qubits for quantum information storage and traditional transmon qubits for error readout.
However, while Schlegel calls the research “innovative”, he says it is not without limitations. Because the AWS chip incorporates transmons, it still needs to address both bit-flip and phase-flip errors. “Other cat qubit approaches focus on completely eliminating bit flips, further reducing the qubit count by more than a factor of 10,” Schlegel says. “But it remains to be seen which approach will prove more effective and hardware-efficient for large-scale error-corrected quantum devices in the long run.”
Physicists in Serbia have begun strike action today in response to what they say is government corruption and social injustice. The one-day strike, called by the country’s official union for researchers, is expected to result in thousands of scientists joining students who have already been demonstrating for months over conditions in the country.
The student protests, which began in November, were triggered by a railway station canopy collapse that killed 15 people. Since then, it has grown into an ongoing mass protest seen by many as indirectly seeking to change the government, currently led by president Aleksandar Vučić.
The Serbian government, however, claims it has met all student demands such as transparent publication of all documents related to the accident and the prosecution of individuals who have disrupted the protests. The government has also accepted the resignation of prime minister Miloš Vučević as well as transport minister Goran Vesić and trade minister Tomislav Momirović, who previously held the transport role during the station’s reconstruction.
“The students are championing noble causes that resonate with all citizens,” says Igor Stanković, a statistical physicist at the Institute of Physics (IPB) in Belgrade, who is joining today’s walkout. In January, around 100 employees from the IPB in Belgrade signed a letter in support of the students, one of many from various research institutions since December.
Stanković believes that the corruption and lack of accountability that students are protesting against “stem from systemic societal and political problems, including entrenched patronage networks and a lack of transparency”.
“I believe there is no turning back now,” adds Stanković. “The students have gained support from people across the academic spectrum – including those I personally agree with and others I believe bear responsibility for the current state of affairs. That, in my view, is their strength: standing firmly behind principles, not political affiliations.”
Meanwhile, Miloš Stojaković, a mathematician at the University of Novi Sad, says that the faculty at the university have backed the students from the start especially given that they are making “a concerted effort to minimize disruptions to our scientific work”.
Many university faculties in Serbia have been blockaded by protesting students, who have been using them as a base for their demonstrations. “The situation will have a temporary negative impact on research activities,” admits Dejan Vukobratović, an electrical engineer from the University of Novi Sad. However, most researchers are “finding their way through this situation”, he adds, with “most teams keeping their project partners and funders informed about the situation, anticipating possible risks”.
Missed exams
Amidst the continuing disruptions, the Serbian national science foundation has twice delayed a deadline for the award of €24m of research grants, citing “circumstances that adversely affect the collection of project documentation”. The foundation adds that 96% of its survey participants requested an extension. The researchers’ union has also called on the government to freeze the work status of PhD students employed as research assistants or interns to accommodate the months’ long pause to their work. The government has promised to look into it.
Meanwhile, universities are setting up expert groups to figure out how to deal with the delays to studies and missed exams. Physics World approached Serbia’s government for comment, but did not receive a reply.
Researchers in Australia have developed a nanosensor that can detect the onset of gestational diabetes with 95% accuracy. Demonstrated by a team led by Carlos Salomon at the University of Queensland, the superparamagnetic “nanoflower” sensor could enable doctors to detect a variety of complications in the early stages of pregnancy.
Many complications in pregnancy can have profound and lasting effects on both the mother and the developing foetus. Today, these conditions are detected using methods such as blood tests, ultrasound screening and blood pressure monitoring. In many cases, however, their sensitivity is severely limited in the earliest stages of pregnancy.
“Currently, most pregnancy complications cannot be identified until the second or third trimester, which means it can sometimes be too late for effective intervention,” Salomon explains.
To tackle this challenge, Salomon and his colleagues are investigating the use of specially engineered nanoparticles to isolate and detect biomarkers in the blood associated with complications in early pregnancy. Specifically, they aim to detect the protein molecules carried by extracellular vesicles (EVs) – tiny, membrane-bound particles released by the placenta, which play a crucial role in cell signalling.
In their previous research, the team pioneered the development of superparamagnetic nanostructures that selectively bind to specific EV biomarkers. Superparamagnetism occurs specifically in small, ferromagnetic nanoparticles, causing their magnetization to randomly flip direction under the influence of temperature. When proteins are bound to the surfaces of these nanostructures, their magnetic responses are altered detectably, providing the team with a reliable EV sensor.
“This technology has been developed using nanomaterials to detect biomarkers at low concentrations,” explains co-author Mostafa Masud. “This is what makes our technology more sensitive than current testing methods, and why it can pick up potential pregnancy complications much earlier.”
Previous versions of the sensor used porous nanocubes that efficiently captured EVs carrying a key placental protein named PLAP. By detecting unusual levels of PLAP in the blood of pregnant women, this approach enabled the researchers to detect complications far more easily than with existing techniques. However, the method generally required detection times lasting several hours, making it unsuitable for on-site screening.
In their latest study, reported in Science Advances, Salomon’s team started with a deeper analysis of the EV proteins carried by these blood samples. Through advanced computer modelling, they discovered that complications can be linked to changes in the relative abundance of PLAP and another placental protein, CD9.
Based on these findings, they developed a new superparamagnetic nanosensor capable of detecting both biomarkers simultaneously. Their design features flower-shaped nanostructures made of nickel ferrite, which were embedded into specialized testing strips to boost their sensitivity even further.
Using this sensor, the researchers collected blood samples from 201 pregnant women at 11 to 13 weeks’ gestation. “We detected possible complications, such as preterm birth, gestational diabetes and preeclampsia, which is high blood pressure during pregnancy,” Salomon describes. For gestational diabetes, the sensor demonstrated 95% sensitivity in identifying at-risk cases, and 100% specificity in ruling out healthy cases.
Based on these results, the researchers are hopeful that further refinements to their nanoflower sensor could lead to a new generation of EV protein detectors, enabling the early diagnosis of a wide range of pregnancy complications.
“With this technology, pregnant women will be able to seek medical intervention much earlier,” Salomon says. “This has the potential to revolutionize risk assessment and improve clinical decision-making in obstetric care.”
In this episode of the Physics World Weekly podcast, we explore how computational physics is being used to develop new quantum materials; and we look at how ultrasound can help detect breast cancer.
Our first guest is Bhaskaran Muralidharan, who leads the Computational Nanoelectronics & Quantum Transport Group at the Indian Institute of Technology Bombay. In a conversation with Physics World’s Hamish Johnston, he explains how computational physics is being used to develop new materials and devices for quantum science and technology. He also shares his personal perspective on quantum physics in this International Year of Quantum Science and Technology.
Our second guest is Daniel Sarno of the UK’s National Physical Laboratory, who is an expert in the medical uses of ultrasound. In a conversation with Physics World’s Tami Freeman, Sarno explains why conventional mammography can struggle to detect cancer in patients with higher density breast tissue. This is a particular problem because women with such tissue are at higher risk of developing the disease. To address this problem, Sarno and colleagues have developed a ultrasound technique for measuring tissue density and are commercializing it via a company called sona.
Bhaskaran Muralidharan is an editorial board member on Materials for Quantum Technology. The journal is produced by IOP Publishing, which also brings you Physics World
A counterintuitive result from Einstein’s special theory of relativity has finally been verified more than 65 years after it was predicted. The prediction states that objects moving near the speed of light will appear rotated to an external observer, and physicists in Austria have now observed this experimentally using a laser and an ultrafast stop-motion camera.
A central postulate of special relativity is that the speed of light is the same in all reference frames. An observer who sees an object travelling close to the speed of light and makes simultaneous measurements of its front and back (in the direction of travel) will therefore find that, because photons coming from each end of the object both travel at the speed of light, the object is measurably shorter than it would be for an observer in the object’s reference frame. This is the long-established phenomenon of Lorentz contraction.
In 1959, however, two physicists, James Terrell and the future Nobel laureate Roger Penrose, independently noted something else. If the object has any significant optical depth relative to its length – in other words, if its extension parallel to the observer’s line of sight is comparable to its extension perpendicular to this line of sight, as is the case for a cube or a sphere – then photons from the far side of the object (from the observer’s perspective) will take longer to reach the observer than photons from its near side. Hence, if a camera takes an instantaneous snapshot of the moving object, it will collect photons from the far side that were emitted earlier at the same time as it collects photons from the near side that were emitted later.
This time difference stretches the image out, making the object appear longer even as Lorentz contraction makes its measurements shorter. Because the stretching and the contraction cancel out, the photographed object will not appear to change length at all.
But that isn’t the whole story. For the cancellation to work, the photons reaching the observer from the part of the object facing its direction of travel must have been emitted later than the photons that come from its trailing edge. This is because photons from the far and back sides come from parts of the object that would normally be obscured by the front and near sides. However, because the object moves in the time it takes photons to propagate, it creates a clear passage for trailing-edge photons to reach the camera.
The cumulative effect, Terrell and Penrose showed, is that instead of appearing to contract – as one would naïvely expect – a three-dimensional object photographed travelling at nearly the speed of light will appear rotated.
The Terrell effect in the lab
While multiple computer models have been constructed to illustrate this “Terrell effect” rotation, it has largely remained a thought experiment. In the new work, however, Peter Schattschneider of the Technical University of Vienna and colleagues realized it in an experimental setup. To do this, they shone pulsed laser light onto one of two moving objects: a sphere or a cube. The laser pulses were synchronized to a picosecond camera that collected light scattered off the object.
The researchers programmed the camera to produce a series of images at each position of the moving object. They then allowed the object to move to the next position and, when the laser pulsed again, recorded another series of ultrafast images with the camera. By linking together images recorded from the camera in response to different laser pulses, the researchers were able to, in effect, reduce the speed of light to less than 2 m/s.
When they did so, they observed that the object rotated rather than contracted, just as Terrell and Penrose predicted. While their results did deviate somewhat from theoretical predictions, this was unsurprising given that the predictions rest on certain assumptions. One of these is that incoming rays of light should be parallel to the observer, which is only true if the distance from object to observer is infinite. Another is that each image should be recorded instantaneously, whereas the shutter speed of real cameras is inevitably finite.
Because their research is awaiting publication by a journal with an embargo policy, Schattschneider and colleagues were unavailable for comment. However, the Harvard University astrophysicist Avi Loeb, who suggested in 2017 that the Terrell effect could have applications for measuring exoplanet masses, is impressed: “What [the researchers] did here is a very clever experiment where they used very short pulses of light from an object, then moved the object, and then looked again at the object and then put these snapshots together into a movie – and because it involves different parts of the body reflecting light at different times, they were able to get exactly the effect that Terrell and Penrose envisioned,” he says. Though Loeb notes that there’s “nothing fundamentally new” in the work, he nevertheless calls it “a nice experimental confirmation”.
The research is available on the arXiv pre-print server.
The integrity of science could be threatened by publishers changing scientific papers after they have been published – but without making any formal public notification. That’s the verdict of a new study by an international team of researchers, who coin such changes “stealth corrections”. They want publishers to publicly log all changes that are made to published scientific research (Learned Publishing 38 e1660).
When corrections are made to a paper after publication, it is standard practice for a notice to be added to the article explaining what has been changed and why. This transparent record keeping is designed to retain trust in the scientific record. But last year, René Aquarius, a neurosurgery researcher at Radboud University Medical Center in the Netherlands, noticed this does not always happen.
After spotting an issue with an image in a published paper, he raised concerns with the authors, who acknowledged the concerns and stated that they were “checking the original data to figure out the problem” and would keep him updated. However, Aquarius was surprised to see that the figure had been updated a month later, but without a correction notice stating that the paper had been changed.
Teaming up with colleagues from Belgium, France, the UK and the US, Aquarius began to identify and document similar stealth corrections. They did so by recording instances that they and other “science sleuths” had already found and by searching online for for terms such as “no erratum”, “no corrigendum” and “stealth” on PubPeer – an online platform where users discuss and review scientific publications.
Sustained vigilance
The researchers define a stealth correction as at least one post-publication change being made to a scientific article that does not provide a correction note or any other indicator that the publication has been temporarily or permanently altered. The researchers identified 131 stealth corrections spread across 10 scientific publishers and in different fields of research. In 92 of the cases, the stealth correction involved a change in the content of the article, such as to figures, data or text.
The remaining unrecorded changes covered three categories: “author information” such as the addition of authors or changes in affiliation; “additional information”, including edits to ethics and conflict of interest statements; and “the record of editorial process”, for instance alterations to editor details and publication dates. “For most cases, we think that the issue was big enough to have a correction notice that informs the readers what was happening,” Aquarius says.
After the authors began drawing attention to the stealth corrections, five of the papers received an official correction notice, nine were given expressions of concern, 17 reverted to the original version and 11 were retracted. Aquarius says he believes it is “important” that reader knows what has happened to a paper “so they can make up their own mind whether they want to trust [it] or not”.
The researchers would now like to see publishers implementing online correction logs that make it impossible to change anything in a published article without it being transparently reported, however small the edit. They also say that clearer definitions and guidelines are required concerning what constitutes a correction and needs a correction notice.
“We need to have sustained vigilance in the scientific community to spot these stealth corrections and also register them publicly, for example on PubPeer,” Aquarius says.
