The 1920s was an era of transformation. In the US, the “Roaring Twenties” saw industrial growth, the rise of consumerism, and huge social change, marked by jazz music, prohibition and flapper fashion. Europe, meanwhile, was recovering from the devastating First World War, and experiencing political and economic instability alongside flourishing artistic and intellectual movements. And India – which was still under British rule at the time – was embracing Mahatma Gandhi’s policy of non-violence and civil disobedience, accelerating its nationalistic movement towards independence.

Amid worldwide cultural and sociopolitical change, another revolution was unfolding in science, particularly in our understanding of physical phenomena that cannot be explained by the classical laws of physics. Intense efforts were being made by European scientists to reconcile puzzling observations, and ground-breaking ideas were being introduced – such as Max Planck’s hypothesis of “quanta” and Albert Einstein’s quantization of electromagnetism. The first quantum revolution was flourishing.

In the midst of this excitement, a modest man from Bengal in undivided India, Satyendra Nath Bose, was teaching physics at Dacca (now Dhaka) University.  He was greatly inspired by the new ideas in physics, and set about trying to solve the big inconsistency with the Plank distribution of black body radiation – the fact that it mixed classical and quantum concepts. Bose introduced the ground-breaking notion of indistinguishability of particles into the evolving quantum theory to rectify the problem, culminating in an equation describing the distribution of energy in the radiation from a black body purely based on quantum physics.

Bose’s derivation of Planck’s law impressed Einstein, who had also been trying to solve the problem. He translated the work and submitted it to Zeitschrift für Physik journal on Bose’s behalf. Bose’s novel quantum statistical approach later became known as Bose–Einstein statistics. Einstein followed up with its extension to atoms and the prediction of Bose–Einstein condensates. Bose’s work was a breakthrough for quantum mechanics, and there have since been many discoveries and multiple Nobel prizes awarded for work related to his research. He also laid the foundation for novel technologies that are central to today’s “second quantum revolution”. This exciting era encompasses themes such as quantum computing, communications, sensing and metrology, and materials and devices. Bose’s scientific breakthroughs were not his only contributions to physics at the time.

Competent and capable

Bose lived in an era when women were not welcome in the scientific community in India, as was the case in much of the rest of the world. Infamously, in 1933 biochemist Kamala Sohonie – who went on to be the first Indian woman to get a PhD in a scientific discipline – was denied admission to the Indian Institute of Science by the then-director Chandrasekhara Venkata Raman. Best known for his work on light scattering, Raman believed that women were not competent enough to do scientific research. While Sohonie eventually did get a place, she had to fight hard for it, and Raman enforced certain restrictions. For example, she was on probation for a year and Raman had to approve her work before it could be officially recognized.

Bose on the other hand, did not make any distinction between men and women as far as scientific ability was concerned. In 1951 he welcomed PhD student Purnima Sinha to his group at the University of Calcutta. Despite being the only woman in the team, Sinha succeeded in leaving her indelible imprint on a male-dominated world, helped by the constant guidance and encouragement she received from Bose.

Sinha’s research was on crystallographic and thermal analysis of clay samples taken from all over India. She built sophisticated X-ray instruments using military scrap equipment sold on the streets of Calcutta (now Kolkata) after the Second World War. In 1956 Sinha was awarded her doctorate, becoming the first woman to earn a PhD in physics from Calcutta University (and likely the first woman to get a PhD in physics from an institution in India).

She went on to conduct research in biophysics at Stanford University in the US, and found similarities between clay structure and DNA structure, providing pioneering thoughts on the origin of life. Sinha further broke gender stereotypes by doing masonry work, carpentry and even playing the tabla (a pair of hand drums). Bose was equally supportive of Asima Chatterjee, who started her research on medicinal plant extracts with Bose, and conducted the first small-molecule X-ray diffraction, which was ground-breaking work.

Breaking through

While times have changed and women today have more freedom to pursue science, technology, engineering and mathematics (STEM), these areas continue to be dominated by men. India produces the highest percentage of female STEM graduates in the world (43%), but women make up only 14% of the STEM workforce in the country and 18.6% of those directly involved in research and development activities.

The representation of women in the science and technology sector remains strikingly low, both in terms of job applicants and leadership roles. For example, a survey by the Council of Scientific Industrial Research (CSIR) in 2022 revealed that no woman had held the role of director general of CSIR until August of that year when chemical engineer Nallathamby Kalaiselvi became the first woman to lead the institute – a role that she still holds. Indeed, only five of the 35 CSIR labs were led by women at the time of the survey.

Gender bias and traditional role segregation are some of the key reasons why women remain under-represented in STEM careers in India. Several studies have found that women leave the workforce at key phases in their life – notably when they have children – and are also often rejected when seeking jobs because of gender discrimination.

However, the picture is changing rapidly, aided by educational initiatives and grassroots movements advocating for gender equity. The quickly growing quantum sector is no different, and the need for quantum education is greater than ever, as a shortage of trained researchers is being felt globally.

One person hoping to inspire and educate women and girls about quantum computing is Nithyasri Srivathsan – a student at Nanyang Technological University, Singapore, who founded SheQuantum in 2020. The start-up company has built an e-learning platform offering lectures, quantum computing courses and other educational resources, as well as articles and interviews with experts. It was listed by The Quantum Insider as one of the “9 Educational Platforms to get the Quantum Workforce Up & Running“, alongside IBM, Microsoft and MIT xPRO among others.

Another example is Women for Quantum (W4Q), which was set up by a group of female physics professors, mostly based in Europe and Japan, who work in the field of quantum optics, quantum many-body physics and quantum information. In its manifesto, the initiative highlights the “unsatisfactory current situation of women in quantum physics” and calls for a joint effort to make real change in the field.

Celebrating success

The good news is that such efforts seem to be paying off. According to the latest All India Survey on Higher Education (AISHE) (2020–2021) women make up 42.3% of undergraduate, postgraduate, MPhil, and PhD places in STEM education. There has also been a surge in women in all fields of STEM, including quantum science, where they are making significant contributions to the second quantum revolution.

To celebrate the growing presence of women at the forefront of quantum science in India, the S N Bose National Centre for Basic Sciences in Kolkata arranged an international conference in July 2024 on Women in Quantum Science and Technologies. The meeting was part of celebrations marking the 100th anniversary of Bose’s seminal work, highlighting that his legacy encompasses both quantum science and gender equality in physics.

The three-day conference consisted of six talks from accomplished female scientists, two panel discussions, three special lectures, 10 invited talks from early-career women working across quantum science and technologies, and a poster session by PhD students. The panel discussions focused on the challenges faced by women in higher education and ways to overcome them, as well as opportunities for women in the quantum arena. Speakers included Rupamanjari Ghosh, Aditi Sen De, Indrani Bose, Anjana Devi, Shohini Ghose and Efrat Shimshoni.

Such events highlight the achievements of women in the field, providing a platform for sharing research and inspiring future generations. This visibility is crucial for normalizing women’s participation in science and encouraging girls to pursue careers in physics and related disciplines.

With the second quantum revolution in progress, and the next likely to be driven by commercial innovations in areas such as cybersecurity, eco-materials and medical advancements, it is important to ensure that these breakthroughs do not reinforce societal inequalities. For that, we need women, and other under-represented groups in physics, to be encouraged into the field to ensure a diverse range of ideas.

To this end, here we highlight some women at the forefront of quantum science in India. The list is far from exhaustive, but it offers a glimpse of the broader picture.

Beyond academia

Impressive women in quantum science are not limited to academia. Government departments and industry in India can boast of some prominent female leaders. For example, Anindita Banerjee is a product manager for quantum technology projects at the Centre for Development of Advanced Computing (CDACINDIA), a premier research and development organization founded by the Ministry of Electronics and Information Technology. Anupama Ray is an award-winning senior research scientist at IBM Research in Bangalore, where she focuses on developing quantum machine learning algorithms. Meanwhile at Microsoft India and South Asia, Rohini Srivathsa is the chief technology officer, responsible for driving technology innovation and growth across industry and the government.

In addition to the accomplished Indian women working in quantum in their home country, there are several who have built successful careers abroad. Notable cases are Anjana Devi, director of the Institute for Materials Chemistry at the Leibniz Institute for Solid State and Materials Research, Dresden, Germany; Nandini Trivedi, professor of physics at Ohio State University, US; Nilanjana Datta, professor in quantum information theory at the University of Cambridge, UK; Vidya Madhavan, professor of physics at the University of Illinois Urbana-Champaign, US; Shohini Ghose, professor of physics and computer science, and director of research and programmes for the Centre for Women in Science at Wilfrid Laurier University in Waterloo, Canada, and chief technology officer at Quantum Algorithms Institute.

The rise of women in quantum science in India is a tribute to Bose’s legacy, and a sign of a more inclusive and dynamic future. To sustain this momentum, we must create ecosystems that support curiosity, collaboration and equal opportunity – ensuring that every brilliant mind, regardless of gender, has the chance to transform the world.

The post The rise of women in quantum science in India and the legacy of Satyendra Nath Bose appeared first on Physics World.

Researchers in Japan have accelerated muons into the most precise, high-intensity beam to date, reaching energies high as 100 keV. The achievement could enable next-generation experiments such as better measurements of the muon’s anomalous magnetic moment – measurements that could, in turn, that point to new physics beyond the Standard Model.

Muons are sub-atomic particles similar to electrons, but around 200 times heavier. Thanks to this extra mass, muons radiate less energy than electrons as they travel in circles – meaning that a muon accelerator could, in principle, produce more energetic collisions than a conventional electron machine for a given energy input.

However, working with muons comes with challenges. Although scientists can produce high-intensity muon beams from the decay of other sub-atomic particles known as pions, these beams must then be cooled to make the velocities of their constituent particles more uniform before they can be accelerated to collider speeds. And while this cooling process is relatively straightforward for electrons, for muons it is greatly complicated by the particles’ short lifetime of just 2 ms. Indeed, traditional cooling techniques (such as synchrotron radiation cooling, laser cooling, stochastic cooling and electron cooling) simply do not work.

Another muon cooling and acceleration technique

To overcome this problem, researchers at the MUon Science Facility (MUSE) in the Japan Proton Accelerator Research Complex (J-PARC) have been developing an alternative muon cooling and acceleration technique. The MUSE method involves cooling positively-charged muons, or antimuons, down to thermal energies of 25 meV and then accelerating them using radio-frequency (rf) cavities.

In the new work, a team led by particle and nuclear physicist Shusei Kamioka directed antimuons (μ+) into a target made from a silica aerogel. This material has a unique property: a muon that stops inside it gets re-emitted as a muonium atom (an exotic atom consisting of an antimuon and an electron) with very low thermal energy. The researchers then fired a laser beam at these low-energy muonium atoms to remove their electrons, thereby producing antimuons with much lower – and, crucially, far more uniform – velocities than was the case for the starting beam. Finally, they guided the slowed particles into a rf cavity, where an electric field accelerated them to an energy of 100 keV.

Towards a muon accelerator?

The final beam has an intensity of 2 × 10⁻³ μ+ per pulse, and a measured emittance that is much lower (by a factor of 2.0 × 10² in the horizontal direction and 4.1 × 10² vertically) than the starting beam. This represents a two-orders-of-magnitude reduction in the spread of positions and momenta in the beam and makes accelerating the muons more efficient, says Kamioka.

According to the researchers, who report their work in Physical Review Letters, these improvements are important steps on the road to a muon collider. To make further progress, however, they will need to increase the beam’s energy and intensity even further, which they acknowledge will be challenging.

“We are now preparing for the next acceleration test at the new experimental area dedicated to muon acceleration,” Kamioka tells Physics World. “A 4 MeV acceleration with 1000 muon/s is planned for 2027 and a 212 MeV acceleration with 10⁵ muon/s is planned for 2029.”

In total, the MUSE team expects that various improvements will produce a factor of 10⁵–10⁶ increase in the muon rate, which could be enough to enable applications such as the muon g−2/EDM experiment at J-PARC, he adds.

The post High-quality muon beam holds promise for future collider appeared first on Physics World.

In 2018, the Muon g-2 Experiment at Fermilab near Chicago, set out to measure the muon’s anomalous magnetic moment to a precision of 140 parts per billion (ppb). This component of the muon’s magnetic moment is the result of several subtle quantum effects and is also known as the muon g-2 – which reflects how the gyromagnetic ratio of the muon deviates from the simple value of two.

After six years of producing, storing, and measuring more than a trillion muons, the collaboration released its long-anticipated final result in June, achieving an unprecedented precision of 127 ppb. This landmark measurement not only solidifies confidence in the experimental value of muon g-2 but also sets a new benchmark as the most precise accelerator-based measurement of a fundamental particle to date.

Studies of the muon g-2 have served as a rigorous test of the Standard Model – physicist’s leading theory describing known particles and forces – for much of the last century. Theoretically, the muon’s anomalous magnetic moment can be predicted from the Standard Model to a similar precision as the experiment. For decades, a persistent discrepancy between prediction and measurement hinted at the possibility of new physics, with experimental results favouring a higher value than the theory. Such a difference, if confirmed, could point to phenomena not accounted for in the Standard Model – potentially explaining unresolved mysteries like the existence of dark matter.

However, extraordinary claims require extraordinary scrutiny. To address the experimental side, Fermilab launched the Muon g-2 Experiment. On the theoretical side, the Muon g-2 Theory Initiative was established as a global collaboration of theorists working to refine the Standard Model prediction using state-of-the-art methods, techniques, and input data.

Problematic contribution

One of the most problematic contributions to the theoretical value is the hadronic vacuum polarization (HVP), historically determined using experimental data as input to complex calculations. While the Theory Initiative has improved these methods, progress has remained limited due to discrepancies in the available experimental data. Crucially, a recent input from the CMD-3 Experiment diverged significantly from previous results, suggesting a larger HVP contribution (see figure below). This, in turn, yields a Standard Model prediction that aligns with the new Fermilab measurement – apparently eliminating the discrepancy and, with it, any evidence of new physics.

Despite years of investigation, the origin of the CMD-3 tension remains unknown. Its result stands in contrast to a vast catalogue of earlier data from multiple experiments over decades. As a result, the traditional, data-driven approach to estimating the HVP is deemed currently unable to produce a reliable estimate .

Thanks to the efforts of the Theory Initiative, however, the HVP can now also be calculated using lattice QCD (quantum chromodynamics) simulations on supercomputers, reaching a precision comparable to that of the data-driven methods. Multiple independent lattice QCD groups have arrived at consistent values, which also agree with the Fermilab measurement, indicating no discrepancy and thus no sign of new physics. This computational feat, once considered out of reach, marks a major breakthrough. Yet, the tension remains unresolved: Why do lattice QCD and CMD-3 agree, while both conflict with decades of experimental data?

No physics beyond the Standard Model

Given the improved control in lattice QCD, the Theory Initiative has also recently updated its recommended Standard Model prediction with the HVP fully based on lattice results. The resulting value agrees with the Fermilab measurement and currently implies no evidence for physics beyond the Standard Model. However, the Initiative has emphasized that this is far from conclusive. Future predictions are intended to incorporate data-driven estimates again – once the inconsistencies in the experimental input are resolved.

The field now faces two possibilities. One is that the CMD-3 result and lattice QCD are correct. In this case, there is no new physics – but an impressive validation of the Standard Model. The other scenario is that new experimental HVP input data align with the older results, supporting a smaller HVP contribution. This would reintroduce the discrepancy with the Fermilab result, reviving the exciting possibility of new physics. In either case, the inconsistencies between CMD-3, lattice QCD, and the existing data must be explained.

So, is there new physics or not? We know there must be. The Standard Model cannot not explain dark matter, the accelerating expansion of the universe, the absence of antimatter, or the quantum nature of gravity. Precision tests like muon g-2 offer a window into this unknown. That window has not closed – for now it’s propped open.

Where we’ll be in five years is uncertain. The Muon g-2 Theory Initiative will continue to refine predictions and resolve open questions. For now, one thing is clear: the Muon g-2 Experiment at Fermilab has delivered an historic achievement and its legacy will continue to contribute to our understanding of fundamental physics for decades to come.

 

The post Muon g-2 achieves record precision, but theoretical tensions remain appeared first on Physics World.

An imbalance in sodium ions in the blood causes a number of physiological problems, but so far it has not been possible to measure these ion concentrations in vivo. Now researchers have successfully applied their terahertz optoacoustic technology to measure blood ion concentrations non-invasively, overcoming the challenges posed by previous approaches. They report their findings in Optica.

The idea to combine terahertz spectroscopy with optoacoustic detection came about during a recruitment trip when Zhen Tian from the School of Precision Instrument and Optoelectronics Engineering at Tianjin University in China got chatting with colleague Jiao Li – co-author of this latest study. At the time, Tian’s work was focused primarily on terahertz technology while Li had been working on optoacoustics, but the more they talked, the more interested they became in each other’s fields, and took “every available opportunity to discuss these topics in depth” during the trip.

Putting their heads together on their return, in 2021 they successfully demonstrated terahertz optoacoustic detection of ions in water, despite the challenges of the pandemic. “We thought things would progress smoothly from there, but deeper investigations revealed a series of technical challenges,” Tian tells Physics World. “What began as a fortunate opportunity soon turned into a demanding endeavour.”

The sodium focus

Since ions are strongly polar, they absorb highly in the terahertz range, making them easy to detect. As such, Tian and Li were keen to find a scenario where the tracking of ions might be useful. Another colleague at Tianjin University (also a co-author on this new study) pointed out that ion imbalances in the blood can cause kidney disease and serious neurological conditions. The most abundant ion in the blood is sodium, and as Li explains, not only do imbalances in sodium ions need prompt correction, but the lack of means for monitoring sodium ions in vivo poses risks of neural demyelination and brain damage during sodium ion supplementation.

One of the key challenges was the high water content of body tissues, because water absorbs terahertz radiation so strongly. The researchers turned this to an advantage by using the water to detect emitted terahertz radiation from the sample, exploiting the fact that the optoacoustic response is temperature dependent. At cold temperatures, absorbing terahertz radiation emitted from the sample heats up the water, which detectably impacts its optoacoustic signal. Therefore, comparing the sample’s optoacoustic response to terahertz radiation with values for pure water gives a quantitative indication of the absorption by the sample and thus the concentration of ions present.

Although the researchers demonstrated a proof-of-principle for this approach in 2021, they then had to battle with several other issues. They improved the stability of the light source by reducing thermal fluctuations and making other optimizations to the experimental environment; they used higher-intensity light sources and enhanced detectors to increase the detection sensitivity; and they used spectral filtering to achieve molecular specificity in the optoacoustic detection. Tian expresses his gratitude to Yixin Yao, a co-first author of the paper, as well as to the students involved. “It was their commitment and perseverance that helped us overcome each hurdle,” he says.

The team demonstrated that the enhanced system could detect sodium ions in human blood flowing through a microfluid chip and measure increases in blood sodium levels in living mice. The operating temperature for the technique was 8 °C, cold enough to cause damage to many parts of the body. However, the researchers noted that the ear is particularly resilient to temperature, so they cooled and monitored just the animal’s ear, limiting the experiment duration to 30 min. This way they were able to complete their measurements without incurring any tissue damage.

Although the numerous previous in vitro experiments had left the researchers full of “anticipation” for the success of the attempts in vivo, Tian tells Physics World, “when we saw the terahertz optoacoustic signal enhance after sodium ion injection, all of us, including the students conducting the experiment, cheered with excitement”.

“It is very nice to see [that] fundamental studies on dielectric response of aqueous salt solutions may result in a sensor for human health,” says Andrea Markelz from the University at Buffalo, whose research focuses on biomolecular dynamics and terahertz time domain spectroscopy, although she was not directly involved in this study. She notes that tagless terahertz-based biomonitoring is challenging, due to both the strong aqueous background and the lack of narrowband signatures. “It will be very interesting to see if the sensitivity remains robust for different organisms under different conditions,” she adds.

Next, Tian and his collaborators plan to apply the approach to detect neural ion activity without the need for labelling. “It’s admittedly a bold and ambitious idea – but one that has truly excited our team,” he says.

The post Terahertz optoacoustics allows real-time monitoring of blood sodium levels appeared first on Physics World.

Researchers at the Okinawa Institute of Science and Technology (OIST) in Japan have identified the first known example of hyperdisorder occurring in a biological system. This phenomenon combines order at the microscopic scale with disorder at the macro level, and it is often present in systems studied in statistical physics. However, the researchers were surprised to observe it while monitoring the development of pigment cells in squid skin. As the hyperdisorder is directly linked to the squid’s growth, the researchers say the discovery could shed light on the physics of growing structures.

In inanimate objects, the emergence of disordered patterns is relatively well understood in physical terms. Living creatures are different, however, as they can display unexpected phenomena as they grow and develop.

To better understand how growth impacts the formation of patterns, a team led by Robert Ross, Simone Pigolotti and Sam Reiter at OIST studied how pigment cells known as chromatophores arrange themselves on the skin of squid as the animal grows and its skin expands. “These pigment cells are important because they play an essential role in camouflage and communication for these animals,” Reiter explains.

Highly unusual statistical patterns

The researchers took a series of 3D optical images of the squid over a period of three months. These observations revealed that the chromatophores behave very differently from other disordered structures. “The chromatophores appear at fixed positions in relation to one another, in a specific pattern,” Reiter explains.

It is this pattern that met the technical criteria for hyperdisorder, which is defined as occurring when the variation in the number of points within a particular measured space increases more rapidly than the volume of that space.

In the squid he and his colleagues studied, Ross explains that new chromatophores appear only at a minimum exclusion distance from pre-existing ones as the animal grows. “We found that this rule coupled with tissue growth leads to the highly unusual statistical patterns we observe,” he says. “Simply put, when you observe a tiny area in a system, it may appear quite ordered, but when viewed at larger scales, it becomes more disordered.”

To explain this finding, the researchers modelled squid development as static circle packing on a growing surface and showed how the hyperdisordered behaviour emerges. “The result is exciting because it highlights the importance of growth on physical properties,” Ross says.

A general feature of many biological structures?

The researchers note that other growing systems, such as the cells in chicken retinas, often display the exact opposite property, which is known as hyperuniformity. In these systems, there is long-range order and patterning despite randomness at a close scale, Ross explains. Such behaviour is thought to provide optimal retinal coverage properties for vision. “This is what we thought we would see in the squid, but what we actually observed was quite different and we have not yet seen any other instances of this packing behaviour in biology,” he says.

The mechanisms described in this work, which is detailed in Physical Review X, may be common in growing, dense natural systems, says Ross: “Indeed, this simple type of growth combined with distance-limited cell insertion might be a general feature of many biological structures.”

Spurred on by their findings, the researchers plan to continue working on a variety of theoretical and experimental systems related to the physics of growing structures. “These include both growing brains and pattern formation in fish,” says Ross.  “We hope these systems will provide further examples of the novel physics of growing systems,” he tells Physics World.

The post Hyperdisorder appears in pigment patterns on squid skin appeared first on Physics World.

Fashion designer Iris van Herpen has unveiled a bioluminescent dress that features 125 million living algae. The garment involved Herpen collaborating with designer Chris Bellamy as well as biophysicists Nico Schramma and Mazi Jalaal from the University of Amsterdam.

Bioluminescence is the production of light by a living organism, caused by a chemical reaction such as the molecule luciferin reacting with oxygen to release light.

The bioluminescent dress is composed of a gel material that incorporates millions of single celled bioluminescent algae of the species Pyrocystis lunula, named after their moon-like shape.

In the wild, the bioluminescent algae emit light as a defence mechanism. The flash serves as a warning signal that attracts secondary predators, which hunt the main predator of the cells.

In 2019, Jalaal, Schramma and colleagues began to study how the cells respond to mechanical stresses. By combining microscopy and mechanical tests, they were able to measure the light-emission of the cells and how it depended on deformation, which led to a mathematical model that described the light-production mechanism (Phys. Rev. Lett. 125 028102).

The researchers then worked with Chenghai Li and Shengqiang Cai at the University of California San Diego and bioluminescence researcher Michael Latz from the Scripps Institution of Oceanography in San Diego.

They incorporated the cells in a gel matrix to create a flexible yet resistant substance that emits light upon deformation and movement while at the same time keeping the cells alive.

Bellamy and van Herpen developed and refined the bioluminescent material and incorporated it into a spectacular “living” garment, which on Monday was part of van Herpen’s new fashion collection – Sympoiesis – that was unveiled at Paris Haute Couture Week.

The post Physics meets fashion as bioluminescent dress debuts at Paris Haute Couture Week appeared first on Physics World.

Astronomers at the University of Hawai’i’s Institute for Astronomy (IfA) in the US have detected what they say are the most energetic cosmic explosions known to have occurred since the the universe began. These colossal events, dubbed extreme nuclear transients (ENTs), emit at least 10 times as much energy as the previous record holders, and studying them could open a new window into physical processes that take place at very high energies.

ENTs occur when stars that are at least three times as massive as the Sun pass so close to a supermassive black hole that its colossal gravity shreds them to pieces. The resulting string of matter then spirals into the black hole in a phenomenon known as accretion.

Such events are extremely rare, occurring a few hundred times less frequently than supernovae. However, when they do happen, they release huge amounts of energy, producing long-lasting flares that can then be detected on Earth.

Optical transient surveys have spotted several classes of accretion-powered flares over the past decade or so, explains Jason Hinkle, who led the study as part of his PhD research at the IfA. Examples include tidal disruption events, rapid turn-on active galactic nuclei and ambiguous nuclear transients.

The new ENTs are a different kettle of fish, however. They release between 0.5 × 10⁵³ and 2.5 × 10⁵³ erg (0.5‒2.5 × 10⁴⁶ J) making them at least twice as energetic as any other known transient. “They are also 10 times as bright (emitting 2 × 10⁴⁵ to 7 × 10⁴⁵ erg per second) and remain luminous for years, far surpassing the energy output of even the brightest known supernova explosions,” Hinkle says.

Looking for smooth, high-amplitude and long-lived signals

Hinkle began searching for ENTs at the beginning of his PhD studies by sifting through data from the European Space Agency’s Gaia mission. Gaia is ideal for such a search as it has been observing the full sky since late 2014. As a space-based mission, it also typically has shorter seasonal breaks than ground-based surveys.

Hinkle’s search for smooth, high-amplitude, long-lived signals revealed two possible sources. Designated Gaia16aaw (AT2016dbs) and Gaia18cdj (AT2018fbb), each comes from the centre of a distant galaxy. For Gaia16aaw, that galaxy bears the catchy name WISEA J041157.03-420530.8. Gaia18cdj, for its part, lies within the equally memorable WISEA J020948.15-420437.1

In 2020, astronomers began observing these sources with space-based UV/X-ray missions and ground-based facilities, including the University of Hawai’i’s Asteroid Terrestrial-impact Last Alert System and the W M Keck Observatory. “These gave us the first indication that we were seeing something special,” Hinkle says. “When the Zwicky Transient Facility [a wide-field optical survey] published data on a third similar event, ZTF20abrbeie, also sometimes called ‘Scary Barbie’ (AT2021lwx), in 2023, it gave us additional confidence that we had found a rare, new class of transient phenomena.”

These data show that the brightness of the light emitted from ENTs increases for more than 100 days, peaks, and then slowly declines over a period of more than 150 days. ENTs also produce infrared light, which suggests that circumnuclear dust is being heated up and reemitted at longer wavelengths, Hinkle says.

The fact that Gaia16aaw and Gaia18cdj are located relatively close to the centres of their host galaxies (within 0.68 and 0.25 kpc, respectively) confirms their status as nuclear transients, he adds. Their long timescales and high peak luminosities also suggest that they originate from accretion onto a supermassive black hole. “The way they accrete is very different from normal black hole accretion, however, which typically shows irregular and unpredictable changes in brightness,” Hinkle explains. “Instead, the smooth and long-lived flares of ENTs imply a distinct physical process – the gradual accretion of a tidally disrupted star by a supermassive black hole.”

Several ENTs could be detected per year

According to IfA team member Benjamin Shappee, ENTs provide a valuable new tool for studying massive black holes in distant galaxies. Since they are so bright, they can be seen across vast cosmic distances, equivalent to redshifts between z = 4 and 6. This means they could give astronomers new information about black hole growth when the universe was less than half its present age, during a period when galaxies were forming stars and feeding their supermassive black holes up to 10 times more vigorously than they are today.

Now that astronomers know what to look for, Hinkle says that new survey instruments such as the Vera C Rubin Observatory and NASA’s Roman Space Telescope should turn up several ENTs per year. “From a physics perspective, building a sample of ENTs will give us the best look yet at massive black holes in the early universe, especially the large majority of those that are not otherwise accreting,” he says. “This will serve as an excellent complement to studies of accreting black holes in the early universe with the James Webb Space Telescope, for example.

“We have a great starting point, but as with many things in observational astronomy, we need larger samples to gain a fuller understanding of how these events work and how we can best use them to test fundamental physics.”

The present study is detailed in Science Advances.

The post Astronomers observe the biggest booms since the Big Bang appeared first on Physics World.

Researchers in Denmark have produced the acoustic equivalent of a rainbow, creating a structure that spatially decomposes sound into its component frequencies in free space. Developing such a structure had proven difficult due to the complexity required, but the team at Danmarks Tekniske Universitet (DTU) managed it thanks to an advanced structural design technique. The new architecture could be used to make devices tailored to emit or receive certain frequencies of sound.

Optical rainbows occur when white light is split into its different spectral components, for example by passing through dispersive media such as prisms or droplets. Although acoustic rainbows are less well-known, they follow the same principle, being the spatial decomposition of sound in free space where waves oscillating at different frequencies propagate in different directions. They have previously been created in confined media using arrays of resonant structures that “trap” sound at different positions in space depending on their frequency. Examples include waveguides, solid and/or fluid mixtures and devices known as acoustic circulators.

Acoustic spectral decomposition also occurs in several natural structures, including the outer ear structures, or pinnae, of mammals such as bats, cetaceans and primates. Indeed, the pinnae of primates (including humans) have an intricate geometry that generates complex interference phenomena via scattering of sound waves, thereby enabling the animals to localize external sources of sound.

An acoustic scattering structure

While researchers have previously attempted to imitate such biological designs, these efforts were largely unsuccessful. The new work, which was co-led by Rasmus Ellebæk Christiansen and Efren Fernandez-Grande at the DTU, succeeded in part thanks to a new technique known as computational morphogenesis, or topology optimization.

This technique, which the researchers describe in Science Advances, builds on an earlier morphogenetic design framework for tailoring passive acoustic scattering structures with dimensions on the order of a few wavelengths. Using an iterative process, the team spatially redistributed sound-reflecting material in an air background inside a specified region of space. This enabled them to tailor the sound field emitted from the created structure to match a predefined target emission pattern across a specified frequency band, mimicking naturally-occurring “sound shaping” structures.

“Such a technique is possible today thanks to the rapid growth in computational power in recent years that has allowed us to model and synthesize sound on the large scale,” Ellebæk Christiansen explains. When combined with advanced production techniques like additive manufacturing (also known as 3D printing), he adds that the team benefitted from “nearly unlimited design freedom”, with the new technique enabling the design of metamaterials and nonintuitive structures hitherto deemed unrealizable.

“Our approach to designing the structures is to re-formulate the device design problem carefully and meticulously as a mathematical optimization problem and to use topology optimization to solve this problem,” he explains. “In this way, we do not rely on simplified design rules derived from underlying physics models, on design intuition or on prior design experience to come up with our device geometry. Instead, we use rigorous mathematical modelling and simulation coupled with advanced numerical algorithms.”

Towards new and very different structures/geometries

The geometry and topology of the metamaterial the team created has several features reminiscent of structures present in the pinnae that spatio-spectrally decompose sound, Ellebæk Christiansen says. However, he tells Physics World that the technique may also enable them to develop structures/geometries that offer new possibilities never realized in nature.

One option, Fernandez-Grande suggests, would be to design acoustic materials that reflect different frequencies of sound in different ways – for example, by scattering high frequencies diffusely and redirecting low frequencies towards an absorbing surface. “It might also help in the development of acoustic lenses – that is, sound sources (such as loudspeakers) that control how different frequencies are radiated in space,” Fernandez-Grande adds.

In the future, the researchers would like to transition from their current two-dimensional design to one that is fully three-dimensional. “This would offer significantly more design freedom, and acoustic field complexity, which might allow for even better/more elaborate spatio-spectral sound field control,” Ellebæk Christiansen says.

The post Acoustic rainbows emerge from novel sound-scattering structure appeared first on Physics World.

This podcast features an interview with Sara Alderweireldt, who is a physicist working on the ATLAS experiment at CERN – the world-famous physics lab that straddles the Swiss-French border and is home to the Large Hadron Collider (LHC).

Based at the UK’s University of Edinburgh, Alderweireldt is in conversation with Physics World’s Margaret Harris and explains how physicists sift through the vast amount of information produced by ATLAS’ myriad detectors in search of new physics.

They also chat about the ongoing high-luminosity upgrade to the LHC and its experiments – which will be finished in 2030 – and the challenges and rewards of working a very long term project.

The post Inside ATLAS: Sara Alderweireldt explains how the CERN experiment homes in on new physics appeared first on Physics World.

Construction has begun on the new headquarters of the European Centre for Medium-Range Weather Forecasts (ECMWF). Yesterday, senior officials marked the start of construction on the new £93m centre at the University of Reading, which will provide cutting-edge meteorological research and forecasting.

The ECMWF is an independent intergovernmental organization with 35 member and cooperating states. Established in 1975, the centre employs around 500 staff from more than 30 countries at its existing headquarters at Shinfield Park in Reading, UK, and sites in Bologna, Italy, and Bonn, Germany.

As a research institute and 24/7 operational service, the ECMWF produces global numerical weather predictions four times per day and other data for its member/cooperating states and the broader meteorological community.

The new centre at the University of Reading, built by construction firm Mace, is funded by the UK’s Department for Science, Innovation and Technology. When it opens in 2027, it will accommodate up to 300 scientists and staff who will relocate from Shinfield Park.

The centre will carry out work on all aspects of weather prediction, forecast production and research into climate change.

“This state-of-the-art facility places the UK at the heart of international efforts that are helping us to make better sense of our weather and climate,” notes UK science minister Patrick Vallance. “By improving our weather predictions we can optimise our energy consumption estimates, adjust transport schedules effectively and give our farmers time to prepare for extreme weather – helping people and businesses to save money, cut energy use and stay safe.”

The post Construction begins on new £93m European weather-forecasting headquarters appeared first on Physics World.

The UK technology industry is struggling with persistent challenges around diversity and inclusion. That is according to a new report by the Department for Science, Innovation and Technology, which concludes that despite some modest recent progress, all minority groups still remain significantly underrepresented in the technology sector.

The tech startup ecosystem is valued at over $1.1 trillion worldwide with the technology sector employing more than 1.8 million people in the UK. Women and people from ethnic-minority groups, however, account for only around a quarter of the technology workforce. People from ethnic-minority groups also only hold 14% of senior roles.

Based on surveys of UK technology industries and a review of existing research on the sector, the report finds that recent diversity gains diminish at mid-career and leadership levels. In the last year, female representation in senior technology positions increased by only 1%, while one in three women are planning to quit their jobs due to a lack of career progression, poor work-life balance and an unsupportive culture.

This persistent “leaky pipeline” is linked to structural and cultural barriers that result in poor retention and promotion of underrepresented people. Cultural attitudes reinforce this gender bias, the report says, with one recent study finding that 20% of men in technology believe that women are “naturally less suited” to technical work. Indeed, a previous national study found that underrepresented minorities were nearly twice as likely to leave a technology job because of unfair treatment than for a better role.

Underrepresentation is particularly stark for Black technologists, who make up only 5% of workers, while just 0.07% of technology employees are Black women. Socio-economic diversity is also poor with only 9% of technology employees coming from poorer backgrounds, compared with 29% in finance and 23% in law. Data also shows that individuals from working-class backgrounds in technology earn, on average, almost £5000 less per year than their peers from more affluent backgrounds.

’Lack of progress’

There is also a lack of diversity when it comes to technology funding, with the report showing that 92% of angel investments in 2022 went to all-white teams, while female and ethnic minority-led startups secured just 2% of venture capital funding. On average female-founded technology businesses receive £1.1m, figures show, while male-owned startups receive £6.2m.

The report also points to one analysis that found that about 14% of technologists identify as disabled, while another put the figure as low as 6%, suggesting a reluctance to disclose disabilities. The later survey also suggests that 53% of technology employees identify as neurodivergent, yet employers claim that just 3% of their staff are neurodivergent.

To improve diversity and inclusion in the technology sector, the report calls for improvements in flexible-working options; diversity, equity and inclusion reporting; improved governance structures; and socio-economic mobility initiatives.

Sarah Bakewell, head of diversity and inclusion at the Institute of Physics, which publishes Physics World, describes the report’s conclusions as “concerning” as “it reveals the lack of diversity in the sector and who funding is allocated to”. Even more worrying, she says, is the lack of progress in boosting the diversity of people in UK tech. “To unleash a new wave of UK innovation, we must attract, develop and retain people from all backgrounds in inclusive work environments where everyone can realise their full potential.”

The post Diversity in the UK tech sector must improve, says report appeared first on Physics World.

As they approach a black hole’s event horizon, particles of accreting gas can take on opposing orbital trajectories – remarkably similar to the paths produced in manmade particle colliders. Using advanced new models, Andrew Mummery at the University of Oxford, together with Joseph Silk at Sorbonne University, showed how such particles could collide at colossal energies, with detectable collision products that could offer valuable new insights for particle physics.

Within a black hole’s accretion disk, gas particles travel in circular orbits that gradually shrink under its immense gravity. Once an orbit contracts beneath a critical radius, it becomes unstable, and the particles it carries will suddenly plunge toward the black hole.

“Long ago, Roger Penrose showed that these particles could extract energy from the spin of massive black holes in the region where they decay,” Silk explains. “This happens in the ergosphere – the region just outside the event horizon where debris can gain energy from the black hole’s intense gravitational and rotational fields.”

In the theory described by Penrose, a particle approaching a black hole splits into two fragments – possibly through a collision or spontaneous decay. After the split, one fragment falls into the event horizon, while the other gains enough energy from the black hole’s spin to escape its gravity – exiting the ergosphere with more energy than the original particle.

Building on this idea, Silk and two of his previous collaborators – Maximo Bañados and Stephen West – proposed an alternative escape mechanism. Their idea involves gas particles in retrograde orbits (moving opposite to the black hole’s spin) within the accretion disk. Since a retrograde orbit becomes unstable at larger radii than a prograde orbit (movement in the same direction as the black hole’s rotation), these particles fall farther before reaching the ergosphere, allowing them to gain more energy through gravitational acceleration.

Within the ergosphere, Bañados, Silk and West considered how these now highly energetic particles could collide with those originating from prograde orbits, travelling in opposite directions. If this occurred, the relative velocity between the two would be enormous – imparting extreme relativistic energies to their collision products. The trio proposed that some of these products could escape the ergosphere with more energy than either of the original particles.

In their latest study, reported in Physical Review Letters, Silk and Mummery explored this possibility in greater detail. They used models recently developed by Mummery to simulate the flow of particles accreting onto rapidly spinning supermassive black holes.

“We showed that the infalling gas would develop a pattern of turbulent rotating and counter-rotating vortices as it plunged into the black hole’s ergosphere,” Silk explains. The rotation direction of each vortex depends on whether the particles originated from prograde or retrograde orbits within the accretion disk.

When particles travelling in opposite directions collide in the ergosphere, their circular paths resemble the magnetically guided trajectories of protons and heavy ions in manmade particle colliders, such as CERN’s Large Hadron Collider – only on a vastly larger scale. “We found that the collisions occurred at hundreds of times higher energies than those reached in any existing collider, and would approach or even exceed the energies expected for the proposed Future Circular Collider,” Silk notes.

At such colossal energies, Mummery and Silk predict that the collision products could include gamma rays and ultrahigh-energy neutrinos, which might be detectable from nearby supermassive black holes – such as Sagittarius A* at the centre of our own galaxy. As a result, the process could offer an entirely new approach to observations in particle physics.

“Our predicted signatures would complement those of the next generation of giant particle supercolliders planned by CERN and in China, helping to provide evidence of new particle physics beyond the Standard Model,” says Silk. In particular, the duo suggest that these signatures could lead to a highly sensitive probe of dark matter – potentially offering more robust tests for candidates such as weakly interacting massive particles.

The post Black holes could act as cosmic supercolliders appeared first on Physics World.

The Norwegian-born condensed-matter physicist Ivar Giaever, who shared the Nobel Prize for Physics in 1973, died on 20 June at the age of 96. In the late 1950s, Giaever made pioneering progress in the electron tunnelling in superconductors as well as provided a crucial verification of the Bardeen–Cooper–Schrieffer (BCS) theory of superconductivity.

Born in Bergen, Norway, on 5 April 1929, Giaever graduated with a degree in mechanical engineering in 1952 from the Norwegian Institute of Technology. Following a year of military service he worked as a patent examiner for the Norwegian government before moving to Canada in 1954 where he began working at General Electric.

Two years later he moved to GE’s research laboratory in New York, where he continued to study the company’s engineering courses. In 1958 he joined the GE’s R&D centre as a researcher.

At the same time, Giaever began to study physics at Rensselaer Polytechnic Institute in New York where he obtained a PhD in 1964 working in tunnelling and superconductivity. That year he also became a naturalized US citizen.

A Nobel life

It was work in the early 1960s that led to his Nobel prize. Following the Japanese physicist Leo Esaki’s discovery of electron tunnelling in semiconductors in 1958, Giaever showed that tunnelling also happened in superconductors, in this case a thin later of oxide surrounded by a metal in a superconducting state.

Using his tunnelling apparatus, Giaever also measured the energy gap near the Fermi level when a metal becomes superconducting, providing crucial verification of the BCS theory of superconductivity.

At the age of 44, Giaever shared half the 1973 Nobel Prize for Physics with Esaki “for their experimental discoveries regarding tunnelling phenomena in semiconductors and superconductors, respectively”. The other half went to Brian Josephson “for his theoretical predictions of the properties of a supercurrent through a tunnel barrier, in particular those phenomena which are generally known as the Josephson effects”.

Josephson told Physics World that Giaever’s experiments were the source of his interest in tunnelling supercurrents. “An interesting point is that none the [physics] laureates that year were professors at the time,” adds Josephson. “[Giaever] and I were too junior, while Esaki was in industry”.

In 1988 Giaever left General Electric and moved to Rensselaer where he continued to work in biophysics. In 1993, he founded the New York-based Applied BioPhysics Inc.

As well as the Nobel prize, Giaever also won the Oliver E Buckley Prize by the American Physical Society (APS) in 1965 as well as the Golden Plate Award by the American Academy of Achievement in 1966.

Gaiever’s career was not withouth controversy. In 2011 he resigned from the APS in protest after the organisation called the evidence of damaging global warming “incontrovertible”.

In 2016 he published his autobiography I am the Smartest Man I Know, in which he details his journey from relatively humble beginnings in Norway to a Nobel prize and beyond.

The post Norwegian-US Nobel laureate Ivar Giaever dies aged 96 appeared first on Physics World.

Every mystical quest features a journey riddled with challenges, a cast of colourful characters, and a treasure trove that unlocks more intrigue. The Meteorite Hunters: On the Trail of Extraterrestrial Treasures and the Secrets Inside Them is no exception to this canon.

Written by science journalist Joshua Howgego, the book takes the reader on the pursuit of space rocks and how they have unravelled our understanding of the solar system. And, as is so often the way in science as it is with quests, the search and the people you meet along the way are just as interesting as the discoveries themselves.

Towards the end of Meteorite Hunters, Howgego confides that his aim for the book distils down to two questions: “how do you find them, and what do they tell us?”. Indeed, the tale follows this two-act structure pretty neatly. The first half sees the eponymous hunters and their adventures take centre stage, with enough science dotted throughout to set the scene for the second half, which takes us right up to date with the very latest missions to asteroids Itokawa and Ryugu, and the return of the Bennu sample from the OSIRIS-Rex mission. It is a tactic that is kind to the general reader, and there are plenty of interesting anecdotes and characters to keep things from getting too dry, along with some truly astonishing astrophysics.

The journey begins with a look at how people came to understand that rocks can fall from the sky. The truth of course is that civilizations throughout human history have (separately but repeatedly) come to this realization. Howgego highlights how existing knowledge and compelling physical evidence of meteorites from central South American cultures was dismissed as primitive superstitious nonsense by European invaders in the 16th century. It is the perennial story of knowledge being lost during the waves of European colonialism.

Western understanding of meteorites only really gets going in the very late 18th century, and Howgego introduces two key characters who helped cement the topic as a legitimate line of enquiry. Ernst Chladni was a German polymath who wrote the first book on meteorites in 1794 but whose ideas were initially ridiculed. Meanwhile, playwright and journalist Edward Topham had a large meteorite fall on his land in 1795 (witnessed by labourer John Shipley) and went on to the champion the idea of rocks falling from the sky. However, it would take until the mid-1960s, and the anticipation of lunar samples being returned by the Apollo missions, for this area of study to crystallize into the modern field of meteoritics.

Drama and dust

The origin story of many modern meteorite hunters – those who go out searching for these space rocks – often begin in a similar vein to that of Topham, with an inspiring find close to home leading to elaborate expeditions to track down historic falls. The meteorite scientists Howgego interviews are diplomatic when asked about the hunters – after all, they have the resources to investigate reports of fresh falls much more quickly than the hunters can decipher historical reports and local legends. But there is also a real tension between the two camps – there are serious issues with permanent loss of data from the scientific record through mishandling or denial of access to specimens in private collections.

Howgego goes on to discuss efforts to track meteorite falls in real-time, which may be more scientific and systematic but are no less dramatic. Modern programmes involving networks of automated digital cameras can trace their origins back to a resourceful young scientist, Zdeněk Ceplecha, who narrowly escaped the worst of the Stalinist purges in soviet Czechoslovakia. In 1959 he managed to reconstruct the trajectory of an incoming meteorite to within a very respectable margin of modern computations by using long-exposure photographic plates. In a beautiful full-circle moment, the tracking network initiated by Ceplecha followed a 2002 meteorite fall that turned out to have the exact same trajectory as that 1959 space rock – confirming that the two came from the same parent body.

One of the book’s more modern – and most interesting – characters is Swedish jazz guitarist Jon Larsen. His obsession of sifting through tonnes of urban dust for elusive micrometeorites has yielded invaluable (and beautifully photographed) specimens – something dismissed as an urban myth before someone with his patience and ingenuity came along. These pristine remnants of the protoplanetary disc, literal “star dust”, offer unique insights into the earliest days of our solar system.

Alongside his array of characters, Howgego creates a beautiful and accessible rendering of the complex astrophysics underlying the evolution and structure of our solar system as revealed from the study of meteorites. The descriptions of how competing theories have developed and merged also gives a realistic insight into the scientific method in action; consensus building, refinement through accretion of evidence, and an admission that the picture is not yet settled.

The hunt for, and study of, meteorites touches upon an unexpected variety of topics in modern science. But Howgego manages to weave them seamlessly together into a rich fabric, allowing his colourful cast of characters to tell their fascinating stories.

• 2025 Oneworld Publications 272pp £18.99 hb / £9.99 ebook

The post Space rock quest: meet the people hunting meteorites appeared first on Physics World.

A new experiment that measures the quantum tunnelling of photons between two waveguides has produced results that are hard to reconcile with certain deterministic interpretations of quantum mechanics. According to the experimenters, this constitutes a long-sought experimental test of theories that were previously regarded as empirically indistinguishable from conventional quantum mechanics.

In the widely-held Copenhagen interpretation of quantum mechanics developed by physicists such as Werner Heisenberg and Niels Bohr in the 1920s, particles do not have definite properties (such as behaving like a particle or a wave) until they are measured. Instead, a particle’s properties are defined only by its wavefunction, and the square of this wavefunction dictates the probability of the particle being in a particular state when measured.

An alternative interpretation, favoured by physicists such as David Bohm and Louis de Broglie, is that the properties of the particle are everywhere defined by a non-local “guiding equation”.  In the famous quantum double-slit experiment, therefore, the particle does not pass through both slits and interfere with itself. Instead, it passes through one slit or the other, but the probability of it passing through each slit is dictated by the value of the guiding equation. Closing or moving one of the slits alters this equation.

Though most physicists today reject Bohmian mechanics, the differences between it and the Copenhagen interpretation are largely conceptual. “Bohmian mechanics and orthodox quantum mechanics are definitely not physically equivalent – they don’t describe the same things happening in the world,” explains mathematical physicist Sheldon Goldstein of Rutgers University in New Jersey, US. “But they are empirically equivalent – they give the same predictions, the same probabilities, for all possible experiments – which is a kind of striking fact, but it’s true nonetheless.”

A test of Bohmian mechanics?

In the new work, however, Jan Klärs and colleagues at the University of Twente in the Netherlands claim to have devised a test in which the two interpretations predict different results – and Copenhagen wins. To perform this test, the researchers set up two waveguides side by side. When they sent pulses of light down one of the waveguides, light leaked into the other waveguide by quantum tunnelling.  By knowing the strength of the coupling and measuring the quantum tunnelling as a function of distance, they could infer the speed of the photons.

The researchers also introduced a potential step into the first waveguide. As this step was too large for photons to tunnel through, they were largely reflected, but with an exponentially decaying evanescent field inside the step. Bohmian mechanics agrees completely with standard quantum mechanics on the expected density of particles in this field. However, the guiding equation predicts that the velocity of these particles – which can never be measured directly – is zero.

The researchers therefore used the energy of the photons to calculate their expected speeds inside the potential step, and compared this to the tunnelling rate between the two waveguides. They found that particles that were expected to have higher velocity travelled further before tunnelling into the other waveguide. “We interpret this as a speed measurement,” says Klärs. “When you interpret this as a speed measurement, it gives you a speed that is different from the fundamental guiding equation.”

Questions of interpretation

Goldstein, who was not involved in the research, is unconvinced: “There is a theory in Bohmian mechanics where the particles [inside the potential step] are at rest, but for the experiment they give, the Bohmian velocity is not especially relevant to a correct analysis,” he says. “Whatever analysis they’re doing, if they claim that it correctly predicts the analysis based on Schrödinger’s equation, then that would be the conclusion of Bohmian mechanics, and the real thing for them to look at is why was the Bohmian velocity not the thing that corresponds to the result?”

Experimental physicist Aephraim Steinberg of the University of Toronto, Canada is equally sceptical that the work refutes Bohmian mechanics. He points out that the researchers carefully note that the measurements were made in equilibrium, so whether the exponential decay into the step can be interpreted as a speed warrants further discussion by the community.

Nevertheless, he credits their ingenuity. “This particular experiment gave a result that, even after 20 years thinking about tunnelling times, I did not know the answer to,” he says. “There are things in quantum mechanics like ‘how long does a particle spend in a region?’ that sound to our classical ears like they should only have one answer, but that can in fact have multiple answers.”

The research is published in Nature.

The post New experiment challenges Bohmian quantum mechanics appeared first on Physics World.

It wasn’t until the second year of my undergraduate degree that someone finally put a name to why I’d been struggling with day-to-day things throughout my life – it was Attention Deficit Hyperactivity Disorder (ADHD). It explained so much; my extreme anxiety around work and general life, my poor time management, the problems I had regulating my emotions, and my inability to manage everyday tasks. Being able to put a label on it, and therefore start taking steps to mitigate the worst of its symptoms, was a real turning point in my life.

As such, when I started my PhD at the Quantum Engineering Centre for Doctoral Training at the University of Bristol, I got on the (notoriously long) waiting list for an assessment and formal diagnosis. I knew that because of my ADHD, my PhD journey would look a little different compared to the average student, and that I’d have to work harder in some aspects to mitigate the consequences of my symptoms.

People with ADHD exhibit a persistent pattern of inattention, hyperactivity and/or impulsivity that interferes with day-to-day life. It is a type of neurodivergence – when someone’s brain functions in a different way to what is considered “typical”. Other neurodivergent conditions include autism, dyslexia and dyspraxia, but the term also encompasses mental-health issues, learning difficulties and acquired neurodivergence (for example, after a brain injury).

According to Genius Within, at least 5% of the population have ADHD, 1–2% are autistic, 14% have mental health needs, and many more have other neurodevelopmental conditions. It is also common for those with one neurodivergence to have one or more other co-occurring neurodivergent conditions.

However, if you look specifically at the scientific community, these percentages are much higher. For example, in a 2024 survey “Designing Neuroinclusive Laboratory Environments” run by HOK, it was found that out of 241 individuals, 18.6% had ADHD and 25.5% were autistic. If neurodivergent people remain highly overrepresented in the sciences, then it is imperative that we understand and accommodate for the needs of these individuals in work and research environments.

Spiky skills

One common trait among neurodivergent people is that they have greater strengths and bigger weaknesses across skillsets when compared to neurotypical people. This is known as having a “spiky profile” – it appears as peaks and troughs above and below a “normal” baseline (figure 1). The skillsets commonly included in a profile are analytical, mathematical, motor, situational and organizational skills; relationship management; sensory sensitivities; processing speed; verbal and visual comprehension; and working memory. So while neurodivergent people may be extremely capable at certain skills, they may really struggle with others.

Personally, I have problems with working memory, organization and processing speed, but each of these issues present differently in certain situations. For example, it’s not uncommon for me to reach the end of a meeting with my supervisor and feel that I understand all that was discussed and have no questions – but then I may come up with some important queries sometime later that didn’t occur to me at the time. This demonstrates a difference in processing speed, which thankfully can be accommodated for by maintaining an open line of communication between myself and my supervisors.

Meanwhile, for Daisy Shearer – who leads the outreach and education programme at the National Quantum Computing Centre (NQCC) in the UK – their autism affects their day-to-day life in other ways. “I experience sensory inputs and emotion regulation differently to neurotypical people, which uses a lot of energy to manage,” Shearer explains. “My executive functioning skills [those that help you manage everyday tasks] tend to be poor, as well as my social skills, which I work hard to overcome.”

Despite our different neurotypes, Shearer and I also have some symptoms in common. For example, we both struggle with switching between tasks, and time blindness, which means we have difficulty in perceiving and managing time. But while many traits can overlap between neurotypes in this way, even two individuals with the same diagnosis won’t have the exact same symptoms or profile.

Abilities and sensitivities can fluctuate day-to-day or even hour-to-hour, regardless of the accommodations and strategies in place

Furthermore, neurodivergent people can be “dynamically disabled”, meaning that our abilities and sensitivities fluctuate day-to-day or even hour-to-hour, regardless of  the accommodations and strategies in place. Shearer, for instance, used to be primarily lab-based and would find that environment soothing, but occasionally the lab would become overwhelming when their sensory profile shifted.

Meanwhile for me, one day I may be able to focus and complete multiple large tasks in a day, attend various meetings and answer e-mails in a timely fashion. But on another day – sometimes even the next day – I may only be able to answer half of my e-mails and will flit between tasks, unable to focus deeply on any one thing. This can make monitoring progress and completing milestones difficult, and requires a high degree of flexibility and understanding from those around me.

Accommodating the troughs

So what can the physics community do to help people who are neurodivergent like myself? While we absolutely don’t want to be treated leniently – we want our work as physicists to be as high a standard as anyone else’s – working with individuals to accommodate them correctly is key to helping them succeed.

That’s why in 2019 Shearer founded Neuroinclusion in STEM, after having no openly autistic role models in their physics career to date. The project, which is community-driven, aims to increase the visibility of neurodivergent people in science, technology, engineering and mathematics (STEM), and provide information on best practices to make the fields more inclusive.

Shearer also takes part in many equality, diversity and inclusion (EDI) committees, and gives talks at conferences to highlight how the STEM community can improve the working environment for its neurodivergent members.

Indeed, Shearer’s own set up at the NQCC is a great example of workplace accommodations helping an employee thrive. Firstly, Shearer had a high level of autonomy in defining their role when they joined the NQCC. “It was incredibly helpful when it comes to managing how my brain works,” they explain. Shearer also has the flexibility to work from home if they’re feeling particularly sensory sensitive, and were consulted in the design of the NQCC’s “wellbeing room” – a fully sensorily controllable space that they can use during their work day when feeling overwhelmed by sensory stimuli. Other, small adjustments that have helped include having an allocated desk away from general people-traffic, and colleagues being educated to ensure a more inclusive environment.

For physicists working in a lab – dependent on health and safety measures – it can help to wear headphones or earplugs and have dimmable lights to minimize sensory inputs. Some neurodivergent people also benefit from visual aids and written instructions for experiments and equipment. Personally, as a theorist in an office, I find noise cancelling headphones, and asking colleagues to consider e-mailing rather than interrupting me at my desk, can help reduce distractions.

Reaching the peak

While education and accommodations are key, it’s also important to remember the strengths that come with having a neurodivergent spiky profile – the peaks, so to speak. “I have strong analytical, communication and creative skills,” explains Shearer, “which make me very good at what I do professionally.”

For me, I excel in visual, written and communication skills, and try to use these to my advantage. I’m good at spotting errors in mine and others’ work, I’m a concise but detailed writer, and when not working on my PhD, I’m trying to communicate complex ideas in quantum physics to different audiences with varying degrees of understanding of physics and science.

By recognizing all of our unique capabilities and adequately accommodating those additional neurodivergent struggles, we can build systems that empower instead of limit us

Reminding myself of these strengths is key, as it can be too easy to focus on the negatives that come with being neurodivergent. By recognizing all of our unique capabilities and adequately accommodating those additional neurodivergent struggles, we can build systems that empower instead of limit us.

I believe Shearer put this best: “By embracing our individual strengths, we can enable everyone to thrive in their professional and personal lives, but that can only come with understanding how to accommodate each other.”

The post Unique minds: why accommodating neurodivergent scientists matters appeared first on Physics World.

A team of researchers in Sweden has demonstrated how smart optical metasurfaces can respond far more strongly to incoming light when switched to their conducting states. By fine-tuning the spacing between arrays of nanoantennae on a polymer metasurface, Magnus Jonsson and colleagues at Linköping University were able to generate nonlocal electromagnetic coupling between the antennae – vastly strengthening the metasurface’s optical responses.

Metasurfaces are rapidly emerging as a key component of smart optical devices, which can dynamically manipulate the wavefronts and spectral signals of incoming light. “They work in a way that nanostructures are placed in patterns on a flat surface and become receivers for light,” Jonsson explains. “Each receiver, or antenna, captures the light in a certain way and together these nanostructures allow the light to be controlled as you desire.”

One promising route towards such intelligent metasurfaces is to fabricate their antennae from conducting polymers, such as PEDOT. In such materials, the intrinsic permittivity – which determines how the material responds to electric fields, such as those from incoming light – can be manually switched by altering the oxidation state through a redox reaction. This, in turn, modifies the polymer’s carrier density and mobility, altering the number and behaviour of mobile charge carriers that contribute to its optical properties.

A key measure of how well these materials resonate with light is the “quality factor”, which describes how sharp and long-lived a resonance is. A higher quality factor signifies a stronger, more precise interaction with light, while a lower value indicates weaker and broader responses.

When PEDOT is in its metallic oxidation state, incident light will drive the resonance of surface plasmons: collective oscillations of mobile charges that are confined near the surface of the material. At specific wavelengths, these plasmons can strongly enhance electromagnetic fields – altering properties including the phase, amplitude and spectral composition of the light reflected and transmitted by the metasurface.

Alternatively, when PEDOT is switched to its insulating state, the resulting lack of available charge carriers will significantly suppress surface plasmon formation, leading to diminished optical response.

In principle, this effect offers a useful way to modulate the nanoantennae of smart metasurfaces via redox reactions. So far, however, the surface plasmons generated through this approach have only resonated weakly in response to incident light, and have quickly lost their energy after excitation – even when the polymer is switched to its metallic state. This has made the approach impractical for use in smart, switchable metasurfaces that require strong and coherent plasmonic behaviour.

Jonsson’s team addressed this problem by considering the spacing of PEDOT nanoantennae within periodic arrays. When separated at precisely the right distance, the array generated nonlocal coupling through coherent diffractive interactions – involving the constructive interference of light scattered by each antenna.

As a result, this arrangement supported collective lattice resonances (CLRs) – in which entire arrays of nanoantennae respond collectively and coherently to incident light. This drastically boosted the strength and sharpness of the material’s plasmonic response, boosting its quality factor by up to ten times that of previous conducting polymer nanoantennae. Such high-quality resonances indicate more coherent, longer-lived plasmonic modes.

As before, the researchers could manually switch the nanoantenna array between metallic and insulating states via redox reactions, which reversibly weakened its plasmonic responses as required. This dynamic tuning offers a pathway towards electrically or chemically programmable optical behaviour.

Based on this performance, Jonsson’s team is now confident that this approach could have promising implications for the future of smart optical metasurfaces. “We show that metasurfaces made of conducting polymers seem to be able to provide sufficiently high performance to be relevant for practical applications,” says co-author Dongqing Lin.

For now, the researchers have demonstrated their approach across mid-infrared wavelengths. But with some further tweaks to their fabrication process, allowing for closer spacings between the nanoantennae and smaller antenna sizes, they aim to generate CLRs in the visible spectrum. If achieved, this could open up new opportunities for smart optical metasurfaces in cutting-edge optical applications as wide-ranging as holography, invisibility cloaking and biomedical imaging.

The study is described in Nature Communications.

The post Switchable metasurfaces deliver stronger light control appeared first on Physics World.

I recently heard a physicist jocularly remind us that “All science is either physics or stamp collecting”. Widely attributed to the Nobel prize-winning nuclear physicist Ernest Rutherford, this quotation is often interpreted as the pre-eminence of physics over other scientific disciplines. While there is some doubt about whether Rutherford actually uttered that phrase, what’s interesting for me is not its origins but why the statement has – or ought to have – little place in today’s world.

In an era of rapid technological advancement and complex global challenges, it has never been more important for the scientific community to work together. From tackling climate change and dealing with the opportunities and risks of artificial intelligence to exploring space and ensuring everyone has advanced and accessible healthcare, we need experts from different disciplines to work together. No single domain can comprehensively address such challenges.

That’s why all of us in Science, Technology, Engineering, Mathematics and Medicine (STEMM) need to work together collectively and with one voice. Fortunately, there are many examples of where this already occurs. Biomedical engineering, for example, has seen physicists, chemists, biologists, material scientists and medical experts develop many successful innovations, such as prosthetics, joint implants, artificial organs and advanced imaging technologies.

The development of machine learning algorithms for healthcare applications, meanwhile, requires computer scientists, statisticians and medical professionals. By embracing collaboration, the strengths of multiple disciplines can be exploited to drive innovation and create solutions that would be difficult – and sometimes even impossible – to achieve in isolation

Sharing knowledge

Without such collaboration, any solution would be incomplete and likely impractical. By working together, STEMM professionals are creating holistic solutions that address our technical, environmental and societal needs. However, it’s vital that we share knowledge and expertise so that STEMM professionals can learn from one another and build on existing work.

In today’s ever-changing world, staying informed about the latest developments is critical. Collaborative efforts ensure that knowledge is disseminated quickly and efficiently, thereby reducing duplication of effort and speeding up progress. It also fosters creativity by encouraging individuals to think beyond the boundaries of their own expertise. Innovation often occurs at the intersection of disciplines.

When people from different fields collaborate, they bring unique perspectives and methodologies that can lead to ground-breaking discoveries. Just look at the Human Genome Project (HGP), which involved teams of researchers working together to achieve a common goal. The HGP was a voyage of biological discovery led by an international group of researchers looking to comprehensively study all the DNA of a select set of organisms.

Launched in October 1990 and completed in April 2003, the HGP’s major accomplishment – generating the first sequence of the human genome – provided fundamental information about the human blueprint, which has since accelerated the study of human biology and improved the practice of medicine. What we need are more such projects where people work together towards a common goal.

Avoiding siloes

Competition and siloed thinking can, however, hinder progress. Individuals and companies may be reluctant to share knowledge or resources due to concerns about leaking intellectual property, not getting recognition or losing funding opportunities. But knowledge needs to be spread, not least because vesting know-how in a single individual is risky if that person leaves an organization. When you share knowledge, you never know what it can lead to.

Collaborative teams with people from different disciplines are better equipped to handle setbacks and challenges as, when faced with obstacles, team members can rely on each other for support and help seeking alternative solutions. Collective resilience is important in STEMM fields, where failure is often a stepping stone to success. Ultimately the progress and success of humanity depends on our ability to work together.

In practical terms, I am pleased to say that the Institute of Physics (IOP) Business Innovation Awards, which have been running for almost 15 years, embrace much of what I have been talking about. They recognize and celebrate small, medium and large companies that have excelled in innovation, delivering significant economic and/or societal impact through the application of physics.

Whilst the award-winning product innovations recognized by the IOP need to have some link to physics, they almost always involve some other fundamental science. What’s more, the innovations invariably need input from engineering design and manufacture, from software development, and from expertise in, say, medicine, aerospace, nuclear power or food science. Successful winners demonstrate strong multidisciplinary collaboration within their teams.

The bottom line is that’s vital for STEMM professionals to stick together and not try to trump each other with statements like Rutherford’s. For collaboration to work effectively, it requires mutual respect across all contributors. And by working well together, we will drive innovation, help solve complex problems, and shape a better future for the world. As a physicist by training, I naturally have a certain loyalty to the subject. But I’m hugely grateful for what I’ve learnt and achieved by working with people from other disciplines.

The post United we stand: why physicists must quit their siloes appeared first on Physics World.

A new microscope inspired by the design of Keplerian telescopes produces much sharper images from luminescence from biological cells than was possible with previous devices. Dubbed the “QIScope” by its creators, the device’s highly sensitive camera can detect extremely low levels of light and could be used to observe delicate biostructures in greater detail and over longer periods of time without damaging them.

Many organisms naturally produce light via special enzymes in their cells. Although most such bioluminescent creatures are found in the ocean – think of anglerfish and firefly squid – there are also examples of terrestrial bioluminescent organisms, including bacteria and molluscs.

For researchers in life sciences, harnessing this light is an attractive alternative to imaging organisms using fluorescence. This is because it does not rely on strong external illumination, which can damage cells or interfere with the subtle signals they produce. The downside is that bioluminescence is feeble by comparison, so using it produces relatively low-resolution images.

Researchers led by Jian Cui of Helmholtz Munich and the Technical University of Munich, Germany, have now used a new detector technology called a quantum image sensor (QIS) to improve the resolution of bioluminescence imaging. By integrating this sensor into an unconventional optical microscope design, they increased the number of photons per pixel without sacrificing spatial resolution or field-of-view (FOV), as previous bioluminescence microscopes did.

“Telescope-within-a-microscope”

To avoid this restriction, which is known as vignetting, Cui explains that the team separated the two lenses and inserted a Keplerian telescope between them. “This ‘telescope-within-a-microscope’ reshapes the output of the objective lens to match the width of the tube lens’ back aperture,” he says.

The resulting “QIScope”, as the researchers call it, substantially reduces the size of the image while still capturing the full FOV. The result: an instrument with a higher signal-to-noise ratio and spatial resolution, leading to crisper images than was possible before.

“New detector technologies are being developed all the time and some of them are very impressive,” Cui says. “However, we shouldn’t think about simply putting cameras on microscopes – sometimes you need to design the microscope around the properties of the camera. And this is what we have done.”

The researchers, who detail their work in Nature Methods, hope it will spur more interest in bioluminescence as an imaging tool. “There is a lot of untapped potential here and it could have advantages for certain applications such as studying photosensitive samples or low-abundance proteins,” Cui tells Physics World. “It could be used to study a range of biological systems – from single cells to organoids and tissue models. And since it can be used for long periods, it could reveal subtle and long-term changes in cell behaviour, so supporting progress in diverse research areas, including cell biology, disease modelling and drug discovery.”

The post New ‘telescope-microscope’ detects extremely low levels of light appeared first on Physics World.

A physicist from Vilnius University in Lithuania has created a 3D-printed replica of the Sorbonne Chapel so small it fits on a human hair.

Located in Paris’s Latin Quarter, the Chapel of Sainte-Ursule de la Sorbonne is a Roman Catholic chapel and was constructed in the 17th century.

To create the structure, Gordon Zyla, who carries out research in light technologies at Vilnius’s Laser Research Centre, used a laser nanofabrication technique known as multiphoton 3D lithography.

“Unlike conventional 3D printing, this approach can solidify a light-sensitive material at virtually any point in space, enabling the fabrication of truly 3D structures,” notes Zyla.

The length of the finished product is approximately 120 micrometres long, being 275,000 times smaller than the original yet still preserving its architectural details.

Late last week, the model was presented as a symbolic gift to Sorbonne University president Nathalie Drach-Temam during a visit to Vilnius.

The post Vilnius University physicist creates micron-sized model of the Sorbonne Chapel appeared first on Physics World.

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 motion and 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.

The post Electric field treatment restores movement to rats with spinal injuries appeared first on 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.”

The post Mysterious seismic wave speed-up deep within Earth’s mantle explained at last appeared first on Physics World.

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.

These disappointing statistics are reported in “Towards a fully inclusive environment for disabled people in STEMM” and this podcast features an interview with one of its authors – the physicist Francesca Doddato.

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.

The post Making science careers more accessible to people with disabilities appeared first on Physics World.

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.

The research is published in Science.

The post New microscopy technique can identify topological superconductors appeared first on Physics World.