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Why the US needs a ‘quantum Oppenheimer’ to beat China in the quantum race

Quantum mechanics has the potential to change the world beyond our wildest imagination. While there are many challenges that must first be overcome, quantum technology promises to revolutionize many areas of life from computing and finance to cryptography and drug discovery. Such endless possibilities have led many countries to create their own national quantum programmes to advance progress, which are supported by billions of dollars, pounds, euros or yuan.

The nation leading the race so far to harness the power of quantum technologies is China. The country has constructed a 2000 km quantum-secured fibre-optic network and in 2017 demonstrated quantum-secured satellite communications. In 2019 and 2020 China’s demonstration of “quantum advantage” – a critical threshold on the path to powerful quantum computers – further revealed a sophistication and acceleration of its quantum-information programme.

In both political and scientific circles, some are quick to dismiss China’s recent progress, viewing Chinese publications with scepticism and asserting that the country is a “paper tiger”. Yet a closer examination of published Chinese quantum research reveals a level of detail, results and collaboration with western researchers that suggest the tiger has teeth. The Chinese are indeed prioritizing and dominating the quantum space, with every intention of winning this technology race.

China’s rapid progress is even more worrisome for the US when one considers that America was well ahead of China in quantum technology at the turn of the century. This reversal has been attributed to reduced US federal funding for quantum research between 2005 and 2015.

However, this explanation oversimplifies the US’s failures and also does not give China credit for its own advances. Inevitably, the situation is lamented in the US, with concerns ranging from China developing a quantum computer capable of cracking our most secure codes, to advanced Chinese military and industrial capabilities that vastly outpace our own.

Given China’s steady commitment and progress, the conversation in the US must now turn to asking serious questions about our level of commitment and about the need to create a timeline for accelerating the US quantum programme. Such discussions must focus on near-term defence, industry participation and policy actions that directly address the question: how can the US catch – and overtake – China in the quantum race?

A “quantum tsar”

In 2019 the US authorized $1.3bn of federal funding over five years for quantum research and development. The majority of the money goes to the national laboratories and academic universities for research, developing new quantum curricula, building quantum testbeds and growing the quantum workforce. These national laboratories and universities, in turn, are expected to engage industry partners to foster a US quantum industry with access to private investment leading to commercialization.

Unfortunately, this strategy is based on three flawed assumptions – all related to timing. First, we have a “let 100 flowers bloom” strategy that assumes the US has ample time to explore, mature and then trim unfruitful paths from a diverse cornucopia of quantum solutions.

Second, it assumes that the nation’s national laboratories and independent academic organizations will advance quantum technology at a pace that matches, or even exceeds, Chinese competitors. And third, it assumes billions of dollars in private investment to transition research into mature, market-driven solutions.

The Chinese quantum programme, in contrast, is led by quantum physicist Jian-Wei Pan and is managed by a tightly co-ordinated group of academic, government and industry partners. The programme is well resourced, with an annual budget estimated to be in the billions of dollars, and has the full support of the Chinese Communist Party. The US’s quantum race with China could be compared in some ways to the race to develop nuclear technology in the 1940s.

There are few past peace-time efforts that match the scientific magnitude and urgency associated with ushering in the quantum era

To catch the Germans, the US created the Manhattan Project where government, academic and industry partners worked largely under the leadership of Robert Oppenheimer. He successfully guided the basic nuclear R&D and engineering advances required to outpace the Germans.

Oppenheimer understood the urgency of the situation, along with the intricacies of the technology and the challenges of effectively co-ordinating specialized engineering and scientific workforces. He was the conductor of a large scientific orchestra, with the country’s best scientists and engineers serving as the players.

Where is our Oppenheimer for today’s competition to develop quantum technology? When does the quantum project begin? US institutions and researchers are among the best in the world but without a co-ordinated programme under cohesive leadership, we will remain in China’s shadow.

If the US is going to be successful in surpassing China, it must implement a streamlined, convergent strategy co-ordinated around a technically knowledgeable and programmatically skilled “quantum tsar”. This person must have the discretion to direct and distribute significant, sustained R&D funding to public and private organizations across the country.

They must oversee the selection of the various technical approaches and solutions in a careful, but swift, manner. The tsar must formulate and execute a strategy that prioritizes the rapid deployment of near-term quantum solutions and makes full use of the nation’s unique, technologically advanced industry partners.

US-China quantum rivalry creates harmful barriers to progress

This is no small feat and there are few past peace-time efforts that match the scientific magnitude and urgency associated with ushering in the quantum era. But if the US is to mount a serious challenge to the rapidly accelerating Chinese quantum effort, it must implement a new strategy that acknowledges the country’s closing window of opportunity and the need for a more technically and organizationally focused strategy.

The US must urgently advance its national conversation from a techno-centric discussion to one focused on the timing and organizational challenges of accelerating progress for the nation’s quantum programme.

Multicoloured light source gives compressive spectroscopy a boost

A solid-state electronic device array that produces time-modulated light at tuneable wavelengths has been unveiled by researchers in the US. Possible uses of the device include compressive spectroscopy, which is much easier to perform outside the laboratory than conventional spectroscopy.

Traditionally, devices such as optical spectrometers use a single, broadband light source to illuminate a sample before using diffraction gratings or other optical devices to measure the light emitted or absorbed as a function of its wavelength. Scaling this down to the microscale is possible using techniques such as colloidal quantum-dot filters, but these require a suitably broadband light source. Also, these are passive detectors, which means that they produce a signal that can be difficult to separate from ambient light.

An alternative approach, which obviates the need for a spectrally-sensitive measurement, is to vary the wavelength of the illuminating light.

Vivian Wang of the University of California, Berkeley, explains the principle: “Let’s say you have an apple or something that looks a certain colour to your eye: how do you characterize that quantitatively? You could shine a source containing a very broad range of wavelengths onto the object and then measure the wavelengths coming back out using a spectrometer, or you could shine different colours of light onto the object and then just measure the total light reflected back out onto a single point detector for each of those colours.”

Lock-in detection

One advantage of the latter approach is that the wavelength and/or the intensity of the incident radiation can be modulated at a controlled frequency, so the signal in the detected light is easy to separate from noise. “When you have something that is intrinsically pulsed, you can detect the light emission using something called lock-in detection,” explains Wang.

Fabricating multiple LEDs on the same chip can be difficult or even impossible, which would limit the number of different wavelengths that could be included. In 2020, however, Wang and UC Berkeley colleagues led by Ali Javey had made a surprising discovery.

“We had been playing around with two-dimensional semiconducting materials and we found that, when we put them on top of capacitors on silicon wafers, they emit light by the electrical excitation,” says Wang. “We found that we can also get electrically driven emission from other materials using pulse-driven capacitors…The reason this works is really complicated and is described in some of our previous papers.”

Now, the team has taken this innovation an important step towards a real engineering application. They mounted a grid of conductive carbon nanotube networks, each with its own current input, on top of a layer of silicon dioxide, which was in turn laid on a layer of doped silicon. Onto these carbon nanotube networks they deposited 49 different electroluminescent materials, ranging from cadmium selenide quantum dots to the active materials in organic LEDs. When they connected the chip to an alternating current power supply, they could produce multicoloured light with tunable wavelengths, because charging any individual capacitor would cause the emitter on top to light up.

Compressive computer algorithm

“If we want to create different combinations of light we can turn on different combinations of devices at the same time,” says Wang. The researchers then use a compressive computer algorithm to estimate the full reflection spectrum based on the information given by the reflections of each pulse.

In addition to spectroscopy, the researchers say the device has potential applications in other areas such as microscopy. The team is now working to make their array commercially viable.

“We’ve demonstrated some interesting possibilities for this device structure, like making new examples of spectral measurement, but right now we’re trying to improve the performance of these devices – like the brightness, efficiency and stability,” says Wang.

The array is described in a paper in Science Advances.

“This is a very interesting paper and potentially a very important one,” says Zongfu Yu of the University of Wisconsin-Madison; “They solve some of the problems of the traditional method [of spectral sensing] where a bulky instrument is needed as a tuneable light source. Yu and a colleague initially proposed the idea for compressive sensing back in 2014: “It generated tremendous interest from industry, but we had no idea how we would realise the light source at the time,” he says; “Later on we did some work with a fixed light source using filters, but before I read this paper yesterday, I had no idea how people could realise a tuneable light source with so diverse a spectral range.”

Why champagne bubbles rise in thin lines, kitchen ‘jacuzzi’ could clean fruit and vegetables

We live on a planet with lots of water and air, so it’s not surprising that bubbles can play important roles in a range of physical and biological processes. And that is one reason why some physicists are fascinated with bubbles. Although I suspect that having fun playing with bubbles in the lab, especially if they are in beer and champagne, is a major draw for some.

The latest breakthrough in bubble physics comes from the US and France, where Roberto Zenit of Brown University and colleagues have studied the streams of bubbles that occur in carbonated beverages.

Even the casual drinker knows that the bubbles in a glass of champagne tend to move upwards in a thin, straight line, whereas the bubbles in a glass of cola tend to move upwards in a more disperse line. Zenit and colleagues have shown that this behaviour is defined by two factors – the size of the bubbles and the presence of surfactants in the liquid. A surfactant is a chemical that reduces the surface tension between the liquid and the gas in the bubble.

Lateral forces

They found that for small bubbles or low levels of surfactant, the vortices formed in the wakes of rising bubbles exert lateral forces on the bubbles causing a broadening of the stream. In the case of larger bubbles or higher concentrations of surfactants, the lateral forces have the opposite effect, pushing the bubbles back into line.

While champagne bubbles are small, the wine is rich in surfactants so its bubbles tend to travel in straight lines. Cola, on the other hand, has larger bubbles but fewer surfactants, so the bubbles tend to follow wonkier lines. You can find out more about the research in Physics.

As well as giving drinks a tart taste, bubbles can also be used to clean surfaces. Indeed, researchers are keen on developing ways to clean food and culinary equipment using liquids filled with air bubbles. This technique is already in some industrial cleaning applications, but not much is known about how it could be optimized for use in kitchens.

Magic angle

Now, Sunny Jung and colleagues at Cornell University in the US have shown that a stream of bubbles that strikes a surface at about 22.5° and then flows upwards along the surface is the best at cleaning. They came to this conclusion by exposing two different dirty glass surfaces to streams of bubbly water at varying angles of incidence. One surface was coated with proteins derived from milk and flour, and the other with a culture of a common bacteria.

Using numerical simulations, the team verified the hypothesis that the shear force exerted by the bubbles on the surface is responsible for the cleaning. Their simulations suggested that the shear force reaches a maximum at about 22.5°.

Jung told Physics that he hopes the research will lead to the development of a “fruit jacuzzi” for cleaning delicate items of food.

Happy birthday

Normally, Physics World and Physics Today are rivals in the cutthroat world of physics publishing. But today I would like to wish Physics Today a very happy 75th birthday. In May 1948 the membership magazine of the American Institute of Physics was launched with the aim of providing a “unifying influence for the diverse areas of physics and the physics-related sciences”.

The first issue featured an article by the celebrated science administrator Vannevar Bush, who headed the US Office of Scientific Research and Development during the Second World War. I have no doubt that his article captured the excitement of those heady post-war days in America when the country was fast becoming a scientific superpower.

You can read much more about the history of the magazine in this article. It also highlights some of the advertisements that have appeared in Physics Today over the years, including one from a vendor of “war surplus bargains” and another one calling for solidarity with dissident physicists imprisoned in the USSR.

‘More than Moore’: a glimpse at the future of computing

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Earlier this year, Gordon Moore, co-founder of the chipmaker Intel, passed away aged 94. As well as helping to launch the era of the personal computer, Moore is known for his eponymous law, which states that the number of transistors on a computer chip will double about every two years.

This remarkable doubling has occurred since Moore’s law was first postulated in 1965 and has brought us mobile phones with vastly more computing power than was available on the entire planet six decades ago.

However, the atomic nature of matter and the laws of physics mean that transistors cannot keep shrinking forever; and researchers are currently looking for new ways of boosting computing power, without having to pack evermore silicon devices onto chips.

To explore what lies beyond the era of Moore’s law, IOP Publishing is presenting a webinar called “More than Moore”, which will look at some of the technologies that could play roles in the computers of the future.

The webinar will bring together:

Steve Furber (ICL professor of computer engineering at the University of Manchester, UK), who does research on neural systems engineering;
Chaoran Huang (assistant professor at The Chinese University of Hong Kong), who works on silicon photonics, photonic integrated circuits, and nonlinear optics;
Bhavin Shastri (assistant professor at Queen’s University, Canada), who designs and builds programmable nanophotonic processors; and
Renbao Liu (professor at The Chinese University of Hong Kong), who works on quantum nonlinear spectroscopy.

Each speaker will give an overview of their research and a perspective on the future of computing, before convening for a panel discussion. Members of the audience will have the opportunity to pitch questions directly to the panel.

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Left to right: Steve Furber, Chaoran Huang, Bhavin Shastri and Renbao Liu

Steve Furber, CBE FRS FREng is ICL professor of computer engineering in the Department of Computer Science at the University of Manchester, UK. After completing a BA in mathematics and a PhD in aerodynamics at the University of Cambridge, UK, he spent the 1980s at Acorn Computers, where he was a principal designer of the BBC Microcomputer and the ARM 32-bit RISC microprocessor. More than 250 bn ARM-powered chips have since been manufactured, powering much of the world’s mobile and embedded computing. He moved to the ICL chair at Manchester in 1990, where he leads research into asynchronous and low-power systems and, more recently, neural systems engineering, where the SpiNNaker project has delivered a computer incorporating a million ARM processors optimized for brain-modelling applications.

Chaoran Huang, received a PhD from The Chinese University of Hong Kong, Hong Kong, in 2016. She was a postdoctoral research fellow at Princeton University, Princeton, NJ, USA, from 2017 to 2021. She is currently an assistant professor at the Chinese University of Hong Kong. She has broad research interests in optical computing, photonic integrated circuits, and optical communications. Her current research focuses on developing novel photonic devices, integrated circuits, and complementary algorithms for high-performance AI computing and information processing. She has published more than 50 papers, including Nature Electronics and Nature Communications. She has served as co-chair, TPC member of many international conferences, and the editorial board member of Communication Engineering in the Nature Portfolio. She was the recipient of the 2019 Rising Stars Women in Engineering Asia and the 2022 Optica 20th Anniversary Challenge Prize.

Bhavin J Shastri is an assistant professor of engineering physics at Queen’s University and a faculty affiliate at the Vector Institute. He was an associate research scholar (2016–2018) and Banting and NSERC postdoctoral fellow (2012–2016) at Princeton University. He received a PhD in electrical engineering (photonics) from McGill University in 2012. He is a co-author of the book Neuromorphic Photonics, a term he helped coin. Shastri is the recipient of a 2022 iCANX Young Scientist Award, the 2022 SPIE Early Career Achievement Award, and the 2020 IUPAP Young Scientist Prize in Optics “for his pioneering contributions to neuromorphic photonics”. He is a Senior Member of Optica and IEEE.

Renbao Liu got his BSc in 1995 from Nanjing University, Department of Physics and a PhD in 2000 from Institute of Semiconductors, Chinese Academy of Science. After postdoctoral research in Center for Advanced Study, Tsinghua University and in Department of Physics, University of California – San Diego, he joined The Chinese University of Hong Kong in 2005 as a faculty member of Department of Physics, where has been a full professor since 2014.

LAP’s RadCalc software ensures independent QA for Gamma Knife Perfexion treatment planning

Independent patient QA is hard-wired into the stereotactic radiosurgery (SRS) programme at the National Gamma Centre, part of the University Clinical Centre of Serbia in Belgrade. As such, a core building block of the daily radiosurgery workflow is LAP’s RadCalc QA secondary check software, a suite of widely deployed QA tools that provides radiation oncology teams with automated and independent dosimetric verification of their radiotherapy treatment planning systems (TPS).

Operationally, the heart of the Belgrade clinic’s SRS programme is Elekta’s Leksell Gamma Knife Perfexion treatment system (using GammaPlan TPS version 10.2.1). “Our Gamma Knife Perfexion machine provides intracranial radiosurgery to around 750 patients every year,” explains Ljubomir Kurij, the facility’s chief medical physicist. “We address a wide range of disease indications spanning benign and malignant tumours – including brain metastases, vestibular schwannoma and meningioma – as well as vascular disorders in the brain.”

For context, the Gamma Knife exploits multiple narrow beams of gamma radiation from different directions to deliver conformal, high-dose radiation to the disease target in one or a few fractions while minimizing collateral damage to surrounding healthy tissue and organs-at-risk (OARs). Despite widespread deployment in cancer centres worldwide, it’s fair to say that the precision targeting inherent to SRS remains a non-trivial dose optimization challenge for the medical physics team – and not least when it comes to focusing “high-payload” radiation onto metastatic lesions (as small as 2 mm in extent) and having it fall off as quickly as possible.

Hence the requirement for independent verification and QA of those GammaPlan treatment plans. “We needed a commercial second-check software product because developing our own in-house solution would have been too time-consuming,” explains Kurij. “To be honest, we were blown away by the functionality of the RadCalc Gamma Knife module when we road-tested the trial version last year. Training overhead is also minimal – RadCalc’s intuitive interface means it takes just a couple of hours to set up the software and get to grips with the main functionality.”

A virtual QA machine

In terms of specifics, the RadCalc Gamma Knife module includes a comprehensive machine configuration and knowledgeable technical support to guide the clinical user through installation and integration. With automated import, calculation and reporting as standard, the software computes the dose and percent difference for each target utilizing proprietary tissue-maximum-ratio (TMR) data, OAR data and source position information supplied by Elekta – in effect, providing a “virtual machine” for the dose computation (with no physics set-up necessary and automatic selection of the data based upon the type of plan). What’s more, RadCalc performs point-dose calculations for the Model 4C, Perfexion and Icon Gamma Knife treatment units using v10 or v11 variants of the GammaPlan TPS.

Ljubomir Kurij: “The RadCalc Gamma Knife module gives us that added level of reassurance versus the TPS.” (Courtesy: Nebojša Stratijev Foto Knez)

“We use the RadCalc Gamma Knife software on a daily basis to verify all of our SRS treatment plans,” explains Kurij. So far, across a cohort of well over 400 patients, Kurij and his team of three medical physicists have seen no significant discrepancy versus the primary dose calculations in Gamma Plan (more than 1.5% in only three cases).

“All the same,” he notes, “RadCalc gives us that added level of reassurance versus the TPS. Before RadCalc, we had no way of checking the GammaPlan dose calculations were correct without doing a QA measurement with a phantom – i.e. interrupting the SRS workflow and taking a hit on our patient throughput.”

That reassurance, in turn, hinges on the independence of the RadCalc Gamma Knife module and its calculation algorithm from the SRS treatment system. As such, RadCalc stores and maintains its own copy of the Elekta proprietary data, with the table look-up and interpolation process also separate from Elekta’s. In addition, external contour determination (from skull scalar-instrument measurements or threshold CT images) is fully independent as are the ray-tracing process for depth determination and the off-axis computation of the dose.

For Kurij, other notable features of RadCalc are the software’s powerful search and reporting tools – which make it straightforward to view which treatment plans have been approved by the clinician or physicist – as well as the user-friendly visualization tools. “The software has a neat visual representation of the target volume, so you can see where the beams are entering the patient’s skull,” he notes. “That’s important because if the RadCalc dose calculation deviates significantly from the GammaPlan calculation, it’s usually because the target is located in close proximity to the surface of the skull – allowing corrective measures to be taken if necessary.”

For more information about RadCalc, sign up for the webinar Experience of transit dosimetry using RadCalc EPID on 25 May, and visit LAP on booth 10 at the ESTRO Annual Congress in Vienna, Austria (12-15 May).

‘Forest of cylindrical obstacles’ slows avalanche flow

The flow rate of avalanches could be reduced by up to two-thirds by covering vulnerable slopes with trees planted every three metres. This is the conclusion of researchers in France, who used experiments and a new theoretical model of millimetre-sized grains flowing down a sloping “forest of cylindrical obstacles” to gain insights into damaging snow slides.

“Snow avalanches are a threat for humans in mountain areas with steep slopes,” explains study team leader Philippe Gondret of the FAST laboratory at Paris-Saclay University. “There is still the need for a better knowledge of these phenomena…to help develop possible protections against such a danger.”

Pillars reduce the flow in a non-trivial way

While the researchers expected that forest cover would slow the flow of avalanches to some extent, they found that the presence of pillar-like obstacles on a slope reduces the flow in a non-trivial way. “While in the absence of pillars, the average granular flow velocity increases rapidly with layer thickness, at high pillar density the granular flow rate becomes almost independent of the thickness of the granular layer,” Gondret tells Physics World.

In their experiments, the researchers created a slope from a plank 1 m long and 50 cm wide that can be inclined at well-controlled angles. Such set-ups are routinely employed to study the rheological properties of flowing granular material, but Gondret and colleagues added a twist: they covered the plank with a regularly spaced “forest” of pillars around 2 mm in diameter. These pillars mimic the presence of natural obstacles, which are known to reduce the destruction avalanches can cause. By varying the spacing between them, the researchers were able to zero in on how pillar density affects flow.

Glass beads substitute for snow

With their “forested slope” in position, the researchers were ready to simulate some avalanches. “The grains we employed are glass beads around 0.5 mm in diameter, which are just like sand grains but with a spherical shape,” explains Gondret. “We deduce the instantaneous flow rate using a scale connected to a computer that provides the weight of falling grains at the end of the plane as a function of time.”

To control the flow thickness upstream, Gondret and colleagues fine-tuned the aperture of their bead reservoir and measured the results downstream using an inclined laser sheet. They then developed a mathematical model that predicts how the presence of the pillars affects the rate of the flow and calculated the minimum density of pillars required to significantly reduce the energy the flow carries.

“Our study provides a quantitative criterion for avalanche flow reduction as a function of pillar density and slope angle,” Gondret says. “With our experimental results and from the theoretical modelling we developed, we can infer that the flow rate could be reduced by a factor of two thirds for natural avalanches through a forest with one tree every three metres.”

Applications beyond avalanches

As well as being important for snow avalanche prediction, the results could have implications for other dangerous geophysical granular flows, such as volcanic lahars and pyroclastic flows, and for the flows of materials used in industry.

The researchers now plan to study how randomly arranged pillars affect flow rates. “We also hope to characterize the effect of cohesion of the grains on the overall flow,” Gondret reveals. “These two types of experiments aim to better mimic real-life situations, such as the spatial distribution of trees in forests and the cohesive properties of snow.”

They report their work in Phys. Rev. Fluids.

Freeman Dyson: we explore the extraordinary life of the rebel physicist

In this episode of the Physics World Weekly podcast I explore the remarkable life of Freeman Dyson with the historian and physicist David Kaiser. Born in England a century ago, Dyson made important breakthroughs in quantum theory and applied mathematical rigour to a wide range of projects. These included the design of a popular research reactor still in use today and a nuclear-powered rocket, which thankfully was never built.

Kaiser is editor of the new book “Well, Doc, You’re In”: Freeman Dyson’s Journey through the Universe. This looks at the mathematical physicist’s early life, formative years, and professional life in chapters written by historians and science journalists as well as colleagues and relatives of Dyson.

In our wide-ranging conversation, we look at how Dyson’s negative experiences at English boarding schools and his frustrations while doing operational research for the Royal Air Force during the Second World War shaped his lifelong rebellious streak. We discuss how his early love of mathematics served him well when he tackled problems beyond the realm of physics. Kaiser also addresses the contrarian views on climate change that Dyson developed late in life.

IOP Publishing 2023 Quantum Science and Technology Awards webinar

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In coordination with last year’s major Quantum 2022 event, IOP Publishing announced two international awards on 14 April as part of activities to mark World Quantum Day. Judged by an international panel of experts, both awards recognize and support scientific excellence and development of researchers in quantum science and technology at the early stages of their career. The two individual winners are:

International Quantum Technology Early Career Scientist Award
Feihu Xu, University of Science and Technology China, China, for his seminal contributions to quantum communication and quantum network, including the security of practical quantum cryptography, large-scale quantum network and high-speed quantum communication.

International Quantum Technology Emerging Researcher Award
Annabelle Bohrdt, University of Regensburg, Germany, for her developing novel approaches to analyse strongly-correlated quantum matter using snapshots of quantum states.

To celebrate the achievements and contributions of the two winners, IOP Publishing will be hosting a special awards webinar to be held at 1–2.30 p.m. BST on 25 May 2023. The webinar will be chaired by Prof. Chaoyang Lu of the University of Science and Technology China (USTC) in his role as chair of the awards committee. The two prize-winning talks will be:

Secure quantum communication in a large scale – Feihu Xu
A brief tour through the Fermi-Hubbard phase diagram via snapshots – Annabelle Bohrdt

We welcome the quantum science and technology community to register and attend the live ceremony.

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Left to right: Chao-Yang Lu, Feihu Xu and Annabelle Bohrdt

Chao-Yang Lu (chair) is a professor of physics at the University of Science and Technology of China. His research interest includes quantum foundations, quantum computation, and quantum optics.

Feihu Xu has been a tenured professor of physics at USTC since 2021. Before joining USTC in 2017, he was a postdoctoral associate at MIT, 2015–2017. He received a PhD from the University of Toronto in 2015. He works mainly on quantum communication and single-photon imaging, and has co-authored more than 100 journal papers including RMP, Nature, and Nature Photonics. He is the recipient of Optica Fellow in 2022, Changjiang Scholar in 2021, Xplorer Prize in 2021, Early Career Award (by IOP–NJP) in 2020, and the Outstanding Dissertation Award (by OCPA) in 2015. He serves as the steering committee of QCrypt and an associate editor of npj Quantum Information.

Annabelle Bohrdt is a theoretical physicist aiming for a microscopic understanding of strongly correlated quantum systems by developing new analysis tools. In her research, she combines numerical methods, intuitive physical pictures, close collaboration with quantum simulation experiments, and machine learning techniques. She obtained her doctoral degree from Technical University Munich (Germany). During her PhD, Annabelle spent two years as an exchange student in the group of Eugene Demler at Harvard. From 2021 to 2023, she was an independent ITAMP postdoctoral fellow at Harvard University. Since 2023, she is a professor for theoretical physics at the University of Regensburg, Germany.

US fusion firms to be leniently regulated by nuclear watchdog

The US has announced that it will apply regulations used for particle accelerators when overseeing future commercial fusion technology – rather than implement the stricter regime currently used for nuclear fission plants. The decision was made via an unanimous vote by the five commissioners of the Nuclear Regulatory Commission (NRC) in late April. It mirrors one that the UK made last year regarding its nascent fusion industry.

The private fusion industry is booming, with 20 start-up fusion firms having been recently founded in the US alone. Given this development and the radiological issues of fusion systems, the bipartisan scientific caucuses in Congress called for the industry to be appropriately regulated by the NRC.

Some of the concerns around fusion include the significant amounts of tritium that must be carefully stored and could potentially seep into structural materials. Fusion vessels must also be shielded, owing to the radiation that the process creates.

There are also the possible health hazards from neutron bombardment and what the NRC calls “energetic plasma-surface interactions” that could generate dust containing tritium. However, fusion does not involve the heavy radioactive materials associated with commercial fission processes such as uranium, plutonium and their by-products.

A preliminary NRC white paper in January gave three options for future fusion licensing. One would take the approach currently applied to commercial fission plants, known as part 50 of the Code of Federal Regulations. A second would use the process applied for particle accelerators, known as part 30 of the code, while a third option would have been a mix of the two codes.

The white paper recommended the hybrid approach. However, the commissioners voted unanimously in April for the second, least intrusive option.

“Dozens of companies are developing pilot-scale commercial fusion designs, and while the technology’s precise future in the US is uncertain, the agency should provide as much regulatory certainty as possible given what we know today,” says NRC chairperson Christopher Hanson. “Licensing near-term fusion energy systems under a by-product material framework will protect public health and safety with a technology-neutral, scalable regulatory approach.”

Industry response

The US Fusion Industry Association welcomed the move, adding the commissioners “deserve commendation” for the decision. “Fusion energy is not nuclear fission, and therefore should not be regulated as such,” the association notes in a statement. “[The decision] affirms that principle”.

Commonwealth Fusion Systems, which was spun out of the Massachusetts Institute of Technology in 2018, says the ruling will enable the US to be a global leader in commercial fusion energy. “This regulatory framework protects workers and the public while also allowing the fusion energy industry to emerge and flourish in a comprehensive, risk-informed, flexible regulatory environment,” a spokesperson for the firm told Physics World.

To put the new regulatory framework into action, NRC staff will now start a “limited revision” to licensing regulations for materials, which will include consideration of whether the revision should create a new rule category specifically applied to fusion energy systems. Commissioners have also directed the organization’s staff to take actions such as expanding guidance for materials licences to cover fusion systems nationwide.

Meanwhile, a report by the National Academies of Sciences, Engineering, and Medicine says that new and advanced types of nuclear fission reactors could play an important role to help the US meet its long-term climate goals. Making that possible, however, will require overcoming a range of technical, regulatory, economic, and social challenges while deployment of the reactors could take several decades.

The report calls on the US Department of Energy, the NRC, other government organizations and private industry to “lay the groundwork required for advanced reactors to become a viable part of the US energy system”.

Speeded-up Brillouin microscopy sheds light on embryo development

A new microscopy technique can image the mechanical properties of developing embryos at unprecedented speed while capturing spatial details on the scale of microns. The technique, which was developed by Robert Prevedel and colleagues at the European Molecular Biology Laboratory (EMBL) in Germany, does not damage delicate biological cells or tissues and could be used in several areas of research, including biomedicine, and cell and development biology.

The new technique relies on a phenomenon known as Brillouin scattering, which occurs when light interacts with the subtle sound vibrations (phonons, or collective vibrational modes) that are present in all matter. “As the scattered light interacts with the material, the light’s energy (that is, its colour/wavelength/frequency) and bandwidth are directly related to material properties such as elasticity and viscosity,” Prevedel explains. Monitoring the properties of the scattered light thus allows researchers to determine the properties of the material that scattered it.

Such information is important because the mechanical characteristics of biological cells and tissues are closely tied to their function. The physical forces that cells experience also play a critical role in processes such as embryo and tissue development and can even dictate how diseases like cancer evolve. Measuring these properties is no easy task, however, as most techniques for doing so are invasive and thus intrinsically disruptive.

This is where Brillouin scattering could come into its own. Indeed, researchers have already used it to observe and characterize tissue mechanics in a non-invasive way. The downside is that standard Brillouin microscopy relies on analysing one point in a sample at a time. This means that imaging speeds are slow, and the long light exposure times required can damage delicate biological cells.

An entire line of light at once

To overcome these problems, Prevedel and colleagues developed an improved method that increases the speed of imaging by a factor of more than 100. “We extended [the standard] approach from measuring from a single point at a time in a sample, as is currently the case, to measuring the same properties along an entire spatial line, that is, from more than 100 points in parallel,” he explains.

The researchers used this new approach to study mechanical changes in developing embryos in three animal species – fruit flies, mice and a marine organism with the scientific name Phallusia mammillata – over periods ranging from a few hours up to two days. Writing in Nature Methods, they describe how their technique, which they dub line-scanning Brillouin microscopy, can probe the sample to its entire depth in three dimensions with high resolution. This is in stark contrast to alternative techniques, which typically only probe the surface.

“Other techniques are also invasive as they need to exert forces on the biological samples being studied to measure their material properties,” Prevedel adds. “Brillouin microscopy overcomes these limits, and with our new approach, it has now become fast and gentle enough for longitudinal studies in biology and medicine,” he tells Physics World.

The researchers suggest that line-scanning Brillouin spectroscopy could be employed in cell and development biology as well as biomedicine. Possible experiments might involve investigating the role of mechanics in morphogenesis during the development of embryos (as shown in this work) or studying the mechanics of cancer progression in artificially-grown organ-mimicking tissues known as organoids.

The EMBL team is now concentrating on improving the technique by, for example, increasing the weak interaction between the light and sound waves to generate more intense Brillouin scattering signals. “This will allow us to speed up imaging even further so that it is on a par with other (fluorescence) microscopy techniques,” Prevedel says. “We also need to measure other properties of our biological samples, such as their refractive index and material density, in three dimensions and at high resolution.”

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