This episode of the Physics World Weekly podcast features interviews with two leaders in the race to build practical quantum computers.
Michelle Simmons is director of Australia’s Centre of Excellence for Quantum Computation and Communication Technology. She talks about how her early work on fabricating solar cells kindled a passion for building electronic devices that she now pursues by leading a research group at the University of New South Wales that is building solid-state quantum computing devices at the atomic scale.
Jelena Vučković is Professor of Electrical Engineering and by courtesy, professor of Applied Physics at Stanford University. There, she leads the Nanoscale and Quantum Photonics Lab and focuses on using impurities in diamond to create quantum devices. Vučković talks about the challenges involved in creating scalable quantum computers and also reflects on the roles that engineers and physicists play in the development of quantum technologies.
The pursuit, exploration and utilization of the space environment can be misinterpreted as a luxury. History portrays space as an exclusive domain for global powers looking to demonstrate their prowess through technological marvels, or the stage for far-off exploration and scientific endeavour with little impact on daily life. However, the benefits of space are already woven into our everyday routines and provide utilities and resources on which the society has grown dependent. If these were suddenly to disappear and the world were to experience just “a day without space”, the consequences would be evident to all.
Our biggest space-based resource is the satellites we’ve put in orbit around the Earth. Communication satellites provide global connectivity and the means to transmit live television around the world. We can remotely watch international events and sporting spectacles in real time, thanks to this space-borne infrastructure. Earth observation is also of growing importance, letting us monitor and assess our natural habitat and climate, which in turn enables us to optimize agricultural land use, to predict and intervene in national disasters, to organize relief efforts, and more besides.
Position, navigation and timing (PNT) satellites provide valuable location data for drivers and outdoor enthusiasts, while their timing signals are also used to timestamp and co-ordinate global cash withdrawals and financial transactions. Satellites provide platforms for science and technology, and they can give universities access to orbital experimentation. Companies are learning to rapidly develop technology through prototypes placed in orbit, while research into space weather using in-orbit instruments provides improved understanding and forecasting to protect our Earth-bound power grids from solar storms.
The utilization of space is set to become more important still. A new vision for the future is starting to emerge that will feature even more innovative uses of space, ranging from space-based manufacturing and energy production to global Internet connectivity. Space-debris management is also receiving greater focus alongside lunar and Martian exploration, and even space tourism.
While some of these new innovations may sound like they are confined to the realm of science fiction, there are already companies furthering the technology to turn them into reality.
SABRE unleashed A concept image of Reaction Engine’s Synergetic Air Breathing Rocket Engine (SABRE). (Courtesy: Reaction Engines)
Affordable space access
One of the fundamental challenges associated with exploring and working in space is that whatever is up there, starts down here. Escaping Earth’s gravity and achieving orbit is technically difficult, operationally complex and financially exclusive.
The tide is turning, however, and the world is in the midst of a transformational era in the history of spaceflight. An activity once limited to governments and national space agencies is now witnessing a flourish of innovation led by entrepreneurial private companies such as Rocket Lab, Virgin Orbit and SpaceX, the latter of which was in the global spotlight as watched the US Commercial Crew Programme launched American astronauts to the International Space Station and then return them safely earlier this year. By optimizing conventional rocket technology, these firms are rapidly reducing the cost of space access and generating launch capacity. This in turn is creating opportunities for new space operators and is beginning to initiate a virtuous circle, in which reduced launch costs and increased flight rates create additional commercial opportunities and more demand for launch services. Indeed, the investment bank Morgan Stanley estimates that the global space market will be worth $1 trillion per year by 2040.
The global space-access industry will be limited if it remains focused on optimizing conventional rocket technology, which was first used in the mid-20th century
While this cycle could significantly reduce launch costs even further, it will be limited if the global space-access industry remains focused on optimizing conventional rocket technology, which was first used in the mid-20th century. That’s why we here at Reaction Engines in the UK (see box below) are developing the Synergetic Air Breathing Rocket Engine (SABRE) – what we think will be the next generation of space-propulsion technology. Our aim is to enable horizontally launched reusable space vehicles that are affordable, reliable and responsive, and can be launched at a high and regular frequency.
SABRE versus conventional rockets
Conventional rocket vehicles are propelled by a fuel (liquid hydrogen, kerosene or methane) and an oxidizer (liquid oxygen) carried within the vehicle body. When the fuel and oxidizer combust, mass is projected out of the back of the rocket, creating thrust. However, this approach – and especially the use of heavy on-board liquid oxygen – is constrained by Tsiolkovsky’s rocket equation. It basically tells us that everything carried on board a vehicle has a penalty in the form of the additional propellant, and structural mass of the vehicle, needed to get it off the ground. In other words, this approach hampers mission performance, mission payload and mission time.
SABRE, on the other hand, is a hybrid air-breathing rocket engine. During the atmospheric segment of its ascent, it will use oxygen from the atmosphere instead of carrying it inside the vehicle, before switching to on-board oxygen upon leaving the atmosphere. A SABRE-powered launch vehicle will therefore have lower mass for a given payload than a conventional rocket vehicle. This mass benefit can be traded for systems that will enable reusability and aircraft-like traits, such as wings, undercarriage and thermal-protection systems – all the features needed to fly the same vehicle over and over again, achieving hundreds of launches.
Reusability will not only drive down the cost of the launch. SABRE-powered launch vehicles will also take off like aircraft instead of launching vertically like conventional rocket vehicles. As a result, they will introduce faster turnaround times, higher vehicle utilization rates and more responsive launches. They will be able to undertake safe abort and return-to-base scenarios. The design of SABRE-powered launch vehicles will also allow more rapid set-up and simpler launch facilities compared with current vehicle designs.
At Reaction Engines, we think these characteristics are far beyond what we see from even the most advanced expendable systems currently available – and that they therefore will unlock the full virtuous cycle for space access and the greater potential of the space economy.
The precooler
The key element within SABRE is its unique, high-performance thermal-management system, which relies on fundamental thermodynamics to extract, redirect and utilize the enthalpy of a hypersonic (Mach 5) airstream as it enters the engine. One of the most important parts of this system is the precooler, which was therefore one of the first pieces of SABRE technology to be developed.
The speed of existing air-breathing engines is limited by their ability to handle and exploit the energy contained within high-Mach air streams. To create thrust from an air-breathing engine you have to increase the speed of the air that passes through it. Counterintuitively, you also have to slow the air down when you reach high speeds so that the internal machinery can apply work into the airflow before accelerating it from the back of the engine.
However, when fast-moving air slows down, it rapidly heats up as kinetic energy is converted into thermal energy. For example, these temperatures can reach over 1000 °C when slowing a Mach 5 air stream. At such high temperatures, it is not possible to maintain the integrity of conventional engine components – quite simply, they melt.
Quick cooling Hot airstreams can be cooled from 1000 °C to ambient temperatures within 50 ms by SABRE’s precooler. (Courtesy: Reaction Engines)
Together, SABRE’s thermal management system and the precooler provide a solution to this problem. When high-Mach air enters SABRE, it is first slowed down by the intake of the engine through a series of shockwaves created by the geometry of the engine’s components. As this happens the air rapidly heats up, but is then passed into the precooler where its temperature is reduced to manageable levels. The precooler has been designed to create heat transfer between the air stream and an internal fluid medium (cryogenic helium). Geometry, fluid properties, and thermal and mechanical effects have all been considered so as to maximize the extraction of heat from the air stream.
With the air stream suitably cooled, it can now enter the heart of the engine, where it goes through a cycle involving compression, combustion, regeneration and, ultimately, expansion through the engine’s nozzle thereby creating propulsive force. The air stream’s thermal energy, which has been transferred to the precooler fluid, is also used to drive the internal components of the engine.
The precooler can cool high mass-flow airstreams from temperatures above 1000 °C to ambient in less than 50 milliseconds, within a compact and low-weight design. It is formed from over 42 km of tubing, the walls of which are thinner than a human hair – thereby providing an enormous area for heat-transfer between the air and cooling medium.
Putting it to the test
In 2012 Reaction Engines manufactured a fully operational precooler and tested it more than 700 times, verifying the ability to take ambient air down to cryogenic temperatures. This prototype unit saw more test time than an already operational prospective SABRE precooler, and performed impeccably throughout.
Next came the Hot Heat Exchanger (HTX) test campaign, which was designed to subject the precooler to a range of high-temperature conditions representative of high-Mach flight. Carried out in 2019, the testing took place at a specially constructed facility at the Colorado Air and Space Port near Denver in the US. The test set-up featured a conventional fighter aircraft engine running on full afterburner in order to create the high-mass air flow and high-temperature conditions a SABRE precooler will experience in flight after stagnating (or slowing down) a Mach 5 airstream.
Three hot test campaigns were conducted, with each achieving a higher equivalent Mach number. The final round of tests saw both the precooler and test equipment pushed to their limits, and successfully deliver the ultimate Mach 5 test objective – it demonstrated that the precooler could quench airflow temperatures in excess of 1000 °C in less than 50 milliseconds.
The tests showed the precooler’s ability to successfully cool airflow at speeds much higher than the operational limit of any jet-engine-powered aircraft in history. It ran at over twice the operational conditions of Concorde and over one and a half times the conditions of the SR71 Blackbird. This remarkable precooler technology is, therefore, not only key to the SABRE engine but also offers propulsion solutions for high-Mach and hypersonic aircraft that remain within the atmosphere.
Testing, testing The precooler was put through a series of high-temperature tests using an engine from a conventional fighter aircraft. (Courtesy: Reaction Engines)
What comes next?
Since the successful HTX test campaign, the next phase of SABRE testing is now under way in its “core engine campaign”, which aims to validate the performance of the air-breathing core. This part of SABRE is responsible for recycling the thermal energy extracted through the precooler into the engine’s internal components. It is also where the incoming air is compressed, mixed with hydrogen fuel and then burnt within the engine’s combustion systems prior to being expanded through its nozzle. This stage will prove the viability of SABRE’s entire thermodynamic cycle and will be a landmark moment when it is demonstrated for the first time.
While the precise timings of this latest phase of the test campaign have been hit by the COVID-19 restrictions imposed in the UK, an extensive design process has already been conducted in conjunction with the UK and European space agencies, which will enable the programme to swiftly progress once the restrictions are reduced. And while the COVID-19 pandemic has undoubtedly impacted both the global aerospace sector and the operation of manufacturing and R&D facilities in the UK, there remains robust demand in the commercial space-launch sector. Reaction Engines can already see a number of possibilities where applications of SABRE-class engines might be used in launch-vehicle architectures, and we are working with partners across the space industry to understand how these capabilities can be brought to the fore.
Technology spinout
Despite being originally conceived as an engine for enabling low-cost space access, it’s now clear that SABRE technology could provide benefits beyond the space industry. That’s why Reaction Engines is also developing spin-out applications of the technology with other industry partners.
In the aerospace sector, SABRE’s thermal-management capability and heat-exchanger technology could boost the efficiency of next-generation commercial aircraft engines and systems, as well as high-Mach and hypersonic aircraft. At a time when the aerospace industry must demonstrate resilience in the face of COVID-19, technological paradigm shifts and challenging decarbonization targets, SABRE technology could help by providing a range of efficiency improvements and cost savings for current and future aircraft concepts.
Reaction Engines is investigating how SABRE technology could benefit other sectors too. Motorsport, industrial processes and the energy industry are all areas where intelligent thermal management, such as that at the heart of SABRE, could bring about significant change. Reaction Engines is keen to adapt and deploy its technology into these industries to make them more efficient, more sustainable, and better for the environment.
It is clear that the space industry is going through a period of significant innovation and rapid development. Innovative new commercial entrants have lowered the cost of space access, which has in turn opened up further commercial opportunities in space.
As the industry develops and the demand for ultra-low-cost access to space increases, we believe that there will be a need for the kind of revolutionary leap forward in propulsion that SABRE and its thermal-management systems represent.
Reaction Engines
Reaction Engines is a UK company founded in 1989 by the propulsion engineers Alan Bond, Richard Varvill and John Scott Scott. They had previously worked together on the RB545 engine, which was destined for use on the Horizontal Takeoff and Landing (HOTOL) system – a space plane concept developed by British Aerospace and Rolls-Royce – in the late 1980s. After HOTOL was cancelled, the team formed Reaction Engines to evolve the HOTOL and RB545 concepts into the SABRE engine class, which the company continues to develop.
After years of fundamental technology development, a UK government grant of £60m in 2015 – coupled with investment from BAE Systems, Rolls-Royce and Boeing HorizonX – has enabled Reaction Engines to grow and transition from research into design and demonstration. Based at the Culham Science Centre in Oxfordshire, the company is working alongside the UK Space Agency, European Space Agency and other organizations in the UK and Europe, to develop SABRE.
Climate change is a “defining factor” in the long-term prospects of businesses. So said Larry Fink – boss of leading asset-management firm Blackrock – in an open letter he wrote to chief executives around the world in January, shortly before COVID-19 hit pandemic levels. What’s interesting is that as the world emerges from lockdown and governments look to restart their economies with stimulus packages, many are taking the opportunity to attach “green strings” to their support.
The world’s greenest pandemic bailout initiative so far is the European Commission’s €750bn recovery package. Unlike many national COVID-19 support schemes, EU member states that want funds must show they will use the money in line with Europe’s Green Deal to eliminate net greenhouse-gas emissions. The UK has its own Green Recovery Programme, which seeks to drive investment in low-carbon innovation, infrastructure and industries, supporting sectors that increase job creation and decarbonization.
As governments look to restart their economies with stimulus packages, many are taking the opportunity to attach “green strings” to their support
Such programmes essentially involve providing financial support with green caveats attached, which is great news for the “clean technology” sector. However, any such clean-tech improvements will not happen overnight and may take several years to get to market. What’s more, falling profits and reduced business confidence following COVID-19 will lead to companies cutting their spending on research and development, unless appropriate support and encouragement are in place.
That’s why I was delighted to see, here in the UK, chancellor Rishi Sunak increase the Research and Development Expenditure Credit (RDEC) from 12% to 13% to help businesses invest in R&D. More significantly, the UK government is currently holding a consultation on how to refine the scheme to make it more effective at stimulating growth and investment – something that I and others on the Business Innovation and Growth (BIG) group of the Institute of Physics (IOP) have been pushing since it was set up in 2018.
The BIG group and the IOP’s policy team will be responding to the consultation by reminding the UK government how physics-based firms can take a lot longer to develop especially as scaling up prototype products and processes is risky and expensive. But, once established, such firms have a sustained competitive advantage and often export globally. They also encourage basic science, develop patents, employ talented people and boost manufacturing.
Innovation in action
Given the emphasis on green technology in the post-COVID future, I was therefore pleased that several of this year’s IOP business award winners, which I was involved in selecting, are exactly the kind of clean-tech companies we need.
They included Hirst Magnetic Instruments, a research-led company founded in 1938 that develops and makes equipment to test, measure and produce magnets. Headed by John Dudding, it focuses on the growing market for magnetic-material characterization, which is vital for improving the efficiency of motors in electric vehicles. Hirst’s materials equipment and magnetizers are supporting materials testing in China and the production lines of companies in the electric-vehicle supply chain.
Meanwhile, one company to win an IOP business start-up award this year was QLM Technology, which is developing low-power tunable-diode LIDAR gas-imaging systems based on infrared single-photon detection. Its prototypes have produced some amazing camera images that show parts-per-million levels of methane in the atmosphere measured at distances of up to 200 m. Methane is the second most important greenhouse gas – being roughly 30 times more potent at trapping heat than carbon dioxide – and there are over a million gas and oil-well pads around the world, which are leaking much more than they should.
QLM’s low cost, accurate and robust devices are exactly what’s needed for widespread emissions monitoring and meaningful regulation. Indeed, the company is already developing products for industry leaders such as Ametek, BP and the National Grid, with plans to deliver industry-ready products early next year.
Perhaps the most intriguing of the IOP’s start-up winners was FeTu, a company set up in 2016 by chief executive Jonathan Fenton, whose Fenton Turbine seems the closest we have got so far to the ideal, closed-cycle reversible heat engine first imagined by thermodynamics pioneer Nicolas Carnot in 1824. The turbine, the firm claims, could replace compressors, air conditioners, fridges, vacuum pumps and heat pumps with efficiency savings across the board.
It sounds like a “too-good-to-be-true” technology, but Fenton has sensibly set out to prove that’s not the case, with some remarkable results. The turbine is complex to describe but the first version – a “bare-shaft” unit – cuts the energy cost of compressing gases like air by 25%, with the result proven in independent tests carried out by researchers at the University of Bath. That’s promising for FeTu given that 10% of all electricity used by companies in Europe goes on compressing air – roughly 80 terawatt hours consumption per year.
As many of the IOP’s award winners illustrate, plenty of these clean-tech innovations are firmly rooted in physics
What’s more, an “open-cycle” variant of the company’s turbine can, when configured to act as a heat pump, be as efficient as air-conditioning units and refrigerators – despite using just air as the working fluid. It therefore has great environmental potential given that conventional “phase-change” refrigerants are some 2500 times more potent than carbon dioxide as greenhouse gases. FeTu says it is making good progress with customers where the energy saving and environmental advantages are clear. It is also developing a “closed-cycle” variant of the same machine with even greater efficiency improvements in store.
As many of the IOP’s award winners illustrate, plenty of these clean-tech innovations are firmly rooted in physics. I believe that research and development will be critical to ensure both economic and social recovery from the impacts of COVID-19, enabling us to build a greener, healthier and more resilient world. The IOP’s business award winners are therefore well placed to contribute to that endeavour.
Combining elemental and molecular characterization enables better and faster research in many real-world applications. Applications such as pharmaceuticals, environment, or geochemistry can benefit from this complementarity of techniques. Micro-XRF provides elemental distribution on a large area without any compromise on sample preparation, while Raman microscopy can depict molecular heterogeneity in the same conditions.
In this webinar, Thibault Brulé and Jocelyne Marciano will demonstrate how the combination of these two unique techniques can fully characterize the organic and inorganic layout over samples such as tablets, rocks or pollutant particles on filter.
Thibault Brulé is Raman application scientist at HORIBA France, working in the Demonstration Centre at the HORIBA Laboratory in Palaiseau. He is responsible for providing Raman spectroscopy applications support to key customers from various industries, as well as contributing to HORIBA’s application strategies. Prior to joining HORIBA in 2017, he conducted research on proteins in blood characterization based on dynamic surface enhanced Raman spectroscopy. He then applied this technique to cell-secretion monitoring. Thibault holds a MSc from the University of Technologies of Troyes, completed his PhD at the University of Burgundy and followed on with a postdoc fellowship at the University of Montreal.
Jocelyne Marciano is application scientist at HORIBA France, working in the Demonstration Centre at the HORIBA Laboratory in Palaiseau. She is responsible for testing and demonstrating different types of elemental analysers (EMIA-EMGA, SLFA, MESA and XGT) that are part of the HORIBA Japan product portfolio. Prior to joining HORIBA in 2008, Jocelyne spent 17 years working for Saint-Gobain as a key specialist for glass products analysis. She has in-depth experience in X-ray fluorescence and gas analysers as well as in XPS, SEM-EDX and µ-probe.
Proton-coupled electron transfer (PCET) reactions play a vital role in a wide range of electrochemical processes. This talk will focus on theoretical studies of molecular and heterogeneous electrocatalysis, highlighting the interplay between theory and experiment. A general theory of PCET that enables the calculation of rate constants, current densities, Tafel slopes, and kinetic isotope effects has been developed.
The application of this PCET theory to molecular electrocatalysts designed for water splitting illustrates the use of multi-proton relays to transport protons over hydrogen-bonded networks, as well as the ability to tune the redox potentials through substituents and other molecular design strategies.
The application of this PCET theory to proton discharge on a gold electrode provides insight into the fundamental principles underlying this process in acidic and alkaline aqueous solution as well as acetonitrile, and explains experimentally observed potential dependent kinetic isotope effects.
Recent periodic density functional theory calculations of electric fields at electrochemical interfaces and PCET at graphite-conjugated acids elucidate the impact of the applied potential on the electronic structure and interfacial fields.
The insights from these theoretical studies are useful for the design of both molecular and heterogeneous electrocatalysts to control the movement and coupling of electrons and protons for energy-conversion processes.
Sharon Hammes-Schiffer received her BA in chemistry from Princeton University in 1988 and her PhD in chemistry from Stanford University in 1993, followed by two years at AT&T Bell Laboratories. She was the Clare Boothe Luce Assistant Professor at the University of Notre Dame from 1995–2000. She then became the Eberly Professor of Biotechnology at The Pennsylvania State University until 2012, when she became the Swanlund Professor of Chemistry at the University of Illinois Urbana-Champaign. Since 2018, she has been the John Gamble Kirkwood Professor of Chemistry at Yale University.
Her research centres on the investigation of charge transfer reactions, proton-coupled electron transfer, nonadiabatic dynamics, and quantum mechanical effects in chemical, biological, and interfacial processes. Her work encompasses the development of analytical theories and computational methods and applications to experimentally relevant systems. She is a Fellow of the American Physical Society, American Chemical Society, American Association for the Advancement of Science, and the Biophysical Society. She is a member of the American Academy of Arts and Sciences, the US National Academy of Sciences, and the International Academy of Quantum Molecular Science. She has received the American Chemical Society Award in Theoretical Chemistry, the Royal Society of Chemistry Bourke Award, and the Joseph O Hirschfelder Prize in Theoretical Chemistry.
She was the deputy editor of The Journal of Physical Chemistry B and is currently the editor-in-chief of Chemical Reviews. She is on the Board of Reviewing Editors for Science and has served as Chair of the Physical Division and the Theoretical Subdivision of the American Chemical Society. She has more than 285 publications, is co-author of a textbook entitled Physical Chemistry for the Biological Sciences, and has given more than 415 invited lectures, including 24 named lectureships.
This article reports on research described in a paper in Nature. This paper has since been retracted by the journal.
Superconductivity has been observed at temperatures up to 15 °C in a hydrogen-rich material under immense pressure – shattering the previous high-temperature record by about 35 degrees. The carbonaceous sulphur hydride material was made and studied by Ranga Dias and colleagues at the University of Rochester and the University of Nevada Las Vegas in the US, who say that it may be possible to reduce the pressure required to achieve room-temperature superconductivity by changing the chemistry of the material.
Superconductors carry electrical current with no electrical resistance and have a range of applications from the high-field magnets used in MRI scanners and particle accelerators to the quantum bits used in quantum computers. Today, practical devices based on superconductors must be chilled to very cold temperatures, which is costly and can involve the use of helium – which is a limited natural resource. Therefore, a long-standing goal of condensed-matter physicists has been to develop a material that is a superconductor at room temperature.
In 2015 Mikhail Eremets and colleagues at the Max Planck Institute for Chemistry and the Johannes Gutenberg University Mainz, both in Germany, made a huge breakthrough when they observed superconductivity at 203 K (–70 °C) in a sample of hydrogen sulphide at about 1.5 million times atmospheric pressure. This new record was a huge leap forward in the quest for a room-temperature superconductor and reinforced theoretical predictions that hydrogen-rich materials could offer a way forward. Indeed, the metallic state of hydrogen – which is expected to occur at extremely high pressures and has yet to be fully characterized – is expected to be a superconductor at room temperature.
Winter’s day in Siberia
In early 2019 Eremets’ team and a group led by Russell Hemley at George Washington University in the US reported superconductivity at temperatures up to about –20 °C – a typical winter temperature across vast swathes of Russia and Canada.
Now Dias and colleagues have boosted this temperature to 15 °C, which coincidentally is the average surface temperature of the Earth. They did this by adding carbon to hydrogen sulphide – which was done by mixing methane and hydrogen sulphide together in a photochemical process. Dias told Physics World that part of his team’s success can be attributed to the precision of their synthesis technique, which is done at relatively low pressure. “[The photochemical process] is critical in introducing methane and hydrogen sulphide into the starting material, that allows just the ‘right’ amount of hydrogen needed for such remarkable properties,” he explains.
The team placed their samples in the jaws of a diamond anvil and squeezed them to pressures between about 1.4 and 2.7 million atmospheres. They found a sharp upturn in the superconducting transition temperature at about 2.2 million atmospheres with the maximum temperature of 15 °C occurring at about 2.6 million atmospheres.
Hallmarks of superconductivity
According to Dias, the team was able to make three measurements to confirm that the material is indeed a superconductor. The resistance of the sample was measured using two-probe and four-probe techniques to ensure that it was indeed zero. The researchers also measured the transition temperature as a function of applied magnetic field and found that the temperature dropped as the field increased – which is a hallmark of a superconductor. Finally, they observed that the material expelled magnetic field lines, which is another characteristic of a superconductor.
One shortcoming of the research may turn out to be an important opportunity: the team does not know the structure and exact stoichiometry (ratios of carbon, sulphur and hydrogen atoms) of the material at very high pressure. Dias says that the researchers have “some idea [of the stoichiometry] but don’t know the exact answer”. Determining the structure is difficult because the constituent atoms are too light so see using X-ray diffraction. “We have been developing a new set of tools to solve this problem,” says Dias. Once the team has a better understanding of the structure and stoichiometry they hope to be able to chemically tune the material to be a room-temperature superconductor at lower pressures.
Commenting on the significance of this latest result, Mikhail Eremets told Physics World, “We should keep in mind that truly room-temperature superconductor should be at ambient pressure, which will allow applications.” He adds that the high-pressure studies that began with his hydrogen sulphide work in 2015 provide important information in the search for an ambient-pressure room-temperature superconductor – which he says will be likely a ternary compound. Eremets also believes that this latest temperature record will not stand for long, pointing out that “there are predictions of [superconductivity] even above 400 K at high pressures”.
The French Society of Radiology (SFR) and the country’s national centre for space exploration (CNES) have signed a partnership, details of which were streamed live at the Journées Francophones de Radiologie (JFR) congress on 4 October. The aim is to develop imaging solutions to be sent on space flights and to collaborate on image collection and optimization, teleradiology and training of astronauts.
France has the largest space program in Europe and the third oldest institutional space programme in history, along with Russia and the US. CNES, which has a long track record in space exploration, recognizes the great potential of diagnostic imaging for monitoring astronauts’ health while on missions, according to general director Lionel Suchet.
The plan is to create a “two-way street” in which radiologists and space experts will collaborate on innovative projects to make further progress, JFR delegates heard online at the plenary Antoine Béclère lecture. A SFR–CNES working group will now define the research themes and establish a schedule of tasks ahead by December.
Imaging plays a vital role in monitoring astronauts’ health. (Courtesy: CNES, SFR and partners)
Shared interests
Discussing the deal, SFR president Jean-François Meder noted how the collaboration would shed light on the interest of space exploration for imaging and the role of medicine in space.
“We share the same interests: the support of innovation, and research. Today SFR and its members have needs, the first is to be able to discuss and collaborate with real professionals. Your [astronaut] teams have become true imaging professionals,” he said. “The second is the need to dream. This partnership between the SFR and the CNES will allow our radiologists to dream.”
Suchet pointed to the priority of getting crews back in good health after a mission, noting that the priority of the partnership is developing operational medicine on board the space station. The second aspect is to harness imaging in the longer term for research.
Astronauts have had to become true imaging professionals, and now the SFR will help them to carry out their own exams even better. (Courtesy: CNES, SFR and partners)
“Microgravity present in space stations makes them not only science laboratories but also tools for medical research to explore its effect on the human body,” he said.
CNES hopes that working with SFR will allow researchers to better explore health issues associated with this microgravity effect, such as cardiovascular problems, muscle loss, osteoporosis and a certain model of accelerated ageing.
For the SFR, the partnership will be a means to benefit from knowledge gained by astronauts. Discoveries from monitoring the process of accelerated ageing in astronauts, for example, could be applied to patients on Earth, helping radiologists understand the evolution of muscle mass loss, or osteoporosis, markers of patient fragility when they are exposed to cancer treatment, for example.
Beautiful adventure
In a special film broadcast during the JFR session, Claudie Haigneré (rheumatologist, astronaut and counsellor for the European Space Agency) explained how imaging can demonstrate the impact of microgravity – not only on the heart but also on other organs, such as the brain and the eyes. If such transformations can be imaged and followed, they can also be predicted.
Furthermore, after returning to Earth, astronauts undergo a complete reversal of the phenomenon, providing a platform for experimentation to better understand and treat associated symptoms. Such a model of the process of accelerated ageing and of the correction of these anomalies, would contribute to making predictive models of recuperation.
Imaging tools for future missions will be essential elements, but any progress will necessitate innovation and creativity and will also be very important for issues on Earth.
“Together we have to work and perfect the imaging tools that will accompany us. Space exploration is an international co-operative venture, whether this is with the SFR or European industrial bodies which will contribute new imaging methodology, Europe must make its voice heard … because it’s a beautiful adventure, the adventure of tomorrow,” Haigneré elaborated.
Interventional training
With the space station 400 km above the planet, communication from the ground with teleultrasound specialists in real-time is feasible. However for longer missions, communication may take from 20 to 40 minutes for information transferral. In this respect, crews will have to be even more autonomous than they are now for medical matters. Therefore the SFR has pledged as part of the partnership to contribute to astronaut training to improve diagnostics in real time. Such education will cover interpretation of radiological images, methods of image compression and training in interventional radiology.
“It seems to us that interventional radiology, and therapy, will become a major aspect, notably on long missions. Should therapy be needed, minimally invasive interventional radiology will be key,” noted JFR 2020 president Alain Luciani at the session.
Generally, astronauts are selected for their underlying good health. Only one case of venal thrombosis has ever been diagnosed via ultrasound and was treated on the space station, according to Suchet. Nevertheless diagnosis is paramount should the need arise.
Teleradiology lies at the heart of the new collaboration. (Courtesy: CNES, SFR and partners)
At present, astronauts use ultrasound for different organs including the heart and brain, and eye tomography for potential ocular problems related to microgravity. Imaging in space would need to move beyond just ultrasound, noted Luciani. Interventional radiology will need to be made compatible with a long-distance mission and safe for the astronauts and would need to be as small as possible. Telemedicine will be another convergent theme between the SFR and CNES.
Ahead to the future
In a later stage of the partnership, techniques for noise reduction from the research team at CNES could be applied to radiology, the presenters noted.
There will also be a chance for collaboration on image analysis using artificial intelligence (AI). CNES uses AI analysis of satellite images of the Earth to understand phenomena linked to climate change. Techniques based on AI algorithms and data processing to mine the useful data from the mass of information and are very similar to those needed for advanced medical image analysis, according to Suchet, pointing to this other fruitful area of collaboration, where the partners could enrich and help each other.
Media coverage of quantum computing often focuses on the long term potential for these devices to leave classical computing in the dust. But what about the rudimentary quantum systems that are already being developed and tested by technology companies? What are the latest advances in the field? And what might these systems realistically be able to achieve in the short to medium term? Andrew Glester investigates these questions in the latest episode of the Physics World Stories podcast.
The episode previews Quantum 2020, a free online event running 19–22 October hosted by IOP Publishing (which also published Physics World). Tim Smith, associate director for journals product development, describes how the conference will cover the latest developments across quantum science and technology. While Claire Webber, associate director for content and engagement marketing, explains how you can participate in the event.
Glester then catches up with one of the speakers at Quantum 2020 – Ryan Babbush, head of quantum algorithms at Google. In 2019 Google made headlines after asserting that its Sycamore quantum processor was the first to achieve “quantum supremacy”, whereby a quantum computer solves a problem in a significantly shorter time than a conventional computer. Although the specifics of that claim have been disputed, it was still celebrated as a key breakthrough in the field.
Babbush describes some of the key goals for Google’s first generation of practical quantum computers. One of them is to realize Richard Feynman’s idea of using quantum devices to simulate physical systems that behave according to the laws of quantum physics. Such a system could be used to solve the fiendishly complex chemistry equations required to predict the properties of new materials. Another key goal is quantum cryptography, which could offer secure communication systems.
At pressures of millions of atmospheres, hydrogen – normally an excellent insulator thanks to the tightly-bound electrons in the H2 molecule – becomes an electrical conductor. Its exact transition point is, however, the subject of much debate, with the results of several recent experiments seemingly contradicting each other. Researchers in Italy, Spain and France now say they have resolved the discrepancy by using an advanced computing technique that takes the quantum fluctuations of protons into account when simulating the behaviour of hydrogen at high pressures. The group’s simulations also reveal that hydrogen in this metal-like phase reflects very little light, and would thus appear pitch-black to anyone who observed it – further proof, says study lead author Lorenzo Monacelli, that metallic hydrogen is a very peculiar substance indeed.
Solid hydrogen at high pressures boasts a rich phase diagram, with five insulating molecular phases labelled I to V. The idea that it might become metallic at high pressures can be traced back to a theoretical proposal made by the Hungarian-born physicist Eugene Wigner and his American colleague Hillard Bell Huntington in 1935. Since then, metallic hydrogen has been predicted to exist in the core of gas-giant planets like Jupiter and Saturn. It has also been suggested that metallic hydrogen could be a room-temperature superconductor.
Difficult to stabilize and challenging to characterize
Such predictions are hard to confirm, however, because metallic hydrogen is extremely difficult to stabilize in the laboratory. It is also challenging to characterize, since it does not interact with X-rays and techniques that rely on neutron scattering cannot be used at high pressures. Scientists must therefore infer its structure indirectly, using vibrational spectroscopy techniques like Raman and infrared spectroscopy or optical approaches that measure light transmittance and reflectivity from a sample.
These intense experimental difficulties may well explain why different research groups have obtained apparently contradictory results about the behaviour of hydrogen at low temperatures and high pressures. Optical reflectivity measurements suggest that metallization takes place in atomic hydrogen at 495 GPa, when the element transforms from a black lower-pressure phase to a shiny higher-pressure one. Electrical conductivity measurements, meanwhile, imply that hydrogen in phase III – a molecular phase in which the strength of the hydrogen-hydrogen bonds is thought to become so weak that protons can jump between different molecules – exhibits semi-metallic behaviour at pressures above 360 GPa. Infrared light transmission experiments, for their part, suggest that phase III hydrogen becomes metallic at 420 GPa.
Not contradictory
According to researchers led by Francesco Mauri of the University Sapienza in Rome, these results are not, in fact, contradictory. The team came to this conclusion by simulating the properties of phase III hydrogen under pressures of between 150 GPa and 450 GPa. In their simulations, they used a technique called the Self-Consistent Harmonic Approximation (SCHA) to account for quantum effects on the hydrogen nuclei. Simply put, this technique simulates the wavefunction of the hydrogen nuclei (protons) by sampling their probability cloud – that is, the collection of locations where nuclei are likely to be found. The researchers then solved the electrons’ quantum equations for each configuration of nuclei.
This approach means that nuclei are not treated as static “balls” frozen in position, as is the case in most simulations. Instead, the nuclei have delocalized wavefunctions, the square of which describe the probability of where they might be located at a given time.
Based on these simulations, the researchers found that phase III hydrogen starts conducting electricity at 370 GPa – a result that Monacelli says is “in very close agreement with previous experimental findings” – while reflecting very little light even at the highest pressures. They also found that factoring in quantum effects on nuclei has a dramatic impact on hydrogen’s physical properties. This impact was expected, since the nucleus of hydrogen (the lightest element) is subject to large quantum fluctuations, but Monacelli says that the difference was still impressive.
“We found that the bond length of the H2 molecules increases by 6% (which is huge in terms of the energy involved) if quantum effects are considered,” he explains. “The [simulated] Raman and infrared spectra completely change when these effects are taken into account, with signal peaks shifting by more than 25% and their energy profile broadening a lot.” Such simulations of vibrational spectra are important, he says, because they are “the only way we can understand the crystalline structure of high-pressure hydrogen”. Encouragingly, he adds that the team’s calculated results exhibited “a remarkable agreement” with results from experimental studies of infrared absorption.
Very peculiar
Based on these results (which are detailed in Nature Physics), Monacelli says that if the data from the optical reflectivity experiments are correct, then the high measured reflectivities observed in those experiments are not consistent with hydrogen existing in a molecular phase. Instead, they imply that hydrogen is in its atomic form. “We have proven that molecular metallic hydrogen is very peculiar,” he tells Physics World. “It is conductive, black, and transparent in the infrared. This is almost unique for a metal.”
The calculations of Mauri, Monacelli and colleagues also led them to make a new prediction: deuterium – hydrogen’s heavier isotope, with a neutron as well as a proton in its nucleus – should start to conduct electricity at pressures 70 GPa higher than ordinary hydrogen. “This prediction could be confirmed in the coming months to further support or contradict our results,” Monacelli says.
A new low-cost nanogenerator that can efficiently harvest electrical energy from ambient wind has been created by Ya Yang at the Beijing Institute of Nanoenergy and Nanosystems of the Chinese Academy of Sciences and colleagues. The team reports that the device achieves high electrical conversion efficiencies for breezes of 4–8 m/s (14–28 km/h) and say that it could be used to generate electricity in everyday situations, where conventional wind turbines are not practical.
As the drive to develop renewable sources of energy intensifies, there is growing interest in harvesting ambient energy in everyday environments. From breezes along city streets, to the airflows created as we walk, the mechanical energy contained in ambient wind is abundant. The challenge is to harvest this every in an efficient and practical way. This has proven difficult using existing technologies such as piezoelectric films, which operate at very low power outputs.
Yang’s team based their new design around two well-known phenomena in physics. The first is the Bernoulli effect, which causes the fluttering of two adjacent flags to couple. If separated by a very small gap, the flags will flutter in-phase, while at slightly larger separations, they flap out-of-phase, and symmetrically about a central plane. The second is the triboelectric effect – the familiar phenomenon behind the “static electricity” that is created when different objects are rubbed together and then separated – resulting in opposite electrical charges on the objects and a voltage between the two.
Two polymer ribbons
Using two polymer ribbons; one coated with a silver electrode, and the other with the polymer FEP, Yang and colleagues combined these phenomena to create a “Bernoulli effect-dominated triboelectric nanogenerator”, or B-TENG. When subjected to a parallel airflow, the out-of-phase fluttering of the ribbons causes them to touch and separate periodically; resulting in a build-up of charge which could be used to generate an output voltage.
The researchers showed that their 3×8 cm device created usable electrical energy for wind speeds as low as 1.6 m/s, with conversion efficiencies exceeding 3.2% for speeds between 4–8 m/s. The device’s practicality was demonstrated by using it to illuminating 100 LEDs in a series circuit; integrating it into a self-powering thermometer; and using it to charge a 100 µF capacitor to 3 V in 3 min. Together, these elements were incorporated into a self-powered pressure sensor for a pipeline, using lightweight and extremely low-cost materials.
Yang’s team now hope to improve the B-TENG’s efficiency to make it even more compact – potentially enabling its integration with everyday devices. At the same time, they also hope to scale-up the device to create kilowatt-scale generators, which could compete with traditional wind turbines. If successful, the B-TENG could be used in applications ranging from wearable electronics, which can be charged by the airflow generated by walking; to clean power generation in biodiverse areas, where spinning turbines can be harmful to wildlife.
Combining elemental and molecular characterization enables better and faster research in many real-world applications. Applications such as pharmaceuticals, environment, or geochemistry can benefit from this complementarity of techniques. Micro-XRF provides elemental distribution on a large area without any compromise on sample preparation, while Raman microscopy can depict molecular heterogeneity in the same conditions.
Thibault Brulé is Raman application scientist at HORIBA France, working in the Demonstration Centre at the HORIBA Laboratory in Palaiseau. He is responsible for providing Raman spectroscopy applications support to key customers from various industries, as well as contributing to HORIBA’s application strategies. Prior to joining HORIBA in 2017, he conducted research on proteins in blood characterization based on dynamic surface enhanced Raman spectroscopy. He then applied this technique to cell-secretion monitoring. Thibault holds a MSc from the University of Technologies of Troyes, completed his PhD at the University of Burgundy and followed on with a postdoc fellowship at the University of Montreal.
Jocelyne Marciano is application scientist at HORIBA France, working in the Demonstration Centre at the HORIBA Laboratory in Palaiseau. She is responsible for testing and demonstrating different types of elemental analysers (EMIA-EMGA, SLFA, MESA and XGT) that are part of the HORIBA Japan product portfolio. Prior to joining HORIBA in 2008, Jocelyne spent 17 years working for Saint-Gobain as a key specialist for glass products analysis. She has in-depth experience in X-ray fluorescence and gas analysers as well as in XPS, SEM-EDX and µ-probe.
Sharon Hammes-Schiffer received her BA in chemistry from Princeton University in 1988 and her PhD in chemistry from Stanford University in 1993, followed by two years at AT&T Bell Laboratories. She was the Clare Boothe Luce Assistant Professor at the University of Notre Dame from 1995–2000. She then became the Eberly Professor of Biotechnology at The Pennsylvania State University until 2012, when she became the Swanlund Professor of Chemistry at the University of Illinois Urbana-Champaign. Since 2018, she has been the John Gamble Kirkwood Professor of Chemistry at Yale University.
