This time we are featuring a series of seven webinars from Oxford Instruments.
The company’s headline “guest presentation” is from Sheng Ran from the University of Maryland and the National Institute of Standards and Technology in the US, who won the 2020 Lee Osheroff Richardson science prize for North and South America. Specializing in the discovery and characterization of exotic quantum materials, Ran’s webinar is entitled “Spin-triplet superconducting state in the nearly ferromagnetic compound UTe2”. The superconducting state of UTe2 is like that in ferromagnetic superconductors, but the normal state is paramagnetic and shows no indication of magnetic ordering. Along with a very big anisotropic upper critical field, temperature independent NMR Knight shift and a large residual normal electronic density of states, these facts strongly suggest its superconductivity is carried by spin-triplet pairs.
Other presentations
In “Transport properties of low dimensional semiconductors”, Javad Shabani from New York University describes how near-surface quantum wells with strong spin-orbit coupling can be interfaced epitaxially with superconducting films and have proved as a robust platform for exploring mesoscopic and topological superconductivity. Shabani shows he used a 12T Teslatron top-loader system to study transport properties of such quantum wells, quantum Hall effect, Shubnikov de Haas mass measurements and spin orbit coupling in these 2D gas systems.
In “Conductance quantisation in one-dimensional fractional electrons”, you can hear from Sanjeev Kumar from University College London, whose group looks at quantum transport in low-dimensional semiconductor nanostructures. In the talk, Kumar present results on recently discovered zero-magnetic fractional conductance quantisation in quasi-1D electrons in GaAs/AlGaAs semiconductor heterostructures. He also shows how these non-magnetic fractional states could have applications in future quantum technologies.
The fourth webinar is from Mandar Deshmukh from the renowned Tata Institute of Fundamental Research in Mumbai, India, where he’s been a faculty member since 2006. In “Studying the flow of electrons in few-layer graphene”, Deshmukh describes his fascination with 2D materials, not just monolayer graphene but also few-layer graphene systems, which let researchers study how electrons interact in such systems. Few-layer graphene also lets you break simple symmetries and study their consequences.
Next up is Michael Hatridge from the University of Pittsburgh, where his group – the “Hatlab” – builds quantum circuits for quantum information processing and exploring fundamental physics, especially quantum measurement. In his webinar “Parametrically driven gates and loss operators in superconducting circuits”, Hartridge explains how “third-order” nonlinearities can power parametrically-driven microwave amplifiers for measuring superconducting qubits, presenting two new experiments that can control and couple transmon qubits and high-Q cavities.
In “Quantum computing and qubit scale-up applications with Proteox”, you can hear from James Robinson, a product manager at Oxford Instruments NanoScience in the UK. Robinson provides an overview of the company’s new Proteox dilution refrigerator, highlighting the key features and how it’s suitable for many quantum computing and qubit scale-up applications.
The final Oxford Instruments webinar is given by Mengqiao Sui, application manager at Oxford Instruments NanoScience in Beijing, China, who is speaking on “Cryofree magnet system for low temperature transport measurement”. In the webinar, Mengqiao discusses the measurement probes, sample protecting units and the quantum transport measurement system, which are vital for measuring electrical transport at low temperatures. As well as describing Oxford Instruments’ TeslatronPT superconducting magnet system, he also explains how the company’s Demolab in Shanghai is helping researchers and customers.
Physicists working on the LIGO gravitational-wave observatory in the US have shown that quantum-scale correlations can leave their mark on macroscopic objects weighing tens of kilograms. The team explored the interplay between the interferometer’s laser beam and its huge test masses, showing that the instrument’s quantum noise could be reduced below an intrinsic limit. This, the researchers say, could boost the future rate of discoveries with such observatories.
Gravitational waves are light-speed disturbances in space–time that are generated by massive objects accelerating somewhere in space. They can be observed by monitoring the interference between two laser beams propagating at right angles to one another, given that the waves’ passage through the Earth lengthens the path of one beam very slightly compared to the other.
The sensitivity of these instruments is limited by Heisenberg’s uncertainty principle, which stipulates a minimum combined uncertainty in an object’s position and momentum. To have sufficient sensitivity to detect the minute distance changes caused by a passing gravitational wave, an observatory’s laser beams must each bounce many times between a pair of suspended mirrors before they meet and interfere. But the photons exert pressure on the mirrors as they bounce off them, causing the mirrors to deflect and the laser path-length to change very slightly. “The light measures position yet disturbs momentum, thus imposing the Heisenberg limit,” says LIGO group member Lee McCuller of the Massachusetts Institute of Technology.
Standard quantum limit
In practice, the interferometer’s sensitivity has a minimum determined by the discrete, random nature of this and another quantum-mechanical process – the arrival time of photons at the photoelectric detector. Normally, the best that can be achieved comes as a trade-off between the uncertainty in these two quantities called the standard quantum limit. However, that limit can in theory be beaten if there is a correlation between these uncertainties, which are known as shot noise and quantum radiation pressure noise.
The latest work provides the first experimental proof that the standard quantum limit can be beaten in a gravitational-wave observatory. The research was carried out by Haocun Yu, McCuller and other members of the LIGO collaboration on one half of the LIGO observatory – a pair of 4 km-long interferometer arms located in Livingston, Louisiana.
To make their measurements, Yu and colleagues used the interferometer in two different modes. In both, the laser light was subject to ever-present vacuum fluctuations that create uncertainties in measurements of its phase and amplitude – giving rise to shot noise and radiation noise. But in the first mode those vacuum fluctuations were entirely natural, and on average the two sources of noise were equally large. In the second, in contrast, the fluctuations were manipulated so that one noise source was suppressed while the other expanded – creating a “squeezed” vacuum state.
Classical noise
Using five hours’ worth of data collected last year, the researchers plotted the variation in the uncertainty of the interferometer’s distance measurement over a range of frequencies in the output signal. To deduce the detector’s total quantum noise, they subtracted from this distribution classical noise sources – such as thermal fluctuations in the mirror coatings – which they had quantified in a reference measurement. They then compared the resulting data against model predictions.
Reporting its results in Nature, the LIGO group says that its work marks two important milestones in quantum measurement. One, it says, is having directly observed that radiation noise contributes to the motion of the interferometer’s mirrors – each of which weighs 40 kg. This, they write, indicates that an effect brought about by Heisenberg’s uncertainty principle “persists even at human scales”.
The researchers’ second key finding is having shown that when using squeezed vacuum states the resulting quantum noise does indeed drop below the standard limit at frequencies of about 30–50 Hz. This, they say, proves the existence of quantum correlations between the laser beam and the mirrors.
Room temperature result
Writing a commentary piece to accompany the paper, Valeria Sequino of the University of Naples and Mateusz Bawaj of the University of Perugia in Italy point out that the LIGO group is not the first to have reduced quantum noise below the standard limit. But they note that much previous work, which did not involve gravitational-wave observatories, required cryogenic conditions to reduce thermal noise. One impressive aspect of the latest research, they say, is the fact it was carried out at room temperature.
Sequino and Bawaj also point out that LIGO and the Virgo observatory in Italy already use squeezed vacuum states to enhance the sensitivity of their interferometers at high frequencies. But in an e-mail to Physics World, they explain that the quantum correlations introduce a “frequency dependent squeezing”. This suppresses the noise source that creates the biggest problem in a certain region of the spectrum – meaning phase noise above 100 Hz and amplitude noise below it. And they add that since this squeezing simultaneously boosts the other type of noise in each region, the uncertainty principle remains intact.
However, they stress that this improvement in broadband detection has not yet been achieved – noting that the LIGO group obtained its result by “a software subtraction of classical noise”. Reducing this noise in practice will require further work, they say.
Hubble trouble: the July 2020 issue of Physics World examines discrepancies in how fast we think the cosmos is expanding.
Europe’s Planck mission famously measured the Hubble constant to the greatest precision ever, finding it to be 67.4 km/s/Mpc, measured to an uncertainty of less than 1%.
In other words, every stretch of space a million parsecs (3.26 million light-years) wide is expanding by a further 67.4 km every second – and suggesting the universe is 13.8 billion years old.
So how come more-recent measurements of our “local universe” yield a different figure of 73.3 km/s/Mpc, with an uncertainty of 2.4% – suggesting the universe is not as old as we thought.
In the July 2020 issue of Physics World, Keith Cooper’s cover feature investigates the discrepancies and examines what the implications could be.
For the record, here’s a rundown of what else is in the issue.
• Scientists strike in racism protest – Researchers, scientific societies and publishers took part in a one-day strike last month to consider how to combat racism and discrimination in science, as Peter Gwynne and Matin Durrani report
• Growing the gravitational-wave network – David Reitze, executive director of the Laser Interferometer Gravitational-Wave Observatory, talks to Richard Blaustein about how gravitational-wave observations are set for a multi-detector boost
• The danger of going online only – Harry Collins, Bill Barnes and Riccardo Sapienza warn againsta wholesale shift to virtual workshops and conferences following the COVID-19 pandemic
• The e-bike revolution – Electric bikes are all the rage, but James McKenzie wonders if the future lies with a minimalist kit that can be retrofitted to an ordinary bicycle
• Transmogrified physics II – Robert P Crease reports on your latest work in the exciting new scientific field he discovered
• Finding a consistent constant – The Planck mission gave us the most precise value of the Hubble constant to date by measuring the cosmic microwave background. But studies made since using different methods provide different values. Keith Cooper investigates the discrepancies and asks what it might mean for cosmology
• Fighting flat-Earth theory – Physicists will find it shocking, but there are plenty of people around the world who genuinely believe the Earth is flat. Rachel Brazil explores why such views are increasingly taking hold and how the physics community should best respond
• The blue solution – Powerful blue lasers are producing the high-quality copper welds needed to make batteries for electric vehicles, as Richard Stevenson reports
• Cracking the quantum code – Kate Gardner reviews FX/BBC TV quantum-tech series Devs
• Net entanglement – Andrew Robinson reviews The System: Who Owns the Internet, and How It Owns Us by James Ball
• Training a computer to fight cancer – Medical physicist and entrepreneur Maryellen Giger talks to Margaret Harris about how she established the use of AI in breast cancer imaging
• Ask me anything – Sabine Hossenfelder from the Frankfurt Institute for Advanced Studies gives her advice to early-career physicists
Nonlinear microscopy techniques have several benefits over traditional microscopy, as they can image deeper into a sample and are able to visualize many biological features without dyes or markers. One variety of nonlinear microscopy – second-harmonic generation microscopy – is particularly good at imaging molecules that are organized into filaments, such as collagen or muscle fibres.
The team, which specializes in producing holographic images of biological samples, combined this expertise with second-harmonic generation microscopy to produce the HOT microscope.
Making a microscope
The researchers began by developing theoretical models describing how to image the sample. While creating these models, they found that using out-of-focus laser light would actually provide a unique capability for 3D imaging.
They then constructed a microscope that could use these models to image samples. Crucial for development of this microscope was a custom-built high-power laser, which was then integrated into a custom holographic microscope. To achieve the specific illumination conditions to form the required second-harmonic generation signal, the researchers used unfocused light. This also allowed a larger field of the sample to be illuminated at any one time.
The team tested the microscope on myosin fibres in skeletal muscle samples. The wide-field second-harmonic generation microscopy alone was insufficient to produce high-quality data, as the images were corrupted by out-of-focus light and appeared blurry. The HOT microscope, however, uses computational algorithms to reconstruct the image to remove the stray light and produced clear artefact-free images. The HOT reconstruction revealed the distinctive fibre structure of the myosin.
Quicker and better images
Typically, producing these types of 3D images requires a laser scanning technique that sweeps through a sample pixel-by-pixel to produce a 2D image. These images are then stacked up to produce a 3D image. The HOT microscope still collects 2D images but is not restricted to pixel-by-pixel scanning. This means that HOT is considerably faster than traditional methods. As well as saving time, this makes the technique less vulnerable to unwanted vibrations and natural drift of microscope focus.
This type of microscopy can be used to image a variety of biological features and is sensitive to orientation of fibres within the sample. This could be particularly useful to image collagen in tumours, for example, where the orientation of the fibres can indicate disease prognosis. “Most investigators look at it in 2D and not 3D,” says senior author Gabriel Popescu. “Using this technique, we can use the orientation of the collagen fibres as a reporter of how aggressive the cancer is.”
The new switch showing two gold electrodes with a layer of hBN in between. (Courtesy: UT Austin)
Two-dimensional sheets of boron nitride can be used to create an analogue switch that gives communication devices more efficient access to radio, 5G and terahertz frequencies while increasing their battery life. The switch, which was developed by a team of researchers at the University of Texas at Austin in the US and the University of Lille in France, could be employed in a host of different applications, including smartphones, mobile systems and the “Internet of things”.
Analogue switches are routinely employed in communication systems to switch from one frequency band to another, route signals between transmitting and receiving antennas, and reconfigure wireless networks. Traditionally, these switches are based on solid-state diodes or transistors, but components of this type consume energy even in standby mode, reducing the battery life of the device. With 5G networking set to drive a tenfold increase in data throughput – enabling advances in self-driving cars, delivery drones, remote surgery and fast downloads of high-definition media in the process – addressing this energy drain is more urgent than ever.
“White graphene”
A team led by Deji Akinwande of UT Austin’s Cockrell School of Engineering has now made an analogue switch from atomically thin sheets of hexagonal boron nitride (hBN). This material belongs to the same family as graphene (indeed, it is sometimes called “white graphene” for its resemblance to sheets of one-atomic-layer-thick carbon) and comprises a single layer of boron and nitrogen arranged in a honeycomb pattern. The material’s unusual electronic properties – including a large bandgap and high phonon energies – make it an excellent dielectric, and Akinwande and colleagues used it to construct a switch that is 50 times more energy-efficient than existing commercial alternatives.
The device is configured in a metal-insulator-metal sandwich on a diamond substrate, and the UT team demonstrated that it can transmit multiple HDTV streams at a frequency of 100 GHz – something unheard-of in broadband switch technology, Akinwande says. It can also switch between states in nanoseconds, remain in the “off” state when not operating (so saving battery life), and transmit data well above the baseline for 5G-level speeds.
Building on previous work
While researchers have made near-zero-power switches before, these other devices were limited to the low end of the 5G spectrum, where speeds are slower but data can travel longer distances. Akinwande and colleagues’ switch is the first to function from low-end GHz frequencies to high-end THz frequencies – something that might one day be key to developing 5G’s successor, 6G.
As well as saving battery life in smartphones, the switch could also be used in satellite systems, smart radios, reconfigurable communications, the Internet of things and defence technology, according to the researchers.
The present work, which is detailed in Nature Electronics, builds on previous work by Akinwande’s team in which they created the thinnest ever memory device from hBN. In the future, they plan to improve the reliability of their switches to millions of cycles and push the technology to work at the higher speeds required for 6G wireless applications. Akinwande has also published a blog post about the work on the Nature ResearchCommunities website.
Science writer Philip Ball joins Kate Gardner and Tushna Commissariat from Physics World to discuss the TV thriller Devs. Listen to the full conversation in the Physics World Weekly podcast.
To understand quantum physics – as far as anyone does – requires a lot of imagination, and a fair bit of philosophy. If you examine whether, say, the Many Worlds interpretation is correct, that opens up discussions of determinism versus free choice. Indeed, proving which quantum physics interpretation is true could have huge implications for humanity, and for how we live our lives. While we may not quite be there in real life, that is what the characters in new TV show Devs are attempting to unravel.
This sci-fi thriller from writer-director Alex Garland (28 Days Later, Ex-Machina) has quantum physics at its heart and truly embraces all the complexity that entails. The screen is often packed with smart people debating the nature of reality – and yet all eight episodes are also action-packed and thrilling. In the opening scene of Devs, a young couple sit in their kitchen having a conversation about quantum cryptography over breakfast. What I really appreciated was that this dialogue is neither plot explanation, nor mere technobabble. It’s establishing two scientists having a realistic technical discussion – a friendly disagreement – about their work.
The woman in this cosy set-up is Lily (played by Sonoya Mizuno), a quantum-communications expert. Her boyfriend is Sergei (Karl Glusman), an AI developer. They both work at Amaya – a quantum tech company on the outskirts of San Francisco run by its enigmatic founder Forest (Nick Offerman). Amaya is a large company with a beautiful campus – including a small woodland that disguises the location of the super-secret Devs building. Everyone at Amaya knows this department exists, but only those who work in Devs know what it does.
To reveal exactly what this clandestine department does – and how – would certainly constitute a spoiler, but the building itself is worthy of comment. From the outside it is a giant concrete bunker. Inside it is the one thing in this series that I could find fault with. A glass and steel computing lab is suspended magnetically at its centre, surrounded by a vacuum moat, several metres wide, separating it from the outer walls, floor and ceiling. The only access is via a horizontal lift that traverses the vacuum. No electronic devices – or cleaners – are allowed in, but there is somehow a fully functioning bathroom inside. I couldn’t help but wonder how exactly the plumbing functions.
Google’s Quantum AI Lab was a major inspiration in this show’s design
Nitpicking aside, this piece of futuristic architecture is built around a quantum computer – not the black box of press releases from D-Wave Systems, but a device made of tubes and copper coils resembling more than anything else an old carriage clock, with not a circuit board in sight. It’s not a million miles from press images of Google’s quantum computers – not the only time Google was a major inspiration in this show’s design.
Lily is our hero, a practical and capable woman whose life is thrown into disarray when Sergei is transferred to Devs. Through him we meet the rest of Devs team, led by the severe chief designer Katie (Alison Pill). They are all odd in their way, but these are not cardboard mockeries. The only “type” under fire here is Forest as the tech CEO, whose financial success has given him power and control over people.
Practical approach Sonoya Mizuno plays Lily, a quantum expert trying to understand her employer’s convoluted intentions. (Courtesy: BBC/FX Networks)
Mizuno, a Japanese-British ballet dancer and actor, has worked with Garland twice before (you may remember her as Kyoko, the attendant in Ex-Machina). She is utterly convincing as Lily, even while – like almost all characters in this drama – keeping the audience guessing as to what side she is on and how much of what she says is true. She is shown a little more often than is necessary in her underwear, but in that outfit, she reminded me of Ripley in Aliens, which is a strong point of reference.
Offerman is similarly an inspired choice to play Forest. He is best known for playing gruff but loveable Ron Swanson in the TV show Parks and Recreation. As Forest, there are moments of that same leadership figure: affable and brusque in a charming way, but he can turn on a pin to something much more sinister. Which makes Devs, his pet project, equally menacing.
It should come as no surprise that a project from Garland is well acted and beautifully shot, but I will say that the science component of his fiction has come a long way from the dubious physics of Sunshine, his 2007 film about reigniting the Sun, which is prematurely dying. That film boasted one Brian Cox as its scientific adviser, while Devs was developed in conversation with a whole raft of people knowledgeable about quantum – including Google’s Quantum AI Lab.
Garland and Mizuno personally visited the Google lab, and this visit – along with several others to a host of Silicon Valley companies – is evident in the set design and the way people move around it. Aside from the supremely unnerving giant statue at its centre, the architecture at Amaya is wonderful. A friend described the architecture as “realistic and tech-bro”, but I think that is misleading, because there is nothing “bro” about this series. Perhaps that’s a little idealism on Garland’s part, or perhaps that’s the Silicon Valley he saw during his research.
If you’re looking for an entertaining 360 minutes that explores cause and effect, or the true meaning of determinism, but is also an absorbing thrill ride, Devs is just the ticket.
For certain fields of physics, it can be tough to explain how the research has a direct benefit to society. That is never the case with medical physics – a career where you can apply a technical skillset to directly improve people’s everyday lives. In this episode of the Physics World Stories podcast, Andrew Glester catches up with three medical physicists from The Christie – the largest cancer hospital in Europe – to learn about their careers.
Heather Williams, the principal physicist in nuclear medicine at The Christie, speaks about some of the latest developments in positron emission tomography (PET). Williams also explains how the COVID-19 pandemic has affected the working practices at the hospital, requiring some difficult decisions around risk management. Among other developments, clinical engineers have been working with industry to develop new systems to deliver oxygen to coronavirus patients.
Later in the podcast, you will also hear from Patricia Amata who is studying for a PhD in ultrasound modalities. Medical ultrasound is most commonly associated with the field of obstetrics, where it is used to generate images of the foetus developing in the womb. But this non-ionising form of imaging is used across the medical spectrum – from breast scans to neurology, and often as a way of calibrating other imaging techniques.
Finally, clinical scientist Imran Patel speaks about the Christie’s proton therapy centre, which has been treating patients since December 2018. Patel, who leads the proton therapy physics group, explains why proton therapy can offer benefits in certain circumstances, such as paediatric cases. Unlike photons and electrons, protons beams can deliver a radiation to a highly localized sites, minimising damage to surrounding healthy tissue.
You can take a look inside the Christie’s proton therapy centre in this video produced in 2019.
Satellite operators could be doing more harm than good by shutting down their systems whenever a coronal mass ejection (CME) from the Sun is forecast to arrive at Earth, UK researchers have suggested. Mathew Owens, Mike Lockwood and Luke Barnard at the University of Reading show that the speeds and magnetic field intensities of the bursts could be just as important to consider as their arrival times when deciding when to turn satellite systems off. If applied, their ideas could significantly improve the efficiency of many satellite operations.
Originating from the Sun’s dynamic surface, CMEs are high energy bursts of plasma that travel through interplanetary space, accompanied by strong magnetic fields. When they interact with Earth’s atmosphere, they can trigger solar storms that cause severe damage to satellite systems if they are operating at the time. To predict these disruptions, astronomers measure the speed at which CMEs travel through space to make accurate forecasts of when they will arrive at Earth.
Currently, many satellite operators adopt a “better safe than sorry” approach when responding to these forecasts. Whenever a CME is predicted to arrive, they will completely shut down their systems to avoid any damage. However, the Reading trio argue that these current early warning systems do not account for a simple yet crucial fact: while all solar storms are triggered by CMEs, not all CMEs cause in damaging events.
Many false alarms
The researchers believe that this oversight is now causing many false alarms, forcing satellites to shut down when they can be operated safely. Furthermore, the cost of unneeded shutdowns could be even greater than the cost associated with solar storm damage. To improve the response to CMEs, the team suggest that alongside arrival times, it is just as important for CME forecasts to incorporate information about their speeds, and the intensities of their accompanying magnetic fields – both key indicators of solar storm severity.
Owens and colleagues tested this principle through a simple analysis of solar wind data, in which they calculated the costs of shutting down satellite systems only when CME speed and magnetic field measurements indicated that damaging weather was about to occur. Compared with more frequent shutdowns which only considered CME arrival times, they found that the resulting costs were significantly reduced.
By quantifying the costs of false alarms in this way, the team’s findings could inform more sophisticated approaches to mitigating the damage of solar storms in the future. If adopted more widely, their approach could help to streamline the efficiency of satellite operations; significantly reducing costs incurred by the many groups which rely on them.
Vocation, collaboration and innovation provide a unifying frame of reference for the physicists and engineers of Kimball Physics, a New Hampshire-based technology company that specializes in the design and manufacture of precision electron sources, electron optics and ultrahigh-vacuum (UHV) chambers and components. That frame of reference, it seems, is as solid today as it was 50 years ago, when physics professor Chuck Crawford spun Kimball Physics out from his research programme at Massachusetts Institute of Technology (MIT).
Consistency matters to Crawford, which is why the goal back then remains the mission at Kimball Physics today: “To advance humankind by doing good physics – specifically electron optics and vacuum physics – and all the while growing, being good citizens, making a living, and having fun.” Context aside, Crawford’s commercial vision was to identify an opportunity to advance the field of UHV electron and ion optics, and specifically the niche where Kimball Physics could add most value for a range of customers – from university researchers and US national laboratories to multinational “big-science” facilities and semiconductor industry OEMs.
On that canvas, Kimball Physics has carved out – and subsequently scaled – its specialist niche to encompass the design and manufacture of electron optical equipment for the semiconductor industry; electron sources for electron microscopes and electron lithography; as well as custom high-brightness sources and related technologies for free-electron lasers, particle accelerators and X-ray systems. That custom offering includes a mix of products tailored for the exacting requirements of the space industry as well as specialist Multi CF vacuum chambers for “cold physics” research and other exotic physics experiments.
Employee focus meets customer focus
Remarkably, five decades after starting the business, Crawford remains engaged with the operations at Kimball Physics. “Chuck is still in regular communication and I doubt he will ever stop thinking up new ideas,” explains Abigail LePage, a physicist and Kimball Physics’ president and chief executive officer. “He doesn’t consider what he does as work. He’s having fun and that mindset informs the collective culture here at Kimball Physics.”
That culture is further defined by “open-book management”, a non-hierarchical working model that seeks to empower all staff by treating them as partners in the business. Transparency is the key, ensuring Kimball Physics’ teams have a holistic view of the company’s financial metrics – revenue, profit, cash flow, capital expenditure and the like – so that they can make informed decisions to drive operational and strategic priorities.
That trust in the workforce yields significant gains – and not just commercially. “Many of our staff see what they do as more of a vocation,” claims David Altobelli, senior scientist at Kimball Physics. “Everybody takes a lot of pride in their work and pushing the technology forward.”
“No” is not an option for physicists when an important project must move forward. Necessity is the driver of innovation
David Altobelli, senior scientist at Kimball Physics
If vocation underpins the work ethic among Kimball Physics’ scientists and engineers, the vendor’s overarching commercial drivers are shaped by a collective focus on new product innovation and an open, inclusive dialogue with customers large and small. “Innovation at Kimball Physics is all about assimilation,” says Altobelli. “Tracking the pulse of the market requires close collaboration with scientific and industry customers to ensure that our product development aligns with their research and commercial priorities.”
Abigail LePage: “We’re proud of being an innovative and solid high-tech company.” (Courtesy: Kimball Physics)
As such, about 30% of the products that Kimball Physics ships each year are custom-made to users’ bespoke technical requirements. “We’re motivated by the challenging problems and opportunities that we see in the custom business,” Altobelli adds. “After all, today’s one-off product, for a single end-user, can evolve into tomorrow’s standard product for many.”
Unsurprisingly, Kimball Physics is active along many R&D coordinates – in each case working closely with customers. NASA is a case in point. More than 10 years ago, well before additive manufacturing became a mainstream technology, the vendor teamed up with colleagues at the US space agency to build a platform for electron-beam free-form fabrication – an innovation that may ultimately enable additive manufacturing in space. Other NASA projects involve laboratory testing and characterization of satellite shielding materials – essentially using electron and ion sources to simulate the solar wind that a craft will experience – as well as specific product innovations to minimize power consumption and footprint (e.g. delivering a 50 μA electron-beam source for satellite positioning that consumes <100 mW).
“We do take risks – within reason – and are prepared to back projects that some vendors would walk away from,” explains LePage, citing Kimball Physics’ work on the optics for novel electron sources such as superconducting quantum dots, cold electron sources and laser-excited emitters. “These more speculative plays are crucial in loading our toolbox for future product innovations,” she adds.
High-value vacuum innovation
Another promising commercial opportunity is ultrafast electron microscopy, with Kimball Physics supplying electron sources and column optics to research groups for a new generation of microscopes that offer temporal resolutions in the sub-nanosecond regime for single-shot applications (with up to 10 million electrons/pulse) and into the deep femtosecond range for stroboscopic applications (with thousands of electrons/pulse).
Elsewhere, the firm’s Multi CF UHV chambers and associated hardware – “the result of inadequately supervised physicists running amuck with CNC machines”, according to Crawford – provide a core enabling technology in cold-atom physics experiments, where accuracy of port alignment is critical for optimal laser access. A high-profile collaboration with NASA’s Cold Atom Lab, for example, has seen the Kimball Physics Multi-CF “mini” cube UHV chamber deployed on the International Space Station to support such studies. Other Multi CF applications include electron gun and ion source housings; detector housings and subsystems; as well as portable, low-cost UHV chambers.
“Our Multi CF chambers enable UHV operation with enhanced capabilities – more of a ‘value-added’ system or instrument housing than just an evacuated environment,” claims Altobelli. What he’s referring to is an array of unique Multi CF sizes and configurations, featuring precise geometries for optimized internal access, highly polished surfaces, contoured interiors and minimal welds, and annular grooves around most ports to allow mounting of internal hardware and devices. Equally, while most of the standard Multi CF chambers and fittings are made from monolithic structures of 316L stainless steel, customized options are also available in titanium for more demanding technical requirements (such as reduction of hydrogen outgassing, local magnetic effects and weight).
Looking ahead, a significant chunk of Kimball Physics’ long-range R&D effort will focus on realizing next-generation electron sources and optimized optics to address the already large (and growing) markets for electron-beam inspection, metrology and electron lithography within the semiconductor industry. “Electron emitters with precision optics are our dominant product line and key for our future product innovation,” notes LePage.
Of more immediate concern to LePage and colleagues is mapping a course through the current Covid-19 disruption, ensuring Kimball Physics continues to remain on a firm footing as it looks to the next 50 years. “We’re proud of being an innovative and solid high-tech company,” she concludes, “and we don’t intend to let the pandemic change that.”
Grain boundaries in ceramics may not be as chemically stable as previously thought. So say researchers at the University of Wisconsin-Madison in the US who have found that carbon atoms collect or segregate at the boundaries of silicon carbide – a technologically important ceramic – when the material is exposed to ionizing radiation. The result could help improve our understanding of ceramics in general and aid the development of better ceramic materials for applications in nuclear energy.
Changes in the chemical composition of grain boundaries – the interface between two different grains in a polycrystalline material – can dramatically affect a material’s mechanical strength, corrosion resistance and radiation tolerance. This is because the boundaries act as traps for defects, sites for corrosion reactions and channels for diffusing other chemicals through the material.
Radiation-induced segregation
Radiation-induced segregation is a well-known phenomenon in metal alloys. When such alloys are irradiated, the bombardment of neutrons, ions and other particles creates defects. More specifically, defects known as Frenkel pairs form when an atom leaves its place in the crystal lattice (creating a vacancy) and lodges in a nearby location (becoming an interstitial). Frenkel pairs can then either recombine with each other or migrate to defect traps such as grain boundaries. If different types of atoms in the alloy move at different rates, certain elements build up or become depleted in the vicinity of the boundaries.
Because ceramics have stronger interatomic bonds than metals, researchers had long assumed that the atoms in ceramics were not subject to this type of segregation. Now, however, a team of researchers led by Izabela Szlufarska has turned this idea on its head by studying the behaviour of grain boundaries in silicon carbide (SiC). This ceramic is employed in nuclear energy and jet engines, among other high-tech applications, and it also shows promise for advanced nuclear reactors and microelectrochemical systems operating in harsh conditions.
Szlufarska and colleagues found that the material’s grain boundaries became enriched with carbon atoms when they bombarded it with ions at a temperature of 300°C. At this temperature, which is much lower than is required to initiate radiation-induced segregation in metals, they found that the radiation dislodged some carbon atoms from their normal lattice sites. Just as in metals, the resulting pair of defects in the SiC included a vacancy site and an interstitial (in this case, a loosely-bound carbon atom). They also observed that these untethered interstitials migrated towards the grain boundaries, where they accumulated, changing the material’s chemistry. The degree of segregation diminished when they irradiated the material at 600°C.
Radiation as a tool to fine-tune chemistry
The researchers obtained their result by analysing the chemical composition of grain boundaries in pristine samples of SiC grown by chemical vapour deposition using the latest scanning transmission electron microscopy techniques at UW Madison and Oak Ridge National Laboratory. They say that the phenomenon is likely to occur in other polycrystalline ceramics, too, and they also note that the segregation might be turned into an advantage, by making it possible to produce new types of ceramic materials with improved properties. “The radiation might in fact be used as a tool to fine-tune grain boundary chemistry,” explains study co-author Xing Wang.
However, the researchers, who report their findings in Nature Materials, also note that the much lower temperatures for carbon enrichment in SiC suggest that our understanding of radiation-induced segregation in metals may not transfer directly to ceramics.
“Unlike metal alloys, ceramics have much more complex energy landscapes for defect reactions and multiple sublattices in which defects can migrate,” they say. To explore this landscape, the team developed an ab initio informed rate theory model that reproduces and explains the low-temperature radiation-induced segregation behaviour in SiC. These calculations also suggest that carbon segregation near grain boundaries in SiC comes about due to two factors: the different diffusivities of vacancies and interstitial defects; and the different reaction energy barriers between silicon and carbon sublattices in the material.
In their future studies, Szlufarska and colleagues plan to study how radiation-induced segregation in SiC depends on other conditions – for example, the total dose of radiation. They will also investigate different types of grain boundaries.
The company’s headline “guest presentation” is from Sheng Ran from the University of Maryland and the National Institute of Standards and Technology in the US, who won the 2020 Lee Osheroff Richardson science prize for North and South America. Specializing in the discovery and characterization of exotic quantum materials, Ran’s webinar is entitled “Spin-triplet superconducting state in the nearly ferromagnetic compound UTe2”. The superconducting state of UTe2 is like that in ferromagnetic superconductors, but the normal state is paramagnetic and shows no indication of magnetic ordering. Along with a very big anisotropic upper critical field, temperature independent NMR Knight shift and a large residual normal electronic density of states, these facts strongly suggest its superconductivity is carried by spin-triplet pairs.
In “Transport properties of low dimensional semiconductors”, Javad Shabani from New York University describes how near-surface quantum wells with strong spin-orbit coupling can be interfaced epitaxially with superconducting films and have proved as a robust platform for exploring mesoscopic and topological superconductivity. Shabani shows he used a 12T Teslatron top-loader system to study transport properties of such quantum wells, quantum Hall effect, Shubnikov de Haas mass measurements and spin orbit coupling in these 2D gas systems.
In “Conductance quantisation in one-dimensional fractional electrons”, you can hear from Sanjeev Kumar from University College London, whose group looks at quantum transport in low-dimensional semiconductor nanostructures. In the talk, Kumar present results on recently discovered zero-magnetic fractional conductance quantisation in quasi-1D electrons in GaAs/AlGaAs semiconductor heterostructures. He also shows how these non-magnetic fractional states could have applications in future quantum technologies.
The fourth webinar is from Mandar Deshmukh from the renowned Tata Institute of Fundamental Research in Mumbai, India, where he’s been a faculty member since 2006. In “Studying the flow of electrons in few-layer graphene”, Deshmukh describes his fascination with 2D materials, not just monolayer graphene but also few-layer graphene systems, which let researchers study how electrons interact in such systems. Few-layer graphene also lets you break simple symmetries and study their consequences.
Next up is Michael Hatridge from the University of Pittsburgh, where his group – the “Hatlab” – builds quantum circuits for quantum information processing and exploring fundamental physics, especially quantum measurement. In his webinar “Parametrically driven gates and loss operators in superconducting circuits”, Hartridge explains how “third-order” nonlinearities can power parametrically-driven microwave amplifiers for measuring superconducting qubits, presenting two new experiments that can control and couple transmon qubits and high-Q cavities.
In “Quantum computing and qubit scale-up applications with Proteox”, you can hear from James Robinson, a product manager at Oxford Instruments NanoScience in the UK. Robinson provides an overview of the company’s new Proteox dilution refrigerator, highlighting the key features and how it’s suitable for many quantum computing and qubit scale-up applications.
The final Oxford Instruments webinar is given by Mengqiao Sui, application manager at Oxford Instruments NanoScience in Beijing, China, who is speaking on “Cryofree magnet system for low temperature transport measurement”. In the webinar, Mengqiao discusses the measurement probes, sample protecting units and the quantum transport measurement system, which are vital for measuring electrical transport at low temperatures. As well as describing Oxford Instruments’ TeslatronPT superconducting magnet system, he also explains how the company’s Demolab in Shanghai is helping researchers and customers.
