The planet, the size and mass of Saturn with an orbit of thirty-five days, is among hundreds of ‘lost’ worlds that astronomers, including from the University of Cambridge, are using new techniques to track down and characterise, in the hope of finding cooler planets like those in our solar system, and even potentially habitable planets.

Reported in Astrophysical Journal Letters, the planet named NGTS-11b orbits a star 620 light-years away and is located five times closer to its sun than Earth is to our own.

The planet was originally found in a search for planets in 2018 by the University of Warwick-led team using data from NASA’s TESS telescope. This uses the transit method to spot planets, scanning for the tell-tale dip in light from the star that indicates that an object has passed between the telescope and the star.

However, TESS only scans most sections of the sky for 27 days. This means many of the longer period planets only transit once in the TESS data: without a second observation the planet is effectively lost. Researchers from Cambridge’s Cavendish Laboratory are part of the Next-Generation Transit Survey (NGTS) team which, after identifying a single transit event in the TESS data of the star NGTS-11, monitored the system in search of additional transits to confirm the planetary nature of the transiting object.

“By chasing that second transit down we’ve found a longer period planet. It’s the first of hopefully many such finds pushing to longer periods,” said lead author Dr Samuel Gill from the University of Warwick. “These discoveries are rare but important, since they allow us to find longer period planets than other astronomers are finding. Longer period planets are cooler, more like the planets in our own solar system.”

NGTS-11b has a temperature of only 160°C – cooler than Mercury or Venus. Although this is still too hot to support life as we know it, it is closer to the Goldilocks zone than many previously discovered planets which typically have temperatures above 1000°C. The Goldilocks zone refers to a range of orbits that would allow a planet or moon to support liquid water: too close to its star and it will be too hot, but too far away and it will be too cold.

“While we have discovered many planets that orbit close to their host star, we know of fewer at longer periods and cooler temperatures, which makes NGTS-11b an interesting find that takes us one step closer to finding planets in the Goldilocks zone,” said co-author Dr Ed Gillen from Cambridge’s Cavendish Laboratory. “Longer period planets like NGTS-11b may help us to better understand the various evolutionary processes that planetary systems undergo both during and after their formation.”

NGTS has twelve state-of-the-art telescopes at its site in Chile, which means that researchers can monitor multiple stars for months on end, searching for lost planets. The dip in light from NGTS-11b is only 1% deep and occurs only once every 35 days, putting it out of reach of other telescopes.

There are hundreds of single transits detected by TESS that researchers will be monitoring using this method. This will allow them to discover cooler exoplanets of all sizes, including planets more like those in our own solar system. Some of these will be small rocky planets in the Goldilocks zone that are cool enough to host liquid water oceans and potentially extra-terrestrial life.

The research was supported by the Science and Technology Facilities Council (STFC), part of UK Research and Innovation (UKRI).

Reference:
Samuel Gill et al. ‘NGTS-11 b (TOI-1847 b): A Transiting Warm Saturn Recovered from a TESS Single-transit Event.’ The Astrophysical Journal Letters (2020). DOI: 10.3847/2041-8213/ab9eb9

Adapted from a University of Warwick press release.

The researchers, from the University of Cambridge, Harvard and MIT, have shown that quantum particles can carry an unlimited amount of information about things they have interacted with. The results, reported in the journal Nature Communications, could enable far more precise measurements and power new technologies, such as super-precise microscopes and quantum computers.

Metrology is the science of estimations and measurements. If you weighed yourself this morning, you’ve done metrology. In the same way as quantum computing is expected to revolutionise the way complicated calculations are done, quantum metrology, using the strange behaviour of subatomic particles, may revolutionise the way we measure things.

We are used to dealing with probabilities that range from 0% (never happens) to 100% (always happens). To explain results from the quantum world however, the concept of probability needs to be expanded to include a so-called quasi-probability, which can be negative. This quasi-probability allows quantum concepts such as Einstein’s ‘spooky action at a distance’ and wave-particle duality to be explained in an intuitive mathematical language. For example, the probability of an atom being at a certain position and travelling with a specific speed might be a negative number, such as –5%.   

An experiment whose explanation requires negative probabilities is said to possess ‘quantum negativity.’ The scientists have now shown that this quantum negativity can help take more precise measurements.

All metrology needs probes, which can be simple scales or thermometers. In state-of-the-art metrology however, the probes are quantum particles, which can be controlled at the sub-atomic level. These quantum particles are made to interact with the thing being measured. Then the particles are analysed by a detection device.

In theory, the greater number of probing particles there are, the more information will be available to the detection device. But in practice, there is a cap on the rate at which detection devices can analyse particles. The same is true in everyday life: putting on sunglasses can filter out excess light and improve vision. But there is a limit to how much filtering can improve our vision — having sunglasses which are too dark is detrimental.

“We’ve adapted tools from standard information theory to quasi-probabilities and shown that filtering quantum particles can condense the information of a million particles into one,” said lead author Dr David Arvidsson-Shukur from Cambridge’s Cavendish Laboratory and Sarah Woodhead Fellow at Girton College. “That means that detection devices can operate at their ideal influx rate while receiving information corresponding to much higher rates. This is forbidden according to normal probability theory, but quantum negativity makes it possible.”

An experimental group at the University of Toronto has already started building technology to use these new theoretical results. Their goal is to create a quantum device that uses single-photon laser light to provide incredibly precise measurements of optical components. Such measurements are crucial for creating advanced new technologies, such as photonic quantum computers.

“Our discovery opens up exciting new ways to use fundamental quantum phenomena in real-world applications,” said Arvidsson-Shukur.

Quantum metrology can improve measurements of things including distances, angles, temperatures and magnetic fields. These more precise measurements can lead to better and faster technologies, but also better resources to probe fundamental physics and improve our understanding of the universe. For example, many technologies rely on the precise alignment of components or the ability to sense small changes in electric or magnetic fields. Higher precision in aligning mirrors can allow for more precise microscopes or telescopes, and better ways of measuring the earth’s magnetic field can lead to better navigation tools.

Quantum metrology is currently used to enhance the precision of gravitational wave detection in the Nobel Prize-winning LIGO Hanford Observatory. But for the majority of applications, quantum metrology has been overly expensive and unachievable with current technology. The newly-published results offer a cheaper way of doing quantum metrology.

“Scientists often say that ‘there is no such thing as a free lunch’, meaning that you cannot gain anything if you are unwilling to pay the computational price,” said co-author Aleksander Lasek, a PhD candidate at the Cavendish Laboratory. “However, in quantum metrology this price can be made arbitrarily low. That’s highly counterintuitive, and truly amazing!”

Dr Nicole Yunger Halpern, co-author and ITAMP Postdoctoral Fellow at Harvard University, said: “Everyday multiplication commutes: Six times seven equals seven times six. Quantum theory involves multiplication that doesn’t commute. The lack of commutation lets us improve metrology using quantum physics.

“Quantum physics enhances metrology, computation, cryptography, and more; but proving rigorously that it does is difficult. We showed that quantum physics enables us to extract more information from experiments than we could with only classical physics. The key to the proof is a quantum version of probabilities — mathematical objects that resemble probabilities but can assume negative and non-real values.”

Reference:
David R. M. Arvidsson-Shukur et al. ‘Quantum advantage in postselected metrology.’ Nature Communications (2020). DOI: 10.1038/s41467-020-17559-w

Dense metallic hydrogen – a phase of hydrogen which behaves like an electrical conductor – makes up the interior of giant planets, but it is difficult to study and poorly understood. By combining artificial intelligence and quantum mechanics, researchers have found how hydrogen becomes a metal under the extreme pressure conditions of these planets.

The researchers, from the University of Cambridge, IBM Research and EPFL, used machine learning to mimic the interactions between hydrogen atoms in order to overcome the size and timescale limitations of even the most powerful supercomputers. They found that instead of happening as a sudden, or first-order, transition, the hydrogen changes in a smooth and gradual way. The results are reported in the journal Nature.

Hydrogen, consisting of one proton and one electron, is both the simplest and the most abundant element in the Universe. It is the dominant component of the interior of the giant planets in our solar system – Jupiter, Saturn, Uranus, and Neptune – as well as exoplanets orbiting other stars.

At the surfaces of giant planets, hydrogen remains a molecular gas. Moving deeper into the interiors of giant planets however, the pressure exceeds millions of standard atmospheres. Under this extreme compression, hydrogen undergoes a phase transition: the covalent bonds inside hydrogen molecules break, and the gas becomes a metal that conducts electricity.

“The existence of metallic hydrogen was theorised a century ago, but what we haven’t known is how this process occurs, due to the difficulties in recreating the extreme pressure conditions of the interior of a giant planet in a laboratory setting, and the enormous complexities of predicting the behaviour of large hydrogen systems,” said lead author Dr Bingqing Cheng from Cambridge’s Cavendish Laboratory.

Experimentalists have attempted to investigate dense hydrogen using a diamond anvil cell, in which two diamonds apply high pressure to a confined sample. Although diamond is the hardest substance on Earth, the device will fail under extreme pressure and high temperatures, especially when in contact with hydrogen, contrary to the claim that a diamond is forever. This makes the experiments both difficult and expensive.

Theoretical studies are also challenging: although the motion of hydrogen atoms can be solved using equations based on quantum mechanics, the computational power needed to calculate the behaviour of systems with more than a few thousand atoms for longer than a few nanoseconds exceeds the capability of the world’s largest and fastest supercomputers.

It is commonly assumed that the transition of dense hydrogen is first-order, which is accompanied by abrupt changes in all physical properties. A common example of a first-order phase transition is boiling liquid water: once the liquid becomes a vapour, its appearance and behaviour completely change despite the fact that the temperature and the pressure remain the same.

In the current theoretical study, Cheng and her colleagues used machine learning to mimic the interactions between hydrogen atoms, in order to overcome limitations of direct quantum mechanical calculations.

“We reached a surprising conclusion and found evidence for a continuous molecular to atomic transition in the dense hydrogen fluid, instead of a first-order one,” said Cheng, who is also a Junior Research Fellow at Trinity College.

The transition is smooth because the associated ‘critical point’ is hidden. Critical points are ubiquitous in all phase transitions between fluids: all substances that can exist in two phases have critical points. A system with an exposed critical point, such as the one for vapour and liquid water, has clearly distinct phases. However, the dense hydrogen fluid, with the hidden critical point, can transform gradually and continuously between the molecular and the atomic phases. Furthermore, this hidden critical point also induces other unusual phenomena, including density and heat capacity maxima.

The finding about the continuous transition provides a new way of interpreting the contradicting body of experiments on dense hydrogen. It also implies a smooth transition between insulating and metallic layers in giant gas planets. The study would not be possible without combining machine learning, quantum mechanics, and statistical mechanics. Without any doubt, this approach will uncover more physical insights about hydrogen systems in the future. As the next step, the researchers aim to answer the many open questions concerning the solid phase diagram of dense hydrogen.

Reference:
Bingqing Cheng et al. ‘Evidence for supercritical behaviour of high-pressure liquid hydrogen.’ Nature (2020). DOI: 10.1038/s41586-020-2677-y.

Astronomers have speculated for decades that high clouds on Venus could offer a home for microbes – floating free of the scorching surface, but tolerating very high acidity. The detection of phosphine molecules, which consist of hydrogen and phosphorus, is an important step in the search for life beyond Earth, a key question in science. The results are reported in the journal Nature Astronomy.

The discovery was made by Professor Jane Greaves while she was a visitor at the University of Cambridge’s Institute of Astronomy. Greaves and her collaborators used the James Clerk Maxwell Telescope (JCMT) in Hawaii to detect the phosphine, and followed up their discovery on the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. Both facilities observe Venus at a wavelength of about 1 millimetre, much longer than the human eye can see.

“This was an experiment made out of pure curiosity, really – taking advantage of JCMT’s powerful technology, and thinking about future instruments,” said Greaves, who is based at Cardiff University. “I thought we’d just be able to rule out extreme scenarios, like the clouds being stuffed full of organisms. When we got the first hints of phosphine in Venus’ spectrum, it was a shock!”

Luckily, conditions were good at ALMA for follow-up observations while Venus was at a suitable angle to Earth. Processing the data was challenging, however, as ALMA isn’t usually looking for subtle effects in bright objects like Venus.

“In the end, we found that both observatories had seen the same thing – faint absorption at the right wavelength to be phosphine gas, where the molecules are backlit by the warmer clouds below,” said Greaves.

Using existing models of the Venusian atmosphere to interpret the data, the researchers found that phosphine is present but scarce – only about twenty molecules in every billion. The astronomers then ran calculations to see if the phosphine could come from natural processes on Venus. They caution that some information is lacking – in fact, the only other study of phosphorus on Venus came from one lander experiment, carried by the Soviet Vega 2 mission in 1985.

On Earth, phosphine is only made industrially or by microbes that thrive in oxygen-free environments. Co-author Dr William Bains from MIT led the work on assessing natural ways to make phosphine on Venus. Ideas included sunlight, minerals blown upwards from the surface, volcanoes, or lightning, but none of these could make anywhere near enough. Natural sources were found to make at most one ten-thousandth of the amount of phosphine that the telescopes saw.

To create the observed quantity of phosphine on Venus, terrestrial organisms would only need to work at about 10% of their maximum productivity, according to calculations by co-author Dr Paul Rimmer of Cambridge’s Department of Earth Sciences. Any microbes on Venus will likely be very different from their Earth cousins though, to survive in hyper-acidic conditions.

“This discovery brings us right to the shores of the unknown,” said Rimmer, who is also affiliated with Cambridge's Cavendish Laboratory. “Phosphine is very hard to make in the oxygen-rich, hydrogen-poor clouds of Venus and fairly easy to destroy. The presence of life is the only known explanation for the amount of phosphine inferred by observations.

“Both of these facts lie at the edge of our knowledge: the observations could be caused by an unknown molecule, or could be caused by chemistry we’re not aware of. Ultimately, the only way to find out what's really happening is to send a mission into the clouds of Venus to take a sample of the droplets and look at them to see what's inside.”

Earth bacteria can absorb phosphate minerals, add hydrogen, and ultimately expel phosphine gas. It costs them energy to do this, so why they do it is not clear. The phosphine could be just a waste product, but other scientists have suggested purposes like warding off rival bacteria.

Co-author Dr Clara Sousa Silva from MIT was also thinking about searching for phosphine as a ‘biosignature’ gas of non-oxygen-using life on planets around other stars because normal chemistry makes so little of it. “Finding phosphine on Venus was an unexpected bonus,” she said. “The discovery raises many questions, such as how any organisms could survive. On Earth, some microbes can cope with up to about 5% acid in their environment – but the clouds of Venus are almost entirely made of acid.”

Other possible biosignatures in the Solar System may exist, like methane on Mars and water venting from the icy moons Europa and Enceladus. On Venus, it has been suggested that dark streaks where ultraviolet light is absorbed could come from colonies of microbes. The Akatsuki spacecraft, launched by the Japanese space agency JAXA, is currently mapping these dark streaks to understand more about this unknown ultraviolet absorber.

The team believes their discovery is significant because they can rule out many alternative ways to make phosphine, but they acknowledge that confirming the presence of ‘life’ needs a lot more work. Although the high clouds of Venus have temperatures up to a pleasant 30 degrees Celsius, they are incredibly acidic – around 90% sulphuric acid – posing major issues for microbes to survive there. The researchers are investigating the possibility that the microbes could shield themselves inside droplets.

The team is now awaiting more telescope time to establish whether the phosphine is in a relatively temperate part of the clouds and to look for other gases associated with life. New space missions could also travel to our neighbouring planet, and sample the clouds to search for signs of life.

Professor Emma Bunce, President of the Royal Astronomical Society, said: “A key question in science is whether life exists beyond Earth, and the discovery by Professor Jane Greaves and her team is a key step forward in that quest. I’m particularly delighted to see UK scientists leading such an important breakthrough – something that makes a strong case for a return space mission to Venus.”

Reference:
Jane S. Greaves et al. ‘Phosphine Gas in the Cloud Decks of Venus.’ Nature Astronomy (2020). DOI: 10.1038/s41550-020-1174-4

Adapted from an RAS press release.

The planet orbits so close to its star that its year lasts only 19 hours, and stellar radiation heats the planet to over 1700 degrees Celsius.

At these temperatures, heavy elements like iron can be ionised in the atmosphere and molecules disassociated, providing a unique laboratory to study the chemistry of planets outside the solar system.

Although the planet weighs twice as much as Neptune, it is also slightly larger and has a similar density. Therefore, LTT 9779b should have a huge core of around 28 Earth masses, and an atmosphere that makes up around 9% of the total planetary mass.

The system itself is around two billion years old, and given the intense irradiation, a Neptune-like planet would not be expected to keep its atmosphere for so long, providing a puzzle for astronomers to solve; how such an improbable system came to be. The results are reported in the journal Nature Astronomy.

LTT 9779 is a Sun-like star located at a distance of 260 light years, a stone’s throw in astronomical terms. It is metal-rich, having twice the amount of iron in its atmosphere than the Sun. This could be a key indicator that the planet was originally a much larger gas giant, since these bodies tend to form close to stars with the highest iron abundances.

Initial indications of the existence of the planet were made using the Transiting Exoplanet Survey Satellite (TESS), as part of its mission to discover small transiting planets orbiting nearby and bright stars across the whole sky. Such transits are found when a planet passes directly in front of its parent star, blocking some of the starlight, and the amount of light blocked reveals the companion’s size. Planets like these, once fully confirmed, can allow astronomers to investigate their atmospheres, providing a deeper understanding of planet formation and evolution processes.

The transit signal was confirmed in early November 2018 as originating from a planetary mass body, using observations taken at the ESO la Silla Observatory in northern Chile. HARPS uses the Doppler Wobble method to measure planet masses and orbital characteristics. When objects are found to transit, Doppler measurements can be organized to confirm the planetary nature in an efficient manner. In the case of LTT 9779b, the team were able to confirm the planet’s existence after only one week of observations.

Professor James Jenkins from the Department of Astronomy at the Universidad de Chile, who led the team, said: “The discovery of LTT 9779b so early in the TESS mission was a complete surprise; a gamble that paid off. The majority of transit events with periods less than one day turnout to be false-positives, normally background eclipsing binary stars.”  

The planet was uncovered in only the second of 26 sectors of observations that TESS would be observing across the whole sky. Since no similar types of planets were detected in the TESS precursor missions Kepler and K2, the finding was even more exciting.

“We selected this candidate from a TESS alert due to its very short orbital period. After inspecting the light curve, we found it was a good candidate for an upcoming week-long observation campaign using the HARPS spectrograph in La Silla,” said co-author Matías Díaz, also from the Universidad de Chile. “We planned the observations carefully, to maximize the use of the spectrograph and sample the orbit of the candidate in an optimal way. During the first nights of data we saw the observations matched the predicted period of the candidate. Further analysis of the seven nights of observations in November were consistent with a massive Neptune planet.”

LTT 9779b exists in the ‘Neptunian Desert’, a region devoid of planets when we look at the population of planetary masses and sizes. Although icy giants seem to be a fairly common by-product of the planet formation process, this is not the case very close to their stars. The researchers believe these planets get stripped of their atmospheres over cosmic time, ending up as so-called Ultra Short Period planets.

The Kepler mission found that Ultra Short Period planets, those that orbit their stars in one day or less, come mainly in the form of large gas giants or small rocky planets. Models tell us that planets like LTT 9779b should be stripped of their atmospheres through a process called photoevaporation as they move close to their stars. The large gas giants, on the other hand, have strong gravitational fields that can hold onto their atmospheres, and so we end up with a dearth of planets like Neptune with the shortest orbital periods.

“Planetary structure models tell us that the planet is a giant core dominated world, but crucially, there should exist two to three Earth-masses of atmospheric gas,” said Jenkins. “But if the star is so old, why does any atmosphere exist at all? Well, if LTT 9779b started life as a gas giant, then a process called Roche Lobe Overflow could have transferred significant amounts of the atmospheric gas onto the star.”

Roche Lobe Overflow is a process whereby a planet comes so close to its star that the star’s stronger gravity can capture the outer layers of the planet, causing it to transfer onto the star and so significantly decreasing the mass of the planet. Models predict outcomes similar to that of the LTT 9779 system, but they also require some fine-tuning.

“It could also be that LTT 9779b arrived at its current orbit quite late in the day, and so hasn’t had time to be stripped of the atmosphere. Collisions with other planets in the system could have thrown it inwards towards the star. Indeed, since it is such a unique and rare world, more exotic scenarios may be plausible,” said Jenkins.

Members of the Cambridge Astronomy department are part of the Next-Generation Transit Survey (NGTS). The NGTS team conducted follow-up observations of LT9779b’s transit to help confirm the planetary nature of the system and better constrain its properties.

“LTT 9779b is an intriguing planet, being the first of its kind discovered,” said co-author Dr Ed Gillen, from Cambridge’s Cavendish Laboratory. “It is particularly exciting because of its peculiarity: how did this planet come to arrive on such a short period orbit and why does it still possess an atmosphere? Fortunately, the planetary system is located nearby so we can study it in detail, which promises new insights into how such planets come to be and what they are made of.”

Reference:
James S. Jenkins et al. ‘An ultrahot Neptune in the Neptune desert.’ Nature Astronomy (2020). DOI: 10.1038/s41550-020-1142-z

Adapted from a Universidad de Chile press release.

The researchers, led by the University of Edinburgh, with colleagues from Cambridge, London, Slovenia and China, used a combination of theoretical and experimental methods to develop a strategy to detect the DNA of infectious diseases. The results are reported in the Proceedings of the National Academy of Sciences.

The current coronavirus pandemic highlights the need for fast and accurate detection of infectious diseases. Importantly, viral infections like coronavirus and bacterial infections like those associated with antimicrobial resistance (AMR) need to be distinguished. This is usually done by using a complementary sequence that binds selectively to the genome of interest. Normally, this is done by targeting a single, long DNA sequence that is unique to the pathogen.

However, the researchers believe that much higher selectivities can be achieved by simultaneously targeting many shorter sequences that occur with a higher frequency in the pathogen of interest than in the DNA of other organisms that may be present in the patient samples.

"This approach exploits a phenomenon called ‘multivalency’, and the extensive numerical calculations, based on real bacterial and viral DNA sequences show that this approach should significantly outperform current approaches," said co-author Professor Erika Eiser from Cambridge’s Cavendish Laboratory. "Even though the individual shorter sequences bind more weakly to the target DNA than a single, longer sequences, the strength of the multivalent binding increases much faster than linearly with the number of short sequences."

In other words, instead of designing molecular probes that bind strongly to one place on the target DNA, researchers should, counterintuitively, design probes that bind weakly all over the target DNA. Making such relatively short probe sequences is, at present, a standard procedure and the sequences can be ordered online.

The experimental part of the project started with experiments in Cambridge, showing that the method can work in principle on a mixture of viral DNA and colloids coated with short complementary strands. Then the simulations took over to predict what combination of probe sequences would give the highest selectivity.

This part of the project has so far only been tested in computer models. The next step is to carry out experiments on real mixtures of viral and bacterial DNA.

"Experiments are needed to test how well this works in practice – but it is exciting work, given the urgent need for fast, reliable disease detection methods, especially those that can be applied in countries with a weak health infrastructure," said Professor Rosalind Allen from the University of Edinburgh, who led the research.

This work was performed before the COVID-19 pandemic. However, the current emergency illustrates the need for robust and highly selective methods to quickly identify specific viruses – particularly in ‘low-tech’ environments.

The research was funded in part by the Royal Society and the European Research Council.

Reference:
Tine Curk et al. ‘Computational design of probes to detect bacterial genomes by multivalent binding.’ PNAS (2020). DOI: 10.1073/pnas.1918274117

Adapted from a University of Edinburgh press release.

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One hundred and eighty-five senior scientists from across Europe were awarded grants in today’s announcement, representing a total of €450 million in research funding. The UK has 34 grantees in this year’s funding round, the second-most of any ERC participating country.

ERC grants are awarded through open competition to projects headed by starting and established researchers, irrespective of their origins, who are working or moving to work in Europe. The sole criterion for selection is scientific excellence.

ERC Advanced Grants are designed to support excellent scientists in any field with a recognised track record of research achievements in the last ten years.

Professors Mete Atatüre and Jeremy Baumberg, both based at Cambridge’s Cavendish Laboratory, work on diverse ways to create new and strange interactions of light with matter that is built from tiny nano-sized building blocks.

Baumberg’s PICOFORCE project traps light down to the size of individual atoms which will allow him to invent new ways of tugging them, levitating them, and putting them together. Such work uncovers the mysteries of how molecules and metals interact, crucial for creating energy sustainably, storing it, and developing electronics that can switch with thousands of times less power need than currently.

"This funding recognises the huge need for fundamental science to advance our knowledge of the world – only the most imaginative and game-changing science gets such funding," said Baumberg.

Atatüre’s project, PEDESTAL, investigates diamond as a material platform for quantum networks. What gives gems their colour also turns out to be interesting candidates for quantum computing and communication technologies. By developing large-scale diamond-semiconductor hybrid quantum devices, the project aims to demonstrate high-rate and high-fidelity remote entanglement generation, a building block for a quantum internet.

"The impact of ERC funding on my group’s research had been incredible in the last 12 years, through Starting and Consolidator grants. I am very happy that with this new grant we as UK scientists can continue to play an important part in the vibrant research culture of Europe," said Atatüre.

Professor Judith Driscoll from Cambridge’s Department of Materials Science & Metallurgy was also awarded ERC funding for her work on nanostructured electronic materials. She is also spearheading joint work of her team, as well as those of Baumberg and Atatüre, on low-energy IT devices.

"My approach uses a different way of designing and creating oxide nano-scale film structures with different materials to both create new electronic device functions as well as much more reliable and uniform existing functions," she said. "Cambridge is a fantastic place that enables all our approaches to come together, driven by cohorts of inspirational young researchers in our UK-funded Centre for Doctoral Training in Nanoscience and Nanotechnology – the NanoDTC."

Professor John Robb from Cambridge’s Department of Archaeology was awarded an ERC grant for the ANCESTORS project on the politics of death in prehistoric Europe. The project takes the methods developed in the ‘After the Plague’ project and the taphonomy methods developed in the Scaloria Cave project and apply them to a major theoretical problem in European prehistory - the nature of community and the rise of inequality.

"This project is really exciting and I’ll be working with wonderful colleagues Dr Christiana ‘Freddi’ Scheib at the University of Tartu and Dr Mary Anne Tafuri at Sapienza University of Rome," said Robb. "The results will allow us to evaluate for the first time how inequality affected lives in prehistoric Europe and what role ancestors played in it."

Magnets often harbour hidden beauty. Take a simple fridge magnet: somewhat counterintuitively, it is ‘sticky’ on one side but not the other. The secret lies in the way the magnetisation is arranged in a well-defined pattern within the material. More intricate magnetisation textures are at the heart of many modern technologies, such as hard drives.

Now, an international team of scientists from the University of Cambridge, the Paul Scherrer Institute (PSI), ETH Zurich, the Donetsk Institute for Physics and Engineering in Ukraine and the Institute for Numerical Mathematics RAS in Moscow have discovered unexpected magnetic structures inside a tiny pillar made of the magnetic material GdCo₂.

The researchers observed sub-micrometre loop-shaped configurations, which they identified as magnetic vortex rings. Far beyond their aesthetic appeal, these textures might point the way to further complex three-dimensional structures arising in the bulk of magnets and could one day form the basis for new technological applications. Their results are reported in the journal Nature Physics.

Determining the magnetisation arrangement within a magnet is highly challenging, in particular for structures at the micro- and nanoscale, for which studies have been typically limited to looking at a shallow layer just below the surface. That changed in 2017 when researchers at PSI and ETH Zurich introduced a new X‑ray method for the nanotomography of bulk magnets, which they demonstrated in experiments at the Swiss Light Source. That advance opened up a window into the inner life of magnets, providing a tool for determining three-dimensional magnetic configurations at the nanoscale within micrometre-sized samples.

Using these capabilities, the researchers ventured into new territory. The stunning loop shapes they observed appear in the same GdCo₂ micropillar samples in which they had before detected complex magnetic configurations consisting of vortices — the sort of structures seen when water spirals down from a sink — and their topological counterparts, antivortices.

That was a first, but the presence of these textures has not been surprising in itself. Unexpectedly, however, the scientists also found loops that consist of pairs of vortices and antivortices. That observation proved to be puzzling. With the implementation of novel sophisticated data-analysis techniques they eventually established that these structures are so-called vortex rings — in essence, doughnut-shaped vortices.

Vortex rings are familiar to everyone who has seen smoke rings being blown, or who has watched dolphins producing loop-shaped air bubbles, for their own amusement as much as to that of their audience. The newly discovered magnetic vortex rings are captivating in their own right. Not only does their observation verify predictions made some two decades ago, settling the question whether such structures can exist. They also offered surprises. In particular, magnetic vortex rings have been predicted to be a transient phenomenon, but in the experiments now reported, these structures turned out to be remarkably stable.

“One of the main puzzles was why these structures are so unexpectedly stable – like smoke rings, they are only supposed to exist as moving objects,” said Dr Claire Donnelly from Cambridge’s Cavendish Laboratory, and the paper’s first author. “Through a combination of analytical calculations and considerations of the data, we determined the root of their stability to be the magnetostatic interaction.”

The stability of magnetic vortex rings could have important practical implications. For one, they could potentially move through magnetic materials, as smoke rings move stably though air, or air-bubble rings through water.

Learning how to control the rings within the volume of the magnet can open interesting prospects for energy-efficient 3D data storage and processing. There is interest in the physics of these new structures, too, as magnetic vortex rings can take forms not possible for their smoke and air counterparts. The team has already observed some unique configurations, and going forward, their further exploration promises to bring to light yet more magnetic beauty.

Reference:
Claire Donnelly et al. ‘Experimental observation of vortex rings in a bulk magnet.’ Nature Physics (2020). DOI: 10.1038/s41567-020-01057-3

Adapted from a PSI press release.

The researchers, from the University of Cambridge, have shown that microscopic particles can remain intrinsically linked, or entangled, over long distances even if there are random disruptions between them. Using the mathematics of quantum theory, they discovered a simple setup where entangled particles can be prepared and stabilised even in the presence of noise by taking advantage of a previously unknown symmetry in quantum systems.

Their results, reported in the journal Physical Review Letters, open a new window into the mysterious quantum world that could revolutionise future technology by preserving quantum effects in noisy environments, which is the single biggest hurdle for developing such technology. Harnessing this capability will be at the heart of ultrafast quantum computers.

Quantum systems are built on the peculiar behaviour of particles at the atomic level and could revolutionise the way that complex calculations are performed. While a normal computer bit is an electrical switch that can be set to either one or zero, a quantum bit, or qubit, can be set to one, zero, or both at the same time. Furthermore, when two qubits are entangled, an operation on one immediately affects the other, no matter how far apart they are. This dual state is what gives a quantum computer its power. A computer built with entangled qubits instead of normal bits could perform calculations well beyond the capacities of even the most powerful supercomputers.

“However, qubits are extremely finicky things, and the tiniest bit of noise in their environment can cause their entanglement to break,” said Dr Shovan Dutta from Cambridge’s Cavendish Laboratory, the paper’s first author. “Until we can find a way to make quantum systems more robust, their real-world applications will be limited.”

Several companies – most notably, IBM and Google – have developed working quantum computers, although so far these have been limited to less than 100 qubits. They require near-total isolation from noise, and even then, have very short lifetimes of a few microseconds. Both companies have plans to develop 1000 qubit quantum computers within the next few years, although unless the stability issues are overcome, quantum computers will not reach practical use.

Now, Dutta and his co-author Professor Nigel Cooper have discovered a robust quantum system where multiple pairs of qubits remain entangled even with a lot of noise.

They modelled an atomic system in a lattice formation, where atoms strongly interact with each other, hopping from one site of the lattice to another. The authors found if noise were added in the middle of the lattice, it didn’t affect entangled particles between left and right sides. This surprising feature results from a special type of symmetry that conserves the number of such entangled pairs.

“We weren’t expecting this stabilised type of entanglement at all,” said Dutta. “We stumbled upon this hidden symmetry, which is very rare in these noisy systems.”

They showed this hidden symmetry protects the entangled pairs and allows their number to be controlled from zero to a large maximum value. Similar conclusions can be applied to a broad class of physical systems and can be realised with already existing ingredients in experimental platforms, paving the way to controllable entanglement in a noisy environment.

“Uncontrolled environmental disturbances are bad for survival of quantum effects like entanglement, but one can learn a lot by deliberately engineering specific types of disturbances and seeing how the particles respond,” said Dutta. “We’ve shown that a simple form of disturbance can actually produce – and preserve – many entangled pairs, which is a great incentive for experimental developments in this field.”

The researchers are hoping to confirm their theoretical findings with experiments within the next year.

The research was funded in part by the Engineering and Physical Sciences Research Council (EPSRC).

Reference:
Shovan Dutta and Nigel R. Cooper. ‘Long-range coherence and multiple steady states in a lossy qubit array.’ Physical Review Letters (2020). DOI: 10.1103/PhysRevLett.125.240404

Professor Simon Baron-Cohen, Director of Cambridge’s Autism Research Centre and a Fellow of Trinity College, has been knighted for services to autism research and autistic people. He is one of the top autism researchers in the world, and is a Fellow of the British Academy, the Academy of Medical Sciences, and the British Psychological Society. He served as Chair of the NICE Guidelines for autism and is Director of the charity the Autism Centre of Excellence and Vice President of the National Autistic Society. He was President of the International Society for Autism Research. He created the first clinic worldwide to diagnose autism in adults and championed the human rights of autistic people at the UN. He is author of The Essential Difference, Zero Degrees of Empathy, and The Pattern Seekers, which have captured the public imagination.

Professor Baron-Cohen said: “This honour came as a complete surprise, and I accept it on behalf of the talented team of scientists at the Autism Research Centre in Cambridge, and on behalf of the Autism Research Trust, the charity that has supported us. The basic needs and human rights of autistic people and their families are still not being met by statutory services, due to insufficient funding, so we are creating a new charity, the Autism Centre of Excellence, to address this gap.”

Professor Usha Goswami, Director for the Centre for Neuroscience in Education, Professor of Cognitive Developmental Neuroscience and Fellow of St. John’s College, becomes CBE for services to educational research.

Her research focuses on children’s cognitive development, particularly the development of language and literacy. Her world-leading work on dyslexia led to the discovery that children with the disorder hear language differently, showing it to be a language disorder and not a visual disorder as previously thought. This significant finding is enabling the development of transformative new educational interventions, which will benefit millions of children with dyslexia worldwide.

“I am deeply honoured to receive this award,” said Professor Goswami. “I have been interested in children’s development since training as a primary school teacher and it is wonderful to have my research recognised in this way.

Professor Val Gibson, Professor of High Energy Physics at the Cavendish Laboratory, University Gender Equality Champion and Fellow of Trinity College, has been made OBE for service to Science, Women in Science and Public Engagement.

Her research interest is the search for new phenomena using particles containing heavy quarks, which are produced in copious amounts at the Large Hadron Collider, and hold the key to our understanding of the matter-antimatter imbalance in the Universe. From 2004-2008, she was the UK Spokesperson and PI for the LHCb experiment and had ultimate responsibility to deliver the UK contributions to the experiment. She is currently the Chair of the LHCb Collaboration Board, the decision-making body for the experiment, with representatives from 78 institutes across the world.

Professor Gibson said: “It is an honour to be recognised for all three of my passions: research into the most fundamental particles and forces of nature, including the mystery of why we live in a Universe made of matter and not antimatter; support for gender equality and diversity in science; and the public engagement activities I have undertaken over many years.”

Dr Michael Weekes from the Cambridge Institute for Therapeutic Immunology and Infectious Disease (CITIID) has been awarded the British Empire Medal for or services to the NHS during COVID-19. He developed a comprehensive COVID-19 screening programme for Cambridge University Hospitals healthcare workers, Cambridge University staff and students.

Dr Weekes said: "I’m deeply honoured to have had the chance to be part of the team that set up COVID testing for Cambridge University Hospitals. I’d particularly like to acknowledge the contribution of Steve Baker, Rob Howes and Giles Wright, who played vital roles in testing and organisation. I hope that vaccination will soon mean that hospitals become even safer places to work and be cared for."

UK Research and Innovation (UKRI) is supporting seven projects with a £31 million investment to demonstrate how quantum technologies could solve some of the greatest mysteries in fundamental physics. Researchers from the University of Cambridge have been awarded funding on four of the seven projects.

Just as quantum computing promises to revolutionise traditional computing, technologies such as quantum sensors have the potential to radically change our approach to understanding our universe.

The projects are supported through the Quantum Technologies for Fundamental Physics programme, delivered by the Science and Technology Facilities Council (STFC) and the Engineering and Physical Sciences Research Council (EPSRC) as part of UKRI’s Strategic Priorities Fund. The programme is part of the National Quantum Technologies Programme.

AION: A UK Atom Interferometer Observatory and Network has been awarded £7.2 million in funding and will be led by Imperial College London. The project will develop and use technology based on quantum interference between atoms to detect ultra-light dark matter and sources of gravitational waves, such as collisions between massive black holes far away in the universe and violent processes in the very early universe. The team will design a 10m atom interferometer, preparing the construction of the instrument in Oxford and paving the way for larger-scale future experiments to be located in the UK. Members of the AION consortium will also contribute to MAGIS, a partner experiment in the US.

The Cambridge team on AION is led by Professor Valerie Gibson and Dr Ulrich Schneider from the Cavendish Laboratory, alongside researchers from the Kavli Institute for Cosmology, the Institute of Astronomy and the Department of Applied Mathematics and Theoretical Physics. Dr Tiffany Harte will co-lead the development of the cold atom transport and final cooling sequences for AION, and Dr Jeremy Mitchell will co-lead the data readout and network capabilities for AION and MAGIS, and undertake data analysis and theoretical interpretation.

“This announcement from STFC to fund the AION project, which alongside some seed funding from the Kavli Foundation, will allow us to target key open questions in fundamental physics and bring new interdisciplinary research to the University for the foreseeable future,” said Gibson.

“Every physical effect, known or unknown, leaves its fingerprint on the phase evolution of a coherent quantum system such as cold atoms; it only requires sufficiently sensitive detectors,” said Schneider. “We are excited to contribute our cold-atom technology to this interdisciplinary endeavour and to develop atom interferometry into a powerful detector for fundamental physics.”

The Quantum Sensors for the Hidden Sector (QSHS) project, led by the University of Sheffield, has been awarded £4.8 million in funding. The project aims to contribute to the search for axions, low-mass ‘hidden’ particles that are candidates to solve the mystery of dark matter. They will develop new quantum measurement technology for inclusion in the US ADMX experiment, which can then be used to search for axions in parts of our galaxy’s dark matter halo that have never been explored before.

“The team will develop new electronic technology to a high level of sophistication and deploy it to search for the lowest-mass particles detected to date,” said Professor Stafford Withington from the Cavendish Laboratory, Co-Investigator and Senior Project Scientist on QSHS. “These particles are predicted to exist theoretically, but have not yet been discovered experimentally. Our ability to probe the particulate nature of the physical world with sensitivities that push at the limits imposed by quantum uncertainty will open up a new frontier in physics.

“This new window will allow physicists to explore the nature of physical reality at the most fundamental level, and it is extremely exciting that the UK will be playing a major international role in this new generation of science.”

Professor Withington is also involved in the Determination of Absolute Neutrino Mass using Quantum Technologies, which will be led by UCL. The project aims to harness recent breakthroughs in quantum technologies to solve one of the most important outstanding challenges in particle physics – determining the absolute mass of neutrinos. One of the universe’s most abundant particles neutrinos are a by-product of nuclear fusion within stars, therefore being key to our understanding of the processes within stars and the makeup of the universe. Moreover, knowing the value of the neutrino mass is critical to our understanding of the origin of matter and evolution of the universe. They are poorly understood however, and the researchers aim to develop pioneering new spectroscopy technology capable to precisely measure the mass of this elusive but important particle.

Professor Zoran Hadzibabic has received funding as part of the Quantum Simulators for Fundamental Physics project, led by the University of Nottingham. The project aims to develop quantum simulators capable of providing insights into the physics of the very early universe and black holes. The goals include simulating aspects of quantum black holes and testing theories of the quantum vacuum that underpin ideas on the origin of the universe.

The researchers, led by the University of Cambridge, were able to control the conductivity and magnetism of iron thiophosphate (FePS₃), a two-dimensional material which undergoes a transition from an insulator to a metal when compressed. This class of magnetic materials offers new routes to understanding the physics of new magnetic states and superconductivity.

Using new high-pressure techniques, the researchers have shown what happens to magnetic graphene during the transition from insulator to conductor and into its unconventional metallic state, realised only under ultra-high pressure conditions. When the material becomes metallic, it remains magnetic, which is contrary to previous results and provides clues as to how the electrical conduction in the metallic phase works. The newly discovered high-pressure magnetic phase likely forms a precursor to superconductivity so understanding its mechanisms is vital.

Their results, published in the journal Physical Review X, also suggest a way that new materials could be engineered to have combined conduction and magnetic properties, which could be useful in the development of new technologies such as spintronics, which could transform the way in which computers process information.

Properties of matter can alter dramatically with changing dimensionality. For example, graphene, carbon nanotubes, graphite and diamond are all made of carbon atoms, but have very different properties due to their different structure and dimensionality.

“But imagine if you were also able to change all of these properties by adding magnetism,” said first author Dr Matthew Coak, who is jointly based at Cambridge’s Cavendish Laboratory and the University of Warwick. “A material which could be mechanically flexible and form a new kind of circuit to store information and perform computation. This is why these materials are so interesting, and because they drastically change their properties when put under pressure so we can control their behaviour.”

In a previous study by Sebastian Haines of the Cavendish Laboratory and the Department of Earth Sciences, researchers established that the material becomes a metal at high pressure, and outlined how the crystal structure and arrangement of atoms in the layers of this 2D material change through the transition.

“The missing piece has remained however, the magnetism,” said Coak. “With no experimental techniques able to probe the signatures of magnetism in this material at pressures this high, our international team had to develop and test our own new techniques to make it possible.”

The researchers used new techniques to measure the magnetic structure up to record-breaking high pressures, using specially designed diamond anvils and neutrons to act as the probe of magnetism. They were then able to follow the evolution of the magnetism into the metallic state.

“To our surprise, we found that the magnetism survives and is in some ways strengthened,” co-author Dr Siddharth Saxena, group leader at the Cavendish Laboratory. “This is unexpected, as the newly-freely-roaming electrons in a newly conducting material can no longer be locked to their parent iron atoms, generating magnetic moments there - unless the conduction is coming from an unexpected source.”

In their previous paper, the researchers showed these electrons were ‘frozen’ in a sense. But when they made them flow or move, they started interacting more and more. The magnetism survives, but gets modified into new forms, giving rise to new quantum properties in a new type of magnetic metal.

How a material behaves, whether conductor or insulator, is mostly based on how the electrons, or charge, move around. However, the ‘spin’ of the electrons has been shown to be the source of magnetism. Spin makes electrons behave a bit like tiny bar magnets and point a certain way. Magnetism from the arrangement of electron spins is used in most memory devices: harnessing and controlling it is important for developing new technologies such as spintronics, which could transform the way in which computers process information.

“The combination of the two, the charge and the spin, is key to how this material behaves,” said co-author Dr David Jarvis from the Institut Laue-Langevin, France, who carried out this work as the basis of his PhD studies at the Cavendish Laboratory. “Finding this sort of quantum multi-functionality is another leap forward in the study of these materials.”

“We don’t know exactly what’s happening at the quantum level, but at the same time, we can manipulate it,” said Saxena. “It’s like those famous ‘unknown unknowns’: we’ve opened up a new door to properties of quantum information, but we don’t yet know what those properties might be.”

There are more potential chemical compounds to synthesise than could ever be fully explored and characterised. But by carefully selecting and tuning materials with special properties, it is possible to show the way towards the creation of compounds and systems, but without having to apply huge amounts of pressure.

Additionally, gaining fundamental understanding of phenomena such as low-dimensional magnetism and superconductivity allows researchers to make the next leaps in materials science and engineering, with particular potential in energy efficiency, generation and storage.

As for the case of magnetic graphene, the researchers next plan to continue the search for superconductivity within this unique material. “Now that we have some idea what happens to this material at high pressure, we can make some predictions about what might happen if we try to tune its properties through adding free electrons by compressing it further,” said Coak.

“The thing we’re chasing is superconductivity,” said Saxena. “If we can find a type of superconductivity that’s related to magnetism in a two-dimensional material, it could give us a shot at solving a problem that’s gone back decades.”

Reference:
Matthew J. Coak et al. ‘Emergent Magnetic Phases in Pressure-Tuned van der Waals Antiferromagnet FePS3.’ Physical Review X (2021). DOI: 10.1103/PhysRevX.11.011024

The researchers, from the University of Cambridge, used their method to culture and grow a ‘mini-airway’, the first time that a tube-shaped organoid has been developed without the need for any external support.

Using a mould made of a specialised polymer, the researchers were able to guide the size and shape of the mini-airway, grown from adult mouse stem cells, and then remove it from the mould when it reached the point where it could support itself.

Whereas the organoids currently used in medical research are at the microscopic scale, the method developed by the Cambridge team could make it possible to grow life-sized versions of organs. Their results are reported in the journal Advanced Science.

Organoids are tiny, three-dimensional cell assemblies that mimic the cell arrangement of fully-grown organs. They can be a useful way to study human biology and how it can go wrong in various diseases, and possibly how to develop personalised or regenerative treatments. However, assembling them into larger organ structures remains a challenge.

Other research teams have experimented with 3D printing techniques to develop larger mini-organs, but these often require an external support structure.

“Mini-organs are very small and highly fragile,” said Dr Yan Yan Shery Huang from Cambridge’s Department of Engineering, who co-led the research. “In order to scale them up, which would increase their usefulness in medical research, we need to find the right conditions to help the cells self-organise.”

Huang and her colleagues have proposed a new organoid engineering approach called Multi-Organoid Patterning and Fusion (MOrPF) to grow a miniature version of a mouse airway using stem cells. Using this technique, the scientists achieved faster assembly of organoids into airway tubes with uninterrupted passageways. The mini-airways grown using the MOrPF technique showed potential for scaling up to match living organ structures in size and shape, and retained their shape even in the absence of an external support.

The MOrPF technique involves several steps. First, a polymer mould – like a miniature version of a cake or jelly mould – is used to shape a cluster of many small organoids. The cluster is released from the mould after one day, and then grown for a further two weeks. The cluster becomes one single tubular structure, covered by an outer layer of airway cells. The moulding process is just long enough for the outer layer of the cells to form an envelope around the entire cluster. During the two weeks of further growth, the inner walls gradually disappear, leading to a hollow tubular structure.

“Gradual maturation of the cells is really important,” said Dr Joo-Hyeon Lee from Cambridge’s Wellcome – MRC Cambridge Stem Cell Institute, who co-led the research. “The cells need to be well-organised before we can release them so that the structures don’t collapse.”

The organoid cluster can be thought of like soap bubbles, initially packed together to form to the shape of the mould. In order to fuse into a single gigantic bubble from the cluster of compressed bubbles, the inner walls need to be broken down. In the MOrPF process, the fused organoid clusters are released from the mould to grow in floating, scaffold-free conditions, so that the cells forming the inner walls of the fused cluster can be taken out of the cluster. The mould can be made into different sizes or shapes, so that the researchers can pre-determine the shape of the finished mini-organ.

“The interesting thing is, if you think about the soap bubbles, the resulting big bubble is always spherical, but the special mechanical properties of the cell membrane of organoids make the resulting fused shape preserve the shape of the mould,” said co-author Professor Eugene Terentjev from Cambridge’s Cavendish Laboratory.

The team say their method closely approximated the natural process of organ tube formation in some animal species. They are hopeful that their technique will help create biomimetic organs to facilitate medical research.

The researchers first plan to use their method to build a three-dimensional ‘organ on a chip’, which enables real-time continuous monitoring of cells, and could be used to develop new treatments for disease while reducing the number of animals used in research. Eventually, the technique could also be used with stem cells taken from a patient, in order to develop personalised treatments in future.

The research was supported in part by the European Research Council, the Wellcome Trust and the Royal Society.

Reference:
Ye Liu et al. ‘Bio-assembling Macro-Scale, Lumenized Airway Tubes of Defined Shape via Multi-Organoid Patterning and Fusion.’ Advanced Science (2021). DOI: 10.1002/advs.202003332

The researchers, from the University of Cambridge, were able to inject a ‘needle’ of highly fragile quantum information in a ‘haystack’ of 100,000 nuclei. Using lasers to control an electron, the researchers could then use that electron to control the behaviour of the haystack, making it easier to find the needle. They were able to detect the ‘needle’ with a precision of 1.9 parts per million: high enough to detect a single quantum bit in this large ensemble.

The technique makes it possible to send highly fragile quantum information optically to a nuclear system for storage, and to verify its imprint with minimal disturbance, an important step in the development of a quantum internet based on quantum light sources. The results are reported in the journal Nature Physics.

The first quantum computers – which will harness the strange behaviour of subatomic particles to far outperform even the most powerful supercomputers – are on the horizon. However, leveraging their full potential will require a way to network them: a quantum internet. Channels of light that transmit quantum information are promising candidates for a quantum internet, and currently there is no better quantum light source than the semiconductor quantum dot: tiny crystals that are essentially artificial atoms.

However, one thing stands in the way of quantum dots and a quantum internet: the ability to store quantum information temporarily at staging posts along the network.

“The solution to this problem is to store the fragile quantum information by hiding it in the cloud of 100,000 atomic nuclei that each quantum dot contains, like a needle in a haystack,” said Professor Mete Atatüre from Cambridge’s Cavendish Laboratory, who led the research. “But if we try to communicate with these nuclei like we communicate with bits, they tend to ‘flip’ randomly, creating a noisy system.”

The cloud of quantum bits contained in a quantum dot don’t normally act in a collective state, making it a challenge to get information in or out of them. However, Atatüre and his colleagues showed in 2019 that when cooled to ultra-low temperatures also using light, these nuclei can be made to do ‘quantum dances’ in unison, significantly reducing the amount of noise in the system.

Now, they have shown another fundamental step towards storing and retrieving quantum information in the nuclei. By controlling the collective state of the 100,000 nuclei, they were able to detect the existence of the quantum information as a ‘flipped quantum bit’ at an ultra-high precision of 1.9 parts per million: enough to see a single bit flip in the cloud of nuclei.

“Technically this is extremely demanding,” said Atatüre, who is also a Fellow of St John’s College. “We don’t have a way of ‘talking’ to the cloud and the cloud doesn’t have a way of talking to us. But what we can talk to is an electron: we can communicate with it sort of like a dog that herds sheep.”

Using the light from a laser, the researchers are able to communicate with an electron, which then communicates with the spins, or inherent angular momentum, of the nuclei.

By talking to the electron, the chaotic ensemble of spins starts to cool down and rally around the shepherding electron; out of this more ordered state, the electron can create spin waves in the nuclei.

“If we imagine our cloud of spins as a herd of 100,000 sheep moving randomly, one sheep suddenly changing direction is hard to see,” said Atatüre. “But if the entire herd is moving as a well-defined wave, then a single sheep changing direction becomes highly noticeable.”

In other words, injecting a spin wave made of a single nuclear spin flip into the ensemble makes it easier to detect a single nuclear spin flip among 100,000 nuclear spins.

Using this technique, the researchers are able to send information to the quantum bit and ‘listen in’ on what the spins are saying with minimal disturbance, down to the fundamental limit set by quantum mechanics.

“Having harnessed this control and sensing capability over this large ensemble of nuclei, our next step will be to demonstrate the storage and retrieval of an arbitrary quantum bit from the nuclear spin register,” said co-first author Daniel Jackson, a PhD student at the Cavendish Laboratory.

“This step will complete a quantum memory connected to light – a major building block on the road to realising the quantum internet,” said co-first author Dorian Gangloff, a Research Fellow at St John’s College.

Besides its potential usage for a future quantum internet, the technique could also be useful in the development of solid-state quantum computing.

The research was supported in part by the European Research Council (ERC), the Engineering and Physical Sciences Research Council (EPSRC) and the Royal Society.

Reference:
D. M. Jackson et al. ‘Quantum sensing of a coherent single spin excitation in a nuclear ensemble.’ Nature Physics (2021). DOI: 10.1038/s41567-020-01161-4

The planet GJ 1132 b appears to have begun life as a gaseous world with a thick blanket of atmosphere. Starting out at several times the radius of Earth, this ‘sub-Neptune’ quickly lost its primordial hydrogen and helium atmosphere, which was stripped away by the intense radiation from its hot, young star. In a short period of time, it was reduced to a bare core about the size of Earth.

To the surprise of astronomers, new observations from Hubble have uncovered a secondary atmosphere that has replaced the planet’s first atmosphere. It is rich in hydrogen, hydrogen cyanide, methane and ammonia, and also has a hydrocarbon haze. Astronomers theorise that hydrogen from the original atmosphere was absorbed into the planet’s molten magma mantle and is now being slowly released by volcanism to form a new atmosphere. This second atmosphere, which continues to leak away into space, is continually being replenished from the reservoir of hydrogen in the mantle’s magma.

“This second atmosphere comes from the surface and interior of the planet, and so it is a window onto the geology of another world,” said team member Paul Rimmer from the University of Cambridge. “A lot more work needs to be done to properly look through it, but the discovery of this window is of great importance.”

“We first thought that these highly radiated planets would be pretty boring because we believed that they lost their atmospheres,” said team member Raissa Estrela of the Jet Propulsion Laboratory at the California Institute of Technology in Pasadena, California, USA. “But we looked at existing observations of this planet with Hubble and realised that there is an atmosphere there.”

“How many terrestrial planets don’t begin as terrestrials? Some may start as sub-Neptunes, and they become terrestrials through a mechanism whereby light evaporates the primordial atmosphere. This process works early in a planet’s life, when the star is hotter,” said team leader Mark Swain of the Jet Propulsion Laboratory. “Then the star cools down and the planet’s just sitting there. So you’ve got this mechanism that can cook off the atmosphere in the first 100 million years, and then things settle down. And if you can regenerate the atmosphere, maybe you can keep it.”

In some ways, GJ 1132 b has various parallels to Earth, but in some ways, it is also very different. Both have similar densities, similar sizes, and similar ages, being about 4.5 billion years old. Both started with a hydrogen-dominated atmosphere, and both were hot before they cooled down. The team’s work even suggests that GJ 1132 b and Earth have similar atmospheric pressure at the surface.

However, the planets’ formation histories are profoundly different. Earth is not believed to be the surviving core of a sub-Neptune. And Earth orbits at a comfortable distance from our yellow dwarf Sun. GJ 1132 b is so close to its host red dwarf star that it completes an orbit the star once every day and a half. This extremely close proximity keeps GJ 1132 b tidally locked, showing the same face to its star at all times — just as our moon keeps one hemisphere permanently facing Earth.

“The question is, what is keeping the mantle hot enough to remain liquid and power volcanism?” asked Swain. “This system is special because it has the opportunity for quite a lot of tidal heating.”

The phenomenon of tidal heating occurs through friction, when energy from a planet’s orbit and rotation is dispersed as heat inside the planet. GJ 1132 b is in an elliptical orbit, and the tidal forces acting on it are strongest when it is closest to or farthest from its host star. At least one other planet in the host star’s system also exerts a gravitational pull on the planet. The consequences are that the planet is squeezed or stretched by this gravitational “pumping.” That tidal heating keeps the mantle liquid for a long time. A nearby example in our own Solar System is the Jovian moon, Io, which has continuous volcanism as a result of a tidal tug-of-war between Jupiter and the neighbouring Jovian moons.

The team believes the crust of GJ 1132 b is extremely thin, perhaps only hundreds of feet thick. That’s much too feeble to support anything resembling volcanic mountains. Its flat terrain may also be cracked like an eggshell by tidal flexing. Hydrogen and other gases could be released through such cracks.

“This atmosphere, if it’s thin — meaning if it has a surface pressure similar to Earth — probably means you can see right down to the ground at infrared wavelengths. That means that if astronomers use the James Webb Space Telescope to observe this planet, there’s a possibility that they will see not the spectrum of the atmosphere, but rather the spectrum of the surface,” said Swain. “And if there are magma pools or volcanism going on, those areas will be hotter. That will generate more emission, and so they’ll potentially be looking at the actual geological activity — which is exciting!”

This result is significant because it gives exoplanet scientists a way to figure out something about a planet's geology from its atmosphere,” said Rimmer, who is affiliated both with Cambridge’s Cavendish Laboratory and Department of Earth Sciences. “It is also important for understanding where the rocky planets in our own Solar System — Mercury, Venus, Earth and Mars, fit into the bigger picture of comparative planetology, in terms of the availability of hydrogen versus oxygen in the atmosphere.”

Adapted from an ESA/JPL press release.

Results from the LHCb Collaboration at CERN suggests particles are not behaving the way they should according to the guiding theory of particle physics – suggesting gaps in our understanding of the Universe.

Physicists from the Universities of Cambridge, Bristol, and Imperial College London led the analysis of the data to produce this result, with funding from the Science and Technology Facilities Council. The result - which has not yet been peer-reviewed - was announced today at the Moriond Electroweak Physics conference and published as a preprint.

Beyond the Standard Model

Scientists across the world will be paying close attention to this announcement as it hints at the existence of new particles not explained by the Standard Model.

The Standard Model is the current best theory of particle physics, describing all the known fundamental particles that make up our Universe and the forces that they interact with. However, the Standard Model cannot explain some of the deepest mysteries in modern physics, including what dark matter is made of and the imbalance of matter and antimatter in the Universe.

Dr Mitesh Patel of Imperial College London, and one of the leading physicists behind the measurement, said: “We were actually shaking when we first looked at the results, we were that excited. Our hearts did beat a bit faster.

“It’s too early to say if this genuinely is a deviation from the Standard Model but the potential implications are such that these results are the most exciting thing I’ve done in 20 years in the field. It has been a long journey to get here.”

Building blocks of nature

Today’s results were produced by the LHCb experiment, one of four huge particle detectors at CERN’s Large Hadron Collider (LHC).

The LHC is the world’s largest and most powerful particle collider – it accelerates subatomic particles to almost the speed of light, before smashing them into each other.

These collisions produces a burst of new particles, which physicists then record and study in order to better understand the basic building blocks of nature.

The LHCb experiment is designed to study particles called ‘beauty quarks’, an exotic type of fundamental particle not usually found in nature but produced in huge numbers at the LHC.

Once the beauty quarks are produced in the collision, they should then decay in a certain way, but the LHCb team now has evidence to suggest these quarks decay in a way not explained by the Standard Model.

Questioning the laws of physics

The updated measurement could question the laws of nature that treat electrons and their heavier cousins, muons, identically, except for small differences due to their different masses. 

According to the Standard Model, muons and electrons interact with all forces in the same way, so beauty quarks created at LHCb should decay into muons just as often as they do to electrons.

But these new measurements suggest this is not happening.

One way these decays could be happening at different rates is if never-before-seen particles were involved in the decay and tipped the scales in favour of electrons.

Dr Paula Alvarez Cartelle from Cambridge’s Cavendish Laboratory, was one of the leaders of the team that found the result, said: “This new result offers tantalising hints of the presence of a new fundamental particle or force that interacts differently with these different types of particles.

“The more data we have, the stronger this result has become. This measurement is the most significant in a series of LHCb results from the past decade that all seem to line up – and could all point towards a common explanation.

“The results have not changed, but their uncertainties have shrunk, increasing our ability to see possible differences with the Standard Model.”

Not a foregone conclusion

In particle physics, the gold standard for discovery is five standard deviations – which means there is a 1 in 3.5 million chance of the result being a fluke. This result is three deviations – meaning there is still a 1 in 1000 chance that the measurement is a statistical coincidence.

It is therefore too soon to make any firm conclusions. However, while they are still cautious, the team members are nevertheless excited by this apparent deviation and its potentially far-reaching implications.

The LHCb scientists say there has been a breadcrumb trail of clues leading up to this result – with a number of other, less significant results over the past seven years also challenging the Standard Model in a similar way, though with less certainty.

If this result is what scientists think it is – and hope it is – there may be a whole new area of physics to be explored.

Dr Konstantinos Petridis of the University of Bristol, who also played a lead role in the measurement, said: “The discovery of a new force in nature is the holy grail of particle physics. Our current understanding of the constituents of the Universe falls remarkably short – we do not know what 95% of the Universe is made of or why there is such a large imbalance between matter and anti-matter.

“The discovery of a new fundamental force or particle, as hinted at by the evidence of differences in these measurements could provide the breakthrough required to start to answer these fundamental questions.”

Dr Harry Cliff, LHCb Outreach Co-Convener, from Cambridge’s Cavendish Laboratory, said: “This result is sure to set physicists’ hearts beating a little faster today. We’re in for a terrifically exciting few years as we try to figure out whether we’ve finally caught a glimpse of something altogether new.”

It is now for the LHCb collaboration to further verify their results by collating and analysing more data, to see if the evidence for some new phenomena remains.

Additional information – about the result

The results compare the decay rates of Beauty mesons into final states with electrons with those into muons.

The LHCb experiment is one of the four large experiments at the Large Hadron Collider (LHC) at CERN in Geneva, and is designed to study decays of particles containing a beauty quark

This is the quark with the highest mass forming bound states. The resulting precision measurements of matter-antimatter differences and rare decays of particles containing a beauty quark allow sensitive tests of the Standard Model of particle physics.

Rather than flying out in all directions, beauty quarks that are created in the collisions of the proton beams at LHC stay close to the beam pipe.

The UK team studied a large number of beauty or b quarks decaying into a strange-quark and two oppositely charged leptons. By measuring how often the b-quark decays into a final state containing a pair of muons or a pair of electrons, they found evidence that the laws of physics might be different, depending on whether the final state contains electrons or muons. 

Since the b-quark is heavy compared to the masses of the electron and muon it is expected that the b-quark decays with the same probability into a final state with electrons and muons. The ratio between the two decay probabilities is hence predicted to be one.

However analysis of the UK team found evidence that the decay probability is less than one.

The results, reported in the journal Physical Review Letters, could be used to design new types of materials and quantum technology devices. The researchers, from the University of Cambridge, captured the movement of the atoms at speeds that are eight orders of magnitude too fast for conventional microscopes.

Two-dimensional materials, such as graphene, have the potential to improve the performance of existing and new devices, due to their unique properties, such as outstanding conductivity and strength. Two-dimensional materials have a wide range of potential applications, from bio-sensing and drug delivery to quantum information and quantum computing. However, in order for two-dimensional materials to reach their full potential, their properties need to be fine-tuned through a controlled growth process.

These materials normally form as atoms ‘jump’ onto a supporting substrate until they attach to a growing cluster. Being able to monitor this process gives scientists much greater control over the finished materials. However, for most materials, this process happens so quickly and at such high temperatures that it can only be followed using snapshots of a frozen surface, capturing a single moment rather than the whole process.

Now, researchers from the University of Cambridge have followed the entire process in real time, at comparable temperatures to those used in industry.

The researchers used a technique known as ‘helium spin-echo’, which has been developed in Cambridge over the last 15 years. The technique has similarities to magnetic resonance imaging (MRI), but uses a beam of helium atoms to ‘illuminate’ a target surface, similar to light sources in everyday microscopes.

“Using this technique, we can do MRI-like experiments on the fly as the atoms scatter,” said Dr Nadav Avidor from Cambridge’s Cavendish Laboratory, the paper’s senior author. “If you think of a light source that shines photons on a sample, as those photons come back to your eye, you can see what happens in the sample.”

Instead of photons however, Avidor and his colleagues use helium atoms to observe what happens on the surface of the sample. The interaction of the helium with atoms at the surface allows the motion of the surface species to be inferred.

Using a test sample of oxygen atoms moving on the surface of ruthenium metal, the researchers recorded the spontaneous breaking and formation of oxygen clusters, just a few atoms in size, and the atoms that quickly diffuse between the clusters.

“This technique isn’t a new one, but it’s never been used in this way, to measure the growth of a two-dimensional material,” said Avidor. “If you look back on the history of spectroscopy, light-based probes revolutionised how we see the world, and the next step – electron-based probes – allowed us to see even more.

“We’re now going another step beyond that, to atom-based probes, allowing us to observe more atomic scale phenomena. Besides its usefulness in the design and manufacture of future materials and devices, I’m excited to find out what else we’ll be able to see.”

The research was conducted in the Cambridge Atom Scattering Centre and supported by the Engineering and Physical Sciences Research Council (EPSRC).

Reference:
Jack Kelsall et al. ‘Ultrafast diffusion at the onset of growth: O=Ru(0001).’ Physical Review Letters (2021). DOI: 10.1103/PhysRevLett.126.155901

Led by 2019 Physics Nobel Laureate Professor Didier Queloz, the Cambridge Initiative for Planetary Science and Life in the Universe will be the driving force for the development of a new Cambridge research community investigating life in the Universe, from understanding how it emerged on Earth to examining the processes that could make other planets suitable for life.

The initiative comes at a crucial moment in science, as scientists are able to study exoplanets – planets orbiting stars other than our Sun – in ever-greater detail, and outstanding progress is being made in prebiotic chemistry: carefully-regulated laboratory experiments to recreate the conditions when life first formed on Earth.

In addition, the recent successful landing of the Mars 2020 Perseverance Rover set in motion one of the greatest international scientific endeavours of recent decades. Within the next ten years, samples returned from a four-billion-year-old lake deposit on Mars will offer a unique window on the Solar System as it was when life originated on Earth and could provide evidence of ancient life on the Red Planet.

“These recent revolutions and future perspectives offered by next-generation space missions mean that the planets are aligned for us to create a vibrant new field at the cutting edge of modern science,” said Queloz, from Cambridge’s Cavendish Laboratory and Director of the Initiative.

Building on the University’s research excellence and enhancing the multidisciplinary research conducted in various departments of the School of the Physical Sciences, the focus of the research within the new Initiative will be to understand the origins and physical properties of planets throughout the Universe, as well as the chemical and biological processes capable of starting and sustaining life.

“By bringing together chemists, geologists, biologists, and astrophysicists to work creatively together toward a common goal, the Initiative will ensure we truly exploit the full potential of this exciting new field of research, bringing us closer to understanding life in the Universe and finding life beyond Earth,” said Queloz.

The School of the Physical Sciences and its various departments (Cavendish Laboratory, Chemistry, Applied Mathematics and Theoretical Physics, Earth Sciences and the Institute of Astronomy) recently committed to an initial funding package that will support the Initiative as it builds the foundations of its vision and will create the conditions for its research and educational ambitions to grow and develop.

Professor Nigel Peake, Head of the School of the Physical Sciences, said: “During the last decades our understanding of the microbiology of life has made spectacular progress, but knowledge on origins of life on Earth, and more generally in the Universe, are still nascent. This is about to change. I am proud that Cambridge is leading the way to a radically new approach based on a convergence of recent results in astrophysics, planetology and molecular chemistry.

“With the Cambridge Initiative for Planetary Science and Life in the Universe, we will provide the infrastructure that will allow scholars from various disciplines to combine their interests to address the fundamental question of our origins in the Universe. This sets the scene for a revolution to come.”

For more information, news and updates about the Cambridge Initiative for Planetary Science and Life in the Universe, visit www.iplu.phy.cam.ac.uk.

Two hundred and nine senior scientists from across Europe were awarded grants in today’s announcement, representing a total of €507 million in research funding. The UK has 51 grantees in this year’s funding round, the most of any ERC participating country.

ERC grants are awarded through open competition to projects headed by starting and established researchers, irrespective of their origins, who are working or moving to work in Europe. The sole criterion for selection is scientific excellence. ERC Advanced Grants are designed to support excellent scientists in any field with a recognised track record of research achievements in the last ten years. Apart from strengthening Europe’s knowledge base, the new research projects will also lead to the creation of some 1,900 new jobs for post-doctoral fellows, PhD students and other research staff. 

Professor Melinda Duer from the Yusuf Hamied Department of Chemistry has been awarded a grant for her EXTREME project to explore the chemistry that happens when a biological tissue stretches or breaks.

So-called mechanochemistry leads to molecules being generated within the tissue that may be involved in communicating tissue damage to cells. Detecting and understanding this chemistry is highly relevant for understanding ageing, and for developing new therapeutics for degenerative diseases and cancer.

“This award means I can do the research I’ve been dreaming about for the last ten years,” said Duer. “I am extremely grateful to the European Research Council for giving me this amazing opportunity. The ERC is one of the few organisations that understands the need for longer-term funding for high-risk, high-reward research, which is essential for this project. I really couldn’t be more delighted and I can’t wait to get started!”

Professor Manish Chhowalla, from the Department of Materials Science and Metallurgy, received funding for his 2D-LOTTO project, for the development of energy-efficient electronics.

“This grant will enable our research group to realise the next generation of energy-efficient electronics based on two-dimensional semiconductors,” he said. “The funding will also support a team of students, early career researchers and senior academics to address the challenges of demonstrating practical tunnel field effect transistors.”

Professor Henning Sirringhaus from the Cavendish Laboratory received funding for his NANO-DECTET project, for the development of next-generation energy materials. “Worldwide, only about a third of primary energy is converted into useful energy services: the other two thirds are wasted as heat in the various industrial, transportation, residential energy conversion and electricity generation processes,” said Sirringhaus. “Given the urgent need to mitigate the dangerous consequences of climate change, a waste of energy on this scale needs to be addressed immediately.

“Thermoelectric waste-heat-to-electricity conversion could offer a potential solution, but the performance of thermoelectric materials is currently insufficient. In this project we will use the unique physics of molecular organic semiconductors, as well as hybrid organic-inorganic semiconductors, to make efficient, low-temperature thermoelectric materials.”

Professor Marcos Martinon-Torres from the Department of Archaeology received funding for his REVERSEACTION project, which will study how societies in the past cooperated. “Many prehistoric societies did pretty well at maintaining rich and complex lives without the need for permanent power hierarchies and coercive authorities,” he said. “Arguably, they chose to cooperate, and not just to ensure survival. The lack of state structures did not stop them from developing and sustaining complex technologies, making extraordinary artefacts that required exotic materials, challenging skills and labour arrangements. I’m keen to understand why, but also how they managed.

“This grant couldn’t have come at a better time, as collective action is increasingly recognised as the only way to tackle some of our greatest global concerns, and there is value in studying how people collaborated in the past. With our labs freshly revamped through our recent AHRC infrastructure grant, we are ready to take on a new large-scale, challenging archaeological science project.”

Professor Marta Mirazon Lahr, also from the Department of Archaeology, was awarded funding for her NGIPALAJEM project, which will bring a new understanding of how the evolution of our species is part of a broader and longer African evolutionary landscape.

“My research is in human evolution, a field that advances through technical breakthroughs, new ideas, and critically, new fossils,” said Lahr. “A big part of my work is to find new hominin fossils in Africa, which requires not only supportive local communities and institutions, but long-term planning and implementation, a dedicated team, significant funds and the time to excavate, study, compare and interpret new discoveries. This new grant from the ERC gives me all this and more – and I just can’t wait to get started!”

Professor Richard Samworth’s RobustStats project will develop robust statistical methodology and theory for large-scale data. “Large-scale data are usually messy: they may be collected under different conditions, and data may be missing or corrupted, which makes it difficult to draw reliable conclusions,” said Samworth, from the Department of Pure Mathematics and Mathematical Statistics. “This grant will allow me to focus my time on developing robust statistical methodology and theory to address these challenges. Equally importantly, I will be able to build a group of PhD students and post-docs that will dramatically increase the scale and scope of what we are able to achieve.

Professor Zoran Hadzibabic from the Cavendish Laboratory was awarded funding for his UNIFLAT project. One of the great successes of the last-century physics was recognising that complex and seemingly disparate systems are fundamentally alike. This allowed the classification of the equilibrium states of matter into classes based on their basic properties. At the heart of this classification is the universal collective behaviour, insensitive to the microscopic details, displayed by systems close to phase transitions.

A grand challenge for modern physics is to achieve such a feat for the far richer world of the nonequilibrium collective phenomena. “Our ambition is to make a leading contribution to this worldwide effort, through a series of coordinated experiments on homogeneous atomic gases in two-dimensional (2D) geometry,” said Hadzibabic. “Specifically, we will study in parallel three problems – the dynamics of the topological Berezinskii-Kosterlitz-Thouless phase transition, turbulence in driven systems, and the universal spatiotemporal scaling behaviour in isolated quantum systems far from equilibrium. Each of these topics is fascinating and of fundamental importance in its own right, but beyond that we will experimentally establish an emerging picture that connects them.”

Dr Helen Williams from the Department of Earth Sciences said: “By funding the EarthMelt project, the ERC has given me the amazing opportunity to study the early evolution of the Earth and its transition from a largely molten state to the habitable planet we know today. This funding will also help me to develop exciting new instrumentation and analytical techniques, and, most importantly, mentor and support the next generation of PhD students and postdoctoral researchers working in geochemistry.”

Professor Sir Richard Friend from the Cavendish Laboratory has been awarded funding for his Spin Control in Radical Semiconductors (SCORS) project, which will explore the electronic properties of organic semiconductors that have an unpaired electron to give net magnetic spin. The project is based on a recent discovery that this unpaired electron can couple strongly to light, allowing very efficient luminescence in LEDs. Friend’s group will explore new combinations of optical excited states with magnetic spin states. This will allow new designs for LEDs and solar cells, and opportunities to control the ground state spin polarisation in spintronic devices.

Professor Christopher Hunter’s InfoMols project is focused on synthetic information molecules. “The aim of our project is replication and evolution with artificial polymers,” said Hunter, from the Yusuf Hamied Department of Chemistry. “The timeframe for achieving such a breakthrough is unpredictable, and it is the flexibility provided by an ERC award that makes tackling such challenging targets possible.”

Professor Mark Gross from the Department of Pure Mathematics and Mathematical Statistics received funding for his Mirror symmetry in Algebraic Geometry (MSAG) project, and Professor Geoffrey Khan from the Faculty of Asian and Middle Eastern Studies was awarded funding for ALHOME: Echoes of Vanishing Voices in the Mountains: A Linguistic History of Minorities in the Near East.

The researchers, led by the University of Cambridge and the Technical University of Munich, found that by swapping one out of every 1,000 atoms of one material for another, they were able to triple the luminescence of a new material class of light emitters known as halide perovskites.  

This ‘atom swapping’, or doping, causes the charge carriers to get stuck in a specific part of the material’s crystal structure, where they recombine and emit light. The results, reported in the Journal of the American Chemical Society, could be useful for low-cost printable and flexible LED lighting, displays for smartphones or cheap lasers.

Many everyday applications now use light-emitting devices (LEDs), such as domestic and commercial lighting, TV screens, smartphones and laptops. The main advantage of LEDs is they consume far less energy than older technologies.

Ultimately, also the entirety of our worldwide communication via the internet is driven by optical signals from very bright light sources that within optical fibres carry information at the speed of light across the globe.

The team studied a new class of semiconductors called halide perovskites in the form of nanocrystals which measure only about a ten-thousandth of the thickness of a human hair. These ‘quantum dots’ are highly luminescent materials: the first high-brilliance QLED TVs incorporating quantum dots recently came onto the market.

The Cambridge researchers, working with Daniel Congreve’s group at Harvard, who are experts in the fabrication of quantum dots, have now greatly improved the light emission from these nanocrystals. They substituted one out of every one thousand atoms with another – swapping lead for manganese ions – and found the luminescence of the quantum dots tripled.

A detailed investigation using laser spectroscopy revealed the origin of this observation. “We found that the charges collect together in the regions of the crystals that we doped,” said Sascha Feldmann from Cambridge’s Cavendish Laboratory, the study’s first author. “Once localised, those energetic charges can meet each other and recombine to emit light in a very efficient manner.”

“We hope this fascinating discovery: that even smallest changes to the chemical composition can greatly enhance the material properties, will pave the way to cheap and ultrabright LED displays and lasers in the near future,” said senior author Felix Deschler, who is jointly affiliated at the Cavendish and the Walter Schottky Institute at the Technical University of Munich.

In the future, the researchers hope to identify even more efficient dopants which will help make these advanced light technologies accessible to every part of the world.

Reference:
Sascha Feldmann et al. ‘Charge carrier localization in doped perovskite nanocrystals enhances radiative recombination.’, Journal of the American Chemical Society (2021). DOI:10.1021/jacs.1c01567