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News from the Department of Physics.

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    The Vice-Chancellor, Sir Leszek Borysiewicz, said: “This is fantastic news. The Cavendish is and will serve as a national asset, to the benefit of research both in Cambridge and across the UK.

    “This announcement demonstrates the Government’s commitment to regional and national scientific growth and innovation. It presents a major opportunity for us to create a world-leading facility in the heart of the greater Cambridge high-tech cluster and deliver a step-change in physical science research capability in the UK.”

    Professor Andy Parker, Head of the Cavendish Laboratory, said: “Thanks to this welcome announcement we look forward to working with partners in Government and industry and other universities to further the globally important research which this department undertakes.

    “The Cavendish Laboratory has an extraordinary history of discovery and innovation in physics since its opening in 1874, including the determination of the double-helix structure of the DNA molecule by Francis Crick and James Watson. This funding allows us to continue the tradition of innovation and originality that has been at the heart of the laboratory's programme since its foundation.”

    The Government has announced a £75 million investment in the University of Cambridge Cavendish Laboratory as part of Wednesday's Spending Review. This will be matched with a further £75 million from the University to transform the Cavendish, helping maintain Britain’s position at the forefront of physical sciences research.

    This funding allows us to continue the tradition of innovation and originality that has been at the heart of the laboratory's programme since its foundation.
    Andy Parker

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    A new ‘periodic table’ of protein complexes, devised by an interdisciplinary team of researchers, provides a unified way to classify and visualise protein complexes, which drive a huge range of biological processes, from DNA replication to catalysing metabolic reactions.

    The table, published in the journal Science, offers a new way of looking at almost all known molecular structures and predicting how new ones could be made, providing a valuable tool for research into evolution and protein engineering.

    By using the table, researchers are able predict the likely forms of protein complexes with unknown structure, estimate the feasibility of entirely new structures, and identify possible errors in existing structural databases. It was created by an interdisciplinary team led by researchers at the University of Cambridge and the Wellcome Genome Campus.

    Almost every biological process depends on proteins interacting and assembling into complexes in a specific way, and many diseases, such as Alzheimer’s and Parkinson’s, are associated with problems in complex assembly. The principles underpinning this organisation are not yet fully understood, but the new periodic table presents a systematic, ordered view on protein assembly, providing a visual tool for understanding biological function.

    “We’re bringing a lot of order into the messy world of protein complexes,” said the paper’s lead author Sebastian Ahnert of Cambridge’s Cavendish Laboratory, a physicist who regularly tangles with biological problems. “Proteins can keep combining in these simple ways, adding more and more levels of complexity and resulting in a huge variety of structures. What we’ve made is a classification based on underlying principles that helps people get a handle on the complexity.”

    The exceptions to the rule are interesting in their own right, added Ahnert, and are the subject of continuing studies.

    “Evolution has given rise to a huge variety of protein complexes, and it can seem a bit chaotic,” said study co-author Joe Marsh, formerly of the Wellcome Genome Campus and now of the MRC Human Genetics Unit at the University of Edinburgh. “But if you break down the steps proteins take to become complexes, there are some basic rules that can explain almost all of the assemblies people have observed so far.”

    Ballroom dancing can be seen as an endless combination of riffs on the waltz, fox trot and cha-cha. Similarly, the ‘dance’ of protein complex assembly can be seen as endless variations on dimerization (one doubles, and becomes two), cyclisation (one forms a ring of three or more) and subunit addition (two different proteins bind to each other). Because these happen in a fairly predictable way, it’s not as hard as you might think to predict how a novel protein would form.

    Some protein complexes, called homomers, feature multiple copies of a single protein, while others, called heteromers, are made from several different types of proteins. The table shows that there is a very close relationship between the possible structures of heteromers and homomers. In fact, the vast majority of heteromers can be thought of as homomers in which the single protein is replaced by a repeated unit of several proteins. The table was constructed using computational analysis of a large database of protein-protein interfaces.

    “By analysing the tens of thousands of protein complexes for which three-dimensional structures have already been experimentally determined, we could see repeating patterns in the assembly transitions that occur – and with new data from mass spectrometry we could start to see the bigger picture,” said Walsh.

    “The core work for this study is in theoretical physics and computational biology, but it couldn’t have been done without the mass spectrometry work by our colleagues at Oxford University,” said Sarah Teichmann, Research Group Leader at the European Bioinformatics Institute (EMBL-EBI) and the Wellcome Trust Sanger Institute. “This is yet another excellent example of how extremely valuable interdisciplinary research can be.”

    Ahnert SE, et. al. ‘Principles of assembly reveal a periodic table of protein complexes.’ Science (2015). DOI: 10.1126/science.aaa2245

    Adapted from an EMBL-EBI press release.


    Researchers have devised a periodic table of protein complexes, making it easier to visualise, understand and predict how proteins combine to drive biological processes.

    We’re bringing a lot of order into the messy world of protein complexes
    Sebastian Ahnert
    The periodic table of proteins

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    At the start of December a rumour swirled around the internet and physics lab coffee rooms that researchers at the Large Hadron Collider had spotted a new particle. After a three-year drought that followed the discovery of the Higgs boson, could this be the first sign of new physics that particle physicists have all been desperately hoping for?

    Researchers working on the LHC experiments remained tight-lipped until December 14 when physicists packed out CERN’s main auditorium to hear presentations from the scientists working on CMS and ATLASexperiments, the two gargantuan particle detectors that discovered the Higgs boson in 2012. Even watching the online webcast, the excitement was palpable.

    Everybody was wondering if we would witness the beginning of a new age of discovery. The answer is … maybe.

    Baffling bump

    The CMS results were revealed first. At first the story was familiar, an impressive range of measurements that again and again showed no signs of new particles. But in the last few minutes of the presentation a subtle but intriguing bump on a graph was revealed that hinted at a new heavy particle decaying into two photons (particles of light). The bump appeared at a mass of around 760GeV (the unit of mass and energy used in particle physics – the Higgs boson has a mass of about 125 GeV) but was far too weak a signal to be conclusive on its own. The question was, would ATLAS see a similar bump in the same place?

    The ATLAS presentation mirrored the one from CMS, another list of non-discoveries. But, saving the best for last, a bump was unveiled towards the end, close to where CMS saw theirs at 750GeV – but bigger. It was still too weak to reach the statistical threshold to be considered solid evidence, but the fact that both experiments saw evidence in the same place is exciting.

    The discovery of the Higgs back in 2012 completed the Standard Model, our current best theory of particle physics, but left many unsolved mysteries. These include the nature of “dark matter”, an invisible substance that makes up around 85% of the matter in the universe, the weakness of gravity and the way that the laws of physics appear fine-tuned to allow life to exist, to name but a few.


    Could supersymmetry one day crack the mystery of all the dark matter lurking in galaxy clusters?NASA/wikimedia


    A number of theories have been proposed to solve these problems. The most popular is an idea called supersymmetry, which proposes that there is a heavier super-partner for every particle in the Standard Model. This theory provides an explanation for the fine-tuning of the laws of physics and one of the super-partners could also account for dark matter.

    Supersymmetry predicts the existence of new particles that should be in reach of the LHC. But despite high hopes the first run of the machine from 2009-2013 revealed a barren subatomic wilderness, populated only by a solitary Higgs boson. Many of the theoretical physicists working on supersymmetry have found the recent results from the LHC rather depressing. Some had begun to worry that answers to the outstanding questions in physics might lie forever beyond our reach.

    This summer the 27km LHC restarted operation after a two-year upgrade that almost doubled its collision energy. Physicists are eagerly waiting to see what these collisions reveal, as higher energy makes it possible to create heavy particles that were out of reach during the first run. So this hint of a new particle is very welcome indeed.

    A cousin of Higgs?

    Andy Parker, head of Cambridge’s Cavendish Laboratory and senior member of the ATLAS experiment, told me: “If the bump is real, and it decays into two photons as seen, then it must be a boson, most likely another Higgs boson. Extra Higgs are predicted by many models, including supersymmetry”.

    Perhaps even more exciting, it could be a type of graviton, a hypothesised particle associated with the force of gravity. Crucially, gravitons exist in theories with additional dimensions of space to the three (height, width and depth) we experience.

    For now, physicists will remain sceptical – more data is needed to rule this intriguing hint in or out. Parker described the results as “preliminary and inconclusive” but added, “should it turn out to be the first sign of physics beyond the standard model, with hindsight, this will be seen as historic science.”

    Whether this new particle turns out to be real or not, one thing that everyone agrees on is that 2016 is going to be an exciting year for particle physics.

    Harry Cliff, Particle physicist and Science Museum fellow, University of Cambridge

    This article was originally published on The Conversation. Read the original article.

    The opinions expressed in this article are those of the individual author(s) and do not represent the views of the University of Cambridge.

    Harry Cliff (Cavendish Laboratory) discusses the potential discovery of a new particle at the Large Hadron Collider and its implications for particle physics.

    The Large Hadron Collider/ATLAS at CERN

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    The University will host an IdeasLab looking at how breakthroughs in carbon reduction technologies will transform industries. IdeasLabs are quick-fire visual presentations followed by workgroup discussion, and have proved a successful format for engaging various communities in academic thinking.

    Carbon Reduction Technologies: The University of Cambridge IdeasLab

    Wednesday 20 January 16:15 - 17:30

    Sir Leszek Borysiewicz, Vice-Chancellor, will introduce this event, which will look at how research by Cambridge academics has led to breakthroughs in carbon reduction technologies that will transform a range of industries. Ideas to be discussed include:

    • Decarbonizing industrial-scale processes using virtual avatars
    • Self-healing concrete for low-carbon infrastructure
    • Improving solar materials efficiency using quantum mechanics
    • Quantum materials for zero-loss transmission of electricity

    The event is supported Energy@Cambridge, a Strategic Research Initiative that brings together the activities of over 250 world-leading academics working in all aspects of energy-related research, covering energy supply, conversion and demand, across a wide range from departments.

    The speakers, all members of the Strategic Research Initiative, are:

    Professor Abir Al-Tabbaa, Department of Engineering

    Professor Al-Tabbaa is a Director of the Centre for Doctoral Training in Future Infrastructure and Built Environment. She leads international work on sustainable and innovative materials for construction and the environment. Her particular expertise relates to low-carbon and self-healing construction materials, ground improvement, soil mix technology and contaminated land remediation.

    See also:

    Professor Sir Richard Friend, Department of Physics

    Professor Friend is the Director of the Maxwell Centre and the Winton Fund for the Physics of Sustainability. He is the lead academic on one of Energy@Cambridge’s Grand Challenges– Materials for Energy Efficient Information Communications Technology.

    Professor Friend’s research encompasses the physics, materials science and engineering of semiconductor devices made with carbon-based semiconductors, particularly polymers. His research group was first to demonstrate using polymers efficient operation of field-effect transistors and light-emitting diodes. These advances revealed that the semiconductor properties of this broad class of materials are unexpectedly clean, so that semiconductor devices can both reveal their novel semiconductor physics, including their operation in efficient photovoltaic diodes, optically-pumped lasing, directly-printed polymer transistor circuits and light-emitting transistors.

    See also:

    Professor Markus Kraft, Department of Chemical Engineering and Biotechnology

    Professor Kraft is the director of the Singapore-Cambridge CREATE Research Centre and a principal investigator of the Cambridge Centre for Carbon Reduction in Chemical Technology (C4T), one of the Grand Challenges. C4T is a world-leading partnership between Cambridge and Singapore, set up to tackle the environmentally relevant and complex problem of assessing and reducing the carbon footprint of the integrated petro-chemical plants and electrical network on Jurong Island in Singapore.

    Professor Kraft has contributed to the detailed modelling of combustion synthesis of organic and inorganic nanoparticles. He has worked on fluidization, spray drying and granulation of fine powders. His interested include computational modelling and optimization targeted towards developing carbon abatement and emissions reduction technologies.

    Dr Suchitra Sebastian, Department of Physics

    Dr Sebastian creates and studies interesting quantum materials - often under extreme conditions such as very high magnetic and electric fields, enormous pressures, and very low temperatures - with a view to discovering unusual phases of matter. Among these are the family of superconductors - which have the exciting property of transporting electricity with no energy loss - and hence hold great promise for energy saving applications. One of her research programmes is to create a new generation of superconductors that operate at accessible temperatures, thus providing energy transmission and storage solutions of the future.

    See also:

    Energy@Cambridge is working to develop new technologies to reduce the carbon footprint of industrial processes, energy generation and transmission, and building construction. Its aims include leveraging the University’s expertise to tackle grand technical and intellectual challenges in energy, integrating science, technology and policy research.

    The initiative has four Grand Challenges, focused on developing and delivering new large-scale collaborative activities, facilities, centres and research directions by bringing together academics and external partners to work on future energy challenges where we believe we can make a significant impact.

    Will Science Save Us?

    Friday 22 January

    The Vice Chancellor and Dr Suchitra Sebastian will take part in a lunchtime discussion entitled Will Science Save Us?, which will look at how we accelerate scientific breakthroughs that address society's greatest challenges.

    * * *

    The World Economic Forum is an independent international organisation engaging business, political, academic and other leaders of society to shape global, regional and industry agendas; this year’s theme is The Reshaping of the World: Consequences for Society, Politics and Business.

    The Forum will provide an opportunity for the Cambridge researchers to engage with decision-makers in business, NGOs and in public policy, and to highlight new ideas from Cambridge in responding to global challenges.

    For further information or to contact any of the speakers, please contact the team at Energy@Cambridge.

    The Vice Chancellor of the University of Cambridge is to lead a delegation of academics to the annual meeting of the World Economic Forum at Davos, Switzerland, in January 2016, to explore issues including carbon reduction technologies and how science and engineering can best address society's greatest challenges.

    Coal Fired Power Station (cropped)

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    An international team of scientists have observed ripples in the fabric of spacetime called gravitational waves, arriving at the earth from a cataclysmic event in the distant universe. This confirms a major prediction of Albert Einstein’s 1915 general theory of relativity and opens an unprecedented new window onto the cosmos.

    The gravitational waves were detected on 14 September 2015 at 09:51 UK time by both LIGO (Laser Interferometer Gravitational-wave Observatory) detectors in Louisiana and Washington State in the US. They originated from two black holes, each around 30 times the mass of the Sun and located more than 1.3 billion light years from Earth, coalescing to form a single, even more massive black hole.

    The LIGO Observatories are funded by the National Science Foundation (NSF), and were conceived, built, and are operated by Caltech and MIT. The discovery, published in the journal Physical Review Letters, was made by the LIGO Scientific Collaboration (which includes the GEO Collaboration and the Australian Consortium for Interferometric Gravitational Astronomy) and the Virgo Collaboration using data from the two LIGO detectors.

    “The discovery of gravitational waves by the LIGO team is an incredible achievement,” said Professor Stephen Hawking, the Dennis Stanton Avery and Sally Tsui Wong-Avery Director of Research at the Department of Applied Mathematics and Theoretical Physics at the University of Cambridge. “It is the first observation of gravitational waves as predicted by Einstein and will allow us new insights into our universe. The gravitational waves were released from the collision of two black holes, the properties of which are consistent with predictions I made in Cambridge in the 1970s, such as the black hole area and uniqueness theorems. We can expect this observation to be the first of many as LIGO sensitivity increases, keeping us all busy with many further surprises.”

    Gravitational waves carry unique information about the origins of our Universe and studying them is expected to provide important insights into the evolution of stars, supernovae, gamma-ray bursts, neutron stars and black holes. However, they interact very weakly with particles and require incredibly sensitive equipment to detect. British and German teams, including researchers from the University of Cambridge, working with US, Australian, Italian and French colleagues as part of the LIGO Scientific Collaboration and the Virgo Collaboration, are using a technique called laser interferometry.

    Each LIGO site comprises two tubes, each four kilometres long, arranged in an L-shape. A laser is beamed down each tube to very precisely monitor the distance between mirrors at each end. According to Einstein’s theory, the distance between the mirrors will change by a tiny amount when a gravitational wave passes by the detector. A change in the lengths of the arms of close to 10-19 metres (just one-ten-thousandth the diameter of a proton) can be detected.

    According to general relativity, a pair of black holes orbiting around each other lose energy through the emission of gravitational waves, causing them to gradually approach each other over billions of years, and then much more quickly in the final minutes. During the final fraction of a second, the two black holes collide into each other at nearly one-half the speed of light and form a single more massive black hole, converting a portion of the combined black holes’ mass to energy, according to Einstein’s formula E=mc2. This energy is emitted as a final strong burst of gravitational waves. It is these gravitational waves that LIGO has observed.

    Independent and widely separated observatories are necessary to verify the direction of the event causing the gravitational waves, and also to determine that the signals come from space and are not from some other local phenomenon.

    To ensure absolute accuracy, the consortium of nearly 1,000 scientists from 16 countries spent several months carefully checking and re-checking the data before submitting their findings for publication.

    Christopher Moore, a PhD student from Cambridge’s Institute of Astronomy, was part of the discovery team who worked on the data analysis.

    “Since September, we’ve known that something was detected, but it took months of checking to confirm that it was actually gravitational waves,” he said. “This team has been looking for evidence of gravitational waves for decades – a huge amount of work has gone into it, and I feel incredibly lucky to be part of the team. This discovery will change the way we do astronomy.”

    Over coming years, the Advanced LIGO detectors will be ramped up to full power, increasing their sensitivity to gravitational waves, and in particular allowing more distant events to be measured. With the addition of further detectors, initially in Italy and later in other locations around the world, this first detection is surely just the beginning. UK scientists continue to contribute to the design and development of future generations of gravitational wave detectors.

    The UK Minister for Universities and Science, Jo Johnson MP, said: “Einstein’s theories from over a century ago are still helping us to understand our universe. Now that we have the technological capability to test his theories with the LIGO detectors his scientific brilliance becomes all the more apparent. The Government is increasing support for international research collaborations, and these scientists from across the UK have played a vital part in this discovery.”

    LIGO was originally proposed as a means of detecting these gravitational waves in the 1980s by Kip Thorne, Caltech’s Richard P. Feynman Professor of Theoretical Physics, Emeritus; Ronald Drever, professor of physics, emeritus also from Caltech; and Rainer Weiss, professor of physics, emeritus, from MIT.

    “The description of this observation is beautifully described in the Einstein theory of General Relativity formulated 100 years ago and comprises the first test of the theory in strong gravitation. It would have been wonderful to watch Einstein’s face had we been able to tell him,” said Weiss.

    “With this discovery, we humans are embarking on a marvelous new quest: the quest to explore the warped side of the universe—objects and phenomena that are made from warped spacetime. Colliding black holes and gravitational waves are our first beautiful examples,” said Thorne.

    The discovery was made possible by the enhanced capabilities of Advanced LIGO, a major upgrade that increases the sensitivity of the instruments compared to the first generation LIGO detectors, enabling a large increase in the volume of the universe probed—and the discovery of gravitational waves during its first observation run.

    The US National Science Foundation leads in financial support for Advanced LIGO. Funding organisations in Germany (Max Planck Society), the UK (Science and Technology Facilities Council, STFC) and Australia (Australian Research Council) also have made significant commitments to the project.

    Several of the key technologies that made Advanced LIGO so much more sensitive have been developed and tested by the German UK GEO collaboration. Significant computer resources have been contributed by the AEI Hannover Atlas Cluster, the LIGO Laboratory, Syracuse University, and the University of Wisconsin-Milwaukee.

    Several universities designed, built, and tested key components for Advanced LIGO: The Australian National University, the University of Adelaide, the University of Florida, Stanford University, Columbia University of New York, and Louisiana State University.

    Cambridge has a long-standing involvement in the field of gravitational wave science, and specifically with the LIGO experiment. Until recently these efforts were spearheaded by Dr Jonathan Gair, who left last year for a post at the University of Edinburgh and who has made significant contributions to a wide range of gravitational wave and LIGO science; he is one of the authors on the new paper. Several scientists in Cambridge are current members of the collaboration, including PhD students Christopher Moore and Alvin Chua from the Institute of Astronomy; Professor Anthony Lasenby and PhD student Sonke Hee from the Cavendish Laboratory and the Kavli Institute of Cosmology; and Professor Mike Hobson from the Cavendish Laboratory.  

    Further members of the collaboration until recently based at Cambridge, include Dr Philip Graff (author on the detection paper) and Dr Farhan Feroz, who, jointly with Mike Hobson and Anthony Lasenby, developed a machine learning method of analysis used currently within LIGO, as well as Dr Christopher Berry (author) and Dr Priscilla Canizares.

    These findings will be discussed at next month's Cambridge Science Festival during the open afternoon at the Institute of Astronomy.  

    B. P. Abbott et al. (LIGO Scientific Collaboration and Virgo Collaboration) 'Observation of Gravitational Waves from a Binary Black Hole Merger.' Physical Review Letters (2016). DOI: 10.1103/PhysRevLett.116.061102. 

    New window on the universe is opened with the observation of gravitational waves – ripples in spacetime – caused by the collision of two black holes. 

    I feel incredibly lucky to be part of the team - this discovery will change the way we do astronomy.
    Christopher Moore

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    When the numbers began to filter through from the spectrograph that was measuring small shifts in light from distant stars, Didier Queloz at first thought they were wrong. He certainly didn’t think he’d discovered an exoplanet. He checked and re-checked.

    “At some point I realised the only explanation could be that the numbers were right.”

    Today, many regard the discovery of 51 Pegasi b by Queloz and Professor Michel Mayor at the University of Geneva in 1995 as a moment in astronomy that forever changed the way we understand the universe and our place within it. It was the first confirmation of an exoplanet – a planet that orbits a star other than our Sun. Until then, although astronomers had speculated as to the existence of these distant worlds, no planet other than those in our own solar system had ever been found.

    “For centuries, we only had the one single example of our own solar system on which to base our knowledge of planets,” says Queloz, who moved to Cambridge’s Department of Physics two years ago. “If you wanted to understand botany, you wouldn’t build the botanic picture from one single flower – you need all the others.”

    Of the 1,900 or so confirmed exoplanets that have now been found – a tenth of these by Queloz himself – many are different to anything we ever imagined, challenging existing theories of planet formation.

    Fifty light years from Earth, the exoplanet 51 Peg resembles the gas giant Jupiter. But unlike our distant cousin, which is located in the further reaches of our solar system and takes 10 years to orbit the Sun, 51 Peg ‘hugs’ its sun, orbiting every four days. It’s been hailed as an example of a whole new class of ‘roaster planets’ or ‘Hot Jupiters’ and has prompted scientists to wonder if large planets are able to migrate closer to their suns over millions of years.

    “We are constantly surprised by the diversity of the other worlds,” says Queloz. Super-Earths like the volcanic planet 55 Cancri e with a temperature gradient across it of a thousand degrees; rogue planets like PSO J318.5-22, which roam freely between stars; Kepler-186f, which is lit by the light of a red star; and icy Kepler-16b with its double sunset. “For some, we don’t even have names to describe what they are.”

    But, as yet, no planet has been discovered that could be considered a twin of our own. “We are finding planets of a similar size and mass to Earth but nothing at the right temperature – so-called Goldilocks planetary systems in the habitable zone close enough to the sun to be warmed by it but not so close that the presence of water and life is a sheer impossibility,” explains Queloz.

    “Of course the question everyone would like to answer is whether there is life out there, because we are curious and we can’t resist – it’s how we are,” says Queloz.

    Queloz believes that a new era of terra hunting is fast approaching. “The past 20 years has seen a ‘brute force’ hunt for exoplanets. We are now confident that they are practically everywhere you look for them. To find an Earth twin, however, we need to look at specific planets for longer.”

    It’s not possible to see an exoplanet directly – it’s far too close to a blinding source of light, its star – so astronomers use two  techniques to look indirectly. Focusing on a star, they use NASA’s Kepler telescope to look for the dimming of starlight as the planet transits in front of it. From this, they calculate the planet’s size and temperature.

    The breakthrough that Queloz and Mayor pioneered was a technique to look for signs of ‘wobble’ caused by the gravitational pull exerted by the planet on the star as it orbits. The technique needed to be accurate enough to detect a wobble of only 10 m/s –  the speed of a running man. To put this in context, the Earth moves at the speed of 30,000 m/s.”

    Current technology works well for finding large exoplanets but to find planets the size of the Earth in the habitable zone astronomers need to look at smaller stars, and they need to overcome ‘stellar noise’, or natural variability in the data caused by physical motions of gas at the surface of the star.

    “This noise is slowing further progress but we believe that it can be overcome by careful analysis and by extending the length of time we are able to observe a planet for,” adds Queloz. “Intensive runs on a small number of stars where an observation is carried out every night for years is far more valuable than unevenly spaced data taken over years.”

    As techniques improve and with the launch of NASA's James Webb Space Telescope, astronomers will be able to ask whether what we understand as the basic molecules of life – carbon, oxygen and hydrogen – are present in the atmosphere of exoplanets, opening up the possibility of understanding their astrobiology and geophysics.

    “My feeling is that life will be found, although life like us may be extremely rare because otherwise we probably would have seen it by now,” he adds. “It may take a long time, and many scientists, to find life, but maybe that’s part of the fun – it would be too easy otherwise!”

    On the door of Queloz’s office is a spoof poster published by NASA in celebration of 20 years of exoplanet discoveries. Offering greetings from the Exoplanet Travel Bureau, it suggests 51 Pegasi b as a dream destination, or indeed “any planet you wish – as long as it’s far beyond our solar system.” Could this be reality one day? “It’s far too hard to say,” says Queloz. “But I would hope that sending a tiny probe of perhaps a few grams in weight might be possible in the next century.”

    At one stage in recent years, Queloz was almost finding an exoplanet a week. His terra hunting has slowed while he focuses on improving the equipment and techniques that he believes will help find an Earth twin. But the excitement never goes away, he says. “I must admit that every time I find a planet I feel like a child – it’s a surprise because it’s a new system. I used to joke with people asking me about sci-fi – the reality is far more exciting and diverse than any sci-fi movie you can imagine!”

    Inset images: top: Didier Queloz; bottom: 'travel' poster by NASA /JPL-Caltech


    Other worlds: Professor Didier Queloz and Dr William Bains consider what life might be like under the light of other suns at the Cambridge Science Festival on 17 March 2016

    Twenty years ago, in Geneva, PhD student Didier Queloz discovered a planet orbiting another sun – something that astronomers had predicted, but never found. Today he continues his terra hunting for extreme worlds and Earth twins in Cambridge.

    We are constantly surprised by the diversity of the other worlds.
    Didier Queloz
    Artist’s impression of a super-Earth exoplanet orbiting its nearby star

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    Scientists have discovered that a highly promising group of materials known as hybrid lead halide perovskites can recycle light – a finding that they believe could lead to large gains in the efficiency of solar cells.

    Hybrid lead halide perovskites are a particular group of synthetic materials which have been the subject of intensive scientific research, as they appear to promise a revolution in the field of solar energy. As well as being cheap and easy to produce, perovskite solar cells have, in the space of a few years, become almost as energy-efficient as silicon – the material currently used in most household solar panels.

    By showing that they can also be optimised to recycle light, the new study suggests that this could just be the beginning. Solar cells work by absorbing photons from the sun to create electrical charges, but the process also works in reverse, because when the electrical charges recombine, they can create a photon. The research shows that perovskite cells have the extra ability to re-absorb these regenerated photons – a process known as “photon recycling”. This creates a concentration effect inside the cell, as if a lens has been used to focus lots of light in a single spot.

    According to the researchers, this ability to recycle photons could be exploited with relative ease to create cells capable of pushing the limits of energy efficiency in solar panels.

    The study builds on an established collaboration, focusing on the use of these materials not only in solar cells but also in light-emitting diodes, and was carried out in the group of Richard Friend, Cavendish Professor of Physics and Fellow of St John’s College at the University of Cambridge. The research was undertaken in partnership with the team of Henry Snaith at the University of Oxford and Bruno Ehrler at the FOM Institute, AMOLF, Amsterdam.

    Felix Deschler, who is one of the corresponding authors of the study and works with a team studying perovskites at the Cavendish Laboratory, said: “It’s a massive demonstration of the quality of this material and opens the door to maximising the efficiency of solar cells. The fabrication methods that would be required to exploit this phenomenon are not complicated, and that should boost the efficiency of this technology significantly beyond what we have been able to achieve until now.”

    Perovskite-based solar cells were first tested in 2012, and were so successful that in 2013, Science Magazine rated them one of the breakthroughs of the year.

    Since then, researchers have made rapid progress in improving the efficiency with which these cells convert light into electrical energy. Recent experiments have produced power conversion efficiencies of around 20% - a figure already comparable with silicon cells.

    By showing that perovskite-based cells can also recycle photons, the new research suggests that they could reach efficiencies well beyond this.

    The study, which is reported in Science, involved shining a laser on to one part of a 500 nanometre-thick sample of lead-iodide perovskite. Perovskites emit light when they come into contact with it, so the team was able to measure photon activity inside the sample based on the light it emitted.

    Close to where the laser light had shone on to the film, the researchers detected a near-infrared light emission. Crucially, however, this emission was also detected further away from the point where the laser hit the sample, together with a second emission composed of lower-energy photons.

    “The low-energy component enables charges to be transported over a long distance, but the high-energy component could not exist unless photons were being recycled,” Luis Miguel Pazos Outón, lead author on the study, said. “Recycling is a quality that materials like silicon simply don’t have. This effect concentrates a lot of charges within a very small volume. These are produced by a combination of incoming photons and those being made within the material itself, and that’s what enhances its energy efficiency.”

    As part of the study, Pazos Outón also manufactured the first demonstration of a perovskite-based back-contact solar cell. This single cell proved capable of transporting an electrical current more than 50 micrometres away from the contact point with the laser; a distance far greater than the researchers had predicted, and a direct result of multiple photon recycling events taking place within the sample.

    The researchers now believe that perovskite solar cells, may be able to reach considerably higher efficiencies than they have to date. “The fact that we were able to show photon recycling happening in our own cell, which had not been optimised to produce energy, is extremely promising,” Richard Friend, a corresponding author, said. “If we can harness this it would lead to huge gains in terms of energy efficiency.”

    Perovskite materials can recycle light particles – a finding which could lead to a new generation of affordable, high-performance solar cells.

    It’s a massive demonstration of the quality of this material and opens the door to maximising the efficiency of solar cells
    Felix Deschler
    Depiction of photon recycling inside the crystalline structure of perovskite.

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    An international team of astronomers, led by the University of Cambridge, has obtained the most detailed ‘fingerprint’ of a rocky planet outside our solar system to date, and found a planet of two halves: one that is almost completely molten, and the other which is almost completely solid.

    According to the researchers, conditions on the hot side of the planet are so extreme that it may have caused the atmosphere to evaporate, with the result that conditions on the two sides of the planet vary widely: temperatures on the hot side can reach 2500 degrees Celsius, while temperatures on the cool side are around 1100 degrees. The results are reported in the journal Nature.

    Using data from NASA’s Spitzer Space Telescope, the researchers examined a planet known as 55 Cancri e, which orbits a sun-like star located 40 light years away in the Cancer constellation, and have mapped how conditions on the planet change throughout a complete orbit, the first time this has been accomplished for such a small planet. 

    55 Cancri e is a ‘super Earth’: a rocky exoplanet about twice the size and eight times the mass of Earth, and orbits its parent star so closely that a year lasts just 18 hours. The planet is also tidally locked, meaning that it always shows the same face to its parent star, similar to the Moon, so there is a permanent ‘day’ side and a ‘night’ side. Since it is among the nearest super Earths whose composition can be studied, 55 Cancri e is among the best candidates for detailed observations of surface and atmospheric conditions on rocky exoplanets.

    Uncovering the characteristics of super Earths is difficult, since they are so small compared to the parent star and their contrast relative to the star is extremely small compared to larger, hotter gas giant planets, the so-called ‘hot Jupiters’.

    “We haven’t yet found any other planet that is this small and orbits so close to its parent star, and is relatively close to us, so 55 Cancri e offers lots of possibilities,” said Dr Brice-Olivier Demory of the University’s Cavendish Laboratory, the paper’s lead author. “We still don’t know exactly what this planet is made of – it’s still a riddle. These results are like adding another brick to the wall, but the exact nature of this planet is still not completely understood.”

    55 Cancri e has been extensively studied since it was discovered in 2011. Based on readings taken at different points in time, it was thought to be a water world, or even made of diamond, but researchers now believe that it is almost completely covered by lava.

    “We have entered a new era of atmospheric remote sensing of rocky exoplanets,” said study co-author Dr Nikku Madhusudhan, from the Institute of Astronomy at Cambridge. “It is incredible that we are now able to measure the large scale temperature distribution on the surface of a rocky exoplanet.”

    Based on these new infrared measurements, the ‘day’ side of the planet appears to be almost completely molten, while the ‘night’ side is almost completely solid. The heat from the day side is not efficiently circulated to the night side, however. On Earth, the atmosphere aids in the recirculation of heat, keeping the temperature across the whole planet within a relatively narrow range. But on 55 Cancri e, the hot side stays hot, and the cold side stays cold.

    According to Demory, one possibility for this variation could be either a complete lack of atmosphere, or one which has been partially destroyed due to the strong irradiation from the nearby host star. “On the day side, the temperature is around 2500 degrees Celsius, while on the night side it’s about 1100 degrees – that’s a huge difference,” he said. “We think that there could still be an atmosphere on the night side, but temperatures on the day side are so extreme that the atmosphere may have evaporated completely, meaning that heat is not being efficiently transferred, or transferred at all from the day side to the night side.”

    Another possibility for the huge discrepancy between the day side and the night side may be that the molten lava on the day side moves heat along the surface, but since lava is mostly solid on the night side, heat is not moved around as efficiently.

    What is unclear however, is where exactly the ‘extra’ heat on 55 Cancri e comes from in the first place, since the observations reveal an unknown source of heat that makes the planet hotter than expected solely from the irradiation from the star – but the researchers may have to wait until the next generation of space telescopes are launched to find out.

    For Demory, these new readings also show just how difficult it will be to detect a planet that is similar to Earth. The smaller a planet is, the more difficult it is to detect. And once a rocky planet has been found, there is the question of whether it lies in the so-called habitable zone, where life can be supported. “The problem is, people don’t agree on what the habitable zone is,” said Demory. “For example, some studies consider Mars and Venus to be in the habitable zone, but life as we know it is not possible on either of those planets. Understanding the surface and climate properties of these other worlds will eventually allow us to put the Earth’s climate and habitability into context.”

    One possibility might be to look at stars which are much cooler and smaller than our sun, such as the M-dwarfs, which would mean that planets could be much closer to their star and still be in the habitable zone. The sizes of such planets relative to their star would be larger, which make them more detectable from Earth.

    But for the time being, Demory and his colleagues plan to keep studying 55 Cancri e, in order to see what other secrets it might hold, including the possibility that it might be surrounded by a torus of gas and dust, which could account for some of the variations in the data. And in 2018, the successor to Hubble and Spitzer, the James Webb Space Telescope, will launch, allowing astronomers to look at planets outside our solar system with entirely new levels of precision.

    Brice-Olivier Demory et al. ‘A map of the extreme day-night temperature gradient of a super-Earth exoplanet.’ Nature (2016). DOI: 10.1038/nature17169

    The most detailed map of a small, rocky ‘super Earth’ to date reveals a planet almost completely covered by lava, with a molten ‘hot’ side and solid ‘cool’ side.

    We still don’t know exactly what this planet is made of – it’s still a riddle. These results are like adding another brick to the wall, but the exact nature of this planet is still not completely understood.
    Brice-Olivier Demory
    Illustration of the hot lava world 55 Cancri e

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    An international team of researchers have found evidence of a mysterious new state of matter, first predicted 40 years ago, in a real material. This state, known as a quantum spin liquid, causes electrons – thought to be indivisible building blocks of nature – to break into pieces.

    The researchers, including physicists from the University of Cambridge, measured the first signatures of these fractional particles, known as Majorana fermions, in a two-dimensional material with a structure similar to graphene. Their experimental results successfully matched with one of the main theoretical models for a quantum spin liquid, known as a Kitaev model. The results are reported in the journal Nature Materials.

    Quantum spin liquids are mysterious states of matter which are thought to be hiding in certain magnetic materials, but had not been conclusively sighted in nature.

    The observation of one of their most intriguing properties — electron splitting, or fractionalisation — in real materials is a breakthrough. The resulting Majorana fermions may be used as building blocks of quantum computers, which would be far faster than conventional computers and would be able to perform calculations that could not be done otherwise.

    “This is a new quantum state of matter, which has been predicted but hasn’t been seen before,” said Dr Johannes Knolle of Cambridge’s Cavendish Laboratory, one of the paper’s co-authors.

    In a typical magnetic material, the electrons each behave like tiny bar magnets. And when a material is cooled to a low enough temperature, the ‘magnets’ will order themselves over long ranges, so that all the north magnetic poles point in the same direction, for example.

    But in a material containing a spin liquid state, even if that material is cooled to absolute zero, the bar magnets would not align but form an entangled soup caused by quantum fluctuations.

    “Until recently, we didn’t even know what the experimental fingerprints of a quantum spin liquid would look like,” said paper co-author Dr Dmitry Kovrizhin, also from the Theory of Condensed Matter group of the Cavendish Laboratory. “One thing we’ve done in previous work is to ask, if I were performing experiments on a possible quantum spin liquid, what would I observe?”

    Knolle and Kovrizhin’s co-authors, led by Dr Arnab Banerjee and Dr Stephen Nagler from Oak Ridge National Laboratory in the US, used neutron scattering techniques to look for experimental evidence of fractionalisation in alpha-ruthenium chloride (α-RuCl3). The researchers tested the magnetic properties of α-RuCl3 powder by illuminating it with neutrons, and observing the pattern of ripples that the neutrons produced on a screen when they scattered from the sample.

    A regular magnet would create distinct sharp lines, but it was a mystery what sort of pattern the Majorana fermions in a quantum spin liquid would make. The theoretical prediction of distinct signatures by Knolle and his collaborators in 2014 match well with the broad humps instead of sharp lines which experimentalists observed on the screen, providing for the first time direct evidence of a quantum spin liquid and the fractionalisation of electrons in a two dimensional material.

    “This is a new addition to a short list of known quantum states of matter,” said Knolle.

    “It’s an important step for our understanding of quantum matter,” said Kovrizhin. “It’s fun to have another new quantum state that we’ve never seen before – it presents us with new possibilities to try new things.”

    A. Banerjee et al. ‘Proximate Kitaev quantum spin liquid behaviour in a honeycomb magnet.’ Nature Materials (2016). DOI: 10.1038/nmat4604

    Researchers have observed the ‘fingerprint’ of a mysterious new quantum state of matter in a two-dimensional material, in which electrons break apart.

    It’s an important step for our understanding of quantum matter.
    Dmitry Kovrizhin
    Excitation of a spin liquid on a honeycomb lattice with neutrons.

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    A centrepiece for industrial partnership with the physical sciences and engineering officially opens today. The building will be opened by David Harding, whose generous sponsorship of the Physics of Sustainability programme was central to the funding of the Maxwell Centre project by HEFCE.

    In addition, the centre will foster advanced scientific computing, materials science research, nanoscience and biophysics.

    Hosted by the Cavendish Laboratory, the Centre provides facilities for the University of Cambridge’s Science and Technology campus as well as collaborators from industry, with offices, laboratory and meeting spaces for more than 230 people.

    It will house researchers from the University’s Physics, Chemistry, Chemical Engineering and Biotechnology, Engineering, and Material Sciences and Metallurgy departments. It is also a home to two EPSRC (Engineering and Physical Sciences Research Council) Centres for Doctoral Training, the SKF University Technology Centre, the Energy@Cambridge Initiative and connects to several other Cambridge Strategic Research Initiatives and Networks.

    The Maxwell Centre is due to become the Cambridge satellite centre for the Sir Henry Royce Institute for Advanced Materials Research, and will also host the partnership between ARM and University of Cambridge. The latter collaboration will research new technologies that ensure data-intensive computing can be delivered within the constrained energy budgets governing many compute applications.

    Director of the Centre, Professor Sir Richard Friend, said: “The Centre will translate ‘blue skies’ research into products vital for industry.

    “The co-location of academics and industry supports a two-way flow of ideas.  New research opportunities are often revealed by industrial activity, their solutions require transfer of ideas and techniques often from fields well away from the industry.

    “It demonstrates our commitment to collaborating with industry, large and small, through intellectual innovation.”

    Professor Sir Leszek Borysiewicz, Vice-Chancellor of the University of Cambridge, said: "The Maxwell Centre significantly strengthens our drive to deliver new knowledge and applications for industry, underpinning growth and fostering our innovative partnerships between research and business.

    “This builds on established efforts to embed industrial engagement still further into the University, driving forward real excellence in translational research.”

    The Centre will take forward research activity currently supported by the Winton Programme for the Physics of Sustainability at the Cavendish Laboratory, where the focus has been on original, risk-taking science since its inception in March 2011.

    David Harding, Founder and CEO of Winton Capital, and an alumnus of the Physics Department, gave £20 million to the Cavendish Laboratory in 2011 to establish the Winton Programme, providing the freedom to explore basic science that could generate the much needed breakthroughs for the resource-strained world.

    The Centre is named after physicist James Clerk Maxwell, who was appointed the first Professor of Experimental Physics at Cambridge in 1871 and who discovered electromagnetism and founded statistical mechanics.

    It is located between the Physics of Medicine building and the William Gates building on the West Cambridge Physical Science and Technology campus.

    The £26 million Maxwell Centre will focus on “blue skies” research in areas such as efficient energy generation, storage and use, including work on photovoltaics, energy storage, refrigeration, lighting and ICT.

    The Maxwell Centre significantly strengthens our drive to deliver new knowledge and applications for industry, underpinning growth and fostering our innovative partnerships between research and business.
    Professor Sir Leszek Borysiewicz, Vice-Chancellor of the University of Cambridge
    Maxwell Centre

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    A project which aims to establish the UK as an international leader in the development of “superconducting spintronics” – technology that could significantly increase the energy-efficiency of data centres and high-performance computing – has been announced.

    Led by researchers at the University of Cambridge, the “Superspin” project aims to develop prototype devices that will pave the way for a new generation of ultra-low power supercomputers, capable of processing vast amounts of data, but at a fraction of the huge energy consumption of comparable facilities at the moment.

    As more economic and cultural activity moves online, the data centres which house the servers needed to handle internet traffic are consuming increasing amounts of energy. An estimated three per cent of power generated in Europe is, for example, already used by data centres, which act as repositories for billions of gigabytes of information.

    Superconducting spintronics is a new field of scientific investigation that has only emerged in the last few years. Researchers now believe that it could offer a pathway to solving the energy demands posed by high performance computing.

    As the name suggests, it combines superconducting materials – which can carry a current without losing energy as heat – with spintronic devices. These are devices which manipulate a feature of electrons known as their “spin”, and are capable of processing large amounts of information very quickly.

    Given the energy-efficiency of superconductors, combining the two sounds like a natural marriage, but until recently it was also thought to be completely impossible. Most spintronic devices have magnetic elements, and this magnetism prevents superconductivity, and hence reduces any energy-efficiency benefits.

    Stemming from the discovery of spin polarized supercurrents in 2010 at the University of Cambridge, recent research, along with that of other institutions, has however shown that it is possible to power spintronic devices with a superconductor. The aim of the new £2.7 million project, which is being funded by the Engineering and Physical Sciences Research Council, is to use this as the basis for a new style of computing architecture.

    Although work is already underway in several other countries to exploit superconducting spintronics, the Superspin project is unprecedented in terms of its magnitude and scope.

    Researchers will explore how the technology could be applied in future computing as a whole, examining fundamental problems such as spin generation and flow, and data storage, while also developing sample devices. According to the project proposal, the work has the potential to establish Britain as a leading centre for this type of research and “ignite a technology field.”

    The project will be led by Professor Mark Blamire, Head of the Department of Materials Sciences at the University of Cambridge, and Dr Jason Robinson, University Lecturer in Materials Sciences, Fellow of St John’s College, University of Cambridge, and University Research Fellow of the Royal Society. They will work with partners in the University’s Cavendish Laboratory (Dr Andrew Ferguson) and at Royal Holloway, London (Professor Matthias Eschrig).

    Blamire and Robinson’s core vision of the programme is “to generate a paradigm shift in spin electronics, using recent discoveries about how superconductors can be combined with magnetism.” The programme will provide a pathway to making dramatic improvements in computing energy efficiency.

    Robinson added: “Many research groups have recognised that superconducting spintronics offer extraordinary potential because they combine the properties of two traditionally incompatible fields to enable ultra-low power digital electronics.”

    “However, at the moment, research programmes around the world are individually studying fascinating basic phenomena, rather than looking at developing an overall understanding of what could actually be delivered if all of this was joined up. Our project will aim to establish a closer collaboration between the people doing the basic science, while also developing demonstrator devices that can turn superconducting spintronics into a reality.”

    The initial stages of the five-year project will be exploratory, examining different ways in which spin can be transported and magnetism controlled in a superconducting state. By 2021, however, the team hope that they will have manufactured sample logic and memory devices – the basic components that would be needed to develop a new generation of low-energy computing technologies.

    The project will also report to an advisory board, comprising representatives from several leading technology firms, to ensure an ongoing exchange between the researchers and industry partners capable of taking its results further.

    “The programme provides us with an opportunity to take international leadership of this as a technology, as well as in the basic science of studying and improving the interaction between superconductivity and magnetism,” Blamire said. “Once you have grasped the physics behind the operation of a sample device, scaling up from the sort of models that we are aiming to develop is not, in principle, too taxing.”

    A Cambridge-led project aiming to develop a new architecture for future computing based on superconducting spintronics - technology designed to increase the energy-efficiency of high-performance computers and data storage - has been announced.

    Superconducting spintronics offer extraordinary potential because they combine the properties of two traditionally incompatible fields to enable ultra-low power digital electronics
    Jason Robinson
    Growing quantities of data storage online are driving up the energy costs of high-performance computing and data centres. Superconducting spintronics offer a potential means of significantly increasing their energy-efficiency to resolve this problem.

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    Researchers have developed the world’s tiniest engine – just a few billionths of a metre in size – which uses light to power itself. The nanoscale engine, developed by researchers at the University of Cambridge, could form the basis of future nano-machines that can navigate in water, sense the environment around them, or even enter living cells to fight disease.

    The prototype device is made of tiny charged particles of gold, bound together with temperature-responsive polymers in the form of a gel. When the ‘nano-engine’ is heated to a certain temperature with a laser, it stores large amounts of elastic energy in a fraction of a second, as the polymer coatings expel all the water from the gel and collapse. This has the effect of forcing the gold nanoparticles to bind together into tight clusters. But when the device is cooled, the polymers take on water and expand, and the gold nanoparticles are strongly and quickly pushed apart, like a spring. The results are reported in the journal PNAS.

    “It’s like an explosion,” said Dr Tao Ding from Cambridge’s Cavendish Laboratory, and the paper’s first author. “We have hundreds of gold balls flying apart in a millionth of a second when water molecules inflate the polymers around them.”

    “We know that light can heat up water to power steam engines,” said study co-author Dr Ventsislav Valev, now based at the University of Bath. “But now we can use light to power a piston engine at the nanoscale.”

    Nano-machines have long been a dream of scientists and public alike, but since ways to actually make them move have yet to be developed, they have remained in the realm of science fiction. The new method developed by the Cambridge researchers is incredibly simple, but can be extremely fast and exert large forces.

    The forces exerted by these tiny devices are several orders of magnitude larger than those for any other previously produced device, with a force per unit weight nearly a hundred times better than any motor or muscle. According to the researchers, the devices are also bio-compatible, cost-effective to manufacture, fast to respond, and energy efficient.

    Professor Jeremy Baumberg from the Cavendish Laboratory, who led the research, has named the devices ‘ANTs’, or actuating nano-transducers. “Like real ants, they produce large forces for their weight. The challenge we now face is how to control that force for nano-machinery applications.”

    The research suggests how to turn Van de Waals energy – the attraction between atoms and molecules – into elastic energy of polymers and release it very quickly. “The whole process is like a nano-spring,” said Baumberg. “The smart part here is we make use of Van de Waals attraction of heavy metal particles to set the springs (polymers) and water molecules to release them, which is very reversible and reproducible.”

    The team is currently working with Cambridge Enterprise, the University’s commercialisation arm, and several other companies with the aim of commercialising this technology for microfluidics bio-applications.

    The research is funded as part of a UK Engineering and Physical Sciences Research Council (EPSRC) investment in the Cambridge NanoPhotonics Centre, as well as the European Research Council (ERC).

    Tao Ding et al. ‘Light-induced actuating nanotransducers.’ PNAS (2016). DOI: 10.1073/pnas.1524209113

    Researchers have built a nano-engine that could form the basis for future applications in nano-robotics, including robots small enough to enter living cells.

    Like real ants, they produce large forces for their weight.
    Jeremy Baumberg
    Expanding polymer-coated gold nanoparticles

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    An international team of astronomers has discovered three planets orbiting an ultracool dwarf star just 40 light years from Earth. These worlds have sizes and temperatures similar to those of Venus and Earth and may be the best targets found so far for the search for life outside the Solar System. They are the first planets ever discovered around such a tiny and dim star. The results are reported in the journal Nature.

    Using the TRAPPIST telescope at the European Southern Observatory’s (ESO) La Silla Observatory in Chile, the astronomers observed the star 2MASS J23062928-0502285, now also known as TRAPPIST-1, and located in the Aquarius constellation. They found that this dim and cool star faded slightly at regular intervals, indicating that several objects were transiting, or passing between the star and the Earth. Detailed analysis showed that three planets with similar sizes to the Earth were present.

    TRAPPIST-1 is an ultracool dwarf star — much cooler and redder than the Sun and barely larger than Jupiter. Such stars are very common in the Milky Way and very long-lived, but this is the first time that planets have been found around one of them. Despite being so close to the Earth, this star is too dim and too red to be seen with the naked eye or even with a large amateur telescope.

    “The discovery of a planetary system around such a small star opens up a brand new avenue for research,” said Professor Didier Queloz from the University of Cambridge’s Cavendish Laboratory, the paper’s senior author. “Before this discovery it was not at all clear whether such a small star could host an Earth-sized planet. Nobody had seriously studied it, but now that’s likely to change.”

    “Systems around these tiny stars are the only places where we can detect life on an Earth-sized exoplanet with our current technology,” said the paper’s lead author Michaël Gillon, from the University of Liège in Belgium. “So if we want to find life elsewhere in the Universe, this is where we should start to look.”

    Astronomers will search for signs of life by studying the effect that the atmosphere of a transiting planet has on the light reaching Earth. For Earth-sized planets orbiting stars similar to our Sun this tiny effect is swamped because of the large size ratio between the planet and the star. Only for the case of faint red ultra-cool dwarf stars — like TRAPPIST-1 — is this effect big enough to be detected.

    Follow-up observations with larger telescopes have shown that the planets orbiting TRAPPIST-1 have sizes very similar to Earth. Two of the planets complete an orbit of the star in 1.5 days and 2.4 days respectively, and the third planet has a less well determined orbital period in the range of 4.5 to 73 days.

    “With such short orbital periods, the planets are between 20 and 100 times closer to their star than the Earth to the Sun,” said Gillon. “The structure of this planetary system is much more similar in scale to the system of Jupiter’s moons than to that of the Solar System.”

    Although they orbit very close to their host dwarf star, the inner two planets only receive four and two times, respectively, the amount of radiation received by the Earth, because their star is much fainter than the Sun. That puts them closer to the star than the habitable zone for this system. The third, outer, planet’s orbit is not yet well known – it probably receives less radiation than the Earth does, but perhaps still enough to lie within the habitable zone.

    The next generation of giant telescopes, such as NASA’s James Webb Telescope due to launch in 2018, will allow researchers to study the atmospheric composition of these planets and to explore them first for water, and then for traces of biological activity.

    “While this is not the first time that planets have been found in the habitable zone of a star, the TRAPPIST-1 system provides humanity with our first opportunity to remotely explore Earth-like environments and empirically determine their suitability for life,” said study co-author Dr Amaury Triaud from Cambridge’s Institute of Astronomy. “Because the system contains many planets, we will even be able to compare the climates of each to one another and to the Earth’s.”

    This work opens up a new direction for exoplanet hunting, as around 15% of the stars near to the Sun are ultra-cool dwarf stars, and it also serves to highlight that the search for exoplanets has now entered the realm of potentially habitable cousins of the Earth. The TRAPPIST survey is a prototype for a more ambitious project called SPECULOOS that will be installed at ESO’s Paranal Observatory in Chile.

    Michaël Gillon et al. ‘Temperate Earth-sized planets transiting a nearby ultracool dwarf star.’ Nature (2016). DOI: 10.1038/nature17448

    ​Adapted from an ESO press release. 

    Three Earth-sized planets have been discovered orbiting a dim and cool star, and may be the best place to search for life beyond the Solar System.

    The discovery of a planetary system around such a small star opens up a brand new avenue for research.
    Didier Queloz
    Artist’s impression of the ultracool dwarf star TRAPPIST-1 from the surface of one of its planets.

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    The team, led by the University of Cambridge, have invented a way to make such sheets on industrial scales, opening up applications ranging from smart clothing for people or buildings, to banknote security.

    Using a new method called Bend-Induced-Oscillatory-Shearing (BIOS), the researchers are now able to produce hundreds of metres of these materials, known as ‘polymer opals’, on a roll-to-roll process. The results are reported in the journal Nature Communications.

    Some of the brightest colours in nature can be found in opal gemstones, butterfly wings and beetles. These materials get their colour not from dyes or pigments, but from the systematically-ordered microstructures they contain.

    The team behind the current research, based at Cambridge’s Cavendish Laboratory, have been working on methods of artificially recreating this ‘structural colour’ for several years, but to date, it has been difficult to make these materials using techniques that are cheap enough to allow their widespread use.

    In order to make the polymer opals, the team starts by growing vats of transparent plastic nano-spheres. Each tiny sphere is solid in the middle but sticky on the outside. The spheres are then dried out into a congealed mass. By bending sheets containing a sandwich of these spheres around successive rollers the balls are magically forced into perfectly arranged stacks, by which stage they have intense colour.

    By changing the sizes of the starting nano-spheres, different colours (or wavelengths) of light are reflected. And since the material has a rubber-like consistency, when it is twisted and stretched, the spacing between the spheres changes, causing the material to change colour. When stretched, the material shifts into the blue range of the spectrum, and when compressed, the colour shifts towards red. When released, the material returns to its original colour. Such chameleon materials could find their way into colour-changing wallpapers, or building coatings that reflect away infrared thermal radiation.

    “Finding a way to coax objects a billionth of a metre across into perfect formation over kilometre scales is a miracle,” said Professor Jeremy Baumberg, the paper’s senior author. “But spheres are only the first step, as it should be applicable to more complex architectures on tiny scales.”

    In order to make polymer opals in large quantities, the team first needed to understand their internal structure so that it could be replicated. Using a variety of techniques, including electron microscopy, x-ray scattering, rheology and optical spectroscopy, the researchers were able to see the three-dimensional position of the spheres within the material, measure how the spheres slide past each other, and how the colours change.

    “It’s wonderful to finally understand the secrets of these attractive films,” said PhD student Qibin Zhao, the paper’s lead author.

    Cambridge Enterprise, the University’s commercialisation arm which is helping to commercialise the material, has been contacted by more than 100 companies interested in using polymer opals, and a new spin-out Phomera Technologies has been founded. Phomera will look at ways of scaling up production of polymer opals, as well as selling the material to potential buyers. Possible applications the company is considering include coatings for buildings to reflect heat, smart clothing and footwear, or for banknote security and packaging applications.

    The research is funded as part of a UK Engineering and Physical Sciences Research Council (EPSRC) investment in the Cambridge NanoPhotonics Centre, as well as the European Research Council (ERC).

    Q. Zhao et al. “Large-scale ordering of nanoparticles using viscoelastic shear processing”, Nature Communications (2016); DOI: 10.1038/ncomms11661

    Researchers have devised a new method for stacking microscopic marbles into regular layers, producing intriguing materials which scatter light into intense colours, and which change colour when twisted or stretched.

    Finding a way to coax objects a billionth of a metre across into perfect formation over kilometre scales is a miracle.
    Jeremy Baumberg
    Polymer Opals

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    When a molecule emits a blink of light, it doesn’t expect it to ever come back. However researchers have now managed to place single molecules in such a tiny optical cavity that emitted photons, or particles of light, return to the molecule before they have properly left. The energy oscillates back and forth between light and molecule, resulting in a complete mixing of the two.

    Previous attempts to mix molecules with light have been complex to produce and only achievable at very low temperatures, but the researchers, led by the University of Cambridge, have developed a method to produce these ‘half-light’ molecules at room temperature.

    These unusual interactions of molecules with light provide new ways to manipulate the physical and chemical properties of matter, and could be used to process quantum information, aid in the understanding of complex processes at work in photosynthesis, or even manipulate the chemical bonds between atoms. The results are reported in the journal Nature.

    To use single molecules in this way, the researchers had to reliably construct cavities only a billionth of a metre (one nanometre) across in order to trap light. They used the tiny gap between a gold nanoparticle and a mirror, and placed a coloured dye molecule inside.

    “It’s like a hall of mirrors for a molecule, only spaced a hundred thousand times thinner than a human hair,” said Professor Jeremy Baumberg of the NanoPhotonics Centre at Cambridge’s Cavendish Laboratory, who led the research.

    In order to achieve the molecule-light mixing, the dye molecules needed to be correctly positioned in the tiny gap. “Our molecules like to lie down flat on the gold, and it was really hard to persuade them to stand up straight,” said Rohit Chikkaraddy, lead author of the study.

    To solve this, the team joined with a team of chemists at Cambridge led by Professor Oren Scherman to encapsulate the dyes in hollow barrel-shaped molecular cages called cucurbiturils, which are able to hold the dye molecules in the desired upright position.

    When assembled together correctly, the molecule scattering spectrum splits into two separated quantum states which is the signature of this ‘mixing’. This spacing in colour corresponds to photons taking less than a trillionth of a second to come back to the molecule.

    A key advance was to show strong mixing of light and matter was possible for single molecules even with large absorption of light in the metal and at room temperature. “Finding single-molecule signatures took months of data collection,” said Chikkaraddy.

    The researchers were also able to observe steps in the colour spacing of the states corresponding to whether one, two, or three molecules were in the gap.

    The Cambridge team collaborated with theorists Professor Ortwin Hess at the Blackett Laboratory, Imperial College London and Dr Edina Rosta at Kings College London to understand the confinement and interaction of light in such tiny gaps, matching experiments amazingly well.

    The research is funded as part of a UK Engineering and Physical Sciences Research Council (EPSRC) investment in the Cambridge NanoPhotonics Centre, as well as the European Research Council (ERC), the Winton Programme for the Physics of Sustainability and St John’s College.

    Rohit Chikkaraddy et al. ‘Single-molecule strong coupling at room temperature in plasmonic nanocavities.’ Nature (2016). DOI: 10.1038/nature17974

    Researchers have successfully used quantum states to mix a molecule with light at room temperature, which will aid in the exploration of quantum technologies and provide new ways to manipulate the physical and chemical properties of matter.

    It’s like a hall of mirrors for a molecule, only spaced a hundred thousand times thinner than a human hair.
    Jeremy Baumberg
    Mixing light with dye molecules, trapped in golden gaps

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  • 06/28/16--02:28: A Quantum Leap
  • Developing new materials – or improving existing ones – is a time-consuming process of trial and error. Thanks to CASTEP, software developed at Cambridge and based on quantum mechanics is taking the guess work out of R&D.

    Material world

    Making materials better is a key part of technology innovation, but doing so often takes decades. Now, software based on quantum mechanics and originally developed by physicists at Cambridge is helping R&D teams speed up the search for new materials. Called CASTEP, the modelling code is widely used in many industries – from chemical and semiconductor manufacture to oil and gas.

    CASTEP has been licensed to Cambridge-based software company Accelrys – now BIOVIA – since 1995 and in 2013 passed $30m in sales.

    Used in tandem with ‘real’ experiments, the ‘virtual’ experiments that CASTEP enables mean that as well as boosting efficiency of the R&D process, the code can help pinpoint sources of product failures.

    Key to its widespread use is its accessibility: the code’s interface means it can be used by any academic or bench-top scientist, allowing its adoption across many industries. UK academics can use the code for free; as a result, hundreds of peer-reviewed papers based on CASTEP calculations are published every year.

    An academy of sceptics

    From better solar cells to more efficient catalysts, technological innovation is often based on materials. Traditionally, development of better materials has been based on trial and error, a process of incremental improvement that can take decades to deliver.

    Computation and simulation are drivers of economic growth, so models that reliably describe materials, and which can be used alongside ‘real’ experiments, would o er many advantages to many industries.

    In theory, the part of quantum mechanics known as density functional theory should be able to describe anything from a single atom of silicon to a Boeing 747. However, quantum mechanical equations for things more complex than a single particle are hugely complex.

    When Professor Mike Payne joined the field in the 1980s, quantum mechanics could describe nothing more complex than two atoms of silicon, and the scientific world was sceptical that density functional theory would ever have relevance outside academia.

    Breakthroughs in quantum mechanics and density functional theory, however, transformed the  field and paved the way for CASTEP.

    Rigorous, robust and reliable

    Breakthroughs in quantum mechanics and density functional theory meant the methods Payne had pioneered were capable of modelling not just a few atoms, but many atoms across the Periodic Table.

    As well as playing a key role in the underlying physics, Payne and CASTEP’s other developers were early adopters of parallel computing, giving the software the memory it needed to perform its complex calculations on very large systems containing hundreds of atoms.

    The code was completely re-written – by six researchers in their spare time – between 2000 and 2003.

    Because it is a full-featured material modelling code based on a first-principles quantum mechanical description of electrons and nuclei, CASTEP helps R&D teams understand very complicated problems.

    Used alongside ‘real’ experiments, the ‘virtual’ experiments that CASTEP performs means R&D teams can model anything based on atoms, understand how it works – and then generate ideas about how to improve it.

    Future directions

    Already used by catalyst companies to gain a clearer understanding of how catalysts work – and therefore how best to improve them – and by the semiconductor industry as a tool to diagnose the source of impurities in the manufacturing process, a major area of potential growth for CASTEP is in the pharmaceutical sector.

    Pharmaceutical firms rely on patents to protect the large sums of money they invest in developing new drugs. Patenting the right crystal structure, however, is key.

    Combined with solid-state NMR, CASTEP can ensure all active crystal structures are identified and protected.


    Computation and simulation are drivers of economic growth

    Professor Mike Payne, Cavendish Laboratory

    Over and over again people told us what we couldn’t do with this methodology; over and over again we proved them wrong

    Professor Mike Payne, Cavendish Laboratory

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  • 06/28/16--02:36: From Lab to Fab
  • Two decades after spinning out from Cambridge’s Cavendish Laboratory, Cavendish Kinetics is seeing years of research into quantum physics being translated into minute switches that could be used in billions of mobile phones around the world.

    4G mobile market

    Researchers at Cambridge are often ahead of the curve, and Professor Charles Smith is one of them. He set up Cavendish Kinetics in 1994 and in 2013 the company launched its first chip.

    Based on a minute mechanical switch, the chip solves many problems now faced by 4G mobile phone manufacturers. Compared with the semiconductor switches currently used in phones, the mechanical switch allows faster data rates and uses less power. It’s cheaper too, because as well as inventing the chip, Cavendish Kinetics developed a process technology that means it can be made in a standard CMOS foundry or ‘fab’.

    The company employs staff in the UK, USA, the Netherlands and South Korea, holds many published patents and has raised considerable venture capital funding.

    Cavendish Kinetics now has chips designed in a number of different mobile phones, and the potential market is huge, with more than one billion 4G phones produced each year. The technology could also be used in tablet computers and laptops for Bluetooth and wireless applications.

    Finely tuned technology

    While offering consumers faster and more reliable mobile connectivity, 4G phones also pose a challenge to the industry.

    Today’s small, slim mobile phones have space for only one fixed antenna. Ideally, the antenna would only work with one frequency, but because the phone is sending and receiving large amounts of data, the antenna needs tuning to a range of different frequencies or bands. In addition, different countries use different bands, so a 4G phone must work across a wide range of frequencies.

    Currently, the switches used to switch capacitors on and off to tune the antenna to different frequencies are based on gallium arsenide (GaAs) chips, but although GaAs is faster than silicon, it is also much more expensive to manufacture.

    The Cavendish Kinetics chip overcomes these challenges. It is based on a different technology, a nano-scale mechanical switch, which significantly improves the performance of mobile phones by enabling both faster data transfer and longer battery life.

    And because the chip can tune the antenna to different frequencies, it overcomes the so called ‘head-hand’ problem, which describes the drop in performance that can occur when the user’s head changes the resonant frequency of the antenna.

    As well as developing the new chip, Cavendish Kinetics also invented a way of making them in a standard silicon foundry. This, coupled with the fact that one mechanical chip can do the job of several GaAs chips, means the Cavendish Kinetics solution is significantly cheaper.

    Appliance of nano-science

    The research behind the new chip began more than 20 years ago in Cambridge’s Cavendish Laboratory. Funded by an EPSRC fellowship and research grants, academic physicist Charles Smith was trying to make sub-micron, free- standing metal structures in order to study the quantisation of phonons.

    Phonons are lattice vibrations that carry heat through insulators, and Smith was studying whether thermal conductivity is quantised in very small mechanical structures in the same way electrical conductivity is quantised in very small electrical conductors.

    Wondering what would happen if this technology was shrunk to the nano-scale, he realised these academic questions could have real-world applications in the shape of tiny low voltage switches.

    Cavendish Kinetics was formed to develop these applications, initially as computer memory and then as digital variable capacitors or switches for the new generation of 4G mobile phones.

    Over several years, the team then developed a process enabling their chip to be made in a standard CMOS foundry, making them cheaper to manufacture. Finally, they developed a clever way of packaging the little switches so they are never in contact with the air. By making them in their own minute cavity, which is sealed at the same time, the chips need no special packaging.

    Bringing new products to market is the opposite of how academia works. Manufacturers want 99.9% of their products to work; academics find one or two that function and focus on that

    Professor Charles Smith, Cavendish Laboratory

    I’m a great believer in luck. Everyone thinks it’s just about making the right choices, but that’s not how it works. You have to be in the right place at the right time as well

    Professor Charles Smith, Cavendish Laboratory

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  • 06/28/16--03:43: Leading Lights
  • Since the 1980s, Cambridge researchers have pioneered the field of polymer semiconductors. Their discoveries have opened up a new scientific field and spun out into three new companies.

    Lighting the way

    Professor Sir Richard Friend began to work on organic semiconductors at Cambridge’s Cavendish Laboratory in the mid 1980s, curious about whether polymers made from conjugated molecules would behave as semiconductors in the same way as silicon.

    While studying these compounds in Friend’s laboratory, Dr Jeremy Burroughes noticed that when a voltage was applied, a green light was emitted from the electrode. Together with Professor Donal Bradley, they realised these polymer light-emitting diodes could have many applications. With colleagues in the Department of Chemistry, Professors Andrew Holmes and Paul Burn, they filed patents for the discovery in 1989 and 1990. Later that year they revealed their discovery in Nature, and development of this work was taken forward through the formation of Cambridge Display Technology.

    As the research progressed, Friend and his colleagues Professor Henning Sirringhaus and Professor Neil Greenham spun out other businesses, including Plastic Logic and Eight19, to exploit emerging applications of the technology. And, as a result of the group’s research, the University and TTP won a competition to set up an Advanced Photovoltaics Research Accelerator at Cambridge with £5m funding from the Carbon Trust.

    Cambridge Display Technologies

    As the originator of polymer organic light emitting diode (P-OLED) technology, Cambridge Display Technology (CDT) – set up in 1992 – has continued to lead the field in its development.

    After securing its first licenses in 1996 from Philips, in 1999 it received investment of $133m from private equity funds. CDT was floated on the NASDAQ in 2004, and in 2007 was acquired by Japanese chemical company Sumitomo Chemical Company for $284m. Sumitomo Chemical has invested in CDT, which has a world-class portfolio of intellectual property.

    At its state-of-the-art R&D centre near Cambridge, CDT – which employs 140 staff – is continuing research into display and lighting applications, as well as organic semiconductor and photovoltaic applications.

    Already found in digital cameras and smartphones, organic LEDs are now entering the large-screen TV market, with more mass market products expected in the next few years.

    P-OLEDs have great potential for creating large area, diffuse light sources. With the global market for OLED lighting set to take off, CDT and Sumitomo are developing materials and manufacturing capability for low cost, large area OLED lighting.

    Plastic Logic

    Plastic Logic was founded in 2000 by Friend and Sirringhaus. Since then, the company has gone on to become a leading developer in plastic electronics manufacturing. Its revolutionary plastic resistor technology enables electronics to be manufactured on flexible or plastic sheets.

    Plastic Logic developed the first industrial-scale process for printing electronic circuits on plastic substrates, a process capable of making incredibly thin, light and robust displays – from flexible e-readers to signage.

    In 2015, the technology arm of Plastic Logic was spun out to form a new company, FlexEnable and its manufacturing arm renamed Plastic Logic Germany.


    Named after the number of minutes and seconds it takes sunlight to reach the Earth, Eight19 was set up in 2010 by Friend, Greenham and Sirringhaus to develop and make solar cells based on printed plastic. Today, its state-of-the-art printing and testing facilities are based at Cambridge Science Park.

    Flexible, robust and lightweight, these solar modules can be manufactured more quickly and cheaply than conventional solar cells. And with a fraction of the embedded energy of conventional solar units, printed plastic solar modules are ideal for consumer and off-grid applications.

    As well as new solar technology, Eight19 pioneered Indigo, an innovative new payment model based on mobile phones. With millions of off-grid consumers in sub-Saharan Africa, tapping into the mobile phone network is helping bring solar power to the poorest communities in the remotest parts of the region.

    In 2012, Indigo was spun off into Azuri Technologies, which is giving rural homes and small businesses across Kenya, Malawi, Zambia, South Sudan, Uganda, Rwanda and South Africa a affordable access to electricity – thanks to the payment model developed in Cambridge.

    Low cost organic solar cells could help to revolutionise solar power production by opening up new markets

    Dr Robert Trezona, Carbon Trust

    Solar cells made with organic semiconductors work very differently to those made with silicon, and are closer in operating principle to photosynthesis in green plants

    Professor Sir Richard Friend, Cavendish Laboratory

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    Why we live in a universe made of matter, rather than a universe with no matter at all, is one of science’s biggest questions. The behaviour of antimatter, a rare oppositely charged counterpart to normal matter, is thought to be key to understanding why. However, the nature of antimatter is a mystery. Scientists use data from the LHCb and ALPHA experiments at CERN to study antiparticles and antiatoms in order to learn more about it. Some of these scientists, from the University of Cambridge and other UK institutions, will present their work at the Royal Society’s annual Summer Science Exhibition which opens to the public tomorrow (5 July 2016).

    At CERN’s Large Hadron Collider particle accelerator, matter and antimatter versions of fundamental particles are produced when the accelerator beams smash into each other. The LHCb experiment records the traces these particles leave behind as they fly outwards from the beam collisions with exquisite precision, enabling scientists to identify the particles and deduce whether they are matter or antimatter. At larger scales, antimatter is studied in CERN’s antiproton decelerator complex, when antiprotons are joined with antielectrons to form anti-hydrogen atoms. The ALPHA experiment holds these antiatoms in suspension so that their structure and behavior can be studied. Both experiments are currently recording data that will enable scientists to carefully build up an understanding of why antimatter appears to behave the way it does.

    The University of Cambridge is a founder institute of the LHCb experiment and plays a major part in the construction and operation of the detectors that determine the identity of particles. The detectors use the Ring-Imaging Cherenkov radiation technique via which particles emit radiation as they travel faster than the speed of light in the material of the detectors. The principles behind this technique and the data produced will be on view in the Royal Society Summer Science Exhibition for visitors to examine.

    Professor Val Gibson of the University of Cambridge and former UK Spokesperson for the experiment said: “Antimatter might sound like science fiction, but it is one of the biggest mysteries in science today. We’re going to show everyone just why it matters so much – from what it can tell us about the earliest universe, to how we study it at the frontiers of research, to how it has everyday uses in medical imaging.“

    Visitors to the Exhibition will also be able to see how fundamental particles and antiparticles are identified with the LHCb experiment, talk to researchers to discover what this science is like, try the experimental techniques used to hold and study anti-atoms with the ALPHA experiment, and move, image and locate antimatter within a PET scanner system.

    The Royal Society’s Summer Science Exhibition is weeklong festival of cutting edge science from across the UK, featuring 22 exhibits which give a glimpse into the future of science and tech. Visitors can meet the scientists who are on hand at their exhibits, take part in activities and live demonstrations and attend talks. Entrance is free.

    Scientists from the University of Cambridge are presenting their research into the nature of antimatter at this year’s Royal Society Summer Exhibition.

    Antimatter might sound like science fiction, but it is one of the biggest mysteries in science today.
    Val Gibson

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    Researchers have built a miniature electro-optical switch which can change the spin – or angular momentum – of a liquid form of light by applying electric fields to a semiconductor device a millionth of a metre in size. Their results, reported in the journal Nature Materials, demonstrate how to bridge the gap between light and electricity, which could enable the development of ever faster and smaller electronics.

    There is a fundamental disparity between the way in which information is processed and transmitted by current technologies. To process information, electrical charges are moved around on semiconductor chips; and to transmit it, light flashes are sent down optical fibres. Current methods of converting between electrical and optical signals are both inefficient and slow, and researchers have been searching for ways to incorporate the two.

    In order to make electronics faster and more powerful, more transistors need to be squeezed onto semiconductor chips. For the past 50 years, the number of transistors on a single chip has doubled every two years – this is known as Moore’s law. However, as chips keep getting smaller, scientists now have to deal with the quantum effects associated with individual atoms and electrons, and they are looking for alternatives to the electron as the primary carrier of information in order to keep up with Moore’s law and our thirst for faster, cheaper and more powerful electronics.

    The University of Cambridge researchers, led by Professor Jeremy Baumberg from the NanoPhotonics Centre, in collaboration with researchers from Mexico and Greece, have built a switch which utilises a new state of matter called a Polariton Bose-Einstein condensate in order to mix electric and optical signals, while using miniscule amounts of energy.

    Polariton Bose-Einstein condensates are generated by trapping light between mirrors spaced only a few millionths of a metre apart, and letting it interact with thin slabs of semiconductor material, creating a half-light, half-matter mixture known as a polariton.

    Putting lots of polaritons in the same space can induce condensation – similar to the condensation of water droplets at high humidity – and the formation of a light-matter fluid which spins clockwise (spin-up) or anticlockwise (spin-down). By applying an electric field to this system, the researchers were able to control the spin of the condensate and switch it between up and down states. The polariton fluid emits light with clockwise or anticlockwise spin, which can be sent through optical fibres for communication, converting electrical to optical signals.

    “The polariton switch unifies the best properties of electronics and optics into one tiny device that can deliver at very high speeds while using minimal amounts of power,” said the paper’s lead author Dr Alexander Dreismann from Cambridge’s Cavendish Laboratory.

    “We have made a field-effect light switch that can bridge the gap between optics and electronics,” said co-author Dr Hamid Ohadi, also from the Cavendish Laboratory. “We’re reaching the limits of how small we can make transistors, and electronics based on liquid light could be a way of increasing the power and efficiency of the electronics we rely on.”

    While the prototype device works at cryogenic temperatures, the researchers are developing other materials that can operate at room temperature, so that the device may be commercialised. The other key factor for the commercialisation of the device is mass production and scalability. “Since this prototype is based on well-established fabrication technology, it has the potential to be scaled up in the near future,” said study co-author Professor Pavlos Savvidis from the FORTH institute in Crete, Greece.

    The team is currently exploring options for commercialising the technology as well as integrating it with the existing technology base.

    The research is funded as part of a UK Engineering and Physical Sciences Research Council (EPSRC) investment in the Cambridge NanoPhotonics Centre, as well as the European Research Council (ERC) and the Leverhulme Trust.

    A. Dreismann et al. ‘A sub-femtojoule electrical spin-switch based on optically trapped polariton condensates.’ Nature Materials (2016). DOI: 10.1038/nmat4722

    Researchers have built a record energy-efficient switch, which uses the interplay of electricity and a liquid form of light, in semiconductor microchips. The device could form the foundation of future signal processing and information technologies, making electronics even more efficient.

    We’re reaching the limits of how small we can make transistors, and electronics based on liquid light could be a way of increasing the power and efficiency of the electronics we rely on.
    Hamid Ohadi
    Polariton fluid emits clockwise or anticlockwise spin light by applying electric fields to a semiconductor chip.

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