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News Article
Site: www.rdmag.com

Researchers from the Centre for Quantum Technologies (CQT) at the National Univ. of Singapore and the Univ. of Seville in Spain have reported the most extreme “entanglement” between pairs of photons ever seen in the lab. The result was published in Physical Review Letters. The achievement is evidence for the validity of quantum physics and will bolster confidence in schemes for quantum cryptography and quantum computing designed to exploit this phenomenon. "For some quantum technologies to work as we intend, we need to be confident that quantum physics is complete," says Poh Hou Shun, who carried out the experiment at CQT. "Our new result increases that confidence," he says. Local realism Entanglement says that two particles, such as photons, can be married into a joint state. Once in such a state, either particle observed on its own appears to behave randomly. But if you measure both particles at once, you notice they are perfectly synchronized. Albert Einstein was famously troubled by this prediction of quantum physics. He didn't like the randomness that came with just one particle. He said "God does not play dice". He didn't like the correlations that came with two particles, either. He referred to this as "spooky action at a distance". Experiments since the 1970s have been collecting evidence that quantum predictions are correct. Recently an experiment in the Netherlands became the first to do away with all assumptions in the data-gathering. Technically known as a “loophole-free Bell test,” the experiment leaves no wiggle room in meaning: entangled particles do behave randomly, and they synchronize without exchanging signals. Entangled to the max In the lab in Singapore, Poh and his colleagues also performed a Bell test. But instead of closing loopholes, their setup pushes the entanglement towards its theoretical maximum. They make entangled photons by shining a laser through a crystal. The photons interact with the crystal in such a way that occasionally, one splits into two and the pair emerges entangled. The team control the photons with an array of lenses, mirrors and other optical elements to optimize the effect. The researchers looked at 33.2 million optimized photon pairs. Each pair was split up and the photons measured separately, then the correlation between the results quantified. In such a Bell test, the strength of the correlation says whether or not the photons were entangled. The measures involved are complex, but can be reduced to a simple number. Any value bigger than two is evidence for quantum effects at work. But there is also an upper limit. Quantum physics predicts the correlation measure cannot get any bigger than 2sqrt(2) ~2.82843. In the experiment at CQT, they measure 2.82759 ± 0.00051 - within 0.03% of the limit. If the peak value were the top of Everest, this would be only 2.6 meters below the summit. No extensions The record result also rules out a proposed extension to quantum theory. Earlier this year, Alexei Grinbaum with CEA in France put forward a model in which quantum physics is just an effective description of a more fundamental theory. He calculated a new limit on the correlation measure using tools from information theory. The calculations considered how much information an observer can hold about a two-particle system, and gave a limit on the correlation measure sitting just 0.1% under the quantum limit. "You need a very precise measurement to be able to distinguish the quantum limit, and that was our achievement," says Christian Kurtsiefer, a Principal Investigator at CQT and co-author on the paper. The team's result exceeds the Grinbaum limit by enough to rule out the model behind it. Entanglement doesn't allow faster-than-light communication, but it can be used for secret messaging and to speed up some calculations. Checking that it's possible to reach the quantum limit for correlations is valuable for these applications: their security and reliability depends on this limit being fundamental. The highly-anticipated educational tracks for the 2015 R&D 100 Awards & Technology Conference feature 28 sessions, plus keynote speakers Dean Kamen and Oak Ridge National Laboratory Director Thom Mason.  Learn more.


Abstract: The EU funded EUPHONON coordination action has published a report which includes Position Paper, Road Map and Strategic Research Agenda on Nanophononics in the context of ICT. This document aims at presenting Nanophononics to attract all the relevant stakeholders and help them to synergize into a vast but sound and well defined field. This call is made in direction of academic members, industries, SMEs and governmental organizations to join the nanophononics community (www.euphonon.eu). Nanophononics gathers the research fields targeting investigation, control and application of vibrations in solids or liquids that manifest themselves as sound or heat. This document aims at defining Nanophononics, bringing forth the urgent need to aggregate a Nanophononics community in Europe and boost its consolidation. This report seeks to demonstrate that phonons are at the conceptual heart of several scientific communities such as TeraHertz Phonons, Phononic Crystals, Micro-Nanoscale Heat Transfer, NanoMechanics and Optomechanics, Thermodynamics and Statistical Physics. The impact of building the Nanophononics community is reaching beyond the core phononics communities since the EU’s pivotal fields like Nanoelectronics, Quantum Technologies and Neuroinformatics are strongly dependent on knowledge in phononics. The position paper aims to introduce Nanophononics, place it in context and exemplify its impact on ICT illustrated with representative applications. The objective of the Road Map is to summarise the main research challenges and scientific questions in nanophononics, check the state of the art, identify the scientific and technological challenges to be addressed, estimate both the degree of complexity and the time scale to address them. The main objective of the Nanophononics Strategic Research Agenda is to define the role and impact of nanophononics in today’s society and in the industry, and give insight to the potential of the field to improve the properties of current information technology devices, enhance energy efficiency and advance the health and well-being and safety. The major impact at the moment can be seen to be in the thermal management, handling of heat and also in energy harvesting, including photovoltaics and thermoelectrics. More info: EUPHONON - Building a European NanoPhononics Community - www.euphonon.eu Nanophononics report (online version): www.euphonon.eu/EPH/reports.php Contract number: FP7-ICT-612086 About Phantoms Foundation The Phantoms Foundation was established in 2002 (Madrid, Spain) in order to provide high level Management profile to scientific projects. The Phantoms Foundation focuses its activities on NanoScience & Nanotechnology (N&N) and is a key actor in structuring and fostering European Excellence and enhancing collaborations in this field. For more information, please click Contacts: Questions regarding the report please contact: Sebastian Voltz, CNRS (France) (Project Coordinator): volz(at)em2c.ecp.fr Questions regarding the EUPHONON dissemination please contact: Dr. Antonio Correia: antonio(at)phantomsnet.net If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.


News Article
Site: www.rdmag.com

Why send a message back in time, but lock it so that no one can ever read the contents? Because it may be the key to solving currently intractable problems. That's the claim of an international collaboration who have just published a paper in npj Quantum Information. It turns out that an unopened message can be exceedingly useful. This is true if the experimenter entangles the message with some other system in the laboratory before sending it. Entanglement, a strange effect only possible in the realm of quantum physics, creates correlations between the time-travelling message and the laboratory system. These correlations can fuel a quantum computation. Around ten years ago researcher Dave Bacon, now at Google, showed that a time-travelling quantum computer could quickly solve a group of problems, known as NP-complete, which mathematicians have lumped together as being hard. The problem was, Bacon's quantum computer was travelling around 'closed timelike curves'. These are paths through the fabric of spacetime that loop back on themselves. General relativity allows such paths to exist through contortions in spacetime known as wormholes. Physicists argue something must stop such opportunities arising because it would threaten 'causality' -- in the classic example, someone could travel back in time and kill their grandfather, negating their own existence. And it's not only family ties that are threatened. Breaking the causal flow of time has consequences for quantum physics too. Over the past two decades, researchers have shown that foundational principles of quantum physics break in the presence of closed timelike curves: you can beat the uncertainty principle, an inherent fuzziness of quantum properties, and the no-cloning theorem, which says quantum states can't be copied. However, the new work shows that a quantum computer can solve insoluble problems even if it is travelling along 'open timelike curves', which don't create causality problems. That's because they don't allow direct interaction with anything in the object's own past: the time travelling particles (or data they contain) never interact with themselves. Nevertheless, the strange quantum properties that permit 'impossible' computations are left intact. "We avoid 'classical' paradoxes, like the grandfathers paradox, but you still get all these weird results," says Mile Gu, who led the work. Gu is at the Centre for Quantum Technologies (CQT) at the National University of Singapore and Tsinghua Univ. in Beijing. His eight other coauthors come from these institutions, the Univ. of Oxford, UK, Australian National Univ. in Canberra, the Univ. of Queensland in St Lucia, Australia, and QKD Corp in Toronto, Canada. "Whenever we present the idea, people say no way can this have an effect" says Jayne Thompson, a co-author at CQT. But it does: quantum particles sent on a timeloop could gain super computational power, even though the particles never interact with anything in the past. "The reason there is an effect is because some information is stored in the entangling correlations: this is what we're harnessing," Thompson says. There is a caveat -- not all physicists think that these open timeline curves are any more likely to be realisable in the physical universe than the closed ones. One argument against closed timelike curves is that no-one from the future has ever visited us. That argument, at least, doesn't apply to the open kind, because any messages from the future would be locked. Source: Centre for Quantum Technologies at the National Univ. of Singapore


News Article
Site: www.scientificamerican.com

Scientific American partnered on a writing contest for science fiction short stories inspired by the realm of quantum physics Clara Moskowitz The bizarre quantum rules that govern the microscopic universe sometimes seem more like fiction than fact, even to physicists. To capitalize on the fantastic aspects of quantum mechanics, the 2015 Quantum Shorts competition solicited short stories inspired by quantum physics. Scientific American partnered with the Center for Quantum Technologies at the National University of Singapore, which sponsored the competition, and we’re proud to announce the 2015 winners. First prize in the Open Category goes to Ana by Liam Hogan. It is the story of a young girl who suspects that looking under her bed for monsters has deadly consequences for another version of her in a parallel universe. This tale was the favorite of an international panel of judges, and you can read it below in full. The runner-up in the category, Don’t Die before You’re Dead, Sally Wu by Andrew Neil Gray, imagines an e-mail list of people communicating with their other selves in the multiverse. The People’s Choice winner, decided by popular vote online, is The Qubits of College Acceptance by Lily Turaski, which equates an unopened envelope of letters from colleges to the box containing Schrödinger's cat. And in the Youth Category, for which I was a judge, the winning story is Unrequited Signals by Tara Abrishami, about unrequited love between a pair of scientists trying to make contact with an alternate universe. We’re thrilled to share these creative and scientifically stimulating stories with you. To read all the entries, visit Quantum Shorts 2015. It’s weird, the things that can mess up a kid’s head. Take Ana, for example. She was convinced that every time she looked under her bed, the Universe split in two. In a parallel world in which a mirror Ana also looked under her bed before going to sleep and after saying her prayers and where, up until then, she’d never found anything bad, this time there would be a ghastly demon with wicked teeth and blood-stained claws, whose only desire was to catch and tear apart Ana, aged six and three quarter years. Little wonder she said her prayers before she looked. Little wonder she had nightmares. I told her that wasn’t the way the multiverse theory worked. That for every Ana that found a slavering beast, there was one that found a toy she’d lost, or one that forgot to look under the bed. She skewered me with her most outraged look. This Ana never forgot. But it’s hard arguing theoretical physics with a child yet to turn seven and, as I wasn’t prepared to deny the theory outright, it was clear this notion was not going to be an easy one to shift. It wasn’t simply that she had a binary, yes versus no, either-or view of the coin toss that happened in her imagination every time she lifted the skirt that kept under-the-bed out-of-sight. It was because what terrified her, wasn’t the finding a monster under her bed, it was the not finding a monster under her bed. In her head, every time she survived, she doomed the parallel Universe Ana to a grisly death. It was the guilt that was crushing her. “I have to,” she replied with an air of ancient sorrow. “There might be a monster under the bed. I have to check. And even if I don’t, the other Ana will.” This had me scratching my head, figuratively speaking. I’m a psychologist by trade, not a physicist. Wouldn’t that require the Universe to have already split? And, once the other Ana looked, it would be her Universe that split again, not this Ana’s. Maybe this was something I could use. I thought of her parents. Reading between the lines, not a tricky task with those two, they wanted me to crush Ana’s creativity. To make her as easy to handle as she had been twelve months earlier. To make her ‘normal’. But normal wasn’t an option; it was clear this precocious child had the potential to far exceed the pretensions of her middle class parents. “Ana,” I said, “Who looks first? You, or the other Ana?” She suspected a trick and trod carefully. “We both...” then she corrected herself. “There is no other Ana, not until I look. Or there is, but it’s me and we haven’t split yet.” “If she is you, will she react to finding the monster the same way you would?” She sucked air through the gap in her front teeth. “I guess.” “And how would you react, if, when you looked under the bed, you found a monster there? What would you do?” I waited. The silence stretched between us. This was somewhere she hadn’t been before. “I don’t know,” she said quietly. “But you’d do something? You wouldn’t just sit there?” “I’m sure you would. And what would your parents do, if they heard you scream?” “They’d come running,” she said, and they would. Any parent would. I let her think about this for a moment. “Ana, you’re intelligent, resourceful, and brave. And the other Ana, she is exactly the same. She is, after all, you. She - you - would not take it lying down. You’d fight, you’d run. Your parents would help. The one thing you would never be, is a victim. Don’t think I haven’t noticed the hobby horse propped up against the toy chest, ready for action.” “And the roller skates on the landing,” she said. I wasn’t sure how the roller skates would help. Perhaps she hoped the monster would trip on them. She’d be upset if I told her that her mother wordlessly tidied them up each night. “And the skates,” I diplomatically agreed. “It’s not much, perhaps, but you’re doing the best you can. And so would the other Ana. No monster is going to get a free lunch in this house.” She laughed, a lovely little laugh, made all the more charming by its rarity of use. I pushed on. “So it’s not a foregone conclusion that the monster always wins. And if it does not-” “-Then there are two Anas!” she interrupted. This wasn’t quite where I’d been going. I wanted her to acknowledge that she wasn’t responsible for what happened in the other Universes. How could she be? But sometimes, usually in fact, you had to let your patient find their own path. “And then four, and then eight, and then...” she babbled on. A small chime rang out on my wristwatch. “Okay Ana. I think we’ve made good progress. We’ll leave it there for today.” A muffled voice came through the door. “Ana? Honey? Who are you talking to in there?” Which was an illuminating denial. I jotted it down for future discussion, curious to see if Ana’s mother would come into the bedroom. “Okay sweetie,” she caved in, as I suspected she would. “But go to sleep now, you hear?” Ana waited until the footsteps faded away down the hall. “Goodnight, Doctor.” And then I slid myself back under her bed, listening to her breathing softly slow and waiting for tomorrow night, when she would once again lift the covers, and - all being well - discover me lying there, ready for our next session. Liam Hogan is a London-based writer and host of the award-winning monthly literary event, Liars' League. He was a finalist in Sci-Fest LA's Roswell Award 2015 and has had work published in Leap Books' Beware the Little White Rabbit, #Alice150 anthology and in Sci Phi Journal.


News Article
Site: phys.org

It turns out that an unopened message can be exceedingly useful. This is true if the experimenter entangles the message with some other system in the laboratory before sending it. Entanglement, a strange effect only possible in the realm of quantum physics, creates correlations between the time-travelling message and the laboratory system. These correlations can fuel a quantum computation. Around ten years ago researcher Dave Bacon, now at Google, showed that a time-travelling quantum computer could quickly solve a group of problems, known as NP-complete, which mathematicians have lumped together as being hard. The problem was, Bacon's quantum computer was travelling around 'closed timelike curves'. These are paths through the fabric of spacetime that loop back on themselves. General relativity allows such paths to exist through contortions in spacetime known as wormholes. Physicists argue something must stop such opportunities arising because it would threaten 'causality' - in the classic example, someone could travel back in time and kill their grandfather, negating their own existence. And it's not only family ties that are threatened. Breaking the causal flow of time has consequences for quantum physics too. Over the past two decades, researchers have shown that foundational principles of quantum physics break in the presence of closed timelike curves: you can beat the uncertainty principle, an inherent fuzziness of quantum properties, and the no-cloning theorem, which says quantum states can't be copied. However, the new work shows that a quantum computer can solve insoluble problems even if it is travelling along "open timelike curves", which don't create causality problems. That's because they don't allow direct interaction with anything in the object's own past: the time travelling particles (or data they contain) never interact with themselves. Nevertheless, the strange quantum properties that permit "impossible" computations are left intact. "We avoid 'classical' paradoxes, like the grandfathers paradox, but you still get all these weird results," says Mile Gu, who led the work. Gu is at the Centre for Quantum Technologies (CQT) at the National University of Singapore and Tsinghua University in Beijing. His eight other coauthors come from these institutions, the University of Oxford, UK, Australian National University in Canberra, the University of Queensland in St Lucia, Australia, and QKD Corp in Toronto, Canada. "Whenever we present the idea, people say no way can this have an effect" says Jayne Thompson, a co-author at CQT. But it does: quantum particles sent on a timeloop could gain super computational power, even though the particles never interact with anything in the past. "The reason there is an effect is because some information is stored in the entangling correlations: this is what we're harnessing," Thompson says. There is a caveat - not all physicists think that these open timeline curves are any more likely to be realisable in the physical universe than the closed ones. One argument against closed timelike curves is that no-one from the future has ever visited us. That argument, at least, doesn't apply to the open kind, because any messages from the future would be locked. More information: Xiao Yuan et al. Replicating the benefits of Deutschian closed timelike curves without breaking causality, npj Quantum Information (2015). DOI: 10.1038/npjqi.2015.7

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