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  • richardmitnick 12:24 pm on January 27, 2019 Permalink | Reply
    Tags: Anything that happens to one photon in an entangled pair will be transferred to the other one as well, , , Entangled photons, Fourth Industrial Revolution, Inquire-Quantum Information Research and Engineering instrument, Quantum communication is a secure method of sending and receiving data that's designed to preclude eavesdropping, , Quantum Information and Materials Group, , , Ultrasensitive cameras see things at the single photon level   

    From University of Arizona: “Interdisciplinary UA Researchers Get Tangled Up in Quantum Computing” 

    U Arizona bloc

    From University of Arizona

    Jan. 25, 2019
    Emily Dieckman

    UA researchers are building a quantum hub known as Inquire, which will be the world’s first shared research and training instrument to help researchers in diverse fields benefit from quantum resources.

    1
    Conceptual artwork of a pair of entangled quantum particles interacting. (Photo: Mark Garlick/Science Photo Library)

    Good neighbors often share resources: a cup of sugar, extra lawn chairs, a set of jumper cables. Researchers across campus at the University of Arizona will soon be able to share a less common – and far more valuable – resource to help them further their research: entangled photons, or interlinked pairs of light particles.

    With approximately $1.4 million in funding – $999,999 from the National Science Foundation and about $400,000 from the UA – professor Zheshen Zhang is leading the construction of the Interdisciplinary Quantum Information Research and Engineering instrument, known as Inquire, at the UA. Inquire is the world’s first shared research and training instrument to help researchers in diverse fields – including those with no expertise in quantum information science – benefit from quantum resources.

    Zhang is an assistant professor of materials science and engineering and optical sciences, and the leader of the Quantum Information and Materials Group at the UA. The co-investigators of the Inquire project include Ivan Djordjevic, professor of electrical and computer engineering and optical sciences; Jennifer Barton, director of the BIO5 Institute and professor of biomedical engineering, biosystems engineering, electrical and computer engineering, and optical sciences; Nasser Peyghambarian, professor of optical sciences; and Marek Romanowski, associate professor of biomedical engineering, and materials science and engineering.

    A network of fiber-optic cables will connect an automated quantum information hub in the basement of the Electrical and Computer Engineering building to four other buildings on campus: Biosciences Research Labs, Mines and Metallurgy, Physics and Atmospheric Sciences, and Meinel Optical Sciences.

    “One of the joys of the UA is collaborating with top scholars working in cutting-edge fields,” Barton said. “It seems like science fiction, but Zheshen is building a facility that will create quantum-entangled photons, then deliver them via fiber optics halfway across campus, right into the Translational Bioimaging Resource in the Biosciences Research Labs building.”

    “This is an exciting project that perfectly represents some of the key themes underlying our strategic plan,” said UA President Robert C. Robbins. “To be a leader in the Fourth Industrial Revolution, we must leverage collaboration, stay ahead of the technology curve and provide a high-powered environment where researchers have the tools they need to solve the world’s grand challenges. I look forward to seeing the new opportunities this facility brings once it is completed.”

    Construction on the project already has begun. The expected completion date is September 2021.

    Seeing Individual Photons

    Much like an atom is the smallest unit of matter, a photon is the smallest unit of light. So, while we can see the light of tens of billions of photons in a room lit by a lamp or a courtyard lit by the sun, the human eye – and most microscopes – can’t see individual photons. But sometimes this too-small-to-see information can be important. For example, a biomedical engineering lab might be doing an imaging study on a protein or an organic molecule that’s emitting a signal too weak for traditional cameras to see.

    “You can send your photons to the core facility, which is equipped with an array of ultrasensitive cameras that can see things at the single photon level,” Zhang said.

    Traditionally, researchers used high-powered lasers to illuminate these biological samples, which were sometimes damaged in the process. Using entangled photons as an illumination source provides higher sensitivity, less illuminating power, and the same – or even higher – resolution.

    “Two entangled photons can be worth a million of their classical brethren, potentially allowing us to image deeper without harming tissue,” Barton said.

    High-Precision Probing

    These fiber-optic cables are a two-way street. Researchers can send their photons into the central hub to be imaged by the high-tech microscopes, but the center can also share entangled photons with labs across campus.

    Entangled photons are interlinked pairs. Even when they’re separated by large distances, anything that happens to one photon in an entangled pair will be transferred to the other one as well.

    This relationship has several uses. For example, researchers can use photons as probes to help determine the nature of unidentified materials. The changes a material introduces to a photon, such as a change in color, provide clues to the material’s identity. When one entangled photon in a pair is used as a probe, the material introduces changes to both photons in the entangled pair.

    “Now you can perform a measurement on both photons to learn about the sample being probed,” Zhang said. “You can have twice as much information about the way the material is affecting the photon.”

    Secure Communications

    Entangled photons can also be used in quantum communication, a secure method of sending and receiving data that’s designed to preclude eavesdropping. It works like this: Before Party A shares any sensitive information with Party B, Party A sends a “quantum key,” a series of entangled photons that serves as the code for decrypting future transmissions. Quantum keys are designed so that the very act of decrypting or reading their contents changes their contents.

    If the quantum key arrives with any parts decrypted, the communicating parties know not to use that part of the key to encrypt future transmissions, because it has been “read” by hackers. The communicating parties can simply cut out that part of the key and use a new, shorter quantum key they know is secure.

    Party A and Party B in the above example don’t need to be quantum information scientists. Researchers across all kinds of disciplines can benefit from the unique features of entangled photons, and Inquire’s aim is to allow for just that.

    “This is a key area that the National Science Foundation identifies as one of its 10 Big Ideas and really wants to push forward because it is so interdisciplinary,” Zhang said. “It involves researchers across the boundaries of science, engineering, computer science, physics, chemistry, math, optics – everywhere. The key question is ‘How can everybody speak the same language, and how can they benefit from the progress made in other areas?'”

    See the full article here .


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    U Arizona campus

    The University of Arizona (UA) is a place without limits-where teaching, research, service and innovation merge to improve lives in Arizona and beyond. We aren’t afraid to ask big questions, and find even better answers.

    In 1885, establishing Arizona’s first university in the middle of the Sonoran Desert was a bold move. But our founders were fearless, and we have never lost that spirit. To this day, we’re revolutionizing the fields of space sciences, optics, biosciences, medicine, arts and humanities, business, technology transfer and many others. Since it was founded, the UA has grown to cover more than 380 acres in central Tucson, a rich breeding ground for discovery.

    Where else in the world can you find an astronomical observatory mirror lab under a football stadium?

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    An entire ecosystem under a glass dome? Visit our campus, just once, and you’ll quickly understand why the UA is a university unlike any other.

     
  • richardmitnick 1:55 pm on February 5, 2017 Permalink | Reply
    Tags: “We outsource the choice to the Universe itself”, Cosmic test backs 'quantum spookiness', Entangled photons, Iconic experiment to confirm quantum theory, , , The Big Bell Test   

    From Nature: “Cosmic test backs ‘quantum spookiness'” 

    Nature Mag
    Nature

    02 February 2017
    Elizabeth Gibney

    1
    The light from distant stars is used to fix settings in a new version of the iconic Bell test. Dr Fred Espenak/Science Photo Library.

    A version of an iconic experiment to confirm quantum theory has for the first time used the light of distant stars to bolster the case for a phenomenon that Albert Einstein referred to as “spooky action at a distance”.

    Einstein disliked the notion that objects can share a mysterious connection across any distance of space, and scientists have spent the past 50 years trying to make sure that their results showing this quantum effect could not have been caused by more intuitive explanations.

    Quantum physics suggests that two so-called entangled particles can maintain a special connection — even at a large distance — such that if one is measured, that instantly tells an experimenter what measuring the other particle will show. This happens despite the fact neither particle has definite properties until it is measured. That unsettled some physicists, including Einstein, who favoured an alternative explanation: that quantum theory is incomplete, and that the outcomes instead depend on some predetermined, but hidden, variables.

    The latest effort to explore the phenomenon, to be published in Physical Review Letters on 7 February, uses light emitted by stars around 600 years ago to select which measurements to make in a quantum experiment known as a Bell test. In doing so, they narrow down the point in history when, if they exist, hidden variables could have influenced the experiment.

    “It’s a beautiful experiment,” says Krister Shalm, a quantum physicist at the US National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland. Although few expected it to disprove quantum mechanics, such experiments “keep pushing alternative theories to be more and more contrived and ridiculous”, he says. Similar techniques could, in the future, help to protect against hackers who try to crack quantum-cryptography systems, he adds.

    Closing loopholes

    Physicists at the University of Vienna, along with colleagues in China, Germany and the United States, developed a new version of the Bell test — a protocol devised by the physicist John Bell in the 1960s to distinguish between two possible explanations for the seemingly strange behaviour of the quantum world.

    The test involves performing independent measurements on separated pairs of entangled quantum particles. Bell showed that, statistically, correlations between the results, once above a certain threshold limit, could not be explained by particles having hidden properties. Instead the coordinated outcomes seem to be the result of measurements on one particle mysteriously fixing the properties of the other.

    Although Bell tests have supported quantum theory many times, they include assumptions that leave wiggle room for non-quantum explanations, and physicists have been trying to close these ‘loopholes’ ever since.

    In 2015, they sealed a major victory when three separate teams, including Shalm’s, succeeded in simultaneously closing two major possible loopholes, by showing that entanglement could not be an illusion created by any speed-of-light communication between particles, or an artefact of only detecting certain photons.

    See the following:
    http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.115.250402
    http://www.nature.com/nature/journal/v526/n7575/abs/nature15759.html
    http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.115.250401

    Freedom of choice

    But they left open another loophole — one that is more subtle, and impossible to fully close, says Andrew Friedman, an astronomer at the Massachusetts Institute of Technology in Cambridge, and a co-author on the latest paper. Bell tests also assume that experimenters have free choice over which measurements they perform on each of the pair of photons. But some unknown effect could be influencing both the particles and what tests are performed (either by affecting choice of measurement directly, or more plausibly, by restricting the options that are available), to produce correlations that give the illusion of entanglement.

    To narrow this freedom-of-choice loophole, researchers have previously put 144 kilometres between the source of entangled particles and the random-number generator that they use to pick experimental settings.

    See
    http://www.pnas.org/content/107/46/19708

    The distance between them means that if any unknown process influenced both set-ups, it would have to have done so at a point in time before the experiment. But this only rules out any influences in the microseconds before: the latest paper sought to push this time back dramatically, by using light from two distant stars to determine the experimental settings for each photon. “We outsource the choice to the Universe itself,” says Friedman.

    The team, led by physicist Anton Zeilinger at the University of Vienna, picked which properties of the entangled photons to observe depending on whether its two telescopes detected incoming light as blue or red. The colour is decided when the light is emitted, and does not change during travel. This means that if some unknown effect, rather than quantum entanglement, explains the correlation, it would have to have been set in motion at least around 600 years ago, because the closest star is 575 light-years (176 parsecs) away, says Friedman, who hopes to eventually push back this limit to billions of years ago by doing the experiment with light from more distant quasars. Their results found a level of correlation that supports ‘action at a distance’.

    Protection against hackers

    Technically, the experiment is impressive, say Ronald Hanson, a quantum physicist at the Delft University of Technology in the Netherlands. But, unlike the loopholes closed in 2015, this one can never be fully closed; confining it to further in the past is only possible by making new assumptions — in this case, for example, by assuming that no one messed with the photons immediately before they hit the telescopes, he says.

    Others argue that although, fundamentally, the loophole is never closable, such experiments are valuable because new theories necessarily become more improbable and contrived, or eventually, end up assuming that everything in the Universe was determined at the time of the Big Bang — a philosophical view that most physicists reject. Reworking experiments to reduce and make better assumptions is therefore worthwhile, says Shalm.

    Such experiments also have practical value, argues Friedman, because if quantum mechanics turns out to be explained by a different underlying theory, that discovery could impact the security of technologies that rely on quantum theory, such as quantum encryption. And trying to close such loopholes is useful because minimizing the assumptions in an experiment serves to also beef up protection against hackers who might otherwise exploit them, says Shalm, whose team at the NIST is exploring whether Bell tests could be used in quantum cryptography.

    Harnessing cosmic phenomena is not the only way physicists are ensuring the independence of their measurement settings. In November, teams from around the world took part in the Big Bell Test, which tapped 100,000 game-playing volunteers worldwide to create random sequences of 0s and 1s, which physicists used to fix their measurement settings.

    Preliminary analysis indicates that in this case, most — and possibly even all — of the experiments yet again supported quantum mechanics, says Morgan Mitchell at the Institute of Photonic Sciences (ICFO) in Barcelona, Spain, which coordinated the event. “Sorry, Einstein,” he says.

    See the full article here .

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    Nature is a weekly international journal publishing the finest peer-reviewed research in all fields of science and technology on the basis of its originality, importance, interdisciplinary interest, timeliness, accessibility, elegance and surprising conclusions. Nature also provides rapid, authoritative, insightful and arresting news and interpretation of topical and coming trends affecting science, scientists and the wider public.

     
  • richardmitnick 7:37 am on September 27, 2016 Permalink | Reply
    Tags: , , Entangled photons, Multi-pass microscopy, , Quantum microscopy,   

    From Stanford: “Stanford physicists develop a more sensitive microscope” 

    Stanford University Name
    Stanford University

    September 27, 2016
    Taylor Kubota

    Anyone who has taken a photo in a poorly lit restaurant or dim concert venue knows all too well the grainy, fuzzy outcomes of low-light imaging. Scientists trying to take images of biological specimens encounter the same issue because they tend to work in low light to avoid damaging delicate samples. The resulting grainy images can make it hard to distinguish the intricate proteins and internal structures they are trying to study.

    1
    Stanford graduate student Brannon Klopfer helped develop the multi-pass microscope described in the current edition of “Nature Communications.” (Image credit: Thomas Juffmann)

    The effect that causes grainy images of either your meal or a biological sample is called shot noise. Stanford researchers may have come up with an elegant solution to this problem, which they refer to as “multi-pass microscopy.” This technique, detailed in a Sept. 27 paper in Nature Communications, could make it possible to view proteins and living cells in greater clarity than ever before.

    “If you work at low-light intensities, shot noise limits the maximum amount of information you can get from your image,” said Thomas Juffmann, co-author of the research and a postdoctoral research fellow in Stanford Professor Mark Kasevich’s research group. “But there’s a way around that; the shot-noise limit is not fundamental.”

    Recycled photons

    In optical microscopy, individual units of light, called photons, strike a detector to make the image. The researchers have found they get better results if each photon interacts with the sample multiple times, even in low light. To implement this in a microscope, instead of sending light through a specimen and then directly capturing the resulting image, the Stanford team repeatedly reflects the image back onto the specimen.

    “In a sense, it’s like you’re taking a picture of multiple times your object,” said co-author Brannon Klopfer, a graduate student in the Kasevich group. “You first take an image of the specimen, you then illuminate it with an image of itself, and the image you get, you again send back to illuminate the sample. This leads to contrast enhancement.”

    Multi-pass microscopy is not the only approach to overcoming the shot-noise limit. Another method, called quantum microscopy, uses entangled photons to achieve the same result, but it is more challenging to carry out.

    Entangled photons are photons that show quantum correlations. This means that performing an action on one of two entangled photons can have an effect on the other one, even if they are far apart from each other. It is what Albert Einstein referred to as “spooky action at a distance.”

    The ability of entangled photons to give information about each other means that quantum microscopy can produce higher-quality images compared to standard microscopy. At present, multi-pass microscopy has the potential to create comparably enhanced results with the added benefit of requiring less arduous preparation than quantum microscopy.

    “The advantage you gain when entangling two photons is what we gain when we go through the sample twice,” Juffmann said. “Currently, it is technologically easier to make a photon pass through a sample 10 times than to create a state in which 10 photons are entangled with each other.”

    A general technique

    Multi-pass microscopy could boost more than just low-light imaging because it acts as a general signal-enhancing technique. The method can increase the sensitivity of various microscopy techniques, so long as a source of image noise doesn’t build up with the recycling of photons.

    “While multi-passing builds up the signal in your image, the noise is hardly affected,” Klopfer said.

    At present, multi-passing is restricted to optical microscopes.But the team at Stanford is also working on multi-pass electron microscopy, where damage prevents the atomic-scale imaging of single proteins or DNA. Recycling the electrons in electron microscopy would improve image quality just as the recycling of photons does in the optical microscopes.

    Additional authors on this study include Timmo Frankfort and Mark Kasevich of Stanford, and Philipp Haslinger from the University of California, Berkeley.

    This research was funded by the Gordon and Betty Moore Foundation and by work supported under the Stanford Graduate Fellowship.

    See the full article here .

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