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  • richardmitnick 12:13 pm on June 19, 2020 Permalink | Reply
    Tags: "Is teleportation possible? Yes in the quantum world", “Individual electrons are promising qubits because they interact very easily with each other and individual electron qubits in semiconductors are also scalable", Now according to new research from the University of Rochester and Purdue University teleportation may also be possible between electrons., Quantum entanglement, Quantum teleportation is an important step in improving quantum computing., Scientists have recently demonstrated quantum teleportation by using electromagnetic photons to create remotely entangled pairs of qubits., Teleportation is possible in the subatomic world of quantum mechanics.,   

    From University of Rochester: “Is teleportation possible? Yes, in the quantum world” 

    From University of Rochester

    June 19, 2020
    Lindsey Valich

    A quantum processor semiconductor chip is connected to a circuit board in the lab of John Nichol, an assistant professor of physics at the University of Rochester. Nichol and Andrew Jordan, a professor of physics, are exploring new ways of creating quantum-mechanical interactions between distant electrons, promising major advances in quantum computing. (University of Rochester photo / J. Adam Fenster)

    Quantum teleportation is an important step in improving quantum computing.

    “Beam me up” is one of the most famous catchphrases from the Star Trek series. It is the command issued when a character wishes to teleport from a remote location back to the Starship Enterprise.

    While human teleportation exists only in science fiction, teleportation is possible in the subatomic world of quantum mechanics—albeit not in the way typically depicted on TV. In the quantum world, teleportation involves the transportation of information, rather than the transportation of matter.

    Last year scientists confirmed that information could be passed between photons on computer chips even when the photons were not physically linked.

    Now, according to new research from the University of Rochester and Purdue University, teleportation may also be possible between electrons.

    In a paper published in Nature Communications and one to appear in Physical Review X, the researchers, including John Nichol, an assistant professor of physics at Rochester, and Andrew Jordan, a professor of physics at Rochester, explore new ways of creating quantum-mechanical interactions between distant electrons. The research is an important step in improving quantum computing, which, in turn, has the potential to revolutionize technology, medicine, and science by providing faster and more efficient processors and sensors.

    ‘Spooky action at a distance’

    Quantum teleportation is a demonstration of what Albert Einstein famously called “spooky action at a distance”—also known as quantum entanglement. In entanglement—one of the basic of concepts of quantum physics—the properties of one particle affect the properties of another, even when the particles are separated by a large distance. Quantum teleportation involves two distant, entangled particles in which the state of a third particle instantly “teleports” its state to the two entangled particles.

    Quantum teleportation is an important means for transmitting information in quantum computing. While a typical computer consists of billions of transistors, called bits, quantum computers encode information in quantum bits, or qubits. A bit has a single binary value, which can be either “0” or “1,” but qubits can be both “0” and “1” at the same time. The ability for individual qubits to simultaneously occupy multiple states underlies the great potential power of quantum computers.

    Scientists have recently demonstrated quantum teleportation by using electromagnetic photons to create remotely entangled pairs of qubits.

    Qubits made from individual electrons, however, are also promising for transmitting information in semiconductors.

    “Individual electrons are promising qubits because they interact very easily with each other, and individual electron qubits in semiconductors are also scalable,” Nichol says. “Reliably creating long-distance interactions between electrons is essential for quantum computing.”

    Creating entangled pairs of electron qubits that span long distances, which is required for teleportation, has proved challenging, though: while photons naturally propagate over long distances, electrons usually are confined to one place.

    Entangled pairs of electrons

    In order to demonstrate quantum teleportation using electrons, the researchers harnessed a recently developed technique based on the principles of Heisenberg exchange coupling. An individual electron is like a bar magnet with a north pole and a south pole that can point either up or down. The direction of the pole—whether the north pole is pointing up or down, for instance—is known as the electron’s magnetic moment or quantum spin state. If certain kinds of particles have the same magnetic moment, they cannot be in the same place at the same time. That is, two electrons in the same quantum state cannot sit on top of each other. If they did, their states would swap back and forth in time.

    The researchers used the technique to distribute entangled pairs of electrons and teleport their spin states.

    “We provide evidence for ‘entanglement swapping,’ in which we create entanglement between two electrons even though the particles never interact, and ‘quantum gate teleportation,’ a potentially useful technique for quantum computing using teleportation,” Nichol says. “Our work shows that this can be done even without photons.”

    The results pave the way for future research on quantum teleportation involving spin states of all matter, not just photons, and provide more evidence for the surprisingly useful capabilities of individual electrons in qubit semiconductors.

    See the full article here .


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    U Rochester

    The University of Rochester is one of the country’s top-tier research universities. Our 158 buildings house more than 200 academic majors, more than 2,000 faculty and instructional staff, and some 10,500 students—approximately half of whom are women.

    Learning at the University of Rochester is also on a very personal scale. Rochester remains one of the smallest and most collegiate among top research universities, with smaller classes, a low 10:1 student to teacher ratio, and increased interactions with faculty.

  • richardmitnick 10:41 am on May 23, 2020 Permalink | Reply
    Tags: "Physicists Create a Group of 15 Trillion Entangled Atoms Setting a Major New Record", , , Quantum entanglement,   

    From Science Alert: “Physicists Create a Group of 15 Trillion Entangled Atoms, Setting a Major New Record” 


    From Science Alert

    23 MAY 2020

    The glass cell used for the experiment. (ICFO)

    Quantum physicists have set a new record for collecting a persistent group of entangled atoms together, getting 15 trillion atoms to co-exist in a “hot and messy” cloud of gas.

    Quantum entanglement is the phenomenon at the heart of quantum physics, where two particles can mysteriously influence each other, no matter what the distance is between them – so measuring one of them instantly gives us the measurement of the other.

    While scientists don’t yet fully understand why this occurs, it does indeed happen; but demonstrating quantum entanglement remains a delicate and challenging process.

    Entangled states need some very specific conditions to exist and survive, with most experiments in this area of research being conducted at temperatures approaching absolute zero.

    Artistic illustration of the atom cloud. (ICFO)

    That’s why this new study is such an achievement. The scientists were able to create a hot, chaotic gas of atoms heated to about 450 Kelvin (177° C or 350° F), packed full with around 15 trillion entangled atoms – around 100 times more than have ever been observed together before.

    These atoms weren’t isolated either: measurements taken by lasers showed them colliding into each other, and there were sometimes thousands of other atoms between entangled pairs. The experiment also showed the state of entanglement may be stronger than previously realised.

    “If we stop the measurement, the entanglement remains for about 1 millisecond, which means that 1,000 times per second a new batch of 15 trillion atoms is being entangled,” says quantum physicist Jia Kong from the Institute of Photonic Sciences in Spain (ICFO).

    “You must think that 1 ms is a very long time for the atoms, long enough for about 50 random collisions to occur. This clearly shows that the entanglement is not destroyed by these random events. This is maybe the most surprising result of the work.”

    Whereas most quantum entanglement experiments use ultra-low temperatures, to keep interference like these collisions down to a minimum, this study – using rubidium metal and nitrogen gas – shows that entanglement can survive much hotter temperatures.

    If we’re going to be able to use this phenomenon in next-generation communication systems and quantum computers, we need to get it working in warmer, noisier environments, and that’s something this new research points the way to.

    One of the ways these findings could be useful in the future is in magnetoencephalography or magnetic brain imaging, a process that uses similar hot, high-density atomic gases to detect magnetic fields created by brain activity. Entanglement could potentially make the technique more sensitive.

    For now, though, scientists have learned more about the rules of quantum entanglement, and just what it can and can’t withstand.

    “This result is surprising, a real departure from what everyone expects of entanglement,” says ICFO quantum physicist Morgan Mitchell.

    “We hope that this kind of giant entangled state will lead to better sensor performance in applications ranging from brain imaging, to self-driving cars, to searches for dark matter.”

    The research has been published in Nature Communications.

    See the full article here .


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  • richardmitnick 10:38 am on May 17, 2020 Permalink | Reply
    Tags: "IST Austria scientists demonstrate quantum radar prototype", ‘Microwave quantum illumination’, , Quantum entanglement   

    From IST Austria: “IST Austria scientists demonstrate quantum radar prototype” 

    From IST Austria

    New detection technique based on quantum technology developed at IST Austria – Study published in Science Advances.

    Illustration of a quantum radar prototype. © IST Austria/Philip Krantz

    Physicists at the Institute of Science and Technology Austria (IST Austria) have invented a new radar prototype that utilizes quantum entanglement as a method of object detection. This successful integration of quantum mechanics into our everyday devices could significantly impact the biomedical and security industries. The research is published in the journal Science Advances.

    Quantum entanglement is a physical phenomenon where two particles remain inter-connected, sharing physical traits regardless of how far apart they are from one another. Now, scientists from the research group of Professor Johannes Fink at the Institute of Science and Technology Austria (IST Austria) along with collaborators Stefano Pirandola from the Massachusetts Institute of Technology (MIT) and the University of York, UK, and David Vitali from the University of Camerino, Italy — have demonstrated a new type of detection technology called ‘microwave quantum illumination’ that utilizes entangled microwave photons as a method of detection. The prototype, which is also known as a ‘quantum radar’, is able to detect objects in noisy thermal environments where classical radar systems often fail. The technology has potential applications for ultra-low power biomedical imaging and security scanners.

    Using quantum entanglement as a new form of detection

    The working principles behind the device are simple: Instead of using conventional microwaves, the researchers entangle two groups of photons, which are called the ‘signal’ and ‘idler’ photons. The ‘signal’ photons are sent out towards the object of interest, whilst the ‘idler’ photons are measured in relative isolation, free from interference and noise. When the signal photons are reflected back, true entanglement between the signal and idler photons is lost, but a small amount of correlation survives, creating a signature or pattern that describes the existence or the absence of the target object—irrespective of the noise within the environment.

    “What we have demonstrated is a proof of concept for Microwave Quantum Radar,” says lead author and at the time of the research project postdoc in the Fink group Shabir Barzanjeh, whose previous research helped advance the theoretical notion behind quantum enhanced radar technology. “Using entanglement generated at a few thousandths of a degree above absolute zero (-273.14 °C), we have been able to detect low reflectivity objects at room-temperature.

    Quantum technology can outperform classical low-power radar

    While quantum entanglement in itself is fragile in nature, the device has a few advantages over conventional classical radars. For instance, at low power levels, conventional radar systems typically suffer from poor sensitivity as they have trouble distinguishing the radiation reflected by the object from naturally occurring background radiation noise. Quantum illumination offers a solution to this problem as the similarities between the ‘signal’ and ‘idler’ photons — generated by quantum entanglement — makes it more effective to distinguish the signal photons (received from the object of interest) from the noise generated within the environment. Barzanjeh who is now an Assistant Professor at the University of Calgary on the prototype’s performance: “The main message behind our research is that ‘quantum radar’ or ‘quantum microwave illumination’ is not only possible in theory but also in practice. When benchmarked against classical low-power detectors in the same conditions we already see, at very low-signal photon numbers, that quantum-enhanced detection can be superior.”

    Prominent milestone towards advancing 80 year-old radar technology

    Throughout history, basic science has been one of the key drivers of innovation, paradigm shift and technological breakthrough. Whilst still a proof of concept, the group’s research has effectively demonstrated a new method of detection that, in some cases, may already be superior to classical radar.

    “Throughout history, proof of concepts such as the one we have demonstrated here have often served as prominent milestones towards future technological advancements. It will be interesting to see the future implications of this research, particularly for short-range microwave sensors.” says Barzanjeh.

    Last author and group leader Professor Johannes Fink adds “This scientific result was only possible by bringing together theoretical and experimental physicists that are driven by the curiosity of how quantum mechanics can help to push the fundamental limits of sensing. But to show an advantage in practical situations we will also need the help of experienced electrical engineers and there still remains a lot of work to be done in order to make our result applicable to real-world detection tasks.”

    IST Austria Physicists – Shabir Barzanjeh (lead author) Johannes Fink (Group leader and co-author). © IST Austria/Anna Stöcher

    See the full article here.


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    is a young international institute dedicated to basic research and graduate education in the natural and mathematical sciences, located in Klosterneuburg on the outskirts of Vienna. Established jointly by the federal government of Austria and the provincial government of Lower Austria, the Institute was inaugurated in 2009 and will grow to about 90 research groups by 2026.

    The governance and management structures of IST Austria guarantee its independence and freedom from political and commercial influences. The Institute is headed by the President, who is appointed by the Board of Trustees and advised by the Scientific Board. The first President of IST Austria is Thomas A. Henzinger, a leading computer scientist and former professor of the University of California at Berkeley and the EPFL Lausanne in Switzerland.

  • richardmitnick 12:47 pm on May 11, 2020 Permalink | Reply
    Tags: "NIST Scientists Create New Recipe for Single-Atom Transistors", , , Quantum entanglement   

    From NIST: “NIST Scientists Create New Recipe for Single-Atom Transistors” 

    From NIST

    May 11, 2020

    Media Contact
    Ben P. Stein
    (301) 975-2763

    Technical Contact
    Richard M. Silver
    (301) 975-5609

    Credit: S. Kelley/NIST

    Once unimaginable, transistors consisting only of several-atom clusters or even single atoms promise to become the building blocks of a new generation of computers with unparalleled memory and processing power. But to realize the full potential of these tiny transistors — miniature electrical on-off switches — researchers must find a way to make many copies of these notoriously difficult-to-fabricate components.

    Now, researchers at the National Institute of Standards and Technology (NIST) and their colleagues at the University of Maryland have developed a step-by-step recipe to produce the atomic-scale devices. Using these instructions, the NIST-led team has become only the second in the world to construct a single-atom transistor and the first to fabricate a series of single electron transistors with atom-scale control over the devices’ geometry.

    The scientists demonstrated that they could precisely adjust the rate at which individual electrons flow through a physical gap or electrical barrier in their transistor — even though classical physics would forbid the electrons from doing so because they lack enough energy. That strictly quantum phenomenon, known as quantum tunneling, only becomes important when gaps are extremely tiny, such as in the miniature transistors. Precise control over quantum tunneling is key because it enables the transistors to become “entangled” or interlinked in a way only possible through quantum mechanics and opens new possibilities for creating quantum bits (qubits) that could be used in quantum computing.

    To fabricate single-atom and few-atom transistors, the team relied on a known technique in which a silicon chip is covered with a layer of hydrogen atoms, which readily bind to silicon. The fine tip of a scanning tunneling microscope then removed hydrogen atoms at selected sites. The remaining hydrogen acted as a barrier so that when the team directed phosphine gas (PH3) at the silicon surface, individual PH3 molecules attached only to the locations where the hydrogen had been removed (see animation). The researchers then heated the silicon surface. The heat ejected hydrogen atoms from the PH3 and caused the phosphorus atom that was left behind to embed itself in the surface. With additional processing, bound phosphorous atoms created the foundation of a series of highly stable single- or few-atom devices that have the potential to serve as qubits.

    Two of the steps in the method devised by the NIST teams — sealing the phosphorus atoms with protective layers of silicon and then making electrical contact with the embedded atoms — appear to have been essential to reliably fabricate many copies of atomically precise devices, NIST researcher Richard Silver said.

    In the past, researchers have typically applied heat as all the silicon layers are grown, in order to remove defects and ensure that the silicon has the pure crystalline structure required to integrate the single-atom devices with conventional silicon-chip electrical components. But the NIST scientists found that such heating could dislodge the bound phosphorus atoms and potentially disrupt the structure of the atomic-scale devices. Instead, the team deposited the first several silicon layers at room temperature, allowing the phosphorus atoms to stay put. Only when subsequent layers were deposited did the team apply heat.

    “We believe our method of applying the layers provides more stable and precise atomic-scale devices,“ said Silver. Having even a single atom out of place can alter the conductivity and other properties of electrical components that feature single or small clusters of atoms.

    The team also developed a novel technique for the crucial step of making electrical contact with the buried atoms so that they can operate as part of a circuit. The NIST scientists gently heated a layer of palladium metal applied to specific regions on the silicon surface that resided directly above selected components of the silicon-embedded device. The heated palladium reacted with the silicon to form an electrically conducting alloy called palladium silicide, which naturally penetrated through the silicon and made contact with the phosphorus atoms.

    In a recent edition of Advanced Functional Materials, Silver and his colleagues, who include Xiqiao Wang, Jonathan Wyrick, Michael Stewart Jr. and Curt Richter, emphasized that their contact method has a nearly 100% success rate. That’s a key achievement, noted Wyrick. “You can have the best single-atom-transistor device in the world, but if you can’t make contact with it, it’s useless,” he said.

    Fabricating single-atom transistors “is a difficult and complicated process that maybe everyone has to cut their teeth on, but we’ve laid out the steps so that other teams don’t have to proceed by trial and error,” said Richter.

    In related work published today in Communications Physics, Silver and his colleagues demonstrated that they could precisely control the rate at which individual electrons tunnel through atomically precise tunnel barriers in single-electron transistors. The NIST researchers and their colleagues fabricated a series of single-electron transistors identical in every way except for differences in the size of the tunneling gap. Measurements of current flow indicated that by increasing or decreasing the gap between transistor components by less than a nanometer (billionth of a meter), the team could precisely control the flow of a single electron through the transistor in a predictable manner.

    “Because quantum tunneling is so fundamental to any quantum device, including the construction of qubits, the ability to control the flow of one electron at a time is a significant achievement,” Wyrick said. In addition, as engineers pack more and more circuitry on a tiny computer chip and the gap between components continues to shrink, understanding and controlling the effects of quantum tunneling will become even more critical, Richter said.

    See the full article here.


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    NIST Campus, Gaitherberg, MD, USA

    NIST Mission, Vision, Core Competencies, and Core Values

    NIST’s mission

    To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.
    NIST’s vision

    NIST will be the world’s leader in creating critical measurement solutions and promoting equitable standards. Our efforts stimulate innovation, foster industrial competitiveness, and improve the quality of life.
    NIST’s core competencies

    Measurement science
    Rigorous traceability
    Development and use of standards

    NIST’s core values

    NIST is an organization with strong values, reflected both in our history and our current work. NIST leadership and staff will uphold these values to ensure a high performing environment that is safe and respectful of all.

    Perseverance: We take the long view, planning the future with scientific knowledge and imagination to ensure continued impact and relevance for our stakeholders.
    Integrity: We are ethical, honest, independent, and provide an objective perspective.
    Inclusivity: We work collaboratively to harness the diversity of people and ideas, both inside and outside of NIST, to attain the best solutions to multidisciplinary challenges.
    Excellence: We apply rigor and critical thinking to achieve world-class results and continuous improvement in everything we do.

  • richardmitnick 5:01 pm on February 27, 2020 Permalink | Reply
    Tags: "Quantum researchers able to split one photon into three", Quantum entanglement, Quantum optics,   

    From University of Waterloo: “Quantum researchers able to split one photon into three” 

    U Waterloo bloc

    From University of Waterloo

    February 27, 2020

    Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo report the first occurrence of directly splitting one photon into three.

    The occurrence, the first of its kind, used the spontaneous parametric down-conversion method (SPDC) in quantum optics and created what quantum optics researchers call a non-Gaussian state of light. A non-Gaussian state of light is considered a critical ingredient to gain a quantum advantage.

    “It was understood that there were limits to the type of entanglement generated with the two-photon version, but these results form the basis of an exciting new paradigm of three-photon quantum optics,” said Chris Wilson, a principal investigator at IQC faculty member and a professor of Electrical and Computer Engineering at Waterloo.

    “Given that this research brings us past the known ability to split one photon into two entangled daughter photons, we’re optimistic that we’ve opened up a new area of exploration.”

    Lab of Chris Wilson

    “The two-photon version has been a workhorse for quantum research for over 30 years,” said Wilson. “We think three photons will overcome the limits and will encourage further theoretical research and experimental applications and hopefully the development of optical quantum computing using superconducting units.”

    Wilson used microwave photons to stretch the known limits of SPDC. The experimental implementation used a superconducting parametric resonator. The result clearly showed the strong correlation among three photons generated at different frequencies. Ongoing work aims to show that the photons are entangled.

    “Non-Gaussian states and operations are a critical ingredient for obtaining the quantum advantage,” said Wilson. “They are very difficult to simulate and model classically, which has resulted in a dearth of theoretical work for this application.”

    Science paper:
    “Observation of Three-Photon Spontaneous Parametric Down-Conversion in a Superconducting Parametric Cavity”
    Physical Review X

    See the full article here .


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    U Waterloo campus

    In just half a century, the Waterloo, located at the heart of Canada’s technology hub, has become a leading comprehensive university with nearly 36,000 full- and part-time students in undergraduate and graduate programs.

    Consistently ranked Canada’s most innovative university, Waterloo is home to advanced research and teaching in science and engineering, mathematics and computer science, health, environment, arts and social sciences. From quantum computing and nanotechnology to clinical psychology and health sciences research, Waterloo brings ideas and brilliant minds together, inspiring innovations with real impact today and in the future.

    As home to the world’s largest post-secondary co-operative education program, Waterloo embraces its connections to the world and encourages enterprising partnerships in learning, research, and commercialization. With campuses and education centres on four continents, and academic partnerships spanning the globe, Waterloo is shaping the future of the planet.

  • richardmitnick 4:40 pm on February 18, 2020 Permalink | Reply
    Tags: , , , , MIP-multiprover interactive proof, , Quantum entanglement, ,   

    From Science News: “How a quantum technique highlights math’s mysterious link to physics” 

    From Science News

    February 17, 2020
    Tom Siegfried

    Verifying proofs to very hard math problems is possible with infinite quantum entanglement.

    A technique that relies on quantum entanglement (illustrated) expands the realm of mathematical problems for which the solution could (in theory) be verified. inkoly/iStock/Getty Images Plus.

    It has long been a mystery why pure math can reveal so much about the nature of the physical world.

    Antimatter was discovered in Paul Dirac’s equations before being detected in cosmic rays. Quarks appeared in symbols sketched out on a napkin by Murray Gell-Mann several years before they were confirmed experimentally. Einstein’s equations for gravity suggested the universe was expanding a decade before Edwin Hubble provided the proof. Einstein’s math also predicted gravitational waves a full century before behemoth apparatuses detected those waves (which were produced by collisions of black holes — also first inferred from Einstein’s math).

    Nobel laureate physicist Eugene Wigner alluded to math’s mysterious power as the “unreasonable effectiveness of mathematics in the natural sciences.” Somehow, Wigner said, math devised to explain known phenomena contains clues to phenomena not yet experienced — the math gives more out than was put in. “The enormous usefulness of mathematics in the natural sciences is something bordering on the mysterious and … there is no rational explanation for it,” Wigner wrote in 1960.

    But maybe there’s a new clue to what that explanation might be. Perhaps math’s peculiar power to describe the physical world has something to do with the fact that the physical world also has something to say about mathematics.

    At least that’s a conceivable implication of a new paper that has startled the interrelated worlds of math, computer science and quantum physics.

    In an enormously complicated 165-page paper, computer scientist Zhengfeng Ji and colleagues present a result that penetrates to the heart of deep questions about math, computing and their connection to reality. It’s about a procedure for verifying the solutions to very complex mathematical propositions, even some that are believed to be impossible to solve. In essence, the new finding boils down to demonstrating a vast gulf between infinite and almost infinite, with huge implications for certain high-profile math problems. Seeing into that gulf, it turns out, requires the mysterious power of quantum physics.

    Everybody involved has long known that some math problems are too hard to solve (at least without unlimited time), but a proposed solution could be rather easily verified. Suppose someone claims to have the answer to such a very hard problem. Their proof is much too long to check line by line. Can you verify the answer merely by asking that person (the “prover”) some questions? Sometimes, yes. But for very complicated proofs, probably not. If there are two provers, though, both in possession of the proof, asking each of them some questions might allow you to verify that the proof is correct (at least with very high probability). There’s a catch, though — the provers must be kept separate, so they can’t communicate and therefore collude on how to answer your questions. (This approach is called MIP, for multiprover interactive proof.)

    Verifying a proof without actually seeing it is not that strange a concept. Many examples exist for how a prover can convince you that they know the answer to a problem without actually telling you the answer. A standard method for coding secret messages, for example, relies on using a very large number (perhaps hundreds of digits long) to encode the message. It can be decoded only by someone who knows the prime factors that, when multiplied together, produce the very large number. It’s impossible to figure out those prime numbers (within the lifetime of the universe) even with an army of supercomputers. So if someone can decode your message, they’ve proved to you that they know the primes, without needing to tell you what they are.

    Someday, though, calculating those primes might be feasible, with a future-generation quantum computer. Today’s quantum computers are relatively rudimentary, but in principle, an advanced model could crack codes by calculating the prime factors for enormously big numbers.

    That power stems, at least in part, from the weird phenomenon known as quantum entanglement. And it turns out that, similarly, quantum entanglement boosts the power of MIP provers. By sharing an infinite amount of quantum entanglement, MIP provers can verify vastly more complicated proofs than nonquantum MIP provers.

    It is obligatory to say that entanglement is what Einstein called “spooky action at a distance.” But it’s not action at a distance, and it just seems spooky. Quantum particles (say photons, particles of light) from a common origin (say, both spit out by a single atom) share a quantum connection that links the results of certain measurements made on the particles even if they are far apart. It may be mysterious, but it’s not magic. It’s physics.

    Say two provers share a supply of entangled photon pairs. They can convince a verifier that they have a valid proof for some problems. But for a large category of extremely complicated problems, this method works only if the supply of such entangled particles is infinite. A large amount of entanglement is not enough. It has to be literally unlimited. A huge but finite amount of entanglement can’t even approximate the power of an infinite amount of entanglement.

    As Emily Conover explains in her report for Science News, this discovery proves false a couple of widely believed mathematical conjectures. One, known as Tsirelson’s problem, specifically suggested that a sufficient amount of entanglement could approximate what you could do with an infinite amount. Tsirelson’s problem was mathematically equivalent to another open problem, known as Connes’ embedding conjecture, which has to do with the algebra of operators, the kinds of mathematical expressions that are used in quantum mechanics to represent quantities that can be observed.

    Refuting the Connes conjecture, and showing that MIP plus entanglement could be used to verify immensely complicated proofs, stunned many in the mathematical community. (One expert, upon hearing the news, compared his feces to bricks.) But the new work isn’t likely to make any immediate impact in the everyday world. For one thing, all-knowing provers do not exist, and if they did they would probably have to be future super-AI quantum computers with unlimited computing capability (not to mention an unfathomable supply of energy). Nobody knows how to do that in even Star Trek’s century.

    Still, pursuit of this discovery quite possibly will turn up deeper implications for math, computer science and quantum physics.

    It probably won’t shed any light on controversies over the best way to interpret quantum mechanics, as computer science theorist Scott Aaronson notes in his blog about the new finding. But perhaps it could provide some sort of clues regarding the nature of infinity. That might be good for something, perhaps illuminating whether infinity plays a meaningful role in reality or is a mere mathematical idealization.

    On another level, the new work raises an interesting point about the relationship between math and the physical world. The existence of quantum entanglement, a (surprising) physical phenomenon, somehow allows mathematicians to solve problems that seem to be strictly mathematical. Wondering why physics helps out math might be just as entertaining as contemplating math’s unreasonable effectiveness in helping out physics. Maybe even one will someday explain the other.

    See the full article here .


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  • richardmitnick 8:18 am on January 22, 2020 Permalink | Reply
    Tags: "High-precision distributed sensing using an entangled quantum network", , , , Quantum entanglement, , Quantum-enhanced metrology, Squeezed light and homodyne detection, Technical University of Denmark, , Using an entangled quantum network to sense an averaged phase shift among multiple distributed nodes., We wanted to estimate the average of multiple optical phase shifts.   

    From Technical University of Denmark and University of Copenhagen via phys.org: “High-precision distributed sensing using an entangled quantum network” 


    From Technical University of Denmark


    From University of Copenhagen


    January 21, 2020
    Ingrid Fadelli

    The experimental setup used in the study. Credit: Jonas S. Neergaard-Nielsen.

    Quantum-enhanced metrology has been an active area of research for several years now due to its many possible applications, ranging from atomic clocks to biological imaging. Past physics research established that having a non-classical probe, such as squeezed light or an entangled spin state, can have significant benefits compared to classical probes. This idea was explored further in several recent works, some of which also considered the benefits of examining multiple distinct samples with non-classical probes.

    Inspired by these studies, researchers at the Technical University of Denmark and the University of Copenhagen have recently carried out an experiment investigating the advantages of using an entangled quantum network to sense an averaged phase shift among multiple distributed nodes. Their paper, published in Nature Physics,introduces a series of techniques that could help to collect more precise measurements in a variety of areas.

    “Recent studies showed that having non-classical correlations between probes addressing different samples could lead to a gain compared to having non-correlated probes,” Johannes Borregaard, the researcher who initiated the project, told Phys.org. “This inspired us to investigate whether such advantages could be demonstrated already using present technology.”

    In their study, Borregaard and his colleagues focused on squeezed light and homodyne detection, which are now established sensing techniques. The overall goal of the experiment was to measure a global property of multiple spatially separated objects and investigate whether probing these objects simultaneously with entangled light led to more precise results than probing them individually. The researchers found that the use of a quantum network to probe the objects simultaneously enabled phase sensing with far higher precision than that attainable when examining probes individually.

    Outline of the scheme for distributed phase sensing. Squeezed light (sqz) is distributed via beam-splitters to the phase samples under study. The phases imprinted on the squeezed probes are detected with homodyne detectors and these measurements are subsequently combined to form the average phase shift. Due to the quantum correlations between the probes, this average phase shift can be obtained with higher precision than if the samples were probed independently. Credit: Jonas S. Neergaard-Nielsen.

    “In this particular demonstration, we wanted to estimate the average of multiple optical phase shifts,” Xueshi Guo, lead author of the paper, told Phys.org. “We measured the phase shifts (which we set with wave plates to a known value) by sending a weak laser beam through and detecting the change in the light’s phase quadrature with homodyne detectors.”

    To generate entangled light and distribute it among different sites, the researchers used a fairly simple method. First, they created a phase-squeezed state of light, which is a standard non-classical quantum state. Then they divided it into multiple beams using beam splitters.

    This resulted in light probes with reduced noise in the phase quadrature, but only when all probes were measured simultaneously. This is precisely the property required to attain a better signal-to-noise ratio in the estimation of the average phase without increasing the energy (i.e., number of photons) in the probe states.

    “In the experiment we had four phase samples in total,” Guo explained. “The gain that can be achieved by using entanglement is then theoretically limited to a factor of 2. However, as the number of samples increases, so does the achievable gain.”

    Image showing the source of squeezed light in the experiment (i.e., an optical parametric oscillator). Credit: Jonas S. Neergaard-Nielsen.

    The researchers found that the advantage of using distributed quantum sensing truly becomes significant when a property of many objects connected in an optical network is to be measured. To successfully attain an increase in precision, however, the losses in the network and detectors need to be kept low, otherwise the quantum advantage vanishes.

    “The key achievement of our study is the experimental demonstration of the advantages associated with using multi-mode entanglement for distributed sensing,” Borregaard said. “Previous theoretical studies had predicted such advantages, but they often considered highly idealized scenarios and experimentally very challenging probe states or detection techniques. Our work cements that such advantages are accessible even with present noisy technology.”

    In the future, the techniques demonstrated by Borregaard, Guo and their colleagues could have important implications for a number of different areas of research and technology development. For instance, they could help to enhance the sensitivity of molecular tracking tools, atomic clocks, and optical magnetometry techniques.

    Although only further investigations will determine how much each of these applications can benefit from the methods introduced by the researchers, this recent study offers valuable insight into how quantum-enhanced metrology can be achieved using readily available technologies, such as squeezed light generation and homodyne detection. In their future work, the researchers plan to continue investigating the use of multi-mode squeezed light in other contexts, in particular for optical quantum computing applications.

    “In our experiment, we did not actually use the optimal probe states and measurement methods allowed by quantum theory, so it would be exciting to demonstrate the distributed sensing problem with those resources,” Jonas S. Neergaard-Nielsen, another researcher involved in the study, told Phys.org. “Furthermore, it could be interesting to distribute the entangled light to far-away locations in an installed fiber network to show the real-world applicability of the scheme.”

    See the full article here .


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  • richardmitnick 7:42 pm on January 16, 2020 Permalink | Reply
    Tags: "Study finds billions of quantum entangled electrons in ‘strange metal", , , , Quantum entanglement, Quantum entanglement is the basis for storage and processing of quantum information., , Terahertz spectroscopy, With strange metals there is an unusual connection between electrical resistance and temperature.   

    From Rice University: “Study finds billions of quantum entangled electrons in ‘strange metal” 

    Rice U bloc

    From Rice University

    January 16, 2020
    Jade Boyd

    Physicists provide direct evidence of entanglement’s role in quantum criticality.

    In a new study, U.S. and Austrian physicists have observed quantum entanglement among “billions of billions” of flowing electrons in a quantum critical material.

    Junichiro Kono (left) and Qimiao Si in Kono’s Rice University laboratory in December 2019. (Photo by Jeff Fitlow/Rice University)

    The research, which appears this week in Science, examined the electronic and magnetic behavior of a “strange metal” compound of ytterbium, rhodium and silicon as it both neared and passed through a critical transition at the boundary between two well-studied quantum phases.

    The study at Rice University and Vienna University of Technology (TU Wien) provides the strongest direct evidence to date of entanglement’s role in bringing about quantum criticality, said study co-author Qimiao Si of Rice.

    “When we think about quantum entanglement, we think about small things,” Si said. “We don’t associate it with macroscopic objects. But at a quantum critical point, things are so collective that we have this chance to see the effects of entanglement, even in a metallic film that contains billions of billions of quantum mechanical objects.”

    Si, a theoretical physicist and director of the Rice Center for Quantum Materials (RCQM), has spent more than two decades studying what happens when materials like strange metals and high-temperature superconductors change quantum phases. Better understanding such materials could open the door to new technologies in computing, communications and more.

    The international team overcame several challenges to get the result. TU Wien researchers developed a highly complex materials synthesis technique to produce ultrapure films containing one part ytterbium for every two parts rhodium and silicon (YbRh2Si2). At absolute zero temperature, the material undergoes a transition from one quantum phase that forms a magnetic order to another that does not.

    Physicist Silke Bühler-Paschen of the Vienna University of Technology (Photo by Luisa Puiu/TU Wien)

    At Rice, study co-lead author Xinwei Li, then a graduate student in the lab of co-author and RCQM member Junichiro Kono, performed terahertz spectroscopy experiments on the films at temperatures as low as 1.4 Kelvin. The terahertz measurements revealed the optical conductivity of the YbRh2Si2 films as they were cooled to a quantum critical point that marked the transition from one quantum phase to another.

    “With strange metals, there is an unusual connection between electrical resistance and temperature,” said corresponding author Silke Bühler-Paschen of TU Wien’s Institute for Solid State Physics. “In contrast to simple metals such as copper or gold, this does not seem to be due to the thermal movement of the atoms, but to quantum fluctuations at the absolute zero temperature.”

    To measure optical conductivity, Li shined coherent electromagnetic radiation in the terahertz frequency range on top of the films and analyzed the amount of terahertz rays that passed through as a function of frequency and temperature. The experiments revealed “frequency over temperature scaling,” a telltale sign of quantum criticality, the authors said.

    Kono, an engineer and physicist in Rice’s Brown School of Engineering, said the measurements were painstaking for Li, who’s now a postdoctoral researcher at the California Institute of Technology. For example, only a fraction of the terahertz radiation shined onto the sample passed through to the detector, and the important measurement was how much that fraction rose or fell at different temperatures.

    Former Rice University graduate student Xinwei Li in 2016 with the terahertz spectrometer he later used to measure entanglement in the conduction electrons flowing through a “strange metal” compound of ytterbium, rhodium and silicon. (Photo by Jeff Fitlow/Rice University)

    “Less than 0.1% of the total terahertz radiation was transmitted, and the signal, which was the variation of conductivity as a function of frequency, was a further few percent of that,” Kono said. “It took many hours to take reliable data at each temperature to average over many, many measurements, and it was necessary to take data at many, many temperatures to prove the existence of scaling.

    “Xinwei was very, very patient and persistent,” Kono said. “In addition, he carefully processed the huge amounts of data he collected to unfold the scaling law, which was really fascinating to me.”

    Making the films was even more challenging. To grow them thin enough to pass terahertz rays, the TU Wien team developed a unique molecular beam epitaxy system and an elaborate growth procedure. Ytterbium, rhodium and silicon were simultaneously evaporated from separate sources in the exact 1-2-2 ratio. Because of the high energy needed to evaporate rhodium and silicon, the system required a custom-made ultrahigh vacuum chamber with two electron-beam evaporators.

    “Our wild card was finding the perfect substrate: germanium,” said TU Wien graduate student Lukas Prochaska, a study co-lead author. The germanium was transparent to terahertz, and had “certain atomic distances (that were) practically identical to those between the ytterbium atoms in YbRh2Si2, which explains the excellent quality of the films,” he said.

    Si recalled discussing the experiment with Bühler-Paschen more than 15 years ago when they were exploring the means to test a new class of quantum critical point. The hallmark of the quantum critical point that they were advancing with co-workers is that the quantum entanglement between spins and charges is critical.

    Former Rice University graduate student Xinwei Li (left) and Professor Junichiro Kono in 2016 with the terahertz spectrometer Li used to measure quantum entanglement in YbRh2Si2. (Photo by Jeff Fitlow/Rice University)

    “At a magnetic quantum critical point, conventional wisdom dictates that only the spin sector will be critical,” he said. “But if the charge and spin sectors are quantum-entangled, the charge sector will end up being critical as well.”

    At the time, the technology was not available to test the hypothesis, but by 2016, the situation had changed. TU Wien could grow the films, Rice had recently installed a powerful microscope that could scan them for defects, and Kono had the terahertz spectrometer to measure optical conductivity. During Bühler-Paschen’s sabbatical visit to Rice that year, she, Si, Kono and Rice microscopy expert Emilie Ringe received support to pursue the project via an Interdisciplinary Excellence Award from Rice’s newly established Creative Ventures program.

    “Conceptually, it was really a dream experiment,” Si said. “Probe the charge sector at the magnetic quantum critical point to see whether it’s critical, whether it has dynamical scaling. If you don’t see anything that’s collective, that’s scaling, the critical point has to belong to some textbook type of description. But, if you see something singular, which in fact we did, then it is very direct and new evidence for the quantum entanglement nature of quantum criticality.”

    Si said all the efforts that went into the study were well worth it, because the findings have far-reaching implications.

    “Quantum entanglement is the basis for storage and processing of quantum information,” Si said. “At the same time, quantum criticality is believed to drive high-temperature superconductivity. So our findings suggest that the same underlying physics — quantum criticality — can lead to a platform for both quantum information and high-temperature superconductivity. When one contemplates that possibility, one cannot help but marvel at the wonder of nature.”

    Si is the Harry C. and Olga K. Wiess Professor in Rice’s Department of Physics and Astronomy. Kono is a professor in Rice’s departments of Electrical and Computer Engineering, Physics and Astronomy, and Materials Science and NanoEngineering and the director of Rice’s Applied Physics Graduate Program. Ringe is now at the University of Cambridge.

    Additional co-authors include Maxwell Andrews, Maximilian Bonta, Werner Schrenk, Andreas Limbeck and Gottfried Strasser, all of the TU Wien; Hermann Detz, formerly of TU Wien and currently at Brno University; Elisabeth Bianco, formerly of Rice and currently at Cornell University; Sadegh Yazdi, formerly of Rice and currently at the University of Colorado Boulder; and co-lead author Donald MacFarland, formerly of TU Wien and currently at the University at Buffalo.

    The research was supported by the European Research Council, the Army Research Office, the Austrian Science Fund, the European Union’s Horizon 2020 program, the National Science Foundation, the Robert A. Welch Foundation, Los Alamos National Laboratory and Rice University.

    RCQM leverages global partnerships and the strengths of more than 20 Rice research groups to address questions related to quantum materials. RCQM is supported by Rice’s offices of the provost and the vice provost for research, the Wiess School of Natural Sciences, the Brown School of Engineering, the Smalley-Curl Institute and the departments of Physics and Astronomy, Electrical and Computer Engineering, and Materials Science and NanoEngineering.

    See the full article here .


    Stem Education Coalition

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    In his 1912 inaugural address, Rice University president Edgar Odell Lovett set forth an ambitious vision for a great research university in Houston, Texas; one dedicated to excellence across the range of human endeavor. With this bold beginning in mind, and with Rice’s centennial approaching, it is time to ask again what we aspire to in a dynamic and shrinking world in which education and the production of knowledge will play an even greater role. What shall our vision be for Rice as we prepare for its second century, and how ought we to advance over the next decade?

    This was the fundamental question posed in the Call to Conversation, a document released to the Rice community in summer 2005. The Call to Conversation asked us to reexamine many aspects of our enterprise, from our fundamental mission and aspirations to the manner in which we define and achieve excellence. It identified the pressures of a constantly changing and increasingly competitive landscape; it asked us to assess honestly Rice’s comparative strengths and weaknesses; and it called on us to define strategic priorities for the future, an effort that will be a focus of the next phase of this process.

  • richardmitnick 9:53 am on October 17, 2019 Permalink | Reply
    Tags: As baffling as the concept of two entangled particles may be the situation becomes even more complex when more particles are involved., At Caltech researchers are focusing their studies on many-body entangled systems., , Entanglement Passes Tests with Flying Colors, In 1935 Albert Einstein Boris Podolsky and Nathan Rosen published a paper on the theoretical concept of quantum entanglement which Einstein called “spooky action at a distance.”, Quantum entanglement, , The perplexing phenomenon of quantum entanglement is central to quantum computing; quantum networking; and the fabric of space and time., The phenomenon of entanglement was first proposed by Albert Einstein and colleagues in the 1930s.   

    From Caltech: “Untangling Quantum Entanglement” 

    Caltech Logo

    From Caltech

    Caltech Magazine Fall 2019
    Whitney Clavin

    In Erwin Schrödinger’s famous thought experiment, a cat is trapped in a box with a bit of poison the release of which is controlled by a quantum process. The cat therefore exists in a quantum state of being both dead and alive until somebody opens the box and finds the cat either dead or alive.

    The perplexing phenomenon of quantum entanglement is central to quantum computing, quantum networking, and the fabric of space and time.

    The famous “Jim twins,” separated soon after birth in the 1940s, seemed to live parallel lives even though they grew up miles apart in completely different families. When they were reunited at the age of 39, they discovered many similarities between their life stories, including the names of their sons, wives, and childhood pets, as well as their preferences for Chevrolet cars, carpentry, and more.

    A similar kind of parallelism happens at a quantum level, too. The electrons, photons, and other particles that make up our universe can become inextricably linked, such that the state observed in one particle will be identical for the other. That connection, known as entanglement, remains strong even across vast distances.

    “When particles are entangled, it’s as if they are born that way, like twins,” says Xie Chen, associate professor of theoretical physics at Caltech. “Even though they might be separated right after birth, [they’ll] still look the same. And they grow up having a lot of personality traits that are similar to each other.”

    The phenomenon of entanglement was first proposed by Albert Einstein and colleagues in the 1930s. At that time, many questioned the validity of entanglement, including Einstein himself. Over the years and in various experiments, however, researchers have generated entangled particles that have supported the theory. In these experiments, researchers first entangle two particles and then send them to different locations miles apart. The researchers then measure the state of one particle: for instance, the polarization (or direction of vibration) of a photon. If that entangled photon displays a horizontal polarization, then so too will its faithful partner.

    “It may be tempting to think that the particles are somehow communicating with each other across these great distances, but that is not the case,” says Thomas Vidick, a professor of computing and mathematical sciences at Caltech. “There can be correlation without communication.” Instead, he explains, entangled particles are so closely connected that there is no need for communication; they “can be thought of as one object.”

    As baffling as the concept of two entangled particles may be, the situation becomes even more complex when more particles are involved. In natural settings such as the human body, for example, not two but hundreds of molecules or even more become entangled, as they also do in various metals and magnets, making up an interwoven community. In these many-body entangled systems, the whole is greater than the sum of its parts.

    “The particles act together like a single object whose identity lies not with the individual components but in a higher plane. It becomes something larger than itself,” says Spyridon (Spiros) Michalakis, outreach manager of Caltech’s Institute for Quantum Information and Matter (IQIM) and a staff researcher. “Entanglement is like a thread that goes through every single one of the individual particles, telling them how to be connected to one another.”

    Associate Professor of Theoretical Physics Xie Chen specializes in the fields of condensed matter physics and quantum information.

    At Caltech, researchers are focusing their studies on many-body entangled systems, which they believe are critical to the development of future technologies and perhaps to cracking fundamental physics mysteries. Scientists around the world have made significant progress applying the principles of many-body entanglement to fields such as quantum computing, quantum cryptography, and quantum networks (collectively known as quantum information); condensed-matter physics; chemistry; and fundamental physics. Although the most practical applications, such as quantum computers, may still be decades off, according to John Preskill, the Richard P. Feynman Professor of Theoretical Physics at Caltech and the Allen V.C. Davis and Lenabelle Davis Leadership Chair of the Institute of Quantum Science and Technology (IQST), “entanglement is a very important part of Caltech’s future.”

    Entanglement Passes Tests with Flying Colors

    In 1935, Albert Einstein, Boris Podolsky, and Nathan Rosen published a paper on the theoretical concept of quantum entanglement, which Einstein called “spooky action at a distance.” The physicists described the idea, then argued that it posed a problem for quantum mechanics, rendering the theory incomplete. Einstein did not believe two particles could remain connected to each other over great distances; doing so, he said, would require them to communicate faster than the speed of light, something he had previously shown to be impossible.

    Today, experimental work leaves no doubt that entanglement is real. Physicists have demonstrated its peculiar effects across hundreds of kilometers; in fact, in 2017, a Chinese satellite named Micius sent entangled photons to three different ground stations, each separated by more than 1,200 kilometers, and broke the distance record for entangled particles.

    Entanglement goes hand in hand with another quantum phenomenon known as superposition, in which particles exist in two different states simultaneously. Photons, for example, can display simultaneously both horizontal and vertical states of polarization.

    Or, to simplify, consider two “entangled” quarters, each hidden under a cup. If two people, Bob and Alice, were each to take one of those quarters to a different room, the quarters would remain both heads and tails until one person lifted the cup and observed his or her quarter; at that point, it would randomly become either heads or tails. If Alice were to lift her cup first and her quarter was tails, then when Bob observed his quarter, it would also be tails. If you repeated the experiment and the coins are covered once more, they would go back to being in a state of superposition. Alice would lift her cup again and might find her quarter as heads this time. Bob would then also find his quarter as heads. Whether the first quarter is found to be heads or tails is entirely random.

    Similarly, when a researcher entangles two photons and then sends each one in different directions under carefully controlled conditions, they will continue to be in a state of superposition, both horizontally and vertically polarized. Only when one of the photons is measured do both randomly adopt just one of the two possible polarization states.

    “Quantum correlations are deeply different than ordinary correlations,” says Preskill. “And randomness is the key. This spooky intrinsic randomness is actually what bothered Einstein. But it is essential to how the quantum world works.”

    “Scientists often use the word correlation to explain what is happening between these particles,” adds Oskar Painter, the John G Braun Professor of Applied Physics and Physics at Caltech. “But, actually, entanglement is the perfect word.”

    Entanglement to the Nth Degree

    Untangling the relationship between two entangled particles may be difficult, but the real challenge is to understand how hundreds of particles, if not more, can be similarly interconnected.

    According to Manuel Endres, an assistant professor of physics at Caltech, one of the first steps toward understanding many-body entanglement is to create and control it in the lab. To do this, Endres and his team use a brute force approach: they design and build laboratory experiments with the goal of creating a system of 100 entangled atoms.

    “This is fundamentally extremely difficult to do,” says Endres. In fact, he notes, it would be difficult even at a much smaller scale. “If I create a system where I generate, for instance, 20 entangled particles, and I send 10 one way and 10 another way, then I have to measure whether each one of those first 10 particles is entangled with each of the other set of 10. There are many different ways of looking at the correlations.”

    While the task of describing those correlations is difficult, describing a system of 100 entangled atoms with classical computer bits would be unimaginably hard. For instance, a complete classical description of all the quantum correlations among as many as 300 entangled particles would require more bits than the number of atoms in the visible universe. “But that’s the whole point and the reason we are doing this,” Endres says. “Things get so entangled that you need a huge amount of space to describe the information. It’s a complicated beast, but it’s useful.”

    “Generally, the number of parameters you need to describe the system is going to scale up exponentially,” says Vidick, who is working on mathematical and computational tools to describe entanglement. “It blows up very quickly, which, in general, is why it’s hard to make predictions or simulations, because you can’t even represent these systems in your laptop’s memory.”

    To solve that problem, Vidick and his group are working on coming up with computational representations of entangled materials that are simpler and more succinct than models that currently exist.

    “Quantum mechanics and the ideas behind quantum computing are forcing us to think outside the box,” he says.

    A Fragile Ecosystem

    Another factor in creating and controlling quantum systems has to do with their delicate nature. Like Mimosa pudica ,a member of the pea family also known as the “sensitive plant,” which droops when its leaves are touched, entangled states can easily disappear, or collapse, when the environment changes even slightly. For example, the act of observing a quantum state destroys it. “You don’t want to even look at your experiment, or breathe on it,” jokes Painter. Adds Preskill, “Don’t turn on the light, and don’t even dare walk into the room.”

    The problem is that entangled particles become entangled with the environment around them quickly, in a matter of microseconds or faster. This then destroys the original entangled state a researcher might attempt to study or use. Even one stray photon flying through an experiment can render the whole thing useless.

    “You need to be able to create a system that is entangled only with itself, not with your apparatus,” says Endres. “We want the particles to talk to one another in a controlled fashion. But we don’t want them to talk to anything in the outside world.”

    In the field of quantum computing, this fragility is problematic because it can lead to computational errors. Quantum computers hold the promise of solving problems that classical computers cannot, including those in cryptography, chemistry, financial modeling, and more. Where classical computers use binary bits (either a “1” or a “0”) to carry information, quantum computers use “qubits,” which exist in states of “1” and “0” at the same time. As Preskill explains, the qubits in this mixed state, or superposition, would be both dead and alive, a reference to the famous thought experiment proposed by Erwin Schrödinger in 1935, in which a cat in a box is both dead and alive until the box is opened, and the cat is observed to be one or the other. What’s more, those qubits are all entangled. If the qubits somehow become disentangled from one another, the quantum computer would be unable to execute its computations.

    To address these issues, Preskill and Alexei Kitaev (Caltech’s Ronald and Maxine Linde Professor of Theoretical Physics and Mathematics and recipient of a 2012 Breakthrough Prize in Fundamental Physics), along with other theorists at Caltech, have devised a concept to hide the quantum information within a global entangled state, such that none of the individual bits have the answer. This approach is akin to distributing a code among hundreds of people living in different cities. No one person would have the whole code, so the code would be much less vulnerable to discovery.

    Manuel Endres, assistant professor of physics, here pictured with Adam Shaw (left) and Ivaylo Madjarov (right), uses laser-based techniques in his lab to create many-body entanglement.

    “The key to correcting errors in entangled systems is, in fact, entanglement,” says Preskill. “If you want to protect information from damage due to the extreme instability of superpositions, you have to hide the information in a form that’s very hard to get at,” he says. “And the way you do that is by encoding it in a highly entangled state.”

    Spreading the Entanglement

    At Caltech, this work on the development of quantum-computing systems is conducted alongside with research into quantum networks in which each quantum computer acts as a separate node, or connection point, for the whole system. Painter refers to this as “breaking a quantum computer into little chunks” and then connecting them together to create a distributed network. In this approach, the chunks would behave as if they were not separated. “The network would be an example of many-body entanglement, in which the bodies are the different nodes in the network,” says Painter.

    Quantum networks would enhance the power of quantum computers, notes Preskill.

    “We’d like to build bigger and bigger quantum computers to solve harder and harder problems. And it’s hard to build one piece of hardware that can handle a million qubits,” he says. “It’s easier to make modular components with 100 qubits each or something like that. But then, if you want to solve harder problems, you’ve got to get these different little quantum computers to communicate with one another. And that would be done through a quantum network.”

    Quantum networks could also be used for cryptography purposes, to make it safer to send sensitive information; they would also be a means by which to distribute and share quantum information in the same way that the World Wide Web works for conventional computers. Another future use might be in astronomy. Today’s telescopes are limited. They cannot yet see any detail on, for instance, the surface of distant exoplanets, where astronomers might want to look for signs of life or civilization. If scientists could combine telescopes into a quantum network, it “would allow us to use the whole Earth as one big telescope with a much-improved resolution,” says Preskill.

    “Up until about 20 years ago, the best way to explore entanglement was to look at what nature gave us and try to study the exotic states that emerged,” notes Painter. “Now our goal is to try to synthesize these systems and go beyond what nature has given us.”

    At the Root of Everything

    While entanglement is the key to advances in quantum-information sciences, it is also a concept of interest to theoretical physicists, some of whom believe that space and time itself are the result of an underlying network of quantum connections.

    “It is quite incredible that any two points in space-time, no matter how far apart, are actually entangled. Points in space-time that we consider closer to each other are just more entangled than those further apart,” says Michalkis.

    The link between entanglement and space-time may even help solve one of the biggest challenges in physics: establishing a unifying theory to connect the macroscopic laws of general relativity (which describe gravity) with the microscopic laws of quantum physics (which describe how subatomic particles behave).

    The quantum error-correcting schemes that Preskill and others study may play a role in this quest. With quantum computers, error correction ensures that the computers are sufficiently robust and stable. Something similar may occur with space-time. “The robustness of space may come from a geometry where you can perturb the system, but it isn’t affected much by the noise, which is the same thing that happens in stable quantum-computing schemes,” says Preskill.

    “Essentially, entanglement holds space together. It’s the glue that makes the different pieces of space hook up with one another,” he adds.

    At Caltech, the concept of entanglement connects various labs and buildings across campus. Theorists and experimentalists in computer science, quantum-information science, condensed-matter physics, and other fields regularly work across disciplines and weave together their ideas.

    “We bring our ideas from condensed-matter physics to quantum-information folks, and we say, ‘Hey, I have a material you can use for quantum computation,’” says Chen. “Sometimes we borrow ideas from them. Many of us from different fields have realized that we have to deal with entanglement head-on.”

    Preskill echoes this sentiment and is convinced entanglement is an essential part of Caltech’s future: “We are making investments and betting on entanglement as being one of the most important themes of 21st-century science.”

    See the full article here .

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    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

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  • richardmitnick 10:33 am on September 19, 2019 Permalink | Reply
    Tags: Classical nonseparability can be applied to acoustic waves not just light waves., From Light to Sound, , Quantum entanglement, , ,   

    From University of Arizona: “Sound of the Future: A New Analog to Quantum Computing” 

    U Arizona bloc

    From University of Arizona

    Sept. 17, 2019
    Emily Dieckman

    University of Arizona engineers are using soundwaves to search through big data with more stability and ease.

    Pierre Deymier (right) and UA President Robert C. Robbins examine the acoustic system that allowed researchers to create Bell states using phonons. (Photo: Paul Tumarkin/Tech Launch Arizona)

    Human beings create a lot of data in the digital age – whether it’s through everyday items like social media posts, emails and Google searches, or more complex information about health, finances and scientific findings.

    The International Data Corp. reported that the global datasphere contained 33 zettabytes, or 33 trillion gigabytes, in 2018. By 2025, they expect that number to grow to 175 zettabytes. 175 zettabytes of information stored on DVDs would fill enough DVDs to circle Earth 222 times.

    While quantum computing has been touted as a way to intelligently sort through big data, quantum environments are difficult to create and maintain. Entangled quantum bit states, or qubits, usually last less than a second before collapsing. Qubits are also highly sensitive to their surrounding environments and must be stored at cryogenic temperatures.

    In a paper Nature Communications Physics, researchers in the University of Arizona Department of Materials Science and Engineering have demonstrated the possibility for acoustic waves in a classical environment to do the work of quantum information processing without the time limitations and fragility.

    “We could run our system for years,” said Keith Runge, director of research in the Department of Materials Science and Engineering and one of the paper’s authors. “It’s so robust that we could take it outside to a tradeshow without it being perturbed at all – earlier this year, we did.”

    Materials science and engineering research assistant professor Arif Hasan led the research. Other co-authors include MSE research assistant professor Lazaro Calderin; undergraduate student Trevor Lata; Pierre Lucas, professor of MSE and optical sciences; and Pierre Deymier, MSE department head, member of the applied mathematics Graduate Interdisciplinary Program, and member of the BIO5 Institute. The team is working with Tech Launch Arizona, the office of the UA that commercializes inventions stemming from research, to patent their device and is investigating commercial pathways to bring the innovation to the public.

    Quantum Superposition

    In classical computing, information is stored as either 0s or 1s, the same way a coin must land on either heads or tails. In quantum computing, qubits can be stored in both states at the same time – a so-called superposition of states. Think of a coin balanced on its side, spinning so quickly that both heads and tails seem to appear at once.

    When qubits are entangled, anything that happens to one qubit affects the other through a principle called nonseparability. In other words, knock down one spinning coin on a table and another spinning coin on the same table falls down, too. A principle called nonlocality keeps the particles linked even if they’re far apart – knock down one spinning coin, and its entangled counterpart on the other side of the universe falls down, too. The entangled qubits create a Bell state, in which all parts of a collective are affected by one another.

    “This is key, because if you manipulate just one qubit, you are manipulating the entire collection of qubits,” Deymier said. “In a regular computer, you have many bits of info stored as 0s or 1s, and you have to address each one of them.”

    From Light to Sound

    But, like a coin spinning on its edge, quantum mechanics are fragile. The act of measuring a quantum state can cause the link to collapse, or decohere – just like how taking a picture of a spinning coin will mean capturing just one side of the coin. That’s why qubit states can only be maintained for short periods.

    But there’s a way around the use of quantum mechanics for data processing: Optical scientists and electrical and computer engineering researchers have demonstrated the ability to create systems of photons, or units of light, that exhibit nonseparability without nonlocality. Though nonlocality is important for specific applications like cryptography, it’s the nonseparability that matters for applications like quantum computing. And particles that are nonseparable in classical Bell states, rather than entangled in a quantum Bell state, are much more stable.

    The materials science and engineering team has taken this a step further by demonstrating for the first time that that classical nonseparability can be applied to acoustic waves, not just light waves. They use phi-bits, units made up of quasi-particles called phonons that transmit sound and heat waves.

    “Light lasers and single photons are part of the field photonics, but soundwaves fall under the umbrella of phononics, or the study of phonons,” Deymier said. “In addition to being stable, classically entangled acoustic waves are easy to interact with and manipulate.”

    Complex Science, Simple Tools

    The materials to demonstrate such a complex concept were simple, including three aluminum rods, enough epoxy to connect them and some rubber bands for elasticity.

    Researchers sent a wave of sound vibrations down the rods, then monitored two degrees of freedom of the waves: what direction the waves moved down the rods (forward or backward) and how the rods moved in relation to one another (whether they were waving in the same direction and at similar amplitudes). To excite the system into a nonseparable state, they identified a frequency at which these two degrees of freedom were linked and sent the waves at that frequency. The result? A Bell state.

    “So, we have an acoustic system that gives us the possibility creating these Bell states,” Deymier said. “It’s the complete analog to quantum mechanics.”

    Demonstrating that this is possible has opened the door to applying classical nonseparability to the emerging field of phononics. Next, the researchers will work to increase the number of degrees of freedom that can be classically entangled – the more, the better. They also want to develop algorithms that can use these nonseparable states to manipulate information.

    Once the system is refined, they plan to resize it from the tabletop down to the microscale, ready to deploy on computer chips in data centers around the world.

    This work was supported by the W.M. Keck Foundation and the National Science Foundation Emerging Frontiers in Research and Innovation Program.

    See the full article here .


    Please help promote STEM in your local schools.

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    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.

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