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  • richardmitnick 5:50 pm on March 6, 2019 Permalink | Reply
    Tags: , For an arbitrary process whose scrambling properties might not be known this method could be used to test whether—or even how much—it scrambles, If information is successfully teleported from one atom to another it means that the state of the first atom is spread out across all of the atoms, If the information was lost successful teleportation would not be possible, In terms of the difficulty of quantum algorithms that have been run we’re toward the top of that list, In the case of the new experiment Information seems lost but it’s actually still hidden in the correlations between the different particles, Information seems lost but it’s actually still hidden in the correlations between the different particles, it means that the state of the first atom is spread out across all of the atoms, JQI, , Researchers at the Joint Quantum Institute have implemented an experimental test for quantum scrambling, The final step relies on quantum teleportation—a method for transferring information between two quantum particles that are potentially very far apart, The protocol may one day help verify the calculations of quantum computers which harness the rules of quantum physics to process information in novel ways, the teleportation is over modest distances—just 35 microns separates the first atom from the seventh, This is a very complicated experiment to run and it takes a very high level of control, This is something that only happens if the information is scrambled   

    From Joint Quantum Institute: “Ion experiment aces quantum scrambling test” 

    JQI bloc

    From Joint Quantum Institute

    March 6, 2019
    Chris Cesare

    1
    Artist conception of information falling into a black hole. Researchers have implemented an experimental test for quantum scrambling, a chaotic shuffling of the information stored among a collection of quantum particles. The experiment was originally inspired by the physics of black holes. Quantum scrambling is one suggestion for how information can fall into a black hole and come out as random-looking radiation. Perhaps, the argument goes, it’s not random at all, and black holes are just excellent scramblers. (Credit E. Edwards/JQI)

    Researchers at the Joint Quantum Institute have implemented an experimental test for quantum scrambling, a chaotic shuffling of the information stored among a collection of quantum particles. Their experiments on a group of seven atomic ions, reported in the March 7 issue of Nature, demonstrate a new way to distinguish between scrambling—which maintains the amount of information in a quantum system but mixes it up—and true information loss. The protocol may one day help verify the calculations of quantum computers, which harness the rules of quantum physics to process information in novel ways.

    “In terms of the difficulty of quantum algorithms that have been run, we’re toward the top of that list,” says Kevin Landsman, a graduate student at JQI and the lead author of the new paper. “This is a very complicated experiment to run, and it takes a very high level of control.”

    The research team, which includes JQI Fellow and UMD Distinguished University Professor Christopher Monroe and JQI Fellow Norbert Linke, performed their scrambling tests by carefully manipulating the quantum behavior of seven charged atomic ions using well-timed sequences of laser pulses. They found that they could correctly diagnose whether information had been scrambled throughout a system of seven atoms with about 80% accuracy.

    “With scrambling, one particle’s information gets blended or spread out into the entire system,” Landsman says. “It seems lost, but it’s actually still hidden in the correlations between the different particles.”

    Quantum scrambling is a bit like shuffling a fresh deck of cards. The cards are initially ordered in a sequence, ace through king, and the suits come one after another. Once it’s sufficiently shuffled, the deck looks mixed up, but—crucially—there’s a way to reverse that process. If you kept meticulous track of how each shuffle exchanged the cards, it would be simple (though tedious) to “unshuffle” the deck by repeating all those exchanges and swaps in reverse.

    Quantum scrambling is similar in that it mixes up the information stored inside a set of atoms and can also be reversed, which is a key difference between scrambling and true, irreversible information loss. Landsman and colleagues used this fact to their advantage in the new test by scrambling up one set of atoms and performing a related scrambling operation on a second set. A mismatch between the two operations would indicate that the process was not scrambling, causing the final step of the method to fail.

    That final step relied on quantum teleportation—a method for transferring information between two quantum particles that are potentially very far apart. In the case of the new experiment, the teleportation is over modest distances—just 35 microns separates the first atom from the seventh—but it is the signature by which the team detects scrambling: If information is successfully teleported from one atom to another, it means that the state of the first atom is spread out across all of the atoms—something that only happens if the information is scrambled. If the information was lost, successful teleportation would not be possible. Thus, for an arbitrary process whose scrambling properties might not be known, this method could be used to test whether—or even how much—it scrambles.

    The authors say that prior tests for scrambling couldn’t quite capture the difference between information being hidden and lost, largely because individual atoms tend to look similar in both cases. The new protocol, first proposed by theorists Beni Yoshida of the Perimeter Institute in Canada, and Norman Yao at the University of California, Berkeley, distinguishes the two cases by taking correlations between particular particles into account in the form of teleportation.

    “When our colleague Norm Yao told us about this teleportation litmus test for scrambling and how it needed at least seven qubits capable of running many quantum operations in a sequence, we knew that our quantum computer was uniquely-suited for the job,” says Linke.

    The experiment was originally inspired by the physics of black holes. Scientists have long pondered what happens when something falls into a black hole, especially if that something is a quantum particle. The fundamental rules of quantum physics suggest that regardless of what a black hole does to a quantum particle, it should be reversible—a prediction that seems at odds with a black hole’s penchant for crushing things into an infinitely small point and spewing out radiation. But without a real black hole to throw things into, researchers have been stuck speculating.

    Quantum scrambling is one suggestion for how information can fall into a black hole and come out as random-looking radiation. Perhaps, the argument goes, it’s not random at all, and black holes are just excellent scramblers. The paper discusses this motivation, as well as an interpretation of the experiment that compares quantum teleportation to information going through a wormhole.

    “Regardless of whether real black holes are very good scramblers, studying quantum scrambling in the lab could provide useful insights for the future development of quantum computing or quantum simulation,” Monroe says.

    In addition to Landsman, Monroe and Linke, the new paper had four other coauthors: Caroline Figgatt, now at Honeywell in Colorado; Thomas Schuster at UC Berkeley; Beni Yoshida at the Perimeter Institute for Theoretical Physics; and Norman Yao at UC Berkeley and Lawrence Berkeley National Laboratory.

    See the full article here .


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    JQI supported by Gordon and Betty Moore Foundation

    We are on the verge of a new technological revolution as the strange and unique properties of quantum physics become relevant and exploitable in the context of information science and technology.

    The Joint Quantum Institute (JQI) is pursuing that goal through the work of leading quantum scientists from the Department of Physics of the University of Maryland (UMD), the National Institute of Standards and Technology (NIST) and the Laboratory for Physical Sciences (LPS). Each institution brings to JQI major experimental and theoretical research programs that are dedicated to the goals of controlling and exploiting quantum systems.

     
  • richardmitnick 3:23 pm on August 3, 2018 Permalink | Reply
    Tags: Boson sampling, Complexity test offers new perspective on small quantum computers, JQI, , Sampling complexity   

    From Joint Quantum Institute: “Complexity test offers new perspective on small quantum computers” 

    JQI bloc

    From Joint Quantum Institute

    August 2, 2018
    Chris Cesare

    1
    Simulating the behavior of quantum particles hopping around on a grid may be one of the first problems tackled by early quantum computers. (Credit: E. Edwards/JQI)

    State-of-the-art quantum devices are not yet large enough to be called full-scale computers. The biggest comprise just a few dozen qubits—a meager count compared to the billions of bits in an ordinary computer’s memory. But steady progress means that these machines now routinely string together 10 or 20 qubits and may soon hold sway over 100 or more.

    In the meantime, researchers are busy dreaming up uses for small quantum computers and mapping out the landscape of problems they’ll be suited to solving. A paper by researchers from the Joint Quantum Institute (JQI) and the Joint Center for Quantum Information and Computer Science (QuICS), published recently in Physical Review Letters, argues that a novel non-quantum perspective may help sketch the boundaries of this landscape (link is external) and potentially even reveal new physics in future experiments.

    The new perspective involves a mathematical tool—a standard measure of computational difficulty known as sampling complexity—that gauges how easy or hard it is for an ordinary computer to simulate the outcome of a quantum experiment. Because the predictions of quantum physics are probabilistic, a single experiment could never verify that these predictions are accurate. You would need to perform many experiments, just like you would need to flip a coin many times to convince yourself that you’re holding an everyday, unbiased nickel.

    If an ordinary computer takes a reasonable amount of time to mimic one run of a quantum experiment—by producing samples with approximately the same probabilities as the real thing—the sampling complexity is low; if it takes a long time, the sampling complexity is high.

    Few expect that quantum computers wielding lots of qubits will have low sampling complexity—after all, quantum computers are expected to be more powerful than ordinary computers, so simulating them on your laptop should be hard. But while the power of quantum computers remains unproven, exploring the crossover from low complexity to high complexity could offer fresh insights about the capabilities of early quantum devices, says Alexey Gorshkov, a JQI and QuICS Fellow who is a co-author of the new paper.

    “Sampling complexity has remained an underappreciated tool,” Gorshkov says, largely because small quantum devices have only recently become reliable. “These devices are now essentially doing quantum sampling, and simulating this is at the heart of our entire field.”

    To demonstrate the utility of this approach, Gorshkov and several collaborators proved that sampling complexity tracks the easy-to-hard transition of a task that small- and medium-sized quantum computers are expected to perform faster than ordinary computers: boson sampling.

    Bosons are one of the two families of fundamental particles (the other being fermions). In general two bosons can interact with one another, but that’s not the case for the boson sampling problem. “Even though they are non-interacting in this problem, bosons are sort of just interesting enough to make boson sampling worth studying,” says Abhinav Deshpande, a graduate student at JQI and QuICS and the lead author of the paper.

    In the boson sampling problem, a fixed number of identical particles are allowed to hop around on a grid, spreading out into quantum superpositions over many grid sites. Solving the problem means sampling from this smeared-out quantum probability cloud, something a quantum computer would have no trouble doing.

    Deshpande, Gorshkov and their colleagues proved that there is a sharp transition between how easy and hard it is to simulate boson sampling on an ordinary computer. If you start with a few well-separated bosons and only let them hop around briefly, the sampling complexity remains low and the problem is easy to simulate. But if you wait longer, an ordinary computer has no chance of capturing the quantum behavior, and the problem becomes hard to simulate.

    The result is intuitive, Deshpande says, since at short times the bosons are still relatively close to their starting positions and not much of their “quantumness” has emerged. For longer times, though, there’s an explosion of possibilities for where any given boson can end up. And because it’s impossible to tell two identical bosons apart from one another, the longer you let them hop around, the more likely they are to quietly swap places and further complicate the quantum probabilities. In this way, the dramatic shift in the sampling complexity is related to a change in the physics: Things don’t get too hard until bosons hop far enough to switch places.

    Gorshkov says that looking for changes like this in sampling complexity may help uncover physical transitions in other quantum tasks or experiments. Conversely, a lack of ramping up in complexity may rule out a quantum advantage for devices that are too error-prone. Either way, Gorshkov says, future results arising from this perspective shift should be interesting. “A deeper look into the use of sampling complexity theory from computer science to study quantum many-body physics is bound to teach us something new and exciting about both fields,” he says.

    See the full article here .

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    We are on the verge of a new technological revolution as the strange and unique properties of quantum physics become relevant and exploitable in the context of information science and technology.

    The Joint Quantum Institute (JQI) is pursuing that goal through the work of leading quantum scientists from the Department of Physics of the University of Maryland (UMD), the National Institute of Standards and Technology (NIST) and the Laboratory for Physical Sciences (LPS). Each institution brings to JQI major experimental and theoretical research programs that are dedicated to the goals of controlling and exploiting quantum systems.

     
  • richardmitnick 7:21 pm on July 5, 2018 Permalink | Reply
    Tags: Able to process 10 billion photonic qubits every second, JQI, Photons have added appeal because they can swiftly shuttle information over long distances and they are compatible with fabricated chips, , , , Semiconductor quantum transistor opens the door for photon-based computing   

    From Joint Quantum Institute: “Semiconductor quantum transistor opens the door for photon-based computing” 

    JQI bloc

    From Joint Quantum Institute

    1
    Researchers demonstrate the first single-photon transistor using a semiconductor chip. They used a single photon, stored in a quantum memory, to toggle the state of other photons. (Credit: E. Edwards/JQI)

    Transistors are tiny switches that form the bedrock of modern computing—billions of them route electrical signals around inside a smartphone, for instance.

    Quantum computers will need analogous hardware to manipulate quantum information. But the design constraints for this new technology are stringent, and today’s most advanced processors can’t be repurposed as quantum devices. That’s because quantum information carriers, dubbed qubits, have to follow different rules laid out by quantum physics.

    Scientists can use many kinds of quantum particles as qubits, even the photons that make up light. Photons have added appeal because they can swiftly shuttle information over long distances and they are compatible with fabricated chips. However, making a quantum transistor triggered by light has been challenging because it requires that the photons interact with each other, something that doesn’t ordinarily happen on its own.

    Now, researchers at the Joint Quantum Institute (JQI), led by JQI Fellow Edo Waks have cleared this hurdle and demonstrated the first single-photon transistor using a semiconductor chip. The device, described in the July 6 issue of Science , is compact: Roughly one million of these new transistors could fit inside a single grain of salt. It is also fast, able to process 10 billion photonic qubits every second.

    “Using our transistor, we should be able to perform quantum gates between photons,” says Waks. “Software running on a quantum computer would use a series of such operations to attain exponential speedup for certain computational problems.

    The photonic chip is made from a semiconductor with numerous holes in it, making it appear much like a honeycomb. Light entering the chip bounces around and gets trapped by the hole pattern; a small crystal called a quantum dot sits inside the area where the light intensity is strongest. Analogous to conventional computer memory, the dot stores information about photons as they enter the device. The dot can effectively tap into that memory to mediate photon interactions—meaning that the actions of one photon affect others that later arrive at the chip.

    “In a single-photon transistor the quantum dot memory must persist long enough to interact with each photonic qubit,” says Shuo Sun, the lead author of the new work who is a Postdoctoral Research Fellow at Stanford University*. “This allows a single photon to switch a bigger stream of photons, which is essential for our device to be considered a transistor.”

    To test that the chip operated like a transistor, the researchers examined how the device responded to weak light pulses that usually contained only one photon. In a normal environment, such dim light might barely register. However, in this device, a single photon gets trapped for a long time, registering its presence in the nearby dot.

    The team observed that a single photon could, by interacting with the dot, control the transmission of a second light pulse through the device. The first light pulse acts like a key, opening the door for the second photon to enter the chip. If the first pulse didn’t contain any photons, the dot blocked subsequent photons from getting through. This behavior is similar to a conventional transistor where a small voltage controls the passage of current through it’s terminals. Here, the researchers successfully replaced the voltage with a single photon and demonstrated that their quantum transistor could switch a light pulse containing around 30 photons before the quantum dot’s memory ran out.

    Waks, who is also a professor in the University of Maryland Department of Electrical and Computer Engineering, says that his team had to test different aspects of the device’s performance prior to getting the transistor to work. “Until now, we had the individual components necessary to make a single photon transistor, but here we combined all of the steps into a single chip,” Waks says.

    Sun says that with realistic engineering improvements their approach could allow many quantum light transistors to be linked together. The team hopes that such speedy, highly connected devices will eventually lead to compact quantum computers that process large numbers of photonic qubits.

    *Other contributors and affiliations

    Edo Waks has affiliations with the University of Maryland Department of Electrical and Computer Engineering (ECE), Department of Physics, Joint Quantum Institute, and the Institute for Research in Electronics and Applied Physics (IREAP).
    Shuo Sun was a UMD graduate student at the time of this research. He is now a postdoctoral research fellow at Stanford University.
    JQI Fellow Glenn Solomon, a physicist at the National Institute of Standards and Technology, grew the sample used in this research.
    Hyochul Kim was a postdoctoral research at UMD at the time of the research. He is now at Samsung Advanced Institute of Technology.
    Zhouchen Luo is currently a UMD ECE graduate student.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    We are on the verge of a new technological revolution as the strange and unique properties of quantum physics become relevant and exploitable in the context of information science and technology.

    The Joint Quantum Institute (JQI) is pursuing that goal through the work of leading quantum scientists from the Department of Physics of the University of Maryland (UMD), the National Institute of Standards and Technology (NIST) and the Laboratory for Physical Sciences (LPS). Each institution brings to JQI major experimental and theoretical research programs that are dedicated to the goals of controlling and exploiting quantum systems.

     
  • richardmitnick 8:24 pm on June 13, 2018 Permalink | Reply
    Tags: , , Exascale supercomputing still to come, JQI, NQI- Congress's National Quantum Initiative, , ,   

    From Science Magazine: “Quantum physics gets attention—and brighter funding prospects—in Congress” 

    AAAS
    From Science Magazine

    Jun. 13, 2018
    Gabriel Popkin

    1
    Ions trapped between gold blades serve as information-carrying qubits in a prototype quantum computer.
    E. EDWARDS/JOINT QUANTUM INSTITUTE

    Many members of Congress admit they find quantum physics mind-boggling, with its counterintuitive account of the subatomic world. But that isn’t stopping U.S. lawmakers, as well as policymakers in President Donald Trump’s administration, from backing an emerging effort to better organize and boost funding for quantum research, which could reshape computing, sensors, and communications.

    ORNL IBM AC922 SUMMIT supercomputer just launched by OLCF at ORNL, and there is more to come as we approach exascale supercomputing

    In the coming weeks, the science committee of the House of Representatives is expected to introduce legislation calling for a new, 10-year-long National Quantum Initiative (NQI). The White House, for its part, is scheduled to formally launch a new panel that will guide the federal government’s role in quantum science. Key science agencies are calling on Congress to accelerate spending on quantum research. And the Senate supports a boost for the field: Last week, it approved a mammoth defense policy bill that includes a provision directing the Pentagon to create a new $20 million quantum science program.

    A yearlong push by a coalition of academic researchers and technology firms helped trigger this flurry of activity. Proponents argue the United States needs a better plan for harvesting the potential fruits of quantum research—and for keeping up with global competitors.

    LLNL IBM Sierra ATS2 supercomputer still to come

    Depiction of ANL ALCF Cray Shasta Aurora supercomputer still to come

    The European Union has launched a decadelong quantum research initiative, and China is said to be investing heavily in the field. The United States is “kind of the only major country that’s not doing something [?],” says Chris Monroe, a physicist at the University of Maryland in College Park and co-founder of a startup developing quantum computers, which could outstrip conventional computers on certain problems. [I guess what is depicted below is someone’s idea of nothing.]

    Quantum computing – IBM I

    IBM Quantum Computing

    Last June, a small group of academics, executives, and lobbyists that includes Monroe released a white paper calling for an NQI; they issued a blueprint for the effort in April. Meanwhile, the House science committee held a hearing on the topic last October and plans to release a bill later this month that draws extensively from the blueprint.

    “We must ensure that the United States does not fall behind other nations that are advancing quantum programs,” Science committee chair Lamar Smith (R–TX) said yesterday in a statement about the bill.

    The legislation will authorize the Department of Energy (DOE) and the National Science Foundation (NSF) to create new research centers at universities, federal laboratories, and nonprofit research institutes, according to a committee spokesperson. These research hubs would aim to build alliances between physicists doing fundamental research, engineers who can build devices, and computer scientists developing quantum algorithms. The centers could give academics seeking to develop commercial technologies access to expertise and expensive research tools, says physicist David Awschalom of the University of Chicago in Illinois, one of the blueprint’s authors. “The research needs rapidly outpace any individual lab,” he says.

    The proposal “sounds really promising,” says Danna Freedman, a chemist at Northwestern University in Evanston, Illinois, who did not contribute to the proposal. But Freedman, who synthesizes materials that could be used to build new kinds of quantum computer components, says her enthusiasm “depends to what extent the government decides to prescribe the research.”

    The blueprint recommends that the hubs focus on three areas: developing ultraprecise quantum sensors for biomedicine, navigation, and other applications; hack-proof quantum communication; and quantum computers. The bill will likely leave it up to federal agencies, the new White House quantum panel, and an outside advisory group to determine the initiative’s focus. Backers also say the effort could help advance the development of software for quantum computers—a major hurdle. Right now, just “tens or hundreds of people” can program quantum computers, says William Zeng of Rigetti Computing, a startup in Berkeley, California, seeking to build a quantum computer and offer quantum computing services. “That’s not going to be able to support building the full potential of the tech.”

    It’s not yet known how much funding the House bill, which Republicans on the science panel are crafting, will recommend. The blueprint envisions channeling $800 million over 5 years to the NQI, but even if the bill endorses that figure, congressional appropriators will have the final say. Also uncertain is whether Democrats will sign on and help ensure passage through the full House, and whether the Senate will support the idea.

    In the meantime, lawmakers and the Trump administration are moving to shore up federal spending on quantum science, which analysts in 2016 estimated at about $200 million a year. Adding to the $20 million boost approved by the Senate (but not yet by the entire Congress), Trump’s 2019 budget request would create a new $30 million “Quantum Leap” initiative at NSF and boost DOE’s quantum research programs to $105 million.

    The United States, long seen as a leader, is facing growing global competition in the quantum field, says Walter Copan, director of the National Institutes of Standards and Technology in Gaithersburg, Maryland, which has long played a role in quantum research. “It is the equivalent of a space race now,” says Copan, who met last week with Smith. Focusing federal resources on the field, Copan adds, “has phenomenal promise for the country—if it’s done right.”

    See the full article here .


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  • richardmitnick 3:48 pm on February 14, 2018 Permalink | Reply
    Tags: , , JQI, New hole-punched crystal clears a path for quantum light, , , UMD   

    From JQI: “New hole-punched crystal clears a path for quantum light” 

    JQI bloc

    Joint Quantum Institute

    February 12, 2018
    E. Edwards

    1
    Optical highways for light are at the heart of modern communications. But when it comes to guiding individual blips of light called photons, reliable transit is far less common. Now, a collaboration of researchers from the Joint Quantum Institute (JQI), led by JQI Fellows Mohammad Hafezi and Edo Waks, has created a photonic chip that both generates single photons, and steers them around. The device, described in the Feb. 9 issue of Science, features a way for the quantum light to seamlessly move, unaffected by certain obstacles.

    “This design incorporates well-known ideas that protect the flow of current in certain electrical devices,” says Hafezi. “Here, we create an analogous environment for photons, one that protects the integrity of quantum light, even in the presence of certain defects.”

    The chip starts with a photonic crystal, which is an established, versatile technology used to create roadways for light. They are made by punching holes through a sheet of semiconductor. For photons, the repeated hole pattern looks very much like a real crystal made from a grid of atoms. Researchers use different hole patterns to change the way that light bends and bounces through the crystal. For instance, they can modify the hole sizes and separations to make restricted lanes of travel that allow certain light colors to pass, while prohibiting others.

    Sometimes, even in these carefully fabricated devices, there are flaws that alter the light’s intended route, causing it to detour into an unexpected direction. But rather than ridding their chips of every flaw, the JQI team mitigates this issue by rethinking the crystal’s hole shapes and crystal pattern. In the new chip, they etch out thousands of triangular holes in an array that resembles a bee’s honeycomb. Along the center of the device they shift the spacing of the holes, which opens a different kind of travel lane for the light. Previously, these researchers predicted that photons moving along that line of shifted holes should be impervious to certain defects because of the overall crystal structure, or topology. Whether the lane is a switchback road or a straight shot, the light’s path from origin to destination should be assured, regardless of the details of the road.

    The light comes from small flecks of semiconductor—dubbed quantum emitters—embedded into the photonic crystal. Researchers can use lasers to prod this material into releasing single photons. Each emitter can gain energy by absorbing laser photons and lose energy by later spitting out those photons, one at time. Photons coming from the two most energetic states of a single emitter are different colors and rotate in opposite directions. For this experiment, the team uses photons from an emitter found near the chip’s center.

    The team tested the capabilities of the chip by first changing a quantum emitter from its lowest energy state to one of its two higher energy states. Upon relaxing back down, the emitter pops out a photon into the nearby travel lane. They continued this process many times, using photons from the two higher energy states. They saw that photons emitted from the two states preferred to travel in opposite directions, which was evidence of the underlying crystal topology.

    To confirm that the design could indeed offer protected lanes of traffic for single photons, the team created a 60 degree turn in the hole pattern. In typical photonic crystals, without built-in protective features, such a kink would likely cause some of the light to reflect backwards or scatter elsewhere. In this new chip, topology protected the photons and allowed them to continue on their way unhindered.

    “On the internet, information moves around in packets of light containing many photons, and losing a few doesn’t hurt you too much”, says co-author Sabyasachi Barik, a graduate student at JQI. “In quantum information processing, we need to protect each individual photon and make sure it doesn’t get lost along the way. Our work can alleviate some forms of loss, even when the device is not completely perfect.”

    The design is flexible, and could allow researchers to systematically assemble pathways for single photons, says Waks. “Such a modular approach may lead to new types of optical devices and enable tailored interactions between quantum light emitters or other kinds of matter.”

    See also:
    Two-dimensionally confined topological edge states in photonic crystals, NEW JOURNAL OF PHYSICS

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    We are on the verge of a new technological revolution as the strange and unique properties of quantum physics become relevant and exploitable in the context of information science and technology.

    The Joint Quantum Institute (JQI) is pursuing that goal through the work of leading quantum scientists from the Department of Physics of the University of Maryland (UMD), the National Institute of Standards and Technology (NIST) and the Laboratory for Physical Sciences (LPS). Each institution brings to JQI major experimental and theoretical research programs that are dedicated to the goals of controlling and exploiting quantum systems.

     
  • richardmitnick 10:31 am on December 10, 2017 Permalink | Reply
    Tags: , JQI, ,   

    From JQI: “Quantum simulators wield control over more than 50 qubits” 

    JQI bloc

    Joint Quantum Institute

    November 29, 2017 [Just appeared in social media.]
    E. Edwards

    Research Contact
    Christopher Monroe
    monroe@umd.edu

    Atoms provide a robust platform for observing quantum magnets in action.

    1
    Artist’s depiction of quantum simulation. Lasers manipulate an array of over 50 atomic qubits in order to study the dynamics of quantum magnetism (credit: E. Edwards/JQI).

    Two independent teams of scientists, including one from the Joint Quantum Institute, have used more than 50 interacting atomic qubits to mimic magnetic quantum matter, blowing past the complexity of previous demonstrations. The results appear in this week’s issue of Nature.

    As the basis for its quantum simulation, the JQI team deploys up to 53 individual ytterbium ions—charged atoms trapped in place by gold-coated and razor-sharp electrodes. A complementary design by Harvard and MIT researchers uses 51 uncharged rubidium atoms confined by an array of laser beams. With so many qubits these quantum simulators are on the cusp of exploring physics that is unreachable by even the fastest modern supercomputers. And adding even more qubits is just a matter of lassoing more atoms into the mix.

    “Each ion qubit is a stable atomic clock that can be perfectly replicated,” says JQI Fellow Christopher Monroe*, who is also the co-founder and chief scientist at the startup IonQ Inc. “They are effectively wired together with external laser beams. This means that the same device can be reprogrammed and reconfigured, from the outside, to adapt to any type of quantum simulation or future quantum computer application that comes up.” Monroe has been one of the early pioneers in quantum computing and his research group’s quantum simulator is part of a blueprint for a general-purpose quantum computer.

    Quantum hardware for a quantum problem

    While modern, transistor-driven computers are great for crunching their way through many problems, they can screech to a halt when dealing with more than 20 interacting quantum objects. That’s certainly the case for quantum magnetism, in which the interactions can lead to magnetic alignment or to a jumble of competing interests at the quantum scale.

    “What makes this problem hard is that each magnet interacts with all the other magnets,” says research scientist Zhexuan Gong, lead theorist and co-author on the study. “With the 53 interacting quantum magnets in this experiment, there are over a quadrillion possible magnet configurations, and this number doubles with each additional magnet. Simulating this large-scale problem on a conventional computer is extremely challenging, if at all possible.”

    When these calculations hit a wall, a quantum simulator may help scientists push the envelope on difficult problems. This is a restricted type of quantum computer that uses qubits to mimic complex quantum matter. Qubits are isolated and well-controlled quantum systems that can be in a combination of two or more states at once. Qubits come in different forms, and atoms—the versatile building blocks of everything—are one of the leading choices for making qubits. In recent years, scientists have controlled 10 to 20 atomic qubits in small-scale quantum simulations.

    Currently, tech industry behemoths, startups and university researchers are in a fierce race to build prototype quantum computers that can control even more qubits. But qubits are delicate and must stay isolated from the environment to protect the device’s quantum nature. With each added qubit this protection becomes more difficult, especially if qubits are not identical from the start, as is the case with fabricated circuits. This is one reason that atoms are an attractive choice that can dramatically simplify the process of scaling up to large-scale quantum machinery.

    An atomic advantage

    Unlike the integrated circuitry of modern computers, atomic qubits reside inside of a room-temperature vacuum chamber that maintains a pressure similar to outer space. This isolation is necessary to keep the destructive environment at bay, and it allows the scientists to precisely control the atomic qubits with a highly engineered network of lasers, lenses, mirrors, optical fibers and electrical circuitry.

    “The principles of quantum computing differ radically from those of conventional computing, so there’s no reason to expect that these two technologies will look anything alike,” says Monroe.

    In the 53-qubit simulator, the ion qubits are made from atoms that all have the same electrical charge and therefore repel one another. But as they push each other away, an electric field generated by a trap forces them back together. The two effects balance each other, and the ions line up single file. Physicists leverage the inherent repulsion to create deliberate ion-to-ion interactions, which are necessary for simulating of interacting quantum matter.

    The quantum simulation begins with a laser pulse that commands all the qubits into the same state. Then, a second set of laser beams interacts with the ion qubits, forcing them to act like tiny magnets, each having a north and south pole. The team does this second step suddenly, which jars the qubits into action. They feel torn between two choices, or phases, of quantum matter. As magnets, they can either align their poles with their neighbors to form a ferromagnet or point in random directions yielding no magnetization. The physicists can change the relative strengths of the laser beams and observe which phase wins out under different laser conditions.

    The entire simulation takes only a few milliseconds. By repeating the process many times and measuring the resulting states at different points during the simulation, the team can see the process as it unfolds from start to finish. The researchers observe how the qubit magnets organize as different phases form, dynamics that the authors say are nearly impossible to calculate using conventional means when there are so many interactions.

    This quantum simulator is suitable for probing magnetic matter and related problems. But other kinds of calculations may need a more general quantum computer with arbitrarily programmable interactions in order to get a boost.

    “Quantum simulations are widely believed to be one of the first useful applications of quantum computers,” says Alexey Gorshkov**, JQI Fellow and co-author of the study. “After perfecting these quantum simulators, we can then implement quantum circuits and eventually quantum-connect many such ion chains together to build a full-scale quantum computer with a much wider domain of applications.”

    As they look to add even more qubits, the team believes that its simulator will embark on more computationally challenging terrain, beyond magnetism. “We are continuing to refine our system, and we think that soon, we will be able to control 100 ion qubits, or more,” says Jiehang Zhang, the study’s lead author and postdoctoral researcher. “At that point, we can potentially explore difficult problems in quantum chemistry or materials design.”

    Written by E. Edwards

    See the full article here .

    Please help promote STEM in your local schools.

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    Stem Education Coalition

    We are on the verge of a new technological revolution as the strange and unique properties of quantum physics become relevant and exploitable in the context of information science and technology.

    The Joint Quantum Institute (JQI) is pursuing that goal through the work of leading quantum scientists from the Department of Physics of the University of Maryland (UMD), the National Institute of Standards and Technology (NIST) and the Laboratory for Physical Sciences (LPS). Each institution brings to JQI major experimental and theoretical research programs that are dedicated to the goals of controlling and exploiting quantum systems.

     
  • richardmitnick 3:46 pm on December 5, 2017 Permalink | Reply
    Tags: , , JQI, , Narrow glass threads synchronize the light emissions of distant atoms, Physicists have extended the range over which atoms can synchronize their light emission by using an optical nanofiber,   

    From JQI: “Narrow glass threads synchronize the light emissions of distant atoms” 

    JQI bloc

    Joint Quantum Institute

    December 4, 2017
    N. Beier

    1
    An optical nanofiber enables interactions between distant atoms, allowing them to synchronize their light emissions. (Credit: E. Edwards/JQI)

    If you holler at someone across your yard, the sound travels on the bustling movement of air molecules. But over long distances your voice needs help to reach its destination—help provided by a telephone or the Internet. Atoms don’t yell, but they can share information through light. And they also need help connecting over long distances.

    Now, researchers at the Joint Quantum Institute (JQI) have shown that nanofibers can provide a link between far-flung atoms, serving as a light bridge between them. Their research, which was conducted in collaboration with the Army Research Lab and the National Autonomous University of Mexico, was published last week in Nature Communications. The new technique could eventually provide secure communication channels between distant atoms, molecules or even quantum dots.

    An excited atom—that is, one with some extra energy—emits light when it loses energy. Usually atoms spit this light out in random directions and at different times. But this random process can be tamed if excited atoms are bunched up close together. In that case, atoms can sync up their light emissions, like the rhythmic clapping of an appreciative audience. However, this synchronization effect, which is caused by light of different atoms joining together, doesn’t reach very far because the strength of light weakens drastically over short distances. While your neighbor might hear you yelling over several meters, atoms need to be really close to interact with each other—typically closer than one micron, which is a hundred times smaller than the width of a human hair.

    Now, physicists have extended the range over which atoms can synchronize their light emission by using an optical nanofiber. In an experiment, the researchers immerse a nanofiber in a cloud of cold rubidium atoms and excite the atoms with a laser beam. As atoms in the cloud move around, they sometimes get very close to the fiber. If an atom emits light near the fiber, the glass thread can capture the light and pipe it to another atom, even if the atoms are far apart.

    The team observed a group of atoms emitting light pulses at different rates than their ordinary, unsynchronized selves—one signature of these far-reaching interactions. The effect persisted even when physicists cleaved the atomic cloud in two so that atoms in separate clouds could only connect through the fiber, and not through other atoms in the cloud.

    The atoms in this experiment are only separated by distances of a few pieces of paper, but the authors say that longer distances—meters or even kilometers—should be doable. “We have shown that optical nanofibers are excellent for connecting atoms that are quite far apart—if the atoms were the size of people, it would be a distance of more than 300 kilometers,” says Pablo Solano, the lead author of the paper and a former JQI graduate student.* “The question now is not whether the atoms interact, but how far can we push their optical-fiber-mediated connections.” On the scale of atoms even a few meters is an enormous distance. But the authors say that a combination of optical nanofibers and regular fiber optics—technologies already deployed for long-distance phone calls, cable TV and the Internet—could extend the range of these atomic connections even farther.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    We are on the verge of a new technological revolution as the strange and unique properties of quantum physics become relevant and exploitable in the context of information science and technology.

    The Joint Quantum Institute (JQI) is pursuing that goal through the work of leading quantum scientists from the Department of Physics of the University of Maryland (UMD), the National Institute of Standards and Technology (NIST) and the Laboratory for Physical Sciences (LPS). Each institution brings to JQI major experimental and theoretical research programs that are dedicated to the goals of controlling and exploiting quantum systems.

     
  • richardmitnick 8:17 am on September 7, 2016 Permalink | Reply
    Tags: A sharper eye on ions, , JQI, Optical systems   

    From JQI: “A sharper eye on ions” 

    JQI bloc

    Joint Quantum Institute

    September 6, 2016
    No writer credit found

    1
    Artist’s conception of an the imaging system and ion. A version of this image is featured on the cover of the September issue of Nature Photonics. Credit S. Kelley, JQI

    Optical systems, like your eye, sometimes need help to produce a crystal clear image. And it’s not just a problem for eyes. Research labs, too, worry about aberrations and distortions that lead to image inaccuracies. JQI physicists have implemented a novel imaging technique that adapts to these destructive errors and corrects them. They combine high performance lenses, akin to an artificial eye, with computer processing to capture an image of a single atomic ion and its motion with unprecedented nanoscale sensitivity. The research is featured on the cover of the September issue of Nature Photonics.

    Image formation depends on the way light coming from an object is collected and processed. For instance, the cornea and lens focus light waves as they enter the eye, forming an image on the retina. The clarity of this snapshot depends on the quality of the light. Objects appear blurry if the lenses bend light waves too much or too little, something we correct for by using glasses or contacts. Even with these errors, the brain excels at using contextual cues to analyze an image and grasp its concept. The idea of adaptive optics is similar to corrective eyewear.

    To see a single ion, researchers must collect light from a lone, point-like object hovering inside a vacuum chamber. A laser illuminates the ion, causing it to emit light, which is then collected on a CCD camera, analogous to the retina. But first, the light passes through a vacuum window, two stages of optical magnification, and lenses that correct for astigmatism, all of which introduce distortion. This set of optics, called a microscope objective, combine with a camera to form the effective eye of the system. A computer acts as a brain, processing the camera signal.

    The researchers characterized the way an ion emitted light by fitting combinations of mathematical curves to the collected data. From these fits, they could determine how to manually adjust the microscope objective’s position to obtain a cleaner, sharper image. Notably, this imaging system was able to detect ion movements of mere nanometers–changes more than 1000 times smaller than the size of a red blood cell.

    Beyond optimized ion pictures, the team plans to use this sensitive imaging system to measure quantum superpositions of two different motional states of a single ion. And the method, although applied here to atomic physics, could be translated to biology and astronomy, where point-like light sources are also common.

    High-resolution adaptive imaging of a single atom, J. D. Wong-Campos, K. G. Johnson, B. Neyenhuis, J. Mizrahi & C. Monroe, Nature Photonics doi:10.1038/nphoton.2016.136

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    We are on the verge of a new technological revolution as the strange and unique properties of quantum physics become relevant and exploitable in the context of information science and technology.

    The Joint Quantum Institute (JQI) is pursuing that goal through the work of leading quantum scientists from the Department of Physics of the University of Maryland (UMD), the National Institute of Standards and Technology (NIST) and the Laboratory for Physical Sciences (LPS). Each institution brings to JQI major experimental and theoretical research programs that are dedicated to the goals of controlling and exploiting quantum systems.

     
  • richardmitnick 2:58 pm on June 30, 2016 Permalink | Reply
    Tags: , JQI, ,   

    From JQI: “Ultra-cold atoms may wade through quantum friction” 

    JQI bloc

    Joint Quantum Institute

    June 24, 2016

    Research Contact
    Dmitry Efimkin
    efimkindk@utexas.edu

    Victor Galitski
    galitski@physics.umd.edu

    Johannes Hofmann
    jbh38@cam.ac.uk

    Media Contact
    Chris Cesare
    ccesare@umd.edu

    1
    A soliton made of atoms rolls like a marble in a one-dimensional trap created by lasers. Credit: S. Kelley/NIST

    Theoretical physicists studying the behavior of ultra-cold atoms have discovered a new source of friction, dispensing with a century-old paradox in the process. Their prediction, which experimenters may soon try to verify, was reported recently in Physical Review Letters.

    The friction afflicts certain arrangements of atoms in a Bose-Einstein Condensate (BEC), a quantum state of matter in which the atoms behave in lockstep. In this state, well-tuned magnetic fields can cause the atoms to attract one another and even bunch together, forming a single composite particle known as a soliton.

    Solitons appear in many areas of physics and are exceptionally stable. They can travel freely, without losing energy or dispersing, allowing theorists to treat them like everyday, non-quantum objects. Solitons composed of photons—rather than atoms—are even used for communication over optical fibers.

    Studying the theoretical properties of solitons can be a fruitful avenue of research, notes Dmitry Efimkin, the lead author of the paper and a former JQI postdoctoral researcher now at the University of Texas at Austin. “Friction is very fundamental, and quantum mechanics is now quite a well-tested theory,” Efimkin says. “This work investigates the problem of quantum friction for solitons and marries these two fundamental areas of research.”

    Efimkin, along with JQI Fellow Victor Galitski and Johannes Hofmann, a physicist at the University of Cambridge, sought to answer a basic question about soliton BECs: Does an idealized model of a soliton have any intrinsic friction?

    Prior studies seemed to say no. Friction arising from billiard-ball-like collisions between a soliton and stray quantum particles was a possibility, but the mathematics prohibited it. For a long time, then, theorists believed that the soliton moved through its cloudy quantum surroundings essentially untouched.

    But those prior studies did not give the problem a full quantum consideration, Hofmann says. “The new work sets up a rigorous quantum-mechanical treatment of the system,” he says, adding that this theoretical approach is what revealed the new frictional force.

    It’s friction that is familiar from a very different branch of physics. When a charged particle, such as an electron, is accelerated, it emits radiation. A long-known consequence is that the electron will experience a friction force as it is accelerated, caused by the recoil from the radiation it releases.

    Instead of being proportional to the speed of the electron, as is friction like air resistance, this force instead depends on the jerk—the rate at which the electron’s acceleration is changing. Intriguingly, this is the same frictional force that appears in the quantum treatment of the soliton, with the soliton’s absorption and emission of quantum quasiparticles replacing the electron’s emission of radiation.

    2
    Infographic credit: S. Kelley/NIST and C. Cesare/JQI

    At the heart of this frictional force, however, lurks a problem. Including it in the equations describing the soliton’s motion—or an accelerated electron’s—reveals that the motion in the present depends on events in the future, a result that inverts the standard concept of causality. It’s a situation that has puzzled physicists for decades.

    The team tracked down the origin of these time-bending predictions and dispensed with the paradox. The problem arises from a step in the calculation that assumes the friction force only depends on the current state of the soliton. If, instead, it also depends on the soliton’s past trajectory, the paradox disappears.

    Including this dependence on the soliton’s history leads to nearly the same equations governing its motion, and those equations still include the new friction. It’s as if the quantum background retains a memory of the soliton’s path.

    Hofmann says that BECs provide a pristine system to search for the friction. Experimenters can apply lasers that set the atomic soliton in motion, much like a marble rolling around a bowl—although the bowl is tightly squeezed in one dimension. Observing the frequency and amplitude of this motion, as well as how it changes over time, could reveal the friction’s signature. “Using some typical experimental parameters, we think that the magnitude of this force is large enough to be observable in current experiments,” Hofmann says.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    We are on the verge of a new technological revolution as the strange and unique properties of quantum physics become relevant and exploitable in the context of information science and technology.

    The Joint Quantum Institute (JQI) is pursuing that goal through the work of leading quantum scientists from the Department of Physics of the University of Maryland (UMD), the National Institute of Standards and Technology (NIST) and the Laboratory for Physical Sciences (LPS). Each institution brings to JQI major experimental and theoretical research programs that are dedicated to the goals of controlling and exploiting quantum systems.

    See the full article here .

     
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