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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 .


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    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” 

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    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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  • 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 .


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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.

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

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

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  • richardmitnick 7:47 am on September 2, 2019 Permalink | Reply
    Tags: "Physicists Have Finally Built a Quantum X-Ray Device", , Bar Ilon University, PDC-parametric down-conversion, , Quantum enhancement, Quantum entanglement, Quantum illumination, Quantum imaging, , , X-ray PDC,   

    From Bar Ilon University and Riken via Science Alert: “Physicists Have Finally Built a Quantum X-Ray Device” 


    From Bar Ilon University


    RIKEN bloc

    From RIKEN



    Science Alert

    2 SEP 2019

    (APS/Alan Stonebraker)

    A team of researchers has just demonstrated quantum enhancement in an actual X-ray machine, achieving the desirable goal of eliminating background noise for precision detection.

    The relationships between photon pairs on quantum scales can be exploited to create sharper, higher-resolution images than classical optics. This emerging field is called quantum imaging, and it has some really impressive potential – particularly since, using optical light, it can be used to show objects that can’t usually be seen, like bones and organs.

    Quantum correlation describes a number of different relationships between photon pairs. Entanglement is one of these, and is applied in optical quantum imaging.

    But the technical challenges of generating entangled photons in X-ray wavelengths are considerably greater than for optical light, so in the building of their quantum X-ray, the team took a different approach.

    They used a technique called quantum illumination to minimise background noise. Usually, this uses entangled photons, but weaker correlations work, too. Using a process called parametric down-conversion (PDC), the researchers split a high-energy – or “pump” – photon into two lower-energy photons, called a signal photon and an idler photon.

    “X-ray PDC has been demonstrated by several authors, and the application of the effect as a source for ghost imaging has been demonstrated recently,” the researchers write in their paper.

    “However, in all previous publications, the photon statistics have not been measured. Essentially, to date, there is no experimental evidence that photons, which are generated by X-ray PDC, exhibit statistics of quantum states of radiation. Likewise, observations of the quantum enhanced measurement sensitivity have never been reported at X-ray wavelengths.”

    The researchers achieved their X-ray PDC with a diamond crystal. The nonlinear structure of the crystal splits a beam of pump X-ray photons into signal and idler beams, each with half the energy of the pump beam.

    Normally, this process is very inefficient using X-rays, so the team scaled up the power. Using the SPring-8 synchrotron in Japan, they shot a 22 KeV beam of X-rays at their crystal, which split into two beams, each carrying 11 KeV.

    SPring-8 synchrotron

    SPring-8 synchrotron, located in Hyōgo Prefecture, Japan

    The signal beam is sent towards the object to be imaged – in the case of this research, a small piece of metal with three slits – with a detector on the other side. The idler beam is sent straight to a different detector. This is set up so that each beam hits its respective detector at the same place and at the same time.

    “The perfect time-energy relationship we observed could only mean that the two photons were quantum correlated,” said physicist Sason Sofer of Bar-Ilan University in Israel.

    For the next step, the researchers compared their detections. There were only around 100 correlated photons per point in the image, and around 10,000 more background photons. But the researchers could match each idler to a signal, so they could actually tell which photons in the image were from the beam, thus easily separating out the background noise.

    They then compared these images to images taken using regular, non-correlated photons – and the correlated photons clearly produced a much sharper image.

    It’s early days yet, but it’s definitely a step in the right direction for what could be a greatly exciting tool. Quantum X-ray imaging could have a number of uses outside the range of current X-ray technology.

    One promise is that it could lower the amount of radiation required for X-ray imaging. This would mean that samples easily damaged by X-rays could be imaged, or samples that require low temperatures; less radiation would mean less heat. It could also enable physicists to X-ray atomic nuclei to see what’s inside.

    Obviously, since these quantum X-rays require a hardcore particle accelerator, medical applications are currently off the table. The team has demonstrated that it can be done, but scaling down is going to be tricky.

    Currently, determining whether the photons are entangled is the next step. That would require the photons’ arrival at the detectors to be measured within attosecond scales, which is beyond our current technology.

    Still, this is a pretty amazing achievement.

    “We have demonstrated the ability to utilise the strong time-energy correlations of photon pairs for quantum enhanced photodetection. The procedure we have presented possesses great potential for improving the performances of X-ray measurements,” the researchers write.

    “We anticipate that this work will open the way for more quantum enhanced x-ray regime detection schemes, including the area of diffraction and spectroscopy.”

    The research has been published in Physical Review X.

    See the full article here .


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    RIKEN is Japan’s largest comprehensive research institution renowned for high-quality research in a diverse range of scientific disciplines. Founded in 1917 as a private research foundation in Tokyo, RIKEN has grown rapidly in size and scope, today encompassing a network of world-class research centers and institutes across Japan.

  • richardmitnick 9:50 am on July 29, 2019 Permalink | Reply
    Tags: "Engineering a Fast Two-Qubit Gate in Silicon", , “We were able to bring the qubit’s electrons closer or further apart effectively turning on and off the interaction between them- a prerequisite for a quantum gate” said Yu He., , Long coherence times- the ability to hang onto delicate quantum information for more than instant., , Quantum entanglement, Qubits transistor and leads, Scanning tunneling microscope hydrogen lithography, The big problem has been getting these atoms close enough together to “talk” to one another in a quantum-mechanical sense.,   

    From UNSW via Optics & Photonics: “Engineering a Fast Two-Qubit Gate in Silicon” 

    U NSW bloc

    From University of New South Wales

    Optics & Photonics

    Stewart Wills

    In a tour-de-force of atom-scale engineering, a research team at the University of New South Wales (UNSW), Australia, has demonstrated a two-qubit gate between coupled donor atom qubits in silicon—the first time, according to the researchers, that such a feat has been accomplished (Nature). The work potentially overcomes one significant hurdle in building quantum computers with atom-based qubits on a silicon platform.

    The research team behind the UNSW work on atom-based qubits in silicon included (left to right) co-lead-authors Sam Gorman and Yu He, team leader Michelle Simmons, Ludwik Kranz, Joris Keizer and Daniel Keith. [Image: UNSW Sydney]

    Bringing atom qubits to silicon

    Atom- and ion-based qubits have some notable attractions as candidates for quantum computing. A particular plus is these systems’ long coherence times, the ability to hang onto delicate quantum information for more than instant. This and other advantages have made assemblages of ions or atoms trapped in lattices of laser beams a key locus of advances in quantum research, with some standout recent accomplishments, for example, in quantum simulation.

    Technologists and engineers would like to bring some of those same advantages of atom-based qubits to silicon. In principle, that would mean that efforts to build quantum computers could leverage the infrastructure and techniques honed over decades in fashioning semiconductors for classical computers.

    Moreover, as Michelle Simmons, the leader of the UNSW team, noted in a press release accompanying the research, electron-spin qubits donated by single atoms “hold the world record” for qubits in silicon under several metrics. Previous work has shown, for example, that such qubits in silicon can have coherence times in the seconds, with potential gate fidelities (and, hence, coherent control) on the order of 99.9%.

    The big problem has been getting these atoms close enough together to “talk” to one another in a quantum-mechanical sense—through phenomena such as entanglement—and thus form quantum-computational logic gates, while still maintaining the ability to control and measure each atom qubit individually. As a result, while a number of research teams have demonstrated two-qubit gates in silicon using qubits bigger than individual atoms, such as quantum dots, the same feat hadn’t yet been achieved for individual-atoms-based qubits until the recent work by the UNSW team.

    STM hydrogen lithography

    To create such a two-qubit gate between atom-based qubits, Simmons and her team used a technique, scanning tunneling microscope (STM) hydrogen lithography, that the research group has been honing for some 20 years.

    The method begins with a natural silicon substrate—the surface of which, through a number of high-temperature chemical steps, the researchers then coat with a layer of monoatomic hydrogen. Next, the tip of an STM is used to individually pick off hydrogen atoms from that surface, creating an atom-scale lithographic mask on the surface, with nanometer precision. Finally, the surface is exposed to a phosphorous–hydrogen gas at 350 °C, leaving behind phosphorous in the exposed areas.

    The UNSW team’s STM hydrogen lithography technique allowed it to construct a two-qubit logic gate consisting of phosphorous atoms placed a mere 13 nm apart, along with associated circuitry. [Image: UNSW Sydney Media Office]

    Qubits, transistor and leads

    By applying this method, the team was able to deposit phosphorous atom qubits—a left qubit consisting of two phosphorous atoms, and a right qubit including three—separated by a mere 13 nm. (The left–right asymmetry between the number of donor atoms was engineered intentionally, according to the paper, in part to increase the tunability of the exchange interaction between the qubits.)

    The researchers also used the technique to lay down associated circuitry for a quantum gate between the two qubits. That circuitry included source and drain leads, as well as a nearby single-electron transistor that serves, through weak tunnel-coupling with the qubits, as an electron reservoir and charge sensor.

    The team then popped the fabricated device into 50-mK dilution refrigerator, and tested its ability to implement a particular quantum logic gate—a so-called (SWAP)½ gate—on a variety of electron spin basis states from the donor atoms. The team was able to read out the gate results with 94% fidelity.

    “We were able to bring the qubit’s electrons closer or further apart, effectively turning on and off the interaction between them, a prerequisite for a quantum gate,” Yu He, one of the paper’s two lead co-authors (along with Sam Gorman), said in a press release. And the gate operation was blazingly fast, with the two-qubit SWAP exchange happening in a mere 800 ps.

    Exquisite engineering

    In an email to OPN, Simmons noted that one of the key points of the paper was the exquisite engineering that the technique allows. “We engineer the atoms to be [around] 13nm apart, to create entanglement,” she said, “but at the same time have the control to independently measure one qubit with high fidelity, without altering the neighboring qubit despite their close proximity.”

    Simmons added that the fact that the platform uses only phosphorous and silicon atoms allows (as the team had shown in previous work) “very low noise quantum circuitry.” That’s because the system “[gets] rid of any dielectrics of different materials, which typically cause charge noise and/or irregularities at the interfaces found in semiconductor quantum dots.”

    In the paper, the team noted that in the long run, the hope is that, by leveraging these techniques, the group can “utilize the hallmark long coherence times that are normally associated with ion trap qubits together with the scalability of the silicon material system to realize a large-scale quantum processor.” Simmons told OPN that she and her colleagues are “excited about the possibilities,” but also noted that the work is still at an early stage. “Watch this space,” she said.

    Joris Keizer, Michelle Simmons and Yu He in the lab. [Image: UNSW Sydney Media Office]

    See the full article here .


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  • richardmitnick 11:59 am on July 28, 2019 Permalink | Reply
    Tags: A quantum particle can have a range of possible states known as a “superposition.”, “Quantum-classical transition.”, But why can’t we see a quantum superposition?, , Darwin-Survival of the Fittest, Many independent observers can make measurements of a quantum system and agree on the outcome—a hallmark of classical behavior., Quantum Darwinism, Quantum entanglement, , The definite properties of objects that we associate with classical physics—position and speed say—are selected from a menu of quantum possibilities., The process is loosely analogous to natural selection in evolution., The vexing question then becomes: How do quantum probabilities coalesce into the sharp focus of the classical world?, This doesn’t really mean it is in several states at once; rather it means that if we make a measurement we will see one of those outcomes., This process by which “quantumness” disappears into the environment is called decoherence.,   

    From WIRED: “Quantum Darwinism Could Explain What Makes Reality Real” 

    Wired logo

    From WIRED

    Philip Ball

    Contrary to popular belief, says physicist Adán Cabello, “quantum theory perfectly describes the emergence of the classical world.” Olena Shmahalo/Quanta Magazine

    It’s not surprising that quantum physics has a reputation for being weird and counterintuitive. The world we’re living in sure doesn’t feel quantum mechanical. And until the 20th century, everyone assumed that the classical laws of physics devised by Isaac Newton and others—according to which objects have well-defined positions and properties at all times—would work at every scale. But Max Planck, Albert Einstein, Niels Bohr and their contemporaries discovered that down among atoms and subatomic particles, this concreteness dissolves into a soup of possibilities. An atom typically can’t be assigned a definite position, for example—we can merely calculate the probability of finding it in various places. The vexing question then becomes: How do quantum probabilities coalesce into the sharp focus of the classical world?

    Physicists sometimes talk about this changeover as the “quantum-classical transition.” But in fact there’s no reason to think that the large and the small have fundamentally different rules, or that there’s a sudden switch between them. Over the past several decades, researchers have achieved a greater understanding of how quantum mechanics inevitably becomes classical mechanics through an interaction between a particle or other microscopic system and its surrounding environment.

    One of the most remarkable ideas in this theoretical framework is that the definite properties of objects that we associate with classical physics—position and speed, say—are selected from a menu of quantum possibilities in a process loosely analogous to natural selection in evolution: The properties that survive are in some sense the “fittest.” As in natural selection, the survivors are those that make the most copies of themselves. This means that many independent observers can make measurements of a quantum system and agree on the outcome—a hallmark of classical behavior.

    This idea, called quantum Darwinism (QD), explains a lot about why we experience the world the way we do rather than in the peculiar way it manifests at the scale of atoms and fundamental particles. Although aspects of the puzzle remain unresolved, QD helps heal the apparent rift between quantum and classical physics.

    Chaoyang Lu (left) and Jian-Wei Pan of the University of Science and Technology of China in Hefei led a recent experiment that tested quantum Darwinism in an artificial environment made of interacting photons. Chaoyang Lu

    Only recently, however, has quantum Darwinism been put to the experimental test. Three research groups, working independently in Italy, China and Germany, have looked for the telltale signature of the natural selection process by which information about a quantum system gets repeatedly imprinted on various controlled environments. These tests are rudimentary, and experts say there’s still much more to be done before we can feel sure that QD provides the right picture of how our concrete reality condenses from the multiple options that quantum mechanics offers. Yet so far, the theory checks out.

    Survival of the Fittest

    At the heart of quantum Darwinism is the slippery notion of measurement—the process of making an observation. In classical physics, what you see is simply how things are. You observe a tennis ball traveling at 200 kilometers per hour because that’s its speed. What more is there to say?

    In quantum physics that’s no longer true. It’s not at all obvious what the formal mathematical procedures of quantum mechanics say about “how things are” in a quantum object; they’re just a prescription telling us what we might see if we make a measurement. Take, for example, the way a quantum particle can have a range of possible states, known as a “superposition.” This doesn’t really mean it is in several states at once; rather, it means that if we make a measurement we will see one of those outcomes. Before the measurement, the various superposed states interfere with one another in a wavelike manner, producing outcomes with higher or lower probabilities.

    But why can’t we see a quantum superposition? Why can’t all possibilities for the state of a particle survive right up to the human scale?

    The answer often given is that superpositions are fragile, easily disrupted when a delicate quantum system is buffeted by its noisy environment. But that’s not quite right. When any two quantum objects interact, they get “entangled” with each other, entering a shared quantum state in which the possibilities for their properties are interdependent. So say an atom is put into a superposition of two possible states for the quantum property called spin: “up” and “down.” Now the atom is released into the air, where it collides with an air molecule and becomes entangled with it. The two are now in a joint superposition. If the atom is spin-up, then the air molecule might be pushed one way, while, if the atom is spin-down, the air molecule goes another way—and these two possibilities coexist. As the particles experience yet more collisions with other air molecules, the entanglement spreads, and the superposition initially specific to the atom becomes ever more diffuse. The atom’s superposed states no longer interfere coherently with one another because they are now entangled with other states in the surrounding environment—including, perhaps, some large measuring instrument. To that measuring device, it looks as though the atom’s superposition has vanished and been replaced by a menu of possible classical-like outcomes that no longer interfere with one another.

    This process by which “quantumness” disappears into the environment is called decoherence. It’s a crucial part of the quantum-classical transition, explaining why quantum behavior becomes hard to see in large systems with many interacting particles. The process happens extremely fast. If a typical dust grain floating in the air were put into a quantum superposition of two different physical locations separated by about the width of the grain itself, collisions with air molecules would cause decoherence—making the superposition undetectable—in about 10−31 seconds. Even in a vacuum, light photons would trigger such decoherence very quickly: You couldn’t look at the grain without destroying its superposition.

    Surprisingly, although decoherence is a straightforward consequence of quantum mechanics, it was only identified in the 1970s, by the late German physicist Heinz-Dieter Zeh. The Polish-American physicist Wojciech Zurek further developed the idea in the early 1980s and made it better known, and there is now good experimental support for it.

    Wojciech Zurek, a theoretical physicist at Los Alamos National Laboratory in New Mexico, developed the quantum Darwinism theory in the 2000s to account for the emergence of objective, classical reality. Los Alamos National Laboratory

    But to explain the emergence of objective, classical reality, it’s not enough to say that decoherence washes away quantum behavior and thereby makes it appear classical to an observer. Somehow, it’s possible for multiple observers to agree about the properties of quantum systems. Zurek, who works at Los Alamos National Laboratory in New Mexico, argues that two things must therefore be true.

    First, quantum systems must have states that are especially robust in the face of disruptive decoherence by the environment. Zurek calls these “pointer states,” because they can be encoded in the possible states of a pointer on the dial of a measuring instrument. A particular location of a particle, for instance, or its speed, the value of its quantum spin, or its polarization direction can be registered as the position of a pointer on a measuring device. Zurek argues that classical behavior—the existence of well-defined, stable, objective properties—is possible only because pointer states of quantum objects exist.

    What’s special mathematically about pointer states is that the decoherence-inducing interactions with the environment don’t scramble them: Either the pointer state is preserved, or it is simply transformed into a state that looks nearly identical. This implies that the environment doesn’t squash quantumness indiscriminately but selects some states while trashing others. A particle’s position is resilient to decoherence, for example. Superpositions of different locations, however, are not pointer states: Interactions with the environment decohere them into localized pointer states, so that only one can be observed. Zurek described this “environment-induced superselection” of pointer states in the 1980s [Physical Review D].

    But there’s a second condition that a quantum property must meet to be observed. Although immunity to interaction with the environment assures the stability of a pointer state, we still have to get at the information about it somehow. We can do that only if it gets imprinted in the object’s environment. When you see an object, for example, that information is delivered to your retina by the photons scattering off it. They carry information to you in the form of a partial replica of certain aspects of the object, saying something about its position, shape and color. Lots of replicas are needed if many observers are to agree on a measured value—a hallmark of classicality. Thus, as Zurek argued in the 2000s, our ability to observe some property depends not only on whether it is selected as a pointer state, but also on how substantial a footprint it makes in the environment. The states that are best at creating replicas in the environment—the “fittest,” you might say—are the only ones accessible to measurement. That’s why Zurek calls the idea quantum Darwinism [Nature Physics].

    It turns out that the same stability property that promotes environment-induced superselection of pointer states also promotes quantum Darwinian fitness, or the capacity to generate replicas. “The environment, through its monitoring efforts, decoheres systems,” Zurek said, “and the very same process that is responsible for decoherence should inscribe multiple copies of the information in the environment.”

    Information Overload

    It doesn’t matter, of course, whether information about a quantum system that gets imprinted in the environment is actually read out by a human observer; all that matters for classical behavior to emerge is that the information get there so that it could be read out in principle. “A system doesn’t have to be under study in any formal sense” to become classical, said Jess Riedel, a physicist at the Perimeter Institute for Theoretical Physics in Waterloo, Canada, and a proponent of quantum Darwinism.

    “QD putatively explains, or helps to explain, all of classicality, including everyday macroscopic objects that aren’t in a laboratory, or that existed before there were any humans.”

    About a decade ago, while Riedel was working as a graduate student with Zurek, the two showed theoretically that information from some simple, idealized quantum systems is “copied prolifically into the environment,” Riedel said, “so that it’s necessary to access only a small amount of the environment to infer the value of the variables.” They calculated [Physical Review Letters] that a grain of dust one micrometer across, after being illuminated by the sun for just one microsecond, will have its location imprinted about 100 million times in the scattered photons.

    It’s because of this redundancy that objective, classical-like properties exist at all. Ten observers can each measure the position of a dust grain and find that it’s in the same location, because each can access a distinct replica of the information. In this view, we can assign an objective “position” to the speck not because it “has” such a position (whatever that means) but because its position state can imprint many identical replicas in the environment, so that different observers can reach a consensus.

    What’s more, you don’t have to monitor much of the environment to gather most of the available information—and you don’t gain significantly more by monitoring more than a fraction of the environment. “The information one can gather about the system quickly saturates,” Riedel said.

    This redundancy is the distinguishing feature of QD, explained Mauro Paternostro, a physicist at Queen’s University Belfast who was involved in one of the three new experiments. “It’s the property that characterizes the transition towards classicality,” he said.

    Quantum Darwinism challenges a common myth about quantum mechanics, according to the theoretical physicist Adán Cabello of the University of Seville in Spain: namely, that the transition between the quantum and classical worlds is not understood and that measurement outcomes cannot be described by quantum theory. On the contrary, he said, “quantum theory perfectly describes the emergence of the classical world.”

    Just how perfectly remains contentious, however. Some researchers think decoherence and QD provide a complete account of the quantum-classical transition. But although these ideas attempt to explain why superpositions vanish at large scales and why only concrete “classical” properties remain, there’s still the question of why measurements give unique outcomes. When a particular location of a particle is selected, what happens to the other possibilities inherent in its quantum description? Were they ever in any sense real? Researchers are compelled to adopt philosophical interpretations of quantum mechanics precisely because no one can figure out a way to answer that question experimentally.

    Into the Lab

    Quantum Darwinism looks fairly persuasive on paper. But until recently that was as far as it got. In the past year, three teams of researchers have independently put the theory to the experimental test by looking for its key feature: how a quantum system imprints replicas of itself on its environment.

    The experiments depended on the ability to closely monitor what information about a quantum system gets imparted to its environment. That’s not feasible for, say, a dust grain floating among countless billions of air molecules. So two of the teams created a quantum object in a kind of “artificial environment” with only a few particles in it. Both experiments—one by Paternostro [Physical Review A] and collaborators at Sapienza University of Rome, and the other by the quantum-information expert Jian-Wei Pan [https://arxiv.org/abs/1808.07388] and co-authors at the University of Science and Technology of China—used a single photon as the quantum system, with a handful of other photons serving as the “environment” that interacts with it and broadcasts information about it.

    Both teams passed laser photons through optical devices that could combine them into multiply entangled groups. They then interrogated the environment photons to see what information they encoded about the system photon’s pointer state—in this case its polarization (the orientation of its oscillating electromagnetic fields), one of the quantum properties able to pass through the filter of quantum Darwinian selection.

    A key prediction of QD is the saturation effect: Pretty much all the information you can gather about the quantum system should be available if you monitor just a handful of surrounding particles. “Any small fraction of the interacting environment is enough to provide the maximal classical information about the observed system,” Pan said.

    The two teams found precisely this. Measurements of just one of the environment photons revealed a lot of the available information about the system photon’s polarization, and measuring an increasing fraction of the environment photons provided diminishing returns. Even a single photon can act as an environment that introduces decoherence and selection, Pan explained, if it interacts strongly enough with the lone system photon. When interactions are weaker, a larger environment must be monitored.

    Fedor Jelezko, director of the Institute for Quantum Optics at Ulm University in Germany. Ulm University

    A team led by Jelezko probed the state of a nitrogen “defect” inside a synthetic diamond (shown mounted on the right) by monitoring surrounding carbon atoms. Their findings confirmed predictions of a theory known as quantum Darwinism.
    Ulm University

    The third experimental test of QD, led by the quantum-optical physicist Fedor Jelezko at Ulm University in Germany in collaboration with Zurek and others, used a very different system and environment, consisting of a lone nitrogen atom substituting for a carbon atom in the crystal lattice of a diamond—a so-called nitrogen-vacancy defect. Because the nitrogen atom has one more electron than carbon, this excess electron cannot pair up with those on neighboring carbon atoms to form a chemical bond. As a result, the nitrogen atom’s unpaired electron acts as a lone “spin,” which is like an arrow pointing up or down or, in general, in a superposition of both possible directions.

    This spin can interact magnetically with those of the roughly 0.3 percent of carbon nuclei present in the diamond as the isotope carbon-13, which, unlike the more abundant carbon-12, also has spin. On average, each nitrogen-vacancy spin is strongly coupled to four carbon-13 spins within a distance of about 1 nanometer.

    By controlling and monitoring the spins using lasers and radio-frequency pulses, the researchers could measure how a change in the nitrogen spin is registered by changes in the nuclear spins of the environment. As they reported in a preprint last September, they too observed the characteristic redundancy predicted by QD: The state of the nitrogen spin is “recorded” as multiple copies in the surroundings, and the information about the spin saturates quickly as more of the environment is considered.

    Zurek says that because the photon experiments create copies in an artificial way that simulates an actual environment, they don’t incorporate a selection process that picks out “natural” pointer states resilient to decoherence. Rather, the researchers themselves impose the pointer states. In contrast, the diamond environment does elicit pointer states. “The diamond scheme also has problems, because of the size of the environment,” Zurek added, “but at least it is, well, natural.”

    Generalizing Quantum Darwinism

    So far, so good for quantum Darwinism. “All these studies see what is expected, at least approximately,” Zurek said.

    Riedel says we could hardly expect otherwise, though: In his view, QD is really just the careful and systematic application of standard quantum mechanics to the interaction of a quantum system with its environment. Although this is virtually impossible to do in practice for most quantum measurements, if you can sufficiently simplify a measurement, the predictions are clear, he said: “QD is most like an internal self-consistency check on quantum theory itself.”

    But although these studies seem consistent with QD, they can’t be taken as proof that it is the sole description for the emergence of classicality, or even that it’s wholly correct. For one thing, says Cabello, the three experiments offer only schematic versions of what a real environment consists of. What’s more, the experiments don’t cleanly rule out other ways to view the emergence of classicality. A theory called “spectrum broadcasting,” for example, developed by Pawel Horodecki at the Gdańsk University of Technology in Poland and collaborators, attempts to generalize QD. Spectrum broadcast theory (which has only been worked through for a few idealized cases) identifies those states of an entangled quantum system and environment that provide objective information that many observers can obtain without perturbing it. In other words, it aims to ensure not just that different observers can access replicas of the system in the environment, but that by doing so they don’t affect the other replicas. That too is a feature of genuinely “classical” measurements.

    Horodecki and other theorists have also sought to embed QD in a theoretical framework that doesn’t demand any arbitrary division of the world into a system and its environment, but just considers how classical reality can emerge from interactions between various quantum systems. Paternostro says it might be challenging to find experimental methods capable of identifying the rather subtle distinctions between the predictions of these theories.

    Still, researchers are trying, and the very attempt should refine our ability to probe the workings of the quantum realm. “The best argument for performing these experiments probably is that they are good exercise,” Riedel said. “Directly illustrating QD can require some very difficult measurements that will push the boundaries of existing laboratory techniques.” The only way we can find out what measurement really means, it seems, is by making better measurements.

    See the full article here .


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  • richardmitnick 9:14 am on July 13, 2019 Permalink | Reply
    Tags: , , Quantum entanglement, , , University of Glasgow   

    From University of Glasgow via Science Alert: “Scientists Just Unveiled The First-Ever Photo of Quantum Entanglement” 

    U Glasgow bloc

    From University of Glasgow



    Science Alert

    13 JUL 2019

    (University of Glasgow)

    In an incredible first, scientists have captured the world’s first actual photo of quantum entanglement – a phenomenon so strange Einstein famously described it as ‘spooky action at a distance’.

    The image was captured by physicists at the University of Glasgow in Scotland, and it’s so breathtaking we can’t stop staring.

    It might not look like much, but just stop and think about it for a second: this fuzzy grey image is the first time we’ve seen the particle interaction that underpins the strange science of quantum mechanics and forms the basis of quantum computing.

    Quantum entanglement occurs when two particles become inextricably linked, and whatever happens to one immediately affects the other, regardless of how far apart they are. Hence the ‘spooky action at a distance’ description.

    This particular photo shows entanglement between two photons – two particles of light. They’re interacting and for a brief moment sharing physical states.

    Paul-Antoine Moreau, first author on the paper where the image was unveiled, told the BBC the image was “an elegant demonstration of a fundamental property of nature”.

    To capture the incredible photo, Moreau and a team of physicists created a system that blasted out streams of entangled photons at what they described as ‘non-conventional objects’.

    The experiment actually involved capturing four images of the photons under four different phase transitions. You can see the full image below:

    (Moreau et al., Science Advances, 2019)

    What you’re looking at here is actually a composite of multiple images of the photons as they go through a series of four phase transitions.

    Basically, the physicists split the entangled photons up and ran one beam through a liquid crystal material known as β-Barium Borate, triggering four phase transitions.

    At the same time they captured photos of the entangled pair going through the same phase transitions, even though it hadn’t passed through the liquid crystal.

    You can see the setup below, the entangled beam of photons comes from the bottom left, one half of the entangled pair splits to the left and passes through the four phase filters. The others that go straight ahead didn’t go through the filters, but underwent the same phase changes.

    (Moreau et al., Science Advances, 2019)

    The camera was able to capture images of these at the same time, showing that they’d both shifted the same way despite being split. In other words, they were entangled.

    While Einstein made quantum entanglement famous, the late physicist John Stewart Bell helped define quantum entanglement and established a test known as ‘Bell inequality’. Basically, if you can break Bell inequality, you can confirm true quantum entanglement.

    “Here, we report an experiment demonstrating the violation of a Bell inequality within observed images,” the team write in Science Advances.

    “This result both opens the way to new quantum imaging schemes … and suggests promise for quantum information schemes based on spatial variables.”

    The research was published in Science Advances.

    See the full article here .


    Please help promote STEM in your local schools.

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    U Glasgow campus

    The University of Glasgow (Scottish Gaelic: Oilthigh Ghlaschu, Latin: Universitas Glasguensis) is the fourth oldest university in the English-speaking world and one of Scotland’s four ancient universities. It was founded in 1451. Along with the University of Edinburgh, the University was part of the Scottish Enlightenment during the 18th century. It is currently a member of Universitas 21, the international network of research universities, and the Russell Group.

    In common with universities of the pre-modern era, Glasgow originally educated students primarily from wealthy backgrounds, however it became a pioneer[citation needed] in British higher education in the 19th century by also providing for the needs of students from the growing urban and commercial middle class. Glasgow University served all of these students by preparing them for professions: the law, medicine, civil service, teaching, and the church. It also trained smaller but growing numbers for careers in science and engineering.[4]

    Originally located in the city’s High Street, since 1870 the main University campus has been located at Gilmorehill in the West End of the city.[5] Additionally, a number of university buildings are located elsewhere, such as the University Marine Biological Station Millport on the Island of Cumbrae in the Firth of Clyde and the Crichton Campus in Dumfries.

    Alumni or former staff of the University include philosopher Francis Hutcheson, engineer James Watt, philosopher and economist Adam Smith, physicist Lord Kelvin, surgeon Joseph Lister, 1st Baron Lister, seven Nobel laureates, and two British Prime Ministers.

  • richardmitnick 11:11 am on July 6, 2019 Permalink | Reply
    Tags: Quantum entanglement, ,   

    From Science Alert: “If You Thought Quantum Mechanics Was Weird, You Need to Check Out Entangled Time” 


    From Science Alert

    6 JULY 2019


    In the summer of 1935, the physicists Albert Einstein and Erwin Schrödinger engaged in a rich, multifaceted and sometimes fretful correspondence about the implications of the new theory of quantum mechanics.

    The focus of their worry was what Schrödinger later dubbed entanglement: the inability to describe two quantum systems or particles independently, after they have interacted.

    Until his death, Einstein remained convinced that entanglement showed how quantum mechanics was incomplete. Schrödinger thought that entanglement was the defining feature of the new physics, but this didn’t mean that he accepted it lightly.

    “I know of course how the hocus pocus works mathematically,” he wrote to Einstein on 13 July 1935. “But I do not like such a theory.”

    Schrödinger’s famous cat, suspended between life and death, first appeared in these letters, a byproduct of the struggle to articulate what bothered the pair.

    The problem is that entanglement violates how the world ought to work. Information can’t travel faster than the speed of light, for one.

    But in a 1935 paper, Einstein and his co-authors showed how entanglement leads to what’s now called quantum nonlocality, the eerie link that appears to exist between entangled particles.

    If two quantum systems meet and then separate, even across a distance of thousands of lightyears, it becomes impossible to measure the features of one system (such as its position, momentum and polarity) without instantly steering the other into a corresponding state.

    Up to today, most experiments have tested entanglement over spatial gaps.

    The assumption is that the ‘nonlocal’ part of quantum nonlocality refers to the entanglement of properties across space. But what if entanglement also occurs across time? Is there such a thing as temporal nonlocality?

    The answer, as it turns out, is yes.

    Just when you thought quantum mechanics couldn’t get any weirder, a team of physicists at the Hebrew University of Jerusalem reported in 2013 that they had successfully entangled photons that never coexisted.

    Previous experiments involving a technique called ‘entanglement swapping’ had already showed quantum correlations across time, by delaying the measurement of one of the coexisting entangled particles; but Eli Megidish and his collaborators were the first to show entanglement between photons whose lifespans did not overlap at all.

    Here’s how they did it.

    First, they created an entangled pair of photons, ‘1-2’ (step I in the diagram below). Soon after, they measured the polarisation of photon 1 (a property describing the direction of light’s oscillation) – thus ‘killing’ it (step II).


    Photon 2 was sent on a wild goose chase while a new entangled pair, ‘3-4’, was created (step III). Photon 3 was then measured along with the itinerant photon 2 in such a way that the entanglement relation was ‘swapped’ from the old pairs (‘1-2’ and ‘3-4’) onto the new ‘2-3’ combo (step IV).

    Some time later (step V), the polarisation of the lone survivor, photon 4, is measured, and the results are compared with those of the long-dead photon 1 (back at step II).

    The upshot? The data revealed the existence of quantum correlations between ‘temporally nonlocal’ photons 1 and 4. That is, entanglement can occur across two quantum systems that never coexisted.

    What on Earth can this mean? Prima facie, it seems as troubling as saying that the polarity of starlight in the far-distant past – say, greater than twice Earth’s lifetime – nevertheless influenced the polarity of starlight falling through your amateur telescope this winter.

    Even more bizarrely: maybe it implies that the measurements carried out by your eye upon starlight falling through your telescope this winter somehow dictated the polarity of photons more than 9 billion years old.

    Lest this scenario strike you as too outlandish, Megidish and his colleagues can’t resist speculating on possible and rather spooky interpretations of their results.

    Perhaps the measurement of photon 1’s polarisation at step II somehow steers the future polarisation of 4, or the measurement of photon 4’s polarisation at step V somehow rewrites the past polarisation state of photon 1.

    In both forward and backward directions, quantum correlations span the causal void between the death of one photon and the birth of the other.

    Just a spoonful of relativity helps the spookiness go down, though.

    In developing his theory of special relativity, Einstein deposed the concept of simultaneity from its Newtonian pedestal.

    As a consequence, simultaneity went from being an absolute property to being a relative one. There is no single timekeeper for the Universe; precisely when something is occurring depends on your precise location relative to what you are observing, known as your frame of reference.

    So the key to avoiding strange causal behaviour (steering the future or rewriting the past) in instances of temporal separation is to accept that calling events ‘simultaneous’ carries little metaphysical weight.

    It is only a frame-specific property, a choice among many alternative but equally viable ones – a matter of convention, or record-keeping.

    The lesson carries over directly to both spatial and temporal quantum nonlocality.

    Mysteries regarding entangled pairs of particles amount to disagreements about labelling, brought about by relativity.

    Einstein showed that no sequence of events can be metaphysically privileged – can be considered more real – than any other. Only by accepting this insight can one make headway on such quantum puzzles.

    The various frames of reference in the Hebrew University experiment (the lab’s frame, photon 1’s frame, photon 4’s frame, and so on) have their own ‘historians’, so to speak.

    While these historians will disagree about how things went down, not one of them can claim a corner on truth. A different sequence of events unfolds within each one, according to that spatiotemporal point of view.

    Clearly, then, any attempt at assigning frame-specific properties generally, or tying general properties to one particular frame, will cause disputes among the historians.

    But here’s the thing: while there might be legitimate disagreement about which properties should be assigned to which particles and when, there shouldn’t be disagreement about the very existence of these properties, particles, and events.

    These findings drive yet another wedge between our beloved classical intuitions and the empirical realities of quantum mechanics.

    As was true for Schrödinger and his contemporaries, scientific progress is going to involve investigating the limitations of certain metaphysical views.

    Schrödinger’s cat, half-alive and half-dead, was created to illustrate how the entanglement of systems leads to macroscopic phenomena that defy our usual understanding of the relations between objects and their properties: an organism such as a cat is either dead or alive. No middle ground there.

    Most contemporary philosophical accounts of the relationship between objects and their properties embrace entanglement solely from the perspective of spatial nonlocality.

    But there’s still significant work to be done on incorporating temporal nonlocality – not only in object-property discussions, but also in debates over material composition (such as the relation between a lump of clay and the statue it forms), and part-whole relations (such as how a hand relates to a limb, or a limb to a person).

    For example, the ‘puzzle’ of how parts fit with an overall whole presumes clear-cut spatial boundaries among underlying components, yet spatial nonlocality cautions against this view. Temporal nonlocality further complicates this picture: how does one describe an entity whose constituent parts are not even coexistent?

    Discerning the nature of entanglement might at times be an uncomfortable project. It’s not clear what substantive metaphysics might emerge from scrutiny of fascinating new research by the likes of Megidish and other physicists.

    In a letter to Einstein, Schrödinger notes wryly (and deploying an odd metaphor): “One has the feeling that it is precisely the most important statements of the new theory that can really be squeezed into these Spanish boots – but only with difficulty.”

    We cannot afford to ignore spatial or temporal nonlocality in future metaphysics: whether or not the boots fit, we’ll have to wear ’em.

    See the full article here .


    Please help promote STEM in your local schools.

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  • richardmitnick 8:41 am on June 5, 2019 Permalink | Reply
    Tags: "Stanford joins collaboration to explore 'ultra-quantum matter'", , Quantum entanglement, , , The Simons Collaboration on Ultra-Quantum Matter   

    From Stanford University: “Stanford joins collaboration to explore ‘ultra-quantum matter'” 

    Stanford University Name
    From Stanford University

    June 3, 2019
    Ker Than


    The Simons Collaboration on Ultra-Quantum Matter brings together physicists from 12 institutions to “understand, classify and realize” new forms of ultra-quantum matter in the lab.

    Stanford physicist Shamit Kachru is a member of a new collaboration that aims to unravel the mystery of entangled quantum matter — macroscopic assemblages of atoms and electrons that seem to share the same seemingly telepathic link as entangled subatomic particles.

    The Simons Collaboration on Ultra-Quantum Matter is funded by the Simons Foundation and led by Harvard physics Professor Ashvin Vishwanath. It is part of the Simons Collaborations in Mathematics and Physical Sciences program, which aims to “stimulate progress on fundamental scientific questions of major importance in mathematics, theoretical physics and theoretical computer science.” The Simons Collaboration on Ultra-Quantum Matter will be one of 12 such collaborations ranging across these fields.

    Ultra-quantum matter, or UQM, exhibit non-intuitive quantum properties that were once thought to arise only in very small systems. One key property is “non-local entanglement,” in which two physically separated groups of atoms can share joint properties, so that measuring one affects the measurement outcome of the other. UQM should exhibit entirely new physical properties, a better understanding of which could lead to new types of quantum information storage systems and quantum materials.

    The Simons Collaboration on Ultra-Quantum Matter brings together physicists from 12 institutions to “understand, classify and realize” new forms of ultra-quantum matter in the lab. To achieve this, the collaboration includes physicists working in different domains, including condensed matter and high energy theorists, as well as atomic and quantum information experts. Kachru’s own background is in string theory, theoretical cosmology, and condensed matter physics.

    A confluence of factors makes this a particularly exciting time to study UQM, said Kachru, who is the Wells Family Director of the Stanford Institute for Theoretical Physics (SITP) and the chair of the physics department.

    “Many of the cutting-edge questions in quantum field theory now seem to involve highly quantum condensed matter systems,” Kachru said. “These systems are often best studied using elegant and clean mathematical techniques, and there is a promise of genuine contact between high level theory and experiment. I can’t imagine better people to teach me about issues and opportunities here than the collaboration members, who are leading experts in all aspects of UQM.”

    Kachru also looks forward to working again with former Stanford graduate student and collaboration member, John McGreevy, who was Kachru’s first PhD advisee and is now a professor of physics at the University of California, San Diego.

    Ultra-Quantum Matter is an $8M four-year award funded by the Simons Foundation and renewable for three additional years. It will support researchers from the following institutions: Caltech, Harvard, the Institute for Advanced Study, MIT, Stanford, University of California Santa Barbara, University of California San Diego, the University of Chicago, the University of Colorado Boulder, the University of Innsbruck, University of Maryland and University of Washington.

    A UQM meeting of the new collaboration is scheduled to take place at Stanford in May of 2020.

    See the full article here .

    Please help promote STEM in your local schools.

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    Stanford University campus. No image credit

    Stanford University

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

    Stanford University Seal

  • richardmitnick 11:42 am on May 17, 2019 Permalink | Reply
    Tags: Articles about them inevitably refer to entanglement- a property of quantum physics that makes all these magical devices possible., , , Quantum computers; quantum cryptography; and quantum (insert name here) are often in the news these days., Quantum entanglement,   

    From University of Toronto: “Remote connections? U of T expert on detangling entanglement in quantum physics” 

    U Toronto Bloc

    From University of Toronto

    April 26, 2019
    Amar Vutha

    Entanglement is a “quantum correlation” between the properties of particles (image by Shutterstock)

    Quantum computers, quantum cryptography and quantum (insert name here) are often in the news these days. Articles about them inevitably refer to entanglement, a property of quantum physics that makes all these magical devices possible.

    Einstein called entanglement “spooky action at a distance,” a name that has stuck and become increasingly popular. Beyond just building better quantum computers, understanding and harnessing entanglement is also useful in other ways.

    For example, it can be used to make more accurate measurements of gravitational waves, and to better understand the properties of exotic materials. It also subtly shows up in other places: I have been studying how atoms bumping into each other become entangled, to understand how this affects the accuracy of atomic clocks.

    But what is entanglement? Is there some way to understand this “spooky” phenomenon? I will try to explain it by bringing together two notions from physics: conservation laws and quantum superpositions.

    Conservation laws

    Conservation laws are some of the deepest and most pervasive concepts in all of physics. The law of conservation of energy states that the total amount of energy in an isolated system remains fixed (although it can be converted from electrical energy to mechanical energy to heat, and so on). This law underlies the workings of all of our machines, whether they are steam engines or electric cars. Conservation laws are a kind of accounting statement: You can exchange bits of energy around, but the total amount has to stay the same.

    Conservation of momentum (momentum being mass times velocity) is the reason why, when two ice skaters with different masses push off from each other, the lighter one moves away faster than the heavier. This law also underlies the famous dictum that “every action has an equal and opposite reaction.” Conservation of angular momentum is why – going back to ice skaters again – a whirling figure skater can spin faster by drawing her arms closer to her body.

    France’s Gabriella Papadakis and Guillaume Cizeron demonstrate the effects of conservation laws during the 2019 ISU European Figure Skating Championships in Belarus (photo by Shutterstock)

    These conservation laws have been experimentally verified to work across an extraordinary range of scales in the universe, from black holes in distant galaxies all the way down to the tiniest spinning electrons.

    Quantum addition

    Picture yourself on a nice hike through the woods. You come to a fork in the trail, but you find yourself struggling to decide whether to go left or right. The path to the left looks dark and gloomy but is reputed to lead to some nice views, while the one to the right looks sunny but steep. You finally decide to go right, wistfully wondering about the road not taken. In a quantum world, you could have chosen both.

    For systems described by quantum mechanics (that is, things that are sufficiently well isolated from heat and external disturbances), the rules are more interesting. Like a spinning top, an electron for example can be in a state where it spins clockwise, or in another state where it spins anticlockwise. Unlike a spinning top though, it can also be in a state that is [clockwise spinning] + [anticlockwise spinning].

    The states of quantum systems can be added together and subtracted from each other. Mathematically, the rules for combining quantum states can be described in the same way as the rules for adding and subtracting vectors. The word for such a combination of quantum states is a superposition. This is really what is behind strange quantum effects that you may have heard about, such as the double-slit experiment, or particle-wave duality.

    PBS Studios: The Double-Slit Experiment. 13 minutes

    Say you decide to force an electron in the [clockwise spinning] + [anticlockwise spinning] superposition state to yield a definite answer. Then the electron randomly ends up either in the [clockwise spinning] state or in the [anticlockwise spinning] state. The odds of one outcome versus the other are easy to calculate (with a good physics book at hand). The intrinsic randomness of this process may bother you if your worldview requires the universe to behave in a completely predictable way, but … c’est la (experimentally tested) vie.

    Conservation laws and quantum mechanics

    Let’s put these two ideas together now, and apply the law of conservation of energy to a pair of quantum particles.

    Imagine a pair of quantum particles (say atoms) that start off with a total of 100 units of energy. You and your friend separate the pair, taking one each. You find that yours has 40 units of energy. Using the law of conservation of energy, you deduce that the one your friend has must have 60 units of energy. As soon as you know the energy of your atom, you immediately also know the energy of your friend’s atom. You would know this even if your friend never revealed any information to you. And you would know this even if your friend was off on the other side of the galaxy at the time you measured the energy of your atom. Nothing spooky about it (once you realize this is just correlation, not causation).

    But the quantum states of a pair of atoms can be more interesting. The energy of the pair can be partitioned in many possible ways (consistent with energy conservation, of course). The combined state of the pair of atoms can be in a superposition, for example: [your atom: 60 units; friend’s atom: 40 units] + [your atom: 70 units; friend’s atom: 30 units].

    This is an entangled state of the two atoms. Neither your atom, nor your friend’s, has a definite energy in this superposition. Nevertheless, the properties of the two atoms are correlated because of conservation of energy: Their energies always add up to 100 units.

    For example, if you measure your atom and find it in a state with 70 units of energy, you can be certain that your friend’s atom has 30 units of energy. You would know this even if your friend never revealed any information to you. And thanks to energy conservation, you would know this even if your friend was off on the other side of the galaxy.

    Nothing spooky about it.The Conversation

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Founded in 1827, the University of Toronto has evolved into Canada’s leading institution of learning, discovery and knowledge creation. We are proud to be one of the world’s top research-intensive universities, driven to invent and innovate.

    Our students have the opportunity to learn from and work with preeminent thought leaders through our multidisciplinary network of teaching and research faculty, alumni and partners.

    The ideas, innovations and actions of more than 560,000 graduates continue to have a positive impact on the world.

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