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  • richardmitnick 9:54 am on December 18, 2014 Permalink | Reply
    Tags: , , Quantum Physics,   

    From Ethan Siegel: “Quantum Immortality” 

    Starts with a bang
    Starts with a Bang

    This article was written by Paul Halpern, the author of Einstein’s Dice and Schrödinger’s Cat: How Two Great Minds Battled Quantum Randomness to Create a Unified Theory of Physics.

    Observers are the necessary, but unliked, bouncers in the elegant nightclub of quantum physics. While, no one is entirely comfortable with having doormen checking IDs, they persist; otherwise everyone and everything gets in, contrary to ordinary experience.

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    Image credit: AIP Emilio Segre Visual Archives, Physics Today Collection of [Paul]Dirac and [Werner] Heisenberg;

    v
    © Los Alamos National Laboratory of [John] von Neumann.

    In the late 1920s and early 1930s, Heisenberg, Dirac, and John von Neumann, codified the formalism of quantum mechanics as a two-step process. One part involves the continous evolution of states via the deterministic

    e
    Schrödinger equation.
    Image credit: Wikimedia Commons user YassineMrabet.

    Map out a system’s potential energy distribution — in the form of a well, for example — and the spectrum of possible quantum states is set. If the states are time-dependent, then they predictably transform. That could set out, for instance, a superposition of states that spreads out in position space over time, like an expanding puddle of water.

    Yet experiments show that if an apparatus is designed to measure a particular quantity, such as the position, momentum or spin-state of a particle, quantum measurements yield specific values of that respective physical parameter. Such specificity requires a second type of quantum operation that is instantaneous and discrete, rather than gradual and continuous: the process of collapse.

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    Image credit: A Friedman, via http://blogs.scientificamerican.com/the-curious-wavefunction/2014/01/15/what-scientific-idea-is-ready-for-retirement/.

    Collapse occurs when a measurement of a certain physical parameter — position, let’s say — precipitates a sudden transformation into one of the “eigenstates” (solution states) of the operator (mathematical function) corresponding to that parameter — the position operator, in that case.

    g
    Image credit: Nick Trefethen, via http://www.chebfun.org/examples/ode-eig/Eigenstates.html.

    Then the measured value of that quantity is the “eigenvalue” associated with that eigenstate — the specific position of the particle, for instance. Eigenstates represent the spectrum of possible states and eigenvalues the measurements associated with those states.

    We can imagine the situation of quantum collapse as being something like a slot machine with a mixture of dollar coins and quarters; some old enough to be valuable, others shining new.

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    Image credit: © 2014 Marco Jewelers, via http://marcojewelers.net/sell-buy-silver-gold-coins.

    Its front panel has two buttons: one red and the other blue. Press the red button and the coins instantly become sorted according to denomination. A number of dollar coins drop out (a mixture of old and new). Press the blue button and the sorting is instantly done by date. A bunch of old coins (of both denominations) are released. While someone seeking quick bucks might press red, a coin collector might push blue. The machine is set that you are not permitted to press both buttons. Similarly, in quantum physics, according to Heisenberg’s famous uncertainty principle certain quantities such as position and momentum are not measurable at once with any degree of precision.

    Over the years, a number of critics have attacked this interpretation.

    a
    Albert Einstein
    Image credit: Oren Jack Turner, Princeton, N.J., via Wikimedia Commons user Jaakobou.

    Suggesting that quantum physics, though experimentally correct, must be incomplete, Einstein argued that random, instantaneous transitions had no place in a fundamental description of nature. Schrödinger cleverly developed his well-known feline thought experiment to demonstrate the absurdity of the observer’s role in quantum collapse. In his hypothetical scheme, he imagined a set-up in which a cat in a closed box, whose survival (or not) was tied to the random decay of a radioactive material, was in a mixed state of life and death until the box was opened and the system observed.

    Image credit: retrieved from Øystein Elgarøy at http://fritanke.no/index.php?page=vis_nyhet&NyhetID=8513.

    More recently, physicist Bryce DeWitt, who theorized how quantum mechanics might apply to gravity and the dynamics of the universe itself, argued that because there are presumably no observers outside the cosmos to view it (and trigger collapse into quantum gravity eigenstates), a complete accounting of quantum physics could not include observers.

    Instead, DeWitt, until his death in 2004, was an ardent advocate of an alternative to the Copenhagen (standard) interpretation of quantum mechanics that he dubbed the Many Worlds Interpretation (MWI).

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    Image credit: University of Texas of Bryce DeWitt;

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    Professor Jeffrey A. Barrett and UC Irvine, of Hugh Everett III.

    He based his views on the seminal work of Hugh Everett, who as a graduate student at Princeton, developed a way of avoiding the need in quantum mechanics for an observer. Instead, each time a quantum measurement is taken, the universe, including any observers, seamlessly and simultaneously splits into the spectrum of possible values for that measurement. For example, in the case of the measurement of the spin of an electron, in one branch it has spin up, and all observers see it that way; in the other it has spin down. Schrödinger’s cat would be happily alive in one reality, to the joy of its owner, while cruelly deceased in the other, much to the horror of the same owner (but in a different branch). Each observer in each branch would have no conscious awareness of his near-doppelgangers.

    As Everett wrote to DeWitt in explaining his theory:

    “The theory is in full accord with our experience (at least insofar as ordinary quantum mechanics is)… because it is possible to show that no observer would ever be aware of any ‘branching.’”

    If Schrödinger’s thought experiment were repeated each day, there would always be one branch of the universe in which the cat survives. Hypothetically, rather than the proverbial “nine lives,” the cat could have an indefinite number of “lives” or at least chances at life. There would always be one copy of the experimenter who is gratified, but perplexed, that his cat has beaten the odds and lived to see another day. The other copy, in mourning, would lament that the cat’s luck had finally run out.

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    Image credit: Ethan Zuckerman, from Garrett Lisi’s talk (2008), via http://www.ethanzuckerman.com/blog/2008/02/28/ted2008-garrett-lisi-looks-for-balance/.

    What about human survival? We are each a collection of particles, governed on the deepest level by quantum rules. If each time a quantum transition took place, our bodies and consciousness split, there would be copies that experienced each possible result, including those that might determine our life or death. Suppose in one case a particular set of quantum transitions resulted in faulty cell division and ultimately a fatal form of cancer. For each of the transitions, there would always be an alternative that did not lead to cancer. Therefore, there would always be branches with survivors. Add in the assumption that our conscious awareness would flow only to the living copies, and we could survive any number of potentially hazardous events related to quantum transitions.

    Everett reportedly believed in this kind of “quantum immortality.” Fourteen years after his death in 1982, his daughter Liz took her own life, explaining in her suicide note that in some branch of the universe, she hoped to reunite with her father.

    There are major issues with the prospects for quantum immortality however. For one thing the MWI is still a minority hypothesis. Even if it is true, how do we know that our stream of conscious thought would flow only to branches in which we survive? Are all possible modes of death escapable by an alternative array of quantum transitions? Remember that quantum events must obey conservation laws, so there could be situations in which there was no way out that follows natural rules. For example, if you fall out of a spaceship hatch into frigid space, there might be no permissible quantum events (according to energy conservation) that could lead you to stay warm enough to survive.

    Finally, suppose you do somehow manage to achieve quantum immortality — with your conscious existence following each auspicious branch. You would eventually outlive all your friends and family members — because in your web of branches you would eventually encounter copies of them that didn’t survive. Quantum immortality would be lonely indeed!

    See the full article here.

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    Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible.

     
  • richardmitnick 8:35 pm on November 1, 2014 Permalink | Reply
    Tags: , , , , , , Quantum Physics   

    From AAAS: “Dark matter: Out with the WIMPs, in with the SIMPs?” 

    AAAS

    AAAS

    30 October 2014
    Adrian Cho

    Like cops tracking the wrong person, physicists seeking to identify dark matter—the mysterious stuff whose gravity appears to bind the galaxies—may have been stalking the wrong particle. In fact, a particle with some properties opposite to those of physicists’ current favorite dark matter candidate—the weakly interacting massive particle, or WIMP—would do just as good a job at explaining the stuff, a quartet of theorists says. Hypothetical strongly interacting massive particles—or SIMPs—would also better account for some astrophysical observations, they argue.

    “We’ve been searching for WIMPs for quite some time, but we haven’t found them yet, so I think it’s important to think outside the box,” says Yonit Hochberg, a theorist at Lawrence Berkeley National Laboratory and the University of California (UC), Berkeley, and an author of the new paper.

    Theorists dreamed up WIMPs 30 years ago to help explain why galaxies don’t just fly apart. The particles would have a mass between one and 1000 times that of a proton and, in addition to gravity, would interact with one another and with ordinary matter through only the weak nuclear force, one of two forces of nature that normally exert themselves only in the atomic nucleus.

    The infant universe would have produced a huge number of WIMPs as subatomic particles crashed into one another. Some of those WIMPs would then disappear when two of them collided and annihilated each other to produce two ordinary particles. As the universe expanded, such collisions would become ever rarer and, given the strength of the weak force, just enough WIMPs would survive to provide the right amount of dark matter today—about five times that of ordinary matter. That coincidence, or “WIMP miracle,” has made WIMPs a favorite of theorists, even if experimenters have yet to spot them floating about.

    However, Hochberg and colleagues argue that dark matter could also consist of lighter particles that have a mass somewhere around one-tenth that of the proton and interact with one another—but not ordinary matter—very strongly. Such SIMPs would pull on one another almost as strongly as the quarks in a proton, which cling to each other so fiercely that it’s impossible to isolate a quark.

    SIMPs can also provide just the right amount of dark matter, assuming the theorists add a couple of wrinkles. The SIMPs must disappear primarily through collisions in which three SIMPs go in and only two SIMPs come out. These events must be more common than ones in which two SIMPs annihilate each other to produce two ordinary particles. Moreover, the theorists argue, SIMPs must interact with ordinary matter, although much more weakly than WIMPs. That’s because the three-to-two collisions would heat up the SIMPs if they could not interact and share heat with ordinary matter.

    That may seem like a lot to ask, but those conditions are easy to meet so long as the SIMPs aren’t too heavy, Hochberg says. So the WIMP miracle could easily be replaced with a SIMP miracle, as the team reports this month in Physical Review Letters.

    Moreover, the fact that SIMPs must interact with ordinary matter guarantees that, in principle, they should be detectable in some way, Hochberg says. Whereas physicists are now searching for signs of WIMPs colliding with massive atomic nuclei, researchers would probably have to look for SIMPs smacking into lighter electrons because the bantamweight particles would not pack enough punch to send a nucleus flying.

    Compared with WIMPy dark matter, SIMPy dark matter would also have another desirable property. As the universe evolved, dark matter coalesced into clumps, or halos, in which the galaxies then formed. But computer simulations suggest that dark matter that doesn’t interact with itself would form myriad little clumps that are very dense in the center. And little “dwarf galaxies” aren’t as abundant and the centers of galaxies aren’t as dense as the simulations suggest. But strongly interacting dark matter would smooth out the distribution of dark matter and solve those problems, Hochberg says. “This isn’t some independent thing that we’ve just forced into the model,” she says. “It just naturally happens.”

    The new analysis “has the flavor of the WIMP miracle, which is nice,” says Jonathan Feng, a theorist at UC Irvine who was not involved in the work. Feng says he’s been working on similar ideas and that the ability to reconcile the differences between dark matter simulations and the observed properties of galaxies makes strongly interacting dark matter attractive conceptually.

    However, he cautions, it may be possible that, feeble as they may be, the interactions between dark and ordinary matter might smooth out the dark matter distribution on their own. And Feng says he has some doubts about the claim that SIMPs must interact with ordinary matter strongly enough to be detected. So the SIMP probably won’t knock WIMP off its perch as the best guess for the dark matter particle just yet, Feng says: “At the moment, it’s not as well motivated as the WIMP, but it’s definitely worth exploring.”

    See the full article here.

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  • richardmitnick 3:12 pm on October 17, 2014 Permalink | Reply
    Tags: , , , , Quantum Physics   

    From Perimeter: “The Last Gasp of a Black Hole” 

    Perimeter Institute
    Perimeter Institute

    October 17, 2014
    No Writer Credit

    New research from Perimeter shows that two of the strangest features of quantum mechanicsentanglement and negative energy – might be two faces of one coin.

    Quantum mechanics is, notoriously, weird. Take entanglement: when two or more particles are entangled, their states are linked together, no matter how far apart they go.

    If the idea makes your classical mind twitch, you’re in good company. At the heart of everything, according to quantum mechanics, nature has a certain amount of irreducible jitter. Even nothing – the vacuum of space – can jitter, or as physicists say, fluctuate. When it does, a particle and its anti-particle can pop into existence.

    For example, an electron and an anti-electron (these are called positrons) might pop into existence out of the vacuum. We know that they each have a spin of one half, which might be either up or down. We also know that these particles were created from nothing and so, to balance the books, the total spin must add up to zero. Finally, we know that the spin of either particle is not determined until it is measured.

    So suppose the electron and the positron fly apart a few metres or a few light years, and then a physicist comes by to measure the spin of, say, the electron. She discovers that the electron is spin up, and in that moment, the electron becomes spin up. Meanwhile, a few metres or a few light years away, the positron becomes spin down. Instantly. That is the strangeness of quantum entanglement.

    Negative energy is less well known than entanglement, but no less weird. It begins with the idea – perhaps already implied by the positron and electron popping out of nowhere – that empty space is not empty. It is filled with quantum fields, and the energy of those fields can fluctuate a little bit.

    In fact, the energy of these fields can dip under the zero mark, albeit briefly. When that happens, a small region of space can, for a short span of time, weigh less than nothing – or at least less than the vacuum. It’s a little bit like finding dry land below sea level.

    Despite their air of strangeness, entanglement and negative energy are both well-explored topics. But now, new research, published as a Rapid Communication in Physical Review D, is hinting that these two strange phenomena may be linked in a surprising way.

    The work was done by Perimeter postdoctoral fellow Matteo Smerlak and former postdoc Eugenio Bianchi (now on the faculty at Penn State and a Visiting Fellow at Perimeter). “Negative energy and entanglement are two of the most striking features of quantum mechanics,” says Smerlak. “Now, we think they might be two sides of the same coin.”

    ms
    Perimeter Postdoctoral Researcher Matteo Smerlak

    man
    Perimeter Visiting Fellow Eugenio Bianchi

    Specifically, the researchers proved mathematically that any external influence that changes the entanglement of a system in its vacuum state must also produce some amount of negative energy. The reverse, they say, is also true: negative energy densities can never be produced without entanglement being directly affected.

    At the moment, the result only applies to certain quantum fields in two dimensions – to light pulses travelling up and down a thin cable, for instance. And it is with light that the Perimeter researchers hope that their new idea can be directly tested.

    “Some quantum states which have negative energy are known, and one of them is called a ‘squeezed state,’ and they can be produced in the lab, by optical devices called squeezers,” says Smerlak. The squeezers manipulate light to produce an observable pattern of negative energy.

    Remember that Smerlak and Bianchi’s basic argument is that if an external influence affects vacuum entanglement, it will also release some negative energy. In a quantum optics setup, the squeezers are the external influence.

    Experimentalists should be able to look for the correlation between the entanglement patterns and the negative energy densities which this new research predicts. If these results hold up – always a big if in brand new work – and if they can make the difficult leap from two dimensions to the real world, then there will be startling implications for black holes.

    Like optical squeezers, black holes also produce changes in entanglement and energy density. They do this by separating entangled pairs of particles and preferentially selecting the ones with negative energy.

    Remember that the vacuum is full of pairs of particles and antiparticles blinking into existence. Under normal circumstances, they blink out again just as quickly, as the particle and the antiparticle annihilate each other. But just at a black hole’s event horizon, it sometimes happens that one of the particles is sucked in, while the other escapes. The small stream of escaping particles is known as Hawking radiation.

    By emitting such radiation, black holes slowly give up their energy and mass, and eventually disappear. Black hole evaporation, as the process is known, is a hot topic in physics. This new research has the potential to change the way we think about it.

    “In the late stages of the evaporation of a black hole, the energy released from the black hole will turn negative,” says Smerlak. And if a black hole releases negative energy, then its total energy goes up, not down. “It means that the black hole will shrink and shrink and shrink – for zillions of years – but in the end, it will release its negative energy in a gasp before dying. Its mass will briefly go up.”

    Call it the last gasp of a black hole.

    See the full article here.

    About Perimeter

    Perimeter Institute is a leading centre for scientific research, training and educational outreach in foundational theoretical physics. Founded in 1999 in Waterloo, Ontario, Canada, its mission is to advance our understanding of the universe at the most fundamental level, stimulating the breakthroughs that could transform our future. Perimeter also trains the next generation of physicists through innovative programs, and shares the excitement and wonder of science with students, teachers and the general public.

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  • richardmitnick 11:15 am on October 15, 2014 Permalink | Reply
    Tags: , , Loop Quantum Gravity, , Quantum Gravity, , Quantum Physics, White Holes   

    From NOVA: “Are White Holes Real?” 

    PBS NOVA

    NOVA

    Tue, 19 Aug 2014
    Maggie McKee

    Sailors have their krakens and their sea serpents. Physicists have white holes: cosmic creatures that straddle the line between tall tale and reality. Yet to be seen in the wild, white holes may be only mathematical monsters. But new research suggests that, if a speculative theory called loop quantum gravity is right, white holes could be real—and we might have already observed them.

    wh

    A white whole is, roughly speaking, the opposite of a black hole. “A black hole is a place where you can go in but you can never escape; a white hole is a place where you can leave but you can never go back,” says Caltech physicist Sean Carroll. “Otherwise, [both share] exactly the same mathematics, exactly the same geometry.” That boils down to a few essential features: a singularity, where mass is squeezed into a point of infinite density, and an event horizon, the invisible “point of no return” first described mathematically by the German physicist Karl Schwarzschild in 1916. For a black hole, the event horizon represents a one-way entrance; for a white hole, it’s exit-only.

    There is excellent evidence that black holes really exist, and astrophysicists have a robust understanding of what it takes to make one. To imagine how a white hole might form, though, we have to go out on a bit of an astronomical limb. One possibility involves a spinning black hole. According to [Albert] Einstein’s general theory of relativity, the rotation smears the singularity into a ring, making it possible in theory to travel through the swirling black hole without being crushed. General relativity’s equations suggest that someone falling into such a black hole could fall through a tunnel in space-time called a wormhole and emerge from a white hole that spits its contents into a different region of space or period of time.

    Though mathematical solutions to those equations exist for white holes, “they’re not realistic,” says Andrew Hamilton, an astrophysicist at the University of Colorado at Boulder. That is because they describe universes that contain only black holes, white holes and wormholes—no matter, radiation or energy. Indeed, previous research, including Hamilton’s, suggests that anything that falls into a spinning black hole will essentially plug up the wormhole, preventing the formation of a passage to a white hole.

    But there’s a light at the end of the wormhole, so to speak. General relativity, from which Hamilton draws his predictions, breaks down at a black hole’s singularity. “The energy density and the curvature become so large that classical gravity is not a good description of what’s happening there,” says Stephen Hsu, a physicist at Michigan State University in East Lansing. Perhaps a more complete model of gravity—one that works as well on the quantum scale as it does on large ones—would negate the instability and allow for white holes, he says.

    Indeed, a unified theory that merges gravity and quantum mechanics is one of the holy grails of contemporary physics. Applying one such theory, loop quantum gravity, to black holes, theorists Hal Haggard and Carlo Rovelli of Aix-Marseille University in France have shown that black holes could metamorphose into white holes via a quantum process. In July, they published their work online.

    Loop quantum gravity proposes that space-time is made up of fundamental building blocks shaped like loops. According to Haggard and Rovelli, the loops’ finite size prevents a dying star from collapsing all the way down into a point of infinite density, and the shrinking object rebounds into a white hole instead. This process may take just a few thousandths of a second, but thanks to the intense gravity involved, the effects of relativity make the transformation appear to take much, much longer to anyone watching from afar. That means that minuscule black holes born in the infant universe could “now be ready to pop off like firecrackers,” forming white holes, according to a report in Nature. Some of the explosions astronomers thought were supernovae may actually be the wails of newborn white holes.

    The black-to-white conversion could resolve a nettlesome conundrum known as the black hole information paradox. The notion that information can be destroyed is anathema in physics, and general relativity says that anything, including information, that falls into a black hole can never escape. These two statements are not at odds if black holes simply act as locked safes for any information they slurp up, but Stephen Hawking showed 40 years ago that black holes actually evaporate over time. That led to the disturbing possibility that the information contained within them could be lost too, triggering a debate that rages to this day.

    But if a black hole instead turns into a white hole, then “all the information is recovered,” says Haggard. “We are quite excited about this mechanism because it avoids so many of the thorny issues that surround this discussion.”

    The new work is preliminary, however, and it is far from clear whether loop quantum gravity is an accurate description of reality. The only glimpse we get of white holes might turn out to be those we model in labs and kitchen sinks. But Carroll says that’s okay. Just thinking about these possibly mythical cosmic creatures can improve physicists’ intuition, “even if the real world is messy and not like those exact situations,” he says. “That’s the way in which white holes are very useful.”

    See the full article here.

    NOVA is the highest rated science series on television and the most watched documentary series on public television. It is also one of television’s most acclaimed series, having won every major television award, most of them many times over.

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  • richardmitnick 4:41 pm on September 20, 2014 Permalink | Reply
    Tags: , , , , , Quantum Physics   

    From Princeton: “‘Solid’ light could compute previously unsolvable problems” 

    Princeton University
    Princeton University

    Sep 08, 2014
    John Sullivan

    Researchers at Princeton University have begun crystallizing light as part of an effort to answer fundamental questions about the physics of matter.

    The researchers are not shining light through crystal – they are transforming light into crystal. As part of an effort to develop exotic materials such as room-temperature superconductors, the researchers have locked together photons, the basic element of light, so that they become fixed in place.

    “It’s something that we have never seen before,” said Andrew Houck, an associate professor of electrical engineering and one of the researchers. “This is a new behavior for light.”

    The results raise intriguing possibilities for a variety of future materials. But the researchers also intend to use the method to address questions about the fundamental study of matter, a field called condensed matter physics.

    “We are interested in exploring – and ultimately controlling and directing – the flow of energy at the atomic level,” said Hakan Türeci, an assistant professor of electrical engineering and a member of the research team. “The goal is to better understand current materials and processes and to evaluate materials that we cannot yet create.”

    The team’s findings, reported online on Sept. 8 in the journal Physical Review X, are part of an effort to answer fundamental questions about atomic behavior by creating a device that can simulate the behavior of subatomic particles. Such a tool could be an invaluable method for answering questions about atoms and molecules that are not answerable even with today’s most advanced computers.

    light

    In part, that is because current computers operate under the rules of classical mechanics, which is a system that describes the everyday world containing things like bowling balls and planets. But the world of atoms and photons obeys the rules of quantum mechanics, which include a number of strange and very counterintuitive features. One of these odd properties is called “entanglement” in which multiple particles become linked and can affect each other over long distances.

    The difference between the quantum and classical rules limits a standard computer’s ability to efficiently study quantum systems. Because the computer operates under classical rules, it simply cannot grapple with many of the features of the quantum world. Scientists have long believed that a computer based on the rules of quantum mechanics could allow them to crack problems that are currently unsolvable. Such a computer could answer the questions about materials that the Princeton team is pursuing, but building a general-purpose quantum computer has proven to be incredibly difficult and requires further research.

    Another approach, which the Princeton team is taking, is to build a system that directly simulates the desired quantum behavior. Although each machine is limited to a single task, it would allow researchers to answer important questions without having to solve some of the more difficult problems involved in creating a general-purpose quantum computer. In a way, it is like answering questions about airplane design by studying a model airplane in a wind tunnel – solving problems with a physical simulation rather than a digital computer.

    In addition to answering questions about currently existing material, the device also could allow physicists to explore fundamental questions about the behavior of matter by mimicking materials that only exist in physicists’ imaginations.

    To build their machine, the researchers created a structure made of superconducting materials that contains 100 billion atoms engineered to act as a single “artificial atom.” They placed the artificial atom close to a superconducting wire containing photons.

    By the rules of quantum mechanics, the photons on the wire inherit some of the properties of the artificial atom – in a sense linking them. Normally photons do not interact with each other, but in this system the researchers are able to create new behavior in which the photons begin to interact in some ways like particles.

    “We have used this blending together of the photons and the atom to artificially devise strong interactions among the photons,” said Darius Sadri, a postdoctoral researcher and one of the authors. “These interactions then lead to completely new collective behavior for light – akin to the phases of matter, like liquids and crystals, studied in condensed matter physics.”

    Türeci said that scientists have explored the nature of light for centuries; discovering that sometimes light behaves like a wave and other times like a particle. In the lab at Princeton, the researchers have engineered a new behavior.

    “Here we set up a situation where light effectively behaves like a particle in the sense that two photons can interact very strongly,” Türeci said. “In one mode of operation, light sloshes back and forth like a liquid; in the other, it freezes.”

    The current device is relatively small, with only two sites where an artificial atom is paired with a superconducting wire. But the researchers say that by expanding the device and the number of interactions, they can increase their ability to simulate more complex systems – growing from the simulation of a single molecule to that of an entire material. In the future, the team plans to build devices with hundreds of sites with which they hope to observe exotic phases of light such as superfluids and insulators.

    “There is a lot of new physics that can be done even with these small systems,” said James Raftery, a graduate student in electrical engineering and one of the authors. “But as we scale up, we will be able to tackle some really interesting questions.”

    Besides Houck, Türeci, Sadri and Raftery, the research team included Sebastian Schmidt, a senior researcher at the Institute for Theoretical Physics at ETH Zurich, Switzerland. Support for the project was provided by: the Eric and Wendy Schmidt Transformative Technology Fund; the National Science Foundation; the David and Lucile Packard Foundation; the U.S. Army Research Office; and the Swiss National Science Foundation.

    See the full article here.

    About Princeton: Overview

    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

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  • richardmitnick 4:25 pm on September 20, 2014 Permalink | Reply
    Tags: , , , Quantum Physics   

    From phys.org: “UCI team is first to capture motion of single molecule in real time” 

    physdotorg
    phys.org

    September 16, 2014
    No Writer Credit

    UC Irvine chemists have scored a scientific first: capturing moving images of a single molecule as it vibrates, or “breathes,” and shifts from one quantum state to another.

    aa

    The groundbreaking achievement, led by Ara Apkarian, professor of chemistry, and Eric Potma, associate professor of chemistry, opens a window into the strange realm of quantum mechanics – where nanoscopic bits of matter seemingly defy the logic of classical physics.

    phy
    A simplified view on fields of modern physics theories. Please note that from historical point of view, this diagram is very simplified. In fact, when quantum mechanics was originally formulated, it was applied to models whose correspondence limit was non-relativistic. Many attempts were made to merge quantum mechanics with special relativity with a covariant equation such as the [[w:Dirac equation|Dirac equation]]. In other days, the relativistic quantum mechanics is now abandoned in favour of the quantum theory of fields.

    This could lead to a wide variety of important applications, including lightning-fast quantum computers and uncrackable encryption of private messages. It also moves researchers a step closer to viewing the molecular world in action – being able to see the making and breaking of bonds, which controls biological processes such as enzymatic reactions and cellular dynamics.

    The August issue of Nature Photonics features this breakthrough as its cover story.

    “Our work is the first to capture the motion of one molecule in real time,” Apkarian said. While still images of single molecules have been possible since the 1980s, recording a molecule’s extremely rapid movements had proven elusive.

    In addition to using precisely tuned, ultrafast lasers and microscopes, the researchers had to equip the molecule with a tiny antenna consisting of two gold nanospheres in order to track its activity and record measurements over the course of an hour.

    When the many repeated measurements were averaged, an astonishing finding emerged: The molecule was oscillating from one quantum state to another.

    The scientists have produced a movie in which a small, glowing dot appears to emit pulses of bright light. “That’s the light broadcast from the antenna every time the molecule completes a cycle of its vibrational motion,” Apkarian said. “The bond moves at a rate of 1013 cycles per second – a million, million times 10 cycles in one second.” Making the movie was like freeze-frame photography with a very fast flash and repeating the measurement over and over again.

    Seeing a molecule as it moves is “essential to a deeper understanding of how it forms and breaks chemical bonds,” Potma said. “The aim of the present experiment was to demonstrate that we can capture a molecule in motion on its own timescale.”

    The next and even more ambitious goal is to acquire moving images of molecules in their natural environment without tethering them to an antenna. “Ultimately, we’d like to be able to [examine] a molecule … as it’s undergoing chemistry,” Apkarian said.

    See the full article here.

    About Phys.org in 100 Words

    Phys.org™ (formerly Physorg.com) is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

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  • richardmitnick 3:10 pm on September 15, 2014 Permalink | Reply
    Tags: , , Quantum Physics   

    From BNL: “Elusive Quantum Transformations Found Near Absolute Zero” 

    Brookhaven Lab

    September 15, 2014
    Justin Eure, (631) 344-2347 or Peter Genzer, (631) 344-3174

    Brookhaven Lab and Stony Brook University researchers measure the quantum fluctuations behind a novel magnetic material’s ultra-cold ferromagnetic phase transition.

    Heat drives classical phase transitions—think solid, liquid, and gas—but much stranger things can happen when the temperature drops. If phase transitions occur at the coldest temperatures imaginable, where quantum mechanics reigns, subtle fluctuations can dramatically transform a material.

    Scientists from the U.S. Department of Energy’s Brookhaven National Laboratory and Stony Brook University have explored this frigid landscape of absolute zero to isolate and probe these quantum phase transitions with unprecedented precision.

    two
    Liusuo Wu, a Stony Brook University Ph.D. student and lead author on the study, with his postdoctoral advisor (and study coauthor) Meigan Aronson, a Brookhaven Lab physicist and Stony Brook professor

    “Under these cold conditions, the electronic, magnetic, and thermodynamic performance of metallic materials is defined by these elusive quantum fluctuations,” said study coauthor Meigan Aronson, a physicist at Brookhaven Lab and professor at Stony Brook. “For the first time, we have a picture of one of the most fundamental electron states without ambient heat obscuring or complicating those properties.”

    The scientists explored the onset of ferromagnetism—the same magnetic polarization exploited in advanced electronic devices, electrical motors, and even refrigerator magnets—in a custom-synthesized iron compound as it approached absolute zero.

    The research provides new methods to identify and understand novel materials with powerful and unexpected properties, including superconductivity—the ability to conduct electricity with perfect efficiency. The study will be published online Sept. 15, 2014, in the journal Proceedings of the National Academy of Sciences.

    “Exposing this quantum phase transition allows us to predict and potentially boost the performance of new materials in practical ways that were previously only theoretical,” said study coauthor and Brookhaven Lab physicist Alexei Tsvelik.

    Mapping Quantum Landscapes

    cry
    Rendering of the near–perfect crystal structure of the yttrium–iron–aluminum compound used in the study. The two–dimensional layers of the material allowed the scientists to isolate the magnetic ordering that emerged near absolute zero.

    The presence of heat complicates or overpowers the so-called quantum critical fluctuations, so the scientists conducted experiments at the lowest possible temperatures.

    “The laws of thermodynamics make absolute zero unreachable, but the quantum phase transitions can actually be observed at nonzero temperatures,” Aronson said. “Even so, in order to deduce the full quantum mechanical nature, we needed to reach temperatures as low as 0.06 Kelvin—much, much colder than liquid helium or even interstellar space.”

    The researchers used a novel compound of yttrium, iron, and aluminum (YFe2Al10), which they discovered while searching for new superconductors. This layered, metallic material sits poised on the threshold of ferromagnetic order, a key and very rare property.

    “Our thermodynamic and magnetic measurements proved that YFe2Al10 becomes ferromagnetic exactly at absolute zero—a sharp contrast to iron, which is ferromagnetic well above room temperature,” Aronson said. “Further, we used magnetic fields to reverse this ferromagnetic order, proving that quantum fluctuations were responsible.”

    The collaboration produced near-perfect samples to prove that material defects could not impact the results. They were also the first group to prepare YFe2Al10 in single-crystal form, which allowed them to show that the emergent magnetism resided within two-dimensional layers.

    “As the ferromagnetism decayed with heat or applied magnetic fields, we used theory to identify the spatial and temporal fluctuations that drove the transition,” Tsvelik said. “That fundamental information provides insight into countless other materials.”

    Quantum Clues to New Materials

    The scientists plan to modify the composition of YFe2Al10 so that it becomes ferromagnetic at nonzero temperatures, opening another window onto the relationship between temperature, quantum transitions, and material performance.

    “Robust magnetic ordering generally blocks superconductivity, but suppressing this state might achieve the exact balance of quantum fluctuations needed to realize unconventional superconductivity,” Tsvelik said. “It is a matter of great experimental and theoretical interest to isolate these competing quantum interactions that favor magnetism in one case and superconductivity on the other.”

    Added Aronson, “Having more examples displaying this zero-temperature interplay of superconductivity and magnetism is crucial as we develop a holistic understanding of how these phenomena are related and how we might ultimately control these properties in new generations of materials.”

    Other authors on this study include Liusuo Wu, Moosung Kim, and Keeseong Park, all of Stony Brook University’s Department of Physics and Astronomy.

    The research was conducted at Brookhaven Lab’s Condensed Matter Physics and Materials Science Department and supported by the U.S. Department of Energy’s Office of Science (BES).

    BNL Campus

    See the full article here.

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world.Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 2:21 pm on August 19, 2014 Permalink | Reply
    Tags: , , , Quantum Physics,   

    From Quanta: “At Multiverse Impasse, a New Theory of Scale” 

    Quanta Magazine
    Quanta Magazine

    August 18, 2014
    Natalie Wolchover

    Mass and length may not be fundamental properties of nature, according to new ideas bubbling out of the multiverse.

    Though galaxies look larger than atoms and elephants appear to outweigh ants, some physicists have begun to suspect that size differences are illusory. Perhaps the fundamental description of the universe does not include the concepts of “mass” and “length,” implying that at its core, nature lacks a sense of scale.

    This little-explored idea, known as scale symmetry, constitutes a radical departure from long-standing assumptions about how elementary particles acquire their properties. But it has recently emerged as a common theme of numerous talks and papers by respected particle physicists. With their field stuck at a nasty impasse, the researchers have returned to the master equations that describe the known particles and their interactions, and are asking: What happens when you erase the terms in the equations having to do with mass and length?

    Nature, at the deepest level, may not differentiate between scales. With scale symmetry, physicists start with a basic equation that sets forth a massless collection of particles, each a unique confluence of characteristics such as whether it is matter or antimatter and has positive or negative electric charge. As these particles attract and repel one another and the effects of their interactions cascade like dominoes through the calculations, scale symmetry “breaks,” and masses and lengths spontaneously arise.

    Similar dynamical effects generate 99 percent of the mass in the visible universe. Protons and neutrons are amalgams — each one a trio of lightweight elementary particles called quarks. The energy used to hold these quarks together gives them a combined mass that is around 100 times more than the sum of the parts. “Most of the mass that we see is generated in this way, so we are interested in seeing if it’s possible to generate all mass in this way,” said Alberto Salvio, a particle physicist at the Autonomous University of Madrid and the co-author of a recent paper on a scale-symmetric theory of nature.

    In the equations of the “Standard Model of particle physics”, only a particle discovered in 2012, called the Higgs boson, comes equipped with mass from the get-go. According to a theory developed 50 years ago by the British physicist Peter Higgs and associates, it doles out mass to other elementary particles through its interactions with them. Electrons, W and Z bosons, individual quarks and so on: All their masses are believed to derive from the Higgs boson — and, in a feedback effect, they simultaneously dial the Higgs mass up or down, too.

    sm
    The Standard Model of elementary particles, with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    The new scale symmetry approach rewrites the beginning of that story.

    as
    Alessandro Strumia of the University of Pisa, pictured speaking at a conference in 2013, has co-developed a scale-symmetric theory of particle physics called “agravity.” Thomas Lin/Quanta Magazine

    “The idea is that maybe even the Higgs mass is not really there,” said Alessandro Strumia, a particle physicist at the University of Pisa in Italy. “It can be understood with some dynamics.”

    The concept seems far-fetched, but it is garnering interest at a time of widespread soul-searching in the field. When the Large Hadron Collider at CERN Laboratory in Geneva closed down for upgrades in early 2013, its collisions had failed to yield any of dozens of particles that many theorists had included in their equations for more than 30 years. The grand flop suggests that researchers may have taken a wrong turn decades ago in their understanding of how to calculate the masses of particles.

    “We’re not in a position where we can afford to be particularly arrogant about our understanding of what the laws of nature must look like,” said Michael Dine, a professor of physics at the University of California, Santa Cruz, who has been following the new work on scale symmetry. “Things that I might have been skeptical about before, I’m willing to entertain.”

    The Giant Higgs Problem

    The scale symmetry approach traces back to 1995, when William Bardeen, a theoretical physicist at Fermi National Accelerator Laboratory in Batavia, Ill., showed that the mass of the Higgs boson and the other Standard Model particles could be calculated as consequences of spontaneous scale-symmetry breaking. But at the time, Bardeen’s approach failed to catch on. The delicate balance of his calculations seemed easy to spoil when researchers attempted to incorporate new, undiscovered particles, like those that have been posited to explain the mysteries of dark matter and gravity.

    Instead, researchers gravitated toward another approach called “supersymmetry” that naturally predicted dozens of new particles. One or more of these particles could account for dark matter. And supersymmetry also provided a straightforward solution to a bookkeeping problem that has bedeviled researchers since the early days of the Standard Model.

    Supersymmetry standard model
    Standard Model of Supersymmetry

    In the standard approach to doing calculations, the Higgs boson’s interactions with other particles tend to elevate its mass toward the highest scales present in the equations, dragging the other particle masses up with it. “Quantum mechanics tries to make everybody democratic,” explained theoretical physicist Joe Lykken, deputy director of Fermilab and a collaborator of Bardeen’s. “Particles will even each other out through quantum mechanical effects.”

    This democratic tendency wouldn’t matter if the Standard Model particles were the end of the story. But physicists surmise that far beyond the Standard Model, at a scale about a billion billion times heavier known as the “Planck mass,” there exist unknown giants associated with gravity. These heavyweights would be expected to fatten up the Higgs boson — a process that would pull the mass of every other elementary particle up to the Planck scale. This hasn’t happened; instead, an unnatural hierarchy seems to separate the lightweight Standard Model particles and the Planck mass.

    With his scale symmetry approach, Bardeen calculated the Standard Model masses in a novel way that did not involve them smearing toward the highest scales. From his perspective, the lightweight Higgs seemed perfectly natural. Still, it wasn’t clear how he could incorporate Planck-scale gravitational effects into his calculations.

    Meanwhile, supersymmetry used standard mathematical techniques, and dealt with the hierarchy between the Standard Model and the Planck scale directly. Supersymmetry posits the existence of a missing twin particle for every particle found in nature. If for each particle the Higgs boson encounters (such as an electron) it also meets that particle’s slightly heavier twin (the hypothetical “selectron”), the combined effects would nearly cancel out, preventing the Higgs mass from ballooning toward the highest scales. Like the physical equivalent of x + (–x) ≈ 0, supersymmetry would protect the small but non-zero mass of the Higgs boson. The theory seemed like the perfect missing ingredient to explain the masses of the Standard Model — so perfect that without it, some theorists say the universe simply doesn’t make sense.

    Yet decades after their prediction, none of the supersymmetric particles have been found. “That’s what the Large Hadron Collider has been looking for, but it hasn’t seen anything,” said Savas Dimopoulos, a professor of particle physics at Stanford University who helped develop the supersymmetry hypothesis in the early 1980s. “Somehow, the Higgs is not protected.”

    The LHC will continue probing for convoluted versions of supersymmetry when it switches back on next year, but many physicists have grown increasingly convinced that the theory has failed. Just last month at the International Conference of High-Energy Physics in Valencia, Spain, researchers analyzing the largest data set yet from the LHC found no evidence of supersymmetric particles. (The data also strongly disfavors an alternative proposal called “technicolor.”)

    The multiverse hypothesis has surged in begrudging popularity in recent years. But the argument feels like a cop-out to many, or at least a huge letdown.

    The implications are enormous. Without supersymmetry, the Higgs boson mass seems as if it is reduced not by mirror-image effects but by random and improbable cancellations between unrelated numbers — essentially, the initial mass of the Higgs seems to exactly counterbalance the huge contributions to its mass from gluons, quarks, gravitational states and all the rest. And if the universe is improbable, then many physicists argue that it must be one universe of many: just a rare bubble in an endless, foaming “multiverse.” We observe this particular bubble, the reasoning goes, not because its properties make sense, but because its peculiar Higgs boson is conducive to the formation of atoms and, thus, the rise of life. More typical bubbles, with their Planck-size Higgs bosons, are uninhabitable.

    “It’s not a very satisfying explanation, but there’s not a lot out there,” Dine said.

    As the logical conclusion of prevailing assumptions, the multiverse hypothesis has surged in begrudging popularity in recent years. But the argument feels like a cop-out to many, or at least a huge letdown. A universe shaped by chance cancellations eludes understanding, and the existence of unreachable, alien universes may be impossible to prove. “And it’s pretty unsatisfactory to use the multiverse hypothesis to explain only things we don’t understand,” said Graham Ross, an emeritus professor of theoretical physics at the University of Oxford.

    The multiverse ennui can’t last forever.

    “People are forced to adjust,” said Manfred Lindner, a professor of physics and director of the Max Planck Institute for Nuclear Physics in Heidelberg who has co-authored several new papers on the scale symmetry approach. The basic equations of particle physics need something extra to rein in the Higgs boson, and supersymmetry may not be it. Theorists like Lindner have started asking, “Is there another symmetry that could do the job, without creating this huge amount of particles we didn’t see?”

    Wrestling Ghosts

    Picking up where Bardeen left off, researchers like Salvio, Strumia and Lindner now think scale symmetry may be the best hope for explaining the small mass of the Higgs boson. “For me, doing real computations is more interesting than doing philosophy of multiverse,” said Strumia, “even if it is possible that this multiverse could be right.”

    For a scale-symmetric theory to work, it must account for both the small masses of the Standard Model and the gargantuan masses associated with gravity. In the ordinary approach to doing the calculations, both scales are put in by hand at the beginning, and when they connect in the equations, they try to even each other out. But in the new approach, both scales must arise dynamically — and separately — starting from nothing.

    “The statement that gravity might not affect the Higgs mass is very revolutionary,” Dimopoulos said.

    A theory called “agravity” (for “adimensional gravity”) developed by Salvio and Strumia may be the most concrete realization of the scale symmetry idea thus far. Agravity weaves the laws of physics at all scales into a single, cohesive picture in which the Higgs mass and the Planck mass both arise through separate dynamical effects. As detailed in June in the Journal of High-Energy Physics, agravity also offers an explanation for why the universe inflated into existence in the first place. According to the theory, scale-symmetry breaking would have caused an exponential expansion in the size of space-time during the Big Bang.

    However, the theory has what most experts consider a serious flaw: It requires the existence of strange particle-like entities called “ghosts.” Ghosts either have negative energies or negative probabilities of existing — both of which wreck havoc on the equations of the quantum world.

    “Negative probabilities rule out the probabilistic interpretation of quantum mechanics, so that’s a dreadful option,” said Kelly Stelle, a theoretical particle physicist at Imperial College, London, who first showed in 1977 that certain gravity theories give rise to ghosts. Such theories can only work, Stelle said, if the ghosts somehow decouple from the other particles and keep to themselves. “Many attempts have been made along these lines; it’s not a dead subject, just rather technical and without much joy,” he said.

    mc
    Marcela Carena, a senior scientist at Fermi National Accelerator Laboratory in Batavia, Ill.Courtesy of Marcela Carena

    Strumia and Salvio think that, given all the advantages of agravity, ghosts deserve a second chance. “When antimatter particles were first considered in equations, they seemed like negative energy,” Strumia said. “They seemed nonsense. Maybe these ghosts seem nonsense but one can find some sensible interpretation.”

    Meanwhile, other groups are crafting their own scale-symmetric theories. Lindner and colleagues have proposed a model with a new “hidden sector” of particles, while Bardeen, Lykken, Marcela Carena and Martin Bauer of Fermilab and Wolfgang Altmannshofer of the Perimeter Institute for Theoretical Physics in Waterloo, Canada, argue in an Aug. 14 paper that the scales of the Standard Model and gravity are separated as if by a phase transition. The researchers have identified a mass scale where the Higgs boson stops interacting with other particles, causing their masses to drop to zero. It is at this scale-free point that a phase change-like crossover occurs. And just as water behaves differently than ice, different sets of self-contained laws operate above and below this critical point.

    To get around the lack of scales, the new models require a calculation technique that some experts consider mathematically dubious, and in general, few will say what they really think of the whole approach. It is too different, too new. But agravity and the other scale symmetric models each predict the existence of new particles beyond the Standard Model, and so future collisions at the upgraded LHC will help test the ideas.

    In the meantime, there’s a sense of rekindling hope.

    “Maybe our mathematics is wrong,” Dine said. “If the alternative is the multiverse landscape, that is a pretty drastic step, so, sure — let’s see what else might be.

    See the full article here.

    Formerly known as Simons Science News, Quanta Magazine is an editorially independent online publication launched by the Simons Foundation to enhance public understanding of science. Why Quanta? Albert Einstein called photons “quanta of light.” Our goal is to “illuminate science.” At Quanta Magazine, scientific accuracy is every bit as important as telling a good story. All of our articles are meticulously researched, reported, edited, copy-edited and fact-checked.

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  • richardmitnick 4:14 pm on August 7, 2013 Permalink | Reply
    Tags: , , Quantum Physics   

    From Caltech: “Caltech Team Produces Squeezed Light Using a Silicon Micromechanical System” 

    Caltech Logo
    Caltech

    08/07/2013
    Kimm Fesenmaier

    “One of the many counterintuitive and bizarre insights of quantum mechanics is that even in a vacuum—what many of us think of as an empty void—all is not completely still. Low levels of noise, known as quantum fluctuations, are always present. Always, that is, unless you can pull off a quantum trick. And that’s just what a team led by researchers at the California Institute of Technology (Caltech) has done. The group has engineered a miniature silicon system that produces a type of light that is quieter at certain frequencies—meaning it has fewer quantum fluctuations—than what is usually present in a vacuum.

    quant
    (a) SEM image of the silicon micromechanical resonator used to generate squeezed light. Light is coupled into the device using a narrow waveguide and reflects off a back mirror formed by a linear array of etched holes. Upon reflection, the light interacts with a pair of double-nanobeams (micromechanical resonator/optical cavity), which are deflected in a way that tends to cancel fluctuations in the light. (b) Numerical model of the differential in-plane motion of the nanobeams. Credit: Caltech/Amir Safavi-Naeini, Simon Groeblacher, and Jeff Hill

    This special type of light with fewer fluctuations is known as squeezed light and is useful for making precise measurements at lower power levels than are required when using normal light. Although other research groups previously have produced squeezed light, the Caltech team’s new system, which is miniaturized on a silicon microchip, generates the ultraquiet light in a way that can be more easily adapted to a variety of sensor applications.

    ‘This system should enable a new set of precision microsensors capable of beating standard limits set by quantum mechanics,’ says Oskar Painter, a professor of applied physics at Caltech and the senior author on a paper that describes the system; the paper appears in the August 8 issue of the journal Nature. ‘Our experiment brings together, in a tiny microchip package, many aspects of work that has been done in quantum optics and precision measurement over the last 40 years.'”

    See the full article here.

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


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  • richardmitnick 2:54 pm on July 25, 2013 Permalink | Reply
    Tags: , , , , , , Quantum Physics, , Superfluids   

    From M.I.T.: “Superfluid turbulence through the lens of black holes” 

    Study finds behavior of the turbulent flow of superfluids is opposite that of ordinary fluids.

    July 25, 2013
    Jennifer Chu, MIT News Office

    “A superfluid moves like a completely frictionless liquid, seemingly able to propel itself without any hindrance from gravity or surface tension. The physics underlying these materials — which appear to defy the conventional laws of physics — has fascinated scientists for decades.

    fluid
    Black hole physics shows that superfluids in turbulence behave much like cigarette smoke. Image: Christine Daniloff

    Think of the assassin T-1000 in the movie “Terminator 2: Judgment Day” — a robotic shape-shifter made of liquid metal. Or better yet, consider a real-world example: liquid helium. When cooled to extremely low temperatures, helium exhibits behavior that is otherwise impossible in ordinary fluids. For instance, the superfluid can squeeze through pores as small as a molecule, and climb up and over the walls of a glass. It can even remain in motion years after a centrifuge containing it has stopped spinning.

    Now physicists at MIT have come up with a method to mathematically describe the behavior of superfluids — in particular, the turbulent flows within superfluids. They publish their results this week in the journal Science.

    ‘Turbulence provides a fascinating window into the dynamics of a superfluid,’ says Allan Adams, an associate professor of physics at MIT. ‘Imagine pouring milk into a cup of tea. As soon as the milk hits the tea, it flares out into whirls and eddies, which stretch and split into filigree. Understanding this complicated, roiling turbulent state is one of the great challenges of fluid dynamics. When it comes to superfluids, whose detailed dynamics depend on quantum mechanics, the problem of turbulence is an even tougher nut to crack.’

    To describe the underlying physics of a superfluid’s turbulence, Adams and his colleagues drew comparisons with the physics governing black holes. At first glance, black holes — extremely dense, gravitationally intense objects that pull in surrounding matter and light — may not appear to behave like a fluid. But the MIT researchers translated the physics of black holes to that of superfluid turbulence, using a technique called holographic duality.

    Consider, for example, a holographic image on a magazine cover. The data, or pixels, in the image exist on a flat surface, but can appear three-dimensional when viewed from certain angles. An engineer could conceivably build an actual 3-D replica based on the information, or dimensions, found in the 2-D hologram.

    ‘If you take that analogy one step further, in a certain sense you can regard various quantum theories as being a holographic image of a world with one extra dimension,’ says Paul Chesler, a postdoc in MIT’s Department of Physics.

    Taking this cosmic line of reasoning, Adams, Chesler and colleagues used holographic duality as a ‘dictionary’ to translate the very well-characterized physics of black holes to the physics of superfluid turbulence.

    To the researchers’ surprise, their calculations showed that turbulent flows of a class of superfluids on a flat surface behave not like those of ordinary fluids in 2-D, but more like 3-D fluids, which morph from relatively uniform, large structures to smaller and smaller structures. The result is much like cigarette smoke: From a burning tip, smoke unfurls in a single stream that quickly disperses into smaller and smaller eddies. Physicists refer to this phenomenon as an “energy cascade.”

    ‘For superfluids, whether such energy cascades exist is an open question,’ says Hong Liu, an associate professor of physics at MIT. ‘People have been making all kinds of claims, but there hasn’t been any smoking-gun type of evidence that such a cascade exists. In a class of superfluids, we produced very convincing evidence for the direction of this kind of flow, which would otherwise be very hard to obtain.’”

    See the full article here.


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