



Quantum cats are hard to see
December 19, 2011
International team of researchers explain the difficulty of detecting quantum effects Are there parallel universes? And how will we know? This is one of many fascinations people hold about quantum physics. Researchers from the universities of Calgary and Waterloo in Canada and the University of Geneva in Switzerland have published a paper this week in Physical Review Letters explaining why we don't usually see the physical effects of quantum mechanics. "Quantum physics works fantastically well on small scales but when it comes to larger scales, it is nearly impossible to count photons very well. We have demonstrated that this makes it hard to see these effects in our daily life," says Dr. Christoph Simon, who teaches in the Department of Physics and Astronomy at the University of Calgary and is one of the lead authors of the paper entitled: Coarsegraining makes it hard to see micromacro entanglement. It's well known that quantum systems are fragile. When a photon interacts with its environment, even just a tiny bit, the superposition is destroyed. Superposition is a fundamental principle of quantum physics that says that systems can exist in all their possible states simultaneously. But when measured, only the result of one of the states is given. This effect is known as decoherence, and it has been studied intensively over the last few decades. The idea of decoherence as a thought experiment was raised by Erwin Schrödinger, one of the founding fathers of quantum physics, in his famous cat paradox: a cat in a box can be both dead and alive at the same time. But, according to the authors of this study, it turns out that decoherence is not the only reason why quantum effects are hard to see. Seeing quantum effects requires extremely precise measurements. Simon and his team studied a concrete example for such a "cat" by using a particular quantum state involving a large number of photons. "We show that in order to see the quantum nature of this state, one has to be able to count the number of photons in it perfectly," says Simon. "This becomes more and more difficult as the total number of photons is increased. Distinguishing one photon from two photons is within reach of current technology, but distinguishing a million photons from a million plus one is not." University of Calgary Related Quantum Physics Current Events and Quantum Physics News ArticlesDemystifying nanocrystal solar cellsScientists are focusing on nanometresized crystals for the next generation of solar cells. These nanocrystals have excellent optical properties. Forward look report on quantum biology presented in brussels The scientific community represented by about forty researchers and officials from research funding organisations gathered in Brussels on 23 January 2015 to present the outcomes of the European Science Foundation's (ESF) Foresight Activity on Research in Quantum Biology (FarQBio). Entanglement on a chip: Breakthrough promises secure communications and faster computersUnlike Bilbo's magic ring, which entangles human hearts, engineers have created a new microring that entangles individual particles of light, an important first step in a whole host of new technologies. Doing more with less: Steering a quantum path to improved internet security Research conducted at Griffith University in Queensland, Australia, may lead to greatly improved security of information transfer over the internet. Quantum physics just got less complicatedHere's a nice surprise: quantum physics is less complicated than we thought. An international team of researchers has proved that two peculiar features of the quantum world previously considered distinct are different manifestations of the same thing. The result is published 19 December in Nature Communications. Mathematicians prove the Umbral Moonshine ConjectureMonstrous moonshine, a quirky pattern of the monster group in theoretical math, has a shadow  umbral moonshine. Mathematicians have now proved this insight, known as the Umbral Moonshine Conjecture, offering a formula with potential applications for everything from number theory to geometry to quantum physics. Researchers use real data rather than theory to measure the cosmosFor the first time researchers have measured large distances in the Universe using data, rather than calculations related to general relativity. Fraudproof credit cards possible with quantum physicsCredit card fraud and identify theft are serious problems for consumers and industries. Though corporations and individuals work to improve safeguards, it has become increasingly difficult to protect financial data and personal information from criminal activity. 45year physics mystery shows a path to quantum transistorsAn odd, iridescent material that's puzzled physicists for decades turns out to be an exotic state of matter that could open a new path to quantum computers and other nextgeneration electronics. The mysterious 'action at a distance' between liquid containersFor several years, it has been known that superfluid helium housed in reservoirs located next to each other acts collectively, even when the channels connecting the reservoirs are too narrow and too long to allow for substantial flow. More Quantum Physics Current Events and Quantum Physics News Articles

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