Schrödinger’s Cat may be the most famous thought experiment of all time, but due to its quantum trickiness it must remain in the realm of the hypothetical for the time being. However, researchers suggest they might just be able to pull off a similar, smaller-scale experiment they call Schrödinger’s virus.

The physicist Erwin Schrödinger came up the the feline thought experiment in the 1930s, presenting it as a caution against applying quantum rules to the real, ‘classical’ world…. At its most fundamental level, quantum mechanics says that particles can only exist in discrete states. For example, researchers can measure the direction a particle spins as either ‘up’ or ‘down’, but nothing in between. Yet, as long as no one is looking, the particle exists in a combination of both states simultaneously, a strange blend known as a superposition [Nature News].

Schrödinger proposed an experiment where a cat would be put in box containing a vial of poison gas. A hammer would be suspended ready to smash down on the vial if triggered by the decay of a single atom of radioactive material. If no one looked inside the box, Schrödinger said, the radioactive atom would be in a superposition–both intact and decayed–and therefore the cat would exist in two states as well, being simultaneously alive and dead.

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In several labs around the world, sound waves are doing things they’ve never done before. Teams working in England and the Ukraine have made a sonic laser, or “saser,” which operates in the terahertz range, with sound waves oscillating more than a trillion times per second. Meanwhile, in an Israeli lab, researchers say they’ve created the first ever sonic black hole that traps sound waves and won’t let them escape.

The saser uses packets of sonic vibrations called “phonons” much like a regular laser uses photons. Specifically, the acoustic laser device consists of a sonic beam traveling through a “superlattice” constructed of 50 sheets of material each only atoms thick that are alternately made of gallium arsenide and aluminium arsenide, two materials found in semiconductor [CNET]. The phonons bounce back and forth inside the lattice, which causes more phonons to be released and amplifies the overall signal. The result is the formation of an intense series of synchronised phonons inside the stack, which leaves the device as a narrow saser beam of high-frequency ultrasound [New Scientist].

At the moment the terahertz saser, described in a paper published in the journal Physical Review B, is mainly a neat trick, but it may find practical applications down the line, says lead researcher Tony Kent. “Fifty years ago many eminent scientists said that light amplification by the stimulated emission of radiation [lasers] was no more than a scientific curiosity,” says Kent, but lasers are now used for everything from digital storage and cancer treatment to weaponry [New Scientist]. Kent says the new saser technology could lead to breakthroughs in imaging for tiny, nanoscale objects.

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In the realm of quantum mechanics, atoms and subatomic particles just don’t follow the rules that we’re governed by in the larger world of classical mechanics. For example, the theory of quantum mechanics predicts that two or more particles can become “entangled” so that even after they are separated in space, when an action is performed on one particle, the other particle responds immediately. Scientists still don’t know how the particles send these instantaneous messages to each other, but somehow, once they are entwined, they retain a fundamental connection [LiveScience].

Now, a new study has dragged entanglement a little bit closer to our classical world. Researchers managed to entangle two pairs of vibrating ions so that when the motion of one pair of ions was changed, the other pair reflected the change as well. Previously, researchers have entangled particles in much more esoteric ways, coordinating the spin of electrons or the polarization of photons. With this study, says coauthor John Jost, “We’ve entangled something that has never been entangled before, and it’s the kind of physical, oscillating system you see in the classical world, just much smaller” [LiveScience].

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French physicist Bernard d’Espagnat has won the annual Templeton Prize with its purse of $1.4 million; the prize is often given to scientists who find common ground between religion and science. Professor d’Espagnat, 87, worked with great luminaries of quantum physics but went on to address the philosophical questions that the field poses [BBC News]. 

Physicists may be more open to seeing a higher power behind the great mysteries of the universe than scientists in other disciplines: Including Dr. d’Espagnat, five of the past 10 Templeton winners have been physicists or have had strong connections to the discipline [The Christian Science Monitor]. 

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Researchers have accomplished teleportation, though not of the “Beam me up, Scotty” variety. Instead, they sent information between two individual atoms of the element ytterbium, which were suspended in separate containers three feet apart. Because the quantum information instantly hops from one atom to the other without ever crossing the space between the two, scientists call the transfer “teleportation” [Science News].

Over the years, teleportation experiments have demonstrated that quantum states – for example, the spin of a particle or the polarization of a photon – can be teleported using a variety of methods. But the researchers behind the latest experiment … claim that this is the first time information has been teleported between two separate atoms in unconnected enclosures [MSNBC]. Researchers say that atoms are a better bet than photons for storing quantum information because they’re easier to hold on to, and say that their system could one day be harnessed for spy-proof communication using quantum cryptography, or for powerful quantum computers.

The befuddling process of quantum teleportation is made possible by the what Einstein called the “spooky” properties of quantum materials. Until it’s measured, an atom or photon can remain in an ambiguous state of all possible values simultaneously. Whenever a particle is measured, though, this range of possibilities “collapses” into a single, distinct value. The original, uncommitted state is lost, and it’s this ability to hold multiple values at once that gives [quantum materials] such potential for high-performance computing [Science News].

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By harnessing a quantum mechanic force of repulsion researchers have caused nanoparticles to repel each other, and in their next experiment they plan to levitate a tiny gold nanosphere. The quantum force is part of the Casimir effect, first predicted in 1948 by the Dutch physicist Hendrik Casimir, which describes both the attraction and repulsion that occur between two tiny objects held close together in a vacuum. While the attractive force has previously been demonstrated, the new experiment marks the first time the repulsive force has been seen in a lab.

But the experiment wasn’t just a neat physics trick; the researchers say the repulsive force may one day be used in nanoscale devices. Lead author Jeremy Munday says the research may lend itself to producing ultrasensitive detectors and almost friction-free devices by separating their components via Casimir repulsion. “Where you would normally have friction,” he says, “you can start to greatly reduce that by having a repulsive interaction that doesn’t let the surfaces come into contact” [Scientific American].

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Encryption systems that rely on the “spooky” properties of quantum mechanics have long been hyped as the ultimate in spy- and hack-proof communication, and recently governments and large companies have begun sampling early examples of the technology. Now, scientists in Vienna have demonstrated a commercial telecommunications network protected by quantum cryptography, and say the system could be generally available in less than 10 years.

One of the researchers who worked out the basic idea behind quantum cryptography 25 years ago, Gilles Brassard, was on hand in Vienna to explain the mechanism. “All quantum security schemes are based on the Heisenberg Uncertainty Principle, on the fact that you cannot measure quantum information without disturbing it,” he explained. “Because of that, one can have a communications channel between two users on which it’s impossible to eavesdrop without creating a disturbance. An eavesdropper would create a mark on it. That was the key idea” [BBC News].

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It may not be a big market, but it’s presumably a lucrative one: To meet the needs of consumers who are in the business of transmitting classified national secrets, physicists are working on an absolutely secure communication system that uses the strange laws of quantum mechanics to encode information. The latest experiments in this field, called quantum cryptography, produced a system that researchers say would theoretically work to transmit information around the globe.

The system relies on a concept known as quantum entanglement to establish hack-proof communication. Entanglement allows two particles to be quantum-mechanically connected even when they are physically separated. Although the specific condition of either particle cannot be precisely known, taking measurements of one will instantly tell you something about the other. The trick can’t be used to actually send information, because each particle’s condition is random until it is measured. But entanglement can be used for encrypting data if a sender and a receiver make measurements on a number of entangled particles and then compare their results [Nature News].

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Of all the weirdness in the universe, the quantum mechanics phenomenon called “entanglement” may be the most mind-boggling. Physicists have long shaken their heads at the theory that two particles that become entangled will always and instantly mirror each other’s properties, no matter how far they are separated, which seems to go against all other physical understanding. In the everyday world, objects can organize themselves in just a few ways. For example, two people can coordinate their actions by talking directly with each other, or they can both receive instructions from a third source…. But quantum mechanics allows for a third way to coordinate information [Nature News].

Einstein rebelled against the notion of quantum entanglement, derisively calling it “spooky action at a distance”  [LiveScience]. Entanglement would look a lot less spooky if we could prove that an entangled object releases an unknown particle or some other signal at high speeds to influence its partner, giving the illusion of a simultaneous reaction [LiveScience]. But a new study shows that if some hidden signal is passing between the separated particles, it would have to travel at 10,000 times the speed of light. As this explanation seems impossible, the research team favors the alternate, weirder idea: that a measurement on one photon instantly influences the other [New Scientist].

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