Physicists build a "quantum cat" out of light

The purple-and-blue blur you see here is a representation of light in a perfectly quantum state, or "cat state," where particles exhibit opposite properties simultaneously. Now scientists have created this seemingly impossible state - using lasers, of course.

The "cat" reference is to Schrödinger's Cat, a thought experiment created by the eponymous physicist where he explained quantum states by describing a box that contained a cat that was dead and alive simultaneously.

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The quantum cat was created at the National Institute for Standards and Technology in America, and the researchers explain that the image above on the left is what they created - while the image on the right is a theoretical model of what a quantum cat should look like. The two are nearly identical. You can tell the photons are in their cat state because of the characteristic shapes of the purple spots in the center of the image, as well as the alternating bars of blue. So yes, the blue and purple blob is a quantum cat, and I hope to see it turned into a lolcat as soon as possible.

The NIST researchers explain that they:

Repeatedly produced light pulses that each possessed two exactly opposite properties-specifically, opposite phases, as if the peaks of the light waves were superimposed on the troughs. Physicists call this an optical Schrödinger's cat. NIST's quantum cat is the first to be made by detecting three photons at once and is one of the largest and most well-defined cat states ever made from light. (Larger cat states have been created in different systems by other research groups, including one at NIST.) . . . "This is a new state of light, predicted in quantum optics for a long time," says NIST research associate Thomas Gerrits, lead author of the paper. "The technologies that enable us to get these really good results are ultrafast lasers, knowledge of the type of light needed to create the cat state, and photon detectors that can actually count individual photons."

And here's where it gets cool. The quantum cat was created with lasers:

The NIST team created their optical cat state by using an ultrafast laser pulse to excite special crystals to create a form of light known as a squeezed vacuum, which contains only even numbers of photons. A specific number of photons were subtracted from the squeezed vacuum using a device called a beam splitter. The photons were identified with a NIST sensor that efficiently detects and counts individual photons (see "NIST Detector Counts Photons With 99 Percent Efficiency"). Depending on the number of subtracted photons, the remaining light is in a state that is a good approximation of a quantum cat says Gerrits-the best that can be achieved because nobody has been able to create a "real" one, by, for instance, the quantum equivalent to superimposing two weak laser beams with opposite phases.

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via NIST

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