NIST researchers create 'quantum cats' made of light

Sep 01, 2010
This is NIST research associate Thomas Gerrits at the laser table used to create "quantum cats" made of light. Credit: NIST

Researchers at the National Institute of Standards and Technology have created "quantum cats" made of photons (particles of light), boosting prospects for manipulating light in new ways to enhance precision measurements as well as computing and communications based on quantum physics.

The NIST experiments, described in a forthcoming paper,* repeatedly produced light pulses that each possessed two exactly opposite properties—specifically, opposite phases, as if the peaks of the 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.)

A "cat state" is a curiosity of the , where particles can exist in "superpositions" of two opposite properties simultaneously. Cat state is a reference to German physicist Erwin Schrödinger's famed 1935 theoretical notion of a cat that is both alive and dead simultaneously.

"This is a new state of light, predicted in 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."

These colorized plots of electric field values indicate how closely the NIST "quantum cats" (left) compare with theoretical predictions for a cat state (right). The purple spots and alternating blue contrast regions in the center of the images indicate the light is in the appropriate quantum state. Credit: Gerrits/NIST

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 , 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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More information: * T. Gerrits, S. Glancy, T. Clement , B. Calkins, A. Lita, A. Miller, A. Migdall, S.W. Nam, R. Mirin and E. Knill. Generation of optical coherent state superpositions by number-resolved photon subtraction from squeezed vacuum. Physical Review A. Forthcoming.

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User comments : 6

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Xaero
1.8 / 5 (4) Sep 01, 2010
Actually Schrodinger cat though experiment was misinterpreted from its very beginning, because cat in the box will be always entangled with the box and poison in it - not just with observer. The life is nothing more, then the specially entangled state of organic molecules in space-time. The intermediate time of cat's life existence is the time, required for poison to kill the cat. It means, the life-time of "quantum cats" is principally limited by quantum decoherence (i.e. by vacuum noise, illustratively speaking) as well. This is why so fast lasers pulses are required for detection of this intermediate state of lightweight electrons. At the case of real cat such time would be significantly longer, accordingly.
Hesperos
1.7 / 5 (3) Sep 01, 2010
Did the cat die?


It depends.
Skeptic_Heretic
not rated yet Sep 02, 2010
Actually Schrodinger cat though experiment was misinterpreted from its very beginning, because cat in the box will be always entangled with the box and poison in it - not just with observer.
There is no observer in the hypothetical of Schrodinger's Cat. The hypothetical merely explains superposition and quantum probability.
Hesperos
1 / 5 (1) Sep 02, 2010
I wonder if you feed them with quantum cat food made of quarks....
Xaero
1 / 5 (2) Sep 02, 2010
..there is no observer in the hypothetical of Schrodinger's Cat.
How can you know after then, that cat exists, it exists inside of box, in box with trigger and poison at the same moment?

You're assuming too much for observeless hypothesis. Without observer such cat could live outside of box safely and it could appear rather like green platypus... If you're sure, cat sits inside of box during whole experiment, you're expected to remain entangled with box via uninterrupted observation of it, and the cat remains entangled with internal walls of box.
Skeptic_Heretic
not rated yet Sep 03, 2010
How can you know after then, that cat exists, it exists inside of box, in box with trigger and poison at the same moment?
That is exactly the point.
You're assuming too much for observeless hypothesis. Without observer such cat could live outside of box safely and it could appear rather like green platypus... If you're sure, cat sits inside of box during whole experiment, you're expected to remain entangled with box via uninterrupted observation of it, and the cat remains entangled with internal walls of box.
You put the cat there. Once you close the box there is no observer. If there is an observer there is no entanglement, no superposition, and the cat is always dead. Good job completely missing the point of the example.

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