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Quantum optics

Photons made to dance together

Physicists have made two beams of light interact at the level of individual photons.

Getting photons to interact is important for all-optical computation and for producing new quantum states of light. Kristin Beck at the Massachusetts Institute of Technology in Cambridge and her colleagues crossed two beams of light inside a cavity filled with trapped and cooled caesium atoms. When photons from each beam tried to pass through the system at the same time, the trapped atoms changed their internal state, allowing only one photon to be transmitted, while the other one was reflected or scattered.

The interaction creates two entangled beams of light, which the authors say could eventually be used to improve the accuracy of measurements, such as of a gyroscope's rotation, that would otherwise be limited by the laws of quantum mechanics.

Phys. Rev. Lett. 113, 113603 (2014)

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Photons made to dance together. Nature 513, 463 (2014).

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