Communications of the ACM
Quantum Sensor's Advantages Survive Entanglement Breakdown
In the researchers' system, a returning beam of light is mixed with a locally stored beam, and the correlation of their phase helps remove noise caused by interactions with the environment.
Credit: Jose-Luis Olivares / MIT
Massachusetts Institute of Technology (MIT) researchers have demonstrated that entanglement can improve the performance of optical sensors, even when it does not survive light's interaction with the environment, a development that furthers the progress toward quantum information processing.
As part of the MIT researchers' system, two beams of light are entangled, and one of them is stored locally in an optical fiber, while the other is projected into the environment. When light from the projected beam is reflected back, it carries information about the object it has encountered. However, this light also is corrupted by environmental influences, generally referred to as "noise." The researchers can suppress the noise and recover the information by recombining the projected beam with the locally stored beam. The local beam helps with noise suppression because its phase is correlated with that of the projected beam. Entangled beams start out with stronger correlations than classical beams, so even when noise causes entangled beams to fall back within classical limits, they still perform better than classical beams do under similar circumstances.
In tests comparing optical systems that used entangled light and classical light, the researchers found the entangled-light systems increased the signal-to-noise ratio, which is a measure of how much information can be recaptured from the reflected beam, by 20 percent.
From MIT News
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