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Researchers Build an All-Optical Transistor

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A representation of an optical switch.

Researchers have developed an optical switch that's controlled by a single photon.

Credit: Christine Daniloff

Researchers at the Massachusetts Institute of Technology (MIT), Harvard University, and the Vienna University of Technology have created an optical switch that’s controlled by a single photon.

Since quantum physics effects are more readily visible in individual particles than in particle groups, the ability to control the switch with a single photon could make the discovery especially meaningful in quantum computing. The switch uses two highly reflective mirrors that allow an optical signal to pass through when the switch is on. When the switch is off, approximately 20 percent of the light in the optical signal passes through the mirrors.

"If you had just one mirror, all the light would come back," says MIT professor Vladan Vuletic. "When you have two mirrors, something very strange happens."

The researchers filled the space between the mirrors with a gas of supercooled cesium atoms, and found that if a single gate photon is added at a different angle and changes one electron of one atom to a higher energy state, the physics of the cavity alters enough to stop light from passing through.

Stanford University professor Jelena Vuckovic believes the results can be replicated in physical systems that are easier to integrate into computer chips.

From MIT News
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