Communications of the ACM
Quantum Computing With Light
Credit: Courtesy of Christine Daniloff
Researchers at the Massachusetts Institute of Technology (MIT) and Harvard University have conducted an experiment that enables a single photon to control the quantum state of another photon, a development that could lead to a quantum Internet that offers both stability and control by utilizing photons in superposition that can carry information stored as qubits rather than as ordinary bits.
The researchers developed an optical switch that consists of a small cluster of cesium atoms suspended between two tiny mirrors in a vacuum cavity. When a photon enters the cavity, it bounces back and forth between the mirrors, delaying its emission on the other side. If another photon has already struck the cesium atoms, then each pass through the cluster delays this second photon even more.
The delay induced by a single pass through the atoms would be imperceptible, but the mirror-lined cavity "allows us to pass the photon many, many times through the atoms. In our case, it's like passing the photon 40,000 times through the atoms," says MIT professor Vladan Vuletic.
When the second photon emerges from the cavity, it is either delayed, or extra-delayed, depending on whether another photon has preceded it, which could represent a bit of information.
From MIT News
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