Such an application of using nonlinear optical crystals to make quantum logic gates, say the researchers, had remained in question until they presented a way to realize a quantum logic gate with this approach using established photonic circuit components.
"The problem was that if one has a photon travelling in a channel, the photon has a 'wave-packet' with a certain shape," says Dr. Kurt Jacobs, of the U.S. Army Combat Capabilities Development Command’s Army Research Laboratory. "For a quantum gate, you need the photon wave-packets to remain the same after the operation of the gate. Since nonlinearities distort wave-packets, the question was whether you could load the wave-packet into cavities, have them interact via a nonlinearity, and then emit the photons again so that they have the same wave-packets as they started with."
Once they designed the quantum logic gate, the researchers performed numerous computer simulations of the operation of the gate to demonstrate that it could, in theory, function appropriately. Actual construction of a quantum logic gate with this method, say the researchers, will first require significant improvements in the quality of certain photonic components.
"Based on the progress made over the last decade, we expect that it will take about ten years for the necessary improvements to be realized," says Heuck. "However, the process of loading and emitting a wave-packet without distortion is something that we should able to realize with current experimental technology, and so that is an experiment that we will be working on next."
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