In computing, a logic gate is built to accept a set of inputs and, depending on their properties, provide a specific output. In the binary logic found in today's electrical computers, a certain gate will yield a "1" only if all of its inputs are "1"s. Otherwise it will yield a "0." Similarly, a quantum photonic gate would work by detecting the properties of input photons from two light beams, called "control" and "signal," and then producing an output based on those, such as by flipping the polarization of one of the input photons.
Computers based on the powerful properties of quantum mechanics have the potential to revolutionize information technology and security, but for decades they have remained more theoretical than practical, and difficult to scale up. That is changing, however, as demonstrated in a report this week in the journal Science.
In the paper, engineers and physicists from Stanford and the University of California at Santa Barbara demonstrate a potential progenitor of an essential component of quantum computers, "a logic gate" that enables interaction between just two particles of light.
The key advance is a solid state device that can reliably produce an interaction between the light particles, called photons. "We have demonstrated a system composed of a single quantum dot in a cavity that can be used to realize such a gate, and we demonstrated that two photons can be made to interact with each other via this system," Logic from light
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