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May 09, 2008

Quantum dot based quantum logic gate proven possible

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.

"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," says Stanford applied physics doctoral student Ilya Fushman, a lead author on the paper along with two other doctoral students from the Vuckovic group, Dirk Englund and Andrei Faraon. "So we showed that such a gate is possible and demonstrated the first necessary steps in that direction."

The team has demonstrated that when the two photons are identical, a phase shift of 12.6 degrees is achieved. This is only a fraction of the 180-degree rotation required to make a full logic gate, Vuckovic says, but by combining several of the devices in a row, her team expects to attain the needed effect. Also, when the signal and control photons are allowed to differ, the phase shifts can be up to 45 degrees.


Other challenges include eliminating manufacturing imperfections and reliably placing the quantum dots right where they need to be within the crystals, but the team is optimistic.

"We are hopeful that these engineering challenges can be overcome to open the path to chip-based high-fidelity quantum logic with photons," Vuckovic says

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