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Demonstration of an all-optical quantum controlled-NOT gate

Thursday, November 20, 2003

Background.
Quantum computers potentially offer tremendous computational power. One of the key elements in a possible quantum computer is the controlled- NOT, or CNOT, gate. In the November 20, 2003, issue of Nature, a team of researchers report an experiment performed in UQ's Quantum Technology Laboratory that unambiguously demonstrates and comprehensively characterises an optical quantum CNOT gate. The team consists of Drs Jeremy O'Brien and Geoffrey Pryde, Assoc.-Prof. Timothy Ralph, and Dr Andrew White, of the University of Queensland, and Dr David Branning, now of the Rose-Hulman Institute of Technology, Indiana.

This image represents the operation of the CNOT gate. The pair of spots at the bottom left are output modes of the photon source used to generate control and target qubits in the experiment. This image has been repeated to form the truth table: the left column represents the ideal input qubits (dim = 0, bright = 1); the right column represents the qubit outputs measured in the lab, where the intensities are scaled by the probabilities measured in our experiment. The entangled state is not shown, as it would look very strange indeed!

Paper and press release
Nature paper web site; Local copy of paper (PDF); UQ media release and contact details.

Media reports of this work