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Demonstration of an all-optical quantum controlled-NOT gate 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. Paper and press release UQ media release and contact details Nature paper web site Local copy of paper (PDF) Image 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! Media reports of this work Commsworld: Untangling Quantum Computing at Queensland Uni - An Open and Shut Gate Commsworld : Interview: UQ's Dr Andrew White - Quanta, Photons, and Things Hard to See New Scientist: Optical gate kick-starts quantum computer race, p. 27, November 22, 2003 ABC Science Online: Spooky bits propel quantum computer ABC PM Programme: Quantum computer in development       (RealAudio file) Monitor: Light work of quantum computers, Vol. 28 Issue 5 page 2, December 2003 The R & D Review: Quantum computing breakthrough, December 2003/January 2004 The 7:30 Report: Brisbane team leads ground-breaking project Australasian Science: "Quantum Leap for Computing" January/February 2004.

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last update 12.12.2003,