Optimal Computation with Noisy Quantum Walks

SPEAKER: Dr. Viv Kendon, University of LeedsABSTRACT: Quantum versions of random walks on the line and cycle show a quadratic improvement in their spreading rate and mixing times respectively. The addition of decoherence to the quantum walk produces a more uniform distribution on the line, and even faster mixing on the cycle by removing the need for time-averaging to obtain a uniform distribution. By calculating the entanglement between the coin and the position of the quantum walker, the optimal decoherence rates are found to be such that all the entanglement is just removed by the time the final measurement is made. This requires only O(log T) random bits for a quantum walk of T steps.Bio: Viv Kendon works in the School of Physics and Astronomy at the University of Leeds, funded by a Royal Society University Research Fellowship, in the new Quantum Information group headed by Vlatko Vedral. Before this she was part of Peter Knight's Quantum Information and Quantum Optics Theory Group at Imperial College, and prior to Imperial (April 2000), was in the Computational Nonlinear & Quantum Optics group at Strathclyde University working on quantum measurement with Steven Barnett. Viv Kendon finished her PhD at Edinburgh in July 1999, in the Soft Condensed Matter group. Before her PhD, she used to work for GreenNet, a non-profit Internet service provider (now TWENTY years old!) and member the Association for Progressive Communications. She has also done work for Oxfam and Amnesty International. Prior to joining GreenNet she lived in Glasgow and was an active campaigner for Scottish Campagin for Nuclear Disarmament. Her first degree is from Oxford University, in Physics, and she has a Masters in Physics from UC Berkeley.Host: Todd Brun, tbrun@usc.edu

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