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DY: Fachverband Dynamik und Statistische Physik

DY 8: Quantum Dynamics, Decoherence, and Quantum Information I

DY 8.11: Hauptvortrag

Dienstag, 23. März 2010, 12:30–13:00, H38

Quantum search algorithms and quantum communication on networks — •Gregor Tanner and Birgit Hein — School of Mathematical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK

Quantum search algorithms - both for an ordered list and on an extended network - are based on propagating a well known initial quantum state into a localised target state. Grover's algorithm, one of the corner stones of modern quantum information theory, predicts a square root speed up of a search protocol based on wave mechanics compared to a ''classical'' search. I will discuss extensions of Grover's ideas to searches on networks. I will summarise the connections between quantum random walks, quantum searches and quantum graphs, and will offer a new interpretation of a quantum search in terms of avoided crossings and localised defect states.

Setting up a communication channel between two parties is in fact closely related to a two-way search. Starting from this observation, it will be shown that wave mechanics can be used to send signals efficiently between a sender and a receiver where neither party knows the address of the other. Possible experimental realisations will be discussed.