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The propagation of quantum information through a spin system

Presented by: 
T Osborne [Bristol]
Tuesday 28th September 2004 - 16:45 to 17:30
INI Seminar Room 1

It has been recently suggested that the dynamics of a quantum spin system may provide a natural mechanism for transporting quantum information. I'll show that one dimensional rings of qubits with fixed (time-independent) interactions, constant around the ring, allows high fidelity communication of quantum states. I'll then show that the problem of maximising the fidelity, in a restricted subspace of a single up spin, of the quantum communication is related to a classical problem in fourier wave analysis. By making use of this observation I'll argue that if both communicating parties have access to limited numbers of qubits in the ring (a fraction that vanishes in the limit of large rings) it is possible to make the communication arbitrarily good. I'll then show how to extend our results beyond the restricted 1-spin subspace. These results provide a novel interpretation of a spin systems as a second-quantised optical fibre or waveguide.

University of Cambridge Research Councils UK
    Clay Mathematics Institute London Mathematical Society NM Rothschild and Sons