Decoherence in a system of many two-level atoms.
I show that the decoherence in a system of degenerate two-level atoms interacting with a bosonic heat bath is for any number of atoms governed by a generalized Hamming distance (called "decoherence metric") between the superposed quantum states, with a time-dependent metric tensor that is specific for the heat bath. The decoherence metric allows for the complete characterization of the decoherence of all possible superpositions of many-particle states, and can be applied to minimize the overall decoherence in a quantum memory. For qubits which are far apart, the decoherence is given by a function describing single-qubit decoherence times the standard Hamming distance. I apply the theory to cold atoms in an optical lattice interacting with blackbody radiation.
Braun
Daniel
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Laboratoire de Physique Théorique, IRSAMC, UMR 5152 du CNRS, Université Paul Sabatier, 118 route de Narbonne, 31062 Toulouse, France.