# Dresden 2006 – wissenschaftliches Programm

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# TT: Tiefe Temperaturen

## TT 29: Transport: Quantum Coherence and Quantum Information Systems - Part 1

### TT 29.4: Vortrag

### Donnerstag, 30. März 2006, 10:30–10:45, HSZ 304

**Decoherence of spatially separated qubits** — •Roland Doll, Sigmund Kohler, Martijn Wubs, and Peter Hänggi — Institut für Physik, Universität Augsburg, 86135 Augsburg

We consider spatially separated qubits coupled to a phonon field which acts as a heat bath and, thus, causes decoherence. For a theoretical description, it is frequently assumed that depending on the spatial separation, either each qubit couples to a separate bath or that all qubits couple via a collective coordinate to one common bath. For weak qubit-bath coupling it is in both cases possible to describe the dissipative dynamics within a Born-Markov approximation, i.e. one neglects memory effects induced by the bath.

In many experimental situations, however, the bath correlation length and the distances between the qubits are comparable such that neither limit is justified. Then it is necessary to take the spatial dependence of the phonon field explicitely into account. We developed a generalized master equation formalism for the dissipative dynamics which becomes intrinsically non-Markovian. The resulting memory effects and the limitations of a Markovian approximation are discussed.

This work is supported by the DFG through SFB631.