Berlin 2005 – scientific programme

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TT: Tiefe Temperaturen

TT 13: Transport - Quantum Coherence and Quantum Information Systems

TT 13.12: Talk

Saturday, March 5, 2005, 11:45–12:00, TU H3027

Coherence stabilization of a driven two-qubit gate by AC fields — •Sigmund Kohler, Karen M. Fonseca Romero, and Peter Hänggi — Institut für Physik, Universität Augsburg

In order to perform logical operations, a quantum computer requires tunable nonlinear interactions between two qubits. In particular, a spin-spin interaction of the Heisenberg type has been proposed for the construction of a CNOT gate. The quality of a gate operation is affected by decoherence which results from the coupling of the qubits to external degrees of freedom. In this talk, we propose a coherence stabilization scheme which reduces the influence of bit-flip noise in two-qubit gate operations. As a microscopic model, we consider a pair of driven qubits coupled to a harmonic oscillator bath with an ohmic spectral density. The bath is eliminated within a Floquet-Bloch-Redfield formalism. This allows on the one hand to derive an approximate analytical solution for the dephasing and relaxation times and, on the other hand, provides a physical explanation of the observed coherence stabilization. Our analytical estimates are in good agreement with numerical results.

[1] K. M. Fonseca Romero, S. Kohler, and P. Hänggi, cond-mat/0409774.