Darmstadt 2008 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 28: Poster Quanteninformation

Q 28.2: Poster

Tuesday, March 11, 2008, 16:30–19:00, Poster C2

Dephasing of two Qubits — •Julius Helm and Walter T. Strunz — Theoretical Quantum Dynamics, Institute of Physics, University of Freiburg, Hermann-Herder-Strasse 3, 79104 Freiburg, Germany

We study quantum channels applied to systems of two qubits that may be described in terms of stochastically fluctuating classical fields (so-called random external fields or REF). For arbitrary pure initial states we examine the sensitivity of purity and entanglement of the composite quantum system when subject to dephasing channels, i.e., dissipationless quantum channels. With concurrence as entanglement measure we are able to identify certain accessible regions in the purity-concurrence diagram, generalizing results obtained for local unital channels [1]. Furthermore, we identify a class of initial states that are robust against disentanglement when only dephasing channels acting on both qubits simultaneously are involved.

[1] Ziman, M and Bužek, V, "Concurrence vs. purity: Influence of local channels on Bell states of two qubits", Phys. Rev. A 72, 052325 (2005)