Darmstadt 2008 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 28: Poster Quanteninformation

Q 28.3: Poster

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

Effect of local operations on entanglement-induced state ordering of two qubits — •Lars Erik Würflinger and Walter T. Strunz — Theoretical Quantum Dynamics, Institute of Physics, University of Freiburg, Hermann-Herder-Straße 3, 79104 Freiburg

Any measure of entanglement E induces an ordering of states. Local operations on a bi-partite quantum system cannot create entanglement; but in what way do they affect the ordering of states? Focussing on the two qubit case we find that there are no unital local channels that preserve the ordering for all states, with unitary and entanglement breaking channels being the only (trivial) exceptions, as has been conjectured by Ziman and Buzek [1]. However, when restricted to certain one-parameter families of states such as Werner states, or pure states, ordering based on concurrence is preserved under all local unital channels. We therefore investigate in more detail to what extend entanglement-induced state ordering is preserved for a restricted class of states (or channels).

[1] M. Ziman and V. Bužek: Entanglement-induced state ordering under local operations, Phys. Rev. A 61, 012312 (2006).