Hamburg 2009 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 60: Quanteneffekte: Dekohärenz
Q 60.7: Talk
Friday, March 6, 2009, 12:00–12:15, VMP 6 HS-D
Scalability of GHZ and random-state entanglement in the presence of decoherence — •de Melo Fernando1, Leandro Aolita2, Daniel Cavalcanti2, Antonio Acin2,3, Alejo Salles4,1, Markus Tiersch1, and Andreas Buchleitner1 — 1Physikalisches Institut, Albert-Ludwigs-Universität Freiburg — 2ICFO - Institut de Ciències Fotòniques — 3ICREA - Institució Catalana de Recerca i Estudis Avançats — 4Instituto de Física, Universidade Federal do Rio de Janeiro
We derive analytical upper bounds for the entanglement of generalized Greenberger-Horne-Zeilinger (GHZ) states locally coupled to dephasing, depolarizing, and thermal reservoirs. The derivation is carried out under very weak constraints, and holds for any convex quantifier of entanglement.
The obtained bounds reveal an exponential entanglement decay with the number of qubits – the robustness of the generalized GHZ states decreases exponentially with the system size. This poses a severe limitation to many quantum communication protocols.
A comparison between the entanglement decay of randomly generated states with the GHZ family shows that the former decays slower, thus violating the previously obtained bounds. Furthermore, the random state’s entanglement is more robust against noise for larger system size.