0510237v1

related topics
{state, states, entangled}
{state, phys, rev}
{measurement, state, measurements}
{photon, photons, single}
{bell, inequality, local}
{operator, operators, space}
{information, entropy, channel}
{let, theorem, proof}
{state, states, coherent}
{states, state, optimal}
{group, space, representation}

Observables suitable for restricting the fidelity to multipartite maximally entangled states

Koji Nagata, Masato Koashi, Nobuyuki Imoto

abstract: We present a class of observables which are suitable for determining the fidelity of a state to the multipartite Greenberger-Horne-Zeilinger (GHZ) state. Given an expectation value of an observable belonging to the class, we give a simple formula that gives a lower bound and an upper bound for the fidelity. Applying the formula to the GHZ-state preparation experiment by Pan {\it et al}. {[Nature (London) {\bf 403}, 515 (2000)]}, we show that the observed state lies outside of the class of biseparable mixed three-qubit states. We also show that for this class of operators, adopting the principle of minimum variance {[Phys. Rev. A {\bf 60}, 4338 (1999)]} in the state estimation always results in the state with the minimum fidelity.

oai_identifier:
oai:arXiv.org:quant-ph/0510237
categories:
quant-ph
comments:
6 pages
arxiv_id:
quant-ph/0510237
journal_ref:
Phys. Rev. A 65, 042314 (2002)
created:
2005-10-31

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