dorsal/arxiv
View SchemaMeasuring the purity of a qubit state: entanglement estimation with fully separable measurements
| Authors | E. Bagan, M. A. Ballester, R. Munoz-Tapia, O. Romero-Isart |
|---|---|
| Categories | |
| ArXiv ID | quant-ph/0505083 |
| URL | https://arxiv.org/abs/quant-ph/0505083 |
| DOI | 10.1103/PhysRevLett.95.110504 |
| Journal | Enlarged version of Phys. Rev. Lett. 95, 110504 (2005) |
Abstract
Given a finite number $N$ of copies of a qubit state we compute the maximum fidelity that can be attained using joint-measurement protocols for estimating its purity. We prove that in the asymptotic $N\to\infty$ limit, separable-measurement protocols can be as efficient as the optimal joint-measurement one if classical communication is used. This in turn shows that the optimal estimation of the entanglement of a two-qubit state can also be achieved asymptotically with fully separable measurements. The relationship between our global Bayesian approach and the quantum Cramer-Rao bound is also discussed.
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"abstract": "Given a finite number $N$ of copies of a qubit state we compute the maximum\nfidelity that can be attained using joint-measurement protocols for estimating\nits purity. We prove that in the asymptotic $N\\to\\infty$ limit,\nseparable-measurement protocols can be as efficient as the optimal\njoint-measurement one if classical communication is used. This in turn shows\nthat the optimal estimation of the entanglement of a two-qubit state can also\nbe achieved asymptotically with fully separable measurements. The relationship\nbetween our global Bayesian approach and the quantum Cramer-Rao bound is also\ndiscussed.",
"arxiv_id": "quant-ph/0505083",
"authors": [
"E. Bagan",
"M. A. Ballester",
"R. Munoz-Tapia",
"O. Romero-Isart"
],
"categories": [
"quant-ph"
],
"doi": "10.1103/PhysRevLett.95.110504",
"journal_ref": "Enlarged version of Phys. Rev. Lett. 95, 110504 (2005)",
"title": "Measuring the purity of a qubit state: entanglement estimation with fully separable measurements",
"url": "https://arxiv.org/abs/quant-ph/0505083"
},
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