Purity estimation with separable measurements
Bagán Capella, Emili (Universitat Autònoma de Barcelona. Departament de Física)
Ballester, M. A. (University of Utrecht. Department of Mathematics)
Muñoz Tapia, Ramon (Universitat Autònoma de Barcelona. Departament de Física)
Romero-Isart, Oriol (Universitat Autònoma de Barcelona. Departament de Física)
American Physical Society

Data:	2005
Resum:	Given a large number N of copies of a qubit state of which we wish to estimate its purity, we prove that separable-measurement protocols can be as efficient as the optimal joint-measurement one if classical communication is used. This shows that the optimal estimation of the entanglement of a two-qubit state can also be achieved asymptotically with fully separable measurements. Thus, quantum memories provide no advantage in this situation. The relationship between our global Bayesian approach and the quantum Cramér-Rao bound is discussed.
Drets:	Tots els drets reservats.
Llengua:	Anglès
Document:	Article ; Versió publicada
Publicat a:	Physical review letters, Vol. 95, Issue 11 (September 2005) , p. 110504, ISSN 1079-7114

DOI: 10.1103/PhysRevLett.95.110504

4 p, 100.1 KB

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