Purity Estimation with Separable Measurements

E. Bagan, M. A. Ballester, R. Muñoz-Tapia, and O. Romero-Isart
Phys. Rev. Lett. 95, 110504 – Published 9 September 2005

Abstract

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.

  • Received 17 June 2005

DOI:https://doi.org/10.1103/PhysRevLett.95.110504

©2005 American Physical Society

Authors & Affiliations

E. Bagan1, M. A. Ballester2, R. Muñoz-Tapia1, and O. Romero-Isart1

  • 1Grup de Física Teòrica & IFAE, Facultat de Ciències, Edifici Cn, Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona), Spain
  • 2Department of Mathematics, University of Utrecht, Box 80010, 3508 TA Utrecht, The Netherlands

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Issue

Vol. 95, Iss. 11 — 9 September 2005

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