Collective versus local measurements in a qubit mixed-state estimation

E. Bagan; M. Baig; R. Muñoz-Tapia; A. Rodriguez

doi:10.1103/PhysRevA.69.010304

Collective versus local measurements in a qubit mixed-state estimation

E. Bagan, M. Baig, R. Muñoz-Tapia, A. Rodriguez

Research output: Contribution to journal › Article › Research › peer-review

34 Citations (Scopus)

Abstract

We discuss the problem of estimating a qubit mixed state. We give the optimal estimation that can be inferred from any given set of measurements. For collective measurements and for a large number N of copies, we show that the error in the estimation varies as [Formula Presented] For local measurements, we focus on the simpler case of states lying on the equatorial plane of the Bloch sphere. We show that the error using plain tomography varies as [Formula Presented] while our approach leads to an error proportional to [Formula Presented]. © 2004 The American Physical Society.

Original language	English
Article number	010304
Pages (from-to)	103041-103044
Journal	Physical Review A - Atomic, Molecular, and Optical Physics
Volume	69
Issue number	1
DOIs	https://doi.org/10.1103/PhysRevA.69.010304
Publication status	Published - 1 Jan 2004

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abstract = "We discuss the problem of estimating a qubit mixed state. We give the optimal estimation that can be inferred from any given set of measurements. For collective measurements and for a large number N of copies, we show that the error in the estimation varies as [Formula Presented] For local measurements, we focus on the simpler case of states lying on the equatorial plane of the Bloch sphere. We show that the error using plain tomography varies as [Formula Presented] while our approach leads to an error proportional to [Formula Presented]. {\textcopyright} 2004 The American Physical Society.",

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