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 |
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Article number | 010304 |
Pages (from-to) | 103041-103044 |
Journal | Physical Review A - Atomic, Molecular, and Optical Physics |
Volume | 69 |
Issue number | 1 |
DOIs | |
Publication status | Published - 1 Jan 2004 |