Title | Collective versus local measurements in a qubit mixed-state estimation |
Publication Type | Journal Article |
Year of Publication | 2004 |
Authors | Bagan, E, Baig, M, Muñoz-Tapia, R, Rodriguez, A |
Journal | Physical Review A (Atomic, Molecular, and Optical Physics) |
Volume | 69 |
Issue | 1 |
Pagination | 010304 |
Date Published | 01/2004 |
ISSN | 1050-2947 |
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 1/N. 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 1/N1/4, while our approach leads to an error proportional to 1/N3/4. |
URL | http://link.aps.org/doi/10.1103/PhysRevA.69.010304 |
DOI | 10.1103/PhysRevA.69.010304 |
