Optimal minimal measurements of mixed states
- 1 July 1999
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review A
- Vol. 60 (1) , 126-135
- https://doi.org/10.1103/physreva.60.126
Abstract
The optimal and minimal measuring strategy is obtained for a two-state system prepared in a mixed state with a probability given by any isotropic a priori distribution. We explicitly construct the specific optimal and minimal generalized measurements, which turn out to be independent of the a priori probability distribution, obtaining the best guesses for the unknown state as well as a closed expression for the maximal mean-average fidelity. We do this for up to three copies of the unknown state in a way that leads to the generalization to any number of copies, which we then present and prove.Keywords
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