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Minimum Decision Cost for Quantum Ensembles

Dorje Brody·Bernhard Meister
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Abstract

For a given ensemble of $N$ independent and identically prepared particles, we calculate the binary decision costs of different strategies for measurement of polarised spin 1/2 particles. The result proves that, for any given values of the prior probabilities and any number of constituent particles, the cost for a combined measurement is always less than or equal to that for any combination of separate measurements upon sub-ensembles. The Bayes cost, which is that associated with the optimal strategy (i.e., a combined measurement) is obtained in a simple closed form.

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Dorje Brody, Bernhard Meister. 1995-07-14. Minimum Decision Cost for Quantum Ensembles. https://doi.org/10.1103/physrevlett.76.1

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