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Optimization of quantum universal detectors

G. M. D'Ariano·P. Perinotti·M. F. Sacchi
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Abstract

The expectation value of an arbitrary operator O can be obtained via a universal measuring apparatus that is independent of O, by changing only the data-processing of the outcomes. Such a ``universal detector'' performs a joint measurement on the system and on a suitable ancilla prepared in a fixed state, and is equivalent to a positive operator valued measure (POVM) for the system that is ``informationally complete''. The data processing functions generally are not unique, and we pose the problem of their optimization, providing some examples for covariant POVM's, in particular for SU(d) covariance group.

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G. M. D'Ariano, P. Perinotti, M. F. Sacchi. 2003-09-22. Optimization of quantum universal detectors. https://arxiv.org/abs/quant-ph/0309161

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