Quantum-state comparison and discrimination

A. Hayashi, T. Hashimoto, and M. Horibe
Phys. Rev. A 97, 052323 – Published 21 May 2018

Abstract

We investigate the performance of discrimination strategy in the comparison task of known quantum states. In the discrimination strategy, one infers whether or not two quantum systems are in the same state on the basis of the outcomes of separate discrimination measurements on each system. In some cases with more than two possible states, the optimal strategy in minimum-error comparison is that one should infer the two systems are in different states without any measurement, implying that the discrimination strategy performs worse than the trivial “no-measurement” strategy. We present a sufficient condition for this phenomenon to happen. For two pure states with equal prior probabilities, we determine the optimal comparison success probability with an error margin, which interpolates the minimum-error and unambiguous comparison. We find that the discrimination strategy is not optimal except for the minimum-error case.

  • Figure
  • Received 23 March 2018

DOI:https://doi.org/10.1103/PhysRevA.97.052323

©2018 American Physical Society

Physics Subject Headings (PhySH)

Quantum Information, Science & Technology

Authors & Affiliations

A. Hayashi, T. Hashimoto, and M. Horibe

  • Department of Applied Physics, University of Fukui, Fukui 910-8507, Japan

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Issue

Vol. 97, Iss. 5 — May 2018

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