Quantum-state comparison and discrimination
arXiv:1803.09030 · doi:10.1103/PhysRevA.97.052323
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.
8 pages, 1 figure, minor corrections made, final version
References in corpus (8)
- State discrimination with error margin and its locality
- Discrimination with error margin between two states - Case of general occurrence probabilities -
- Optimal bounded-error strategies for projective measurements in non-orthogonal state discrimination
- On the generalization of quantum state comparison
- Unitary-process discrimination with error margin
- Comparison of mixed quantum states
- Optimal unambiguous comparison of two unknown squeezed vacua
- Probability-based comparison of quantum states