# Sequential state discrimination with quantum correlation

## TL;DR

This paper investigates sequential unambiguous state discrimination (SSD) of two quantum states with arbitrary prior probabilities, highlighting the roles of quantum discord over entanglement and comparing different strategies including probabilistic cloning.

## Contribution

It introduces a detailed analysis of SSD with arbitrary priors, emphasizing the importance of quantum discord and the superiority of probabilistic cloning in certain scenarios.

## Key findings

- Probabilistic cloning outperforms other strategies when at least one party succeeds.
- Quantum discord, not entanglement, is essential for SSD.
- Prior probability imbalance affects quantum discord distribution.

## Abstract

The sequential unambiguous state discrimination (SSD) of two states prepared in arbitrary prior probabilities is studied, and compared with three strategies that allow classical communication. The deviation from equal probabilities contributes to the success in all the tasks considered. When one considers at least one of the parties succeeds, the protocol with probabilistic cloning is superior to others, which is not observed in the special case with equal prior probabilities. We also investigate the roles of quantum correlations in SSD, and show that the procedure requires discords but rejects entanglement. The left and right discords correspond to the part of information extracted by the first observer and the part left to his successor respectively. Their relative difference is extended by the imbalance of prior probabilities.