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arXiv · 2604.26647

Nonclassical traits in multi-copy state discrimination

Tim Achenbach·Leevi Leppäjärvi·Hanwool Lee·Teiko Heinosaari
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Abstract

Quantum state discrimination is a fundamental information processing task that serves as a key component in many applications while also carrying foundational significance. In this work, we consider minimum error discrimination of multi-copy states, where instead of preparing a single system we assume that multiple instances of the same state are prepared. Now the discrimination allows for measurements from multiple parties with different measurement strategies varying from global measurement strategy to ones restricted to different forms of local operations and classical communication strategies. By comparing the average success probabilities in quantum and classical cases, we find a qubit strategy that outperforms all the bit strategies. On the other hand, we show that the classical measurement strategy does not give benefit in qubit over bit. However, we find that there are other (qu)bit-like operational theories which can outperform the best qubit strategies even with a classical measurement strategy and we are able to identify instances of different theories where different measurement strategies are optimal. In this way, we are able to find instances of nonlocality without entanglement as well as provide general bounds for bit-like operational theories.

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Tim Achenbach, Leevi Leppäjärvi, Hanwool Lee, Teiko Heinosaari. 2026-04-29. Nonclassical traits in multi-copy state discrimination. https://arxiv.org/abs/2604.26647

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