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Similar talk presented at:
- Chapman University, group of Prof. Prof. Matthew Leifer (Orange, USA, 2021)
- Ulm University, group of Prof. Martin Plenio (Ulm, Germany, 2021)
- YQIS 2021 - VI International Conference for Young Quantum Information Scientists (Michigan, USA, 2021)
References
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Strict Hierarchy between Parallel, Sequential, and Indefinite-Causal-Order Strategies for Channel Discrimination
Jessica Bavaresco, Mio Murao, Marco Túlio Quintino
Physical Review Letters 127, 200504 (2021)
We present an instance of a task of minimum-error discrimination of two qubit-qubit quantum channels for which a sequential strategy outperforms any parallel strategy. We then establish two new classes of strategies for channel discrimination that involve indefinite causal order and show that there exists a strict hierarchy among the performance of all four strategies. Our proof technique employs a general method of computer-assisted proofs. We also provide a systematic method for finding pairs of channels that showcase this phenomenon, demonstrating that the hierarchy between strategies is not exclusive to our main example.
