Presented at:
- QIP 2021 - 24th Annual Conference on Quantum Information Processing (Munich, Germany, 2021)
- QPL 2021 - 18th International Conference on Quantum Physics and Logic (Gdansk, Poland, 2021)
View or download the poster (PDF)
References
-
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 the strategies is not exclusive to our main example.
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