Strict hierarchy between parallel, sequential, and indefinite-causal-order strategies for channel discrimination
Quantum Physics
2021-11-24 v2
Abstract
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.
Cite
@article{arxiv.2011.08300,
title = {Strict hierarchy between parallel, sequential, and indefinite-causal-order strategies for channel discrimination},
author = {Jessica Bavaresco and Mio Murao and Marco Túlio Quintino},
journal= {arXiv preprint arXiv:2011.08300},
year = {2021}
}
Comments
6 + 13 pages, 4 figures. Code available at https://github.com/mtcq/channel_discrimination