Strict hierarchy between parallel, sequential, and indefinite-causal-order strategies for channel discrimination
Seminar author:Jessica Bavaresco
Event date and time:05/06/2021 04:00:pm
Event location:https://us02web.zoom.us/j/82048989218?pwd=aW0rYjA2L3dZd3ZQcGJ3L1o2NUUzQT09
Event contact:
We will discuss a tester formalism for the task of minimum-error channel discrimination that encompasses both standard parallel and sequential strategies and indefinite-causal-order strategies. We start by applying it to general channels, and discover an instance of a discrimination task of two qubit-qubit channels, an amplitude-damping and a bit-flip channel, for which a sequential strategy outperforms any parallel strategy. We then also show that two classes of strategies evolving indefinite causal order outperform causally ordered ones in the same task, forming a strict hierarchy of performance among all four strategies. Our proof technique employs a general method of computer-assisted proofs. Finally, we turn our attention to the discrimination of unitary channels to also find examples of the advantage of sequential and general strategies in this scenario.
Based on: arXiv:2011.08300 [quant-