Estimation of correlations and non-separability in quantum channels via
unitarity benchmarking
unitarity benchmarking
File(s)
Published version
Author(s)
Girling, Matthew
Cirstoiu, Cristina
Jennings, David
Type
Journal Article
Abstract
The ability to transfer quantum information between systems is a fundamental component of quantum technologies and leads to correlations within the global quantum process. However, correlation structures in quantum channels are less studied than those in quantum states. Motivated by recent techniques in randomized benchmarking, we develop a range of results for efficient estimation of correlations within a bipartite quantum channel. We introduce subunitarity measures that are invariant under local changes of basis, generalize the unitarity of a channel, and allow for the analysis of quantum information exchange within channels. Using these, we show that unitarity is monogamous, and we provide an information-disturbance relation. We then define a notion of correlated unitarity that quantifies the correlations within a given channel. Crucially, we show that this measure is strictly bounded on the set of separable channels and therefore provides a witness of nonseparability. Finally, we describe how such measures for effective noise channels can be efficiently estimated within different randomized benchmarking protocols. We find that the correlated unitarity can be estimated in a SPAM-robust manner for any separable quantum channel, and we show that a benchmarking/tomography protocol with mid-circuit resets can reliably witness nonseparability for sufficiently small reset errors. The tools we develop provide information beyond that obtained via simultaneous randomized benchmarking and so could find application in the analysis of cross-talk errors in quantum devices.
Date Issued
2022-04-15
Date Acceptance
2022-02-25
Citation
Physical Review Research, 2022, 4
ISSN
2643-1564
Publisher
American Physical Society
Journal / Book Title
Physical Review Research
Volume
4
Copyright Statement
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
License URL
Identifier
http://arxiv.org/abs/2104.04352v2
Subjects
quant-ph
quant-ph
Notes
38 pages, 5 figures
Publication Status
Published