Estimation of correlations and non-separability in quantum channels via unitarity benchmarking
As quantum technologies and devices scale up, it becomes increasingly important to characterise the behaviour of noise. The presence of unwanted correlations can have a detrimental effect on how errors accumulate throughout a circuit. In this work, we introduce new operational measures to quantify correlations between subsystems in quantum processes and show they satisfy a range of physically meaningful properties. In particular, they allow detection of non-classical features in processes. A key aspect is that we develop efficient benchmarking protocols to estimate these correlation measures in effective noise channels. Specific applications could be found in quantification of cross-talk and coherent errors. The implications of detecting and quantifying noise correlations are twofold: it impacts Noisy Intermediate-Scale Quantum devices by improving circuit fidelities and informing error mitigation but also provides necessary tools to test physical assumptions of quantum error correction.
Matthew Girling, Cristina Cırstoiu and David Jennings