Filtering crosstalk from bath non-Markovianity via spacetime classical shadows

TL;DR

This paper introduces a method combining non-Markovian quantum process tomography with classical shadows to filter out crosstalk effects and isolate bath-induced non-Markovianity in quantum systems, enabling efficient analysis of spatiotemporal correlations.

Contribution

It presents a novel approach to distinguish bath non-Markovian effects from crosstalk using classical shadows and causal breaks, scalable to large quantum systems.

Findings

Successfully filters crosstalk effects in synthetic data

Efficiently erases multiple neighboring qubits at no extra cost

Probes non-Markovianity from inaccessible environments

Abstract

From an open system perspective non-Markovian effects due to a nearby bath or neighbouring qubits are dynamically equivalent. However, there is a conceptual distinction to account for: neighbouring qubits may be controlled. We combine recent advances in non-Markovian quantum process tomography with the framework of classical shadows to characterise spatiotemporal quantum correlations. Observables here constitute operations applied to the system, where the free operation is the maximally depolarising channel. Using this as a causal break, we systematically erase causal pathways to narrow down the progenitors of temporal correlations. We show that one application of this is to filter out the effects of crosstalk and probe only non-Markovianity from an inaccessible bath. It also provides a lens on spatiotemporally spreading correlated noise throughout a lattice from common environments. We demonstrate both examples on synthetic data. Owing to the scaling of classical shadows, we can erase arbitrarily many neighbouring qubits at no extra cost. Our procedure is thus efficient and amenable to systems even with all-to-all interactions.