Quantum non-Markovianity elusive to interventions

TL;DR

This paper demonstrates that certain non-Markovian quantum systems can have long-term memory effects that are completely undetectable through interventions, raising questions about the fundamental assessibility of non-Markovianity.

Contribution

It introduces a method to engineer non-Markovian quantum systems with hidden memory effects that are undetectable by any intervention up to large times.

Findings

Non-Markovianity can be engineered to be completely non-detectable by interventions.

Long-term memory effects can exist without short-term detectable signatures.

Non-Markovian effects may emerge at arbitrarily large times, challenging current assessment methods.

Abstract

The non-Markovian nature of open quantum dynamics lies in the structure of the multitime correlations, which are accessible by means of interventions. Here, by examining multitime correlations, we show that it is possible to engineer non-Markovian systems with only long-term memory but seemingly no short-term memory, so that their non-Markovianity is completely non-detectable by any interventions up to an arbitrarily large time. Our results raise the question about the assessibility of non-Markovianity: in principle, non-Markovian effects that are perfectly elusive to interventions may emerge at much later times.