Temporal self-similarity of quantum dynamical maps as a concept of memorylessness

TL;DR

This paper introduces a new perspective on quantum non-Markovianity by defining temporal self-similarity of quantum dynamical maps, providing a geometric measure that complements existing divisibility criteria.

Contribution

It formalizes the concept of temporal self-similarity as a weaker form of memory in quantum dynamics and proposes a geometric quantification method.

Findings

Temporal self-similarity deviation indicates non-Markovian effects.

The geometric measure quantifies the degree of memory in quantum maps.

The approach complements divisibility-based criteria for quantum non-Markovianity.

Abstract

The problem of defining quantum non-Markovianity has proven elusive, with various in-equivalent criteria put forth to address it. The concept of CP-indivisibility and the hierarchy of stronger divisibility criteria going up to P-indivisibility, capture a fundamental aspect of memory in quantum non-Markovianity. In practice, however, there can be a memory-like influence associated with divisible channels in the form of weakening, if not reversing, the effects of decoherence. Arguably, such a facet of memory relates to CP-indivisibility as quantum discord relates to entanglement. We concretize this weaker notion of non-Markovianity by identifying it with deviation from ``temporal self-similarity'', the property of a system dynamics whereby the propagator between two intermediate states is independent of the initial time $t_0$. We illustrate this idea through examples, and propose a geometric quantification of temporal self-similarity, and show how our approach complements the divisibility-based criterion of quantum non-Markovianity.