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arXiv:2402.16096 · Communications Physics

Memory loss is contagious in open quantum systems

Anael Ben‐Asher, Antonio I. Fernández‐Domínguez, Johannes Feist

Published Oct 10, 2025• 2 citations
arXivHTMLPDF

Abstract

Markovian (memoryless) system-bath interactions play a fundamental role across physics, chemistry, and biological systems. Typically, such memoryless behavior arises from the bath’s properties. Here, we reveal a distinct mechanism: when a system interacts with both a Markovian and a non-Markovian bath, losses induced by the former suppress memory effects from the latter, making the interaction appear more Markovian. This effect leads to a direct interplay between independent baths, where Markovianity becomes “contagious,” transferring between them via their common system. To describe this phenomenon, we introduce a Bloch-Redfield-inspired approach that accurately captures how a lossy system, governed by a Lindblad master equation, interacts with a non-Markovian bath. Beyond offering new insights into dissipative dynamics, this framework provides a computationally efficient alternative for modeling complex system-bath interactions across a broad range of scientific disciplines. Markovianity, where system-bath interactions have no memory, is central for describing many physical processes and serves as a useful approximation that reduces complexity. Here, the authors show that Markovianity can arise not only from the bath’s properties, but also from dissipation induced in a system coupled to a non-Markovian bath by its coupling to an additional Markovian bath.

DOI
10.1038/s42005-025-02310-y

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Markovian (memoryless) system-bath interactions play a fundamental role across physics, chemistry, and biological systems. Typically, such memoryless behavior arises from the bath’s properties. Here, we reveal a distinct mechanism: when a system interacts with both a Markovian and a non-Markovian bath, losses induced by the former suppress memory effects from the latter, making the interaction appear more Markovian. This effect leads to a direct interplay between independent baths, where Markovianity becomes “contagious,” transferring between them via their common system. To describe this phenomenon, we introduce a Bloch-Redfield-inspired approach that accurately captures how a lossy system, governed by a Lindblad master equation, interacts with a non-Markovian bath. Beyond offering new insights into dissipative dynamics, this framework provides a computationally efficient alternative for modeling complex system-bath interactions across a broad range of scientific disciplines. Markovianity, where system-bath interactions have no memory, is central for describing many physical processes and serves as a useful approximation that reduces complexity. Here, the authors show that Markovianity can arise not only from the bath’s properties, but also from dissipation induced in a system coupled to a non-Markovian bath by its coupling to an additional Markovian bath.
Abstract Non-Markovian dynamics is central to quantum information processing, as memory effects strongly influence coherence preservation, metrology, and communication. In this work, we investigate the role of stochastic system–bath couplings in shaping non-Markovian behavior of open quantum systems, using the central spin model within a time-convolutionless master equation framework. We show that the character of the reduced dynamics depends jointly on the intrinsic memory of the environment and on the structure of the system–environment interaction. In certain regimes, the dynamics simplify to pure dephasing, while in general both amplitude damping and dephasing contribute to the evolution. By employing two complementary measures: the Quantum Fisher Information (QFI) flow and the Breuer–Laine–Piilo (BLP) measure, we demonstrate that QFI flow may fail to witness memory effects in weak-coupling and near-resonant regimes, whereas the BLP measure still detects information backflow. Furthermore, external modulation of the interaction kernel produces qualitatively richer behavior, including irregular and frequency-dependent revivals of non-Markovianity. These results clarify the physical origin of memory effects, highlight the limitations of single-witness approaches, and suggest that stochasticity and modulation can be harnessed to engineer robust, noise-resilient quantum technologies.
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We present a theoretical framework to tackle quantum non-Markovian dynamics based on a microscopic collision model (CM), where the bath consists of a large collection of initially uncorrelated ancillas. Unlike standard memoryless CMs, we endow the bath with memory by introducing interancillary collisions between next system-ancilla interactions. Our model interpolates between a fully Markovian dynamics and the continuous interaction of the system with a single ancilla, i.e., a strongly non-Markovian process. We show that in the continuous limit one can derive a general master equation, which, while keeping such features, is guaranteed to describe an unconditionally completely positive and trace-preserving dynamics. We apply our theory to an atom in a dissipative cavity for a Lorentzian spectral density of bath modes, a dynamics which can be exactly solved. The predicted evolution shows a significant improvement in approaching the exact solution with respect to two well-known memory-kernel master equations.
Quantum simulation of open quantum systems offers a pathway towards better understanding various non-equilibrium physics that would otherwise be challenging to study. While most open quantum systems studied are modeled as being memory-less (obeying the Markov approximation), real baths generally are influenced by the system-bath interaction, and some systems existing in structured non-Markovian environments can display novel behavior as a result. Here we utilize a trapped ion quantum simulator to simulate a single spin-1/21/21/2 driven-dissipative system with a non-Markovian dissipation channel, and experimentally compare steady-states to those from an analogous Markovian bath. We observe that a non-Markovian dissipative channel can shift the steady-state even for a single qubit, to a regime inaccessible for Markovian dissipation. The techniques used here are compatible with many-body extensions of the model, which can not be simulated efficiently on a classical computer in general. Our work also opens up new possibilities in quantum reservoir engineering beyond the Markovian regime.