Using the Environment to Understand non-Markovian Open Quantum Systems

Tracing out the environmental degrees of freedom is a necessary procedure when simulating open quantum systems. While being an essential step in deriving a tractable master equation it represents a loss of information. In situations where there is strong interplay between the system and environmenta...

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Main Authors: Dominic Gribben, Aidan Strathearn, Gerald E. Fux, Peter Kirton, Brendon W. Lovett
Format: Article
Language:English
Published: Verein zur Förderung des Open Access Publizierens in den Quantenwissenschaften 2022-10-01
Series:Quantum
Online Access:https://quantum-journal.org/papers/q-2022-10-25-847/pdf/
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author Dominic Gribben
Aidan Strathearn
Gerald E. Fux
Peter Kirton
Brendon W. Lovett
author_facet Dominic Gribben
Aidan Strathearn
Gerald E. Fux
Peter Kirton
Brendon W. Lovett
author_sort Dominic Gribben
collection DOAJ
description Tracing out the environmental degrees of freedom is a necessary procedure when simulating open quantum systems. While being an essential step in deriving a tractable master equation it represents a loss of information. In situations where there is strong interplay between the system and environmental degrees of freedom this loss makes understanding the dynamics challenging. These dynamics, when viewed in isolation, have no time-local description: they are non-Markovian and memory effects induce complex features that are difficult to interpret. To address this problem, we here show how to use system correlations, calculated by any method, to infer any correlation function of a Gaussian environment, so long as the coupling between system and environment is linear. This not only allows reconstruction of the full dynamics of both system and environment, but also opens avenues into studying the effect of a system on its environment. In order to obtain accurate bath dynamics, we exploit a numerically exact approach to simulating the system dynamics, which is based on the construction and contraction of a tensor network that represents the process tensor of this open quantum system. Using this we are able to find any system correlation function exactly. To demonstrate the applicability of our method we show how heat moves between different modes of a bosonic bath when coupled to a two-level system that is subject to an off-resonant drive.
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spelling doaj.art-422b01b528b2427484073c467c4bd0712022-12-22T02:36:02ZengVerein zur Förderung des Open Access Publizierens in den QuantenwissenschaftenQuantum2521-327X2022-10-01684710.22331/q-2022-10-25-84710.22331/q-2022-10-25-847Using the Environment to Understand non-Markovian Open Quantum SystemsDominic GribbenAidan StrathearnGerald E. FuxPeter KirtonBrendon W. LovettTracing out the environmental degrees of freedom is a necessary procedure when simulating open quantum systems. While being an essential step in deriving a tractable master equation it represents a loss of information. In situations where there is strong interplay between the system and environmental degrees of freedom this loss makes understanding the dynamics challenging. These dynamics, when viewed in isolation, have no time-local description: they are non-Markovian and memory effects induce complex features that are difficult to interpret. To address this problem, we here show how to use system correlations, calculated by any method, to infer any correlation function of a Gaussian environment, so long as the coupling between system and environment is linear. This not only allows reconstruction of the full dynamics of both system and environment, but also opens avenues into studying the effect of a system on its environment. In order to obtain accurate bath dynamics, we exploit a numerically exact approach to simulating the system dynamics, which is based on the construction and contraction of a tensor network that represents the process tensor of this open quantum system. Using this we are able to find any system correlation function exactly. To demonstrate the applicability of our method we show how heat moves between different modes of a bosonic bath when coupled to a two-level system that is subject to an off-resonant drive.https://quantum-journal.org/papers/q-2022-10-25-847/pdf/
spellingShingle Dominic Gribben
Aidan Strathearn
Gerald E. Fux
Peter Kirton
Brendon W. Lovett
Using the Environment to Understand non-Markovian Open Quantum Systems
Quantum
title Using the Environment to Understand non-Markovian Open Quantum Systems
title_full Using the Environment to Understand non-Markovian Open Quantum Systems
title_fullStr Using the Environment to Understand non-Markovian Open Quantum Systems
title_full_unstemmed Using the Environment to Understand non-Markovian Open Quantum Systems
title_short Using the Environment to Understand non-Markovian Open Quantum Systems
title_sort using the environment to understand non markovian open quantum systems
url https://quantum-journal.org/papers/q-2022-10-25-847/pdf/
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