• Open Access

Exact Dynamics of Nonadditive Environments in Non-Markovian Open Quantum Systems

Dominic Gribben, Dominic M. Rouse, Jake Iles-Smith, Aidan Strathearn, Henry Maguire, Peter Kirton, Ahsan Nazir, Erik M. Gauger, and Brendon W. Lovett
PRX Quantum 3, 010321 – Published 7 February 2022

Abstract

When a quantum system couples strongly to multiple baths, then it is generally no longer possible to describe the resulting system dynamics by simply adding the individual effects of each bath. However, capturing such multibath system dynamics typically requires approximations that can obscure some of the nonadditive effects. Here we present a numerically exact and efficient technique for tackling this problem that builds on the time-evolving matrix product operator (TEMPO) representation. We test the method by applying it to a simple model system that exhibits nonadditive behavior: a two-level dipole coupled to both a vibrational and an optical bath. Although not directly coupled, there is an effective interaction between the baths mediated by the system that can lead to population inversion in the matter system when the vibrational coupling is strong. We benchmark and validate multibath TEMPO against two approximate methods—one based on a polaron transformation, the other on an identification of a reaction coordinate—before exploring the regime of simultaneously strong vibrational and optical coupling where the approximate techniques break down. Here we uncover a new regime where the quantum Zeno effect leads to a fully mixed state of the electronic system.

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  • Received 17 September 2021
  • Revised 21 December 2021
  • Accepted 7 January 2022

DOI:https://doi.org/10.1103/PRXQuantum.3.010321

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Quantum Information, Science & TechnologyCondensed Matter, Materials & Applied PhysicsGeneral Physics

Authors & Affiliations

Dominic Gribben1,†, Dominic M. Rouse1,†, Jake Iles-Smith2,3,†, Aidan Strathearn4, Henry Maguire2, Peter Kirton5, Ahsan Nazir2, Erik M. Gauger6, and Brendon W. Lovett1,*

  • 1SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, United Kingdom
  • 2Department of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
  • 3Department of Electrical and Electronic Engineering, The University of Manchester, Sackville Street Building, Manchester M1 3BB, United Kingdom
  • 4School of Mathematics and Physics, The University of Queensland, St Lucia, Queensland 4072, Australia
  • 5Department of Physics and SUPA, University of Strathclyde, Glasgow G4 0NG, United Kingdom
  • 6SUPA, Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom

  • *bwl4@st-andrews.ac.uk
  • These authors contributed equally.

Popular Summary

Quantum systems that can be measured in the laboratory are never truly isolated. They interact with their surroundings, and this affects their behaviour. In many situations, this interaction is relatively strong - for example in the solid-state systems that might be used to build a quantum computer. Moreover, there is often more than one kind of environment, each consisting of a different collection of particles, and each of which changes the behaviour of the system in a different way. In this paper, an exact numerical technique is developed, able to capture their combined effect.

Importantly, these multiple environments cannot be treated separately - i.e. the changes in the system dynamics are not simply additive. Nor can they be treated through a direct solution of the Schroedinger equation: the number of particles is too large for any computer to represent directly. Rather, we develop a way of capturing only the most relevant information, through the use of tensor network techniques. In this way, we are able to obtain exact predictions for general models consisting of a quantum system and multiple environments.

The technique is illustrated by studying a two-level atom coupled to both photons (light particles) and phonons (lattice vibrations) and is able to look at what happens when the coupling to both environments is strong. This method paves the way for gaining a deeper insight into the non-equilibrium physics that naturally emerge in open quantum systems, and for understanding the behaviour of quantum devices being developed for future technologies.

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Vol. 3, Iss. 1 — February - April 2022

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It is not necessary to obtain permission to reuse this article or its components as it is available under the terms of the Creative Commons Attribution 4.0 International license. This license permits unrestricted use, distribution, and reproduction in any medium, provided attribution to the author(s) and the published article's title, journal citation, and DOI are maintained. Please note that some figures may have been included with permission from other third parties. It is your responsibility to obtain the proper permission from the rights holder directly for these figures.

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