Beyond Markovian dissipation at the nanoscale : towards finding quantum design rules for bio-organic nanodevices
: Au delà de la dissipation markovienne à l’échelle nanométrique : vers la découverte de règles quantiques pour la conception de nano-dispositifs bio-organiques

  • Thibaut Francois Marie Lacroix

Student thesis: Doctoral Thesis (PhD)


A better understanding of dissipation is crucial for understanding real-world quantum systems. Indeed, all quantum systems experience interactions with an (often) uncontrollable outside environment that can lead to a decay of excited state populations and a loss of quantum coherences. The study of dissipation is timely as the development of next-generation nanoscale quantum technologies is on its way, and the existence of non-trivial quantum effects in biological systems is being seriously investigated. However, descriptions of dissipation in quantum systems are reduced (most of the time) to time-local approaches and (everywhere) to space-local independent environments. These simplifying assumptions do render analytic and numerical calculations possible, yet they get rid of a breadth of physical processes that can alter radically the quantum systems' dynamics. In this thesis, building on a numerically exact tensor networks method, we developed a technique able to handle spatio-temporal correlations between a quantum system and bosonic (i.e. vibrational, electromagnetic, magnons, etc.) environments. With this method we studied the signalling process - a form of information backflow - in quantum systems, and uncovered how it can induce non-trivial dynamics, and be leveraged to populate otherwise inaccessible excited states. We also evidenced the ability of 'non-local' environment reorganisation, induced by system-environment interactions, to radically change the nature of the thermodynamically favoured system ground state. The new phenomenology of physical processes, resulting from considering quantum systems interacting with a common environment, has important consequences for the design of nanodevices as it gives access to new control, sensing and cross-talk mechanisms. In another vein, these results might also give us a new framework to study and interpret (quantum?) effects in the biological realm.
Date of Award29 Nov 2023
Original languageEnglish
Awarding Institution
  • University of St Andrews
SupervisorBrendon William Lovett (Supervisor) & Alex Chin (Supervisor)


  • Quantum physics
  • Open systems
  • Tensor networks
  • Non-Markovian
  • Nanosciences

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