Professor John Goold

When considering devices operating at a scale where quantum mechanical laws become important we may ask whether the solid grounds of thermodynamics might be challenged, not only by the lack of a thermodynamic limit, but also by the intrinsic uncertainty synonymous with this domain. It comes as no surprise that there has been a recent concerted effort to understand how the laws of thermodynamics generalize to arbitrary quantum systems both at and away from equilibrium. This effort is known as quantum thermodynamics and its development and application is the subject of this proposal. Specifically I will develop and apply thermodynamic concepts to finite size quantum systems in generically non equilibrium settings. By combining well developed tools of condensed matter physics, quantum information and quantum optics with quantum thermodynamics approaches I plan to model the physics of both single and many-body quantum devices and systems at and far from thermodynamic equilibrium. Specifically the research is focused on the description, development and optimization of stochastic quantum engine cycles, developing concepts in quantum thermodynamics to understand the thermodynamic efficiency of quantum information processing and in addition to explore the emergence of thermodynamic behavior from the underlying complex dynamics of many-body systems.The research outlined will enhance our understanding of the fundamental limitations of future technologies, generate the blueprints for a new class of optimized nano-machines, lead to the new design of efficient controls for thermal machines and enhance our understanding of non equilibrium quantum dynamics.

Thermodynamics is a theory with an impressive range of applicability, successfully describing the properties of macroscopic systems ranging from refrigerators in your kitchen to black holes in the universe. With the the industrial and electronic revolutions behind us, we are currently pushing technology towards and beyond the microscopic scale to the border of where quantum mechanical effects prevail. Currently, there is a large interest in the quantum information, quantum optics and statistical mechanics communities surrounding the thermodynamic description of non-equilibrium quantum systems from both a fundamental and applicative view point. Central to this interest is the concept of the quantum thermal machine. These are machines which convert heat to work at the nanoscale level and are expected to play an increasingly central role in emerging quantum technologies. A highly relevant and well studied example of such machines, in the classical and quantum domain, are thermo-electrics. A thermoelectric device is one which converts heat to electrical energy, but is different to other thermal devices- in that it does not have moving parts such as pistons or gears. In thermo-electrics - steady state electrical currents can be made flow in the presence of a thermal gradients and vice versa. This is why they are sometimes known as steady state devices. Despite the progress made in the last years, the efficiency of such devices remains too low to be competitive with other technologies and there is no clear consensus what are the microscopic components which lead to good thermoelectric efficiencies. This research focuses on understanding how the fundamental microscopic features of a material, containing the inevitable ingredients of disorder, interactions and dephasing, could give rise to favourable thermal expectation values which would boost both power and efficiency of a steady state thermal device which uses that material as a working medium.

This research proposal focuses on the open quantum system dynamics of disordered and interacting many- body systems coupled to external baths. The dynamics of systems which contain both disorder and interactions are currently under intense theoretical investigation in condensed matter physics due to the discovery of a new phase of matter known as many-body localization. With the experimental realization of such systems in mind, this proposal addresses an essential issue which is to understand how coupling to external degrees of freedom influences dynamics. These systems are intrinsically complex and lie beyond the unitary closed system paradigm, so the research proposed here contains interdisciplinary methodology beyond the mainstream in condensed matter physics ranging from quantum information to quantum optics. The project has three principal objectives each of which would represent a major contribution to the field: 1. To describe the dynamics of a interacting, disordered many-body systems when coupled to external baths. O 2. To perform a full characterization of spin and energy transport in their non-equilibrium steady state. 3. To explore the system capabilities as steady state thermal machine from a systematic microscopic perspective. This will be the first comprehensive study of the open system phenomenology of disordered interacting many-body systems. It will also allow for the systematic study of energy and spin transport and the exploration of the potential of these systems as steady state thermal machines. In order to successfully carry out the work proposed here, the applicant will build a world class team at Trinity College Dublin. Due to his track record and interdisciplinary background in many-body physics, quantum information and statistical mechanics combined with his personal drive and ambition the applicant is in a formidable position to successfully undertake this task with the platform provided by this ERC Starting Grant.

This is a grant provided by SFI to ERC awardees to help with the grant administration.

The aim of this proposal is to study quantum dynamics in the presence of disorder, and specifically the Anderson and many- body localization transition to a phase where transport and thermalization are absent. Localization in quantum systems has both deep fundamental implications in many different fields and exciting practical applications in quantum technology. In this action the researcher, who is experienced in the statistical physics of quantum disordered systems, will address in a novel and timely way this topic. She aims to improve understanding of it with a three-fold approach: a quantum information experimental effort; new theoretical tools coming from the study of random matrices and the physics of glassy systems; and a joint work with a non-academic entity on numerical methods that use artificial neural networks for the classification of the localized phase. She will perform this work in the perfectly suited environment of the Thermodynamics and Energetics of Quantum Systems research group at Trinity College Dublin.