Archive ouverte UNIGE | last documents for author 'Fabien Clivaz'https://archive-ouverte.unige.ch/Latest objects deposited in the Archive ouverte UNIGE for author 'Fabien Clivaz'engOptimal Manipulation of Correlations and Temperature in Quantum Thermodynamicshttps://archive-ouverte.unige.ch/unige:145933https://archive-ouverte.unige.ch/unige:145933This thesis is devoted to the study of two tasks: refrigeration and the creation of correlations. Both of these tasks are investigated within the realm of quantum thermodynamics. Our approach is influenced by that of quantum information but connections with other approaches are desired and emphasized whenever possible.Mon, 07 Dec 2020 15:06:05 +0100Unifying Paradigms of Quantum Refrigeration: A Universal and Attainable Bound on Coolinghttps://archive-ouverte.unige.ch/unige:127281https://archive-ouverte.unige.ch/unige:127281Cooling quantum systems is arguably one of the most important thermodynamic tasks connected to modern quantum technologies and an interesting question from a foundational perspective. It is thus of no surprise that many different theoretical cooling schemes have been proposed, differing in the assumed control paradigm and complexity, and operating either in a single cycle or in steady state limits. Working out bounds on quantum cooling has since been a highly context dependent task with multiple answers, with no general result that holds independent of assumptions. In this letter we derive a universal bound for cooling quantum systems in the limit of infinite cycles (or steady state regimes) that is valid for any control paradigm and machine size. The bound only depends on a single parameter of the refrigerator and is theoretically attainable in all control paradigms. For qubit targets we prove that this bound is achievable in a single cycle and by autonomous machines.Tue, 03 Dec 2019 14:35:05 +0100Unifying paradigms of quantum refrigeration: Fundamental limits of cooling and associated work costshttps://archive-ouverte.unige.ch/unige:127271https://archive-ouverte.unige.ch/unige:127271In classical thermodynamics the work cost of control can typically be neglected. On the contrary, in quantum thermodynamics the cost of control constitutes a fundamental contribution to the total work cost. Here, focusing on quantum refrigeration, we investigate how the level of control determines the fundamental limits to cooling and how much work is expended in the corresponding process. jona{We compare two extremal levels of control. First coherent operations, where the entropy of the resource is left unchanged, and second incoherent operations, where only energy at maximum entropy (i.e. heat) is extracted from the resource. For minimal machines, we find that the lowest achievable temperature and associated work cost depend strongly on the type of control, in both single-cycle and asymptotic regimes. We also extend our analysis to general machines.} Our work provides a unified picture of the different approaches to quantum refrigeration developed in the literature, including algorithmic cooling, autonomous quantum refrigerators, and the resource theory of quantum thermodynamics.Tue, 03 Dec 2019 14:02:54 +0100