Coherent Thermal Machines: Fluctuations and Performance

Loading...
Thumbnail Image
Journal Title
Journal ISSN
Volume Title
School of Science | Doctoral thesis (article-based) | Defence date: 2020-11-11
Date
2020
Major/Subject
Mcode
Degree programme
Language
en
Pages
68 + app. 92
Series
Aalto University publication series DOCTORAL DISSERTATIONS, 164/2020
Abstract
Quantum Engineering is a rapidly evolving discipline, promising the development of groundbreaking new technologies. To overcome the challenges posed by the nanoscopic scales and ultra-cold temperatures that are required for the implementation of quantum devices, understanding the thermodynamic interaction of these devices with their environment is important. Improving our knowledge of the laws of quantum thermodynamics enables engineers to exert better control over quantum circuits and it paves the way for more effective thermal management solutions on the nanoscale. In this dissertation, we focus on the study of thermal machines such as heat engines or refrigerators. These devices have recently been miniaturized in labs to the point where quantum effects can influence their performance. Due to the well-known advantages of quantum over conventional computers, it is natural to wonder whether coherence effects might be able to give a similar performance enhancement to thermal machines. Here, we approach this question on three different levels. First, we study the theory of periodically controlled open quantum systems in order to better understand the mathematical foundations of reciprocating thermal devices. Second, we investigate transport phenomena in open quantum systems, enabling us to discuss the fluctuations of thermodynamic currents and how they affect the performance of thermal machines. Third, and finally, we examine whether the performance of quantum heat engines is subject to universal bounds and how these bounds change in different operation regimes. The results of this thesis shed light on the optimal design of quantum devices, which will soon be ready for experimental implementation and investigation. Overall, we find that coherence leads to quantum friction, that is, to an increase in thermodynamic irreversibility with associated performance losses. In the adiabatic weak-coupling regime, these losses outweigh the benefits stemming from the increased number of degrees of freedom that are accessible in quantum setups. In other words, we find that coherence should generally be kept as small as possible in order to optimize the performance of nanoscale thermal machines in this regime. A promising direction for future investigations is to explore the effects of strong coupling and fast driving, where quantum advantages may be achievable.
Description
A doctoral dissertation completed for the degree of Doctor of Science (Technology) to be defended, with the permission of the Aalto University School of Science, via remote connection on 11 November 2020 at 13:00. Remote connection link: https://aalto.zoom.us/j/68824530640
Supervising professor
Flindt, Christian Prof., Aalto University, Department of Applied Physics, Finland
Keywords
statistical physics, quantum physics, fluctuations and noise, thermal machines, open quantum systems, counting statistics, optimization problems
Other note
Parts
  • [Publication 1]: P. Menczel and K. Brandner. Limit cycles in periodically driven open quantum systems. J. Phys. A: Math. Theor. 52 43LT01, September 2019.
    DOI: 10.1088/1751-8121/ab435a View at publisher
  • [Publication 2]: F. Brange, P. Menczel, and C. Flindt. Photon counting statistics of a microwave cavity. Phys. Rev. B 99, 085418, February 2019.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-201903112201
    DOI: 10.1103/PhysRevB.99.085418 View at publisher
  • [Publication 3]: S. Singh, P. Menczel, D. S. Golubev, I. M. Khaymovich, J. T. Peltonen, C. Flindt, K. Saito, É. Roldán, and J. P. Pekola. Universal First-Passage-Time Distribution of Non-Gaussian Currents. Phys. Rev. Lett. 122, 230602, June 2019.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-201907304536
    DOI: 10.1103/PhysRevLett.122.230602 View at publisher
  • [Publication 4]: P. Menczel, C. Flindt, and K. Brandner. Quantum jump approach to microscopic heat engines. Phys. Rev. Research 2, 033449, September 2020.
    DOI: 10.1103/PhysRevResearch.2.033449 View at publisher
  • [Publication 5]: P. Menczel, C. Flindt, and K. Brandner. Thermodynamics of cyclic quantum amplifiers. Phys. Rev. A 101, 052106, May 2020.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202006254033
    DOI: 10.1103/PhysRevA.101.052106 View at publisher
  • [Publication 6]: P. Menczel, T. Pyhäranta, C. Flindt, and K. Brandner. Two-stroke optimization scheme for mesoscopic refrigerators. Phys. Rev. B 99, 224306, une 2019.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-201907304446
    DOI: 10.1103/PhysRevB.99.224306 View at publisher
Citation