Anja Seegebrecht

Coarse-graining Methods and Thermodynamics of Open Quantum
Systems – Micromaser

Thermodynamics was developed as a phenomenological theory to describe macroscopic processes in terms of a few quantities such as temperature. With the realization of ever smaller systems not only thermal fluctuations govern the dynamics but also quantum effects have to be taken into account in the theoretical description. This motivates an extension of thermodynamics towards quantum thermodynamics [1].
Especially the definition of concepts like work [2–4] and entropy (production) [5–7] is still debated and a concise extension of fluctuation theorems to open quantum systems far from equilibrium is challenging. Such problems will be considered in the context of the one atom maser as a model system, where a beam of two-level atoms interacts with a single cavity mode [8].
Ideas of classical non-equilibrium coarse-graining methods offer a possible pathway to systematic derivation of effective macroscopic descriptions from microscopic dynamics [9].

References
1. Millen, J. et al. Perspective on quantum thermodynamics. New Journal of Physics 18, 011002. (2016).
2. Gemmer, J. et al. Quantum Thermodynamics: Emergence of Thermodynamic Behavior Within Composite Quantum Systems 2nd ed. isbn: 978-3-540-70509-3 (Springer, Berlin, Heidelberg, 2009).
3. Campisi, M. et al. Colloquium: Quantum fluctuation relations: Foundations and applications. Rev. Mod. Phys. 83, 771–791. (3 July 2011).
4. Balian, R. From Microphysics to Macrophysics (Springer, 1991).
5. Solano-Carrillo, E. et al. Theory of entropy production in quantum many-body systems. Phys. Rev. B 93, 224305. (22 2016).
6. Breuer, H.-P. Quantum jumps and entropy production. Phys. Rev. A 68, 032105. (3 2003).
7. Esposito, M. et al. Entropy production as correlation between system and reservoir. New Journal of Physics 12, 013013. (Jan. 2010).
8. Englert, B.-G. Elements of Micromaser Physics 2002.
9. Schilling, T. Coarse-Grained Modelling Out of Equilibrium 2021.
10. Dirkmann, M. Thermodynamics of the Micromaser MA thesis (Albert-Ludwigs-Universität Freiburg im Breisgau, 2019).

Supervisor: Tanja Schilling