## Simplifying multi-level thermal machines using virtual qubits

**Speaker:**Ayaka Usui, OIST

**When:**October 28, 2020 (Wed), 04:00PM to 05:00PM (add to my calendar)

*This event is part of the Biophysics/Condensed Matter Seminar Series. *

Investigating the control of thermal machines in the quantum regime allows one to explore the fundamental limits of thermodynamic tasks. To study such processes, it is usual to consider a few quantum-mechanical degrees of freedom interacting with a large environment, which one does not have detailed control over. Higher-dimensional machines are harder to simulate exactly, and hence much of the focus is on models that are simple enough to be treatable by master equations, such as a few qubits. Expanding the target system to multi-level systems beyond qubits is a challenge. In this work [1], we address this problem for three-level systems, as well as arbitrary-level systems, coherently interacting with several virtual qubits in the context of reset master equations. We investigate the steady-state solution for three-level systems coupled to virtual qubits and identify properties of multi-level thermal machines. In this talk, I will start with the introduction of the history of thermodynamic tasks in the quantum regime and virtual qubits before presenting the findings of this work. I will then propose a method to enhance the performance of the paradigmatic three-level maser/laser to show the advantages of the results obtained from this work.

[1] A. Usui, W. Niedenzu, and M. Huber, Simplifying multi-level thermal machines using virtual qubits, arXiv:2009.03832.

zoom link: https://bostonu.zoom.us/j/97975652026?pwd=cnhiQ1V1d29CZ1JpSVJWWHQ5WEZaUT09