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arXiv · 2305.08150

The effect of thermal photons on exceptional points in coupled resonators

Grzegorz Chimczak·Anna Kowalewska-Kudłaszyk·Ewelina Lange·Karol Bartkiewicz·Jan Peřina Jr
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Abstract

We analyse two quantum systems with hidden parity-time (PT) symmetry: one is an optical device, whereas another is a superconducting microwave-frequency device. To investigate their symmetry, we introduce an equilibrium frame, in which loss and gain terms for a given Hamiltonian are balanced. We show that the non-Hermitian Hamiltonians of both systems can be tuned to reach an exceptional point (EP), i.e., the point in parameter space at which a transition from broken to unbroken hidden PT symmetry takes place. We calculate a degeneracy of a Liouvillian superoperator, which is called the Liouvillian exceptional point (LEP), and show that, in the optical domain, LEP is equivalent to EP obtained from the non-Hermitian Hamiltonian (HEP). We also report breaking the equivalence between LEP and HEP by a non-zero number of thermal photons for the microwave-frequency system.

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Grzegorz Chimczak, Anna Kowalewska-Kudłaszyk, Ewelina Lange, Karol Bartkiewicz, Jan Peřina Jr. 2023-05-14. The effect of thermal photons on exceptional points in coupled resonators. https://doi.org/10.1038/s41598-023-32864-2

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