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TT: Fachverband Tiefe Temperaturen

TT 42: Other Transport Topics

TT 42.7: Vortrag

Mittwoch, 11. März 2026, 11:15–11:30, HSZ/0105

Symmetry breaking in the non-degenerate parametric oscilator — •Jonathan Schluck, Steven Kim, and Fabian Hassler — Institute for Quantum Information, RWTH Aachen University, 52074 Aachen, Germany

Two harmonic oscillators that are parametrically driven at the sum of their natural frequencies exhibit an instability once the driving strength exceeds the damping. Close to and beyond this instability threshold, nonlinearities must be taken into account. As a consequence of the instability, the system develops a separation of time scales, which can be used to derive an effective Liouvillian describing the long-time dynamics. The effective model possesses a U(1)-symmetry akin to that of a laser. Above the transition, a symmetry-broken state with a fixed phase exhibits an extended lifetime, indicating the symmetry breaking. The phase coherence of this state increases with increasing photon number, following the conventional Schawlow-Townes limit. We propose a measure of symmetry breaking that compares the photon lifetime to the dephasing time in the lasing regime.

Keywords: Harmonic oscillator; Parametric drive; Symmetry; Open quantum systems; Quantum Optics