Regensburg 2025 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 47: Fluctuations, Noise and Other Transport Topics (joint session TT/DY)

TT 47.4: Talk

Thursday, March 20, 2025, 15:45–16:00, H31

Colored noise Langevin equation for photon counting — •Steven Kim and Fabian Hassler — Institute for Quantum Information, RWTH Aachen, Germany

For open quantum systems, obtaining the photon counting statistics of the emitted radiation is central to obtain insights into phenomena such as entanglement and correlations, in particular super- and anti-bunching. Typically, these systems are described by a Lindblad master equation, which allows the counting statistics to be derived from normal-ordered number operators. However, the Lindblad equation relies on the rotating wave approximation (RWA), which assumes that the dissipation rate is much smaller than the characteristic photon frequency. While this requirement is always fulfilled at optical frequencies, microwave cavities can have broader linewidths, making the RWA inaccurate. Alternatively, such systems can be effectively described by an equivalent Langevin equation with correlated (colored) noise, which bypasses the need for the RWA. In this work, we derive the photon counting statistics directly from the Langevin equation, providing a broader framework for understanding photon emission in open quantum systems.

Keywords: Photon counting; Open quantum systems; Correlated noise; Microwave cavity