Regensburg 2025 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 50: Superconducting Electronics: SQUIDs, Qubits, Circuit QED II

TT 50.9: Talk

Thursday, March 20, 2025, 17:15–17:30, H36

Dispersive and dissipative interactions in niobium-based photon-pressure circuits — •Zisu Emily Guo, Mohamad el Kazouini, Janis Peter, Kevin Uhl, Dieter Koelle, Reinhold Kleiner, and Daniel Bothner — Physikalisches Institut, Center for Quantum Science (CQ) and LISA⁺, Universität Tübingen

Photon-pressure (PP) circuits consist of one superconducting microwave resonator in the GHz range and one low-frequency (LF) circuit in the MHz range and are the cQED analog of cavity optomechanics. The LC circuits in a PP device are coupled to each other via a superconducting quantum interference device (SQUID), emulating an optomechanical interaction and offering access to sensing and control of MHz photons with potential applications in axion dark matter detection and quantum information technologies. Here, we report the realization of niobium- and nanoconstriction-based photon-pressure circuits operated in the thermal regime. In contrast to previous implementations, we observe in our experiments both dispersive and dissipative PP coupling - meaning that not only frequency but also linewidth modulations contribute significantly to the overall interaction. We investigate dynamical backaction effects with these dissipative contributions as well as sideband-cooling of the LF mode, measured through photon-pressure-induced transparency and output noise thermometry, respectively. Additionally, our circuit design with on-chip flux-bias line allows the parametric modulation of the LF mode resonance frequency, which may be used for LF squeezing and (phase-sensitive) amplification of the PP coupling rate.

Keywords: cQED; microwave circuits; SQUID; sideband-cooling; parametric amplification