Regensburg 2022 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 31: Superconducting Electronics and Cryogenics: Poster Session

TT 31.4: Poster

Donnerstag, 8. September 2022, 15:00–18:00, P1

Characterization of Josephson photonics devices as microwave sources for a quantum radar — •Lukas Danner^{1, 2}, Ciprian Padurariu², Joachim Ankerhold², and Björn Kubala^{1, 2} — ¹Institute for Quantum Technologies, German Aerospace Center (DLR), Ulm, Germany — ²ICQ and IQST, Ulm University, Ulm, Germany

In Josephson photonics devices, microwave radiation is created by inelastic Cooper pair tunneling across a dc-biased Josephson junction connected in-series with a microwave resonator [1]. Various resonances are accessed by tuning the dc-voltage, where, e.g., each tunneling Cooper pair creates one, two or three photonic excitations in the resonator. If excitations are created in two different resonators, the device could be used in a quantum radar which exploits the quantum correlations of the photons [2]. The source can be characterized by the steady-state Wigner density of the cavities, showing e.g. two-mode squeezing or other phase-space symmetries for multi-photon creation. Wigner-state tomography is expensive and in Josephson photonics devices especially challenging due to lacking phase stability. Therefore, we propose an alternative approximative characterization scheme which requires measuring only a few expectation values. A different way of dealing with the instability of the phase-space angle by a locking mechanism [3] is discussed in the contribution of F. Höhe.

[1] M. Hofheinz et al., Phys. Rev. Lett. 106, 217005 (2011)

[2] A. Peugeot et al., Phys. Rev. X 11, 031008 (2021)

[3] L. Danner et al., Phys. Rev. B 104, 054517 (2021)