Freiburg 2019 – wissenschaftliches Programm

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FM: Fall Meeting

FM 83: Poster: Enabling Technologies Sources of Quantum States of Light

FM 83.2: Poster

Donnerstag, 26. September 2019, 16:30–18:30, Tents

Injection locking and synchronization in Josephson circuits — •Lukas Danner, Ciprian Padurariu, Björn Kubala, and Joachim Ankerhold — Institute for Complex Quantum Systems and IQST, Ulm University, 89069 Ulm, Germany

Motivated by recent progress in realizing sources of quantum states of microwave light using Josephson circuits, we explore reducing the emission linewidth to potentially enable measurements of microwave quantum entanglement [1]. We employ the phenomena of injection locking and synchronization that stabilize the phase of emitted radiation against electrical noises [2].

We study injection locking of a single Josephson cavity and show that the low frequency environment plays an essential role in frequency pulling and locking. We model a realistic circuit that includes the resistive part of the impedance and calculate the radiation spectrum finding good agreement with recent experiments.

We further study the synchronization of two (nearly) degenerate Josephson cavities. At low driving amplitudes we find a competition between squeezing and entanglement production. The steady state Wigner density indicates squeezing along an axis that can be rotated by tuning the ratio of the cavity loss rates. Building on these results, we argue the emergence of non-linear response and synchronization as the driving power is increased.

[1] M. Westig et al., Phys. Rev. Lett. 119, 137001 (2017).

[2] M.C. Cassidy et al., Science 355, 939 (2017).