Minimal manifestation of Kerr-mediated frequency combs in superconducting circuits

In this presentation, we present an experimental realization of a coherently driven, Kerr-mediated, microwave frequency comb. Our device consists of two superconducting modes: a mode with modest Kerr-nonlinearity strongly coupled to a second, linear mode. We explore the phase space of the two-mode system, including the transition from a stable regime to a region where the system settles into limit cycle dynamics exhibiting a frequency comb [1]. Temporal correlation function measurements reveal it is highly coherent, with a phase coherence as 30 μs, significantly exceeding the bare mode decay times of 15 ns. Additionally, in contrast to standard optical comb devices the comb’s coherence is strongly influenced by quantum fluctuations due to the intrinsic Kerr nonlinearity of the system. This result is further supported by excellent agreement of comb coherence and dynamics measurements with a microscopic quantum theory of the two-mode system. The combination of strong and engineerable interactions in our system makes it a promising platform for engineering spectrally broader and denser microwave frequency combs, and also a good testbed for studying complex quantum nonlinear dynamics.

[1] S. Khan, H. E. Türeci, Phys. Rev. Lett. 120, 153601 (2018)