Progress towards implementing GC-enhancement in an axion search

Dynamically coupling a science cavity with an auxiliary readout resonator via simultaneous frequency-conversion (C) and entanglement (gain, G) processes is expected to yield an advantage in weak signal searches where the frequency of the signal tone is a priori unknown [1]. When applied to a demonstration experiment designed to mimic an axion search in which synthetic axion signals were injected with powers far below the level of vacuum fluctuations, the GC-enhanced technique yielded a 5.6-fold scan rate enhancement relative to an equivalent search at the quantum limit. Nevertheless, there are several technical challenges to be overcome before the technique can be applied to a real axion search. In particular, higher-order parametric processes such as single mode squeezing that limit the achievable interaction rates need to be regulated and a transmission line must be introduced to physically separate the superconducting readout circuitry from the large magnetic field that will surround the axion-sensitive science cavity. Here, we present progress towards overcoming these challenges and applying the technique to a real axion search.

[1] K. Wurtz et al. A cavity entanglement and state swapping method to accelerate the search for axion dark matter. arxiv:2107.04147 (2021)