Quantum fluctuations constitute the primary noise barrier limiting cavity-based axion dark matter searches. In an experiment designed to mimic a real axion search, we employ a quantum-enhanced sensing technique to detect a synthetic axion-like microwave tone at an unknown frequency weakly coupled to a resonator, demonstrating a factor of 5.6 acceleration relative to a quantum-limited search for the same tone. The acceleration comes from increases to both the visibility bandwidth and the peak visibility of a detector. This speedup is achieved by dynamically coupling the resonator mode to a second (readout) mode with balanced swapping and two-mode squeezing interactions. A small fractional imbalance between the two interaction rates yields further scan rate enhancement and we demonstrate that an 8-fold acceleration can be achieved.
@article{arxiv.2211.10403,
title = {Bandwidth and visibility improvement in detection of a weak signal using mode entanglement and swapping},
author = {Yue Jiang and Elizabeth P. Ruddy and Kyle O. Quinlan and Maxime Malnou and Nicholas E. Frattini and Konrad W. Lehnert},
journal= {arXiv preprint arXiv:2211.10403},
year = {2023}
}