Bandwidth and visibility improvement in detection of a weak signal using mode entanglement and swapping

TL;DR

This paper demonstrates a quantum-enhanced sensing technique that significantly improves the detection speed of weak signals in cavity-based axion searches by increasing bandwidth and visibility through mode entanglement and swapping.

Contribution

It introduces a novel method combining mode entanglement and swapping to enhance detection bandwidth and visibility in quantum sensing for axion-like signals.

Findings

Achieved a 5.6-fold acceleration in detection speed.

Enhanced scan rate by dynamically coupling modes with balanced interactions.

Demonstrated up to an 8-fold acceleration with fractional imbalance.

Abstract

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.