Year: 2026
Type: preprint
Abstract: The search for wave-like dark matter using microwave cavity haloscopes is constrained by the Standard Quantum Limit, which dictates that phase-preserving linear amplification results in a minimum of one quantum of total system noise for a narrow-band signal. We demonstrate that this limit is effectively halved for a non-monochromatic axion signal coupled to a high-$Q$ cavity. By operating a Josephson Parametric Amplifier such that the cavity resonance is centered exactly at the half-pump frequency, the axion signal symmetrically populates both the signal and idler bands. Through quadrature analysis of the homodyne readout, we show that the incoherent sum of these mirrored spectral components doubles the measured signal power while the vacuum noise remains constant. This operation yields an effective noise limit of 0.5 quanta per frequency bin, translating to an overall effective limit of $1/\sqrt{2}$ quanta after optimal matched filtering.
Source: arXiv (Cornell University)
Authors: Jeong, Junu, Silva-Feaver, Max
Institutions: Stockholm University, AlbaNova, Yale University
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7207655888