Effective Sub-Quantum Readout for Non-Monochromatic Axion Signals in High-Q Haloscopes
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/√2 quanta after optimal matched filtering.
Related
- Photon-Counting Readout via Electro-Optic Microwave-to-Optical Transduction for Axion Haloscopes
- Realization of a Primary Irradiance Scale for Solar irradiance Measurements based on a Predictable Quantum Efficient Detector and a Quasi-Monochromatic Portable Tunable Source.
- Design and Modeling of the Charge Readout of a SiMOS Quantum Dot with a Single Electron Transistor and CryoCMOS
- Near-Quantum-Limited Readout for the Princeton Axion Search using a sub-GHz Kinetic Inductance Traveling Wave Parametric Amplifier
- Near-exact Upper Confidence Limits for Axion Haloscopes
BibTeX
@misc{jeong2026effective,
title = {{Effective Sub-Quantum Readout for Non-Monochromatic Axion Signals in High-$Q$ Haloscopes}},
author = {Junu Jeong and Max Silva-Feaver},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.02828},
eprint = {2609.02828},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.02828},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Effective Sub-Quantum Readout for Non-Monochromatic Axion Signals in High-Q Haloscopes
AU - Junu Jeong
AU - Max Silva-Feaver
PY - 2026
DA - 2026/09/02
PB - arXiv
DO - 10.48550/arxiv.2609.02828
UR - https://arxiv.org/abs/2609.02828
AB - 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/√2 quanta after optimal matched filtering.
ER -