Quantum-enhanced Search for Galactic Dark Photons Using Cat-State Cavities

Abstract:We present a quantum-enhanced search for the Galactic dark-photon background (GDPB), a relativistic and anisotropic vector field that can be produced by dark-matter decay or annihilation in the Milky Way halo. We reinterpret an existing quantum-enhanced dark-photon dataset obtained with a superconducting circuit QED platform originally developed for wave-like dark-photon dark-matter searches, consisting of a high-$Q$ niobium cavity in the $\mathrm{TM}_{010}$ mode dispersively coupled to a transmon qubit. By preparing four-component cat states and performing repeated quantum non-demolition parity measurements, analyzed with a hidden Markov model, we extract photon-transition probabilities for multiple cat amplitudes and integration times. The coupling to the GDPB is governed by a polarization- and angle-dependent cavity overlap function, which predicts a distinctive diurnal modulation of the excitation rate for both longitudinal and transverse polarizations. From the absence of such modulation, we set 90\% confidence-level bounds on the kinetic-mixing parameter $\epsilon$ for two benchmark production mechanisms (parametric and cascade decay) over the relativistic mass range $m_X \ll \omega_c$.

arXiv:2610.19751 [hep-ph]

(or arXiv:2610.19751v1 [hep-ph] for this version)

https://doi.org/10.48550/arXiv.2610.19751 Focus to learn more arXiv-issued DOI via DataCite (pending registration)

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