Quantum-Enhanced Dark Matter Search Using Cat States

TL;DR

This paper demonstrates the first use of four-component cat states in a superconducting microwave cavity to enhance dark photon detection sensitivity, achieving significant improvements over previous methods.

Contribution

It introduces a novel application of macroscopic superposition states for quantum-enhanced dark matter searches, with experimental validation and improved sensitivity.

Findings

8.1-fold increase in signal photon rate

Constrained dark photon kinetic mixing angle to <7.32×10⁻¹⁶

Achieved sensitivity at 10⁻¹⁶ level within 100 kHz bandwidth

Abstract

Quantum metrology has recently emerged as a powerful approach for dark matter (DM) searches, particularly using nonclassical bosonic states in microwave cavities that are sensitive to weak signals. Nonclassical cat states - macroscopic superpositions of coherent states featuring sub-Planck interference structures - offer promising advantages for high-precision measurements. However, their practical utility in DM search remains unexplored. Here, we report the first experimental application of four-component cat states within a high-quality superconducting microwave cavity to search for dark photons, a potential DM candidate. We demonstrate an 8.1-fold enhancement in the signal photon rate and constrain the dark photon kinetic mixing angle to an unprecedented $\epsilon < 7.32 \times 10^{-16}$ near 6.44~GHz (26.6~$\mu$eV). By employing a parametric sideband drive to actively tune the cavity frequency, we achieve dark photon searches and background subtraction across multiple frequency bins, yielding a sensitivity at the $10^{-16}$ level within a 100~kHz bandwidth. Our cat-assisted DM (CaD) search and frequency-scanning techniques demonstrate substantial improvements over previous results, promising potential implications in quantum-enhanced searches for new physics.