Searching for Dark Matter with a Superconducting Qubit

TL;DR

This paper introduces a superconducting qubit-based microwave photon counting technique that enhances dark matter detection sensitivity by reducing noise below the quantum limit, enabling faster and more precise searches for hidden photon dark matter.

Contribution

The authors develop a novel quantum non-demolition photon counting method using a superconducting qubit, achieving significant noise reduction and setting new limits on hidden photon dark matter.

Findings

Achieved 15.7 dB noise reduction below the quantum limit.

Constrained hidden photon kinetic mixing angle to ≤ 1.68×10⁻¹⁵ at 6.011 GHz.

Demonstrated potential to accelerate dark matter searches by a factor of 1300.

Abstract

Detection mechanisms for low mass bosonic dark matter candidates, such the axion or hidden photon, leverage potential interactions with electromagnetic fields, whereby the dark matter (of unknown mass) on rare occasion converts into a single photon. Current dark matter searches operating at microwave frequencies use a resonant cavity to coherently accumulate the field sourced by the dark matter and a near standard quantum limited (SQL) linear amplifier to read out the cavity signal. To further increase sensitivity to the dark matter signal, sub-SQL detection techniques are required. Here we report the development of a novel microwave photon counting technique and a new exclusion limit on hidden photon dark matter. We operate a superconducting qubit to make repeated quantum non-demolition measurements of cavity photons and apply a hidden Markov model analysis to reduce the noise to 15.7 dB below the quantum limit, with overall detector performance limited by a residual background of real photons. With the present device, we perform a hidden photon search and constrain the kinetic mixing angle to $\epsilon \leq 1.68 \times 10^{-15}$ in a band around 6.011 GHz (24.86 $\mu$eV) with an integration time of 8.33 s. This demonstrated noise reduction technique enables future dark matter searches to be sped up by a factor of 1300. By coupling a qubit to an arbitrary quantum sensor, more general sub-SQL metrology is possible with the techniques presented in this work.