Sensitivity of ultralight axion dark matter search with optical quantum sensors

TL;DR

This paper explores the potential of optical quantum sensors to detect ultralight axion dark matter at unprecedented sensitivity levels, combining advanced quantum noise limits with superconducting circuits.

Contribution

It demonstrates the feasibility of using quantum-limited optical sensors with superconducting circuits to probe axion models in a new mass range near 10 neV.

Findings

Projected sensitivity could reach QCD axion models

Preliminary experiments validate prototype design

Potential to explore unexplored axion mass range

Abstract

An optical quantum sensor (OQS) based on lasers and alkali-metal atoms is a sensitive ambient-temperature magnetometer that can be used in axion dark matter search with an inductor-capacitor (LC) circuit at kHz and MHz frequencies. We have previously investigated the sensitivity of an LC circuit-OQS axion detector to ultralight axion dark matter that could be achieved using a fT-noise OQS constructed in our lab. In this paper, we investigate the sensitivity that could be potentially reached by an OQS performing close to the fundamental quantum noise levels of 10 aT/$\sqrt{\text{Hz}}$. To take advantage of the quantum-limited OQS, the LC circuit has to be made of a superconductor and cooled to low temperature of a few K. After considering the intrinsic noise of the advanced axion detector and characterizing possible background noises, we estimate that such an experiment could probe benchmark QCD axion models in an unexplored mass range near 10 neV. Reaching such a high sensitivity is a difficult task, so we have conducted some preliminary experiments with a large-bore magnet and a prototype axion detector consisting of a room-temperature LC circuit and a commercial OQS unit. This paper describes the prototype experiment and its projected sensitivity to axions in detail.