Speaker
Description
The search for axions, light and weakly interacting dark matter particles, is nowadays mostly
exploited through photon coupling in the sub-meV region. In this range, only haloscopes have a
sensitivity to test theoretically motivated axion models. (talk by Di Vora for the last updates on
the QUAX haloscope[1])
Axions can also be exploited through coupling to fermions, but no experiment is able to reach the
required sensitivity in the sub-meV mass range to this date.
Recently, Single Microwave Photon Detectors (SMPDs), chips comprised of two resonators coupled
to a superconducting qubit, have been demonstrated to increase the sensitivity to axion signals in a
haloscope [2]. The SMPD resolution is a single microwave photon, which allows them to overcome
the so-called Standard Quantum Limits of linear amplifiers.
This novel improvement is now being implemented on a ferromagnetic haloscope[3] to further en-
hance the sensitivity to axions through coupling to the electron. The hypothetical axion signal will
excite the magnon mode of a ferromagnetic material (YIG in our case) inserted inside the haloscope
cavity. Under the condition of strong coupling, the hybrid mode polariton-magnon can be picked
up and read out with the SMPD.
The axion mass tuning is performed by varying the magnetic field acting on the ferromagnetic
material. The range to be probed, from 7.2 to 7.4 GHz, will also test the ability to downscale such
haloscopes.
References
[1] G Sardo Infirri et al. “Search for Postinflationary QCD Axions with a Quantum-Limited Tun-
able Microwave Receiver”. In: Physical Review Letters 135.21 (2025), p. 211002.
[2] Caterina Braggio et al. “Quantum-enhanced sensing of axion dark matter with a transmon-
based single microwave photon counter”. In: Physical Review X 15.2 (2025), p. 021031.
[3] N Crescini et al. “Axion search with a quantum-limited ferromagnetic haloscope”. In: Physical
Review Letters 124.17 (2020), p. 171801.