Speaker
Description
Axions are well-motivated dark matter candidates that can be converted into extremely weak microwave photons in a strong magnetic field. At frequencies above a few gigahertz, axion searches relying on phase-preserving linear amplification are increasingly limited by the standard quantum limit, motivating the development of photon-counting receivers. Transmon-based single microwave photon detectors (SMPDs) can map an itinerant microwave photon onto a qubit excitation through a pump-activated four-wave-mixing process combined with engineered dissipation [1,2]. This approach has recently been implemented in an axion haloscope, demonstrating an approximately 20-fold enhancement in search speed compared with quantum-limited linear-amplifier-based detection[3].
We are developing a transmon-based SMPD optimized for axion dark matter searches. As a first step, we improved the fabrication process for superconducting transmon circuits and achieved qubit energy-relaxation times of several tens of microseconds with high yield. Using this improved fabrication process, we produced a prototype SMPD and performed initial cryogenic characterization, including the resonator and qubit parameters, coherence times, and progress toward the activation and calibration of the photon-to-qubit conversion process. These results establish the key device platform for a low-noise photon-counting receiver and guide further optimization of the detection efficiency, bandwidth, and dark-count rate for future axion searches.
reference
[1] Lescanne et al., PRX 10, 021038 (2020).
[2] Balembois et al., PRAppl. 21, 014043 (2024). [3] Braggio et al., PRX 15, 021031 (2025).
| Primary Abstract Topic | Experiment: Axions and Wave-Like-DM |
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