Speaker
Description
Detecting extremely weak electromagnetic signals is a central challenge in quantum technologies and fundamental physics, especially in searches for dark matter candidates such as axions. We present a new detection scheme [1] based on passive superconducting thermoelectric single-photon detectors (TEDs), which use bipolar thermoelectric effects in tunnel junctions between superconductors with different energy gaps [2,3]. Unlike
conventional cryogenic detectors, TEDs operate without external bias and convert the absorption of a single photon directly into a measurable thermovoltage. This passivity greatly reduces electrical noise and thermal load, enabling scalable architectures and improved sensitivity at ultralow temperatures. The detector offers a broadband response from tens of gigahertz up to the petahertz regime, with an operational bandwidth over more than four orders of magnitude and signal-to-noise ratios ~15 even at gigahertz frequencies. A key feature is its quasi-digital response: the output voltage is nearly constant over a wide frequency range, while spectroscopic information is encoded in the time profile of the thermoelectric signal. This combination of broadband sensitivity, low noise, and intrinsic energy discrimination makes TEDs well-suited for detecting extremely faint photon fluxes. They are particularly relevant for dark matter searches, as their single-photon resolution in the microwave-to-terahertz range matches the requirements of axion and axion-like particle experiments, where photon-conversion events are expected to be rare and weak. Their passive operation, scalability, and compatibility with existing cryogenic infrastructure position superconducting thermoelectric detectors as promising tools for next-generation dark matter experiments and as a versatile, high-performance sensing platform at the interface of quantum metrology and astroparticle physics.
References
[1] A highly-sensitive broadband superconducting thermoelectric single-photon detector, F. Paolucci, G. Germanese, A. Braggio, and F. Giazotto, Appl. Phys. Lett. 122, 173503 (2023).
[2] Bipolar Thermoelectric Josephson Engine,G. Germanese, F. Paolucci, G. Marchegiani, A. Braggio, and F. Giazotto, Nat. Nanotechnol. 17, 1084 (2022).
[3] Phase-control of bipolar thermoelectricity in Josephson tunnel junctions, G. Germanese, F. Paolucci, G. Marchegiani, A. Braggio, and F. Giazotto, Phys. Rev. Applied 19, 014074 (2023).