Abstract:The traditional motivation to search for axion as a solution for the strong CP problem has recently been extended to more general hypothetical particles which couple with photons. These particles can be cold dark matter candidates via the misalignment mechanism and their experiments have gained popularity toward physics beyond the Standard Model. Depending on the scenario of the symmetry breaking scale, mass range of µeV and meV may be motivated. The corresponding photon frequency is from MHz to THz, and in particular, millimeter-wave photons (20 GHz-100 GHz) are the research frontier to search for post-inflationary scenario of the QCD axion as well as dark photons in the least constrained parameter space. Development of state-of-the-art bolometers, photon counting sensors, and eventually single-photon-sensitive calorimeters are motivated in galaxy halo axion search with such high frequency microwaves. However, this technological trend may not be naturally extrapolated to the laboratory-based experiment by using light-shinning-through-the-wall technique, which attempts to generate axions and detect reconverted photons. This is because one can make use of the phase information of incident photons via the classical lock-in amplifier method. In this seminar, we critically compare the photon counting and coherent wave detection in the millimeter-wave range. We clarify the quantum mechanical definition of optical coherency, photon counting, and amplitude detection, and consider physical devices to implement them with millimeter waves. We also briefly see recent progress in proof-of-principle tests of lock-in amplifier method for dark photons at 30 GHz. If time allows, we will see the ultimate advantage of single photon detectors in other applications.
Il seminario si terrà in Sala Galilei (stanza 131) ed in modalità remota sulla piattaforma Zoom al seguente indirizzo:
https://infn-it.zoom.us/j/84261721878?pwd=MDZNaGdBUlcvUUJXa2phSHZVZk5sdz09
ID riunione: 842 6172 1878
Passcode: 611379