Superconducting Josephson devices for quantum measurements in electronic circuits
Recent experiments revealed the quantum nature of electromagnetic fields of superconducting circuits at microwave frequencies. Individual quanta of these fields are photons with energy a few million times smaller than the energy of an optical photon and are extremely hard to detect. A promising device for microwave photon detection is based on Josephson junctions. Even a single microwave photon with tiny energy is sufficient to switch a junction from the superconducting to voltage state, and detection of a photon reduces to observation of voltage pulses across the junction.
In this talk, I will present a theoretical model of a current-bias Josephson junction interacting with a quantized electromagnetic field and show that Josephson photon detectors have relatively high efficiency of detection of a single microwave photon. I will also describe gain and added noise in SQUID amplifiers by analyzing effect of thermal noise on phase-slips timing.
I will discuss application of such devices for qubit readout for quantum information processing and to studies of photon emission statistics by quantum electronic devices.