Frequency-selective single-photon detection with a double quantum dot

We use time-resolved charge detection methods to detect single photons absorbed by a double quantum dot (DQD). With the ability to tune the energy levels in the DQD, the frequency of the detected photon can be continuously varied between 10 and 80 GHz. The working principle of this device is demonstrated by measuring the radiation emitted by a nearby quantum point contact driven out-of-equilibrium at large bias voltage.