Deliverable D2.3: Concept of a quantum heat detector

Experimental realization of a detector for a single quantum of radiation by calorimetric means has become popular over the past years. In this context, the fluctuations of the electron-phonon heat current are important since they determine the fundamental bound of detectable energy of the radiation quantum. Since the fluctuation-dissipation theorem holds, our practical task is to optimize the thermal conductance considering various electronic systems including superconducting proximity structures. Motivated by the experiments that have been performed by ESR 4 and Prof. Jukka Pekola from ALLTO University, we were supposed to provide an appropriate theoretical description of such an effect. To do so, we have employed the quasiclassical Keldysh Green's formalism and the linear response theory.