Quantum dynamics of single-photon detection using functionalized quantum transport electronic channels*

Single photon detectors have historically consisted of macroscopic-sized materials, but recent experimental and theoretical progress opens new approaches based on nanoscale and molecular electronics. Here we present a theoretical study of photodetection in a system composed of a quantum electronic transport channel functionalized by a photon absorber. Notably, the photon field, absorption process, transduction mechanism, and measurement process are all treated as part of one fully-coupled quantum system, with explicit interactions. Using non-equilibrium, time-dependent quantum transport simulations, we reveal the unique temporal signatures of the single photon detection process, and show that the system can be described using optical Bloch equations, with a new non-linearity as a consequence of time-dependent detuning caused by the back-action from the transport channel. We compute the photodetector signal-to-noise ratio and demonstrate that single photon detection is possible for realistic parameters.