On the back-action of THz measurement on the total current of quantum devices

Measuring a quantum system implies some kind of perturbation of the system itself. A novel approach to include the perturbation of the quantum electron device, i.e. the back-action, due to the TeraHertz (THz) measurement of the total current is presented. The approach is based on a microscopic description of the interaction between the quantum system and the measuring apparatus, in terms of conditional (Bohmian) wave functions. The disturbance of the quantum system due to measurements at THz frequencies and the (perturbed) value of the total current is numerically computed for a simple two-terminal device. Contrarily to traditional strong (i.e. projective) measurements, it is shown that the measurement of the total current at THz frequencies can be modeled by a weak measurement. An additional unavoidable source of fluctuations of the current is predicted at THz frequencies due to the back-action (i.e. the quantum measurement).