On the noise induced by the measurement of the THz electrical current in quantum devices

TL;DR

This paper models the measurement-induced noise in THz electrical current in quantum devices, revealing it as a weak measurement effect that introduces significant noise at THz frequencies but is negligible at low frequencies.

Contribution

It introduces a quantum measurement model using Bohmian conditional wave functions to analyze noise in THz current measurements in quantum devices.

Findings

Measurement acts as a weak perturbation causing noise at THz frequencies.

Numerical simulations confirm the weak measurement nature and associated noise.

At low frequencies, measurement noise is negligible.

Abstract

From a quantum point of view, it is mandatory to include the measurement process when predicting the time-evolution of a quantum system. In this paper, a model to treat the measurement of the (TeraHertz) THz electrical current in quantum devices is presented. The explicit interaction of a quantum system with an external measuring apparatus is analyzed through the unambiguous notion of the Bohmian conditional wave function, the wave function of a subsystem. It it shown that such THz quantum measurement process can be modeled as a weak measurement: The systems suffers a small perturbation due to the apparatus, but the current is measured with a great uncertainty. This uncertainty implies that a new source of noise appears at THz frequencies. Numerical (quantum Monte Carlo) experiments are performed confirming the weak character of this measurement. This work also indicates that at low frequencies this noise is negligible and it can be ignored. From a classical point of view, the origin of this noise due to the measurement at THz frequencies can be attributed to the plasmonic effect of those electrons at the contacts (by interpreting the contacts themselves as part of the measuring apparatus).