Is Telegraph Noise A Good Model for the Environment of Mesoscopic Systems?

Some papers represent the environment of a mesosopic system (e.g., a qubit in a quantum computer or a quantum junction) by a neighboring fluctuator, which generates a fluctuating electric field—a telegraph noise (TN)—on the electrons in the system. An example is a two-level system, that randomly fluctuates between two states with Boltzmann weights determined by an effective temperature. To consider whether this description is physically reasonable, we study it in the simplest example of a quantum dot which is coupled to two electronic reservoirs and to a single fluctuator. Averaging over the histories of the TN yields an inflow of energy flux from the fluctuator into the electronic reservoirs, which persists even when the fluctuator’s effective temperature is equal to (or smaller than) the common reservoirs temperature. Therefore, the fuluctuator’s temperature cannot represent a real environment. Since our formalism allows for any time dependent energy on the dot, we also apply it to the case of a non-random electric field which oscillates periodically in time. Averaging over a period of these oscillations yields results which are very similar to those of the TN model, including the energy flow into the electronic reservoirs. We conclude that both models may not give good representations of the true environment.