Finite-Frequency Noise and Dynamical Charge Susceptibility in Single and Double Quantum Dot Systems

This study reports on finite-frequency noise and dynamical charge susceptibility in out-of-equilibrium quantum dot systems. Both single and double quantum dots connected to one or two reservoirs of electrons are considered, and these quantities are calculated by using the non-equilibrium Green function technique. The results are discussed in the light of experimental results, particularly in the low-frequency limit for which an interpretation in terms of an equivalent RC-circuit is made. Anti-symmetrized noise is also studied, defined as the difference between absorption and emission noises, and its relationship with the dynamical charge susceptibility in single quantum dots is established. In double quantum dots, the similarities between the dynamical charge susceptibility, the absorption noise, and the dot occupancy, are highlighted by comparing their respective variations with the bias voltage applied between the two reservoirs, and the detuning energy defined as the difference between the lowest level energies in the two dots. The similarities between finite-frequency noise and dynamical charge susceptibility in quantum dots, the qubit building block, have been studied. In a single-level dot system, an explicit relationship between these quantities has been established. In multi-level dot or double dot systems, studies of the variation of finite-frequency noise and dynamical charge susceptibility with bias voltage and detuning energy show similarities that have been characterized.image