Double quantum dot coupled to a radio-frequency single-electron transistor: Quantum measurement and back action

Abstract

The radio-frequency superconducting single electron transistor (RF-SET) is a highly sensitive and fast electrometer operating near the quantum limit. The back-action current noise of the SET induces voltage fluctuations on the system it is coupled to, dephasing its charge states. Here we propose to study the back action of the RF-SET by means of a double quantum dot (DQD) and, an RF-SET electrostatically coupled to one of the two dots. The inelastic current through the DQD is very sensitive to the spectral density of the voltage fluctuations in the nearby environment. By properly choosing the dot size and inter-dot tunnel barrier thickness, one can cause inelastic process to dominate the transport processes. A measurement of the inelastic current through the double dot system can then be used to calculate the spectral density of noise associated with the RF-SET and hence its back action. The design, fabrication and characterization of an RF-SET/DQD system is discussed in this work. Real-time studies of electron dynamics in coupled dots are also addressed.