Optimizing single-electron transistors as electrometers for high-precision electrometry of charge on quantum dots

Abstract

Single electron transistors (SET) are devices that can be used as highly sensitive electrometers, with sensitivities approaching the quantum noise level. They can be used as measurement devices for quantum systems, including quantum computers and quantum-dot cellular automata, and as logic elements in their own right as replacements for MOSFETs. For solid-state quantum computing applications it is vital to maximize the charge sensitivity to decrease readout time and increase readout fidelity. We analyze the interactions between a SET and a double dot system. The SET sensitivity is described in terms of the current variation through the SET due to a single electron's location on the two dots. We use finite element modeling to determine the capacitive coupling between all objects in our system, which in turn allows us to determine the current in the SET based on steady-state energy minimization arguments. We base our geometries on experiments involving a twin-SET device developed as a prototype for solid-state quantum computing read-out. Our model allows us to systematically vary the device geometry in order to optimize the sensitivity of the SET.