Ramsey Fringes in an Electric-Field-Tunable Quantum Dot System

Abstract

We report on Ramsey fringes measured in a single $\mathrm{InGaAs}/\mathrm{GaAs}$ quantum dot two-level system. We are able to control the transition energy of the system by Stark effect tuning. In combination with double pulse excitation this allows for a voltage controlled preparation of the phase and the occupancy of the two-level system. For long pulse delay times we observe extremely narrow fringes with spectral width below the homogeneous linewidth of the system. Implications on quantum information processing are discussed.