High-resolution photocurrent spectroscopy of the positive trion state in a single quantum dot

Abstract

We demonstrate high-resolution photocurrent spectroscopy of the positive trion state (X+) in a single InAs/GaAs self-assembled quantum dot (QD). Exploiting a Coulomb-mediated renormalization of the X+ transition energy, our approach allows for a sub-mu eV resolution, which is more than four orders of magnitude higher than that in previous approaches. Furthermore, such high-resolution spectroscopy of X+ permits us to obtain precise values for the X+ permanent dipole moment and polarizability, by fitting a theoretical model to the measured transition energy as a function of electric field. Since optical initialization, manipulation, and readout of a QD spin rely on the trion state as an intermediary state, such high-resolution measurements of the X+ spectrum and its dipole moment are essential for performing high-fidelity quantum computing operations on QD spin qubits.