Keeping the photon in the dark: Enabling quantum dot dark state control by chirped pulses and magnetic fields.

Abstract

Dark excitons in quantum dots are not directly optically accessible, which has limited their use in practical applications. Nevertheless, they offer promising features such as substantially longer lifetimes compared to bright excitons, making them attractive candidates for quantum information processing. While previous theoretical and experimental studies have explored their potential, their full capabilities remain largely untapped. In this work, we demonstrate an all-optical storage and retrieval of the spin-forbidden dark exciton in a quantum dot from the ground state using chirped pulses and an in-plane magnetic field. Our experimental findings are in excellent agreement with theoretical predictions of the dynamics calculated using state-of-the-art product tensor methods. Our scheme enables an all-optical control of dark states without relying on any preceding decays. This opens up an unexplored dimension for optimal quantum control and time-bin entangled photon pair generation from quantum dots.