Gigahertz bandwidth electrical control over a dark exciton-based memory bit in a single quantum dot

An optical write-store-read process is demonstrated in a single InGaAs quantum dot within a charge-tunable device. A single dark exciton is created by nongeminate optical excitation allowing a dark exciton-based memory bit to be stored for over ~1 µs. Read-out is performed with a gigahertz bandwidth electrical pulse, forcing an electron spin-flip followed by recombination as a bright neutral exciton, or by charging with an additional electron followed by a recombination as a negative trion. These processes have been used to determine accurately the dark exciton spin-flip lifetime as it varies with static electric field.