Voltage-controlled Motional Narrowing in a Semiconductor Quantum Dot

We demonstrate the control with a dc voltage of the environment-induced decoherence in a semiconductor quantum dot (QD) embedded in a gated field-effect device. The electrical control of the spectral diffusion dynamics governing the QD decoherence induces various effects, and in particular a narrowing of the QD emission spectrum on increasing the electric field applied to the structure. We develop a model in the framework of the pre-Gaussian noise theory that provides a quantitative interpretation of our data as a function of gate voltage. The standard phenomenology of motional narrowing described in nuclear magnetic resonance is successfully reached by hastening the carrier escape from the traps around the QD through tunneling under reverse bias voltage. Our study paves the way to a protection of zero-dimensional electronic states from outside coupling through a voltage-controlled motional narrowing effect.