Direct Observation of the Origin of Spectral Diffusion in Colloidal Quantum Dots

An essential ingredient of quantum photonic technologies is the ability to control and read out single- or few-electron excitations. In solid-state sources of quantum light, such capabilities require a thorough understanding of both the emitters themselves and their noisy environment. In particular, the effect of electric-field noise in the micro environment of an emitter is still not well understood even though it is arguably the largest contributor to spectral noise. Here, we apply optical cryogenic spectroscopy of individual colloidal quantum dots (CQDs) to provide the first direct proof that the quantum confined Stark effect (QCSE) is the underlying mechanism of spectral instabilities.