Fast spin state initialization in a singly charged InAs-GaAs quantum dot by optical cooling.

TLDR: This work demonstrates fast spin state initialization with near unity efficiency in a singly charged quantum dot by optically cooling an electron spin by exploiting the spontaneous decay rate of the excited state.

Abstract: Quantum computation requires a continuous supply of rapidly initialized qubits for quantum error correction. Here, we demonstrate fast spin state initialization with near unity efficiency in a singly charged quantum dot by optically cooling an electron spin. The electron spin is successfully cooled from 5 to 0.06 K at a magnetic field of 0.88 T applied in Voigt geometry. The spin cooling rate is of order ${10}^{9}\text{ }\text{ }{\mathrm{s}}^{\ensuremath{-}1}$, which is set by the spontaneous decay rate of the excited state.