Control and measurement of electron spins in semiconductor quantum dots

Abstract

Abstract We present an overview of experimental steps taken towards using the spin of a single electron trapped in a semiconductor quantum dot as a spin qubit [Loss and DiVincenzo, Phys. Rev. A 57 , 120 (1998)]. Fabrication and characterization of a double quantum dot containing two coupled spins has been achieved, as well as initialization and single‐shot read‐out of the spin state. The relaxation time T 1 of single‐spin and two‐spin states was found to be on the order of a millisecond, dominated by spin–orbit interactions. The time‐averaged dephasing time T 2 *, due to fluctuations in the ensemble of nuclear spins in the host semiconductor, was determined to be on the order of several tens of nanosceconds. Coherent manipulation of single‐spin states can be performed using a microfabricated wire located close to the quantum dot, while two‐spin interactions rely on controlling the tunnel barrier connecting the respective quantum dots [Petta et al., Science 309 , 2180 (2005)]. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)