Coherent Population Trapping of an Electron Spin in a Single Negatively   Charged Quantum Dot
  Coherent population trapping (CPT) refers to the steady-state trapping of population in a coherent superposition of two ground states which are coupled by coherent optical fields to an intermediate state in a three-level atomic system. Recently, CPT has been observed in an ensemble of donor bound spins in GaAs and in single nitrogen vacancy centers in diamond by using a fluorescence technique. Here we report the demonstration of CPT of an electron spin in a single quantum dot (QD) charged with one electron. 
Xiaodong Xu, Bo Sun, Paul R. Berman, Duncan G. Steel, Allan S.   Bracker, Dan Gammon, L. J. Sham