Fast spin rotations by optically controlled geometric phases in a quantum dot

摘要

We demonstrate optical control of the geometric phase acquired by one of thespin states of an electron confined in a charge-tunable InAs quantum dot viacyclic 2pi excitations of an optical transition in the dot. In the presence ofa constant in-plane magnetic field, these optically induced geometric phasesresult in the effective rotation of the spin about the magnetic field axis andmanifest as phase shifts in the spin quantum beat signal generated by twotime-delayed circularly polarized optical pulses. The geometric phasesgenerated in this manner more generally perform the role of a spin phase gate,proving potentially useful for quantum information applications.