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

TL;DR

This paper demonstrates a method to rapidly rotate electron spins in quantum dots using optically controlled geometric phases, which could be useful for quantum information processing.

Contribution

It introduces a technique to control spin states via geometric phases in quantum dots using optical methods, enabling fast spin rotations.

Findings

Optical control induces geometric phases in quantum dot spins.

Resulting phase shifts enable effective spin rotations.

Potential application as a spin phase gate for quantum computing.

Abstract

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