Ultrafast mapping of optical polarization states onto spin coherence of localized electrons in a semiconductor

TL;DR

This paper demonstrates an ultrafast optical method to prepare and measure spin states of donor-bound electrons in GaAs, enabling rapid quantum state control and tomography for quantum information applications.

Contribution

The study introduces a novel ultrafast laser pulse technique that maps photon polarization states onto electron spin states with high speed and precision.

Findings

Single laser pulses can prepare spin states with a bijective polarization mapping.

The process occurs orders of magnitude faster than spin dephasing.

Double pulse experiments show additive effects in spin state preparation.

Abstract

We experimentally demonstrate an ultrafast method for preparing spin states of donor-bound electrons in GaAs with single laser pulses. Each polarization state of a preparation pulse has a direct mapping onto a spin state, with bijective correspondence between the Poincar\'{e}-sphere (for photon polarization) and Bloch-sphere (for spin) state representations. The preparation is governed by a stimulated Raman process and occurs orders of magnitude faster than the spontaneous emission and spin dephasing. Similar dynamics governs our ultrafast optical Kerr detection of the spin coherence, thus getting access to spin state tomography. Experiments with double preparation pulses show an additive character for the preparation method. Utilization of these phenomena is of value for quantum information schemes.