Optically induced rotation of a quantum dot exciton spin

TL;DR

This paper demonstrates a method to control and rotate the spin state of a quantum dot exciton using polarized laser pulses, enabling precise manipulation of quantum states for potential quantum information applications.

Contribution

The study introduces a novel optical technique for spin control in quantum dots using detuned laser pulses to achieve spin rotation, combining experimental and theoretical analysis.

Findings

Successful optical rotation of exciton spin states

Dependence of rotation angle on laser detuning

Agreement between experimental results and theoretical model

Abstract

We demonstrate control over the spin state of a semiconductor quantum dot exciton using a polarized picosecond laser pulse slightly detuned from a biexciton resonance. The control pulse follows an earlier pulse, which generates an exciton and initializes its spin state as a coherent superposition of its two non-degenerate eigenstates. The control pulse preferentially couples one component of the exciton state to the biexciton state, thereby rotating the exciton's spin direction. We detect the rotation by measuring the polarization of the exciton spectral line as a function of the time-difference between the two pulses. We show experimentally and theoretically how the angle of rotation depends on the detuning of the second pulse from the biexciton resonance.