Coherent optical manipulation of triplet-singlet states in coupled quantum dots

TL;DR

This paper demonstrates how spin-orbit coupling enables coherent optical control of singlet and triplet electron spin states in coupled quantum dots, with potential applications in quantum information processing.

Contribution

It introduces a method for coherent manipulation of two-electron spin states in quantum dot molecules via Raman transitions influenced by spin-orbit coupling.

Findings

Weak spin-orbit effects enable Raman coupling of singlet-triplet states.

Metastable ground states can serve as auxiliary states for quantum tasks.

Coherent control of spin states is feasible with slight differences in g-factors.

Abstract

We show that spin-orbit coupling in a quantum dot molecule allows for coherent manipulation of two electron spin states using Raman transitions. Such two-electron spin states defined by the singlet and triplet states of two exchange coupled quantum dots can have favorable coherence properties. In addition, two of the four metastable ground states in this system can be used as auxiliary states that could facilitate implementation of tasks such as mapping of spin states to that of a single propagating photon. We find that even weak spin-orbit effects -- manifesting themselves as slightly different g-factors for the electron and the hole -- would allow for the coherent Raman coupling of the singlet-triplet states. We also discuss the possibilities for implementing quantum optical techniques for spin preparation and manipulation.