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

Abstract

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