Non-local nuclear spin quieting in quantum dot molecules: Optically-induced extended two-electron spin coherence time

摘要

We demonstrate the extension of coherence between all four two-electron spinground states of an InAs quantum dot molecule (QDM) via non-local suppressionof nuclear spin fluctuations in both constituent quantum dots (QDs), whileoptically addressing only the upper QD transitions. Long coherence times arerevealed through dark-state spectroscopy as resulting from nuclear spin lockingmediated by the exchange interaction between the QDs. Lineshape analysisprovides the first measurement of the quieting of the Overhauser fielddistribution correlating with reduced nuclear spin fluctuations.