SPONTANEOUS EMISSION-SPECTRUM IN DOUBLE-QUANTUM DOT DEVICES

A double quantum dot device is a tunable two-level system for electron ic energy states. A de electron current was used to directly measure t he rates for elastic and inelastic transitions between the two levels. For inelastic transitions, energy is exchanged with bosonic degrees o f freedom in the environment. The inelastic transition rates are well described by the Einstein coefficients, relating absorption with stimu lated and spontaneous emission. The most effectively coupled bosons in the specific environment of the semiconductor device used here were a coustic phonons. The experiments demonstrate the importance of vacuum fluctuations in the environment for quantum dot devices and potential design constraints for their use for preparing long-lived quantum stat es.