Sam Carter, Naval Research Laboratory
Over the past few decades a number of exciting applications of quantum coherence and entanglement have been developed that promise fundamental improvements in a variety of areas, including computing, secure communications, metrology, and sensing. A team of scientists at the Naval Research Laboratory have been working for many years to develop a physical implementation for these quantum information applications using semiconductor indium arsenide quantum dots. This system has the advantages of a robust solid state host, strong optical transitions, mature device fabrication, engineerable properties, and a scalable, monolithic architecture. A single electron or hole spin within a quantum dot acts as a stationary quantum bit that can be optically controlled on a picosecond timescale. In this presentation, I will discuss how a spin in a quantum dot or in a pair of coupled quantum dots can also be used for sensing mechanical motion and for generating tunable single photons. To sense motion, quantum dots have been incorporated into mechanical resonators, which couple to the dots through strain. When mechanical resonators are driven, the optical transitions of QDs shift significantly, and the spin states shift as well, particularly the hole spins. To generate photons, we make use of Raman spin-flip processes (1,2) which have the advantage of generating photons with properties determined by the drive laser and the spin properties. In this way, we are able to demonstrate spectral and temporal control over single photon wave packets.
1. Sweeney, T. M. et al. Cavity-stimulated Raman emission from a single quantum dot spin. Nat. Photonics 8, 442–447 (2014).