Semiconductor devices for quantum technologies
Prof Jonathan Finley, Technische Universität München, Germany
The application of all-optical techniques to control and probe discrete quantum states in solids benefits from the possibility to apply well established methods from the quantum optics toolbox such as coherent control, optical pumping, resonant light scattering and dynamical decoupling. When combined with advanced semiconductor nanofabrication methods and the ability to electrically tune quantum systems, such electro-optical approaches open the way to interconnect quantum systems via photonic channels in highly integrated architectures.
In this talk, I will discuss several research themes pursued in my group in which individual, optically active quantum dots (QDs) are embedded within a tailored photonic environment and addressed via resonant and near resonant optical pulses. For example, we have applied ultrafast optical methods to probe coherent exciton and electron spin dynamics in individual electrically tunable dots over timescales ranging from a few picoseconds up to ~50μs, elucidating the processes responsible for spin decoherence. Typically, environmental coupling is detrimental to the exploration of such quantum phenomena. However, we show how controlled optically induced dissipation arising from exciton-LA phonon interactions can actually be exploited for high fidelity state preparation. Our focus will then move to nanostructures for integrated quantum photonics. We will discuss how slow light phenomena in GaAs photonic crystal waveguides can be used to efficiently direct single photons into propagating waveguide modes on a chip and illustrate how one can detect quantum light in-situ using integrated NbN superconducting single photon detectors. By temporally filtering the time-resolved luminescence signal stemming from individual resonantly excited dots, we demonstrate on-chip resonant fluorescence with a narrow linewidth <8μeV; key elements needed for the use of single photons to connect quantum systems in future quantum photonic circuits.
The Distinguished Lecturer Series (DLS) follows a colloquium format for a broad audience and will be followed by a reception to provide an opportunity for meeting the speaker.