Nanophotonic enhancement of solid-state quantum emitters

Photons are excellent carriers of quantum information. They retain coherence for long periods of time and can be sent over large distances, making them key components of quantum technologies including a secure internet, computers that can surpass any classical machine, and simulators which will assist with the development of new medicines and materials. However, there are multiple roadblocks which need to be removed before these goals can be reached. Photons are difficult to generate on demand, when generated they travel at the speed of light making them difficult to store and synchronise, and they must be at a wavelength in the low-loss region of silica glass to be compatible with optical fiber networks. During this PhD I will overcome these problems using solid-state quantum emitters such as single organic molecules and crystalline defects, in both cases coupled to nanophotonic structures to generate photons efficiently. Emission from the solid-state molecule dibenzoterrylene is between 780 nm to 795 nm, making it compatible with the D1 and D2 transitions in rubidium atoms. This promising source of photons has a high probability to emit coherent, narrowband photons, but it is difficult to always collect the emitted photons to a well-defined optical mode. During this PhD I will design and fabricate a vertical-emitting cavity with a reservoir that can be filled with organic molecules. Once a molecule is coupled to the cavity it will emit vertically at a high rate into a mode that is well matched to an optical fiber. This will enable novel quantum interference demonstrations and for interfacing molecule emission with atomic systems. Emission from carbon defects in silicon is at wavelengths spanning 1200 nm to 1500 nm, making them compatible with long-distance quantum networks. During this PhD I will design and fabricate silicon photonic structures - waveguides and cavities in guided modes on a silicon chip - which will enhance the emission and collection of photons from these defects allowing me to build an integrated, on-demand, telecommunications compatible photon source. Being in silicon these emitters benefit from the huge infrastructure and investment in making current computer chips and will be transformative for quantum communication and miniaturised chip-based quantum computation and simulation.
The use of several novel microscopy and spectroscopy techniques will be utilised during this project. More specifically, I will employ a bespoke cryogenic confocal microscope to stimulate the emission of photons and also laser-scanning fluorescence spectroscopy to analyse the spectra of varying defects. These both represent novel approaches to methodology that will be employed during my project.
This PhD aligns with the EPSRC research areas "Quantum physics for new quantum technologies", "Quantum optics and information", "Quantum devices components and systems", "Optical devices and subsystems", and "Photonic materials".