Spatial and spectral control of diamond NV centres for scalable spin-photon interfaces.

: Heterogeneous integration of nanodiamonds with silicon nitride photonics for quantum optical technologies

Abstract

There is a global effort to implement networks capable of distributing quantum entanglement. In this context, nodes based on spins in solid state have been identified as one of the most viable routes towards achieving large scale quantum networks. For this reason, the development of scalable and efficient spin-photon interfaces is crucial. While there has been plenty of work on increasing both photon extraction efficiency and the entangling fidelity between these spin-photon systems, many of these implementations are only possible in restrictive a research facility environment or using materials difficult to produce in mass leading to issues of scalability.

The purpose of the research described in this thesis focuses on this last point: working towards the design and fabrication of scalable spin-photon interfaces. The approach explored here combines the inclusion of nanoparticles hosting spin defects with foundry compatible photonic platforms. From the selection of a spin defect and a photonics platform, to the design, fabrication and testing of nanophotonic structures around deterministically positioned spin defects, this thesis details the first steps required for demonstrating the scope of the proposed approach.

It was found that negatively charged nitrogen vacancy centres (NV⁻) in nanodiamonds are compelling spin systems to test this approach with. Furthermore, research proved that it is possible to integrate NV⁻ centres with silicon nitride photonics by modifying the silicon nitride’s stoichiometry, thereby suppressing its immanent photoluminescence. This allows for the detection of NV⁻ centres buried within the silicon nitride. It was also found that it is possible to attain spatial control of the nanodiamonds using scalable lithographic deposition methods. Finally, the fabrication of optical resonators designed to both increase the collection efficiency and enhance the NV⁻ centre zero phonon line emission was demonstrated.

Whilst the results shown here present several challenges and opportunities for improvement, they also show a promising path towards the fabrication of scalable spin-photon interfaces.

Date of Award	27 Sept 2022
Original language	English
Awarding Institution	University of Bristol
Sponsors	Consejo Nacional de Ciencia y Tecnologia Mexico
Supervisor	John G Rarity (Supervisor) & Krishna Coimbatore Balram (Supervisor)