Quantum network demonstration based on photonic integrated diamond chips

The goal of the PhD project is to develop quantum nanophotonic devices based on diamond colour centres for the demonstration of scalable memories and repeaters for quantum networks. The memory element will rely on the progress in the Midi project on coherent control of nuclear spins. Once achieved, the PhD project will focus on its full demonstration as a quantum-coherent electro-nuclear two-qubit device. Using the optical transitions of this system, the PhD project will focus on the efficient generation of multiphoton entanglement, in particular a Greenberger-Horne-Zeilinger state for three photons with sufficient efficiency for loss-resilient quantum communication in a quantum network. The devices will comprise diamond nanochips with deterministically implanted colour centres and integrated into insulating photonic integrated circuit platforms. The colour centre of choice is the tin-vacancy centre with a spin 1/2 ground state, spin-selective optical transitions, and a resident nuclear spin through the 117Sn isotope. The photonic devices comprise thin diamond membranes with integrated microwave striplines initially to develop the necessary control protocols, and these devices are illustrated in the figures below for concept (top figure) and the actual devices (bottom figure). After the initial progress we will switch to diamond-etched waveguide arrays optimised for efficient coupling into tapered single-mode optical fibres via adiabatic mode transfer. This also provides a continuous flow from the Midi project to the PhD project.