New understanding and engineering of defect qubits in diamond

Defects in diamond and other wide bandgap semiconductors with electronic spins that may be optically initialised and readout are promising qubit systems for a great diversity of quantum technologies. The negatively-charged nitrogen-vacancy (NV) centre in diamond is the best understood of these defects. It has driven major advances across quantum technology, including quantum computing, nanosensing and microscopy, and communications. However, there still remain unanswered questions about how best to employ it to initialise and read out clusters of coupled nuclear spin qubits. Recently, the negatively-charged silicon-vacancy (SiV-) and germanium-vacancy (GeV-) centres in diamond have come to prominence as possible alternatives to the NV centre in quantum computing and communications due to their superior optical properties. However, they currently suffer from poorer spin properties. Although not prominent, the ST1 centre in diamond promises superior performance as a bus for quantum registers formed from clusters of nuclear spin impurities. Progression towards using the ST1 centre has been hampered because its structure remains a mystery as well as difficulties in its reproduction. In the meantime, the search for new defects for quantum technologies is increasing in breadth and speed.

In this presentation, I will report the discovery of a new defect with an optically-addressable electronic spin: the neutral silicon-vacancy (SiV0) centre in diamond; as well as new knowledge of the ST1 centre’s structure, methods to enhance the spin properties of SiV- centres, and new insight into the NV centre’s mechanism of single-shot readout/ projective initialisation of nuclear spin qubits.