Colour centres in diamond are attractive architectures for qubits and spin-photon interfaces, but the currently available candidates are not perfect. The nitrogen vacancy (NV) centre is famous as an optically addressable electron- and nuclear-spin qubit. However, the NV fluorescence spectrum exhibits a number of undesirable characteristics including a strong phonon sideband and, typically, spectral diffusion of the zero-phonon line (ZPL). More recently the related silicon vacancy (SiV) centre has been shown to have exceptional optical properties, but a fundamentally limited spin coherence time of only 40 ns.
An overview of the way that SiV physics has developed provides an excellent opportunity to demonstrate how our understanding of How Colour Centres Work has increased in recent years. This information has begun to enable a "smart search" for novel diamond qubits, and hopefully points towards a future where colour centres can be "engineered" for specific applications.
The brand-new germanium vacancy centre will be presented as an example of this process. There is a tantalising possibility that germanium vacancies could combine the excellent spin coherence properties of NV with the superb spectral properties of SiV, leading to an almost perfect diamond qubit.
Lachlan Rogers completed his PhD at ANU (Canberra) working under Professor Neil Manson. He worked on the fundamental physics of the nitrogen vacancy centre in diamond, and discovered the infrared transition that plays an important role in optically-induced spin polarisation. After three semesters of full-time lecturing, he moved to Germany to work in the labs of Professor Fedor Jelezko at Ulm. There Lachlan began work on the silicon vacancy centre in diamond, and has been central the development of optical access to electronic spin in this colour centre.