Silicon based vacancy centres hold promise for quantum computing

The research, reported in Nature Communications, exploits atomic defects in the crystal structure of diamond known as 'vacancy centres'. These gaps in the carbon lattice usually occur around an impurity, where another element has found its way into the structure. The perfect vacancy centre is said to be hard to come by, because it needs to possess precise characteristics. The work is said to be a breakthrough because researchers managed to access the state of electrons around a vacancy centre based on silicon and discovered it has some of the qualities for which they have been looking. Most current research of this type is said to use nitrogen as the impurity in the diamond. While nitrogen vacancy centres are abundant and their spin properties are good, the broad bandwidth of their optical signature means the imprint which the electron spin leaves on the photon is often lost. Dr Mete Atatüre, a Fellow of St John's College who co led the project, said: "The main advantage of the silicon vacancy centre is that its internal state is transferred to better quality photons, with a cleaner spectrum, when compared with other sources." In their work, the teams opted add silicon to lab-grown diamonds, then used a combination of magnetic field and polarised light to access the spin of the electrons trapped in the silicon vacancy centre. As well as being able to observe quantum states within the diamond, the researchers found the fluorescence was brighter than many other systems, with a narrower bandwidth. This enabled the spin properties of the trapped electron to be correlated with the properties of the emitted photon.