In the field of diamond-defect-based quantum information processing, electron spins at defect sites sit within a diamond spin-vacuum and external interface is enabled via photon emission. In comparison to nitrogen-vacancy defects in diamond, silicon-vacancy (SiV) defects possess superior coherence of emitted photons, but limited spin coherence. In this invention, the team identified and overcame this spin coherence limitation by cooling the SiV defect below the spin-orbit energy, thereby splitting responsibility for the poor spin coherence.

Below this temperature threshold the spin qubit exhibits a superb spin coherence time of 13 ms, exceeding many competing technologies. As a result, the system embodies an important quantum building block, since it entangles a non-local photon with a localized, coherent electron spin. This achievement could form the basis for a quantum computing system longer term, but more near term could be applied to constructing a quantum network and in quantum security applications. By the time the spin in the cryostat decoheres, the photon can propagate down an optical fiber to a distance (~ 103 km) comparable to global distance scales.

A paper on this work was published in Physical Review Letters.