Phys. Rev. Lett. 107, 150503 (2011)

Nitrogen-vacancy centres in diamond have many of the requirements for quantum-information protocols. Their spin can be addressed optically and they have long coherence times. What is still missing, however, is the possibility of controlling the interaction between two or more spins. Alejandro Bermudez and colleagues have proposed a scheme that could solve the problem and allow control of the interaction between nuclear spins in distant nitrogen-vacancy centres. Unfortunately the dipole–dipole interaction between distant nuclear spins is too weak to warrant communication between the two. However, the electron spins can function as intermediaries. Their dipole–dipole interaction is long range and each of them can interact with the respective nuclear spin through hyperfine interaction. According to the model, the realization of quantum gates should be possible, especially if the spins are driven by microwave fields, which have the additional advantage of reducing the negative decoherence effects of the environment. The scheme should work with systems other than nitrogen-vacancy centres, making an interesting approach to realize solid-state quantum-information processors.