Researchers have placed two nitrogen atoms a few nanometers apart, so that laser excitation can create a quantum mechanical coupling. The key to the solution: it works with high precision, reliably, and even at room-temperature only in a diamond.
The nitrogen-vacancy center (N-V center) is one of the numerous point defects in diamond. Its most explored and useful property is photoluminescence, which can be easily detected from an individual N-V center. The intensity and wavelength of this photoluminescence can be altered by applying a magnetic field, electric field, microwave radiation or light or their various combinations, and sharp resonances are observed as a function of the parameters of those applied fields. Those remarkable resonances are explained in terms of various electron spin related phenomena, such as quantum entanglement, spin-orbit interaction, and Rabi oscillations. Their complete understanding requires advanced knowledge of quantum optics and is beyond the scope of this article. More comprehensible however is the summary of the achieved results and their consequences: Electron spins at the individual N-V center, localized at atomic scales, can be manipulated at room temperature by applying light, magnetic, electric or microwave fields or their combinations. Such individual center can be viewed as a basic unit of a quantum computer, and it has potential applications in novel, more efficient fields of electronics and computational science including spintronics, quantum cryptography, quantum computing, etc.
The vision –
* Use ion implantation to create several N-V centers
* couple them together in a scalable fashion and have a classical computer control it all
Devices that harness the laws of quantum physics hold the promise for information processing that outperforms their classical counterparts, and for unconditionally secure communication. However, in particular, implementations based on condensed-matter systems face the challenge of short coherence times. Carbon materials particularly diamond however, are suitable for hosting robust solid-state quantum registers, owing to their spin-free lattice and weak spin–orbit coupling. Here we show that quantum logic elements can be realized by exploring long-range magnetic dipolar coupling between individually addressable single electron spins associated with separate colour centres in diamond. The strong distance dependence of this coupling was used to characterize the separation of single qubits (98±3 Å) with an accuracy close to the value of the crystal-lattice spacing. Our demonstration of coherent control over both electron spins, conditional dynamics, selective readout as well as switchable interaction should open the way towards a viable room-temperature solid-state quantum register. As both electron spins are optically addressable, this solid-state quantum device operating at ambient conditions provides a degree of control that is at present available only for a few systems at low temperature.