The quest for a solid-state system where quantum information can be manipulated at room temperature, is an ongoing enterprise. One system that has emerged as a candidate is the nitrogen-vacancy (N-V) color center in diamond.
The N-V center consists of a nitrogen atom sitting next to a vacant site in the lattice (see figure below). Because its spin state can be both initialized and read-out optically, it is well suited for studying electronic and nuclear spin phenomena at room temperature. Due to the weak spin-orbit coupling in diamond, the single spin of an N-V center is only weakly coupled to its environment and spin coherence times up to hundreds of microseconds at room temperature have been observed.
Using a room-temperature confocal microscope, it is possible to study single N-V centers through their photoluminescence (PL). On the right, we show a 20 μm by 20 μm PL-image with several resolution-limited features.
We can identify them as single N-V centers through the anti-bunching behavior at τ = 0 in the photon-correlation measurements and the electron spin resonance dip around 2.88 GHz, which corresponds to the ground-state spin slitting (both shown on the left).
We make use of several experimental "knobs" for studying and controlling the spin state of the N-V center: the angle and magnitude of the applied magnetic field, the power and the duration of the optical excitation, and RF magnetic fields for coherently rotating the electron and nuclear spin.
To learn more about our studies, please refer to "The Diamond Age of Spintronics", David D. Awschalom, Ryan Epstein, and Ronald Hanson, Scientific American, Volume 297, pages 84-91 (October, 2007).