Spin decoherence in diamond
DOI: 10.1063/1.4796841
An excellent heat conductor and electrical insulator, diamond is also a potential host for qubits—the units of quantum information that exist in a superposition of two different states. Previously demonstrated qubits include photons that can be in either of two polarization states, Cooper pairs that can reside on either side of a Josephson junction, and quantum dots with a net spin either up or down. In diamond, removing two neighboring carbon atoms and replacing one of them with a nitrogen atom results in a defect called a nitrogen–vacancy center. Such an NV center has a net electronic spin; can be optically imaged, polarized, and “read out”; and keeps its phase coherence for hundreds of microseconds at room temperature. A team of physicists from the University of California, Santa Barbara, and Ames Lab in Iowa, has now looked in detail at that coherence by watching an individual NV center interact with its environment—a local “spin bath” of randomly substituted nitrogen atoms in the diamond crystal. They found that the coupling between the NV center and the bath, and hence the center’s decoherence time, could be finely tuned with an applied magnetic field. A rich variety of dynamical behavior could be accessed, including Rabi oscillations and a resonance “beating” phenomenon. (
