Quantum-state tomography of a single nuclear spin qubit of an optically manipulated ytterbium atom

A single Yb atom is loaded into a high-finesse optical cavity with a moving lattice, and its nuclear spin state is manipulated using a nuclear magnetic resonance technique. A highly reliable quantum state control with fidelity and purity greater than 0.98 and 0.96, respectively, is confirmed by the full quantum state tomography; a projective measurement with high speed (500 mu s) and high efficiency (0.98) is accomplished using the cavity QED technique. Because a hyperfine coupling is induced only when the projective measurement is operational, the long coherence times (T1 = 0.49 s and T2 = 0.10 s) are maintained.