Color center qubits are encoded in electron orbital and spin eigenstates associated with single- or few- atomic impurities in solid-state host crystals, most commonly diamond. The nitrogen-vacancy (NV) center in diamond is the most widely studied system in the field of coherent optically active quantum defects owing to its long coherence time even at room temperature and the possibility of optical measurement of spin states through spin-dependent fluorescence.
While there are ongoing numerous efforts to realize a position-controlled, dense array of NV centers toward integrated quantum chips in diamond, deterministically positioning NV centers with atomic resolution is challenging. Another possibility is to use naturally given, coherent resources around an NV center, the 13C nuclear spins having spin-1/2. In this case NV center can be a sensitive probe of surrounding 13C nuclear spins, and through hyperfine interaction, quantum operation on the 13C nuclear spins can be also performed. In DKim lab at SNU, we are actively studying advanced quantum and classical control schemes toward realization of coherently controllable electron-nuclear spin registers in diamond.