Scalable quantum computation based on quantum actuated nuclear-spin   decoherence-free qubits
  We propose a novel architecture for scalable quantum computation based on quantum actuated decoherence-free (DF) qubits. Each qubit is encoded by the DF subspace of a nuclear spin pair and has long coherence time. A nitrogen-vacancy center in diamond is chosen as the quantum actuator to realize initialization, readout and universal control of DF qubits with fidelities higher than 99%. It reduces the challenge of classical interfaces from controlling and observing complex quantum systems down to a simple quantum actuator. Our scheme also provides a novel way to handle complex quantum systems. 
Xing Rong, Lihong Dong, Jianpei Geng, Fazhan Shi, Zhaokai Li, Changkui   Duan and Jiangfeng Du
quant-ph