Blok M S, Kalb N, Reiserer A, Taminiau T H, Hanson R
QuTech and Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, 2600 GA Delft, The Netherlands.
Faraday Discuss. 2015;184:173-82. doi: 10.1039/c5fd00113g. Epub 2015 Sep 28.
Single defect centers in diamond have emerged as a powerful platform for quantum optics experiments and quantum information processing tasks. Connecting spatially separated nodes via optical photons into a quantum network will enable distributed quantum computing and long-range quantum communication. Initial experiments on trapped atoms and ions as well as defects in diamond have demonstrated entanglement between two nodes over several meters. To realize multi-node networks, additional quantum bit systems that store quantum states while new entanglement links are established are highly desirable. Such memories allow for entanglement distillation, purification and quantum repeater protocols that extend the size, speed and distance of the network. However, to be effective, the memory must be robust against the entanglement generation protocol, which typically must be repeated many times. Here we evaluate the prospects of using carbon nuclear spins in diamond as quantum memories that are compatible with quantum networks based on single nitrogen vacancy (NV) defects in diamond. We present a theoretical framework to describe the dephasing of the nuclear spins under repeated generation of NV spin-photon entanglement and show that quantum states can be stored during hundreds of repetitions using typical experimental coupling parameters. This result demonstrates that nuclear spins with weak hyperfine couplings are promising quantum memories for quantum networks.
金刚石中的单缺陷中心已成为量子光学实验和量子信息处理任务的强大平台。通过光学光子将空间分离的节点连接成量子网络，将实现分布式量子计算和远程量子通信。最初关于捕获原子和离子以及金刚石中的缺陷的实验已经证明了两个节点之间在数米距离上的纠缠。为了实现多节点网络，非常需要在建立新的纠缠链路时能够存储量子态的额外量子比特系统。这种存储器允许进行纠缠蒸馏、纯化和量子中继器协议，从而扩展网络的规模、速度和距离。然而，要发挥作用，存储器必须对纠缠生成协议具有鲁棒性，而该协议通常必须重复多次。在这里，我们评估了将金刚石中的碳核自旋用作与基于金刚石中单氮空位（NV）缺陷的量子网络兼容的量子存储器的前景。我们提出了一个理论框架来描述在重复生成NV自旋 - 光子纠缠时核自旋的退相，并表明使用典型的实验耦合参数，量子态可以在数百次重复过程中存储。这一结果表明，具有弱超精细耦合的核自旋是用于量子网络的有前景的量子存储器。
