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Deterministic quantum state transfer and remote entanglement using microwave photons
Nature ( IF 64.8 ) Pub Date : 2018-06-01 , DOI: 10.1038/s41586-018-0195-y
P. Kurpiers , P. Magnard , T. Walter , B. Royer , M. Pechal , J. Heinsoo , Y. Salathé , A. Akin , S. Storz , J.-C. Besse , S. Gasparinetti , A. Blais , A. Wallraff

Sharing information coherently between nodes of a quantum network is fundamental to distributed quantum information processing. In this scheme, the computation is divided into subroutines and performed on several smaller quantum registers that are connected by classical and quantum channels1. A direct quantum channel, which connects nodes deterministically rather than probabilistically, achieves larger entanglement rates between nodes and is advantageous for distributed fault-tolerant quantum computation2. Here we implement deterministic state-transfer and entanglement protocols between two superconducting qubits fabricated on separate chips. Superconducting circuits3 constitute a universal quantum node4 that is capable of sending, receiving, storing and processing quantum information5–8. Our implementation is based on an all-microwave cavity-assisted Raman process9, which entangles or transfers the qubit state of a transmon-type artificial atom10 with a time-symmetric itinerant single photon. We transfer qubit states by absorbing these itinerant photons at the receiving node, with a probability of 98.1 ± 0.1 per cent, achieving a transfer-process fidelity of 80.02 ± 0.07 per cent for a protocol duration of only 180 nanoseconds. We also prepare remote entanglement on demand with a fidelity as high as 78.9 ± 0.1 per cent at a rate of 50 kilohertz. Our results are in excellent agreement with numerical simulations based on a master-equation description of the system. This deterministic protocol has the potential to be used for quantum computing distributed across different nodes of a cryogenic network.Deterministic quantum state transfer and entanglement generation is demonstrated between superconducting qubits on distant chips using single photons.

中文翻译:

使用微波光子的确定性量子态转移和远程纠缠

在量子网络的节点之间连贯地共享信息是分布式量子信息处理的基础。在这个方案中,计算被分成子程序并在几个较小的量子寄存器上执行,这些寄存器通过经典和量子通道1连接。确定性而非概率性地连接节点的直接量子通道在节点之间实现了更大的纠缠率,并且有利于分布式容错量子计算2。在这里,我们在不同芯片上制造的两个超导量子位之间实现了确定性状态转移和纠缠协议。超导电路3构成了一个通用量子节点4,能够发送、接收、存储和处理量子信息5-8。我们的实现基于全微波腔辅助拉曼过程,该过程将 transmon 型人工原子的量子位状态与时间对称的巡回单光子纠缠或转移。我们通过在接收节点吸收这些流动光子来传输量子比特状态,概率为 98.1 ± 0.1%,在仅 180 纳秒的协议持续时间内实现了 80.02 ± 0.07% 的传输过程保真度。我们还以 50 kHz 的速率以高达 78.9 ± 0.1% 的保真度按需准备远程纠缠。我们的结果与基于系统主方程描述的数值模拟非常吻合。这种确定性协议有可能用于分布在低温网络不同节点的量子计算。
更新日期:2018-06-01
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