Experimental demonstration of a BDCZ quantum repeater node
Experimental demonstration of a BDCZ quantum repeater node
复制标题
BDCZ量子中继器节点的实验演示
DOI：
10.1038/nature07241
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发表时间：
2008-08-28
期刊：
影响因子：
64.8
通讯作者：
Pan, Jian-Wei
中科院分区：
文献类型：
--
作者：
Yuan, Zhen-Sheng;Chen, Yu-Ao;Pan, Jian-Wei
量子通信是一种为网络中的信息交换提供有效和安全的方法。（100公里量级的）大规模量子通信已经实现；然而，在这个距离尺度之外，就会出现严重的问题，主要是由于传输通道中不可避免的光子损失。当光子探测器中暗计数的概率与正确检测到光子的概率相当时，量子通信最终会失败。为了克服这一问题，Briegel, d<e:1> r， Cirac和Zoller （BDCZ）引入了量子中继器的概念，将纠缠交换和量子存储器结合起来，有效地延长了可实现的距离。虽然纠缠交换已经被实验证明，但由于集成量子存储器的困难，BDCZ量子中继器的实现被证明具有挑战性。在这里，我们实现了纠缠交换和光的存储和检索，这是BDCZ量子中继器的一个组成部分。我们采用了一种将BDCZ策略与原子量子存储相结合的方案。两个原子系综，每个原子系综最初都与一个发射的光子纠缠在一起，通过对两个单光子进行联合贝尔态测量，在它们通过一个300米的基于光纤的通信信道后，被投射到纠缠态。纠缠态存储在原子系综中，稍后通过将原子激发转化为光子来验证。我们的方法本质上是相位不敏感的，并建立了实现以静止原子量子位作为量子存储器和飞行光子量子位作为量子信使的量子中继器所需的基本元素。
Quantum communication is a method that offers efficient and secure ways for the exchange of information in a network. Large-scale quantum communication,,,(of the order of 100 km) has been achieved; however, serious problems occur beyond this distance scale, mainly due to inevitable photon loss in the transmission channel. Quantum communication eventually fails when the probability of a dark count in the photon detectors becomes comparable to the probability that a photon is correctly detected. To overcome this problem, Briegel, Dür, Cirac and Zoller (BDCZ) introduced the concept of quantum repeaters, combining entanglement swapping and quantum memory to efficiently extend the achievable distances. Although entanglement swapping has been experimentally demonstrated, the implementation of BDCZ quantum repeaters has proved challenging owing to the difficulty of integrating a quantum memory. Here we realize entanglement swapping with storage and retrieval of light, a building block of the BDCZ quantum repeater. We follow a scheme,that incorporates the strategy of BDCZ with atomic quantum memories. Two atomic ensembles, each originally entangled with a single emitted photon, are projected into an entangled state by performing a joint Bell state measurement on the two single photons after they have passed through a 300-m fibre-based communication channel. The entanglement is stored in the atomic ensembles and later verified by converting the atomic excitations into photons. Our method is intrinsically phase insensitive and establishes the essential element needed to realize quantum repeaters with stationary atomic qubits as quantum memories and flying photonic qubits as quantum messengers.