Center for Photonic Communication and Computing, EECS Department, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3118, USA.
Phys Rev Lett. 2011 Feb 4;106(5):053901. doi: 10.1103/PhysRevLett.106.053901. Epub 2011 Feb 1.
To deploy and operate a quantum network which utilizes existing telecommunications infrastructure, it is necessary to be able to route entangled photons at high speeds, with minimal loss and signal-band noise, and--most importantly--without disturbing the photons' quantum state. Here we present a switch which fulfills these requirements and characterize its performance at the single photon level. Furthermore, because this type of switch couples the temporal and spatial degrees of freedom, it provides an important new tool with which to encode multiple-qubit states in a single photon. As a proof-of-principle demonstration of this capability, we demultiplex a single quantum channel from a dual-channel, time-division-multiplexed entangled photon stream, effectively performing a controlled-bit-flip on a two-qubit subspace of a five-qubit, two-photon state.
要部署和运行利用现有电信基础设施的量子网络，就必须能够以最小的损耗和信号带宽噪声高速路由纠缠光子，而且——最重要的是——不能干扰光子的量子态。在这里，我们提出了一种满足这些要求的开关，并在单光子水平上对其性能进行了表征。此外，由于这种类型的开关耦合了时间和空间自由度，它为在单个光子中编码多个量子比特状态提供了一个重要的新工具。作为这种能力的原理验证演示，我们从双信道时分复用纠缠光子流中解复用单个量子信道，有效地在五光子双光子态的两个量子比特子空间上执行受控位翻转。
