Experimental demonstration of quantum walks with initial superposition states
Experimental demonstration of quantum walks with initial superposition states
复制标题
具有初始叠加态的量子行走的实验演示
DOI：
10.1038/s41534-019-0155-x
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发表时间：
2019
影响因子：
7.6
通讯作者：
Yang Chui-Ping
中科院分区：
文献类型：
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作者：
Su Qi-Ping;Zhang Yu;Yu Li;Zhou Jia-Qi;Jin Jin-Shuang;Xu Xiao-Qiang;Xiong Shao-Jie;Xu QingJun;Sun Zhe;Chen Kefei;Nori Franco;Yang Chui-Ping
离散时间量子行走（DTQW）初始叠加态的制备对于DTQW的研究和应用是必要的。基于编码方法，我们在这里提出了线性光学中的DTQW协议，该协议能够准备步行者和硬币的任意初始叠加状态，并且除了步行者的概率分布之外还能够获得DTQW的状态。通过该协议，我们仅使用无源线性光学元件，通过实验演示了偏振空间中的 DTQW，步行者和硬币最初都处于叠加态。步行者不同的初始叠加态对DTQW的传播速度以及硬币与步行者之间的纠缠的影响也通过实验进行了研究，这在之前没有报道过。当步行器从叠加态开始时，我们表明 DTQW 的属性与从单个位置开始的 DTQW 的属性非常不同。我们的研究结果揭示了 DTQW 的不同特性，并为研究具有任意初始状态的 DTQW 铺平了道路。此外，这种编码方法使得人们能够使用单个物理量子位对任意高维量子态进行编码，并且可以用于实现其他量子信息任务。
The preparation of initial superposition states of discrete-time quantum walks (DTQWs) is necessary for the study and applications of DTQWs. Based on an encoding method, here, we propose a DTQW protocol in linear optics, which enables the preparation of arbitrary initial superposition states of the walker and the coin and enables to obtain the states of the DTQW in addition to the probability distribution of the walker. With this protocol, we experimentally demonstrate the DTQW in the polarization space with both the walker and the coin initially in superposition states, by using only passive linear-optical elements. The effects of the walker’s different initial superposition states on the spread speed of the DTQW and on the entanglement between the coin and the walker are also experimentally investigated, which have not been reported before. When the walker starts with superposition states, we show that the properties of DTQWs are very different from those of DTQWs starting with a single position. Our findings reveal different properties of DTQWs and pave an avenue to study DTQWs with arbitrary initial states. Moreover, this encoding method enables one to encode an arbitrary high-dimensional quantum state, using a single physical qubit, and may be adopted to implement other quantum information tasks.