北京大学古英团队近日研究了单梯度超表面上的量子CZ门。相关论文于2025年5月13日发表在《光：科学与应用》杂志上。

针对片上量子信息中量子光子集成的要求，研究组提出了一种通过单梯度元表面实现量子控制Z（CZ）门的方案。利用其平行分束特性，即一系列具有相同分束比的连接分束器，一个元表面可以支持偏振编码CZ门或路径编码CZ门、几个独立的CZ门和级联CZ门。 

利用输出状态的路径被输入状态的偏振锁定的优点，路径编码CZ门可以有效地滤除来自分束过程的位翻转误差。这些CZ门也有可能检测量子误差，并通过超表面上的多自由度关联产生高维纠缠。通过将量子CZ门集成到单个元表面中，该研究结果为量子器件的高密度和多功能集成开辟了一条道路。

附：英文原文

Title: Quantum CZ gates on a single gradient metasurface

Author: Liu, Qi, Tian, Yu, Tian, Zhaohua, Jia, Yali, Li, Guixin, Ren, Xi-Feng, Gong, Qihuang, Gu, Ying

Issue&Volume: 2025-05-13

Abstract: For the requirement of quantum photonic integration in on-chip quantum information, we propose a scheme to realize quantum controlled-Z (CZ) gates through single gradient metasurface. Using its parallel beam-splitting feature, i.e., a series of connected beamsplitters with the same splitting ratio, one metasurface can support a polarization encoding CZ gate or path encoding CZ gate, several independent CZ gates, and cascade CZ gates. Taking advantage that the path of output state is locked by the polarization of input state, path encoding CZ gates can efficiently filter out bit-flip errors coming from beam-splitting processes. These CZ gates also have the potential to detect quantum errors and generate high-dimensional entanglement through multi-degree-of-freedom correlation on metasurfaces. By integrating quantum CZ gates into a single metasurface, our results open an avenue for high-density and multifunctional integration of quantum devices.

DOI: 10.1038/s41377-025-01871-5

Source: https://www.nature.com/articles/s41377-025-01871-5