Optimizing the physical realization of quantum gates is important to build a quantum computer. The controlled-SWAP gate, also named Fredkin gate, can be widely applicable in various quantum information processing schemes. In the present research, we propose and experimentally implement quantum Fredkin gate in a single-photon hybrid-degrees-of-freedom system. Polarization is used as the control qubit, and SWAP operation is achieved in a four-dimensional Hilbert space spanned by photonic orbital angular momentum. The effective conversion rate of the quantum Fredkin gate in our experiment is (95.4 2.6)%. Besides, we find that a kind of Greenberger–Horne–Zeilinger-like states can be prepared by using our quantum Fredkin gate, and these nonseparale states can show its quantum contextual characteristic by the violation of Mermin inequality. Our experimental design and coding method are useful for quantum computing and quantum fundamental study in high-dimensional and hybrid coding quantum systems.

优化量子门的物理实现对于构建量子计算机很重要。受控交换门，也称为弗雷德金门，可以广泛应用于各种量子信息处理方案。在目前的研究中，我们提出并在单光子混合自由度系统中实验性地实现了量子弗雷德金门。极化用作控制量子位，并且在由光子轨道角动量跨越的四维希尔伯特空间中实现 SWAP 操作。有效转化率我们实验中的量子弗雷德金门是 (95.4 2.6)%。此外，我们发现使用我们的量子 Fredkin 门可以制备一种类格林伯格 - 霍恩 - 赛林格状态，并且这些非分离状态可以通过违反 Mermin 不等式来显示其量子上下文特征。我们的实验设计和编码方法可用于高维和混合编码量子系统中的量子计算和量子基础研究。