Celebrating its centennial anniversary, the Stern–Gerlach experiment has proven to be one of the cornerstones of quantum mechanics, unravelling the quantized nature of the spin angular momentum, and being used in various applications ranging from matter-wave interferometry to weak measurements. Here we report an analogous all-optical Stern–Gerlach experiment in nonlinear optics, where the frequency of light acts as a pseudospin. We observe the splitting of light into two beams, each comprising a frequency-bin superposition, in the presence of a nonlinear coupling gradient. We further realize the phase-sensitive deflection of a distinct frequency-bin superposition into a single direction. Our work constitutes a frequency-domain all-optical coherent deflection of light, offering large bandwidths, fast switching rates and tunability, which are valuable for both classical and quantum information. Furthermore, our findings serve as experimental proof of concept for the emulation of spin transport phenomena using nonlinear optics.

Stern-Gerlach 实验庆祝其一百周年，已被证明是量子力学的基石之一，它揭示了自旋角动量的量子化性质，并被用于从物质波干涉测量到弱测量的各种应用。在这里，我们报告了非线性光学中类似的全光学 Stern-Gerlach 实验，其中光的频率充当赝自旋。我们观察到在存在非线性耦合梯度的情况下，光分裂成两个光束，每个光束都包含一个频率仓叠加。我们进一步实现了不同频率箱叠加到单个方向的相敏偏转。我们的工作构成了光的频域全光相干偏转，提供大带宽、快速切换速率和可调谐性，这对经典信息和量子信息都很有价值。此外，我们的研究结果可作为使用非线性光学模拟自旋输运现象的实验概念证明。