Observation of the spin Hall effect of light by a single-photon detector.

We use a single-photon detector to detect the spin Hall effect of light (SHEL) of a quasi-single-photon beam obtained in this Letter. The physics of the spin Hall effect and its quantum weak measurement method with a dimensionless pointer are elucidated through particle number representation. Our weak measurement scheme obviates the necessity of high-resolution single-photon array detectors. Consequently, we have successfully observed the spin Hall effect within a 20 ns temporal window using a position-resolution-independent single-photon detector with remarkably low-noise levels. The weak measurement of the dimensionless pointer presented in this Letter boosts both the detection accuracy and the response speed of the photonics spin Hall effect, thereby contributing significantly to fundamental theoretical research in spin photonics and precise measurements of physical property parameters.