Photonic spin Hall effect (SHE) is a fundamental and important optical phenomenon, which originates from the spin–orbit interactions (SOI) of light, forming the cornerstone for a wide range of optical precision measurements. However, the wave function collapse in the single-photon SHE is unpredictable as spin collapse has inherent randomness governed by the Born rule. Here, nonlocal spin bunching and anti-bunching of polarization-entangled photon pairs called two-photon SHE is realized to predict and manipulate the wave function collapse, which is fundamentally different from the single-photon SHE. The two-photon SHE is sensitive to the relative phase among entangled photon pairs, enabling continuous control from nonlocal spin bunching to anti-bunching. Owing to the phase sensitivity of the two-photon SHE, an accurate and simple quantitative phase imaging scheme is realized. The two-photon SHE may pave the way for unveiling the wave function evolution in the SOI of light and manipulating spin-dependent photonic quantum effects.
Photonic spin Hall effect (SHE) is a fundamental and important optical phenomenon, which originates from the spin–orbit interactions (SOI) of light, forming the cornerstone for a wide range of optical precision measurements. However, the wave function collapse in the single-photon SHE is unpredictable as spin collapse has inherent randomness governed by the Born rule. Here, nonlocal spin bunching and anti-bunching of polarization-entangled photon pairs called two-photon SHE is realized to predict and manipulate the wave function collapse, which is fundamentally different from the single-photon SHE. The two-photon SHE is sensitive to the relative phase among entangled photon pairs, enabling continuous control from nonlocal spin bunching to anti-bunching. Owing to the phase sensitivity of the two-photon SHE, an accurate and simple quantitative phase imaging scheme is realized. The two-photon SHE may pave the way for unveiling the wave function evolution in the SOI of light and manipulating spin-dependent photonic quantum effects.
Using the sensitivity of atomic transitions on the polarizations of pump fields in multi-Zeeman-sublevel atomic systems, we show the polarization-direction-dependent anisotropic susceptibility of atoms that yields the strong coupling between the spin and the transverse momentum of light, i.e., spin–orbit interaction (SOI). Moreover, we also show that the spin-Hall effect of light can be obtained due to SOI. It can be controlled via the orientation of the anisotropy and frequency of light, and substantially enhanced up to several micrometers, which could be easily observed in experiment.
The photonic Spin Hall Effect (SHE) causes a polarization dependent transverse shift of light at an interface. In this paper, we theoretically investigate the microwave controlled photonic SHE and microwave electrometry in a closed-loop Λ-type atomic system. At zero probe detuning (Δp=0) and relative phase φ=0,π, the photonic SHE magnitude remains at the intrinsic finite beam saturation limit w0/2, whereas the microwave field shifts its angular position linearly with opposite slopes (signs) for the two phases, enabling differential microwave electric field sensing. At φ=π/2, the photonic SHE magnitude decays exponentially with Ωμ, providing weak microwave electric field sensing. In contrast, at Δp=±Ωc (control field coupling), the photonic SHE reaches a maximum of half the incident beam waist when Ωμ≥Ωp and the phase φ is optimized. Interestingly, we observed microwave controlled switching of photonic SHE by tuning the relative phase φ at an optimized value of Ωμ and Ωc. Our results may have potential applications in microwave quantum sensing and quantum optical switches based on the photonic SHE.
Abstract We present a theoretical study demonstrating that the photonic spin Hall effect (PSHE) can be both actively tuned and greatly amplified by exploiting the nonlocal, nonlinear optical response of a strongly interacting Rydberg gas operating under electromagnetically induced transparency. Rather than relying on fixed phase metasurfaces or conventional Kerr materials, long range interactions between Rydberg atoms create a spatially extended, intensity dependent refractive index profile that enables dynamic spin resolved beam deflection. In a glass–Rydberg–glass trilayer model, we show that the PSHE displacement can be varied smoothly in magnitude and even reversed in sign by adjusting atomic density, probe intensity, laser detunings, and interaction strength. This nonlocal nonlinearity transforms the typically weak PSHE into a macroscopically observable and dynamically controllable effect. Our results establish a versatile platform for reconfigurable spin-dependent photonic control, with potential applications in high-sensitivity optical metrology, spin-based beam steering, and tunable quantum-optical information processing.
Optical spin-orbit interactions (SOI), demonstrated experimentally in optical cavities, enable the polarization degrees of freedom of light to be described and controlled as an effective pseudospin, providing a foundation for spintronic-like control of light and the development of next-generation optical technologies. However, prior works describe this emergent effect using phenomenological models that fail to uncover its microscopic quantum origins, and as a result, a rigorous connection between material electronic structure and the optical SOI remains elusive. In this work, we address this fundamental challenge by developing a microscopic quantum theory starting from the non-relativistic quantum electrodynamical (QED) description of light-matter interactions. We show that this effect arises from virtual interactions between confined photons and material excitations. Crucially, our theoretical framework provides microscopic material-design principles for tuning the distinct components of optical SOI, which include the optical birefringence, photonic self-energies, TE-TM splitting, and optical Zeeman splitting, enabling precise engineering of effective magnetic fields, diabolical points, and pseudospin textures. We anticipate that the predictive capability of our microscopic theory will enable systematic screening and design of material systems for photonic spintronics and optical technologies.
We theoretically investigate the transverse photonic spin Hall effect (PSHE) in a cavity structure containing a double-tripod (DT) atomic medium. We show that the internal topology of the double-tripod system can be coherently reconfigured through the relative phase of the control fields and the two-photon detuning, leading to qualitatively distinct effective configurations. These structural transformations reshape the transparency bandwidth, absorption spectrum, and dispersive slope, which in turn govern the spin-dependent reflection phase responsible for the PSHE. We demonstrate that large transverse shifts emerge in low-loss dispersive windows and are strongly enhanced near the Brewster angle due to the sensitive dependence of the reflection phase on the optical response. The magnitude, spectral range, and even sign of the spin-dependent displacement can be reversibly tuned by adjusting the phase, detuning, and atomic density. Our results reveal that cavity-assisted DT media provide a reconfigurable platform in which internal quantum interference directly maps to controllable spin–orbit photonic transport.
Abstract The photonic spin Hall effect (SHE) is explored in a highly tunable Rydberg‐based atomic system by leveraging the distinctive properties of Rydberg superatoms. These superatoms arise from strong dipole–dipole interactions and extended radiative lifetimes, resulting in collective excitations governed by the dipole blockade mechanism. An ensemble of three‐level atoms in a cascade configuration models a medium in which each superatom acts as a coherent quantum entity. The photonic SHE shows strong dependence on the probe field Rabi frequency and atomic number density. At high Rabi frequencies, the blockade effect suppresses the photonic SHE, confining its occurrence to specific resonant conditions. In contrast, under weak probe excitation, the blockade influence diminishes, enabling an amplified photonic SHE response at resonant detuning due to increased light‐matter interaction sensitivity. Reducing atomic number density further broadens the detuning range over which the photonic SHE occurs, indicating a transition toward a more sensitive, less resonance‐constrained optical behavior. The effect of van der Waals interactions on the photonic SHE shift is also characterized. This expanded operational bandwidth demonstrates the potential of Rydberg‐based systems for robust spin‐optical control, particularly in scenarios where precise stabilization of the probe field frequency is experimentally challenging.