Continuous variable spin–orbit total angular momentum entanglement on the higher-order Poincaré sphere

Abstract

Optical spin–orbit coupling is an important phenomenon and has fruitful applications. Here, we investigate the spin–orbit total angular momentum entanglement in the optical parametric downconversion process. Four pairs of entangled vector vortex modes are experimentally generated directly using a dispersion- and astigmatism-compensated single optical parametric oscillator, and for the first time, to the best of our knowledge, the spin–orbit quantum states are characterized on the quantum higher-order Poincaré sphere, and the relationship of spin–orbit total angular momentum Stokes entanglement is demonstrated. These states have potential applications in high-dimensional quantum communication and multiparameter measurement.