Spin and Orbital Rotation of Electrons and Photons via Spin-Orbit Interaction

TL;DR

This paper demonstrates a universal spin-orbit interaction in electrons and photons within waveguides, revealing novel rotational effects and enabling reversible entanglement transfer between spin and orbital angular momentum.

Contribution

It introduces a unified description of spin-orbit interaction for electrons and photons, predicting new rotational phenomena and applications in entanglement manipulation.

Findings

Spin and orbital angular momentum interact in waveguides.

Novel rotational effects depend on the sign of OAM or SAM.

Reversible entanglement transfer between SAM and OAM.

Abstract

We show that when an electron or photon propagates in a cylindrically symmetric waveguide, its spin angular momentum (SAM) and its orbital angular momentum (OAM) interact. Remarkably, we find that the dynamics resulting from this spin-orbit interaction are quantitatively described by a single expression applying to both electrons and photons. This leads to the prediction of several novel rotational effects: the spatial or time evolution of either particle's spin/polarization vector is controlled by the sign of its OAM quantum number, or conversely, its spatial wavefunction is controlled by its SAM. We show that the common origin of these effects in electrons and photons is a universal geometric phase. We demonstrate how these phenomena can be used to reversibly transfer entanglement between the SAM and OAM degrees of freedom of two-particle states.