Hyperentanglement in Nanophotonic Systems with Discrete Rotational Symmetry

TL;DR

This paper introduces a novel method for generating hyperentanglement in nanophotonic systems with discrete rotational symmetry, enabling high-dimensional quantum states for on-chip communication.

Contribution

It presents a new scheme leveraging polygonal-shaped gratings to generate hyperentangled photon states with preserved high-dimensional Hilbert space.

Findings

Coupling photons into surface plasmon polaritons creates finite basis modes.

Encoding spin and orbital angular momentum preserves high-dimensional entanglement.

Phase engineering with polygonal boundary conditions enables hyperentangled state generation.

Abstract

We propose a scheme to generate hyperentanglement between photons carrying angular momentum in nanophotonic systems with discrete rotational symmetry. Coupling free-space photons into surface plasmon polaritons by a polygonal-shaped grating restricts the basis of the generated near-field modes to a finite set, thus creating a new mechanism for spatial mode entanglement. By encoding the incoming photons with spin and orbital angular momenta, we find that the system preserves the high-dimensional Hilbert space, in contrast to rotationally symmetric nanophotonic platforms, where the inseparability of spin and orbital degrees of freedom results in loss of information. We further show that by properly engineering the phase of the photons to conform to the polygonal boundary conditions, we achieve a new scheme for generating hyperentangled states, utilizing both the vector-field nature of the nanophotonic modes and the finite basis of states in polygonal boundary conditions. Our approach paves the way for on-chip quantum communication by expanding the Hilbert space used in computation.