A classical to quantum optical network link for orbital angular momentum carrying light

TL;DR

This paper demonstrates a hybrid classical-quantum optical network link using orbital angular momentum (OAM) of light, enabling conversion and entanglement across classical and quantum channels at telecom wavelengths.

Contribution

It introduces a novel method to connect classical and quantum optical networks via OAM conservation, utilizing sum frequency generation and spontaneous parametric down conversion.

Findings

Successful up-conversion of OAM beams at telecom wavelength

Generation of non-degenerate OAM-entangled photon pairs

Verification of high OAM entanglement in two-dimensional subspaces

Abstract

Light with orbital angular momentum (OAM) has great potentials in both classical and quantum optical communications such as enhancing the transmission capacity of a single communication channel because of its unlimited dimensions. Based on OAM conservation in second order nonlinear interaction processes, we create a classical to quantum optical network link in OAM degree of freedoms of light via sum frequency generation (SFG) following by a spontaneous parametric down conversion (SPDC). A coherent OAM-carrying beams at telecom wavelength 1550nm is up-converted to 525.5nm OAM-carrying beams in the first crystal, then up-converted OAM-carrying beam is used to pump a second crystal to generate non-degenerate OAM entangled photon pairs at 795nm and 1550nm. By switching the OAM carries by the classical party, the OAM correlation in the quantum party is shifted. High OAM entanglements in two dimensional subspaces are verified. This primary study enables to build a hybrid optical communication network contains both classical and quantum optical network nodes.