Protecting entanglement of twisted photons by adaptive optics

TL;DR

This paper demonstrates that adaptive optics can effectively mitigate atmospheric turbulence effects on entangled twisted photons, significantly improving the stability and security of quantum communication channels using orbital-angular-momentum states.

Contribution

It introduces an adaptive optics correction method that enhances entanglement preservation of OAM photons in turbulent conditions, extending secure quantum communication capabilities.

Findings

AO reduces crosstalk within and outside the encoding subspace

AO stabilizes entanglement against atmospheric turbulence

Enhances turbulence threshold for secure quantum communication

Abstract

We study the efficiency of adaptive optics (AO) correction for the free-space propagation of entangled photonic orbital-angular-momentum (OAM) qubit states, to reverse moderate atmospheric turbulence distortions. We show that AO can significantly reduce crosstalk to modes within and outside the encoding subspace and thereby stabilize entanglement against turbulence. This method establishes a reliable quantum channel for OAM photons in turbulence, and enhances the threshold turbulence strength for secure quantum communication at least by a factor two.