Topological robustness of orbital angular momentum entanglement in stochastic channels

TL;DR

This paper reveals a topological property of orbital angular momentum entanglement that remains robust in stochastic channels like atmospheric turbulence, even when the entanglement itself degrades.

Contribution

It uncovers a topological invariant in OAM entanglement that is resilient to noise, providing a new approach to preserving quantum information in turbulent environments.

Findings

OAM topological observable is preserved under turbulence.

Topological robustness applies to mixed states despite decoherence.

The approach can extend to other spatial degrees of freedom.

Abstract

Orbital angular momentum (OAM) entanglement gives access to multiple qubit and high dimensional Hilbert spaces, but is unfortunately susceptible to disturbance, decaying in real-world noisy channels. Here, we show there is an underlying topology arising from OAM entanglement that is robust to such channels, which we demonstrate using atmospheric turbulence -- exemplary of stochastic or chaotic media. Using a quantum channel with various turbulence strengths, we find the OAM topological observable preserved even though the OAM itself is shown to be highly sensitive to the turbulence. We show this is true for mixed states too, with the OAM topology intact even as the purity of the state decreases due to decoherence. Our work offers a new perspective on OAM entanglement preservation, and may easily be extended to other spatial bases, degrees of freedom, as well as complex channels, whether static or dynamic.