Combating errors in propagation of orbital angular momentum modes of light in turbulent media

TL;DR

This paper identifies invariants in the propagation of orbital angular momentum modes through turbulent media and develops quantum error correction methods to preserve information without entanglement.

Contribution

It introduces a framework for error-immune information transfer in OAM modes and constructs quantum error correction codes for idealised crosstalk channels.

Findings

Invariants enable error-immune information encoding in turbulent media.

Coherence persists longer than entanglement in turbulence.

Error correction codes work without multiparty entanglement.

Abstract

There is a wealth of simulation, experimental and analytical studies on propagation of orbital angular momentum (OAM) modes through atmospheric and oceanic turbulence.} Using the data of these studies and generalising the framework proposed in [Bala et al., [arXiv:2208.04555] for error-immune information transfer, we accomplish two tasks. First, we identify invariants for propagation of OAM modes through atmospheric and oceanic turbulence, in which error-immune information can be encoded. A closer look at the data reveals two universal features: (i)coherence lasts for a much longer distance in turbulence than entanglement, and, (ii) the crosstalk among different OAM modes depends very weakly on the initial OAM mode index in the weak turbulence regime. Keeping these in mind, we next develop a method for combating errors in what we call an idealised crosstalk channel. In an idealised crosstalk channel, the crossover probabilities are independent of the initial mode index (IMI). We lay down a procedure that allows to retrieve full information in a state by identifying invariant quantities. Finally, we construct quantum error correction and rejection codes for idealised crosstalk channels, without any need for multiparty entanglement.