Characterization of free-space quantum channels

TL;DR

This paper models the statistical properties of free-space quantum channels affected by atmospheric turbulence, providing insights crucial for designing secure quantum communication systems over large distances.

Contribution

It derives comprehensive probability distributions of transmittance considering various atmospheric effects, enhancing the understanding of free-space quantum channel behavior.

Findings

Derived PDT models for different turbulence conditions

Analyzed effects of beam wandering and deformation

Suggested strategies for improving channel transmission

Abstract

Many fundamental and applied experiments in quantum optics require transferring nonclassical states of light through large distances. In this context the free-space channels are a very promising alternative to optical fibers as they are mobile and enable to establish communications with moving objects, using satellites for global quantum links. For such channels the atmospheric turbulence is the main disturbing factor. The statistical properties of the fluctuating transmittance through the turbulent atmosphere are given by the probability distribution of transmittance (PDT). We derive the consistent PDTs for the atmospheric quantum channels by step-by-step inclusion of various atmospheric effects such as beam wandering, beam broadening and deformation of the beam into elliptic form, beam deformations into arbitrary forms. We discuss the applicability of PDT models for different propagation distances and optical turbulence strengths in the case when the receiver module has an annular aperture. We analyze the optimal detection and correction strategies which can improve the channel transmission characteristics. The obtained results are important for the design of optical experiments including postselection and adaptive strategies and for the security analysis of quantum communication protocols in free-space.