Circular-beam approximation for quantum channels in a turbulent atmosphere

TL;DR

This paper introduces a circular-beam approximation for modeling the probability distribution of transmittance in turbulent atmospheric quantum channels, offering a simpler yet accurate alternative to existing models for quantum communication analysis.

Contribution

The paper presents a novel circular-beam approximation that reduces computational complexity and extends the applicability of PDT models for atmospheric quantum channels.

Findings

The circular-beam approximation matches experimental data well.

It simplifies parameter determination from transmittance moments.

It outperforms the elliptic-beam approximation in certain regimes.

Abstract

The evolution of quantum states of light in free-space channels is strongly influenced by atmospheric turbulence, posing a significant challenge for quantum communication. The transmittance in such channels randomly fluctuates. This effect is commonly described by the probability distribution of transmittance (PDT). The elliptic-beam approximation provides an analytical model for the PDT, showing good agreement with experimental and simulation data within a specific range of channel parameters. In this work, we introduce the circular-beam approximation -- a simplified alternative that offers satisfactory accuracy while significantly reducing computational complexity. Our method naturally leads to a technique for determining the model parameters from the first two moments of the transmittance. This approach eliminates the model misspecification bias inherent in the elliptic-beam approximation and significantly extends the applicability range of the PDT model, providing a practical tool for characterizing atmospheric channels in quantum applications.