Atmospheric Channel Characteristics for Quantum Communication with Continuous Polarization Variables

TL;DR

This study examines the atmospheric channel for free-space quantum communication using continuous polarization variables, demonstrating its suitability under various weather conditions with detailed analysis of channel influences.

Contribution

The paper provides an experimental analysis of atmospheric effects on polarization-based quantum communication over a 100m free-space link, highlighting the system's robustness and autocompensation capabilities.

Findings

Channel is suitable for most weather conditions

Atmospheric fluctuations are autocompensated in the setup

Daylight operation is feasible due to LO filtering

Abstract

We investigate the properties of an atmospheric channel for free space quantum communication with continuous polarization variables. In our prepare-and-measure setup, coherent polarization states are transmitted through an atmospheric quantum channel of 100m length on the roof of our institute's building. The signal states are measured by homodyne detection with the help of a local oscillator (LO) which propagates in the same spatial mode as the signal, orthogonally polarized to it. Thus the interference of signal and LO is excellent and atmospheric fluctuations are autocompensated. The LO also acts as spatial and spectral filter, which allows for unrestrained daylight operation. Important characteristics for our system are atmospheric channel influences that could cause polarization, intensity and position excess noise. Therefore we study these influences in detail. Our results indicate that the channel is suitable for our quantum communication system in most weather conditions.