Practical quantum cryptography for secure free-space communications

TL;DR

This paper discusses the development and experimental demonstration of quantum cryptography for secure free-space communications, showing its potential for satellite-based secure key distribution.

Contribution

It presents the first experimental demonstration of quantum key generation over a daylight outdoor atmospheric path and analyzes the feasibility of satellite quantum key distribution.

Findings

Successful quantum key generation over 0.5 km outdoor atmospheric path

Demonstrated feasibility of satellite-based quantum key distribution

Supports secure re-keying between ground stations and satellites

Abstract

Quantum cryptography is an emerging technology in which two parties may simultaneously generate shared, secret cryptographic key material using the transmission of quantum states of light. The security of these transmissions is based on the inviolability of the laws of quantum mechanics and information-theoretically secure post-processing methods. An adversary can neither successfully tap the quantum transmissions, nor evade detection, owing to Heisenberg's uncertainty principle. In this paper we describe the theory of quantum cryptography, and the most recent results from our experimental free-space system with which we have demonstrated for the first time the feasibility of quantum key generation over a point-to-point outdoor atmospheric path in daylight. We achieved a transmission distance of 0.5 km, which was limited only by the length of the test range. Our results provide strong evidence that cryptographic key material could be generated on demand between a ground station and a satellite (or between two satellites), allowing a satellite to be securely re-keyed on orbit. We present a feasibility analysis of surface-to-satellite quantum key generation.