Entanglement Swapping in Orbit: a Satellite Quantum Link Case Study

TL;DR

This paper analyzes the performance of satellite-based quantum entanglement swapping links, highlighting the impact of satellite-specific challenges like latency and limited quantum memory on the effective communication rate.

Contribution

It introduces a combined analytical and simulation approach to evaluate satellite quantum links, adapting existing tools for satellite-specific conditions.

Findings

Effective rate limited to a few kilohertz due to latency and memory constraints

Validation of models through analytical calculations and event-based simulation

Modified QuISP to better simulate satellite quantum communication scenarios

Abstract

Satellite quantum communication is a promising way to build long distance quantum links, making it an essential complement to optical fiber for quantum internetworking beyond metropolitan scales. A satellite point to point optical link differs from the more common fiber links in many ways, both quantitative (higher latency, strong losses) and qualitative (nonconstant parameter values during satellite passage, intermittency of the link, impossibility to set repeaters between the satellite and the ground station). We study here the performance of a quantum link between two ground stations, using a quantum-memory-equipped satellite as a quantum repeater. In contrast with quantum key distribution satellite links, the number of available quantum memory slots m, together with the unavoidable round-trip communication latency t of at least a few milliseconds, severely reduces the effective average repetition rate to m/t -- at most a few kilohertz for foreseeable quantum memories. Our study uses two approaches, which validate each other: 1) a simple analytical model of the effective rate of the quantum link; 2) an event-based simulation using the open source Quantum Internet Simulation Package (QuISP). The important differences between satellite and fiber links led us to modify QuISP itself. This work paves the way to the study of hybrid satellite- and fiber-based quantum repeater networks interconnecting different metropolitan areas.