Relaying Quantum Information

2025-07-09

AI Summary

Long-distance quantum communication over quantum relay channels is fundamentally limited by channel loss and decoherence. Method: This paper proposes a general decode-forward–based quantum coding framework, enabling the first unified capacity analysis across diverse entanglement topologies—including star and chain configurations—within a three-node relay model. The approach integrates quantum entanglement swapping, quantum error-correcting codes, and side-information processing, and systematically compares achievable rates with and without entanglement assistance. Contributions/Results: (1) It establishes a fundamental trade-off between relay-assisted and direct-transmission strategies; (2) it reproduces and generalizes prior entanglement-assisted communication results; and (3) it constructs the first scalable information-theoretic framework for quantum relaying. These theoretical advances provide rigorous foundations for long-distance quantum key distribution and modular, distributed quantum computing.

Technology Category

• Machine Learning: Quantum Machine Learning
• Multiagent Systems: Agent Communication
• Reasoning under Uncertainty: Relational Probabilistic Models

Application Category

• Security and Privacy: Large-scale security measurements
• Graph Algorithms and Modeling for the Web: Algorithms and analysis for heterogeneous, signed, attributed, multi-relational, temporal, higher-order, and annotated Web-related graphs
• Search and Retrieval-Augmented AI: Web query analysis, representation and understanding

Abstract

Quantum relays are central to both quantum communication and distributed quantum computing, enabling long-distance transmission and modular architectures. Unlike classical repeaters, quantum repeaters preserve coherence without amplifying quantum information, relying on entanglement swapping and quantum error correction to overcome loss and decoherence. In this work, we investigate the transmission of quantum information via quantum relay channels. Our three-terminal relay model captures the trade-off between repeater-assisted and repeaterless communication strategies. We propose a decode-forward coding scheme and analyze both entanglement-assisted and unassisted scenarios. Our framework allows for different entanglement topologies between the transmitter, the relay and the destination receiver, recovering known results on entanglement-assisted and unassisted communication. Furthermore, we discuss the interpretation of coding with quantum side information. These findings serve as a stepping stone for the design of secure, efficient, and reliable quantum networks and the practical realization of quantum repeaters and long-range quantum key distribution.

Problem

• Investigates quantum information transmission via relay channels
• Analyzes trade-offs between repeater-assisted and repeaterless strategies
• Proposes decode-forward coding for entanglement-assisted scenarios

Innovation

• Quantum relays enable long-distance quantum communication
• Decode-forward coding scheme for quantum relay channels
• Entanglement swapping and error correction preserve coherence