Classical Feedback in a Quantum Network

2025-09-19

AI Summary

This work investigates how classical feedback enhances communication capacity in quantum multiple-access channels (MACs), aiming to circumvent limitations imposed by the quantum no-cloning theorem on state replication. Methodologically, it introduces the first feedback communication framework for quantum MACs by performing joint measurements at the receiver and generating classical feedback signals—thereby generalizing both the classical Cover–Leung region and the generalized feedback region to the quantum setting. Using superposition block Markov coding and a quantum multi-user lemma, the authors derive a new achievable rate region. Theoretically, they prove that even with purely classical feedback, the capacity of the quantum binary adder MAC strictly exceeds its no-feedback capacity. This work establishes foundational theoretical support and a concrete architectural blueprint for feedback-enhanced communication in quantum networks.

Technology Category

• Machine Learning: Quantum Machine Learning
• Multiagent Systems: Agent Communication
• Search and Optimization: Learning to Search

Application Category

• Security and Privacy: Large-scale security measurements
• Search and Retrieval-Augmented AI: Web evaluation methodologies and metrics
• Semantics and Knowledge: Methods to enhance, augment, integrate or synergize semantic models such as knowledge graphs and LLMs

Abstract

Classical communication over a quantum multiple access channel (MAC) is considered. Since the no-cloning prohibits universal copying of arbitrary quantum states, classical feedback is generated through measurement. An achievable rate region is derived using superposition block Markov coding and a quantum multiparty lemma for the analysis. Our region generalizes both the classical Cover-Leung region and the generalized feedback region. As an example, we show that the quantum binary adder MAC can benefit from feedback.

Problem

• Classical communication over quantum multiple access channels
• Deriving achievable rate region using superposition coding
• Showing quantum binary adder MAC benefits from feedback

Innovation

• Superposition block Markov coding technique
• Quantum multiparty lemma for analysis
• Measurement-generated classical feedback approach