A Fundamental Inequality for Lower-bounding the Error Probability for Classical and Quantum Multiple Access Channels and Its Applications
This paper develops a new fundamental inequality for bounding error probabilities in classical and quantum multiple access channels (MACs). It establishes a core theorem based on three distinct settings, leading to extensions of Yagi-Oohama and Poor-Verdú bounds across various access scenarios. The results are crucial for deriving capacity region constraints in both classical and quantum MAC systems.