Simultaneous Decoding of Classical Coset Codes over 3-User Quantum Interference Channel : New Achievable Rate Regions
This work provides a new achievable rate region for multi-user quantum communication, advancing the theoretical understanding of quantum interference channels.
The paper derives a new inner bound to the capacity region of a 3-user classical-quantum interference channel that subsumes all known inner bounds and is strictly larger for identified examples, including non-commutative additive and non-additive cases.
We undertake a Shannon theoretic study of the problem of communicating bit streams over a 3-user classical-quantum interference channel (3-CQIC) and focus on characterizing inner bounds. We design a new coding strategy based on (i) coset codes possessing algebraic closure properties and (ii) decoding POVMs to decode bi-variate interference efficiently. Needing to perform simultaneous decoding, we enhance Sen's powerful technique of tilting, smoothing, and augmentation - originally designed only for IID codes - to decode into `functions of codebooks'. Developing analysis techniques to combine all of these elements, we derive a new inner bound to the capacity region of a 3-CQIC. The derived inner bound subsumes all currently known inner bounds and is analytically proven to be strictly larger for identified examples, including non-commutative `additive' and `non-additive' ones.