Explicit channels with unbounded gains in classical communication using entangled inputs

2026-09-22

AI Summary

研究通过使用纠缠输入在经典通信中构建了具有无界增益的显式通道，采用确定性qudit Clifford幺正变换结合二进制测量和经典前馈方法。

Abstract

We construct an explicit family of finite-dimensional quantum channels for which the optimal classical communication rate achievable with product-state codewords and collective decoding tends to zero, while rates achievable using entanglement only within pairs of channel inputs grow without bound. Our construction combines deterministic qudit Clifford unitaries with a binary measurement and classical feedforward, providing a derandomization to Hastings' probabilistic construction. The key ingredient is a careful design of measurement and feedforward process that yields the required one-copy and two-copy output entropy bounds from moment estimates alone, without requiring strong convergence of the underlying unitary family.

Problem

• quantum channels
• entangled inputs
• classical communication rate
• product-state codewords
• collective decoding

Innovation

• quantum channels
• entanglement
• classical communication rate
• Clifford unitaries
• feedforward