2017/01/12 by Hao–Chung Cheng, Min-Hsiu Hsieh, Cheng, Hao-Chung +1 · 1 citation
Engineering · Computer Science · #Wireless Communication Security Techniques #Quantum Computing Algorithms and Architecture #Quantum Information and Cryptography
paper · pdf · doi:10.48550/arxiv.1701.03195
In this work, we study the tradeoffs between the error probabilities of classical-quantum channels and the blocklength n when the transmission rates approach the channel capacity at a rate slower than 1/√(n), a research topic known as moderate deviation analysis. We show that the optimal error probability vanishes under this rate convergence. Our main technical contributions are a tight quantum sphere-packing bound, obtained via Chaganty and Sethuraman's concentration inequality in strong large deviation theory, and asymptotic expansions of error-exponent functions. Moderate deviation analysis for quantum hypothesis testing is also established. The converse directly follows from our channel coding result, while the achievability relies on a martingale inequality.