2025/07/21 by Khanian, Zahra Baghali, Hirche, Christoph · 2 citations
#FOS: Computer and information sciences #FOS: Physical sciences #Information Theory (cs.IT) #Quantum Physics (quant-ph)
paper · doi:10.48550/arxiv.2507.15661
We establish a strong converse bound for the private classical capacity of anti-degradable quantum channels. Specifically, we prove that this capacity is zero whenever the error ε> 0 and privacy parameter δ> 0 satisfy the inequality δ(1-ε2)(1)/(2)+ε(1-δ2)(1)/(2)<1. This result strengthens previous understandings by sharply defining the boundary beyond which reliable and private communication is impossible. Furthermore, we present a ``pretty simple'' proof of the ``pretty strong'' converse for the quantum capacity of anti-degradable channels, valid for any error ε< (1)/(√(2)). Our approach offers clarity and technical simplicity, shedding new light on the fundamental limits of quantum communication.