Andrew W. Cross, Ke Li, et al.
Physical Review Letters
Privacy is a fundamental feature of quantum mechanics. A coherently transmitted quantum state is inherently private. Remarkably, coherent quantum communication is not a prerequisite for privacy: there are quantum channels that are too noisy to transmit any quantum information reliably that can nevertheless send private classical information. Here, we ask how much private classical information a channel can transmit if it has little quantum capacity. We present a class of channels Nd with input dimension d2, quantum capacity Q(Nd)≤1, and private capacity P(Nd)=logd. These channels asymptotically saturate an interesting inequality P(N)≤(1/2)[logdA+Q(N)] for any channel N with input dimension dA and capture the essence of privacy stripped of the confounding influence of coherence. © 2014 American Physical Society.
Andrew W. Cross, Ke Li, et al.
Physical Review Letters
Debbie Leung, Graeme Smith
IEEE Trans. Inf. Theory
Jianxin Chen, Toby S. Cubitt, et al.
ISIT 2010
Graeme Smith, Joseph M. Renes, et al.
Physical Review Letters