Maximal Privacy without Coherence
Author(s)Leung, Debbie W.; Li, Ke; Smith, Graeme; Smolin, John A.
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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 N[subscript d] with input dimension d[superscript 2], quantum capacity Q(N[subscript d]) ≤ 1, and private capacity P(N[subscript d])= log d. These channels asymptotically saturate an interesting inequality P(N) ≤ (1/2)[log d[subscript A] + Q(N)] for any channel N with input dimension d[subscript A] and capture the essence of privacy stripped of the confounding influence of coherence.
DepartmentMassachusetts Institute of Technology. Center for Theoretical Physics; Massachusetts Institute of Technology. Laboratory for Nuclear Science
Physical Review Letters
American Physical Society
Leung, Debbie, Ke Li, Graeme Smith, and John A. Smolin. "Maximal Privacy without Coherence." Phys. Rev. Lett. 113, 030502 (July 2014). © 2014 American Physical Society
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