Abstract
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 with input dimension , quantum capacity , and private capacity . These channels asymptotically saturate an interesting inequality for any channel with input dimension and capture the essence of privacy stripped of the confounding influence of coherence.
- Received 7 February 2014
DOI:https://doi.org/10.1103/PhysRevLett.113.030502
© 2014 American Physical Society