Maximal Privacy without Coherence
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 never...
| Main Authors: | , , , |
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| Other Authors: | |
| Format: | Article |
| Language: | English |
| Published: |
American Physical Society
2014
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| Online Access: | http://hdl.handle.net/1721.1/88610 https://orcid.org/0000-0002-3944-8449 |
| Summary: | 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. |
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