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arXiv:1010.4575 · Physical Review Letters

Experimental Extraction of Secure Correlations from a Noisy Private State

Krzysztof Dobek, Michał Karpiński, Rafał Demkowicz-Dobrzański, Konrad Banaszek, Paweł Horodecki

Published Jan 18, 2011• 21 citations
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Abstract

We report experimental generation of a noisy entangled four-photon state that exhibits a separation between the secure key contents and distillable entanglement, a hallmark feature of the recently established quantum theory of private states. The privacy analysis, based on the full tomographic reconstruction of the prepared state, is utilized in a proof-of-principle key generation. The inferiority of distillation-based strategies to extract the key is exposed by an implementation of an entanglement distillation protocol for the produced state.

DOI
10.1103/physrevlett.106.030501

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Complete security proofs for quantum communication protocols can be notoriously involved, which convolutes their verification, and obfuscates the key physical insights the security finally relies on. In such cases, for the majority of the community, the utility of such proofs may be restricted. Here, we provide a simple proof of confidentiality for parallel quantum channels established via entanglement distillation based on hashing, in the presence of noise, and a malicious eavesdropper who is restricted only by the laws of quantum mechanics. The direct contribution lies in improving the linear confidentiality levels of recurrence-type entanglement distillation protocols to exponential levels for hashing protocols. The proof directly exploits the security relevant physical properties: measurement-based quantum computation with resource states and the separation of Bell-pairs from an eavesdropper. The proof also holds for situations where Eve has full control over the input states, and obtains all information about the operations and noise applied by the parties. The resulting state after hashing is private, i.e. disentangled from the eavesdropper. Moreover, the noise regimes for entanglement distillation and confidentiality do not coincide: confidentiality can be guaranteed even in situations where entanglement distillation fails. We extend our results to multiparty situations which are of special interest for secure quantum networks.
Complete security proofs for quantum communication protocols can be notoriously involved, which convolutes their verification, and obfuscates the key physical insights the security finally relies on. In such cases, for the majority of the community, the utility of such proofs may be restricted. Here, we provide a simple proof of confidentiality for parallel quantum channels established via entanglement distillation based on hashing, in the presence of noise, and a malicious eavesdropper who is restricted only by the laws of quantum mechanics. The direct contribution lies in improving the linear confidentiality levels of recurrence-type entanglement distillation protocols to exponential levels for hashing protocols. The proof directly exploits the security relevant physical properties: measurement-based quantum computation with resource states and the separation of Bell-pairs from an eavesdropper. The proof also holds for situations where Eve has full control over the input states, and obtains all information about the operations and noise applied by the parties. The resulting state after hashing is private, i.e. disentangled from the eavesdropper. Moreover, the noise regimes for entanglement distillation and confidentiality do not coincide: confidentiality can be guaranteed even in situations where entanglement distillation fails. We extend our results to multiparty situations which are of special interest for secure quantum networks.