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arXiv · 1504.07572

Efficient superdense coding in the presence of non-Markovian noise

Bi-Heng Liu·Xiao-Min Hu·Yun-Feng Huang·Chuan-Feng Li·Guang-Can Guo·Antti Karlsson·Elsi-Mari Laine·Sabrina Maniscalco·Chiara Macchiavello·Jyrki Piilo
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Abstract

Many quantum information tasks rely on entanglement, which is used as a resource, for example, to enable efficient and secure communication. Typically, noise, accompanied by loss of entanglement, reduces the efficiency of quantum protocols. We develop and demonstrate experimentally a superdense coding scheme with noise, where the decrease of entanglement in Alice's encoding state does not reduce the efficiency of the information transmission. Having almost fully dephased classical two-photon polarization state at the time of encoding with concurrence $0.163\pm0.007$, we reach values of mutual information close to $1.52\pm 0.02$ ($1.89\pm 0.05$) with 3-state (4-state) encoding. This high efficiency relies both on non-Markovian features, that Bob exploits just before his Bell-state measurement, and on very high visibility ($99.6\%\pm0.1\%$) of the Hong-Ou-Mandel interference within the experimental set-up. Our proof-of-principle results with measurements on mutual information pave the way for exploiting non-Markovianity to improve the efficiency and security of quantum information processing tasks.

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Bi-Heng Liu, Xiao-Min Hu, Yun-Feng Huang, Chuan-Feng Li, Guang-Can Guo, Antti Karlsson, Elsi-Mari Laine, Sabrina Maniscalco, Chiara Macchiavello, Jyrki Piilo. 2015-04-28. Efficient superdense coding in the presence of non-Markovian noise. https://doi.org/10.1209/0295-5075/114/10005

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