Publications associated with Ultrafast quantum optics and optical metrology

Experimental Observation of Coherent-Information Superadditivity in a Dephrasure Channel.

Physical review letters 125 (2020) 060502-

S Yu, Y Meng, RB Patel, Y-T Wang, Z-J Ke, W Liu, Z-P Li, Y-Z Yang, W-H Zhang, J-S Tang, C-F Li, G-C Guo

We present an experimental approach to construct a dephrasure channel that contains both dephasing and erasure noises and can be used as an efficient tool to study the superadditivity of coherent information. Using a three-fold dephrasure channel, the superadditivity of coherent information is observed, and a substantial gap is found between the zero single-letter coherent information and zero quantum capacity. Particularly, we find that, when the coherent information of n channel uses is zero, with a larger number of channel uses the quantum capacity becomes positive. These phenomena exhibit a more obvious superadditivity of coherent information than previous works and demonstrate a higher threshold for nonzero quantum capacity. Such novel channels built in our experiment also can provide a useful platform to study the nonadditive properties of coherent information and quantum channel capacity.

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