Entanglement distillation is an essential protocol for long-distance quantum communications1, typically for extending the range of quantum key distribution. In the field of continuous variable quantum information processing, quantum as well as classical information is encoded in the light field quadratures, often in the form of Gaussian states. However, distillation from Gaussian input states has not yet been accomplished. It is made difficult by a prominent no-go theorem stating that no Gaussian operation can distill Gaussian states2,3,4. Here we demonstrate, for the first time, such distillation from Gaussian input states, realized by the implementation of non-Gaussian operations. By subtracting one or two photons, a large gain of entanglement was observed. For two photons, Gaussian-like entanglement was also improved. Other than quantum key distribution, this distilled entanglement can also be used for downstream applications such as high-fidelity quantum teleportation5 and a loophole-free Bell test6,7.
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H.T. acknowledges financial support from the G-COE program, commissioned by the MEXT of Japan.
The authors declare no competing financial interests.
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Takahashi, H., Neergaard-Nielsen, J., Takeuchi, M. et al. Entanglement distillation from Gaussian input states. Nature Photon 4, 178–181 (2010). https://doi.org/10.1038/nphoton.2010.1
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