Transferring an unknown quantum state over arbitrary distances is essential for large-scale quantum communication and distributed quantum networks. It can be achieved with the help of long-distance quantum teleportation and entanglement distribution. The latter is also important for fundamental tests of the laws of quantum mechanics. Although quantum… (More)
Here, we strictly closed the loopholes by observing a 12 h continuous violation of the Bell inequality and concluded that the lower bound speed of spooky action was 4 orders of magnitude of the speed of light.
Previous attempts • HOM interferometer is demonstrated at laboratory. • HOM interferometer is demonstrated with fiber channels. • In previous free-space quantum experiments, quantum operation was implemented at the transmitter, and then the photons are transmitted to the receiver. • In free space, to the best of our knowledge, no HOM interference has been… (More)
We report a free-space entanglement-based quantum key distribution experiment, implementing the biased basis protocol between two sites which are 15.3 km apart. Photon pairs from a polarization-entangled source are distributed through two 7.8-km free-space optical links. An optimal bias 20:80 between the X and Z basis is used. A post-processing scheme with… (More)
Throughout history, every advance in encryption has been defeated by advances in hacking with severe consequences. In theory, quantum cryptography [1, 2] holds the promise to end this battle by offering unconditional security [3–5] when ideal single-photon sources and detectors are employed. In practice, unfortunately, the battle revives due to the gap… (More)