Quantum Internet Closer as Chinese Physicists Forge Entanglement Over Kilometers of Standard Optical Fiber

(ScienceMag) Physicists in China have forged entanglement, over dozens of kilometers of standard optical fiber, marking a long step toward a fully quantum internet.
David Awschalom, a physicist at the University of Chicago. “I’m very impressed that they’ve integrated these various technologies into a full system,” he says. “It’s a beautiful piece of work.”
Entanglement would be key to a fully quantum internet that would let quantum computers of the future communicate with one another and be immune to hacking. If hackers messed with communication, they would spoil the entanglement, revealing their presence.
Now, Xiao-Hui Bao, Jian-Wei Pan, and colleagues at the University of Science and Technology of China, Beijing, have demonstrated entanglement over fiber optic links of up to 50 kilometers.
To make the experiment work, the team had to get several elements just right, Pan says. A major hurdle was avoiding absorption of the photons in the optical fiber. To do that, Pan and colleagues used another laser pulse and a device called a waveguide to stretch the photons’ wavelength 60% to the sweet spot for transmission down a standard optical fiber.