Quantum teleportation is implemented in urban optical fiber networks

Pan Jianwei, Zhang Qiang and others of the University of Science and Technology of China cooperated with relevant parties to realize the quantum state teleportation between independent quantum sources distributed in pre-entanglement distribution for the first time on the Hefei quantum metro communication test network, laying a solid foundation
for the construction of scalable quantum networks in the future.
The results were published online on September 19 in
Nature Photonics.

Quantum teleportation is an important communication method for transmitting quantum states and is the basis for
scalable quantum networks and distributed quantum computing.
In layman's terms, quantum teleportation is to restore the quantum information of a particle in place A to another particle in place B, and the transmitted object is like an "interstellar crossing"
.
The principle is: the communication parties in distant places first share a pair of entangled particles, one of them will transmit the quantum state particles (generally not related to the entangled particles) and the entangled particles in their hands to distinguish the entangled state, and then inform the other party of the resolution results, and the other party performs corresponding quantum transformation operations
according to the obtained information.
Entangled state predistribution, independent quantum source interference, and pre-feedback are the three elements
of quantum teleportation.
Prior to this, no quantum teleportation experiment in the world had met all of the above requirements
at the same time.

Pan Jianwei's group first cooperated with Tsinghua University to develop a time-phase-entangled photon source suitable for optical fiber network transmission, and then successfully solved the synchronization and interference problems between two independent photon sources by developing picosecond long-range optical synchronization technology and narrowband filtering using fiber Bragg gratings.
Then, an active feedback system was developed to solve the problems of delay and polarization fluctuation caused by long-distance optical fiber and the stability of the experimental system.
Finally, using the superconducting nanowire single-photon detector developed by the Shanghai Microsystem Institute of the Chinese Academy of Sciences, a quantum teleportation experiment
satisfying the above three elements was realized on a 30-kilometer optical fiber of the Hefei quantum metro communication network.

Zhang Qiang said that the existing quantum confidential communication is mainly through the encrypted transmission of classical information through quantum keys, but with the development of technology, the final quantum confidential communication will realize the transmission of quantum information, and quantum teleportation through optical fiber networks is expected to greatly improve the security and strength
of Internet connections.
In addition, if quantum computers come out one day, complex quantum information processing will require quantum teleportation in the metro network to transmit quantum information
.

The experiment was highly praised by the reviewers, saying that it "provides a blueprint for future quantum communication network applications" and that "due to the important role played by quantum teleportation in many quantum communication schemes, such a first experimental verification will be an important milestone
in the development of quantum technology.
" 。 The journal Nature Photonics specially invited international quantum informatics scholar Friedrich Groshans to write an article in the "News Perspective" column at the same time, saying that the work "shows that quantum teleportation at the metro scale is technically feasible, and there is no doubt that many interesting quantum information experiments will be carried out
on this basis in the future.
" ”