China sets long-distance quantum world record

Chinese scientists have set a world record of progress in achieving the transmission of quantum states between two ground stations more than 1,200 kilometers apart via a quantum science experiment satellite, signaling a giant leap towards the construction of a global quantum information processing and communication network.

The experiment was led by Pan Jianwei, a professor of physics at the University of Science and Technology of China, and the related paper co-authored by Pan and his team members was later published in the international journal Physical Review. Letters April 26.

Long-range quantum state transmission (QST), usually achieved by quantum teleportation, is one of the main approaches for building quantum communication networks and an essential requirement for performing multiple quantum information processing tasks. .

Aided by the distribution of long-range quantum entanglement, quantum states can be measured and then restructured to achieve long-range transmission, the transmission distance being theoretically infinite. As the distance and quality of quantum entanglement distribution are affected by channel loss, decoherence and other factors, how to break the transmission distance limit has always been one of the biggest concerns of scientists. .

Using satellite-borne entanglement sources to distribute the entanglement to two distant locations and then preparing and restructuring the quantum states is one of the most feasible ways to achieve long-distance quantum state transmission. . Nevertheless, due to atmospheric turbulence, it is very difficult to measure quantum states based on quantum interference after the propagation of photons in the atmospheric channel.

In previous experiments, since the quantum state transmission producers all owned quantum entanglement sources, it was impossible to use third-party-provided entanglement to achieve prior distribution and follow-up transmission of quantum states. in the real sense.

On August 16, 2016, China launched the world’s first quantum satellite known as Quantum Scale Experiments in Space (QUESS), nicknamed “Micius” after an ancient Chinese philosopher. Only then did the research team first achieve entanglement and distribution between two different stations more than 1,000 kilometers apart, with the Micius platform providing valuable data distribution resources. entanglement for quantum communication experiments.

In order to overcome quantum light interference following long-range turbulent atmospheric transmission, the experimental team developed an optical interferometer with very high stability, thanks to an optical integration bonding technology that can remain stable for a long time without shutting down. active loop.

The technological breakthrough combines the quantum teleportation scheme based on a two-photon path polarization mixed entangled state. Long-distance quantum state transmission between Lijiang Station in southwest China’s Yunnan Province and Delingha Earth Station in northwest China’s Qinghai Province, 1,200 kilometers apart, has finally been verified . In this successful experiment, a total of six typical quantum states were verified and the transmission fidelity exceeded the classical limit.

Source: This news is originally published by cgtn

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