China Reports New Record in Quantum Entanglement Transmission
Chinese scientists report the successful transmission of entangled photons between the military's Micius satellite in suborbital space and Earth in a landmark study.
The previous record for a successful quantum entanglement distribution was about 100 kilometers and Chinese scientists reported a transmission over a distance of more than 1,200 km. The distribution of quantum entanglement, especially across vast distances, holds important implications for quantum teleportation and communication networks.
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Efforts to entangle quantum particles, essentially "linking" them together over long distances, have been limited to 100 km or less, mostly because the entanglement is lost as they are transmitted along optical fibers, or through open space on land.
One way to overcome this issue is to break the line of transmission into smaller segments and repeatedly swap, purify and store quantum information along the optical fiber. Another approach to achieving global-scale quantum networks is making use of lasers and satellite-based technologies.
Chinese scientists demonstrated the latter feat using China's Micius military satellite launched last year. Equipped with specialized quantum tools, Micius was used to communicate with three military ground stations across China, each up to around 1,200 km apart.
The separation between the orbiting satellite and these military ground stations varied from 500 km to 2,000 km. A laser beam on the satellite was subjected to a beam splitter, which gave the beam two distinct polarized states.
One of the spilt beams was used for transmission of entangled photons, while the other was used for photon receipt. In this way, entangled photons were received at the separate ground stations, more than 1,000 km apart.
In September 2016, the People's Liberation Army (PLA) that owns Micius established a "quantum channel" with its ground stations. This landmark is an important step in the quest of the PLA to develop ultra secure military communications and quantum encryption systems impervious to hacking by the United States and its allies in a coming war.
The satellite's true military nature is being disguised under the civilian name, Quantum Experiments at Space Scale, or QUESS. Publicly, QUESS is being billed as an international research project in the field of quantum physics.
The PLA plans a network of quantum satellites by 2030 that will augment a ground-based quantum computer network.