Same, But Not Really

A new study has experimentally demonstrated a quantum fingerprinting protocol and shown that it can surpass the classical limit for solving communication complexity problems. Scientists say that in these problems, two parties each have a message, and they both share some of their message with a referee, who has to decide whether the two messages are the same or not. The classical limit requires that a minimum amount of information must be transmitted between each party and the referee in order for the referee to make this decision.

Researchers found that the best communication complexity protocols require transmission of data that is two orders of magnitude larger than the classical limit.

It was shown that quantum fingerprinting can transmit less information, up to 84% less, than classical limit. The results set a new record for transmitting the smallest amount of information for any type of communication complexity protocol.

"For the first time, we have demonstrated the quantum advantage over classic information processing in communication complexity," coauthor Qiang Zhang, a physicist at the University of Science and Technology of China and the Jinan Institute of Quantum Technology, told

Image source: Guan et al. ©2016 American Physical Society

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Researchers tested the new protocol to transmit 2-Gbit video files over a 20-km fiber. By transmitting only the information contained in the files' quantum fingerprints, this task requires transmitting only about 1300 photons, which is 14% less information than that required by the classical limit.

The results of the study could lead to a wide variety of applications in quantum communications, in particular the potential for the development of "green" (low-energy) communication methods. It can also be used to test the foundations of quantum physics, since quantum fingerprinting involves quantum phenomena such as non-locality, which is related to quantum entanglement.

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