Single-photon quantum-info amplifier is noiseless

Nathan, Australia--Physicists have demonstrated the first device capable of amplifying the information in a single photon without adding noise. The research group, which included people from Griffith University, the University of Queensland (Brisbane, Australia), and the University of Science and Technology of China (Hefei, China), was able to amplify the noisy quantum state of a single photon subjected to loss without adding noise in the process; in fact, their amplification reduced the noise in the quantum state.

Team leader Geoff Pryde from Griffith University’s Centre for Quantum Dynamics says the breakthrough would provide a new tool for all sorts of new quantum technologies. “The technique works by combining the noisy quantum state with a ‘clean’ single photon in the amplifier, and using quantum teleportation to transfer the information onto the new photon,” says Pryde. “The most obvious application for this work is in improved quantum cryptography.”

The results may stimulate further interest in the fundamental laws that govern how well amplifiers can work, and in developing uses of noiseless amplification techniques for other quantum information applications.

The next step for the research team will be to build additional quantum teleportation into the experiment, which will make the noiseless amplifier more directly useful for long-distance communication.

The results have been published on the Nature Physics website.