AsianScientist (Nov. 4, 2016) – Scientists in Australia have produced near-perfect clones of quantum information using a new method to surpass previous cloning limits. Their work was published in Nature Communications.

A global race is on to use quantum physics for ultra-secure encryption over long distances, according to Professor Ping Koy Lam, node director of the Center for Quantum Computation and Communication Technology (CQC2T) at Australia National University. Using a new cloning method of high-performance optical amplifiers to clone light encoded with quantum information, it is now possible to allow quantum encryption to be implemented with existing fiber optic infrastructure.

The laws of physics—in particular the ‘No Cloning Theorem’—prevent high quality clones being produced with a 100 percent success rate. The research team, led by Professor Lam, uses a probabilistic method to demonstrate that it’s possible to produce clones that exceed theoretical quality limits. The method was initially proposed by CQC2T researchers led by Professor Timothy Ralph at University of Queensland.

“Imagine Olympic archers being able to choose the shots that land closest to the target’s centre to increase their average score,” said Ralph. “By designing our experiment to have probabilistic outputs, we sometimes ‘get lucky’ and recover more information than is possible using existing deterministic cloning methods. We use the results closest to a ‘bullseye’ and discard the rest.”

A distinct difference between archery and quantum information is that the probabilistic method is permitted, and is useful in many crypto-communication situations, such as generating secret keys.

“At the heart of the demonstration is a ‘noiseless optical amplifier,'” explained Ralph. “When the amplification is good enough, we can then split a light beam into clones. ‘Amplify-then-split’ allows us to clone the light beam with minimal distortion, so that it can still be read with exquisite precision.”



The article can be found at: Haw et al. (2016) Surpassing the No-cloning Limit with a Heralded Hybrid Linear Amplifier for Coherent States.

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Source: Australian National University.

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