A high-fidelity noiseless amplifier for quantum light states

Noise is the price to pay when trying to clone or amplify arbitrary quantum states. However, the quantum noise associated with linear phase-insensitive amplifiers can be avoided by relaxing the requirement of a deterministic operation. Here we present the experimental realization of a novel concept of a probabilistic noiseless linear amplifier that is able to amplify coherent states at the highest levels of effective gain and final state fidelity ever reached. Based on a sequence of photon addition and subtraction, this high-fidelity amplification scheme is likely to become an essential tool for applications of quantum communication and metrology.