Quantum enhancement of signal-to-noise ratio for arbitrary coherent states using heralded linear amplifiers

We present an experimental enhancement of signal-to-noise ratio for arbitrary coherent states using a noise-reduced linear amplifier that profitably combines a heralded measurement-based noiseless linear amplifier and a deterministic linear amplifier. The concatenation of two amplifiers introduces the flexibility that allows one to reach the amplification with high gain for large input coherent amplitude. We demonstrate a signal transfer coefficient of Ts = 2.55 ± 0.08 from input to output, achieved with an amplification gain of 10.54. When Gaussian statistics is retained, our heralded amplifier obtained a signal transfer coefficient of Ts = 1.10 ± 0.04. Our amplification scheme only relies on linear optics and post-selection algorithm, and therefore would be of great usage in loss-sensitive quantum information protocols.