Noise-immune quantum correlations of intense light

Lasers with high intensity generally exhibit strong intensity fluctuations far above the shot-noise level. Taming this noise is pivotal to a wide range of applications, both classical and quantum. Here we demonstrate the creation of intense light with quantum levels of noise even when starting from inputs with large amounts of excess noise. In particular, we demonstrate how intense squeezed light with intensities approaching 0.1 TW cm⁻², but noise at or below the shot-noise level, can be produced from noisy inputs associated with high-power amplified laser sources (an overall noise reduction of 30-fold). On the basis of a new theory of quantum noise in multimode systems, we show that the ability to generate quantum light from noisy inputs results from multimode quantum correlations, which maximally decouple the output light from the dominant noise channels in the input light. As an example, we demonstrate this effect for femtosecond pulses in nonlinear fibres, but the noise-immune correlations that enable our results are generic to many other nonlinear systems in optics and beyond.