Programmable control of the spatiotemporal quantum noise of light

Understanding and controlling multimode nonlinear photonic systems is crucial for applications like high-power fiber lasers, optical communications, mode-locked lasers, wavefront shapers, and physical neural networks. So far, the focus has been on controlling the average (so-called "mean-field") properties of light: those described by the classical Maxwell equations. At the same time, the statistical properties of light are of both fundamental interest and potential practical importance for the applications above. Specifically, quantum noise sets fundamental limits on applications (e.g., imaging, communications, and interferometry). Overcoming such limits requires generating quantum states of light, such as squeezed or entangled states, as enabled by second- and third-order nonlinear media.

In this seminar, we will show theoretically that in multimode nonlinear systems (natural experimental platforms include nonlinear waveguide arrays and multimode fibers), the noise distribution across output modes depends strongly on initial conditions, i.e., the input light's phase and amplitude. We predict that controlling the initial conditions enables the generation of squeezed light at high powers, even with a noisy laser across various photonic platforms.

Motivated by this, we conducted a proof-of-principle experiment demonstrating the feasibility of our approach. We shape the wavefront of a pulsed laser using a spatial light modulator and couple the beam into a multimode fiber. At the fiber output facet, we measure the spatial distributions of intensity and intensity noise. We show that by selecting the appropriate phase pattern at the spatial light modulator, we can minimize intensity noise at a specific point in the beam while keeping the average intensity fixed.