Non-classical optimization of entangled photons through complex media

Optimization approaches are ubiquitous in physics. In optics, they are key to manipulating light through complex media, enabling applications ranging from imaging to photonic simulators. In most demonstrations, however, the optimization process is implemented using classical coherent light, leading to a purely classical solution. Here, we introduce the concept of optical non-classical optimization in complex media. We experimentally demonstrate the control and refocusing of non-classical light—namely, entangled photon pairs—through a scattering medium by directly optimizing the output coincidence rate. Importantly, these optimal solutions cannot be obtained with classical light and do not result in a focus for classical light; this is a result of entanglement in the input state. This genuinely non-classical optimization method promises advances in quantum imaging, communication, and optical simulations with non-classical light.