Quantum boomerang effect of light

The quantum boomerang effect is a counterintuitive phenomenon in which a wave packet launched with finite momentum in a disordered medium returns to its origin. However, up to now, the experimental exploration of this boomerang effect remains largely unexplored. Here, we report the observation of this effect with light in an on-chip, one-dimensional (1D) disordered waveguide lattice. After benchmarking the system through Anderson localization, we launch a kinetic light beam into the system and track its center of mass (COM): it first moves away from its starting point, arrives at a maximum-valued point, reverses its direction, and returns to its original position over time, revealing the real-space observation of the photonic quantum boomerang effect. We also show two methods to accelerate and control the return: a symmetric gradient loss and time-varying coupling control to effectively increase the return velocity. Both strategies are realized experimentally and captured by our model. These results establish a controllable photonic platform for boomerang physics and open an avenue for future study in nonlinear and many-photon regimes. Light launched into a disordered photonic chip first drifts, then unexpectedly reverses and returns to its point of origin. This work presents the first real-space observation of this quantum boomerang effect and demonstrates how engineered loss and time-varying couplings can accelerate the return dynamics.