Observation of anomalous classical-to-quantum transitions in many-body systems

The correspondence principle bridges the quantum and classical worlds by establishing a direct link between their dynamics. This well-accepted tenant of quantum physics has been explored in quantum systems wherein the number of particles is increased to macroscopic scales. However, theoretical investigations of nanoscale structures have revealed discrepancies when attempting to bridge classical and quantum physics. Here, we report on the experimental observation of anomalous classical-to-quantum transitions in open many-body optical systems. We demonstrate, for the first time, the lack of classical-to-quantum correspondence between a macroscopic optical system and its constituent quantum multiphoton subsystems. In contrast to common belief, we demonstrate that the coherence dynamics of many-body quantum subsystems with up to forty particles can indeed be opposite to that exhibited by the hosting macroscopic system. By employing complex-Gaussian statistics, we show that these effects are universal for open many-body systems. Consequently, our work can have important implications for other fields of physics ranging from condensed matter to nuclear physics.