This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: An international collaboration demonstrates that classical nonlinear dynamics can drive single- and two-photon states to thermalize, opening new avenues for simulating complex quantum many-body systems within accessible optical architectures. In the modern landscape of quantum physics and optical sciences, photons stand out as the ultimate information carriers.
Possessing exceptional coherence and traveling at the absolute upper physical speed limit, they form the backbone of high-speed data transmission and quantum-enhanced optical technologies. Yet, these advantages are coupled with a fundamental physical limitation: the absence of direct photon-photon interactions. When high-intensity classical light fields propagate through nonlinear optical materials, they undergo mutual and self-interactions, modifying their phase and amplitude via self-phase and cross-phase modulation.
However, translating such multi-wave mixing behavior to the single-photon level is a prohibitively difficult task. Conventional optical media exhibit vanishingly small nonlinear responses at ultralow light intensities, meaning individual photons typically pass right through one another without scattering or interacting. Consequently, generating direct, controllable photon-photon interactions for single- and few-photon states has remained elusive, restricting the exploration of quantum many-body dynamics in optical systems.
Now, in a theoretical study detailed in the paper "Thermalization of quantum light induced by classical nonlinear wave dynamics," an international research team comprising scientists from Saint Louis University (U.S.), the Max Born Institute (Berlin) and Humboldt-Universität zu Berlin has demonstrated that the nonlinear dynamics of classical light can influence single- and two-photon quantum states. Specifically, the team has shown that multimode nonlinear optical platforms can be harnessed to induce effective quantum interactions between photons, subsequently thermalizing them. The paper is published in the journal Science Advances.
To circumvent the weak native nonlinearities of materials at the quantum limit, we investigated scenarios where quantum light propagates alongside relatively intense classical light fields within multimode nonlinear optical systems. Through rigorous numerical experiments, the team revealed that single- and two-photon states embedded in these configurations do not merely maintain their initial states or suffer unmitigated decoherence; instead, they thermalize. This thermalization process is confirmed by the emergence of characteristic statistical distributions, specifically matching Rayleigh-Jeans and Boltzmann distributions.
By leveraging the intense classical wave dynamics to mediate effective interactions, the system successfully bridges the gap between macroscopic nonlinear optics and microscopic quantum mechanics. This approach provides a powerful framework for simulating quantum behaviors that were previously considered practically inaccessible in optical setups. Rather than requiring exotic, ultrastrong single-photon nonlinear materials—which are notoriously difficult to fabricate and scale—the team's method achieves effective quantum thermalization using standard, readily available classical optical structures.
Extract — continue reading at the source.
