# Saint Louis University simulates thermalization of single- and two-photon states in nonlinear optics

- Published: 2026-11-13 13:59 UTC
- Section: Science › Physics
- Tags: thermalization of quantum light, single-photon states, two-photon states, multimode nonlinear optics, Rayleigh-Jeans distribution, Boltzmann distribution, effective photon interactions, quantum many-body dynamics, Saint Louis University, Max Born Institute
- URL: https://realtech.media/news/rt-1ba70642233689af4b8bbffe_saint_louis_university/

**In simulations, single- and two-photon states travelling with classical light in multimode nonlinear systems thermalized, the authors report. Photons do not interact directly.**

![Saint Louis University simulates thermalization of single- and two-photon states in nonlinear optics](https://realtech.media/media/2026/11/d0489fa42cecb411.jpg)
*NTNU, Faculty of Natural Sciences and Technology, Wikimedia Commons, CC BY 2.0*

A team from Saint Louis University (SLU), the Max Born Institute and Humboldt-Universität zu Berlin has reported numerical experiments in which quantum light thermalizes inside multimode nonlinear optical systems. The work was published in Science Advances. The results are computational; no physical experiment is described. [1]

The authors are Şahin K. Özdemir, Ramy El-Ganainy and Armando Perez-Leija from SLU, Fouad Chahrour from the Max Born Institute and Humboldt University, and Kurt Busch from the Institute of Physics at Humboldt University and the Max Born Institute.

## Quantum light next to a classical field

Photons carry information with high coherence and at the speed of light, but they do not interact with each other directly. The team considered a different arrangement: quantum light propagates alongside relatively intense classical light fields in a multimode nonlinear system. [1]

In the simulations, the nonlinear dynamics of the classical light induced effective quantum interactions between photons. Single- and two-photon states in such systems neither kept their initial state nor simply lost coherence. They thermalized. [1]

## Rayleigh-Jeans and Boltzmann statistics

The thermalization showed up as the emergence of Rayleigh-Jeans and Boltzmann statistical distributions. According to Perez-Leija, the intense classical wave dynamics mediate the interactions and link macroscopic nonlinear optics with microscopic quantum mechanics. [1]

The authors state that the method relies on standard classical optical structures rather than single-photon nonlinear materials, which are difficult to fabricate and scale. In their view, this gives a controllable testbed for open quantum systems and many-body thermodynamics. [1]

The paper also says the approach makes it possible to study a broader range of complex quantum phenomena, including aspects of quantum phase transitions, in readily accessible classical optical settings. [1]

The study is described as peer-reviewed, and its method as computational simulation and modelling. The material does not report photon numbers, system sizes or parameters of the simulated structures.

## Sources

1. [Science Advances](https://doi.org/10.1126/sciadv.aeg6518)
2. [newswise.com](https://www.newswise.com/articles/new-research-bridges-classical-wave-physics-quantum-many-body-dynamics)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-1ba70642233689af4b8bbffe_saint_louis_university/