• A new synthetic-dimension platform based on fast-gain lasers enables the study of collective quench dynamics in active photonic lattices.
• The platform demonstrates robust coherent oscillations in the presence of complex dispersion and dissipation due to the liquid phase of light enabled by fast gain.
• The system's dynamics involve three distinct timescales: Bloch oscillations, dispersion/dissipation effects, and fast-gain recovery, influencing the system's stability and coherence.

Researchers have created a novel photonic emulator platform using modulated fast-gain ring lasers to investigate the flow of liquid light in synthetic dimensions. This platform allows for the emulation of quench dynamics within a synthetic photonic lattice with equal densities across the reciprocal space. By applying an artificial electric field and introducing a slow timescale through Bloch oscillations, the study reveals coherent oscillations facilitated by fast gain, despite dispersion and dissipation. Furthermore, quenching a steady state to an uncoupled system uncovers coherent interactions between decaying modes, highlighting the liquid state of light's role in suppressing fluctuations and enriching the understanding of collective dynamics in the non-perturbative regime.

• What: Investigation of collective quench dynamics in active photonic lattices using a synthetic-dimension platform based on fast-gain saturation in real space, leading to a liquid phase of light.
• Who: Researchers from the Institute of Quantum Electronics, ETH Zürich; Department of Physics, University of Konstanz; including Alexander Dikopoltsev, Ina Heckelmann, Mathieu Bertrand, Mattias Beck, Giacomo Scalari, Oded Zilberberg, and Jérôme Faist.
• When: Experiment conducted and results published in 2025, with the article received on June 11, 2024, accepted on March 17, 2025, and published on May 1, 2025.
• Where: Research conducted at the Institute of Quantum Electronics, ETH Zürich, Zurich, Switzerland, and the Department of Physics, University of Konstanz, Konstanz, Germany.

This research presents a significant advancement in the field of photonic emulation, offering a novel platform to study complex quantum phenomena. The use of fast-gain lasers to create a liquid phase of light enables the observation of collective behaviors that are typically challenging to investigate. The ability to manipulate the lattice dynamics with artificial electric fields and observe coherent oscillations despite dispersion and dissipation opens new avenues for understanding non-equilibrium dynamics in crystals. The identified timescales provide a framework for controlling and optimizing the system's behavior. The comparison to cold atomic experiments and the analogy to the Pauli exclusion principle highlight the potential of this platform to emulate solid-state phenomena and inspire new photonic devices.

The development of this synthetic-dimension platform provides a powerful tool for exploring collective quench dynamics in active lattices. By leveraging fast-gain saturation to create a liquid phase of light, the researchers demonstrated robust coherent oscillations and uncovered distinct timescales governing the system's behavior. This work not only enhances our understanding of non-equilibrium dynamics in crystals but also paves the way for designing advanced multi-frequency photonic devices, offering new opportunities for solid-state emulations and technological innovations.