Periodic Reporting for period 1 - Q-FLIGHTS (Quantum Fluids-of-Light Turbulence in Semiconductor microcavities)
Reporting period: 2023-07-01 to 2025-06-30
The Q-FLIGHTS project explored a special kind of quantum fluid made of light, called an exciton-polariton fluid, which forms in semiconductor microcavities under laser excitation. These fluids exhibit remarkable properties like superfluidity and the formation of quantized vortices, similar to those observed in liquid helium or ultracold atomic gases.
Unlike traditional fluids, polariton fluids are driven by lasers and constantly dissipate energy, making them fundamentally out of equilibrium. This opens the door to observing unique physical phenomena, including quantum turbulence, a highly complex state where many vortices form, move, and interact in unpredictable ways.
The main objective of Q-FLIGHTS was to study how turbulence emerges in such fluids, and how it differs from classical turbulence (like air or water flow). To achieve this, the project developed a novel experimental platform capable of capturing “snapshots” of these light fluids in real time, with high spatial and temporal resolution. Alongside this, the project established theoretical models to describe the conditions under which the fluid behaves regularly, forms solitons, becomes turbulent, or regains coherence as a superfluid.
Q-FLIGHTS aimed to:
-Reveal the statistical nature of vortex nucleation in 2D polariton fluids.
-Develop ultrafast detection methods based on nonlinear optics.
-Simulate and classify the various dynamical regimes of these fluids.
Unlike traditional fluids, polariton fluids are driven by lasers and constantly dissipate energy, making them fundamentally out of equilibrium. This opens the door to observing unique physical phenomena, including quantum turbulence, a highly complex state where many vortices form, move, and interact in unpredictable ways.
The main objective of Q-FLIGHTS was to study how turbulence emerges in such fluids, and how it differs from classical turbulence (like air or water flow). To achieve this, the project developed a novel experimental platform capable of capturing “snapshots” of these light fluids in real time, with high spatial and temporal resolution. Alongside this, the project established theoretical models to describe the conditions under which the fluid behaves regularly, forms solitons, becomes turbulent, or regains coherence as a superfluid.
Q-FLIGHTS aimed to:
-Reveal the statistical nature of vortex nucleation in 2D polariton fluids.
-Develop ultrafast detection methods based on nonlinear optics.
-Simulate and classify the various dynamical regimes of these fluids.
During the fellowship, the Q-FLIGHTS project combined advanced optical experiments and theoretical modeling to investigate quantum turbulence in two-dimensional polariton fluids. The work progressed along two complementary lines:
1. Experimental progress
The project developed and demonstrated a novel detection technique based on ultrafast nonlinear optics (Difference Frequency Generation) capable of capturing single-shot, two-dimensional images of photon statistics with picosecond resolution. This technique allows for visualization of light fluid dynamics, including vortex configurations. A key achievement was the experimental demonstration and theoretical validation of the method’s ability to preserve and resolve bidimensional photon statistics, a crucial step for probing turbulent dynamics in quantum fluids.
Importantly, during the project we identified that the measured photon statistics were strongly influenced by the temporal mode structure of the nonlinear amplifier. This effect limited the detection fidelity in certain cases. Through a detailed theoretical analysis, we developed a strategy to circumvent this limitation by projecting the signal onto a well-defined temporal mode basis. This approach significantly improved the accuracy and robustness of the measurements, making the detection platform suitable for high-fidelity, real-time statistical analysis of quantum fluids.
2. Theoretical and numerical modeling
In parallel, the project established a robust model of polariton fluid dynamics under counterpropagating laser pumping. Using advanced numerical simulations, four distinct dynamical regimes were identified: linear, solitonic, turbulent, and superfluid. Each regime was characterized by its density patterns, phase structure, and temporal coherence. The turbulent regime, in particular, was shown to emerge spontaneously under specific pumping conditions and was mapped in detailed phase diagrams as a function of key system parameters
The combination of experimental innovation and theoretical insight opens new perspectives for studying out-of-equilibrium quantum systems. The project’s results are compatible with current semiconductor platforms and provide a roadmap for future studies of vortex statistics, energy cascades, and dynamical instabilities in quantum fluids of light.
1. Experimental progress
The project developed and demonstrated a novel detection technique based on ultrafast nonlinear optics (Difference Frequency Generation) capable of capturing single-shot, two-dimensional images of photon statistics with picosecond resolution. This technique allows for visualization of light fluid dynamics, including vortex configurations. A key achievement was the experimental demonstration and theoretical validation of the method’s ability to preserve and resolve bidimensional photon statistics, a crucial step for probing turbulent dynamics in quantum fluids.
Importantly, during the project we identified that the measured photon statistics were strongly influenced by the temporal mode structure of the nonlinear amplifier. This effect limited the detection fidelity in certain cases. Through a detailed theoretical analysis, we developed a strategy to circumvent this limitation by projecting the signal onto a well-defined temporal mode basis. This approach significantly improved the accuracy and robustness of the measurements, making the detection platform suitable for high-fidelity, real-time statistical analysis of quantum fluids.
2. Theoretical and numerical modeling
In parallel, the project established a robust model of polariton fluid dynamics under counterpropagating laser pumping. Using advanced numerical simulations, four distinct dynamical regimes were identified: linear, solitonic, turbulent, and superfluid. Each regime was characterized by its density patterns, phase structure, and temporal coherence. The turbulent regime, in particular, was shown to emerge spontaneously under specific pumping conditions and was mapped in detailed phase diagrams as a function of key system parameters
The combination of experimental innovation and theoretical insight opens new perspectives for studying out-of-equilibrium quantum systems. The project’s results are compatible with current semiconductor platforms and provide a roadmap for future studies of vortex statistics, energy cascades, and dynamical instabilities in quantum fluids of light.
Q-FLIGHTS advanced the state of the art in both experimental and theoretical sides by developing and validating an ultrafast imaging technique capable of accessing two-dimensional photon statistics with single-shot acquisition. Before this project, such measurements were either spatially integrated or limited to averaged multi-shot data, preventing the analysis of spontaneous vortex nucleation and fast turbulent fluctuations. The ability to record individual realizations of the photon field opens new experimental avenues for studying stochastic processes and topological defects in quantum fluids.
On the theoretical side, the project introduced a counterflow geometry, based on two coherent, counterpropagating laser pumps, that enables precise control over momentum injection and energy distribution in the fluid. Using realistic driven-dissipative Gross-Pitaevskii simulations, four distinct dynamical regimes were mapped and characterized through coherence and spectral observables. The identification of turbulence via measurable coherence drop and spectral broadening provides a concrete, experimentally accessible signature for future studies.
These results are expected to impact the field of quantum fluid dynamics by providing both the tools and models necessary for exploring deep quantum turbulence, vortex clustering, and superfluid-to-turbulent transitions. More broadly, the detection scheme and modeling framework may benefit researchers in quantum optics, nonlinear photonics, and statistical physics.
On the theoretical side, the project introduced a counterflow geometry, based on two coherent, counterpropagating laser pumps, that enables precise control over momentum injection and energy distribution in the fluid. Using realistic driven-dissipative Gross-Pitaevskii simulations, four distinct dynamical regimes were mapped and characterized through coherence and spectral observables. The identification of turbulence via measurable coherence drop and spectral broadening provides a concrete, experimentally accessible signature for future studies.
These results are expected to impact the field of quantum fluid dynamics by providing both the tools and models necessary for exploring deep quantum turbulence, vortex clustering, and superfluid-to-turbulent transitions. More broadly, the detection scheme and modeling framework may benefit researchers in quantum optics, nonlinear photonics, and statistical physics.