The Macroscopic Description of Chaotic Quantum Systems

The study conducted by Professor Monika Aidelsburger and Professor Immanuel Bloch from the LMU Faculty of Physics raises an interesting question about whether chaotic quantum systems can be described using simple diffusion equations with random noise. This approach, known as hydrodynamics, simplifies the macroscopic description of systems by focusing on the overall behavior rather than the microscopic interactions of particles.

One of the key findings of the research team led by Professor Aidelsburger and Professor Bloch is the concept of white noise in chaotic quantum systems. This white noise, resulting from random collisions of particles with individual molecules, can be described as fluctuations in the system. These fluctuations, when analyzed using fluctuating hydrodynamics (FHD), show that under certain circumstances, the behavior of a system can be determined by a single quantity – the diffusion constant.

Quantum systems pose unique challenges when it comes to describing their behavior. The laws of physics governing quantum particles are fundamentally different from those governing classical particles, leading to phenomena like uncertainty and entanglement. These characteristics make quantum systems even more complex to calculate, making an FHD description particularly beneficial.

The research team conducted experiments to study the behavior of chaotic many-body quantum systems at a microscopic level. By preparing a quantum system of ultracold cesium atoms in optical lattices in a non-equilibrium state and allowing it to evolve freely, the team was able to observe how fluctuations and density correlations grew over time. The results indicated that FHD could describe the system both qualitatively and quantitatively.

The findings of this study provide valuable insights into the macroscopic description of chaotic quantum systems. Despite the inherent complexity of quantum interactions, the research team’s results suggest that these systems can be simplified as a macroscopic diffusion process similar to Brownian motion. This has significant implications for understanding and predicting the behavior of chaotic quantum systems in various contexts.

The research conducted by Professor Aidelsburger, Professor Bloch, and their team sheds light on the potential for describing chaotic quantum systems using simple diffusion equations with random noise. By applying the principles of fluctuating hydrodynamics to quantum systems, the researchers have demonstrated that despite their microscopic complexity, these systems can be understood at a macroscopic level. This opens up new possibilities for studying and analyzing chaotic quantum systems in the future.