In the world of physics, systems that consist of many interacting small particles can often be incredibly complex and chaotic. It may seem daunting to try and understand and describe these systems, but there are cases where simple theories can be applied to make sense of the chaos. But can this simplicity also be extended to the realm of quantum physics?
A recent study conducted by a research team led by Professor Monika Aidelsburger and Professor Immanuel Bloch from the LMU Faculty of Physics delves into this question. The team discovered intriguing indications that quantum many-body systems could potentially be described using macroscopic diffusion equations with random noise, offering a simpler explanation for their behavior.
The concept of hydrodynamics, which allows for the macroscopic description of the behavior of fluids without delving into the specifics of individual molecules, serves as a foundation for this new approach. Julian Wienand, a doctoral candidate in Immanuel Bloch’s research team and the lead author of the study, explains that the erratic movements of small particles within a fluid, known as Brownian motion, can be understood as fluctuations caused by random collisions, akin to white noise.
Wienand elaborates on the theory of fluctuating hydrodynamics (FHD), which suggests that the entire behavior of a system can be simplified and determined by a single quantity, the diffusion constant. This remarkable insight streamlines the macroscopic description of complex systems, eliminating the need to delve into the microscopic interactions of individual particles.
Despite the promising developments in the field of FHD for classical systems, the applicability of this approach to chaotic quantum systems remains a significant challenge. Quantum particles operate under fundamentally different laws of physics, characterized by concepts such as uncertainty and entanglement, which defy conventional intuition.
To address this challenge, the research team conducted experiments to observe the behavior of chaotic many-body quantum systems on 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 measure fluctuations and density correlations over time.
The results of the study indicated that the chaotic quantum system under examination exhibited characteristics that could be effectively described by fluctuating hydrodynamics (FHD). Despite the intricate microscopic complexity of quantum systems, the findings suggest the potential for simplifying their description as a macroscopic diffusion process, akin to the behavior of Brownian motion.
The research conducted by Professor Monika Aidelsburger, Professor Immanuel Bloch, and their team sheds light on the fascinating possibilities of applying simple diffusion equations and fluctuating hydrodynamics to describe the behavior of chaotic quantum systems. While challenges remain in fully understanding the intricacies of quantum interactions, these findings open up new avenues for simplifying the complexity of quantum physics.
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