Probing Novel Out-of-Equilibrium Quantum Dynamics in Homogeneous Atomic Quantum Gases

Purdue University, West Lafayette IN

Investigators

Abstract

Dynamical systems with intrinsic instability can amplify small initial perturbations to produce fascinating features we experience daily, from cloud and pattern formation in weather and geography, freak waves in oceanography, to structure formation in the universe. Such dynamics in quantum many-body systems present interesting but challenging problems because of the need to consider quantum correlations between the constituent particles. An instability could amplify initial quantum fluctuations, noise that exists even without external or thermal perturbations, into an observable pattern that could show distinct behaviors compared with those found in classical systems. Understanding quantum instability dynamics could lead to a better understanding of microscopic to mesoscopic quantum phenomena and new applications such as quantum-enhanced amplifiers and sensors. In this project, the research team will use ultracold atomic gases to form a uniform superfluid and study its out-of-equilibrium behavior and instability-induced quantum dynamics. The first project goal aims at exploring the dynamics of ultracold atoms brought to an attractive interaction so that the system becomes unstable against density perturbations. The team will study how these perturbations evolve due to a pattern forming instability and detect quantum correlations within the system. In the second project goal, the team will implement a new scheme to make a superfluid flow faster than the speed of sound and study the instability of the supersonic flow. The aim is to examine how energy flow is dissipated in the system, which may find connections with important topics in condensed matter and plasma physics, and astronomy. This project will provide training for multiple PhD students and undergraduate research assistants, preparing them for future physics careers. The project will also support the PI’s continuing participation in outreach activities at Purdue University, including an instrumentation development program with the active involvement of service-learning undergraduate students and local high school students. The PI and the team will use ultracold cesium atoms trapped in an optical box to study novel nonequilibrium physics and instability-induced quantum dynamics. Ultracold atoms present an ideal testbed for studying out-of-equilibrium quantum dynamics because of the well-developed control toolbox for accessing instability physics with precise timing and for probing them with many details. The tools include precision tuning of atomic interactions through a Feshbach resonance and arbitrary potential-shaping that could induce dynamics with high spatiotemporal resolution. High-resolution in-situ imaging, time-of-flight measurements, and interferometry will provide complementary information on the density distribution, momentum state population, and long-range phase coherence. The project goals include probing quantum many-body dynamics in an attractive Bose gas and supersonic turbulence in a superfluid. The first goal aims at studying the dynamics of quantum many-body breathers, distinct from mean-field breathers, exploring a novel quantum phase transition in a one-dimensional Bose gas that occurs even at zero temperature, and detecting the non-local correlations and quantum entanglement in a novel state of a Bose condensate following an interaction quench. The second goal aims at using engineered dissipation to induce supersonic flows in a superfluid and to observe the instability of the flow. This technique allows the study of supersonic turbulence in a compressible, zero-viscosity quantum fluid. The engineered supersonic flow also promises a new way of generating sonic black holes. Success in this project could lead to a better understanding of instabilities and entanglement generation in quantum many-body systems, quantum thermalization problems, dynamical quantum phase transitions, and quantum turbulence in supersonic flows. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.