RUI: Quantum Sensing and Simulation with Ultracold Atoms in Ring Lattices

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Quantum technologies will play a central role in shaping human and societal progress in this century, as devices and applications reach limits set by classical physics, and are inevitably impelled into the realms of quantum mechanics to sustain continued advancement. Owing to fundamentally different principles and constraints involved, such migration will be selective rather than comprehensive, and the arenas of sensing, simulation and computation are the most promising. This project focuses on the first two aspects as they can already deliver considerable benefits even in the near term. Quantum effects have been demonstrated to offer substantial enhancement of sensitivity to accelerations, while due to the enormous dimensions of relevant Hilbert spaces, quantum systems are the best simulators of quantum physics with a designer system serving to mimic hard-to-access scenarios of interest. Underlying all such goals, however, the defining challenge continues to be the fragility of quantum states and effects as they interface with the classical world. Therefore, broad success hinges on finding the right platform. This project aims to study and develop a novel alternate platform comprised of ultracold atoms confined to a ring-shaped periodic lattice, a system that is robust, yet encompasses all quantum-mechanical features relevant for applications. The closed loop structure makes for a compact unit that mitigates boundary effects, favors sustained flow, allows easy scaling of size and multiplicity, and directly manifests the quintessential quantum feature of non-locality. The variable lattice structure provides a versatile way to manipulate the system while providing a precise scale for relevant observables. Training of numerous undergraduate students in physics research will be a priority, building on success under prior grants to leverage the experience to channel students into STEM career paths, including many from under-represented demographics. The goals for sensor development comprise two primary directions. One is based on a new principle that utilizes a localization transition that occurs in ring-shaped lattices. In the context of neutral atoms, the principle can be adapted for rotation detection and measurement. Alternately, with a charged medium, it can be similarly adapted for sensing magnetic fields. The second line of research will seek to generate squeezed states of circulating modes in ring lattices to realize implementations of interferometers that use quantum correlated states to improve sensitivity, as exemplified by SU(1,1) interferometers. As a quantum simulator, the system will be utilized to explore the physics of superfluidity and associated transitions to insulator states, as well as the impact of topology on quantum states, such as defined by the quantum Hall effect. With the lattice coupling the circulating modes in a ring much like a laser field couples electronic states in an atom, the system will also be developed as a quantum-optics simulator. With natural periodic boundaries mitigating some finite size effects, cold atoms in ring lattices can be a new platform for studying non-equilibrium physics, including questions of thermalization and relaxation of many-body quantum systems. Interplay of inter-atomic interactions and of the lattice structure in a ring configuration will allow simulation of various nonlinear dynamical effects.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.