CAREER: Floquet Route to Non-Equilibrium Phases of Matter in Cavity QED

点击翻译按钮获取中文摘要

NONTECHNICAL SUMMARYThis CAREER award supports theoretical research and education into states of interacting light and matter that are not in usual steady states of equilibrium. The world around us is described by quantum mechanics, yet quantum mechanical phenomena are absent from our day-to-day life. This anomaly comes from the enormous complexity of the many interacting atoms that make up everyday objects, which wash out quantum effects to give the classical world. By isolating electrons and atoms from this complex environment, experimentalists have made enormous strides towards realizing quantum effects in increasing large and practical devices, which has become known as the second quantum revolution. This revolution will further the need for understanding quantum physics at its most fundamental level, which is the overarching goal of this CAREER award. The research will focus on a class of systems known as many-body cavity quantum electrodynamics (QED), which gives access to quantum properties of light and insight into the interaction between light and matter. Quantum mechanics tells us that light comes in individual units called photons, but conventional lasers contain so many photons that seeing quantum effects from each one is impossible. Cavity QED works by confining the light between two nearly perfect mirrors. One then prepares states where there are not millions or billions of photons in the cavity, but rather one or two. When the photon number is so low that individual photons can be seen, the photons behave quantum mechanically. Many-body cavity QED consists of these photons interacting with atoms that behave quantum mechanically as well. This project will study how these systems respond when they are kicked out of equilibrium, which is anticipated to give qualitatively new features due to the quantum mechanical push and pull between the light and the matter. These interactions should further provide applications down the road in a variety of quantum technologies, such as next-generation lasers and high-precision sensors.The research will be complemented by an educational program built around designing a virtual reality (VR) module allowing users to interact with simple quantum mechanical systems such as the hydrogen atom. By virtually shrinking the user to the size of the hydrogen atom, the VR module will enable them to interact with the quantum mechanical world directly. From an educational standpoint, the quantum VR module will provide a new route to learn about the fundamental rules of quantum mechanics without the mathematical overhead. This will create understanding and excitement which is relevant to training next-generation scientists and engineers, as quantum mechanics becomes an increasingly indispensable part of science and technology.TECHNICAL SUMMARYThis CAREER award supports theoretical research and education into nonequilibrium states of interacting light and matter. Time-periodic, or Floquet, driving is one of the most powerful tools for engineering quantum systems. Traditionally, a strong high frequency drive is used to modify the effective Hamiltonian, enabling the realization of artificial structures such as strong effective magnetic fields in neutral atoms. Recently, new phases of matter have been discovered that exploit the fundamentally nonequilibrium nature of the Floquet drive. Examples such as the Floquet time crystal were quickly realized after their theoretical discovery, opening the door for novel nonequilibrium routes to symmetry breaking.In practice, the Floquet drive is often done by microwave or optical photons. Confining these photons to a cavity, they may also be treated as quantum degrees of freedom, a paradigm known as many-body cavity quantum electrodynamics (QED). The semiclassical Floquet limit is obtained when the cavity photon occupation is large, but cavities afford the intriguing possibility of going to quantum limit by decreasing the photon number, thus accessing a different regime of strongly coupled quantum light and matter.This research will study the many-body cavity QED limit of nonequilibrium Floquet phases of matter. Doing so naturally leads to new nonequilibrium states of matter with anomalous behavior, which may be thought of as arising from competition between native local interactions and global interactions mediated by the cavity. The research will involve three broad directions: (1) understanding the competition between thermalization and many-body localization in a cavity, (2) demonstrating symmetry breaking states such as time crystals in the presence of the cavity, and (3) classifying topological states of matter coupled to one or more cavities, including quantized photon pumps.This work will bridge the active but mostly independent fields of many-body cavity QED and Floquet physics, providing a pathway to new phases of matter that lie between the limits that are often considered. The research team will extend the classification of nonequilibrium phases of matter, where anomalous states induced by the interplay of short- and long-range interactions remain particularly challenging. Experimental realizations will be explored in nitrogen vacancy centers, superconducting circuits, ultracold atoms, and trapped ions. The resulting entangled states of strongly coupled light and matter will have relevance to the fundamental science of quantum information and applications in quantum metrology.This research will be complemented by designing a virtual reality (VR) module allowing users to interact with simple quantum mechanical systems. The quantum VR will illustrate some key aspects of quantum mechanics, such as the wave nature of electrons, quantum measurements, and radiative decay, which have proved elusive to many learners. This is vital for both public science and technological applications as quantum technologies become increasingly relevant, lowering the barrier to entry for scientists, engineers, and members of the public. Feedback from users will serve as a seed for future development of visualization methods in a broader range of quantum systems.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.