Spring 2022

Abstract: In general, quantum states are very sensitive to coupling to the environment. In many cases this interaction leads to a loss of coherence and a transformation of the quantum mechanical system to classical behavior. However, quantum states can also be stabilized if the environment and the coupling to it are appropriately engineered. This is the basic idea of the research results that I will present in this talk.

Abstract: Emergent two-dimensional (2D) atomic crystals [1,2] hold great promise for efficient control of magnetism, fundamentally owing to the 2D nature. However, thus far, there have been only proof-of-concept reports on electrical and optical control of 2D magnetism, and there appear to be some fundamental obstacles for the efficient control. In this talk, I will analyze the challenges and present our recent theoretical and experimental progress on efficient electrical and optical control of 2D magnetism [3-5].

Abstract: Strong exciton-photon interaction results in the formation of half-light half-matter quasiparticles called exciton-polaritons (EPs) that take on the properties of both its constituents. In this talk, I will first introduce polariton formation in 2D semiconductors  [1] followed by a discussion of Rydberg excitons [2] and dipolar excitons  [3] to realize highly nonlinear interactions to achieve polariton blockade.

Abstract: Neutron interferometry is practiced with de Broglie wavelengths of 0.1 nanometer over path lengths of 0.1 meter, typically in Mach-Zehnder configurations familiar to practitioners of atom and optical interferometry.

Abstract: The bright emission observed in cesium lead halide perovskite nanocrystals (NCs) has recently been explained in terms of a bright exciton ground state, a claim that would make these materials the first known examples in which the exciton ground state is not an optically forbidden dark exciton.

Abstract: I will describe the theory of generalized hydrodynamics (GHD), which allows the dynamics of nearly integrable many-body quantum systems to be accurately modeled. GHD has two assumptions: the continuum approximation and local equilibration to the Generalized Gibbs ensemble (GGE). We use bundles of 1D Bose gases to test GHD and show that the theory works remarkably well for quite a long time after even very large trap quenches and even for as few as 10 atoms per 1D gas. We have also performed wavefunction quenches.

Abstract:Quantum computers have finally reached a level of complexity where real-time quantum error correction is possible. Current systems have shown an advantage using encoded qubits for some experiments, but no experiment has shown a decisive victory of encoded qubits over physical qubits. I will review the current state-of-the-art and then provide some lessons learned from adapting fault-tolerant quantum circuits to ion trap hardware.

Abstract: Quantum spin liquids are remarkable phases of matter in which quantum entanglement is, in a precise sense, truly long-ranged.  I will describe realization of quantum spin liquid correlations in recent experiments on pumped Rydberg atoms trapped in arrays of optical tweezers.  I will also describe how recent theories of quantum spin liquids in metallic states provide a description of photoemission observations in the mysterious “pseudogap” state of the cuprate high temperature superconductors.

Abstract: Materials are often used to manipulate and control photons.  Metamaterials -- judiciously engineered material structures -- have enabled scientists and engineers to construct platforms with unconventional material parameters, providing exciting opportunities for optical and microwave devices and components.

Abstract: We add non-linear and state-dependent terms to quantum field theory. We show that the resulting low-energy theory, non-linear quantum mechanics, is causal, preserves probability and permits a consistent description of the process of measurement. We explore the consequences of such terms and show that non-linear quantum effects can be observed in macroscopic systems even in the presence of de-coherence. We find that current experimental bounds on these non-linearities are weak and propose several experimental methods to significantly probe these effects.