37 research outputs found
A generalized phase space approach for solving quantum spin dynamics
Numerical techniques to efficiently model out-of-equilibrium dynamics in
interacting quantum many-body systems are key for advancing our capability to
harness and understand complex quantum matter. Here we propose a new numerical
approach which we refer to as GDTWA. It is based on a discrete semi-classical
phase-space sampling and allows to investigate quantum dynamics in lattice spin
systems with arbitrary . We show that the GDTWA can accurately
simulate dynamics of large ensembles in arbitrary dimensions. We apply it for
spin-models with dipolar long-range interactions, a scenario arising in
recent experiments with magnetic atoms. We show that the method can capture
beyond mean-field effects, not only at short times, but it also correctly
reproduces long time quantum-thermalization dynamics. We benchmark the method
with exact diagonalization in small systems, with perturbation theory for short
times, and with analytical predictions made for closed system which feature
quantum-thermalization at long times. By computing the Renyi entropy, currently
an experimentally accessible quantifier of entanglement, we reveal that large
systems can feature larger entanglement than corresponding systems.
Our analyses demonstrate that the GDTWA can be a powerful tool for modeling
complex spin dynamics in regimes where other state-of-the art numerical methods
fail
Many-body cavity quantum electrodynamics with driven inhomogeneous emitters
Quantum emitters coupled to optical resonators are quintessential systems for
exploring fundamental phenomena in cavity quantum electrodynamics (cQED) and
are commonly used in quantum devices acting as qubits, memories and
transducers. Many previous experimental cQED studies have focused on regimes in
which a small number of identical emitters interact with a weak external drive,
such that the system can be described with simple, effective models. However,
the dynamics of a disordered, many-body quantum system subject to a strong
drive have not been fully explored, despite its importance and potential in
quantum applications. Here we study how a large, inhomogeneously broadened
ensemble of solid-state emitters coupled with high cooperativity to a
nanophotonic resonator behaves under strong excitation. We discover a sharp,
collectively induced transparency (CIT) in the cavity reflection spectrum,
resulting from quantum interference and collective response induced by the
interplay between driven inhomogeneous emitters and cavity photons.
Furthermore, coherent excitation within the CIT window leads to highly
nonlinear optical emission, spanning from fast superradiance to slow
subradiance. These phenomena in the many-body cQED regime enable new mechanisms
for achieving slow light and frequency referencing, pave a way towards
solid-state superradiant lasers and inform the development of ensemble-based
quantum interconnects.Comment: ML and RF contributed equally to this wor
Shattered Time: Can a Dissipative Time Crystal Survive Many-Body Correlations?
We investigate the emergence of a time crystal in a driven-dissipative
many-body spin array. In this system the interplay between incoherent spin
pumping and collective emission stabilizes a synchronized non-equilibrium
steady state which in the thermodynamic limit features a self-generated
time-periodic pattern imposed by collective elastic interactions. In contrast
to prior realizations where the time symmetry is already broken by an external
drive, here it is only spontaneously broken by the elastic exchange
interactions and manifest in the two-time correlation spectrum. Employing a
combination of exact numerical calculations and a second-order cumulant
expansion, we investigate the impact of many-body correlations on the time
crystal formation and establish a connection between the regime where it is
stable and a slow growth rate of the mutual information, signalling that the
time crystal studied here is an emergent semi-classical out-of-equilibrium
state of matter. We also confirm the rigidity of the time crystal to
single-particle dephasing. Finally, we discuss an experimental implementation
using long-lived dipoles in an optical cavity.Comment: v1: Initial commit; v2: Added references, fixed a couple typos, and
made some small, stylistic changes; v3: Update to reflect publication.
Includes additional references and some minor addition
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Many-Body Physics in Long-Range Interacting Quantum Systems
Ultracold atomic and molecular systems provide a useful platform for understanding quantum many-body physics. Recent progresses in AMO experiments enable access to systems exhibiting long-range interactions, opening a window for exploring the interplay between long-range interactions and dissipation. In this thesis, I develop theoretical approaches to study non-equilibrium dynamics in systems where such interplay is crucial.
I first focus on a system of KRb molecules, where dipolar interactions and fast chemical reactions coexist. Using a classical kinetic theory and Monte Carlo methods, I study the evaporative cooling in a quasi-two-dimensional trap, and develop a protocol to reach quantum degeneracy. I also study the case where molecules are loaded into an optical lattice, and show that the strong dissipation induces a quantum Zeno effect, which suppresses the molecule loss. The analysis requires including multiple bands to explain recent experimental measurements, and can be used to determine the molecular filling fraction.
I also investigate a system of radiating atoms, which experience long-range elastic and dissipative interactions. I explore the collective behavior of atoms and the role of atomic motion. The model is validated by comparison with a recent light scattering experiment using Sr atoms. I also show that incoherently pumped dipoles can undergo a dynamical phase transition to synchronization, and study its signature in the quantum regime
Role of estrogen in the regulation of central and peripheral energy homeostasis: from a menopausal perspective
Estrogen plays a prominent role in regulating and coordinating energy homeostasis throughout the growth, development, reproduction, and aging of women. Estrogen receptors (ERs) are widely expressed in the brain and nearly all tissues of the body. Within the brain, central estrogen via ER regulates appetite and energy expenditure and maintains cell glucose metabolism, including glucose transport, aerobic glycolysis, and mitochondrial function. In the whole body, estrogen has shown beneficial effects on weight control, fat distribution, glucose and insulin resistance, and adipokine secretion. As demonstrated by multiple in vitro and in vivo studies, menopause-related decline of circulating estrogen may induce the disturbance of metabolic signals and a significant decrease in bioenergetics, which could trigger an increased incidence of late-onset Alzheimer’s disease, type 2 diabetes mellitus, hypertension, and cardiovascular diseases in postmenopausal women. In this article, we have systematically reviewed the role of estrogen and ERs in body composition and lipid/glucose profile variation occurring with menopause, which may provide a better insight into the efficacy of hormone therapy in maintaining energy metabolic homeostasis and hold a clue for development of novel therapeutic approaches for target tissue diseases