Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userNegative differential conductivity and quantum statistical effects in a three-site Bose-Hubbard model
53
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The use of an electron beam to remove ultracold atoms from selected sites in an optical lattice has opened up new opportunities to study transport in quantum systems [R. Labouvie {it et al. }, Phys. Rev. Lett. {bf 115}, 050601 (2015)]. Inspired by this experimental result, we examine the effects of number difference, dephasing, and initial quantum statistics on the filling of an initially depleted middle well in the three-well inline Bose-Hubbard model. We find that the well-known phenomenon of macroscopic self-trapping is the main contributor to oscillatory negative differential conductivity in our model, with phase diffusion being a secondary effect. However, we find that phase diffusion is required for the production of direct atomic current, with the coherent process showing damped oscillatory currents. We also find that our results are highly dependent on the initial quantum states of the atoms in the system.
rate research
Read More
Ultracold atoms in optical lattices provide a unique opportunity to study Bose- Hubbard physics. In this work we show that by considering a spatially varying onsite interaction it is possible to manipulate the motion of excitations above the Mott phase in a Bose-Hubbard system. Specifically, we show that it is possible to engineer regimes where excitations will negatively refract, facilitating the construction of a flat lens.
The modern description of elementary particles, as formulated in the Standard Model of particle physics, is built on gauge theories. Gauge theories implement fundamental laws of physics by local symmetry constraints. For example, in quantum electrodynamics, Gausss law introduces an intrinsic local relation between charged matter and electromagnetic fields, which protects many salient physical properties including massless photons and a long-ranged Coulomb law. Solving gauge theories by classical computers is an extremely arduous task, which has stimulated a vigorous effort to simulate gauge-theory dynamics in microscopically engineered quantum devices. Previous achievements implemented density-dependent Peierls phases without defining a local symmetry, realized mappings onto effective models to integrate out either matter or electric fields, or were limited to very small systems. The essential gauge symmetry has not been observed experimentally. Here, we report the quantum simulation of an extended U(1) lattice gauge theory, and experimentally quantify the gauge invariance in a many-body system comprising matter and gauge fields. These are realized in defect-free arrays of bosonic atoms in an optical superlattice of 71 sites. We demonstrate full tunability of the model parameters and benchmark the matter--gauge interactions by sweeping across a quantum phase transition. Enabled by high-fidelity manipulation techniques, we measure the degree to which Gausss law is violated by extracting probabilities of locally gauge-invariant states from correlated atom occupations. Our work provides a way to explore gauge symmetry in the interplay of fundamental particles using controllable large-scale quantum simulators.
The manipulation of many-body systems often involves time-dependent forces that cause unwanted heating. One strategy to suppress heating is to use time-periodic (Floquet) forces at large driving frequencies. For quantum spin systems with bounded spectra, it was shown rigorously that the heating rate is exponentially small in the driving frequency. Recently, the exponential suppression of heating has also been observed in an experiment with ultracold atoms, realizing a periodically driven Bose-Hubbard model. This model has an unbounded spectrum and, hence, is beyond the reach of previous theoretical approaches. Here, we study this model with two semiclassical approaches valid, respectively, at large and weak interaction strengths. In both limits, we compute the heating rates by studying the statistical probability to encounter a many-body resonance, and obtain a quantitative agreement with the exact diagonalization of the quantum model. Our approach demonstrates the relevance of statistical arguments to Floquet perthermalization of interacting many-body quantum systems.
We address the effects of quenched disorder averaging in the time-evolution of systems of ultracold atoms in optical lattices in the presence of noise, imposed by of an environment. For bosonic systems governed by the Bose-Hubbard Hamiltonian, we quantify the response of disorder in Hamiltonian parameters in terms of physical observables, including bipartite entanglement in the ground state and report the existence of disorder-induced enhancement in weakly interacting cases. For systems of two-species fermions described by the Fermi-Hubbard Hamiltonian, we find similar results. In both cases, our dynamical calculations show no appreciable change in the effects of disorder from that of the initial state of the evolution. We explain our findings in terms the statistics of the disorder in the parameters and the behaviour of the observables with the parameters.
We investigate the quantum measurement noise effects on the dynamics of an atomic Bose lattice gas inside an optical resonator. We describe the dynamics by means of a hybrid model consisting of a Bose--Hubbard Hamiltonian for the atoms and a Heisenberg--Langevin equation for the lossy cavity field mode. We assume that the atoms are prepared initially in the ground state of the lattice Hamiltonian and then start to interact with the cavity mode. We show that the cavity field fluctuations originating from the dissipative outcoupling of photons from the resonator lead to vastly different effects in the different possible ground state phases, i.e., the superfluid, the supersolid, the Mott- and the charge-density-wave phases. In the former two phases with the presence of a superfluid wavefunction, the quantum measurement noise appears as a driving term leading to excess noise depletion of the ground state. The time scale for the system to leave the ground scale is determined analytically. For the latter two incompressible phases, the quantum noise results in the fluctuation of the chemical potential. We derive an analytical expression for the corresponding broadening of the quasiparticle resonances.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
