Atomic multipole relaxation rates near surfaces

Hysteresis of noninteracting and spin-orbit coupled atomic Fermi gases with relaxation

Hysteresis can be found in driven many-body systems such as magnets and superfluids. Rate-dependent hysteresis arises when a system is driven periodically while relaxing towards equilibrium. A two-state paramagnet driven by an oscillating magnetic field in the relaxation approximation clearly demonstrates rate-dependent hysteresis. A noninteracting atomic Fermi gas in an optical ring potential, when driven by a periodic artificial gauge field and subjected to dissipation, is shown to exhibit hysteresis loops of atomic current due to a competition of the driving time and the relaxation time. Th…

Relaxation time for monitoring the quantumness of an intense cavity field

Recently it was shown that the quantum behavior of an intense cavity field can be revealed by measuring the steady atomic correlations between two ideal atoms, which interact with the same leaking cavity mode. Considering a weak atom-field coupling regime and large average number of photons in the cavity mode ($\bar{n}$), one expects that a semiclassical theory could explain the whole dynamics of the system. However, this system presents the generation of correlations between the atoms, which is a signature of the quantumness of the cavity field even in the limit of $\bar{n} \gg 1$ [Phys. Rev.…

Quantum Zeno effect in atomic spin-exchange collisions

The suppression of spin-exchange relaxation in dense alkali-metal vapors discovered in 1973 and governing modern atomic magnetometers is here reformulated in terms of quantum measurement theory and the quantum Zeno effect. This provides a new perspective of understanding decoherence in spin-polarized atomic vapors.

Blackbody radiation shift, multipole polarizabilities, oscillator strengths, lifetimes, hyperfine constants, and excitation energies in Ca+

A systematic study of Ca+ atomic properties is carried out using high-precision relativistic all-order method where all single, double, and partial triple excitations of the Dirac-Fock wave functions are included to all orders of perturbation theory. Reduced matrix elements, oscillator strengths, transition rates, and lifetimes are determined for the levels up to n = 7. Recommended values and estimates of their uncertainties are provided for a large number of electric-dipole transitions. Electric-dipole scalar polarizabilities for the 5s, 6s, 7s, 8s, 4p, 5p, 3d, and 4d states and tensor polari…

High-Multipole Excitations of Hydrogen-Like Atoms by Twisted Photons near Phase Singularity

We calculate transition amplitudes and cross sections for excitation of hydrogen-like atoms by the twisted photon states, or photon states with angular momentum projection on the direction of propagation exceeding $\hbar$. If the target atom is located at distances of the order of atomic size near the phase singularity in the vortex center, the transitions rates into the states with orbital angular momentum $l_f>1$ become comparable with the rates for electric dipole transitions. It is shown that when the transition rates are normalized to the local photon flux, the resulting cross sections fo…

Photonic Chern insulators from two-dimensional atomic lattices interacting with a single surface plasmon polariton

We study the polaritonic bandstructure of two-dimensional atomic lattices coupled to a single excitation of a surface plasmon polariton mode. We show the possibility of realizing topological gaps with different Chern numbers by having resonant atomic transitions to excited states with different angular momentum. We employ a computational method based on the recently proposed Dirichlet-to-Neumann (DtN) map technique which accurately models non-Markovian dynamics as well as interactions involving higher-order electric and magnetic multipole transitions. We design topologically robust edge states…

高斯噪声存在下原子-分子玻色凝聚体中的弛豫动力学

Relaxation Dynamics in Atomic-Molecular Bose Condensates in the Presence of Gaussian Noise

本文用 Bloch 球模型研究高斯白噪声下经 Feshbach 失谐弱耦合的原子-分子玻色凝聚体，比较 BBGKY 级列与平均场近似的弛豫率，并揭示关联、涨落及结构化噪声对相干性和时间平均量的影响。

Immersing carbon nano-tubes in cold atomic gases

We investigate the sympathetic relaxation of a free-standing, vibrating carbon nano-tube that is mounted on an atom chip and is immersed in a cloud of ultra-cold atoms. Gas atoms colliding with the nano-tube excite phonons via a Casimir-Polder potential. We use Fermi's Golden Rule to estimate the relaxation rates for relevant experimental parameters and develop a fully dynamic theory of relaxation for the multi-mode phononic field embedded in a thermal atomic reservoir. Based on currently available experimental data, we identify the relaxation rates as a function of atom density and temperatur…

Dynamics and equilibration of Rydberg excitations in dissipative atomic ensembles

We study resonant optical excitations of strongly-interacting Rydberg states of atoms in the presence of relaxations. We employ the quantum stochastic (Monte Carlo) wavefunctions to simulate the dissipative dynamics of tens of atoms in two-dimensional lattices. We show that under typical experimental conditions involving slow Rydberg state decay and sizable relaxation of atomic coherences, on the time scale of several microseconds the atomic ensemble approaches a stationary state in which much of the quantum correlations between the atoms have decayed away. The steady state, however, exhibits …

Dynamics of a single ion spin impurity in a spin-polarized atomic bath

We report on observations of spin dynamics in single Yb$^+$ ions immersed in a cold cloud of spin-polarized $^6$Li atoms. This species combination has been proposed to be the most suitable system to reach the quantum regime in atom-ion experiments. For $^{174}$Yb$^+$, we find that the atomic bath polarizes the spin of the ion by 93(4)\,\% after a few Langevin collisions, pointing to strong spin-exchange rates. For the hyperfine ground states of $^{171}$Yb$^+$, we also find strong rates towards spin polarization. However, relaxation towards the $F=0$ ground state occurs after 7.7(1.5) Langevin …