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Fisher Information and Atomic Structure

We present a comparative study of several information and statistical complexity measures in order to examine a possible correlation with certain experimental properties of atomic structure. Comparisons are also carried out quantitatively using Pearson correlation coefficient. In particular, we show that Fisher information in momentum space is very sensitive to shell effects, and is directly associated with some of the most characteristic atomic properties, such as atomic radius, ionization energy, electronegativity, and atomic dipole polarizability. Finally we present a relation that emerges between Fisher information and the second moment of the probability distribution in momentum space i.e. an energy functional of interest in (e,2e) experiments.

quant-ph↗

Differential atom interferometry with $^{87}$Rb and $^{85}$Rb for testing the UFF in STE-QUEST

In this paper we discuss in detail an experimental scheme to test the universality of free fall (UFF) with a differential $^{87}$Rb / $^{85}$Rb atom interferometer applicable for extended free fall of several seconds in the frame of the STE-QUEST mission. This analysis focuses on suppression of noise and error sources which would limit the accuracy of a violation measurement. We show that the choice of atomic species and the correctly matched parameters of the interferometer sequence are of utmost importance to suppress leading order phase shifts. In conclusion we will show the expected performance of $2$ parts in $10^{15}$ of such an interferometer for a test of the UFF.

physics.atom-ph↗

Quantum mechanics, matter waves, and moving clocks

This paper is divided into three parts. In the first (section 1), we demonstrate that all of quantum mechanics can be derived from the fundamental property that the propagation of a matter wave packet is described by the same gravitational and kinematic time dilation that applies to a clock. We will do so in several steps, first deriving the Schroedinger equation for a nonrelativistic particle without spin in a weak gravitational potential, and eventually the Dirac equation in curved space-time describing the propagation of a relativistic particle with spin in strong gravity. In the second part (sections 2-4), we present interesting consequences of the above quantum mechanics: that it is possible to use wave packets as a reference for a clock, to test general relativity, and to realize a mass standard based on a proposed redefinition of the international system of units, wherein the Planck constant would be assigned a fixed value. The clock achieved an absolute accuracy of 4 parts per billion (ppb). The experiment yields the fine structure constant $α= 7.297\,352\,589(15) \times 10^{-3}$ with 2.0 ppb accuracy. We present improvements that have reduced the leading systematic error about 8-fold and improved the statistical uncertainty to 0.33 ppb in 6 hours of integration time, referred to $α$. In the third part (sections 5-7), we present possible future experiments with atom interferometry: A gravitational Aharonov-Bohm experiment and its application as a measurement of Newton's gravitational constant, antimatter interferometry, interferometry with charged particles, and interferometry in space. We will give a review of previously published material when appropriate, but will focus on new aspects that haven't been published before.

quant-ph↗

Multiconfiguration Dirac-Hartree-Fock calculations of atomic electric dipole moments of 225^Ra, 199^Hg, and 171^Yb

The multiconfiguration Dirac-Hartree-Fock (MCDHF) method has been employed to calculate atomic electric dipole moments (EDM) of 225^Ra, 199^Hg, and 171^Yb. For the calculations of the matrix elements we extended the relativistic atomic structure package GRASP2K. The extension includes programs to evaluate matrix elements of (P, T)-odd e-N tensor-pseudotensor and pseudoscalar-scalar interactions, the atomic electric dipole interaction, the nuclear Schiff moment, and the interaction of the electron electric dipole moment with nuclear magnetic moments. The interelectronic interactions were accounted for through valence and core-valence electron correlation effects. The electron shell relaxation was included with separately optimised wave functions of opposite parities.

physics.atom-ph↗

Tunable lattice Induced Opacity in atom-lattice interaction

A lattice-induced opacity is identified in the scattering process of a normally-incident matter wave from a two dimensional lattice of atoms. This system can be treated as an analogue of a confinement induced resonance. Specifically by modifying the s-wave scattering length between atoms in the incident matter wave and the lattice-confined atoms, the transmission of the matter wave can be tuned controllably from zero to one. Based on this, we propose a possible scheme for a matter wave transistor. When the transmission of the matter wave is tuned to zero, a matter wave cavity can be formed by placing two such lattice planes of atoms parallel to one another. At higher kinetic energies, the two dimensional lattice of atoms can also serve as a matter wave beam splitter and a wave plate.

physics.atom-ph↗

Transient coherence of an EIT media under strong phase modulation

A strong phase modulated coupling field leads to an amplitude modulation of a probe field in an electromagnetically induced transparency process. Time vs. detuning plots for different modulation frequencies reveals a transition between an adiabatic regime where a series of smooth pulses are created with a global phase dependent upon the detuning, and a non-adiabatic regime where a strong transient oscillating response is added to these pulses. In the extreme non-adiabatic regime, where the modulation frequency is higher than the transient decay time, a coherent interference pattern is revealed. Adding a magnetic field lifts the hyperfine level degeneracy, resulting in a separation of the original pulse to three pulses. Every pulse has now a different phase dependent upon the magnetic field causing an interference effect between the different magnetic level transients. We explore the dynamics of the magnetic and non magnetic cases and show its resemblance to the Landau-Zener theory. We also show that combining the global phase of the pulses with the transient interference allows for a wide magnetic sensing range without loosing the sensitivity of a single EIT line.

quant-ph↗

Ion-atom hybrid systems

The study of interactions between simultaneously trapped cold ions and atoms has emerged as a new research direction in recent years. The development of ion-atom hybrid experiments has paved the way for investigating elastic, inelastic and reactive collisions between these species at very low temperatures, for exploring new cooling mechanisms of ions by atoms and for implementing new hybrid quantum systems. The present lecture reviews experimental methods, recent results and upcoming developments in this emerging field.

physics.atom-ph↗

The effect of Landau-Zener tunnelings on the nonlinear dynamics of cold atoms in a modulated laser field

We study the motion of a cold atom in a frequency-modulated standing laser wave. If the detuning between the atomic electronic transition and the field is large, the atom moves in a modulated optical potential demonstrating known classical nonlinear effects such as chaos and nonlinear resonances. If the atom-field detuning is small, then two optical potentials emerge in the system, and the atom performs Landau-Zener (LZ) tunnelings between them. It is a radically non-classical behavior. However, we show that classical nonlinear structures in system's phase space (KAM-tori and chaotic layers) survive. Quantum effect of LZ tunnelings only induces small random jumps of trajectories between these structures (dynamical tunneling).

physics.atom-ph↗

Trapping of slow-speed particles in a gas cell by the nonhomogeneous electromagnetic field intensifying with time

Author suggests and analyzes new universal trapping method of comparatively slow-speed particles of a rarefied gas medium in the potential well induced by the nonhomogeneous electromagnetic field increasing with time (up to some moment). Given method is especially effective at inelastic collisions of particles with walls of the gas cell when necessary preliminary slowdown of particles is possible for their following capture even to a highly shallow potential depth. Corresponding sufficiently compact and simple electromagnetic traps may be used for capture and accumulation not only slow-speed micro- and nano-particles in the high vacuum but also atoms and molecules of a rarefied gas in a cell.

physics.gen-ph↗

Generation of Pulse Sequences with Periodic Spectral Phase Masks

We present a method for the generation of complex pulse sequences by using periodic spectral phase modulation. An analytical expression is derived for the temporal profile of such pulse sequences, which relates the temporal amplitudes and phases of the subpulses to the Fourier components of the periodic phase mask. We consider two families of periodic phase masks, namely, when a single period is an odd or even function, and discuss the differences between the resulting pulse sequences. The ability to generate pulse sequences with more degrees of freedom provides an alternative parametrization for investigating quantum coherent control landscapes. This is illustrated in the context of dark pulses in nonresonant two-photon absorption.

physics.optics↗

Hybrid quantum systems of ions and atoms

In this chapter we review the progress in experiments with hybrid systems of trapped ions and ultracold neutral atoms. We give a theoretical overview over the atom-ion interactions in the cold regime and give a summary of the most important experimental results. We conclude with an overview of remaining open challenges and possible applications in hybrid quantum systems of ions and neutral atoms.

cond-mat.quant-gas↗

Coherent manipulation of four-level double lambda-like atomic system by a train of ultra-short few-cycle-optical pulses

We have demonstrated that near complete coherence can be achieved in a four level double lambda-like systems using a train of ultra-short optical pulses. The effect of the Doppler broadening has been analyzed and a scheme has been proposed for establishing high and uniform coherence across different velocity groups in the atomic ensemble. We have also presented a novel scheme of excitation using chirped pulses and shown that in addition to generating coherence in the system it is possible to alter the translational states of the atoms.

physics.optics↗

Two-color pump-probe dynamics of transitions between doubly excited states of Helium

We discuss the dynamics of the two-photon resonant ionization of helium involving two autoionizing states in the presence of two-color laser fields. The first source is tuned around the transition from the ground state to the 2s2p 1Po autoionizing state, and the second couples the state 2s2p 1Po to the 2p2 1S autoionizing state. The laser coupling between the doubly excited states is shown to lead to modifications of the Beutler-Fano profile and the appearance of an Autler-Townes doublet. This double resonance effect between autoionizing states can be observed at moderate laser intensities easily attainable by currently operated sources.

physics.atom-ph↗

Boundary conditions effects on the ground state of a two-electron atom in a vacuum cavity

The ground state properties of the two-electron atom with atomic number $Z\geq 2$ in the spherical vacuum cavity with general boundary conditions of "not going out" are studied. It is shown that for certain parameters of the cavity such atom could either decay into the one-electron atom with the same atomic number and an electron or be in stable state with the binding and ionization energies several times bigger than the same energies of the free atom. By analogy with the Wigner-Seitz model of metallic bonding, the possibility of the existence of such effects on the lattice formed by the vacuum cavities filled with the two-electron atoms of the same type is discussed.

physics.atom-ph↗

Optimizing a spin-flip Zeeman slower

We present a design of a spin-flip Zeeman slower controlled by a fast feedback circuit for a sodium Bose-Einstein condensate apparatus. We also demonstrate how the efficiency of the slower strongly depends on its intrinsic parameters, and compare these observations with a few theoretical models. Our findings lead to a simple three-step procedure of designing an optimal Zeeman slower for neutral atoms, especially for those atomic species with high initial velocities, such as sodium and lithium atoms.

cond-mat.quant-gas↗

Complete-return spectrum for a generalized Rosen-Zener two-state term-crossing model

The general semiclassical time-dependent two-state problem is considered for a specific field configuration referred to as the generalized Rosen-Zener model. This is a rich family of pulse amplitude- and phase-modulation functions describing both non-crossing and term-crossing models with one or two crossing points. The model includes the original constant-detuning non-crossing Rosen-Zener model as a particular case. We show that the governing system of equations is reduced to a confluent Heun equation. When inspecting the conditions for returning the system to the initial state at the end of the interaction with the field, we reformulate the problem as an eigenvalue problem for the peak Rabi frequency and apply the Rayleigh-Schrödinger perturbation theory. Further, we develop a generalized approach for finding the higher-order approximations, which is applicable for the whole variation region of the involved input parameters of the system. We examine the general surface in the 3D space of input parameters, which defines the position of the n-th order return-resonance, and show that the section of the general surface is accurately approximated by an ellipse. We find a highly accurate analytic description through the zeros of a Kummer confluent hypergeometric function. From the point of view of the generality, the analytical description of mentioned curve for the whole variation range of all involved parameters is the main result of the present paper.

physics.atom-ph↗

Super/Subradiant Second Harmonic Generation

A scheme for active second harmonics generation is suggested. The system comprises $N$ three-level atoms in ladder configuration, situated into resonant cavity. It is found that the system can lase in either superradiant or subradiant regime, depending on the number of atoms $N$. When N passes some critical value the transition from the super to subradiance occurs in a phase-transition-like manner. Stability study of the steady state supports this conclusion.

physics.optics↗

Simple Molecules and Clocks

The precise measurement of transition frequencies in cold, trapped molecules has applications in fundamental physics, and extremely high accuracies are desirable. We determine suitable candidates by considering simple molecules with a single electron, for which the external-field shift coefficients can be calculated with high precision. Our calculations show that $\Htwop$ exhibits particular transitions whose fractional uncertainties may reach $2\times10^{-17}$ at room temperature. We also generalize the method of composite frequencies, introducing tailored linear combinations of individual transition frequencies that are free of the major systematic shifts, independent of the strength of the external perturbing fields. By applying this technique, the uncertainty should be reduced to the $10^{-18}$ range for both $\Htwop$ and $\HDp$. Thus, the theoretical results demonstrate that these molecules are of metrological relevance for future studies.

physics.atom-ph↗