Atomic Physics

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Engineering Quantum States of Matter for Atomic Clocks in Shallow Optical Lattices (1903.02498v1)

Ross B. Hutson, Akihisa Goban, G. Edward Marti, Jun Ye

2019-03-06

We investigate the effects of stimulated scattering of optical lattice photons on atomic coherence times in a state-of-the art optical lattice clock. Such scattering processes are found to limit the achievable coherence times to less than 10 s, significantly shorter than the predicted 145(40) s lifetime of 's excited clock state. We suggest that shallow, state-independent optical lattices with increased lattice constants can give rise to sufficiently small lattice photon scattering and motional dephasing rates as to enable coherence times on the order of the clock transition's natural lifetime. Not only should this scheme be compatible with the relatively high atomic density associated with Fermi-degenerate gases in three-dimensional optical lattices, but we anticipate that certain properties of various quantum states of matter can be used to suppress dephasing due to tunneling.

Direct Numerical Observation of Real-Space Recollision in High-Harmonic Generation from Solids (1903.02264v1)

Mrudul M. S., Adhip Pattanayak, Misha Ivanov, Gopal Dixit

2019-03-06

Real-space picture of electron recollision with the parent ion guides our understanding of the highly nonlinear response of atoms and molecules to intense low-frequency laser fields. It is also among several leading contestants for the dominant mechanism of high harmonic generation (HHG) in solids, where it is typically viewed in the momentum space, as the recombination of the conduction band electron with the valence band hole, competing with another HHG mechanism, the strong-field driven Bloch oscillations. In this work, we use numerical simulations to directly test and confirm the real-space recollision picture as the key mechanism of HHG in solids. Our tests take advantage of the well-known characteristic features in the molecular harmonic spectra, associated with the real-space structure of the molecular ion. We show the emergence of analogous spectral features when similar real-space structures are present in the periodic potential of the solid-state lattice. This work demonstrates the capability of HHG imaging of spatial structures of a unit cell in solids.

Ab initio QED treatment of the two-photon annihilation of positrons with bound electrons (1903.02243v1)

V. A. Zaytsev, A. V. Volotka, D. Yu, S. Fritzsche, X. Ma, H. Hu, V. M. Shabaev

2019-03-06

The process of a positron bound-electron annihilation with simultaneous emission of two photons is investigated theoretically. A fully relativistic formalism based on QED description of the process is worked out. The developed approach is applied to evaluate the annihilation of a positron with -shell electrons of a silver atom, for which a strong contradiction between theory and experiment was previously stated. The results obtained here resolve this long-standing disagreement and, moreover, demonstrate a sizeable difference with approaches so far used for calculations of the positron bound-electron annihilation process, namely, the and approximations.

Quasi-stable quantum vortex knots and links in anisotropic harmonically trapped Bose-Einstein condensates (1903.02042v1)

Christopher Ticknor, Victor P. Ruban, P. G. Kevrekidis

2019-03-05

Long-time existence of topologically nontrivial configurations of quantum vortices in the form of torus knots and links in trapped Bose-Einstein condensates is demonstrated numerically within the three-dimensional Gross-Pitaevskii equation with external anisotropic parabolic potential. We find out parametric domains near the trap anisotropy -- axial over planar frequency trapping ratio where the lifetime of such quasi-stationary rotating vortex structures is many hundreds of typical rotation times. This suggests the potential experimental observability of the structures. We quantify the relevant lifetimes as a function of the model parameters (e.g. ) and initial condition parameters of the knot profile.

Cesium bright matter-wave solitons and soliton trains (1902.03144v2)

Tadej Mežnaršič, Tina Arh, Jure Brence, Jaka Pišljar, Katja Gosar, Žiga Gosar, Rok Žitko, Erik Zupanič, Peter Jeglič

2019-02-08

A study of bright matter-wave solitons of a cesium Bose-Einstein condensate (BEC) is presented. Production of a single soliton is demonstrated and dependence of soliton atom number on the interatomic interaction is investigated. Formation of soliton trains in the quasi one-dimensional confinement is shown. Additionally, fragmentation of a BEC has been observed outside confinement, in free space. In the end a double BEC production setup for studying soliton collisions is described.

Pair fraction in a finite temperature Fermi gas on the BEC side of the BCS-BEC crossover (1803.10598v4)

Thomas Paintner, Daniel K. Hoffmann, Manuel Jäger, Wolfgang Limmer, Wladimir Schoch, Benjamin Deissler, Michele Pini, Pierbiagio Pieri, Giancarlo Calvanese Strinati, Cheng Chin, Johannes Hecker Denschlag

2018-03-28

We investigate pairing in a strongly interacting two-component Fermi gas with positive scattering length. In this regime, pairing occurs at temperatures above the superfluid critical temperature; unbound fermions and pairs coexist in thermal equilibrium. Measuring the total number of these fermion pairs in the gas we systematically investigate the phases in the sectors of pseudogap and preformed-pair. Our measurements quantitatively test predictions from two theoretical models. Interestingly, we find that already a model based on classical atom-molecule equilibrium describes our data quite well.

Observation of CPT for the ground hyperfine interval in Cs (1710.10788v2)

Sumanta Khan, Vineet Bharti, Vasant Natarajan

2017-10-30

We use the technique of coherent population trapping (CPT) to access the ground hyperfine interval (clock transition) in Cs. The probe and control beams required for CPT are obtained from a single compact diode laser system. The phase coherence between the beams, whose frequency difference is the clock frequency, is obtained by frequency modulating the laser with an electro-optic modulator (EOM). The EOM is fiber coupled and hence does not require alignment, and the atoms are contained in a vapor cell. Both of these should prove advantageous for potential use as atomic clocks in satellites.

Revisiting spin-dependent forces mediated by new bosons: Potentials in the coordinate-space representation for macroscopic- and atomic-scale experiments (1810.10364v2)

Pavel Fadeev, Yevgeny V. Stadnik, Filip Ficek, Mikhail G. Kozlov, Victor V. Flambaum, Dmitry Budker

2018-10-24

The exchange of spin-0 or spin-1 bosons between fermions or spin-polarised macroscopic objects gives rise to various spin-dependent potentials. We derive the coordinate-space non-relativistic potentials induced by the exchange of such bosons, including contact terms that can play an important role in atomic-scale phenomena, and correct for errors and omissions in the literature. We summarise the properties of the potentials and their relevance for various types of experiments. These potentials underpin the interpretation of experiments that search for new bosons, including spectroscopy, torsion-pendulum measurements, magnetometry, parity nonconservation and electric dipole moment experiments.

Suppressed spontaneous emission for coherent momentum transfer (1903.01627v1)

Xueping Long, Seejia S. Yu, Andrew M. Jayich, Wesley C. Campbell

2019-03-05

Strong optical forces with minimal spontaneous emission are desired for molecular deceleration and atom interferometry applications. We report experimental benchmarking of such a stimulated optical force driven by ultrafast laser pulses. We apply this technique to accelerate atoms, demonstrating an average of momentum transfers per spontaneous emission event. This represents more than an order of magnitude improvement in suppression of spontaneous emission compared to radiative scattering forces. For molecular beam slowing, this technique is capable of delivering a many-fold increase in the achievable time-averaged force to significantly reduce both the slowing distance and detrimental losses to dark vibrational states.

Implementing the three-particle quantization condition including higher partial waves (1901.07095v2)

Tyler D. Blanton, Fernando Romero-López, Stephen R. Sharpe

2019-01-21

We present an implementation of the relativistic three-particle quantization condition including both - and -wave two-particle channels. For this, we develop a systematic expansion about threshold of the three-particle divergence-free K matrix, , which is a generalization of the effective range expansion of the two-particle K matrix, . Relativistic invariance plays an important role in this expansion. We find that -wave two-particle channels enter first at quadratic order. We explain how to implement the resulting multichannel quantization condition, and present several examples of its application. We derive the leading dependence of the threshold three-particle state on the two-particle -wave scattering amplitude, and use this to test our implementation. We show how strong two-particle -wave interactions can lead to significant effects on the finite-volume three-particle spectrum, including the possibility of a generalized three-particle Efimov-like bound state. We also explore the application to the system, which is accessible to lattice QCD simulations, where we study the sensitivity of the spectrum to the components of . Finally, we investigate the circumstances under which the quantization condition has unphysical solutions.

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