J. E. Palmer, S. D. Hogan
2019-07-17
Matter-wave interferometry has been performed with helium atoms in high Rydberg states. In the experiments the atoms were prepared in coherent superpositions of Rydberg states with different electric dipole moments. Upon the application of an inhomogeneous electric field, the different forces on these internal state components resulted in the generation of coherent superpositions of momentum states. Using a sequence of microwave and electric field gradient pulses the internal Rydberg states were entangled with the momentum states associated with the external motion of these matter waves. Under these conditions matter-wave interference was observed by monitoring the populations of the Rydberg states as the magnitudes and durations of the pulsed electric field gradients were adjusted. The results of the experiments have been compared to, and are in excellent quantitative agreement with, matter-wave interference patterns calculated for the corresponding pulse sequences. For the Rydberg states used, the spatial extent of the Rydberg electron wavefunction was ~320 nm. Matter-wave interferometry with such giant atoms is of interest in the exploration of the boundary between quantum and classical mechanics. The results presented also open new possibilities for measurements of the acceleration of Rydberg positronium or antihydrogen atoms in the Earth's gravitational field.
Robert J. Bettles, Mark D. Lee, Simon A. Gardiner, Janne Ruostekoski
2019-07-16
We identify significant quantum many-body effects, robust to position fluctuations and strong dipole--dipole interactions, in the forward light scattering from planar arrays and uniform-density disks of cold atoms, by comparing stochastic electrodynamics simulations of a quantum master equation and of a semiclassical model that neglects quantum fluctuations. Quantum effects are pronounced at high atomic densities with the light close to saturation intensity, and especially at subradiant resonances. We find an enhanced semiclassical model with a single-atom quantum description provides good qualitative, and frequently quantitative agreement with the full quantum solution. We use the semiclassical simulations for large ensembles that would otherwise be numerically inaccessible, and observe collective many-body analogues of resonance power broadening and vacuum Rabi splitting, as well as significant suppression in cooperative reflection from atom arrays.
A. A. Zyablovsky, I. V. Doronin, E. S. Andrianov, A. A. Pukhov, Yu. E. Lozovik, A. P. Vinogradov, A. A. Lisyansky
2019-07-17
It is commonly accepted that a collection of pumped atoms without a resonator, which provides feedback, cannot lase. We show that intermodal coupling via active atoms pulls the frequencies of the free-space modes towards the transition frequency of the atoms. Although at a low pump rate mode phases randomly fluctuate, phase realizations at which interference of pulled modes is constructive emerge. This results in an increase of stimulated emission into such realizations and makes their lifetime longer. Thus, mode pulling provides positive feedback. When the pump rate exceeds a certain threshold, the lifetime of one of the realizations diverges, and radiation becomes coherent.
Moonjoo Lee, Minjae Lee, Seokjun Hong, Klemens Schüppert, Yeong-Dae Kwon, Taehyun Kim, Yves Colombe, Tracy E. Northup, Dong-Il "Dan" Cho, Rainer Blatt
2019-07-17
We present a numerical study of a MEMS-based design of a fiber cavity integrated with an ion trap system. Each fiber mirror is supported by a microactuator that controls the mirror's position in three dimensions. The mechanical stability is investigated by a feasibility analysis showing that the actuator offers a stable support of the fiber. The actuators move the fibers' positions continuously with a stroke of more than 10
m, with mechanical resonance frequencies on the order of kHz. A calculation of the trapping potential shows that a separation between ion and fiber consistent with strong ion-cavity coupling is feasible. Our miniaturized ion-photon interface constitutes a viable approach to integrated hardware for quantum information.
E. R. Moan, R. A. Horne, T. Arpornthip, Z. Luo, A. J. Fallon, S. J. Berl, C. A. Sackett
2019-07-11
Sensitive and accurate rotation sensing is a critical requirement for applications such as inertial navigation [1], north-finding [2], geophysical analysis [3], and tests of general relativity [4]. One effective technique used for rotation sensing is Sagnac interferometry, in which a wave is split, traverses two paths that enclose an area, and then recombined. The resulting interference signal depends on the rotation rate of the system and the area enclosed by the paths [5]. Optical Sagnac interferometers are an important component in present-day navigation systems [6], but suffer from limited sensitivity and stability. Interferometers using matter waves are intrinsically more sensitive and have demonstrated superior gyroscope performance [7-9], but the benefits have not been large enough to offset the substantial increase in apparatus size and complexity that atomic systems require. It has long been hoped that these problems might be overcome using atoms confined in a guiding potential or trap, as opposed to atoms falling in free space [10-12]. This allows the atoms to be supported against gravity, so a long measurement time can be achieved without requiring a large drop distance. The guiding potential can also be used to control the trajectory of the atoms, causing them to move in a circular loop that provides the optimum enclosed area for a given linear size [13]. Here we use such an approach to demonstrate a rotation measurement with Earth-rate sensitivity.
Huayu Hu
2019-07-08
Researches on the electron-positron pair production in the presence of the intense laser field are reviewed, motivated by the theoretical importance of the nonperturbative QED problem and the worldwide development of the strong laser facilities. According to distinct experimental requirements and theoretical methods, two types of pair production are elaborated, which are respectively the pair production in the combination of a seed particle and the strong laser, and vacuum pair production without a seed particle. The origin of the nonperturbative problem caused by the strong field is analyzed. The main ideas, realization, achievements, validity, challenges and bottleneck problems of the nonperturbative methods developed for each type of the pair production problem are discussed.
V. V. Flambaum, H. Feldmeier
2019-07-17
Octupole deformation results in strongly enhanced collective nuclear Schiff moments. In nuclear isotopes which are neighbours to the nuclei with the static octupole there is a soft octupole vibration mode which also leads to the enhancement of the Schiff moment. These mechanisms produce enhanced Schiff moments in stable and very long lifetime nuclei such as 153Eu, 235U and 237Np. Interaction between electrons and these Schiff moments produce enhanced time reversal (T) and parity (P) violating electric dipole moments (EDM) in atoms and molecules. Corresponding experiments may be used to test CP-violation theories predicting T,P-violating nuclear forces and to search for axions.
V. V. Flambaum, V. A. Dzuba
2019-07-17
It is usually assumed that the field isotope shift (FIS) is completely determined by the change of the averaged squared values of the nuclear charge radius
. Relativistic corrections modify the expression for FIS, which is actually described by the change of , where . In the present paper we consider corrections to FIS which are due to the nuclear deformation and due to the predicted reduced charge density in the middle of the superheavy nuclei produced by a very strong proton repulsion (hole in the nuclear centre). Specifically, we investigate effects which can not be completely reduced to the change of or .
Karol Kozioł
2019-07-17
The groundstates and low-lying states of W IX (W
), W X (W ), and W XI (W ) tungsten ions related to and valence configurations have been studied theoretically, employing the multi-configuration Dirac-Hartree-Fock method with configuration interaction. The aim of present research is to fill a lack of atomic data for these tungsten ionization stages, which may help in identification of the measured complex spectra and be a base for collisional-radiative modeling for spectra of tungsten ions occurring in plasma.
Karol Kozioł
2019-07-17
The FAC, GRASP2K, and MCDFGME codes are compared in three case study of radiative transitions occurring in tungsten ions: (i) Ni1 and Ni2 lines in Ni-like tungsten, (ii)
hyperfine splitting in Cl-like tungsten, and (iii) and lines in W VIII. Various approaches to include Breit interaction term and QED corrections in atomic calculations are examined. Electron correlation effects are also investigated. The presented data may be used to estimate the theoretical uncertainties relevant to interpretation of high-resolution spectroscopic data.
