Simanraj Sadana, Debadrita Ghosh, Kaushik Joarder, A. Naga Lakshmi, Barry C. Sanders, Urbasi Sinha
2018-10-02
The Hong-Ou-Mandel effect is considered a signature of the quantumness of light, as the dip in coincidence probability using semi-classical theories has an upper bound of 50%. Here we show, theoretically and experimentally, that, with proper phase control of the signals, classical pulses can mimic a Hong-Ou-Mandel-like dip. We demonstrate a dip of 99.635 +/- 0.002% with classical microwave fields. Quantumness manifests in wave-particle complementarity of the two-photon state. We construct quantum and classical interferometers for the complementarity test and show that while the two-photon state shows wave-particle complementarity, the classical pulses do not.
Manuel J. Gutiérrez, Joaquín Berrocal, Francisco Domínguez, Iñigo Arrazola, Michael Block, Enrique Solano, Daniel Rodríguez
2019-07-18
In this article, the dynamics of an unbalanced two-ion crystal comprising the 'target' and the 'sensor' ions confined in a Penning trap has been studied. First, the low amplitude regime is addressed. In this regime, the overall potential including the Coulomb repulsion between the ions can be considered harmonic and the axial, magnetron and reduced-cyclotron modes split up into the so-called 'stretch' and 'common' modes, that are generalizations of the well-known 'breathing' and 'center-of-mass' motions of a balanced crystal made of two ions. By measuring the frequency modes of the crystal and the sensor ion eigenfrequencies using optical detection, it will be possible to determine the target ion's free-cyclotron frequency. The measurement scheme is described and the non-harmonicity of the Coulomb interaction is discussed since this might cause large systematic effects.
J. Sommerfeldt, R. A. Müller, A. N. Artemyev, A. Surzhykov
2019-07-18
We present a theoretical study of bound-free electron-positron pair production in the interaction of
-rays with bare ions. Special attention is paid to the longitudinal polarization of both the emitted positrons and the produced hydrogen-like ions. To evaluate this polarization we employed exact solutions of the relativistic Dirac equation and treat the electron-photon coupling within the framework of first-order perturbation theory. Detailed calculations have been performed for both, low- and high-Z ions and for a wide range of photon energies. The results of these calculations suggest that bound-free pair production can be a source of strongly polarized positrons and ions.
Václav Hanus, Sarayoo Kangaparambil, Martin Dorner-Kirchner, Xinhua Xie, Markus S. Schöffler, Gerhard G. Paulus, Andrius Baltuška, André Staudte, Markus Kitzler-Zeiler
2019-07-18
We report on the unambiguous observation of the sub-cycle ionization bursts in sequential double ionization of H
and their disentanglement in molecular frame photoelectron angular distributions. The observation was made using a coincidence momentum spectroscopy and few-cycle laser pulses with a known carrier-envelope phase focused to the intensity of W/cm . We envision that the approach demonstrated here can be extended to polyatomic molecules where it should allow sampling of the intramolecular electron dynamics.
A. V. Volotka, M. Bilal, R. Beerwerth, X. Ma, Th. Stöhlker, S. Fritzsche
2019-07-18
Ab initio calculations of QED radiative corrections to the
- fine-structure transition energy are performed for selected F-like ions. These calculations are nonperturbative in and include all first-order and many-electron second-order effects in . When compared to approximate QED computations, a notable discrepancy is found especially for F-like uranium for which the predicted self-energy contributions even differ in sign. Moreover, all deviations between theory and experiment for the - fine-structure energies of F-like ions, reported recently by Li et al., Phys. Rev. A 98, 020502(R) (2018), are resolved if their highly accurate, non-QED fine-structure values are combined with the QED corrections ab initially evaluated here.
Y. N. Zuo, J. Z. Han, J. W. Zhang, L. J. Wang
2019-02-28
This paper reports the direct temperature determination of sympathetically cooled 113Cd+ ions with laser-cooled 24Mg+ in a linear Paul trap. The sympathetically cooled ion species distribute in the outer shell of the large ensembles, which contain up to 3.3E5 ions. With optimized parameters, the minimum temperature of the sympathetically cooled 113Cd+ ions was measured to be tens of mK. These results indicate promising performance for microwave atomic clocks. The second order Doppler frequency shift is two orders of magnitudes lower and the Dick effect is suppressed.
Raghwinder S. Grewal, Gour S. Pati, Renu Tripathi, Anthony W. Yu, Michael Krainak, Michael Purucker
2019-07-17
We report on magneto-optical resonances observed in sodium fluorescence from D2 manifold with an intensity modulated light illuminating a sodium (Na) cell containing Ne buffer gas. Resonances are measured in fluorescence emitted perpendicular and backward to the light propagation direction in the cell. Properties of these resonances are studied by varying the magnetic field at fixed light modulation frequency, and vice-versa. A dark resonance having maximum amplitude for laser wavelength close to the crossover peak, is observed. The origin of dark resonance observed in Na D2 line is discussed. Pulse modulation with low-duty cycle shows higher-harmonic resonances of the modulation frequency and sub-harmonic resonances of the Larmor frequency. Present study is aimed towards improving the understanding of magneto-optical resonances for remote magnetometry applications with mesospheric sodium.
John Sous, H. R. Sadeghpour, T. C. Killian, Eugene Demler, Richard Schmidt
2019-07-17
We consider the quench of an atomic impurity via a single Rydberg excitation in a degenerate Fermi gas. The Rydberg interaction with the background gas particles induces an ultralong-range potential that binds particles to form dimers, trimers, tetramers, etc. Such oligomeric molecules were recently observed in atomic Bose-Einstein condensates. In this work, we demonstrate with a functional determinant approach that quantum statistics and fluctuations have observable spectral consequences. We show that the occupation of molecular states is predicated on the Fermi statistics, which suppresses molecular formation in an emergent molecular shell structure. At large gas densities this leads to spectral narrowing, which can serve as a probe of the quantum gas thermodynamic properties.
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.
