We present a quantum calculation of the electron degeneracy for electron sources. We explore quantum interference of electrons in the temporal and spatial domain and demonstrate how it can be utilized to characterize a pulsed electron source. We estimate effects of Coulomb repulsion on two-electron interference and show that currently available pulsed nanotip electron sources operate in the regime where the quantum nature of electrons can be made dominant.

We extend a model of two-center interference to include the superposition of opposite orientations in aligned polar molecules. We show that the position of the minimum in the harmonic spectrum from both aligned and oriented CO depends strongly on the relative recombination strength at different atoms, not just the relative phase. We reinterpret the minimum in aligned CO as an interference between opposite orientations, and obtain good agreement with numerical calculations. Inclusion of the first-order Stark effect shifts the position of the interference minimum in aligned CO even though aligned molecules do not posses total permanent dipoles. We explain the shift in terms of the phase that the electron of oriented CO accumulates due to the Stark effect.

We explore the Mott insulating state of single-band bosonic pairing Hamiltonians using analytical approaches and large-scale density matrix renormalization group calculations. We focus on the second Mott lobe which exhibits a magnetic quantum phase transition in the Ising universality class. We use this feature to discuss the behavior of a range of physical observables within the framework of the one-dimensional quantum Ising model and the strongly anisotropic Heisenberg model. This includes the properties of local expectation values and correlation functions both at and away from criticality. Depending on the microscopic interactions it is possible to achieve either antiferromagnetic or ferromagnetic exchange interactions and we highlight the possibility of observing the $E_8$ mass spectrum for the critical Ising model in a longitudinal magnetic field.

We investigate the isobar of an ideal Bose gas confined in a cubic box within the grand canonical ensemble for a large yet finite number of particles, $N$. After solving the equation of the spinodal curve, we derive precise formulas for the supercooling and the superheating temperatures that reveal an $N^{-1/3}$ or $N^{-1/4}$ power correction to the known Bose-Einstein condensation temperature in the thermodynamic limit. Numerical computations confirm the accuracy of our analytical approximation, and further show that the isobar zigzags on the temperature-volume plane if $N\ge 14393$. In particular, for the Avogadro’s number of particles, the volume expands discretely about ${10}^5$ times. Our results quantitatively agree with a previous study on the canonical ensemble within $0.1\%$ error.

We study the Kelvin mode excitations on a vortex line in a three-dimensional trapped Bose-Einstein condensate at finite temperature. Our stochastic Gross-Pitaevskii simulations show that the activation of these modes can be suppressed by tightening the confinement along the direction of the vortex line, leading to a strong suppression in the vortex decay rate as the system enters a regime of two-dimensional vortex dynamics. As the system approaches the condensation transition temperature, we find that the vortex decay rate is strongly sensitive to dimensionality and temperature, observing a large enhancement for quasi-two-dimensional traps. Three-dimensional simulations of the recent vortex dipole decay experiment of Neely et al. [Phys. Rev. Lett. 104, 160401 (2010)] confirm two-dimensional vortex dynamics and predict a dipole lifetime consistent with experimental observations and suppression of Kelvon-induced vortex decay in highly oblate condensates.

We investigate the attractive Hubbard model in infinite spatial dimensions by combining dynamical mean-field theory with a strong-coupling continuous-time quantum Monte Carlo method. By calculating the superfluid order parameter and the density of states, we discuss the stability of the superfluid state. In the intermediate-coupling region above the critical temperature, the density of states exhibits a heavy fermion behavior with a quasiparticle peak in the dense system, while a dip structure appears in the dilute system. The formation of the superfluid gap is also addressed.

Recently, it has been shown that spiral-shaped microdisk cavities support highly nonorthogonal pairs of copropagating modes with a preferred sense of rotation (spatial chirality) [J. Wiersig et al., Phys. Rev. A 78, 053809 (2008)]. Here, we provide numerical evidence which indicates that such pairs are a common feature of deformed microdisk cavities which lack mirror symmetries. In particular, we demonstrate that discontinuities of the cavity boundary such as the notch in the spiral cavity are not needed. We find a quantitative relation between the nonorthogonality and the chirality of the modes which agrees well with the predictions from an effective non-Hermitian Hamiltonian. A comparison to ray-tracing simulations is given.

In a recent paper [D. Chruściński and F. A. Wudarski, Open Sys. Information Dyn. (unpublished)], it was conjectured that the entanglement witnesses arising from some generalized Choi maps are optimal. We show that this conjecture is true. Furthermore, we show that they provide a one-parameter family of indecomposable optimal entanglement witnesses.

The triply degenerate ${\nu }_4$ bending mode of methane in superfluid helium nanodroplets was observed at 7.7 $\mu$m by high-resolution infrared depletion spectroscopy. Five rotational transitions were detected, with a minimum linewidth of only 65 MHz. The observed lines showed slightly asymmetric line shapes, especially in the case of the $P\left(2\right)$ and $R\left(1\right)$ rotational lines. Analysis of the line shape indicates that the superfluid environment has a finite response time of a few nanoseconds to equilibrate upon rotational excitation of CH${}_4$.

Laser spectroscopy of short-lived radium isotopes in a linear Paul trap has been performed. The isotope shifts of the $6d{{}^{2}D}_{3/2}$–$7p{{}^{2}P}_{1/2}$ transition in ${}^{209-214}$Ra${}^{+}$, which are sensitive to the short-range part of the atomic wave functions, were measured. The results are essential experimental input for improving the precision of atomic structure calculations. This is indispensable for parity violation in Ra${}^{+}$ aiming at the determination of the weak mixing angle.

High-order-harmonic generation from aligned N${}_2$, O${}_2$, and CO${}_2$ molecules is investigated by 1300-nm and 800-nm pulses. The harmonic intensities of 1300-nm pulses from aligned molecules show harmonic photon energy dependence similar to those of 800-nm pulses. Suppression of harmonic intensity from aligned CO${}_2$ molecules is observed for both 1300- and 800-nm pulses over the same harmonic photon energy range. As the dominant mechanism for the harmonic intensity suppression from aligned CO${}_2$ molecules, the present results support the two-center interference picture rather than the dynamical interference picture.

A Markovian dissipative quantum channel can generate quantum discord from some bipartite product states if and only if it cannot be reduced to individual decoherence channels independently acting on each qudit. As a byproduct, we also prove that proper individual decoherence can transform the classical correlation into quantum discord. Our result builds a tight connection between quantum discord and collective decoherence.

Measuring an entangled state of two particles is crucial to many quantum communication protocols. Yet Bell-state distinguishability using a finite apparatus obeying linear evolution and local measurement is theoretically limited. We extend known bounds for Bell-state distinguishability in one and two variables to the general case of entanglement in $n$ two-state variables. We show that at most $2^{n+1}-1$ classes out of $4^n$ hyper-Bell states can be distinguished with one copy of the input state. With two copies, complete distinguishability is possible. We present optimal schemes in each case.

We propose to use adiabatic rapid passage with a chirped laser pulse in the strong dipole blockade regime to deterministically excite only one Rydberg atom from randomly loaded optical dipole traps or optical lattices. The chirped laser excitation is shown to be insensitive to the random number $N$ of the atoms in the traps. Our method overcomes the problem of the $\sqrt{N}$ dependence of the collective Rabi frequency, which was the main obstacle for deterministic single-atom excitation in the ensembles with unknown $N$, and can be applied for single-atom loading of dipole traps and optical lattices.

This paper presents a general and rigorous transformation method to tailor planar conic reflectors. The proposed method enables the designed reflectors to scatter or reflect incident light in the same manner as a conic reflector while the whole device as well as the reflector would maintain planar profiles. In order to reduce the overall size, especially the aperture of the reflector, we further apply a set of compressed and folded spatial mapping to the planar reflectors. Planar reflectors with reduced sizes are finally obtained which may be useful in several optical and electromagnetic applications.

By considering the interaction between whispering-gallery modes of a spherical resonator and a subwavelength polarizable particle, we demonstrate that spatial confinement of the electromagnetic field dramatically changes the character of the optical forces exerted. We show that this phenomenon can be experimentally observed in the optically induced orbital motion of the particle.

We study the effect of dephasing on the coherent dissociation dynamics of an atom-molecule Bose-Einstein condensate. We show that when phase-noise intensity is strong with respect to the inverse correlation time of the stimulated process, dissociation is suppressed via a Bose enhanced quantum Zeno effect. This is complementary to the quantum Zeno control of phase-diffusion in a bimodal condensate by symmetric noise [Phys. Rev. Lett. 100, 220403 (2008)] in that the controlled process here is phase formation and the required decoherence mechanism for its suppression is purely phase noise.

Fermionic atoms in a periodic optical lattice provide a realization of the single-band Hubbard model. Using quantum Monte Carlo simulations along with the maximum-entropy method, we evaluate the effect of a time-dependent perturbative modulation of the optical lattice amplitude on atomic correlations, revealed in the fraction of doubly occupied sites. We find that the effect of modulation depends strongly on the filling—the response of the double occupation is significantly different in the half-filled Mott insulator from that in the doped Fermi liquid region.