We show that a dynamically evolving two-mode Bose-Einstein condensate (TBEC) with an adiabatic, time-varying Raman coupling maps exactly onto a Ramsey interferometer that includes a nonlinear medium. Assuming a realistic quantum state for the TBEC that has been achieved experimentally, we find that the measurement uncertainty of the “path-difference” phase shift scales as the standard quantum limit $\left(1/\sqrt{N}\right)$, where $N$ is the number of atoms, while that for the interatomic scattering strength scales as $1/N^{7/5}$, overcoming the conventional Heisenberg limit of $1/N$.

We investigate effects of optical lattice potential in one- and two-dimensional two-component trapped Fermi gases with population imbalances. Using the exact diagonalization and the density matrix renormalization group methods complementarily, we calculate the atom-density profile from the ground state many-body wave function as a function of attractive interaction strength for various population imbalances. The numerical results reveal that although a phase separation between the superfluid core and the shell cloud of excess atoms occurs as observed in experiments without the optical lattice, the population imbalance generally remains in the core region in contrast to the nonlattice cases. The essence of the numerical results in a strong attractive regime can be explained by an effective model composed of Cooper pairs and excess major fermions.

This paper discusses the possibility of developing a frequency standard using molecular vibrational transition frequencies, which are useful in optical communications. Cold molecules $\left(<300\mu \text{K}\right)$ are trapped by microwave or infrared laser light, whose frequency is chosen so that the Stark shift on the transition frequency is significantly reduced. Microwave trapping is much more advantageous than infrared trapping for measuring the vibrational transition frequency to within an uncertainty of ${10}^{-11}$.

We present the radial compression of an electron plasma by using a rotating wall in a spindle cusp region of an axisymmetric magnetic quadrupole. The compression rate depended on the rotating frequencies and had a broad peak extending on both sides of a longitudinal (1,0) mode frequency, which was the only observed characteristic frequency. The formation of the high-density plasma is one of the important milestones for the antihydrogen formation and extraction of ultraslow spin-polarized antihydrogen beams in the spindle cusp.

Quantum transition and information properties of the Coulomb coupled trion (electron-electron-hole) in the double quantum dots under the influence of the time-dependent electric field have been studied. Tuning the Hubbard interaction strength among the states of electron-hole complexes and the parameters of the ac field, two strikingly different kinds of approximate qubits can be constructed within the eight trion states. The similarity and difference between the electron dynamic entanglement and overlapping of the wave function with the Bell state have been elucidated through analyzing these two kinds of qubits.

Fluorescence of an organic-dye thin film induced by the impact of individual slow iodine highly charged ions (HCIs) has been investigated for a wide range of charge states $q$ from 30 (V-like ion) to 52 (H-like ion). Combined analysis of emission yields of the visible and x-ray photons reveal that $L$ Auger electrons emitted in the neutralization process of the HCI play an important role in the electronic excitation of the target. It is also noted that, contrary to the energy dissipation of $L$ Auger electrons, x rays carry away a large fraction of the potential energy of a HCI with higher $q$ than the Ne-like ion.

We investigate the existence and especially the linear stability of single- and multiple-charge quantized vortex states of nonlinear Schrödinger equations in the presence of a periodic and a parabolic potential in two spatial dimensions. The study is motivated by an examination of pancake-shaped Bose-Einstein condensates in the presence of magnetic and optical confinement. A two-parameter space of the condensate’s chemical potential versus the periodic potential’s strength is scanned for both single- and double-quantized vortex states located at a local minimum or a local maximum of the lattice. Triple-charged vortices are also briefly discussed. Single-charged vortices are found to be stable for cosinusoidal potentials and unstable for sinusoidal ones above a critical strength. Higher-charge vortices are more unstable for both types of potentials, and their dynamical evolution leads to a breakup into single-charged vortices.

The equation of state of the partially polarized two component Fermi gas at zero temperature in the unitary limit is computed by the ab initio auxiliary field Monte Carlo method. From this, we obtain the critical ratio of the chemical potentials ${\mu }_{\downarrow }∕{\mu }_{\uparrow }$ at the phase transitions. The value of ${\mu }_{\downarrow }∕{\mu }_{\uparrow }$ at the transition between the fully paired superfluid and the partially polarized phases is 0.11, while the critical value at the phase transition between the partially polarized phase and the fully polarized normal fluid is $-0.59$. We also determine the radial boundaries of the phase transitions of the Fermi gas in the harmonic trap as a function of the total polarization. We find that beyond the critical polarization 0.65, the fully paired superfluid core disappears in the trapped Fermi gas.

An algebraic method has been developed which allows one to engineer several energy levels including the low-energy subspace of interacting spin systems. By introducing ancillary qubits, this approach allows $\mathit{k}$-body interactions to be captured exactly using two-body Hamiltonians. Our method works when all terms in the Hamiltonian share the same basis and has no dependence on perturbation theory or the associated large spectral gap. Our methods allow problem instance solutions to be embedded into the ground energy state of Ising spin systems. Adiabatic evolution might then be used to place a computational system into its ground state.

The hyperfine-induced $2s2p{}^{3}P_0–2s^2{}^{1}S_0$ transition rate for Be-like ${}^{47}\mathrm{Ti}^{18+}$ was recently measured in a storage-ring experiment by Schippers et al. [Phys. Rev. Lett. 98, 033001 (2007)]. The measured value of $0.56\left(3\right){\mathrm{s}}^{-1}$ is almost 60% larger than the theoretical value of $0.356{\mathrm{s}}^{-1}$ from a multiconfiguration Dirac-Fock calculation by Marques et al. [Phys. Rev. A 47, 929 (1993)]. In this work, we use a large-scale relativistic configuration-interaction method to calculate these hyperfine-induced rates for ions with $Z=6–92$. Coherent hyperfine-quenching effects between the $2s2p{}^{1,3}P_1$ states are included in a perturbative as well as a radiation damping approach. Contrary to the claims of Marques et al., contributions from the ${}^{1}P_1$ state are substantial and lead to a hyperfine-induced rate of $0.67{\mathrm{s}}^{-1}$, in better agreement with, though larger than, the measured value.

Population dynamics in weakly excited clouds of ultracold ${}^{87}\text{R}\text{b}$ Rydberg atoms were studied by means of trap loss, fluorescence detection, and state-dependent stimulated emission. Rydberg atoms were excited to various $nl$ Rydberg states via continuous two-photon excitation from a magneto-optical trap. A stimulated emission probe laser was then used to bring the Rydberg atoms down to the $6P_{3/2}$ state, allowing state-dependent detection of the Rydberg atoms. Measurements of trap loss and fluorescent emission reveal information about the evolution of the Rydberg populations. In particular, population in the initial Rydberg state quickly transfers to other Rydberg states by a noncollisional mechanism, likely superradiant emission. The trap-loss measurements are consistent with black-body ionization as the dominant loss mechanism.

Single-electron ionization and excitation cross sections as well as cross sections for excitation into the first excited $p$ state of the alkali-metal atoms Li$\left(2s\right)$, Na$\left(3s\right)$, and K$\left(4s\right)$ colliding with antiprotons and protons were calculated using a time-dependent channel-coupling approach. For antiprotons an impact-energy range from 0.25 to 1000 keV and for protons from 2 to 1000 keV was considered. The target atoms are treated as effective one-electron systems using a model potential. The results are compared with theoretical and experimental data from literature and calculated cross sections for antiproton-hydrogen collisions. For proton collisions a good overall agreement is found that confirms the present numerical approach, whereas discrepancies are found between the present antiproton cross sections and those calculated by Stary et al. [C. Stary, H. J. Lüdde, and R. M. Dreizler, J. Phys. B 23, 263 (1990)].

The small doubly-charged molecular anion ${{\mathrm{SiF}}_6}^{2-}$ was studied by two distinct approaches, one experimental the other theoretical. The dianion was produced in the gas phase by sputtering a ${\mathrm{Li}}_2{\mathrm{SiF}}_6$ specimen with ${\mathrm{Cs}}^{+}$ ions and was detected by means of accelerator mass spectrometry. The identification was via the ${}^{29}\mathrm{Si}{}^{19}\mathrm{F}_6^{2-}$ isotopomer; it has an odd total mass and therefore the dianion shows up at a half-integral mass-to-charge ratio $(M∕q=71.5\mathrm{amu})$ in the mass spectrum, facilitating a positive identification. The flight time through the mass spectrometer of $\approx 10\mathrm{\mu }\mathrm{s}$ establishes a lower limit with respect to the intrinsic lifetime of this species. Attempts to detect the ${{\mathrm{SiF}}_6}^{2-}$ dianion also by secondary-ion mass spectrometry failed, but provided an upper limit in terms of its formation probability with respect to the ${\mathrm{F}}^{-}$ ion of ${}^{29}\mathrm{Si}{}^{19}\mathrm{F}_6^{2-}∕{}^{19}\mathrm{F}^{-}<2\times {10}^{-9}$. Furthermore, theoretical calculations of the photoelectron spectrum by means of the relativistic one-particle propagator predict considerable stability of the dianion against autodetachment. The first ionization potential of ${{\mathrm{SiF}}_6}^{2-}$ was determined as $2.79\mathrm{eV}$ at the optimized bond length of $1.718\mathrm{\AA }$ in the gas phase.

We show how two-photon correlation of a two-level amplifier in the small signal regime depends on the atomic populations and the propagation length. We predict that inverted population associated with negative temperature gives a very long correlation time even in the presence of decoherence, a useful asset for quantum communication. The correlation vanishes for very dilute atomic gas. Analytical solutions for the field operators obtained by Fourier transform and Laplace transform (with initial condition) of the time variable appear very different but yield identical numerical results except for certain parameters. The physical explanation behind the deviation is given. The presence of thermal photons is found to reduce the correlation time.

The dynamics of the Jaynes-Cummings Hamiltonian is studied in the semiclassical limit by reducing it to quantum normal form and deriving the phase-space dynamics of classically smooth observables. The resulting systematic semiclassical approximation is used to analyze the Rabi oscillations of a photon wave packet revealing subtle consequences of the uncertainty principle.

We investigate the multiple use of a ferromagnetic spin chain for quantum and classical communications without resetting. We find that the memory of the state transmitted during the first use makes the spin chain a qualitatively different quantum channel during the second transmission, for which we find the relevant Kraus operators. We propose a parameter to quantify the amount of memory in the channel and find that it influences the quality of the channel, as reflected through fidelity and entanglement transmissible during the second use. For certain evolution times, the memory allows the channel to exceed the memoryless classical capacity (achieved by separable inputs) and in some cases it can also enhance the quantum capacity.

We propose a scheme for the realization of a hybrid, strongly quantum-correlated system formed of an atomic ensemble surrounded by a high-finesse optical cavity with a vibrating mirror. We show that the steady state of the system shows tripartite and bipartite continuous variable entanglement in experimentally accessible parameter regimes, which is robust against temperature.

Using cold bosonic atoms with two (hyperfine) ground states, we introduce a spin-boson mixture that allows one to implement the quantum Ising model in a tunable dissipative environment. The first specie lies in a deep optical lattice with tightly confining wells and forms a spin array; spin-up (spin-down) corresponds to occupation by one (no) atom at each site. The second specie forms a superfluid reservoir. Different species are coupled coherently via laser transitions and collisions. Whereas the laser coupling mimics a transverse field for the spins, the coupling to the reservoir sound modes induces a ferromagnetic (Ising) coupling as well as dissipation. This gives rise to an order-disorder quantum phase transition where the effect of dissipation can be studied in a controllable manner.