The electron-correlation effects largely determine the structure and dynamics of anions. Theoretical calculations in the literature indicate the influence of electron correlations on the absolute photodetachment cross section for ${\text{Cu}}^{-}$, for photon energies above 3.5 eV, but has not been confirmed experimentally. In the present work we probe the influence of channel coupling on the photoelectron angular distributions for photon energies above 3.5 eV. A velocity map imaging spectrometer was tested and employed in this experiment. The experimental results for the asymmetry parameter show no deviation from the single-electron model. The results indicate no significant influence of the channel-coupling effect on the photoelectron angular distribution in the photon energy range of 3.46–4.6 eV.

In an electric field of 0–6.67 kV/cm, nitric oxide (NO) molecules are excited by the double-resonance technique through the intermediate $A{}^2{\Sigma }^{+}{\text{F}}_1\left(v=0,N=0\right)$ level to the high Rydberg electronic states converging to the ionic ${\text{NO}}^{+}X{}^1{\Sigma }^{+}\left(v^{+}=0,N^{+}=0\right)$ level, in the energy region from the classical field-ionization limit $E_C^{\left(0,0\right)}$ to above the zero-field-ionization limit $E_0^{\left(0,0\right)}$. Just below $E_0^{\left(0,0\right)}$, resonances showing Fano profiles through the field-induced autoionization are observed. Above $E_0^{\left(0,0\right)}$, resonances corresponding to the transient states of electrons trapped on the “uphill” side of the potential energy raised by the field are observed. These field-induced resonances of molecules from the negative energy region just below the zero-field-ionization limit $E_0^{\left(0,0\right)}$ to the positive energy region are assigned completely. Decoupling of the orbital angular momentum of the Rydberg electron from the core rotation is confirmed in a high electric field.

We calculate the Bose-Einstein condensation (BEC) temperature of spin-1 atomic bosons in external magnetic field, taking into account the influence of the quadratic Zeeman effect. In case that the quadratic Zeeman coefficient is positive, the BEC temperature exhibits a nontrivial dependence on the magnetic field and a magnetic-field-induced reentrant phenomenon of BEC is observed. This phenomenon could be well understood by the competition between the linear and quadratic Zeeman effects. Reentrance of BEC in a trapped spinor Bose gas is also discussed.

We consider the problem of a single particle interacting with $N$ identical fermions, at zero temperature and in one dimension. We calculate the binding energy as well as the effective mass of the single particle. We use an approximate method developed in the three-dimensional case, where the Hilbert space for the excited states of the $N$ fermions is restricted to have at most two particle-hole pairs. When the mass of the single particle is equal to the fermion mass, we find excellent agreement with the exact results of McGuire. When the mass of the single particle is infinite, we solve exactly the problem and find again excellent agreement between approximate results and exact ones. This overall agreement in one dimension gives a strong validation for the approximate method applied in three dimensions. Moreover it shows that our approximate treatment is excellent for the one-dimensional problem in the general case with respect to the mass of the single particle.

We construct quantum field theory in an analog curved spacetime in Bose-Einstein condensates based on the Bogoliubov–de Gennes equations by exactly relating quantum particles in curved spacetime with Bogoliubov quasiparticle excitations in Bose-Einstein condensates. Here, we derive a simple formula relating the two, which can be used to calculate the particle creation spectrum by solving the time-dependent Bogoliubov–de Gennes equations. Using our formulation, we numerically investigate particle creation in an analog expanding universe which can be expressed as Bogoliubov quasiparticles in an expanding Bose-Einstein condensate. We obtain its spectrum, which follows the thermal Maxwell-Boltzmann distribution, the temperature of which is experimentally attainable. Our derivation of the analogy is useful for general Bose-Einstein condensates and not limited to homogeneous ones, and our simulation is an example of particle creations by solving the Bogoliubov–de Gennes equation in an inhomogeneous condensate.

We study intracavity electromagnetically induced transparency in atoms around a nanofiber with a pair of Bragg grating mirrors. We calculate the transmission of the composite cavity-fiber-atom system and the time development of the guided probe light field. We derive analytical approximate expressions for the output probe field and its group delay. We show that the group delay of the guided light substantially depends on the input pulse length, the mirror reflectivity, the atomic number density, and the coupling field intensity. We demonstrate that the group delay of the guided light can be significantly enhanced by the presence of the fiber-Bragg-grating cavity even when the finesse of the cavity is moderate.

We study subwavelength position measurement via spontaneous emission spectroscopy with two photons. Our model systems are a single $\Lambda$-type three-level atom, in which a dual interaction generates two independent photons, and an $M$-type five-level atom, which emits two photons in a double-Raman process. The difference is that the $M$-type system emits correlated pairs of photons, while the photon pairs from the $\Lambda$ system are uncorrelated. In order to evaluate the performance of the position measurement, we introduce an analysis scheme motivated by a possible experimental measurement procedure. We find characteristic differences in the spontaneous emission spectra of the two systems arising from the photon correlation in the $M$-type system. But interestingly, the effect of this photon pair correlation on the conditional position probability distribution does not lead to an increase in the position information of the single atom. Nevertheless, both schemes allow for an efficient measurement of the particle position with unambiguous position determination over a wide range of parameters.

Recently a test of nonclassicality for a single qubit was proposed [R. Alicki and N. Van Ryn, J. Phys, A: Math. Theor. 41, 062001 (2008)]. We present an optimized experimental realization of this test leading to a 46 standard deviation violation of classicality. This factor-of-5 improvement over our previous result was achieved by moving from the infrared to the visible where we can take advantage of higher-efficiency and lower-noise photon detectors.

We examine the possibility of coherent reversible information transfer between solid-state superconducting qubits and ensembles of ultracold atoms. Strong coupling between these systems is mediated by a microwave transmission line resonator that interacts near resonantly with the atoms via their optically excited Rydberg states. The solid-state qubits can then be used to implement rapid quantum logic gates, while collective metastable states of the atoms can be employed for long-term storage and optical readout of quantum information.

We experimentally and theoretically study nonlinear light propagation in a rotating waveguide array. We show that noninertial effects can lead to mode conversion, enhanced transport, and vector (gap) soliton formation. Experimentally, we directly observe these dynamics, both within and between bands, by recording intensity in position space and power spectra in momentum space. The results are fundamental to all rotating nonlinear lattices and hold potential for a variety of twisted photonic devices.

We present a treatment of the nonlinear matter-wave propagation inspired by optical methods, which includes interaction effects within the atom-optics equivalent of the aberrationless approximation. The atom-optical $ABCD$-matrix formalism, considered so far for noninteracting clouds, is extended perturbatively beyond the linear regime of propagation. This approach, applied to discuss the stability of a matter-wave resonator involving a free-falling sample, agrees very well with the predictions of the full nonlinear paraxial wave equation. An alternative optical treatment of interaction effects, based on the aberrationless approximation and suitable for cylindrical paraxial beams of uniform linear density, is also adapted for matter waves.

Spontaneous decay of a two-level atom near the left-handed material (LHM) slab is investigated. The contributions of the guided modes and the surface-plasmon polariton (SPP) modes supported by the LHM slab to the spontaneous decay are studied at length. We find that the atomic decay near a LHM slab is much different from that near a dielectric slab or metal slab. The first—the dielectric slab with arbitrary thickness—supports at least two guided modes (one for TE polarized and one for TM polarized), but LHM slab may support none of the guided mode for certain thickness. The second—the atom near the LHM slab—may decay through both TE- and TM-polarized SPP, but the atom near the metal slab can decay only through TM-polarized SPP. The third, when the LHM slab supports only TE-polarized SPP modes, the atom near such slab cannot couple to the SPP mode when its dipole moment is perpendicular to the interface. Even if LHM contains weak loss, above analysis is also valid, and the decay rate directly related to material’s losses (defined by the decay through dissipation here) can be distinguished from the total decay rate. Most interesting, we find that the decay through SPP will be larger than the decay through dissipation when the atom is placed at an appropriate position. Our results will give constructive reference to the design and fabrication of the quantum device made of LHM.

A two-component fermion model with conventional two-body interactions was recently shown to have anyonic excitations. We here propose a scheme to physically implement this model by transforming each chain of two two-component fermions to the two capacitively coupled chains of superconducting devices. In particular, we elaborate how to achieve the wanted operations to create and manipulate the topological quantum states, providing an experimentally feasible scenario to access the topological memory and to build the anyonic interferometry.

Laser cooling and trapping of the heavy alkaline-earth-metal element barium has been achieved based on the strong $6s^2{{}^{1}S}_0\text{−}6s6p{{}^{1}P}_1$ transition. The excited state decays to a large fraction into metastable $D$ states. Two schemes were implemented where three additional laser-driven transitions provide closed cooling cycles. This results in a fraction of 50(20)% of the trapped atoms in one of the metastable states. A total efficiency of $0.4\left(1\right)\times {10}^{-2}$ for slowing a thermal atomic beam and capturing atoms into a magneto-optical trap was obtained. Trap lifetimes of more than 1.5 s were observed. They are shortened at high laser intensities by three photon photoionization losses. The developed scheme can be transferred to other systems with large leakage from the cooling transition, such as Ra which is interesting for sensitive fundamental symmetry research.

A useful method for deriving analytical results applicable to the standard two-party deterministic dense-coding protocol is introduced and illustrated. In this protocol, communication of $K$ perfectly distinguishable messages is attainable via $K$ selected local unitary operations performed on one qudit from a pair of entangled qudits of equal dimension $d$ in a pure state $|\psi ⟩$ with largest Schmidt coefficient $\sqrt{{\lambda }_0}$. The method takes advantage of the fact that the $K$ message states, together with $d^2-K$ augmenting orthonormal state vectors, yield a unitary matrix, thereby implying properties of the $K$ message states which otherwise are not readily recognized. Employing this augmented message matrix, we produce simple proofs of previously established results including (i) ${\lambda }_0\le d/K$, (ii) ${\lambda }_0<d/K$ when $K=d+1$, and (iii) the impossibility of finding a $|\psi ⟩$ that can enable transmission of $K=d^2-1$ messages but not $d^2$. Additional results obtained using the method include proofs that the ${\lambda }_0\le d/K$ bound is reduced to at least (i) ${\lambda }_0\le \left(1/2\right)\left[1+\sqrt{\left(d-2\right)/\left(d+2\right)}\right]$ when $K=d+1$ and (ii) ${\lambda }_0\le \left(K-m\right)/\left(2K-m-d\right)$ whenever $\left(d+1\right)\le K\le 2d$ and the selected local unitaries include the first $m$ non-negative integral powers of the shift operator $X$.

We establish theoretical bounds on qubit detuning for some of the previously proposed controlled-NOT (CNOT) logic gate implementations with weakly coupled Josephson phase qubits. It is found that in the two-step, $\sqrt{i\text{SWAP}}$-based case the value of the detuning during the entangling operations must not exceed $2g$, where $g$ is the characteristic coupling constant. In the single-step case we consider two practical, physically distinct implementations, in which one of the qubits is driven by a concurrent rf pulse of fixed frequency. We find that when the local drive is applied to the “reference” qubit (with which it is in resonance), the detuning should not exceed $g$. If the drive is applied to the “detuned” qubit, generation of the perfect CNOT gate is possible at any value of detuning provided that the amplitude of the pulse can be made arbitrarily large.

We study the entanglement content of a class of mesoscopic tunable magnetic systems. The systems are closed finite spin-1/2 chains with ferromagnetic nearest-neighbor interactions frustrated by antiferromagnetic next-nearest-neighbor interactions. The finite chains display a series of level crossings reflecting the incommensurate physics of the corresponding infinite-size chain. We present dramatic entanglement signatures characterizing these unusual level crossings. We focus on multispin and global measures of entanglement rather than only one-spin or two-spin entanglements. We compare and contrast the information obtained from these measures to that obtained from traditional condensed-matter quantities such as correlation functions.

Especially in atomic systems, it is now well established that exchange energy generally dominates correlation effects. Therefore we focus here on the exchange energy density ${\epsilon }_x\left(r\right)$ as given in terms of the idempotent Dirac density matrix. This is then brought into contact with the one-parameter form of Becke’s functional, which corrects the local-density-approximation form $-c_x{\left[n\left(r\right)\right]}^{4/3}$ with $n\left(r\right)$ as the ground-state electron density, $c_x=\left(3/4\right)e^2{\left(3/\pi \right)}^{1/3}$, by terms involving the dimensionless gradient ratio $\left|\nabla n\left(r\right)\right|/n^{4/3}\left(r\right)$. A particular nonrelativistic model of the 10-electron Ne-like atomic ions, with large atomic number $Z$, is then compared to Becke’s approximation to ${\epsilon }_x\left(r\right)$.

The results from classical three-dimensional simulations of the double ionization of helium in an intense laser field are presented for realistic nonparaxial focal conditions. The existence of an out-of-phase electric field component in the laser propagation direction produces an effective longitudinal ellipticity, resulting in a reduction in the double-ion yields as a function of position in the laser focus. It is found that under conditions of tight focusing, the effective focal volume for nonsequential double ionization is significantly reduced.

We develop a theoretical framework to understand the preparation and relaxation of a metastable Mott insulator state within the first-excited band of a one-dimensional (1D) optical lattice. The state is loaded by “lifting” atoms from the ground to the first-excited band by means of a stimulated Raman transition. We determine the effect of pulse duration on the accuracy of the state preparation for the case of a Gaussian pulse shape. Relaxation of the prepared state occurs in two major stages: double-occupied sites occurring due to quantum fluctuations initially lead to interband transitions followed by a spreading of particles in the trap and thermalization. We find the characteristic relaxation times at the earliest stage and at asymptotically long times approaching equilibrium. Our theory is applicable to recent experiments performed with 1D optical lattices [T. Müller et al., Phys. Rev. Lett. 99, 200405 (2007)].