We propose a method for controllable generation of nonlocal entangled pairs using spinor atoms loaded in an optical superlattice. Our scheme iteratively increases the distance between entangled atoms by controlling the coupling between the double wells. When implemented in a finite linear chain of $2N$ atoms, it creates a triplet valence bond state with large persistency of entanglement (of the order of $N$). We also study the nonequilibrium dynamics of the one-dimensional ferromagnetic Heisenberg Hamiltonian and show that the time evolution of a state of decoupled triplets on each double well leads to the formation of a highly entangled state where short-distance antiferromagnetic correlations coexist with longer-distance ferromagnetic ones. We present methods for detection and characterization of the various dynamically generated states. These ideas are a step forward toward the use of atoms trapped by light as quantum-information processors and quantum simulators.

By combining the Minkowski inequality and the quantum Chernoff bound, we derive easy-to-compute upper bounds for the error probability affecting the optimal discrimination of Gaussian states. In particular, these bounds are useful when the Gaussian states are unitarily inequivalent, i.e., they differ in their symplectic invariants.

Classical methods are employed to characterize the energy-loss straggling for swift, heavy ions interacting with independent electrons of a degenerate electron gas. The method of Bohr on the statistical aspects of the energy-loss process is used, and the electron-intruder collision is modeled via a finite-range screened Coulomb potential energy. The transport fluctuation cross section is calculated analytically within the framework of the impact-parameter method. Comparison with straggling data obtained for carbon foils with singly ionized carbon ions is made, and a good agreement is found in the validity range of the applied classical methods.

We propose and present a quantitative analysis of neutral atom microtraps based on optical near fields produced by the diffraction of a laser wave on small apertures in a thin screen. We show that near-field atom microtraps are capable of storing atoms in micron-sized regions, with estimated trap lifetimes of about $1\mathrm{s}$, when using a moderate laser intensity of about $10\mathrm{W}∕{\mathrm{cm}}^2$. The depth of the proposed Fresnel atom microtraps is about $0.1\mathrm{mK}$. An array of such atom microtraps could have applications to site-selective manipulation of cold atoms.

The cross section $\sigma$, angular-distribution parameter $\beta$, and spin-polarization parameters $\{\xi ,\eta ,\zeta \}$ of photoelectrons for neutral beryllium are calculated in the multiconfiguration relativistic random-phase approximation theory. Precise energies and widths of all five Rydberg series of doubly excited states $\left(2pns\right){}^{1}P_1^{\mathrm{o}}$, $\left(2pns\right){}^{3}P_1^{\mathrm{o}}$, $\left(2pnd\right){}^{1}P_1^{\mathrm{o}}$, $\left(2pnd\right){}^{3}P_1^{\mathrm{o}}$, and $\left(2pnd\right){}^{3}D_1^{\mathrm{o}}$ are given. Experimental studies of the angular distribution and spin polarization of photoelectrons are suggested to obtain information on energies and widths of states, which cannot be obtained from total cross-section measurements.

We develop a diagrammatic perturbation treatment to calculate the zero-temperature equation of state of the dilute gas mixture of a single spin component Bose-Einstein condensate (BEC) and a normal Fermi gas of indistinguishable (single spin) fermion particles. We find that the mean-field description breaks down near the mechanical instability related to the phase separation phenomenon. Our analysis shows that the instability is caused by the competition of the usual short-range and fermion-mediated boson-boson interactions, which result in a boson compressibility that diverges. In the low BEC-density limit, we show that the diagrammatic analysis simplifies, we sum part of the higher-order diagrams, and we discuss the effects of other higher-order contributions.

We study the sudden expansion of strongly correlated fermions in a one-dimensional lattice, utilizing the time-dependent density-matrix renormalization group method. Our focus is on the behavior of experimental observables such as the density, the momentum distribution function, and the density and spin structure factors. As our main result, we show that correlations in the transient regime can be accurately described by equilibrium reference systems. In addition, we find that the expansion from a Mott insulator produces distinctive peaks in the momentum distribution function at $k\approx \pm \pi /2$, accompanied by the onset of power-law correlations.

We theoretically study a cavity filled with atoms, which provides the optical-mechanical interaction between the modified cavity photonic field and a oscillating mirror at one end. We show that the cavity field “dresses” these atoms, producing two types of polaritons, effectively enhancing the radiation pressure of the cavity field upon the oscillating mirror, as well as establishing an additional squeezing mode of the oscillating mirror. This squeezing produces an adiabatic entanglement, which is absent in usual vacuum cavities, between the oscillating mirror and the rest of the system. We analyze the entanglement and quantify it using the Loschmidt echo and fidelity.

We studied the thermodynamics of quantum light amplification in Phys. Rev. A 74, 063822 (2006). In this work we extend our analysis to include quantum light attenuation, as well as saturated amplification. We show that, for a given excitation of the two reservoirs, different field states converge to the same final stationary state. We provide a full analytic solution of the $3\otimes n$ matter-light density matrix at steady state. The final steady state has three remarkable properties: (i) it is in fact an equilibrium state, (ii) it is an independent (single tensor product) matter-field state (as seen by the vanishing thermodynamic fluxes), and (iii) the final field state assumes a bithermal distribution (as seen by a wide Gaussian $Q$ function centered around the origin). By partially tracing over the field, we obtain the Scovil–Schulz-DuBois atomic inversion formula [Phys. Rev. Lett. 2, 262 (1959)] analytically. We compare the quantum model with its semiclassical analog. Unlike the amplification scenario discussed in Phys. Rev. A 74, 063822 (2006), the quantum and the semiclassical models differ dramatically under the conditions discussed in this paper.

We study atom-atom correlations and relative number squeezing in the dissociation of a Bose-Einstein condensate (BEC) of molecular dimers made of either bosonic or fermionic atom pairs. Our treatment addresses the role of the spatial inhomogeneity of the molecular BEC on the strength of correlations in the short time limit. We obtain explicit analytic results for the density-density correlation functions in momentum space, and show that the correlation widths and the degree of relative number squeezing are determined merely by the shape of the molecular condensate.

It is a well known fact that the presence of material bodies in the vicinity of an atom affects its interaction with the always present quantized electromagnetic field. In this paper, we focus on how the spontaneous-emission rate of a given excited atom is altered when this atom is placed inside a perfectly conducting wedge. We begin by briefly presenting the formalism upon which our calculations are founded, proceeding then to a long but straightforward calculation of the transition rate. We present results for a general atom, but, for the sake of simplicity, we narrow them down to an effective two-level system in our numerical investigations. The oscillatory pattern for the spontaneous-emission rate of the atom as we vary its relative position to the wedge as well as the phenomenon of suppression are shown by a few graphs.

The quantum states built with the $\mathrm{\eta }$ pairing mechanism, i.e., $\mathrm{\eta }$ pairing states, were first introduced in the context of high-temperature superconductivity where they were recognized as important example of states allowing for off-diagonal long-range order (ODLRO). In this paper we describe the structure of the correlations present in these states when considered in their momentum representation and we explore the relations between the quantum bipartite and multipartite correlations exhibited in $k$ space and the direct lattice superconducting correlations. In particular, we show how the negativity between paired momentum modes is directly related to the ODLRO. Moreover, we investigate the dependence of the block entanglement on the choice of the modes forming the block and on the ODLRO; consequently we determine the multipartite content of the entanglement through the evaluation of the generalized Meyer-Wallach measure in the direct and reciprocal lattice. The determination of the persistency of entanglement shows how the network of correlations depicted exhibits a self-similar structure which is robust with respect to “local” measurements. Finally, we recognize how a relation between the momentum-space quantum correlations and the ODLRO can be established even in the case of BCS states.

We show that the pure Aharonov-Bohm (AB) effect, or its dual (DAB), depends only on the net electric, or magnetic charge of an interfering object, however many internal degrees of freedom that system may have. The reciprocal Aharonov-Casher (AC) and He-McKellar-Wilkens (HMW) effects, on the other hand, involve physical properties—the magnetic and electric polarization of the system—which couple a system’s internal degrees of freedom to its center-of-mass coordinate through the field. For composite systems this illustrates a fundamental difference between the two types of phenomenon, and one which could be important as the number of internal degrees of freedom become large. We show that, for a single internal degree of freedom, the result of this coupling is a transient loss of coherence in the observed interference of the center-of-mass coordinate.

A deterministic excess-noise-free recording of unknown quantum states to continuous-variable quantum atomic memory is proposed. To reach this, the memory experiment is extended by the presqueezing of the recorded state of light and deterministic squeezing post-correction of the recorded state. To upload highly nonclassical resources to the memory, such as single-photon state or superposition of coherent states, a probabilistic method is suggested. With the help of presqueezing of the resource state of light and probabilistic squeezing post-correction, this probabilistic upload approaches a lossless transfer of these highly nonclassical states into the quantum memory. Without the squeezing post-correction, the highly nonclassical state can still be probabilistically uploaded in the limit of a weak light-atom coupling.

It is proven that in Levy’s constrained search or Lieb’s ensemble constrained search, if the minimum is achieved by wave functions that satisfy the steadiness condition for the current density kernel and have continuous second derivatives, the minimizing wave functions are eigenstates of some external potential. If the excited states of this potential can only achieve stationarity and cannot achieve a minimum in the constrained search, the minimizing wave functions are ground states and the corresponding electron density is $\mathit{v}$-representable or ensemble $\mathit{v}$-representable. This is also true for the ensemble system with a varying electron number. In time-dependent density-functional theory, if the stationarity of the action integral is achieved in the constrained search by a wave function that satisfies the continuity equation for the current density kernel and has a continuous first derivative with respect to the time coordinate and continuous second derivatives with respect to the space coordinates, the stationary wave function satisfies the time-dependent Schrödinger equation of some time-dependent external potential and the corresponding electron density is time-dependent $\mathit{v}$-representable.

The $P,T$-odd interaction constant, $W_S$, for the ground state of YbF and BaF molecules are calculated using the second-order many-body perturbation theory (MBPT) via $Z$-vector technique. The interaction constant $W_S$ reported here agrees favorably well with other correlated calculations. We also address the convergence behavior of $W_S$ with respect to the number of active orbitals used in the perturbative calculations.

We discuss the cooling efficiency of ultracold Fermi-Bose mixtures in species-selective traps using a thermodynamical approach. The dynamics of evaporative cooling trajectories is analyzed in the specific case of bichromatic optical dipole traps also taking into account the effect of partial spatial overlap between the Fermi gas and the thermal component of the Bose gas. We show that large trapping frequency ratios between the Fermi and the Bose species allow for the achievement of a deeper Fermi degeneracy, consolidating in a thermodynamic setting earlier arguments based on more restrictive assumptions. In particular, we confirm that the minimum temperature of the mixture is obtained at the crossover between boson and fermion heat capacities, and that below such a temperature sympathetic cooling vanishes. When the effect of partial overlap is taken into account, optimal sympathetic cooling of the Fermi species may be achieved by properly tuning the relative trapping strength of the two species in a time-dependent fashion. Alternatively, the dimensionality of the trap in the final stage of cooling can be changed by increasing the confinement strength, which also results in a crossover of the heat capacities at deeper Fermi degeneracies. This technique may be extended to Fermi-Bose degenerate mixtures in optical lattices.

We investigate the dynamics of converting cold bosonic atoms to molecules when an external magnetic field is swept across a Feshbach resonance. Our analysis relies on a quantum microscopic model that accounts for many-body effects in the association process. We show that the picture of two-body molecular production depicted by the Landau-Zener model is significantly altered due to many-body effects. In the nonadiabatic regime, we derive an analytic expression for molecular conversion efficiency that explains the discrepancy between the prediction of the Landau-Zener formula and the experimental data [E. Hodby et al., Phys. Rev. Lett. 94, 120402 (2005)]. Our theory is further extended to the formation of heteronuclear diatomic molecules and gives some interesting predictions.

We propose a many-qubit network with cavity QED by encoding qubits in decoherence-free subspace, based on which we can implement many-logic-qubit conditional gates by means of cavity-assisted interaction with single-photon pulses. Our scheme could not only resist collective dephasing errors, but also much reduce the implementational steps compared to conventional methods doing the same job, and we can also complete communications between two arbitrary nodes. We show the details by implementing a three-logic-qubit Toffoli gate and explore the experimental feasibility and challenge based on currently achievable cavity QED technologies.

We consider the photon spontaneous emission of single molecules in a solid matrix with spectral diffusion. A general theoretical strategy for calculating the photon emission statistics in a solid matrix of single molecules is derived. In particular, the control photon emission from single molecules in a solid matrix driven simultaneously by a laser and an electric radiofrequency (rf) field is investigated. The photon emission of single molecules can be modulated by an rf field. The formulation also allows for the study of the average waiting time for the emission event of a single molecule.