An ad hoc quantization scheme for the electromagnetic field in a weakly dispersive, transparent dielectric leads to the definition of canonical and kinetic forms for the momentum of the electromagnetic field in a dispersive medium. The canonical momentum is uniquely defined as the operator that generates spatial translations in a uniform medium, but the quantization scheme suggests two possible choices for the kinetic momentum operator, corresponding to the Abraham or the Minkowski momentum in classical electrodynamics. Another implication of this procedure is that a wave packet containing a single dressed photon travels at the group velocity through the medium. The physical significance of the canonical momentum has already been established by considerations of energy and momentum conservation in the atomic recoil due to spontaneous emission, the Cerenkov effect, the Doppler effect, and phase matching in nonlinear optical processes. In addition, the data of the Jones and Leslie radiation pressure experiment is consistent with the assignment of one $\hslash \mathbf{k}$ unit of canonical momentum to each dressed photon. By contrast, experiments in which the dielectric is rigidly accelerated by unbalanced electromagnetic forces require the use of the Abraham momentum.

The interaction of a bichromatic quantized field with three-level atoms in a $\Lambda$ configuration is analyzed. We calculate the correlation functions of the field emitted by the atoms when the driven field is in a coherent state. We consider the cases where the atoms are inside and outside a cavity.

Atomic squeezing is studied for the case of large systems of radiating atoms, when collective effects are well developed. All temporal stages are analyzed, starting with the quantum stage of spontaneous emission, passing through the coherent stage of superradiant emission, and going to the relaxation stage ending with stationary solutions. A method of governing the temporal behavior of the squeezing factor is suggested. The influence of a squeezed effective vacuum on the characteristics of collective emission is also investigated.

Laser beams exert torque on microparticles through very different physical mechanisms. In this paper, optical angular momentum transferred by laser light to a trapped absorbing superparamagnetic microsphere has been studied, distinguishing between different contributions. We have found the main contribution to the torque arising from the transfer of the spin angular momentum carried by absorbed laser light. Detailed polarization status contribution of the laser light to the momentum transfer has been then analyzed. A general method to separate and quantify contributions to the optical angular momentum transferred has been developed. We have thus quantified contributions due to radiation pressure, through an effect similar to the wind on a windmill, and contributions arising from magneto-optic effects.

Near the condition of electromagnetically induced transparency in a three-level system, the absorption experienced by the weak probe laser beam interacting with one transition is very sensitive to the frequency detuning of the strong-coupling laser beam coupled to another transition. When the frequency detuning of the coupling laser is modulated at different frequencies, the resulting change in probe absorption as a function of that modulation frequency can be described by a transfer function. The effects on the transfer function from various experimental parameters are calculated numerically. Experimental measurements are shown to be in good agreement with the predicted behavior.

We theoretically explore coherent information transfer between ultraslow light pulses and Bose-Einstein condensates (BEC’s) and find that storing light pulses in BEC’s allows the coherent condensate dynamics to process optical information. We consider BEC’s of alkali atoms with a $\Lambda$ energy level configuration. In this configuration, one laser (the coupling field) can cause a pulse of a second pulsed laser (the probe field) to propagate with little attenuation (electromagnetically induced transparency) at a very slow group velocity $(\sim 10\mathrm{m}∕\mathrm{s})$ and be spatially compressed to lengths smaller than the BEC. These pulses can be fully stopped and later revived by switching the coupling field off and on. Here we develop a formalism, applicable in both the weak- and strong-probe regimes, to analyze such experiments and establish several results: (1) We show that the switching can be performed on time scales much faster than the adiabatic time scale for electromagnetically induced transparancy even in the strong-probe regime. We also study the behavior of the system changes when this time scale is faster than the excited state lifetime. (2) Stopped light pulses write their phase and amplitude information onto spatially dependent atomic wave functions, resulting in coherent two-component BEC dynamics during long storage times. We investigate examples relevant to ${}^{87}\mathrm{Rb}$ experimental parameters and see a variety of novel dynamics occur, including interference fringes, gentle breathing excitations, and two-component solitons, depending on the relative scattering lengths of the atomic states used and the probe to coupling intensity ratio. We find that the dynamics when the levels $\mid F=1,M_F=-1⟩$ and $\mid F=2,M_F=+1⟩$ are used could be well suited to designing controlled processing of the information input on the probe. (3) Switching the coupling field on after the dynamics writes the evolved BEC wave functions density and phase features onto a revived probe pulse, which then propagates out. We establish equations linking the BEC wave function to the resulting output probe pulses in both the strong- and weak-probe regimes. We then identify sources of deviations from these equations due to absorption and distortion of the pulses. These deviations result in imperfect fidelity of the information transfer from the atoms to the light fields and we calculate this fidelity for Gaussian-shaped features in the BEC wave functions. In the weak-probe case, we find that the fidelity is affected both by absorption of very-small-length-scale features and absorption of features occupying regions near the condensate edge. We discuss how to optimize the fidelity using these considerations. In the strong-probe case, we find that when the oscillator strengths for the two transitions are equal the fidelity is not strongly sensitive to the probe strength, while when they are unequal the fidelity is worse for stronger probes. Applications to distant communication between BEC’s, squeezed light generation, and quantum information are anticipated.

We have used the AUTOSTRUCTURE code to carry out semirelativistic calculations for the dielectronic recombination of ${\mathrm{Pb}}^{79+}$ via the $2s_{1∕2}-2p_{1∕2}$ core excitation. We obtain excellent agreement between these semirelativistic results and measurements made at Gesellschaft für Schwerionenforschung, in particular, for the high angular momentum peak of the $2p_{1∕2}20l_j$ resonances. The factor of 3 underestimate in the result for this peak that was originally obtained by Mitnik et al., which has led some to conclude that only a fully relativistic approach can describe dielectronic recombination via high angular momenta in very heavy highly charged ions, are found to be in error.

Standard closed-orbit theory is applied to derive the photodetachment cross section of ${\mathrm{H}}^{-}$ in the presence of a static electric field. The result agrees with the one derived earlier using a quantum approach involving a momentum-space wave function and stationary-phase approximation. The advantage of the present derivation is the ability to separate the oscillation term and the smooth background term in the photodetachment cross section and to identify the two terms with different physical origins.

We present completely ab initio nonperturbative calculations of the integral and single differential cross sections for double photoionization of ${\mathrm{H}}_2$ for photon energies from $53.9\text{to}75.7\mathrm{eV}$. The method of exterior complex scaling, implemented with B-splines, is used to solve the Schrödinger equation for a correlated continuum wave function corresponding to a single photon having been absorbed by a correlated initial state. The results are in good agreement with experimental integral cross sections.

We examine weak measurements of arbitrary observables where the object is prepared in a mixed state and on which measurements with imperfect detectors are made. The weak value of an observable can be expressed as a conditional expectation value over an infinite class of different generalized Kirkwood quasiprobability distributions. “Strange” weak values for which the real part exceeds the eigenvalue spectrum of the observable can only be found if the Terletsky-Margenau-Hill distribution is negative or, equivalently, if the real part of the weak value of the density operator is negative. We find that a classical model of a weak measurement exists whenever the Terletsky-Margenau-Hill representation of the observable equals the classical representation of the observable and the Terletsky-Margenau-Hill distribution is non-negative. Strange weak values alone are not sufficient to obtain a contradiction with classical models. We propose feasible weak measurements of photon number of the radiation field. Negative weak values of energy contradict all classical stochastic models, whereas negative weak values of photon number contradict all classical stochastic models where the energy is bounded from below by the zero-point energy. We examine coherent states in particular and find negative weak values with probabilities of 16% for kinetic energy (or squared field quadrature), 8% for harmonic oscillator energy, and 50% for photon number. These experiments are robust against detector inefficiency and thermal noise.

A classical and a fully quantum mechanical treatment is presented for the Čerenkov radiation stimulated by a uniformly moving charge particle. The dissipated energy of the electron is decomposed into two parts: the radiative energy density which is associated with the transverse part of the field operators and the nonradiative energy density which is connected with the longitudinal part of the field operators. Special attention is paid to the different limits of this formalism, and the results are compared with previous works. We also look at the Čerenkov radiation in left-handed materials.

Within the frame of macroscopic QED in linear, causal media, we study the radiation force of Casimir-Polder type acting on an atom which is positioned near dispersing and absorbing magnetodielectric bodies and initially prepared in an arbitrary electronic state. It is shown that minimal and multipolar coupling lead to essentially the same lowest-order perturbative result for the force acting on an atom in an energy eigenstate. To go beyond perturbation theory, the calculations are based on the exact center-of-mass equation of motion. For a nondriven atom in the weak-coupling regime, the force as a function of time is a superposition of force components that are related to the electronic density matrix elements at a chosen time. Even the force component associated with the ground state is not derivable from a potential in the ususal way, because of the position dependence of the atomic polarizability. Further, when the atom is initially prepared in a coherent superposition of energy eigenstates, then temporally oscillating force components are observed, which are due to the interaction of the atom with both electric and magnetic fields.

We study the problem of optimization over positive-operator-valued measures to extract classical correlation in a bipartite quantum system. The proposed method is applied to binary states only. Moreover, to illustrate this method, an explicit example is studied in detail.

The impossibility of cloning and deleting of unknown states constitute important restrictions on processing of information in the quantum world. On the other hand, a known quantum state can always be cloned or deleted. However, if we restrict the class of allowed operations, there will arise restrictions on the ability of cloning and deleting machines. We have shown that cloning and deleting of known states is in general not possible by local operations. This impossibility hints at quantum correlation in the state. We propose dual measures of quantum correlation based on the dual restrictions of no local cloning and no local deleting. The measures are relative entropy distances of the desired states in a (generally impossible) perfect local cloning or local deleting process from the best approximate state that is actually obtained by imperfect local cloning or deleting machines. Just like the dual measures of entanglement cost and distillable entanglement, the proposed measures are based on important processes in quantum information. We discuss their properties. For the case of pure states, estimations of these two measures are also provided. Interestingly, the entanglement of cloning for a maximally entangled state of two two-level systems is not unity.

We propose an implementation of quantum logic gates via internal state dependent displacements of ions in a linear Paul trap caused by optical dipole forces. Based on a general quantum analysis of the system dynamics we consider specific implementations with alkaline-earth-metal ions. For experimentally realistic parameters gate infidelities as low as ${10}^{-4}$ can be obtained.

Dissociative electron attachment (DEA) to vibronically excited $\mathrm{S}{\mathrm{O}}_2$ in the Clements’ band in the $288\text{to}298\mathrm{nm}$ region has been studied. The ${\mathrm{O}}^{-}$ ion yield, to a first approximation, follows the photo absorption spectrum in this range indicating the DEA process to be independent of the vibrational levels in this band. This is in contrast to what is generally observed for vibrational level dependence from the electronic ground state. The current measurements also do not show any qualitative change in the dissociative attachment process due to change of symmetry as one moves from the peaks to the valleys of the Clements band.

We have studied the multiphoton ionization of xenon atoms by $160\mathrm{fs}$ pulses at intensities of $5\times {10}^{12}$ and $1.3\times {10}^{13}\mathrm{W}∕{\mathrm{cm}}^2$ and present photoelectron kinetic energy and angular distribution spectra measured with a photoelectron imaging spectrometer. A noncollinear optical parametric amplifier allows us to tune the wavelength of the laser pulse over a range between 500 and $700\mathrm{nm}$. Resonant and nonresonant processes as well as channel switching effects have been observed in this intensity and wavelength regime. Mainly resonant $(5+1)$-photon ionization via $ns$, $nd$, and $n{d}^{\prime }$ Rydberg states was studied in the region of $505–602\mathrm{nm}$. Resonance structures were found related to the two fine structure ionization channels ${\mathrm{Xe}}^{+}{}^{2}P_{3∕2}$ and ${\mathrm{Xe}}^{+}{}^{2}P_{1∕2}$. In addition the $(6+1)$-photon resonant ionization and nonresonant 5- and 6-photon processes could be studied.

We analyze the dynamics of a molecular field incoherently pumped by the photoassociation of fermionic atoms and coupled by quantum tunneling in a double-well potential. The relative phase distribution of the molecular modes in each well and their phase coherence are shown to build up owing to quantum-mechanical fluctuations starting from the vacuum state. We identify three qualitatively different steady-state phase distributions, depending on the ratio of the molecule-molecule interaction strength to interwell tunneling, and examine the crossover from a phase-coherent regime to a phase-incoherent regime as this ratio increases.

The dynamics of a collection of resonant atoms embedded inside an inhomogeneous nondispersive and lossless dielectric is described with a dipole Hamiltonian that is based on a canonical quantization theory. The dielectric is described macroscopically by a position-dependent dielectric function and the atoms as microscopic harmonic oscillators. We identify and discuss the role of several types of Green tensors that describe the spatio-temporal propagation of field operators. After integrating out the atomic degrees of freedom, a multiple-scattering formalism emerges in which an exact Lippmann-Schwinger equation for the electric field operator plays a central role. The equation describes atoms as point sources and point scatterers for light. First, single-atom properties are calculated such as position-dependent spontaneous-emission rates as well as differential cross sections for elastic scattering and for resonance fluorescence. Secondly, multiatom processes are studied. It is shown that the medium modifies both the resonant and the static parts of the dipole-dipole interactions. These interatomic interactions may cause the atoms to scatter and emit light cooperatively. Unlike in free space, differences in position-dependent emission rates and radiative line shifts influence cooperative decay in the dielectric. As a generic example, it is shown that near a partially reflecting plane there is a sharp transition from two-atom superradiance to single-atom emission as the atomic positions are varied.

For further interferometric application on diffusive target, the phase fluctuation of a solid-state laser submitted to frequency shifted optical feedback is analyzed both theoretically and experimentally. As a drawback of the laser high sensitivity to optical feedback, the phase fluctuations induced by a strong phase-amplitude coupling noise are several orders of magnitude higher than the standard interferometric phase noise induced by the laser frequency width (Schawlow-Townes limit). Nevertheless, by sending a few milliwatts output power microchip laser beam on a diffusive target with an effective reflectivity of ${10}^{-9}$, a target displacement precision of $0.1\mathrm{\AA }∕\sqrt{\mathrm{Hz}}$ has been experimentally determined.