Physical Review A

The π -phase shift between |F=1,m_F=0⟩ and |F=2,m_F=0⟩ states for an adiabatic rotation of a magnetic field observed in Ramsey atom interferometry arises from the negative sign of the transition amplitude between the |1,0⟩ and |2,0⟩ states when the wave functions are rotated to the o...

The interaction energy due to electromagnetic field fluctuations between two infinitely long straight parallel dielectric-diamagnetic cylinders immersed in a medium is considered. We make use of the mode summation method for the calculations. We investigate the energy dependence on the cylindrical r...

We propose an experiment that would produce and measure a large Aharonov-Casher (AC) phase in a solid-state system under macroscopic motion. A diamond crystal is mounted on a spinning disk in the presence of a uniform electric field. Internal magnetic states of a single nitrogen-vacancy (N-V) defe...

Recently, the principle of information causality has appeared as a good candidate for an information-theoretic principle that would single out quantum correlations among more general nonsignaling models. Here, we present results going in this direction, namely, we show that part of the boundary of q...

The noncontextuality of quantum mechanics can be directly tested by measuring two entangled particles with more than two outcomes per particle. The two associated contexts are “interlinked” by common observables.

We introduce quantum spin models whose ground states allow for sizable entanglement between distant spins. We discuss how spin models with global end-to-end entanglement realize quantum teleportation channels with optimal compromise between scalability and resilience to thermal decoherence and can b...

A scheme for fault-tolerant quantum computation (FTQC) with probabilistic two-qubit gates is proposed. The error thresholds for FTQC are estimated by numerical simulations, where the conditional error probability (the error probability under the condition of “success”) is taken into account in a...

The two-loop self-energy correction to the ground-state Lamb shift is calculated for hydrogenlike ions with the nuclear charge Z=10–30 without any expansion in the binding field of the nucleus. A calculational technique is reported for treatment of Feynman diagrams in the mixed coordinate-moment...

We report the observation of trielectronic recombination with simultaneous excitation of a K -shell and an L -shell electron, hence involving three active electrons. This process was identified in the x-ray emission spectrum of recombining highly charged Kr ions. An energy resolution three times h...

We demonstrate and theoretically analyze the dressing of several proximate Feshbach resonances in ⁸⁷Rb using radio-frequency (rf) radiation. We present accurate measurements and characterizations of the resonances, and the dramatic changes in scattering properties that can arise through the rf dre...

We propose the use of interaction-free quantum measurements with electrons to eliminate sample damage in electron microscopy. This might allow noninvasive molecular-resolution imaging. We show the possibility of such measurements in the presence of experimentally measured quantum decoherence rates a...

Electron emission spectra obtained by thermal collisions of He^∗(2¹S and 2³S ) atoms with Au(111) and Pt(111) surfaces were measured to clarify the electronically excited atom-metal interactions. It has been recognized that the metastable atoms de-excite on ordinary noble- and transition-metal s...

We demonstrate experimentally the efficient fusion neutron generation from Coulomb explosion (CE) of laser irradiated large-size heteronuclear deuterated methane clusters. A conversion efficiency of 2.1×10⁶ neutrons/J of incident laser energy is obtained with a 120 mJ, 70 fs laser pulse. It is ...

We show the existence of a permanent molecular planar alignment in field-free conditions. We present different control strategies using shaped laser pulses to reach this state. The strategies are robust with respect to the temperature and can be implemented with the state of the art technology. They...

We analyzed the discrepancy of the angular dependence of strong-field ionization for CO₂ among the different theoretical calculations and experiments. Using a more accurate ground-state wave function of CO₂ in the asymptotic region, we showed that the accuracy in the earlier tunneling ionization...

We demonstrate selective vibrational population transfer in cold cesium dimers using a simple approach based on the use of a shaped incoherent broadband diode laser near threshold. Optical pumping into a single vibrational level is accomplished with an incoherent light source by eliminating transiti...

We propose a usage of microwave radiation in a magnetic trap for improving the cooling and trapping of cold antihydrogen atoms which are initially produced in high magnetic moment states. Inducing transitions toward lower magnetic moments near the turning points of the atom in the trap, followed by ...

We investigate harmonic generation from H₂⁺ molecules driven by intense few-cycle laser pulses whose linearly polarization axis makes an arbitrary angle χ with respect to the molecular axis. The H₂⁺ molecule is considered initially in various orbitals with nodal planes. It is found that a str...

We present a numerical study of quantum turbulence within the three-dimensional Gross-Pitaevskii equation, concentrating on the direct energy cascade in the case of a forced-dissipated system. We show that the behavior of the system is very sensitive to the properties of the model at the scales grea...

Ternary flavor mixtures of ultracold fermionic atoms in an optical lattice are studied in the case of equal repulsive on-site interactions Ugt;0 . The corresponding SU(3) invariant Hubbard model is solved numerically exactly within dynamical mean-field theory using multigrid Hirsch-Fye quantum Mon...

We propose methods to create fractional vortices in the cyclic state of an F=2 spinor Bose-Einstein condensate by manipulating its internal spin structure using pulsed microwave and laser fields. The stability of such vortices is studied as a function of the rotation frequency of the confining har...

We investigate the effect of the anisotropy between the s -wave scattering lengths of a three-component atomic Fermi gas loaded into a one-dimensional optical lattice. We find four different phases which support trionic instabilities made of bound states of three fermions. These phases distinguish ...

We have experimentally demonstrated a high level of control of the mode populations of guided-atom lasers (GALs) by showing that the entropies per particle of an optically GAL and the one of the trapped Bose-Einstein condensate (BEC) from which it has been produced are the same. The BEC is prepared ...

Correlations between particles can lead to subtle and sometimes counterintuitive phenomena. We analyze one such case, occurring during the sudden expansion of fermions in a lattice when the initial state has a strong admixture of double occupancies. We promote the notion of quantum distillation: dur...

We investigate the finite-temperature properties of attractive three-component (colors) fermionic atoms in optical lattices using a self-energy functional approach. As the strength of the attractive interaction increases in the low-temperature region, we observe a second-order transition from a Ferm...

We present an approach to explore and control nonlinear interactions between two orthogonally polarized femtosecond filaments launched parallel in air. The self-phase and cross-phase modulations due to the Kerr effect and cross-(de)focusing induced by the plasma and molecular alignment were distinct...

On the basis of macroscopic quantum electrodynamics, a theory of Casimir forces in the presence of linearly amplifying bodies is presented which provides a consistent framework for studying the effect of, e.g., amplifying left-handed metamaterials on dispersion forces. It is shown that the force can...

We demonstrate experimentally and theoretically random-phase surface solitons in effectively instantaneous nonlinear media. The key mechanism for self-trapping is played by a nonlocal nature of the nonlinearity, in contrast to other incoherent solitons involving time averaging. These incoherent surf...

We demonstrate a chaotic microcavity laser whose quality is comparable to typical nonchaotic microcavity lasers, yet it has the unique characteristic of unidirectional output. The cavity shape is a disk with the boundary defined by a curve called limaçon of Pascal. For a lasing mode of volume less ...

We experimentally demonstrate that thermal radiation from a micron-sized dielectric particle depends sensitively on its size and shape through the cavity quantum-electrodynamic effect. Our laser trapping technique levitated a high-temperature microsphere of Al₂O₃ and enabled emission spectroscopy ...

The π -phase shift between |F=1,m_F=0⟩ and |F=2,m_F=0⟩ states for an adiabatic rotation of a magnetic field observed in Ramsey atom interferometry arises from the negative sign of the transition amplitude between the |1,0⟩ and |2,0⟩ states when the wave functions are rotated to the o...

The dynamics of a system, consisting of a particle initially in a Gaussian state interacting with a field mode, under the action of repeated measurements performed on the particle, is examined. It is shown that regardless of its initial state the field is distilled into a squeezed state. The depende...

Using a simple model potential, we study the effects of weak Markovian dissipation on the quantum arrival time. The interaction with the environment is incorporated into the dynamics through a Markovian master equation of Lindblad type, which allows us to compare time-of-arrival distributions and ap...

We show the existence of a permanent molecular planar alignment in field-free conditions. We present different control strategies using shaped laser pulses to reach this state. The strategies are robust with respect to the temperature and can be implemented with the state of the art technology. They...

In an intense laser field, an electron may decay by emitting a pair of photons. The two photons emitted during the process, which can be interpreted as a laser-dressed double Compton scattering, remain entangled in a quantifiable way: namely, the so-called concurrence of the photon polarizations giv...

We have observed the photodetachment spectrum near the lowest detachment threshold from S⁻ in a 1 T field. The spectroscopy shows a small degree of magnetic field structure of the type observed in similar experiments at the higher-energy threshold of the electron affinity. Furthermore, our resul...

We investigate the creation mechanism of quantum accelerator modes which are attributed to the existence of the stability islands in an underlying pseudoclassical phase space of the quantum delta-kicked accelerator. Quantum accelerator modes can be created by exposing a Bose-Einstein condensate to a...

We study a natural construction of a general class of inhomogeneous quantum walks (namely, walks whose transition probabilities depend on position). Within the class we analyze walks that are periodic in position and show that, depending on the period, such walks can be bounded or unbounded in time;...

Perfect state transfer (PST) is discussed in the context of passive quantum networks with logical bus topology, where many logical nodes communicate using the same shared media without any external control. The conditions under which a number of point-to-point PST links may serve as building blocks ...

Every security analysis of quantum-key distribution (QKD) relies on a faithful modeling of the employed quantum states. Many photon sources, such as for instance a parametric down-conversion (PDC) source, require a multimode description but are usually only considered in a single-mode representation...

We discuss how to characterize entanglement sources with finite sets of measurements. The measurements do not have to be tomographically complete and may consist of POVMs rather than von Neumann measurements. Our method yields a probability that the source generates an entangled state as well as est...

Recent absorption measurements of the self-broadening of Rb principal series lines [C. H. Greene, E. L. Hamilton, H. Crowell, C. Vadla, and K. Niemax, Phys. Rev. Lett. 97, 233002 (2006)] verified the existence of minima in highly excited long-range potentials of Rb₂ which were predicted theoretica...

High-precision Hylleraas-configuration-interaction (Hy-CI) method variational calculations are reported for the 2 ²S ground state of neutral lithium. The nonrelativistic energy is calculated to be −7.478 060 323 451 9 hartree , demonstrating that the Hy-CI technique is capable of su...

We present a theory of vibrationally enhanced positron annihilation on molecules based on the Feshbach projection operator formalism. A key aspect of the present approach is the fact that no direct vibrational excitation is assumed, i.e., the attachment mechanism is electronic in nature, arising fro...

In this paper, we report on total electron tetrahydrofuran (C₄H₈O) scattering cross-section measurements for energies in the range from 50 to 5000 eV with experimental errors of about 5%. In addition, integral elastic and inelastic cross sections have been calculated over a broad energy range (1â...

We consider electron capture in fast collisions between a proton and hydrogen in the presence of an intense x-ray laser whose angular frequency ω is close to v²/2 , where v is the collision velocity. We show that in such a case laser-induced capture becomes possible and that the latter proceed...

We report on the extension of the recently formulated relativistic convergent close-coupling (RCCC) method to include the Breit and Møller interactions. The inclusion of these relativistic effects ensures that the RCCC method is now capable of calculating electron scattering excitation and ionizati...

Disorder modifies the sound-wave excitation spectrum of Bose-Einstein condensates. We consider the classical hydrodynamic limit, where the disorder correlation length is much longer than the condensate healing length. By perturbation theory, we compute the phonon lifetime and the correction to the s...

In this paper, the phase diagrams of a polar spin-1 Bose gas in a three-dimensional optical lattice with linear and quadratic Zeeman effects both at zero and finite temperatures are obtained within mean-field theory. The phase diagrams can be regrouped to two different parameter regimes depending on...

We derive a 1/c expansion for the single-particle density matrix of a strongly interacting time-dependent one-dimensional Bose gas, described by the Lieb-Liniger model ( c denotes the strength of the interaction). The formalism is derived by expanding Gaudin’s Fermi-Bose mapping operator up to ...

We calculate the reduced single-particle density matrix (RSPDM), momentum distribution, natural orbitals and their occupancies, for a strongly repulsive one-dimensional Bose-Fermi mixture in a double-well potential with a large central barrier. We assume that all particles have the same mass, and fe...

We consider ultracold matter of spin-two atoms in optical lattices. We derive an effective Hamiltonian for the studies of spin ordering in Mott states and investigate hyperfine spin correlations. Particularly, we diagonalize the Hamiltonian in an on-site Hilbert space taking into account spin-depend...

We show that interactions result in the emergence of a definite relative phase between two initially incoherent Bose-Einstein condensates. The many-realization interference fringe visibility is universal at g₁₂⁽¹⁾∼1/3 throughout the Josephson interaction regime as evident from a semiclassical pi...

We have measured the evolution of the intensity emitted by a random laser during a pump pulse that is comparable in duration to the spontaneous emission decay time. The time traces of our random laser, consisting of titanium dioxide particles and sulforhodamine B dye, show clear relaxation oscillati...

We introduce a fundamental concept - closed sets of correlations - for studying non-local correlations. We argue that sets of correlations corresponding to information-theoretic principles, or more generally to consistent physical theories, must be closed under a natural set of operations. Hence, studying the closure of sets of correlations gives insight into which information-theoretic principles are genuinely different, and which are ultimately equivalent. This concept also has implications for understanding why quantum non-locality is limited, and for finding constraints on physical theories beyond quantum mechanics.

Theoretical considerations of Bell-inequality experiments usually assume identically prepared and independent pairs of particles. Here we consider pairs that exhibit both intra- and inter-pair entanglement. The pairs are taken from a large many-body system where all the pairs are generally entangled with each other. Using an explicit example of single mode entanglement and ancillary BEC, we show that the Bell-inequality violation in such systems can display statistical properties that are remarkably different from those obtained using identically prepared, independent pairs. In particular, one can have probabilistic violation of Bell's inequalities in which a finite fraction of all the runs result in violation, even though there could be no violation when averaging over all the runs. Whether or not a particular run of results will end up being local realistically explainable is "decided" by a sequence of quantum (random) outcomes.

We determine the conditions for the existence of a pair of degenerate parity breaking separable eigenstates in general arrays of arbitrary spins connected through XYZ couplings of arbitrary range and placed in a transverse field, not necessarily uniform. Sufficient conditions under which they are ground states are also provided. It is then shown that in finite chains, the associated definite parity states, which represent the actual ground state in the immediate vicinity of separability, can exhibit entanglement between any two spins regardless of the coupling range or separation, with the reduced state of any two subsystems equivalent to that of pair of qubits in an entangled mixed state. The corresponding concurrences and negativities are exactly determined. The same properties persist in the mixture of both definite parity states. These effects become specially relevant in systems close to the XXZ limit. The possibility of field induced alternating separable solutions with controllable entanglement side limits is also discussed. Illustrative numerical results for the negativity between the first and the jth spin in an open spin s chain for different values of s and j are as well provided.

We investigate the connection between local minima in the problem Hamiltonian and first order quantum phase transitions during an adiabatic quantum computation. We demonstrate how some properties of the local minima can lead to an extremely small gap that is exponentially sensitive to the Hamiltonian parameters. Using perturbation expansion, we derive an analytical formula that can not only predict the behavior of the gap, but also provide insight on how to controllably vary the gap size by changing the parameters. We show agreement with numerical calculations for a weighted maximum independent set problem instance.

We determine the conditions under which topological order survives a rapid quantum quench. Specifically, we consider the case where a quantum spin system is prepared in the ground state of the Toric Code Model and, after the quench, it evolves with a Hamiltonian that does not support topological order. We provide analytical results supported by numerical evidence for a variety of quench Hamiltonians. The robustness of topological order under non-equilibrium situations is tested by studying the topological entropy and a novel dynamical measure, which makes use of the similarity between partial density matrices obtained from different topological sectors.

A high resolution (DeltaE~55 meV), trap-based positron beam has been used to measure absolute scattering cross sections for the excitation of the resolved 21S,P states of helium at energies between threshold and 38 eV. The experimental integral cross sections, which have typical uncertainties of 10% or less, are compared with several theoretical calculations, and the agreement is generally very favourable. In particular, a new convergent close coupling approach shows excellent agreement with the experimental data.

A new quantum mechanical approach to ion-molecule collisions is presented. It involves a separation of molecular geometry and collision dynamics and enables the use of the basis generator method developed for ion-atom collisions with relatively minor modifications. As a first application, we consider the pnbsp;-H2O collision system in the impact energy range of 20 to 5000 keV, and report total cross sections for net electron transfer and ionization. They are in remarkably good agreement with experimental data.

Accurate Hylleraas-type correlated helium wave functions are used to predict positronium (Ps) formation cross sections in positron-helium collisions within the frame work of the distorted-wave approximation at intermediate and high energies of positron impact. Exponential correlated atomic target wave functions taking into account up to N = 30 basis terms are utilized. Reliable total cross sections for the ground- and excited 2s-state Ps formation are reported at intermediate and high energies. The present distorted-wave results are in conformity with the existing theoretical and experimental values available in the literature for intermediate and high energy positrons. Surface plots of the DWA differential cross section reveal rich structures due to constructive and destructive interference between angular momentum states of the moving Ps. PACS Nos. 34.70.+e, 34.80.Uv, 34.80.Lx

We analyze the magnetic dipole contribution to atom-surface dispersion forces. Unlike its electrical counterpart, it involves small transition frequencies that are comparable to thermal energy scales. A significant temperature dependence is found near surfaces with a nonzero DC conductivity, leading to a strong suppression of the dispersion force at T > 0. We use thermal response theory for the surface material and discuss both normal metals and superconductors. The asymptotes of the free energy of interaction and of the entropy are calculated analytically over a large range of distances. Near a superconductor, the onset of dissipation at the phase transition strongly changes the interaction, including a discontinuous entropy. We discuss the similarities with the Casimir interaction beween two surfaces and suggest that precision measurements of the atom-surface interaction may shed new light upon open questions around the temperature dependence of dispersion forces between lossy media.

A new method for complete characterization of the waveform of individual few-cycle laser pulses is presented. By analyzing the "left" and "right" asymmetry of high-energy photoelectrons along the polarization axis using the recently developed quantitative rescattering theory, we show that the carrier-envelope phase (CEP), pulse duration and peak intensity of each single-shot pulse can be readily retrieved. By CEP-tagging each laser shot the method permits the study of waveform dependent processes be extended to relativistic beams and to wavelengths where CEP-stabilization is not yet possible.

Numerical solution of the time-dependent Schr#246;dinger equation for a two-dimension model of H2 ionization by intense ultrashort (few cycles) XUV laser pulses are presented to compare linear and circular polarization angular distributions for aligned molecules. Both ground (X1Sg+) and excited (A3Su+) states ionization is calculated at equilibrium and for extended large internuclear distance configurations to study the effect of electron delocalization via molecular orbitals vs electron localization in Heitler-London atomic wavefunctions. It is found that at large distance for ionized electron wavelengths less than the internuclear distance, circular polarization ionization angular distributions exhibit signature of the entanglement of electrons by exchange, thus allowing for a measure of exchange entanglement.

Motivated by the recent discovery that a reflecting wall moving with a square-root in time trajectory behaves as a universal stopper of classical particles regardless of their initial velocities, we compare linear in time and square-root in time expansions of a box to achieve efficient atom cooling. For the quantum single-atom wavefunctions studied the square-root in time expansion presents important advantages: asymptotically it leads to zero average energy whereas any linear in time (constant box-wall velocity) expansion leaves a non-zero residual energy, except in the limit of an infinitely slow expansion. For finite final times and box lengths we set a number of bounds and cooling principles which again confirm the superior performance of the square-root in time expansion, even more clearly for increasing excitation of the initial state. Breakdown of adiabaticity is generally fatal for cooling with the linear expansion but not so with the square-root in time expansion.

We study the role of an external photoassociation light field in the spin mixing dynamics of a spin-1 Bose condensate with long-range magnetic dipole-dipole interaction. The mean-field energy functional of the system is found to be formally identical to that of two coupled non-rigid pendulums, manifesting either constructive or destructive interferences. The interplay between photoassociation and the magnetic dipole-dipole interaction provides a novel route to the magneto-optical quantum control of atomic spin mixing in dipolar spinor condensates.

We study the stability of superfluid Fermi gases in deep optical lattices in the BCS-BEC crossover at zero temperature. Within the tight-binding attractive Hubbard model, we calculate the spectrum of the low-energy Anderson-Bogoliubov (AB) mode as well as the single-particle excitations in the presence of superfluid flow in order to determine the critical velocities. To obtain the spectrum of the AB mode, we calculate the density response function in the generalized random phase approximation (GRPA) applying the Green's function formalism developed by C#244;t#233; and Griffin to the Hubbard model. We find that the spectrum of the AB mode is separated from the particle-hole continuum having the characteristic roton-like minimum at short wavelength due to the strong charge-density-wave (CDW) fluctuations. The energy of the roton-like minimum decreases with increasing the lattice velocity and it reaches zero at the critical velocity which is smaller than the pair-breaking velocity. This indicates that the superfluid state is energetically unstable due to the spontaneous emission of the short wavelength roton-like excitations of the AB mode instead due to pair-breaking. We determine the critical velocities as functions of the interaction strength across the BCS-BEC crossover regime.

We describe the design and function of a circular magnetic waveguide produced from wires on a microchip for atom interferometry using deBroglie waves. The guide is a two-dimensional magnetic minimum for trapping weak-field seeking states of atoms or molecules with a magnetic dipole moment. The design consists of seven circular wires sharing a common radius. We describe the design, the time-dependent currents of the wires and show that it is possible to form a circular waveguide with adjustable height and gradient while minimizing perturbation resulting from leads or wire crossings. This maximal area geometry is suited for rotation sensing with atom interferometry via the Sagnac effect using either cold atoms, molecules and Bose-condensed systems.

We demonstrate a two-dimensional atom interferometer in a harmonic magnetic waveguide using a Bose-Einstein condensate. Such an interferometer could measure rotation using the Sagnac effect. Compared to free space interferometers, larger interactions times and enclosed areas can in principle be achieved, since the atoms are not in free fall. In this implementation, we induce the atoms to oscillate along one direction by displacing the trap center. We then split and recombine the atoms along an orthogonal direction, using an off-resonant optical standing wave. We enclose a maximum effective area of 0.1nbsp;mm2, limited by fluctuations in the initial velocity and the coherence time of the interferometer. We argue that this arrangement is scalable to enclose larger areas by increasing the coherence time and then making repeated loops.

Cold atoms in an optical lattice execute Bloch-Zener oscillations when they are accelerated.We have performed a theoretical investigation into the case when the optical lattice is the intra-cavity field of a driven Fabry-Perot resonator. When the atoms oscillate inside the resonator, we find that their back-action modulates the phase and intensity of the light transmitted through the cavity. We solve the coupled atom-light equations self-consistently and show that, remarkably, the Bloch period is unaffected by this back-action. The transmitted light provides a way to observe the oscillation continuously, allowing high precision measurements to be made with a small cloud of atoms.

We report on a new teleportation scheme, in which a controllable orbital angular momentum (OAM) generator is teleported. Via our scheme, Alice is able to, according to another independent photon's spin state (polarization) sent by Carol, electrically control the remote OAM generation on Bob's photon. To this end, we introduce a local electrically tunable and spin-dependent OAM generator to transfer a preliminary OAM-OAM entanglement to a spin-OAM Hybrid entanglement, which then makes a joint Bell-state measurement on Alice and Carol's photons play its role. We show that the quantum state tomography (QST) can be introduced to evaluate the performance of the teleportation.

In a recent Comment [Phys. Rev. A 79, 027801 (2009)], our position that the calculation of dispersion forces should be based preferably on the Lorentz force (or, equivalently, on Maxwell's stress tensor) is put into question, and it is argued that one should resort to Minkowski's stress tensor instead. After sketching briefly our reasons for preferring the Lorentz force, we point out that by use of Minkowski's stress tensor additional, compensatory force components are included in the calculation, but inconsistently. We dismiss the electrostatic arguments given in support of Minkowski's tensor in the Comment as unconvincing, and we point out that the issue of divergences raised in the Comment in the context of planar setups is not specific to Maxwell's stress tensor.

The conjunction of atom-cavity physics and photonic structures ("solid light" systems) offers new opportunities in terms of more device functionality and the probing of designed emulators of condensed matter systems. By analogy to the canonical one-electron approximation of solid state physics, we propose a one-polariton approximation to study these systems. Using this approximation we apply Bloch states to the uniformly tuned Jaynes-Cummings-Hubbard model to analytically determine the energy band structure. By analyzing the response of the band structure to local atom-cavity control we explore its application as a quantum simulator and show phase transition features absent in mean field theory. Using this novel approach for solid light systems we extend the analysis to include detuning impurities to show the solid light analogy of the semiconductor. This investigation also shows new features with no semiconductor analog.

In this paper the interface between two transformation media or between a transformation medium and vacuum is studied. Strictly from the transformation optics point of view the consequences of the boundary conditions at such interfaces are addressed in two different ways. First, we analyze a restricted class of reflectionless interfaces, for which the tools of transformation optics allow to describe the electromagnetic fields on both sides of the interface by means of the same vacuum solution of the Maxwell equations. In a second step, we examine interfaces between two arbitrary transformation media. This analysis is extended to the recently suggested generalization of transformation optics by the author. As a basic application it is shown how the standard law of reflection and refraction at an interface between vacuum and a homogeneous and isotropic medium with arbitrary and independent permittivity and permeability can be understood in a completely geometric way by the use of generalized transformation optics.

We propose a new optical scheme to literally see Anderson localization by varying the optical wavelength or the angle of incidence in order to tune between localized and delocalized states in a random multilayered filter. This scheme allows us to clearly differentiate absorption from localization effects because the system behaves as a filter centered at a given wavelength, where only one wavelength is perfectly transmitted and all others are fully localized. At the resonant wavelength, the transmission is exactly one in the absence of absorption. The presence of absorption only changes the overall transmission but not the wavelength dependence. These results were obtained by developing a new theoretical framework for the average optical transmission through disordered media.

Circular microresonators are micron sized dielectric disks embedded in material of lower refractive index. They possess modes of extremely high Q-factors (low lasing thresholds) which makes them ideal candidates for the realization of miniature laser sources. They have, however, the disadvantage of isotropic light emission caused by the rotational symmetry of the system. In order to obtain high directivity of the emission while retaining high Q-factors, we consider a microdisk with a pointlike scatterer placed off-center inside of the disk. We calculate the resulting resonant modes and show that some of them possess both of the desired characteristics. The emission is predominantly in the direction opposite to the scatterer. We show that classical ray optics is a useful guide to optimizing the design parameters of this system. We further find that exceptional points in the resonance spectrum influence how complex resonance wavenumbers change if system parameters are varied.

Several wave function approximations describing spontaneous parametric down-conversion can be found in the literature. Basically all cases are derived from the standard Hamiltonian for parametric down-conversion. Most frequently, particular cases describing collinear or paraxial approximations are described. This work presents a wave function in compact form, valid for all cases of single photon-pair conversion (Type I or Type II), for all angles allowed by the phase matching conditions and for all orbital angular momentum values l. Examples are given of coincidence structures to be expected for signal and idler photons. Partial transfer of orbital angular momentum from the pump laser to the photon pair is discussed. Some hypothesis for the decay channels of the non-transferred part of the orbital angular momentum are made. PACS: 42.65.Lm 42.50.Dv 42.50.Tx

We demonstrate that the characteristics of the high-order harmonic spectra generated by few-cycle carrier-envelope phase stabilized pulses can be finely adjusted by controlling the time dependent ellipticity. The experimental measurements show evidence for the generation of single, pairs and trains of attosecond pulses by controlling the time window of linear polarization of the driving pulses. The influence of the carrier-envelope phase on the generation process in different confinement configurations is interpreted and analyzed using a non-adiabatic stationary phase model. We show that the XUV emission depends critically on particular aspects of the fundamental electric field that allows to steer the electron trajectories on the time scale of tens of attoseconds.