References of "Physical Review. A"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailMultiqubit symmetric states with maximally mixed one-qubit reductions
Baguette, Dorian ULg; Bastin, Thierry ULg; Martin, John ULg

in Physical Review. A (2014), 90

We present a comprehensive study of maximally entangled symmetric states of arbitrary numbers of qubits in the sense of the maximal mixedness of the one-qubit reduced density operator. A general criterion ... [more ▼]

We present a comprehensive study of maximally entangled symmetric states of arbitrary numbers of qubits in the sense of the maximal mixedness of the one-qubit reduced density operator. A general criterion is provided to easily identify whether given symmetric states are maximally entangled in that respect or not. We show that these maximally entangled symmetric (MES) states are the only symmetric states for which the expectation value of the associated collective spin of the system vanishes, as well as in corollary the dipole moment of the Husimi function. We establish the link between this kind of maximal entanglement, the anticoherence properties of spin states, and the degree of polarization of light fields. We analyze the relationship between the MES states and the classes of states equivalent through stochastic local operations with classical communication (SLOCC). We provide a nonexistence criterion of MES states within SLOCC classes of qubit states and show in particular that the symmetric Dicke state SLOCC classes never contain such MES states, with the only exception of the balanced Dicke state class for even numbers of qubits. The 4-qubit system is analyzed exhaustively and all MES states of this system are identified and characterized. Finally the entanglement content of MES states is analyzed with respect to the geometric and barycentric measures of entanglement, as well as to the generalized N-tangle. We show that the geometric entanglement of MES states is ensured to be larger than or equal to 1/2, but also that MES states are not in general the symmetric states that maximize the investigated entanglement measures. [less ▲]

Detailed reference viewed: 32 (6 ULg)
Full Text
Peer Reviewed
See detailNonlinear Schrödinger wave equation with linear quantum behavior
Richardson, Christopher ULg; Schlagheck, Peter ULg; Martin, John ULg et al

in Physical Review. A (2014), 89

We show that a nonlinear Schro ̈dinger wave equation can reproduce all the features of linear quantum mechanics. This nonlinear wave equation is obtained by exploring, in a uniform language, the ... [more ▼]

We show that a nonlinear Schro ̈dinger wave equation can reproduce all the features of linear quantum mechanics. This nonlinear wave equation is obtained by exploring, in a uniform language, the transition from fully classical theory governed by a nonlinear classical wave equation to quantum theory. The classical wave equation includes a nonlinear classicality enforcing potential which when eliminated transforms the wave equation into the linear Schro ̈dinger equation. We show that it is not necessary to completely cancel this nonlinearity to recover the linear behavior of quantum mechanics. Scaling the classicality enforcing potential is sufficient to have quantumlike features appear and is equivalent to scaling Planck’s constant. [less ▲]

Detailed reference viewed: 8 (2 ULg)
Full Text
Peer Reviewed
See detailPolarization radiation of vortex electrons with large orbital angular momentum
Ivanov, Igor ULg; Karlovets, Dmitry

in Physical Review. A (2013), 88(4), 043840

Vortex electrons—freely propagating electrons whose wave functions have helical wave fronts—could become a novel tool in the physics of electromagnetic radiation. They carry a nonzero intrinsic orbital ... [more ▼]

Vortex electrons—freely propagating electrons whose wave functions have helical wave fronts—could become a novel tool in the physics of electromagnetic radiation. They carry a nonzero intrinsic orbital angular momentum (OAM) ℓ with respect to the propagation axis and, for ℓ≫1, a large OAM-induced magnetic moment μ≈ℓμB (μB is the Bohr magneton), which influences the radiation of electromagnetic waves. Here, we consider in detail the OAM-induced effects caused by such electrons in two forms of polarization radiation, namely, in Cherenkov radiation and transition radiation. Thanks to the large ℓ, we can neglect quantum or spin-induced effects, which are of the order of ℏω/Ee≪1, but retain the magnetic moment contribution ℓℏω/Ee≲1, which makes the quasiclassical approach to polarization radiation applicable. We discuss the magnetic moment contribution to polarization radiation, which has never been experimentally observed, and study how its visibility depends on the kinematical parameters and the medium permittivity. In particular, it is shown that this contribution can, in principle, be detected in azimuthally nonsymmetrical problems, for example when vortex electrons obliquely cross a metallic screen (transition radiation) or move near it (diffraction radiation). We predict a left-right angular asymmetry of the transition radiation (in the plane where the charge radiation distributions would stay symmetric), which appears due to an effective interference between the charge radiation field and the magnetic moment contribution. Numerical values of this asymmetry for vortex electrons with Ee=300 keV and ℓ=100–1000 are 0.1%–1%, and we argue that this effect could be detected with existing technology. The finite conductivity of the target and frequency dispersion play crucial roles in these predictions. [less ▲]

Detailed reference viewed: 16 (4 ULg)
Full Text
Peer Reviewed
See detailDeterministic generation of arbitrary symmetric states and entanglement classes
Lamata, Lucas; Lopez, C E; Lanyon, B P et al

in Physical Review. A (2013), 87

Detailed reference viewed: 18 (3 ULg)
Full Text
Peer Reviewed
See detailProposal for laser purification in molecular vibrational cooling using zero-width resonances
Atabek, Osman; Lefebvre, Roland; Jaouadi, Amine et al

in Physical Review. A (2013), 87(3), 031403

Detailed reference viewed: 13 (0 ULg)
Full Text
Peer Reviewed
See detailArtificial Abelian gauge potentials induced by dipole-dipole interactions between Rydberg atoms
Cesa, Alexandre ULg; Martin, John ULg

in Physical Review. A (2013), 88

We analyze the influence of dipole-dipole interactions between Rydberg atoms on the generation of Abelian artificial gauge potentials and fields. When two Rydberg atoms are driven by a uniform laser field ... [more ▼]

We analyze the influence of dipole-dipole interactions between Rydberg atoms on the generation of Abelian artificial gauge potentials and fields. When two Rydberg atoms are driven by a uniform laser field, we show that the combined atom-atom and atom-field interactions give rise to new, nonuniform, artificial gauge potentials. We identify the mechanism responsible for the emergence of these gauge potentials. Analytical expressions for the latter indicate that the strongest artificial magnetic fields are reached in the regime intermediate between the dipole blockade regime and the regime in which the atoms are sufficiently far apart such that atom-light interaction dominates over atom-atom interactions. We discuss the differences and similarities of artificial gauge fields originating from resonant dipole-dipole and van der Waals interactions. We also give an estimation of experimentally attainable artificial magnetic fields resulting from this mechanism and we discuss their detection through the deflection of the atomic motion. [less ▲]

Detailed reference viewed: 63 (20 ULg)
Full Text
Peer Reviewed
See detailLocalized electron dynamics in attosecond-pulse-excited molecular systems: Probing the time-dependent electron density by sudden photoionization
Mignolet, Benoît ULg; Levine, Raphael; Remacle, Françoise ULg

in Physical Review. A (2012)

Ultrafast UV excitation can prepare a nonstationary coherent superposition of molecular electronic states. The purely electronic dynamics before the onset of nuclear motion can be probed by a sudden XUV ... [more ▼]

Ultrafast UV excitation can prepare a nonstationary coherent superposition of molecular electronic states. The purely electronic dynamics before the onset of nuclear motion can be probed by a sudden XUV ionization of the electronic wave packet. Dynamical computations at the many-electron level on the LiH and 1-azabicyclo[3.3.3]undecane (C10H19N) molecules showthat molecular frame photoelectron angular distributions reflect the spatial localization and undulations of the electronic coherent superposition accessed by the initial ultrafast UV excitation. The sudden ionization is sensitive to interference effects. [less ▲]

Detailed reference viewed: 19 (4 ULg)
Full Text
Peer Reviewed
See detailDelocalization of ultracold atoms in a disordered potential due to light scattering
Nowak, Boris; Kinnunen, Jami J.; Holland, Murray J. et al

in Physical Review. A (2012), 86

We numerically study the expansion dynamics of ultracold atoms in a one-dimensional disordered potential in the presence of a weak position measurement of the atoms. We specifically consider this position ... [more ▼]

We numerically study the expansion dynamics of ultracold atoms in a one-dimensional disordered potential in the presence of a weak position measurement of the atoms. We specifically consider this position measurement to be realized by a combination of an external laser and a periodic array of optical microcavities along a waveguide. The position information is acquired through the scattering of a near-resonant laser photon into a specific eigenmode of one of the cavities. The time evolution of the atomic density in the presence of this light-scattering mechanism is described within a Lindblad master equation approach, which is numerically implemented using the Monte Carlo wave function technique. We find that an arbitrarily weak rate of photon emission leads to a breakdown of Anderson localization of the atoms. [less ▲]

Detailed reference viewed: 23 (2 ULg)
Full Text
Peer Reviewed
See detailMultipartite-entanglement monotones and polynomial invariants
Eltschka, Christopher; Bastin, Thierry ULg; Osterloh, Andreas et al

in Physical Review. A (2012), 85

We show that a positive homogeneous function that is invariant under determinant 1 stochastic local operations and classical communication (SLOCC) transformations defines an N-qubit entanglement monotone ... [more ▼]

We show that a positive homogeneous function that is invariant under determinant 1 stochastic local operations and classical communication (SLOCC) transformations defines an N-qubit entanglement monotone if and only if the homogeneous degree is not larger than four. We then describe a common basis and formalism for the N-tangle and other known invariant polynomials of degree four. This allows us to elucidate the relation of the four-qubit invariants defined by Luque and Thibon [Phys. Rev. A 67, 042303 (2003)] and the reduced two-qubit density matrices of the states under consideration, thus giving a physical interpretation for those invariants. We demonstrate that this is a special case of a completely general law that holds for any multipartite system with bipartitions of equal dimension, e.g., for an even number of qudits. [less ▲]

Detailed reference viewed: 23 (2 ULg)
Full Text
Peer Reviewed
See detailErratum: Multipartite-entanglement monotones and polynomial invariants
Eltschka, Christopher; Bastin, Thierry ULg; Osterloh, Andreas et al

in Physical Review. A (2012), 85

Detailed reference viewed: 15 (0 ULg)
Full Text
Peer Reviewed
See detailSimulating the coupling of angular momenta in distant matter qubits
Ammon, Christian; Maser, Andreas; Schilling, Uwe et al

in Physical Review. A (2012), 86

Detailed reference viewed: 17 (0 ULg)
Full Text
Peer Reviewed
See detailAddendum to “Scattering of twisted particles: Extension to wave packets and orbital helicity”
Ivanov, Igor ULg; Serbo, Valery

in Physical Review. A (2011), 84(6), 065802

In a recent work [ Phys. Rev. A 84 033804 (2011)] we considered elastic scattering of a twisted particle from a plane wave and studied how the orbital helicity of the twisted particle changes after ... [more ▼]

In a recent work [ Phys. Rev. A 84 033804 (2011)] we considered elastic scattering of a twisted particle from a plane wave and studied how the orbital helicity of the twisted particle changes after scattering. We showed that for realistic beams the relative change can be small, |m′−m|/m≪1, thus resolving a controversy which existed in the literature. In this Addendum, using a more accurate analysis, we argue that in the kinematics of Compton backscattering a stronger statement is true: in fact m′≈m, and the difference |m′−m| even by a single unit is already suppressed. [less ▲]

Detailed reference viewed: 23 (0 ULg)
Full Text
Peer Reviewed
See detailScattering of twisted particles: Extension to wave packets and orbital helicity
Ivanov, Igor ULg; Serbo, Valery

in Physical Review. A (2011), 84(3), 033804

High-energy photons and other particles carrying nonzero orbital angular momentum (OAM) emerge as a new tool in high-energy physics. Recently, it was suggested to generate high-energy photons with nonzero ... [more ▼]

High-energy photons and other particles carrying nonzero orbital angular momentum (OAM) emerge as a new tool in high-energy physics. Recently, it was suggested to generate high-energy photons with nonzero OAM (twisted photons) by the Compton backscattering of twisted optical photons on relativistic electron beams. Twisted electrons in the intermediate energy range have also been demonstrated experimentally; twisted protons and other particles can, in principle, be created in a similar way. Collisions of energetic twisted states can offer a new look at particle properties and interactions. A theoretical description of twisted particle scattering developed previously treated them as pure Bessel states and ran into difficulty when describing the OAM of the final twisted particle at nonzero scattering angles. Here we develop further this formalism by incorporating two additional important features. First, we treat the initial OAM state as a wave packet of a finite transverse size rather than a pure Bessel state. This realistic assumption allows us to resolve the existing controversy between two theoretical analyses for nonforward scattering. Second, we describe the final twisted particle in terms of the orbital helicity: the OAM projection on its average direction of propagation rather than on the fixed reaction axis. Using this formalism, we determine to what extent the twisted state is transferred from the initial to final OAM particle in a generic scattering kinematics. As a particular application, we prove that in the Compton backscattering the orbital helicity of the final photon stays close to the OAM projection of the initial photon. [less ▲]

Detailed reference viewed: 13 (0 ULg)
Full Text
Peer Reviewed
See detailDensity functional theory beyond the linear regime: Validating an adiabatic local density approximation
Helbig, N.; Fuks, J. I.; Casula, M. et al

in Physical Review. A (2011), 83

We present a local density approximation (LDA) for one-dimensional (1D) systems interacting via the soft-Coulomb interaction based on quantum Monte Carlo calculations. Results for the ground-state ... [more ▼]

We present a local density approximation (LDA) for one-dimensional (1D) systems interacting via the soft-Coulomb interaction based on quantum Monte Carlo calculations. Results for the ground-state energies and ionization potentials of finite 1D systems show excellent agreement with exact calculations obtained by exploiting the mapping of an N-electron system in d dimensions onto a single electron in N×d dimensions, properly symmetrized by the Young diagrams. We conclude that 1D LDA is of the same quality as its three-dimensional (3D) counterpart, and we infer conclusions about 3D LDA. The linear and nonlinear time-dependent responses of 1D model systems using LDA, exact exchange, and the exact solution are investigated and show very good agreement in both cases, except for the well-known problem of missing double excitations. Consequently, the 3D LDA is expected to be of good quality beyond the linear response. In addition, the 1D LDA should prove useful in modeling the interaction of atoms with strong laser fields, where this specific 1D model is often used. [less ▲]

Detailed reference viewed: 73 (6 ULg)
Full Text
Peer Reviewed
See detailEntanglement equivalence of N-qubit symmetric states
Mathonet, Pierre ULg; Krins, Stéphanie ULg; Godefroid, M. et al

in Physical Review. A (2010), 81

We study the interconversion of multipartite symmetric N-qubit states under stochastic local operations and classical communication (SLOCC). We demonstrate that if two symmetric states can be connected ... [more ▼]

We study the interconversion of multipartite symmetric N-qubit states under stochastic local operations and classical communication (SLOCC). We demonstrate that if two symmetric states can be connected with a nonsymmetric invertible local operation (ILO), then they belong necessarily to the separable, W, or Greenberger-Horne-Zeilinger (GHZ) entanglement class, establishing a practical method of discriminating subsets of entanglement classes. Furthermore, we prove that there always exists a symmetric ILO connecting any pair of symmetric N-qubit states equivalent under SLOCC, simplifying the requirements for experimental implementations of local interconversion of those states. [less ▲]

Detailed reference viewed: 39 (12 ULg)
Full Text
Peer Reviewed
See detailTunable entanglement, antibunching, and saturation effects in dipole blockade
Gillet, Jérémie ULg; Agarwal, G. S.; Bastin, Thierry ULg

in Physical Review. A (2010), 81

We report a model that makes it possible to analyze quantitatively the dipole blockade effect on the dynamical evolution of a two two-level atom system driven by an external laser field. The multiple ... [more ▼]

We report a model that makes it possible to analyze quantitatively the dipole blockade effect on the dynamical evolution of a two two-level atom system driven by an external laser field. The multiple excitations of the atomic sample are taken into account. We find very large concurrence in the dipole blockade regime. We further find that entanglement can be tuned by changing the intensity of the exciting laser. We also report a way to lift the dipole blockade paving the way to manipulate in a controllable way the blockade effects. We finally report how a continuous monitoring of the dipole blockade would be possible using photon-photon correlations of the scattered light in a regime where the spontaneous emission would dominate dissipation in the sample. [less ▲]

Detailed reference viewed: 37 (14 ULg)
Full Text
Peer Reviewed
See detailOperational multipartite entanglement classes for symmetric photonic qubit states
Kiesel, N.; Wieczorek, W.; Krins, Stéphanie ULg et al

in Physical Review. A (2010), 81

We present experimental schemes that allow us to study the entanglement classes of all symmetric states in multiqubit photonic systems. We compare the efficiency of the proposed schemes and highlight the ... [more ▼]

We present experimental schemes that allow us to study the entanglement classes of all symmetric states in multiqubit photonic systems. We compare the efficiency of the proposed schemes and highlight the relation between the entanglement properties of symmetric Dicke states and a recently proposed entanglement scheme for atoms. In analogy to the latter, we obtain a one-to-one correspondence between well-defined sets of experimental parameters and multiqubit entanglement classes inside the symmetric subspace of the photonic system. [less ▲]

Detailed reference viewed: 38 (11 ULg)
Full Text
Peer Reviewed
See detailAb initio calculation of H + He+ charge-transfer cross section for plasma physics
Loreau, Jérôme; Sodoga, Komi; Lauvergnat, David et al

in Physical Review. A (2010), 82

Detailed reference viewed: 31 (5 ULg)
Full Text
Peer Reviewed
See detailRadiative lifetime measurements and calculations of odd-parity highly excited levels in Ba I
Zhang, W; Palmeri, P; Quinet, Pascal ULg et al

in Physical Review. A (2010), 82

Detailed reference viewed: 3 (0 ULg)