| 1. |
- Antoine, P, et al.
(författare)
-
Generation of attosecond pulses in macroscopic media
- 1997
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 56:6, s. 4960-4969
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Tidskriftsartikel (refereegranskat)abstract
- We describe theoretically the generation of ultrashort (subfemtosecond) pulses using high-order harmonics of a laser pulse with a time-dependent degree of ellipticity. The single-atom response is calculated by using a low-frequency strong-field approximation. Propagation effects are taken into account using a method going beyond the slowly varying envelope approximation. Propagation modifies significantly the results obtained in the single-atom response and, in certain conditions, makes the generation of one attosecond pulse possible. We discuss prospects for the observation of these ultrashort pulses. [S1050-2947(97)09411-0].
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| 2. |
- Lynga, C, et al.
(författare)
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Temporal coherence of high-order harmonics
- 1999
-
Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 60:6, s. 4823-4830
-
Tidskriftsartikel (refereegranskat)abstract
- Systematic studies of the temporal coherence properties of high-order harmonic radiation are presented. These complement our previous investigations [Bellini et at, Phys. Rev. Lett. 81, 297 (1998)], where we showed the separation of the far-field pattern of high-order harmonics into two distinct spatial regions with different coherence times. Here we show how the coherence time of the inner and outer regions changes as a function of the harmonic order, the laser intensity, and the focusing conditions. Good agreement with the predictions of the semiclassical model of harmonic generation is obtained. [S1050-2947(99)10312-3].
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| 3. |
- Altucci, C, et al.
(författare)
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Frequency-resolved time-gated high-order harmonics
- 1998
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 58:5, s. 3934-3941
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Tidskriftsartikel (refereegranskat)abstract
- We report measurements of high-order harmonic spectra obtained with a 800-nm 150-fs loser pulse with a time-varying degree of ellipticity. The modulation of the polarization in time is achieved by using birefringent optics and self-phase modulation in a glass plate. We can create one or two temporal gates of a few femtoseconds width, during which the polarization is linear and harmonic emission is efficient. The harmonic spectra observed experimentally demonstrate that harmonics generated with linear polarization are frequency chirped. The values measured experimentally are consistent with theoretical predictions based on the strong field approximation. [S1050-2947(98)05511-5].
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| 4. |
- Lappas, D. G, et al.
(författare)
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Generation of attosecond xuv pulses in strong laser-atom interactions
- 1998
-
Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 58:5, s. 4140-4146
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Tidskriftsartikel (refereegranskat)abstract
- The generation of radiation pulses that can be as short as 120 attoseconds is demonstrated theoretically. We have employed a two-dimensional exact solution of the Schrodinger equation that allows for arbitrary laser ellipticity. By manipulating the laser ellipticity in time, it is shown that one can control the wave-packet dynamics of the ejected atomic electron. The nonlinear interaction of the electron with the atomic core can thus be restricted to extremely short times. Photon energies up to 160 eV are generated. It is also shown that with a higher laser frequency, even shorter pulses can be produced. [S1050-2947(98)02211-2].
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| 5. |
- Henderson, M, et al.
(författare)
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Lifetimes of the 5d(9)6p levels in HgIII
- 1999
-
Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 59:5, s. 4068-4070
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Tidskriftsartikel (refereegranskat)abstract
- We report measurements and theoretical calculations for the lifetimes of the 5d(9)6p levels in Hg nr with J = 0,2,3,4. This is an extension of earlier measurements of the lifetimes of the 5d(9)6p levels in Hg III with J = 1, and now provides data for all 12 of the levels. The results also provide an isoelectronic comparison with earlier studies of these levels in Au II of the Pt sequence, and a homologous comparison with earlier studies of the 4d(9)5p levels in Ag II, Cd III, and In IV in the Pd sequence. [S1050-2947(99)10905-3].
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| 6. |
- Gaarde, Mette, et al.
(författare)
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Spatiotemporal separation of high harmonic radiation into two quantum path components
- 1999
-
Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 59:2, s. 1367-1373
-
Tidskriftsartikel (refereegranskat)abstract
- We present a spatiotemporal analysis of high harmonic generation, showing evidence for the presence of several quantum path contributions to the atomic dipole moment. We show that the harmonic radiation can largely be described as a sum of two fields having a phase proportional to the intensity of the generating field. We compare our results to recent experimental results demonstrating this separation [M. Bellini et al., Phys. Rev. Lett. 81, 297 (1998)]. We show how the temporal and spatial coherence properties are influenced by this effect, and discuss how it could be used to obtain better control of the generated harmonic radiation. [S1050-2947(99)00402-3].
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| 7. |
- Roos, L, et al.
(författare)
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Controlling phase matching of high-order harmonic generation by manipulating the fundamental field
- 1999
-
Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 60:6, s. 5010-5018
-
Tidskriftsartikel (refereegranskat)abstract
- We study experimentally how to control and improve phase matching of high-order harmonic generation. We use a birefringent lens and a birefringent compensator to obtain a fundamental laser pulse (150 fs, 800 nm, similar to 4 mJ) With two foci Separated by 6.2 mm along the propagation axis and with a controllable phase delay between the polarizations along the optic axes of the birefringent optical components. This enables us to enhance the high-order harmonic conversion efficiency for the high-order harmonics in neon to 3 x 10(-8), a factor of 4 higher compared to a single-focus setup in similar conditions. The enhancement is achieved by improving the phase matching and at the same time maintaining a high intensity in a large generating volume. [S1050-2947(99)04512-6].
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| 8. |
- Abascal, Isabel Sainz, et al.
(författare)
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Bipartite entanglement measure based on covariance
- 2007
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 75:6
-
Tidskriftsartikel (refereegranskat)abstract
- We propose an entanglement measure for two quNits based on the covariances of a set of generators of the su(N) algebra. In particular, we represent this measure in terms of the mutually unbiased projectors for N prime. For pure states this measure quantifies entanglement, we obtain an explicit expression which relates it to the concurrence hierarchy, specifically the I-concurrence and the three-concurrence. For mixed states we propose a separability criterion.
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| 9. |
- Abdullaev, Fatkhulla, et al.
(författare)
-
Collective dynamics of Fermi-Bose mixtures with an oscillating scattering length
- 2019
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 99:3
-
Tidskriftsartikel (refereegranskat)abstract
- Collective oscillations of superfluid mixtures of ultra cold fermionic and bosonic atoms are investigated while varying the fermion-boson scattering length. We study the dynamics with respect to excited center of mass modes and breathing modes in the mixture. Parametric resonances are also analyzed when the scattering length varies periodically in time, by comparing partial differential equation (PDE) models and ordinary differential equation (ODE) models for the dynamics. An application to the recent experiment with fermionic Li-6 and bosonic Li-7 atoms, which approximately have the same masses, is discussed.
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| 10. |
- Abdullaev, Fatkhulla, et al.
(författare)
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Faraday waves in quasi-one-dimensional superfluid Fermi-Bose mixtures
- 2013
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 87:2
-
Tidskriftsartikel (refereegranskat)abstract
- The generation of Faraday waves in superfluid Fermi-Bose mixtures in elongated traps is investigated. The generation of waves is achieved by periodically changing a parameter of the system in time. Two types of modulations of parameters are considered: a variation of the fermion-boson scattering length and the boson-boson scattering length. We predict the properties of the generated Faraday patterns and study the parameter regions where they can be excited.
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| 11. |
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| 12. |
- Abramowicz, Marek A, 1945, et al.
(författare)
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Twin paradox on the photon sphere
- 2007
-
Ingår i: PHYSICAL REVIEW A. - 1050-2947. ; 75:4
-
Tidskriftsartikel (refereegranskat)
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| 13. |
- Acín, Antonio, et al.
(författare)
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Optimal randomness certification from one entangled bit
- 2016
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 93:4
-
Tidskriftsartikel (refereegranskat)abstract
- By performing local projective measurements on a two-qubit entangled state one can certify in a device-independent way up to one bit of randomness. We show here that general measurements, defined by positive-operator-valued measures, can certify up to two bits of randomness, which is the optimal amount of randomness that can be certified from an entangled bit. General measurements thus provide an advantage over projective ones for device-independent randomness certification.
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| 14. |
- Adamashvili, G. T., et al.
(författare)
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Influence of non-Markovian relaxation processes on self-induced transparency: Memory function theory for optical solitons
- 2008
-
Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 78:1
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of transverse relaxation on the resonance soliton (2 pi hyperbolic-secant pulse) in solids is considered. It is shown that memory effects can be considered in terms of generalized non-Markovian optical Bloch equations. The equations of self-induced transparency with a memory function are presented. Explicit forms for the first-order effects of this relaxation on the frequency shift and the pulse height of a resonant 2 pi soliton in solids are given and discussed. It is shown that memory effects do lead to a qualitative change in the dynamics of the influence of transverse relaxations on a 2 pi pulse in comparison to the McCall-Hahn theory and others. The dynamics of the changes of the inverse width of the pulse are obtained in both the Markovian and the non-Markovian cases with realistic parameters that can be achieved in current experiments.
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| 15. |
- Adesso, Gerardo, et al.
(författare)
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Coexistence of unlimited bipartite and genuine multipartite entanglement : Promiscuous quantum correlations arising from discrete to continuous variable systems
- 2007
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 76:2, s. 022315-
-
Tidskriftsartikel (refereegranskat)abstract
- Quantum mechanics imposes 'monogamy' constraints on the sharing of entanglement. We show that, despite these limitations, entanglement can be fully 'promiscuous', i.e. simultaneously present in unlimited two-body and many-body forms in states living in an infinite-dimensional Hilbert space. Monogamy just bounds the divergence rate of the various entanglement contributions. This is demonstrated in simple families of N-mode (N >= 4) Gaussian states of light fields or atomic ensembles, which therefore enable infinitely more freedom in the distribution of information, as opposed to systems of individual qubits. Such a finding is of importance for the quantification, understanding and potential exploitation of shared quantum correlations in continuous variable systems. We discuss how promiscuity gradually arises when considering simple families of discrete variable states, with increasing Hilbert space dimension towards the continuous variable limit. Such models are somehow analogous to Gaussian states with asymptotically diverging, but finite squeezing. In this respect, we find that non-Gaussian states (which in general are more entangled than Gaussian states), exhibit also the interesting feature that their entanglement is more shareable: in the non-Gaussian multipartite arena, unlimited promiscuity can be already achieved among three entangled parties, while this is impossible for Gaussian, even infinitely squeezed states.
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| 16. |
- Adesso, Gerardo, et al.
(författare)
-
Continuous variable entanglement sharing in noninertial frames
- 2007
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 76:6, s. 062112-
-
Tidskriftsartikel (refereegranskat)abstract
- We study the distribution of entanglement between modes of a free scalar field from the perspective of observers in uniform acceleration. We consider a two-mode squeezed state of the field from an inertial perspective, and analytically study the degradation of entanglement due to the Unruh effect, in the cases of either one or both observers undergoing uniform acceleration. We find that for two observers undergoing finite acceleration, the entanglement vanishes between the lowest frequency modes. The loss of entanglement is precisely explained as a redistribution of the inertial entanglement into multipartite quantum correlations among accessible and unaccessible modes from a non-inertial perspective. We show that classical correlations are also lost from the perspective of two accelerated observers but conserved if one of the observers remains inertial.
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| 17. |
- Adesso, Gerardo, et al.
(författare)
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Entanglement in Gaussian matrix-product states
- 2006
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 74:3, s. 030305(R)-
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Tidskriftsartikel (refereegranskat)abstract
- Gaussian matrix product states are obtained as the outputs of projection operations from an ancillary space of M infinitely entangled bonds connecting neighboring sites, applied at each of N sites of an harmonic chain. Replacing the projections by associated Gaussian states, the 'building blocks', we show that the entanglement range in translationally-invariant Gaussian matrix product states depends on how entangled the building blocks are. In particular, infinite entanglement in the building blocks produces fully symmetric Gaussian states with maximum entanglement range. From their peculiar properties of entanglement sharing, a basic difference with spin chains is revealed: Gaussian matrix product states can possess unlimited, long-range entanglement even with minimum number of ancillary bonds (M=1). Finally we discuss how these states can be experimentally engineered from N copies of a three-mode building block and N two-mode finitely squeezed states.
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| 18. |
- Aguilar, A., et al.
(författare)
-
Double photodetachment from the Cl[-]ion
- 2004
-
Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 2469-9926 .- 2469-9934. ; 69:2
-
Tidskriftsartikel (refereegranskat)abstract
- The correlated process involving the photodetachment of two electrons from the [Formula Presented] ion has been investigated over the photon energy range 20–45 eV. In the experiment, a beam of photons from the Advanced Light Source (ALS) was collinearly merged with a counterpropagating beam of [Formula Presented] ions from a sputter ion source. The [Formula Presented] ions produced in the interaction region were detected, and the normalized signal was used to monitor the relative cross section for the reaction. An absolute scale for the cross section was established by measuring the spatial overlap of the two beams and by determining the efficiency for collection and detection of the [Formula Presented] ions. The overall magnitude and shape of the measured cross section for this process agrees well with an R-matrix calculation. The calculation identifies the dominant mechanism leading to the production of the [Formula Presented] ion as being a direct nonresonant process involving the ejection of a pair of electrons from the valence shell. Less important is the indirect nonresonant process that involves the production and decay of core-excited and doubly excited states of the Cl atom in an intermediate step. Direct and indirect resonant mechanisms involving the excitation of a single [Formula Presented] core electron or more than one valence electron of the [Formula Presented] ion were found to be insignificant in the energy range studied.
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| 19. |
- Ahmed, Ergin H., et al.
(författare)
-
All-optical cw quadruple resonance excitation: A coherently driven five-level molecular system
- 2009
-
Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 79:6
-
Tidskriftsartikel (refereegranskat)abstract
- We report here a continuous-wave, high-resolution, and all-optical quadruple resonance laser excitation experiment. To demonstrate this excitation technique, we have used an inhomogeneously broadened molecular sample (Na-2). We emphasize the enhanced ability afforded by the technique to reach new ranges of internuclear separation as well as access to a large range of molecular electronic states. Using the Autler-Townes split line shape of a rovibronic transition and the E field amplitude of the corresponding coupling laser, we have measured with high precision the absolute value of the molecular electronic transition dipole moment matrix elements, with more flexibility than the double and the triple resonance based excitation schemes used previously. This technique may also be used in a stimulated Raman adiabatic passage configuration for effective transfer of ultracold molecules, formed at long internuclear distance, to the lowest vibrational level of the ground electronic state.
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| 20. |
- Ahufinger, V., et al.
(författare)
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Disordered ultracold atomic gases in optical lattices : A case study of Fermi-Bose mixtures
- 2005
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 72:6
-
Tidskriftsartikel (refereegranskat)abstract
- We present a review of properties of ultracold atomic Fermi-Bose mixtures in inhomogeneous and random optical lattices. In the strong interacting limit and at very low temperatures, fermions form, together with bosons or bosonic holes, composite fermions. Composite fermions behave as a spinless interacting Fermi gas, and in the presence of local disorder they interact via random couplings and feel effective random local potential. This opens a wide variety of possibilities of realizing various kinds of ultracold quantum disordered systems. In this paper we review these possibilities, discuss the accessible quantum disordered phases, and methods for their detection. The discussed quantum phases include Fermi glasses, quantum spin glasses, “dirty†superfluids, disordered metallic phases, and phases involving quantum percolation.
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| 21. |
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| 22. |
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| 23. |
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| 24. |
- Alagia, M., et al.
(författare)
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Probing the potential energy surface by highresolution x-ray absorption spectroscopy : The umbrella motion of the coreexcited CH3 free radical
- 2007
-
Ingår i: Physical Review. A. - 1050-2947 .- 1094-1622. ; 76:2, s. 124305-
-
Tidskriftsartikel (refereegranskat)abstract
- A detailed study of the umbrellalike vibration in inner-shell spectroscopy is presented. The high-resolution x-ray absorption spectrum for the lowest lying core excitation of the CH3 free radical was recorded. High quality potential energy surfaces (PES) for the initial and final states of the transition were calculated as a function of the symmetrical stretching and the umbrella deformation coordinates. The strong anharmonicity along the umbrella coordinate in the double-well region of the PES of the core excited state has a strong effect on the bending vibrational progressions. The excellent agreement between the experiment and theory allows an accurate spectroscopic characterization of the vibrational structure of the electronic transition, and the estimation of the umbrella inversion time of 149 fs.
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| 25. |
- Alhassid, Y, et al.
(författare)
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Fano interference and cross-section fluctuations in molecular photodissociation
- 2006
-
Ingår i: Physical Review A. - 1050-2947. ; 73
-
Tidskriftsartikel (refereegranskat)abstract
- We derive an expression for the total photodissociation cross section of a molecule incorporating both direct and indirect processes that proceed through excited resonances, and show that it exhibits generalized Beutler-Fano line shapes. Assuming that the closed system can be modeled by random-matrix theory, we derive the statistical properties of the photodissociation cross section and find that they are significantly affected by the direct processes. In the limit of isolated resonances, we find that direct processes suppress the correlation hole of the cross-section autocorrelation function and lead to a maximum in the cross-section distribution.
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| 26. |
- Allahverdyan, A, et al.
(författare)
-
Brownian entanglement
- 2005
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 72, s. 032102-
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Tidskriftsartikel (refereegranskat)
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| 27. |
- Amusia, MY, et al.
(författare)
-
Directed motion of electrons in gases under the action of photon flux - art. no. 052512
- 2001
-
Ingår i: PHYSICAL REVIEW A. - : AMERICAN PHYSICAL SOC. - 1050-2947. ; 6305:5, s. 2512-
-
Tidskriftsartikel (refereegranskat)abstract
- The phenomenon of directed motion of electrons and ions in gases under the action of ionizing radiation pressure is investigated. It is shown that for photon energies from the thresholds of atomic photoionization to several keV the photoionization process
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| 28. |
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| 29. |
- Anderson, Emma K., et al.
(författare)
-
Decays of excited silver-cluster anions Agn, n=4 to 7, in the Double ElectroStatic Ion Ring ExpEriment
- 2018
-
Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - 2469-9926 .- 2469-9934. ; 98:2
-
Tidskriftsartikel (refereegranskat)abstract
- Spontaneous decays of small, hot silver-cluster anions Ag-n(-), n = 4-7, have been studied using one of the rings of the Double ElectroStatic Ion Ring ExpEriment (DESIREE). Observation of these decays over very long time scales is possible due to the very low residual gas pressure (similar to 10(-14)) and cryogenic (13 K) operation of DESIREE. The yield of neutral particles from stored beams of Ag-6(-) and Ag-2(-) anions were measured for 100 milliseconds and were found to follow single power-law behavior with millisecond time-scale exponential cutoffs. The Ag-4(-) and Ag-5(-) anions were stored for 60 s and the observed decays show two-component power-law behaviors. We present calculations of the rate constants for electron detachment from and fragmentation of Ag-4(-) and Ag-5(-). In these calculations, we assume that the internal energy distribution of the clusters are flat and with this we reproduce the early steep parts of the experimentally measured decay curves for Ag-4(-) and Ag-5(-) which extends to tens and hundreds of milliseconds, respectively. The fact that the calculations reproduce the early slopes of Ag-4(-) and Ag-5(-), which differ for the two cases, suggests that it is the changes in fragmentation rates with internal cluster energies of Ag-4(-) and Ag-5(-) rather than conditions in the ion source that determine this behavior. Comparisons with the measurements strongly suggest that the neutral particles detected in these time domains originate from Ag-4(-) -> Ag-3(-) + Ag and Ag-5(-) -> Ag-3(-) +Ag-2 fragmentation processes.
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| 30. |
- Andersson, E., et al.
(författare)
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Formation of Kr3+ via core-valence doubly ionized intermediate states
- 2012
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 85:3, s. 032502-
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Tidskriftsartikel (refereegranskat)abstract
- The time-of-flight photoelectron-photoion coincidence technique has been used to study single-photon 3d(9)4p(5) core-valence double ionization of Kr and subsequent Auger decay to triply charged states associated with the 4s(2)4p(3) and 4s(1)4p(4) configurations. The photon energy used was h nu = 150 eV. Multiconfiguration Dirac-Fock calculations were performed both for the doubly ionized intermediate states and the triply ionized final states. The intermediate states of Kr2+ are observed between 120 and 125 eV, whereas the final states of Kr3+ are observed between 74- and 120-eV ionization energy. Assignments of all structures are made based on the present numerical results. The calculated Auger rates give a detailed explanation of the relative line strengths observed.
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| 31. |
- Andersson, Egil, 1981-, et al.
(författare)
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Multielectron coincidence study of the double Auger decay of 3d-ionized krypton
- 2010
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 82:4, s. 043418-
-
Tidskriftsartikel (refereegranskat)abstract
- Multielectron coincidence data for triple ionization of krypton have been recorded above the 3d ionization threshold at two photon energies (140 and 150 eV). Three principal transition pathways have been observed, two involving double Auger transitions from Kr+, and one involving single Auger transitions from Kr2+ created by direct single-photon double ionization. The decay of the 3d(9) D-2(5/2,3/2) states in Kr+ has been analyzed in some detail and is found to be strongly dominated by cascade processes where two electrons with well-defined energies are emitted. The decay paths leading to the 4s(2)4p(3) S-4, D-2, and P-2 states of Kr3+ are analyzed and energies of seven intermediate states in Kr2+ are given. A preliminary investigation of the decay paths from Kr+ 3d (9)4p(5)nl shake-up states has also been carried out.
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| 32. |
- Andersson, Egil, et al.
(författare)
-
Single-photon core-valence double ionization of molecular oxygen
- 2008
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 78, s. 023409-
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Tidskriftsartikel (refereegranskat)abstract
- Single-photon core-valence double ionization of molecular oxygen has been studied using a magnetic bottle time-of-flight electron coincidence spectrometer. The K-1V-1 double ionization electron spectrum of O-2 is reported and is assigned with the aid of ab initio calculations. A direct comparison of the core-valence double ionization electron spectra with the conventional valence band photoelectron spectrum is made. The lowest core-valence double ionization energy is found to be 571.6 eV and is associated with a (3)Pi dicationic state.
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| 33. |
- Andersson, Erika, et al.
(författare)
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Variational properties of a pumped dynamical system
- 2010
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 81:2, s. 022111-
-
Tidskriftsartikel (refereegranskat)abstract
- We earlier constructed a generalized entropy concept to show the direction of time in an evolution following from a Markov generator. In such a dynamical system the entity found changes in a monotonic way starting from any initial state of the system. In this article, we generalize the treatment to the case when population is pumped into the system from levels not explicitly considered. These populations then pass through the coupled levels and exit by decay to levels outside the system. We derive the form of the equation of motion and relate it to our earlier treatments. It turns out that the formalism can be generalized to the new situation. Its physically relevant features are demonstrated and the behavior obtained is illustrated by a numerical treatment of the standard two-level system with pumping and relaxation included.
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| 34. |
- Andersson, Jonas, et al.
(författare)
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Triple ionization of atomic Cd involving 4p(-1) and 4s(-1) inner-shell holes
- 2015
-
Ingår i: Physical Review A. - 1050-2947 .- 1094-1622. ; 92:2
-
Tidskriftsartikel (refereegranskat)abstract
- The triple ionization spectrum of atomic Cd formed upon the removal of a 4p or a 4s inner-shell electron and subsequent Auger decays has been obtained at 200 eV photon energy. By using a versatile multielectron coincidence detection technique based on a magnetic bottle spectrometer in combination with multiconfiguration Dirac-Fock calculations, Auger cascades leading to tricationic final states have been analyzed and final-state configurations have been identified. The most prominent Auger cascades leading to the ground state of Cd3+ have been identified in good agreement with theory.
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| 35. |
- Andersson, L. Mauritz, et al.
(författare)
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Nonadiabatic effects in the photoelectron spectra of HCl and DCl. II. Theory
- 2002
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 65:1
-
Tidskriftsartikel (refereegranskat)abstract
- The vibrationally resolved photoelectron spectra of HCl and DCl in the 25-28 eV region were computed using a time-dependent approach for the nuclear dynamics. The spectral features cannot be understood without including a nonadiabatic coupling between the dissociative 3 (2)Sigma(+) state and the bound 4 (2)Sigma(+) state in the adiabatic picture. Alternatively, in the diabatic picture a dissociative two-hole-one-particle state interacts with a bound one-hole state. The molecular system is of intermediate coupling strength, i.e., it cannot be described by a single potential-energy curve. The interaction between a bound and a dissociative state leads to Fano resonances superimposed on a broad back-round, as observed in the experimental spectra [Burmeister et al., Phys. Rev. A 65, 012704 (2001)]. From modified potential-energy curves, all features of the experimental spectra, including Fano resonance parameters and lifetimes, were reproduced. From the simulations we observe that two additional peaks in the experimental DCl spectra should appear if the resolution were to be enhanced to around 10 meV.
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| 36. |
- Andersson, Martin, et al.
(författare)
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Analysis of the competition between forbidden and hyperfine-induced transitions in Ne-like ions
- 2016
-
Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 93:3
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Tidskriftsartikel (refereegranskat)abstract
- In this work we investigate the decay of the |2p53sP03) state in neon-like ions along the isoelectronic sequence ranging from Z=10 to Z=35. In the absence of a nuclear spin, the magnetic dipole transition to |2p53sP13) is the dominating decay channel. However, for isotopes with a nuclear spin, the interaction between the nuclear magnetic dipole moment and the electronic field introduces a mixing of |2p53sP13) and |P11) into the |P03) state, which in turn opens up a competing hyperfine-induced electric dipole decay channel to the ground state. This hyperfine-induced transition channel clearly dominates over the magnetic dipole channel for the neutral end of the isoelectronic sequence, when present. We give values for the rates of both these competing channels and discuss how the introduction of the hyperfine-induced transition channel could have a dramatic influence on the spectrum, not only because it introduces a new line, but also since it can substantially decrease the intensity of the magnetic dipole 2p53sP03→2p53sP13 line and affect the predicted ionization balance in different plasmas.
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| 37. |
- Andersson, M, et al.
(författare)
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Hyperfine-dependent lifetimes in Be-like ions
- 2009
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 79:3
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Tidskriftsartikel (refereegranskat)abstract
- Theoretical investigations of hyperfine quenching of the two metastable levels 1s(2)2s2p P-3(0) and P-3(2) have been performed along the Be-like isoelectronic sequence for ions between Z=6-22. It is shown that the lifetime of the latter level is sensitive to hyperfine quenching in the beginning of the isoelectronic sequence, but the sensitivity decreases towards the high-Z end. It is also shown that the hyperfine dependent branching fraction between the 2s(2) S-1(0)-2s2p P-3(2) and the 2s2p P-3(1)-2s2p P-3(2) transitions can lead to some rather drastic changes in the spectra. Our predicted value of 0.677 s(-1) for the hyperfine-induced 2s(2) S-1(0)-2s2p P-3(0) transition rate for Ti-47(18+) are in disagreement with a recent experimental value of 0.56(3) s(-1). Our calculated values of this quenching are in agreement with other recent calculations all along the sequence.
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| 38. |
- Andersson, M., et al.
(författare)
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Hyperfine-interaction-dependent 4s4p P-3(2) lifetimes in Zn-like ions
- 2008
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 78:6
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Tidskriftsartikel (refereegranskat)abstract
- Theoretical studies on hyperfine-interaction-dependent lifetimes of the 4s4p P-3(2) states of Zn-like ions are reported in this paper. A systematic investigation along the isoelectronic sequence shows that the lifetime of the 4s4p P-3(2) level is very sensitive to hyperfine interaction at the beginning of the sequence, but gets less sensitive going to the higher end. The intensity ratio between the 4s(2) S-1(0)-4s4p P-3(2) and the 4s4p P-3(1)-4s4p P-3(2) transitions was also investigated and it is shown that this ratio is very sensitive to hyperfine interaction. In some isotopes the two branches are dominated by transitions from different upper hyperfine levels. Our research also reveals that the hyperfine-induced electric dipole transitions contribute to the transitions of 4s(2) S-1(0)-4s4p P-3(2) at about the same level as, or even higher than, M2 transitions whenever the nucleus has a spin. This is true all along the isoelectronic sequence.
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| 39. |
- Andersson, M., et al.
(författare)
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Hyperfine-state-dependent lifetimes along the Ni-like isoelectronic sequence
- 2008
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 77:4, s. 12-042509
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Tidskriftsartikel (refereegranskat)abstract
- An investigation of the lifetime of the 3d(9)4s D-3(3) level along a part of the nickel-like isoelectronic sequence has been performed. The focus of this work has been to evaluate the importance of the hyperfine induced electric quadrupole channel of the 3d(10) S-1(0)-3d(9)4s D-3(3) transition for isotopes with nuclear spin. Comparisons between the magnetic octupole transition rate and the hyperfine-induced electric quadrupole transition rate shows that the hyperfine quenching is of importance along the whole isoelectronic sequence. At the low-Z end the hyperfine induced electric quadrupole transition channel dominates, being several orders of magnitude larger than the rate for the magnetic octupole transition channel, while for higher Z the two rates are of comparable size.
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| 40. |
- Andersson, Ole, et al.
(författare)
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Device-independent certification of two bits of randomness from one entangled bit and Gisin's elegant Bell inequality
- 2018
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 97:1
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Tidskriftsartikel (refereegranskat)abstract
- We prove that as conjectured by Acín et al. [Phys. Rev. A 93, 040102(R) (2016)], two bits of randomness can be certified in a device-independent way from one bit of entanglement using the maximal quantum violation of Gisin's elegant Bell inequality. This suggests a surprising connection between maximal entanglement, complete sets of mutually unbiased bases, and elements of symmetric informationally complete positive operator-valued measures, on one side, and the optimal way of certifying maximal randomness, on the other.
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| 41. |
- Andersson, Pontus, 1971, et al.
(författare)
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Observation of the 2S1/2 metastable state in Pt−
- 2009
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Ingår i: PHYSICAL REVIEW A. - 1050-2947. ; 79, s. 022502 -
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Tidskriftsartikel (refereegranskat)abstract
- We have experimentally investigated the structure of the Pt− ion using laser photodetachment threshold spectroscopy. The experiment was conducted using a collinear laser-ion beam apparatus, in which the residual atoms created in the photodetachment process were detected. A p-wave threshold was observed in the photo- detachment spectrum at an energy of 6851͑13͒ cm−1. We conclude that this onset originates from a photode- tachment transition in which the initial state of Pt− is the previously unobserved 5d106s 2S1/2 state and the final state of Pt is the 5d96s 3D3 ground state. The excitation energy of the 2S1/2 state is determined to be 10 289͑13͒ cm−1. This value can be compared with a multiconfiguration Dirac-Fock calculation performed by Thøgersen et al. ͓Phys. Rev. Lett. 76, 2870 ͑1996͔͒, which yielded an excitation energy of 11 301 cm−1. Our data show no indication of the presence of any other state of Pt−. We conclude that the structure of the Pt− ion is now fully known.
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| 42. |
- Andersson, Pontus, 1971, et al.
(författare)
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Radiative lifetimes of metastable states of negative ions
- 2006
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622 .- 2469-9926 .- 2469-9934. ; 73, s. 032705-
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Tidskriftsartikel (refereegranskat)abstract
- We present a technique for measuring the radiative lifetimes of metastable states of negative ions that involves the use of a heavy-ion storage ring. The method has been applied to investigate the radiative decay of the np(3) P-2(1/2) levels of Te-(n=5) and Se-(n=4) and the 3p(3) D-2 state of Si- for which the J=3/2 and 5/2 levels were unresolved. All of these states are metastable and decay primarily by emission of E2 and M1 radiation. Multi Configuration Dirac-Hartree-Fock calculations of rates for the transitions in Te- and Se- yielded lifetimes of 0.45 s and 4.7 s, respectively. The measured values agree well with these predicted values. In the case of the D-2 state of Si-, however, our measurement was only able to set a lower limit on the lifetime. The upper limit of the lifetime that can be measured with our apparatus is set by how long the ions can be stored in the ring, a limit determined by the rate of collisional detachment. Our lower limit of 1 min for the lifetime of the D-2 state is consistent with both the calculated lifetimes of 162 s for the D-2(3/2) level and 27.3 h for the D-2(5/2) level reported by O'Malley and Beck and 14.5 h and 12.5 h, respectively, from our Breit-Pauli calculations.
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| 43. |
- André, Tomas, et al.
(författare)
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Dark path holonomic qudit computation
- 2022
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 106:6
-
Tidskriftsartikel (refereegranskat)abstract
- Nonadiabatic holonomic quantum computation is a method used to implement high-speed quantum gates with non-Abelian geometric phases associated with paths in state space. Due to their noise tolerance, these phases can be used to construct error resilient quantum gates. We extend the holonomic dark path qubit scheme in [M.-Z. Ai et al., Fundam. Res. 2, 661 (2022)] to qudits. Specifically, we demonstrate one- and two-qudit universality by using the dark path technique. Explicit qutrit (d = 3) gates are demonstrated and the scaling of the number of loops with the dimension d is addressed. This scaling is linear and we show how any diagonal qudit gate can be implemented efficiently in any dimension.
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| 44. |
- Antoine, P, et al.
(författare)
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Polarization of high-order harmonics
- 1997
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 55:2, s. 1314-1324
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Tidskriftsartikel (refereegranskat)abstract
- We report measurements and calculations of the polarization state of high-order harmonics generated by a 790-nm Ti:sapphire laser. The problem of completely characterizing the polarization state of a partially polarized radiation in the XUV range is discussed in detail. The comparison between several gases, xenon, argon and neon, and different orders, from the 17th to the 33rd, shows that the rotation angle and ellipticity strongly depends on the position of the harmonic in the spectrum, and in particular, whether it is in the cutoff or in the plateau. In the plateau, the rotation angle is quite large, and the ellipticity follows that of the fundamental, remaining, however, smaller. The radiation is only partially polarized. In contrast, in the cutoff, both rotation angle and ellipticity remain small, independently of the laser ellipticity. Our experimental results compare well with theoretical predictions including the single-atom response and propagation effects.
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| 45. |
- Antoine, P, et al.
(författare)
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Theory of high-order harmonic generation by an elliptically polarized laser field
- 1996
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 53:3, s. 1725-1745
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Tidskriftsartikel (refereegranskat)abstract
- We generalize a recently formulated theory of high-order harmonic generation by low-frequency laser fields [Anne L'Huillier et al., Phys. Rev. A 48, R3433 (1993)] to the case of an elliptically polarized light. Our theoretical description includes both the single-atom response and propagation. Phase matching significantly modifies the results obtained in the single-atom response. The results of our calculations, including propagation for both the intensity and polarization properties of harmonics as a function of laser ellipticity, compare very well with recent experimental observations.
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| 46. |
- Aolita, Leandro, et al.
(författare)
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Fully nonlocal quantum correlations
- 2012
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 85:3, s. 032107-
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Tidskriftsartikel (refereegranskat)abstract
- Quantum mechanics is a nonlocal theory, but not as nonlocal as the no-signalling principle allows. However, there exist quantum correlations that exhibit maximal nonlocality: they are as nonlocal as any nonsignalling correlation and thus have a local content, quantified by the fraction p(L) of events admitting a local description, equal to zero. We exploit the known link between the Kochen-Specker and Bell theorems to derive a maximal violation of a Bell inequality from every Kochen-Specker proof. We then show that these Bell inequalities lead to experimental bounds on the local content of quantum correlations that are significantly better than those based on other constructions. We perform the experimental demonstration of a Bell test originating from the Peres-Mermin Kochen-Specker proof, providing an upper bound on the local content pL less than or similar to 0.22.
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| 47. |
- Araujo, Mateus, et al.
(författare)
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Tests of bell inequality with arbitrarily low photodetection efficiency and homodyne measurements
- 2012
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 86:3, s. 030101-
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Tidskriftsartikel (refereegranskat)abstract
- We show that hybrid local measurements combining homodyne measurements and photodetection provide violations of a Bell inequality with arbitrarily low photodetection efficiency. This is shown in two different scenarios: when one part receives an atom entangled to the field mode to be measured by the other part and when both parts make similar photonic measurements. Our findings promote the hybrid measurement scenario as a candidate for loophole-free Bell tests beyond previous expectations.
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| 48. |
- Argenti, Luca, et al.
(författare)
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Photoionization of helium by attosecond pulses : Extraction of spectra from correlated wave functions
- 2013
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 87:5, s. 053405-
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the photoionization spectrum of helium by attosecond XUV pulses both in the spectral region of doubly excited resonances as well as above the double ionization threshold. In order to probe for convergence, we compare three techniques to extract photoelectron spectra from the wave packet resulting from the integration of the time-dependent Schrodinger equation in a finite-element discrete variable representation basis. These techniques are projection on products of hydrogenic bound and continuum states, projection onto multichannel scattering states computed in a B-spline close-coupling basis, and a technique based on exterior complex scaling implemented in the same basis used for the time propagation. These methods allow one to monitor the population of continuum states in wave packets created with ultrashort pulses in different regimes. Applications include photo cross sections and anisotropy parameters in the spectral region of doubly excited resonances, time-resolved photoexcitation of autoionizing resonances in an attosecond pump-probe setting, and the energy and angular distribution of correlated wave packets for two-photon double ionization.
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| 49. |
- Arteca, Gustavo A., et al.
(författare)
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Quantum states for quantum processes : A toy model for ammonia inversion spectra
- 2011
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 84:1, s. 012115-
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Tidskriftsartikel (refereegranskat)abstract
- Chemical transformations are viewed here as quantum processes modulated by external fields, that is, as shifts in reactant to product amplitudes within a quantum state represented by a linear (coherent) superposition of electronuclear basis functions; their electronic quantum numbers identify the "chemical species." This basis set can be mapped from attractors built from a unique electronic configurational space that is invariant with respect to the nuclear geometry. In turn, the quantum numbers that label these basis functions and the semiclassical potentials for the electronic attractors may be used to derive reaction coordinates to monitor progress as a function of the applied field. A generalization of Feynman's three-state model for the ammonia inversion process illustrates the scheme; to enforce symmetry for the entire inversion process model and ensure invariance with respect to nuclear configurations, the three attractors and their basis functions are computed with a grid of fixed floating Gaussian functions. The external-field modulation of the effective inversion barrier is discussed within this conceptual approach. This analysis brings the descriptions of chemical processes near modern technologies that employ molecules to encode information by means of confinement and external fields.
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| 50. |
- Arve, Per, et al.
(författare)
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Propagation of two-dimensional pulses in electromagnetically induced transparency media
- 2004
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 69:6, s. 063809-
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Tidskriftsartikel (refereegranskat)abstract
- The propagation in two dimensions of "optical" pulses in electromagnetically induced transparency media is analyzed. Results are presented for coupled Maxwell-Bloch equations with slowly varying envelope approximation, for both adiabatic and nonadiabatic situations. The possibility of changing the direction of the pulse by a switch of control beam direction is investigated in detail.
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