M. Lewenstein | ICFO-The Institute of Photonic Sciences (original) (raw)
Papers by M. Lewenstein
Physical Review E, 1993
... networks Andrzej Nowak Institute for Social Studies, Warsaw University, ul. Stawki 5/7, 00-18... more ... networks Andrzej Nowak Institute for Social Studies, Warsaw University, ul. Stawki 5/7, 00-183 Warsaw, Poland Maciej Lewenstein* Centre d'Etudes de Saclay, Service des Photons, Atomes et Molecules, Bbtiment 22, 91191 Gif sur Yvette CEDEX, France Wojciech Tarkowski ...
Research in Optical Sciences, 2012
ABSTRACT
Physical Review Letters, 2013
We present numerical simulations of high-order harmonic generation in helium using a temporally s... more We present numerical simulations of high-order harmonic generation in helium using a temporally synthesised and spatially non-homogeneous strong laser field. The combination of temporal and spatial laser field synthesis results in a dramatic cutoff extension far beyond the usual semiclassical limit. Our predictions are based on the convergence of three complementary approaches: resolution of the three dimensional Time Dependent Schrödinger Equation, time-frequency analysis of the resulting dipole moment and classical trajectories extraction. Employing a combination of temporally and spatially synthesised laser field provides coherent XUV photons beyond the carbon K-edge which is of high interest for initiating inner-shell dynamics and study time-resolved intra-molecular attosecond spectroscopy.
Physical Review A, 2012
We present theoretical studies of above threshold ionization (ATI) produced by spatially inhomoge... more We present theoretical studies of above threshold ionization (ATI) produced by spatially inhomogeneous fields. This kind of field appears as a result of the illumination of plasmonic nanostructures and metal nanoparticles with a short laser pulse. We use the time-dependent Schrödinger equation (TDSE) in reduced dimensions to understand and characterize the ATI features in these fields. It is demonstrated that the inhomogeneity of the laser electric field plays an important role in the ATI process and it produces appreciable modifications to the energy-resolved photoelectron spectra. In fact, our numerical simulations reveal that high energy electrons can be generated. Specifically, using a linear approximation for the spatial dependence of the enhanced plasmonic field and with a near infrared laser with intensities in the mid-10 14 W/cm 2 range, we show it is possible to drive electrons with energies in the near-keV regime. Furthermore, we study how the carrier envelope phase influences the emission of ATI photoelectrons for few-cycle pulses. Our quantum mechanical calculations are supported by their classical counterparts.
Physical Review A, 1997
A variational technique is applied to solve the time-dependent nonlinear Schrödinger equation ͑Gr... more A variational technique is applied to solve the time-dependent nonlinear Schrödinger equation ͑Gross-Pitaevskii equation͒ with the goal to model the dynamics of dilute ultracold atom clouds in the Bose-Einstein condensed phase. We derive analytical predictions for the collapse, equilibrium widths, and evolution laws of the condensate parameters and find them to be in very good agreement with our numerical simulations of the nonlinear Schrödinger equation. It is found that not only the number of particles, but also both the initial width of the condensate and the effect of different perturbations to the condensate may play a crucial role in the collapse dynamics. The results are applicable when the shape of the condensate is sufficiently simple.
Physical Review A, 1996
In this paper we examine some effects of quantum interference on high harmonic generation. We dem... more In this paper we examine some effects of quantum interference on high harmonic generation. We demonstrate in particular that preparing the initial state in a coherent superposition of bound states leads to a harmonic spectrum with distinct plateaus with different conversion efficiencies. We show how this scheme may provide a way of controlling the coherent output that is produced in an experiment. ͓S1050-2947͑96͒03611-6͔
Journal of Physics A: Mathematical and General, 1992
The authors formulate a method for estimating the critical conditions for storage of sets of data... more The authors formulate a method for estimating the critical conditions for storage of sets of data in neural network memory. This variational method is based on random matrix theory and calculating the average spectrum of a matrix, whose elements are given by overlaps of the stored patterns. Several generic cases of random overlap matrices are considered. They investigate the cases of simply uncorrelated random patterns and 'spatially' and 'semantically' correlated ones. They obtain bounds of the critical curve in the control parameters space, which determine the stability of the stored data sets.
The four classes of axioms that define quantum mechanics are the class describing the state of a ... more The four classes of axioms that define quantum mechanics are the class describing the state of a physical system (the ``static'' description), the measurement axioms, the axiom for states of indistinguishable particles, and the axiom stating that the dynamics must be unitary. The second law of thermodynamics states that disorder of a physical system, as quantified by its von Neumann entropy, is preserved in reversible processes. We show that assuming the static description of quantum mechanics, the unitarity of the dynamics follows from the second law of thermodynamics.
Annalen der Physik, 2012
We present theoretical studies of high-order harmonic generation (HHG) in rare gases driven by pl... more We present theoretical studies of high-order harmonic generation (HHG) in rare gases driven by plasmonic field enhancement. This kind of fields appears when plasmonic nanostructures are illuminated by an intense few-cycle laser and have a particular spatial dependency, depending on the geometrical shape of the nanostructure. We demonstrate that the strong nonhomogeneous character of the laser enhanced field plays an important role in the HHG process and significantly extends the harmonic cutoff. Our models are based on numerical solution of the time dependent Schrödinger equation (TDSE) and supported by classical and semiclassical calculations.
Journal of Physics A: Mathematical and Theoretical, 2011
Entanglement witnesses (EWs) constitute one of the most important entanglement detectors in quant... more Entanglement witnesses (EWs) constitute one of the most important entanglement detectors in quantum systems. Nevertheless, their complete characterization, in particular with respect to the notion of optimality, is still missing, even in the decomposable case. Here we show that for any qubit-qunit decomposable EW (DEW) W the three statements are equivalent: (i) the set of product vectors obeying e, f |W |e, f = 0 spans the corresponding Hilbert space, (ii) W is optimal, (iii) W = Q Γ with Q denoting a positive operator supported on a completely entangled subspace (CES) and Γ standing for the partial transposition. While, implications (i) ⇒ (ii) and (ii) ⇒ (iii) are known, here we prove that (iii) implies (i). This is a consequence of a more general fact saying that product vectors orthogonal to any CES in 2 ⊗ n span after partial conjugation the whole space. On the other hand, already in the case of 3 ⊗ 3 Hilbert space, there exist DEWs for which (iii) does not imply (i). Consequently, either (i) does not imply (ii), or (ii) does not imply (iii), and the above transparent characterization obeyed by qubit-qunit DEWs, does not hold in general.
Journal of Physics A: Mathematical and Theoretical, 2014
In 2008, the conjecture that structural physical approximations to optimal entanglement witnesses... more In 2008, the conjecture that structural physical approximations to optimal entanglement witnesses are separable states (in general unnormalized) was posed. In an attempt to disprove it, in (Ha K-C and Kye S-H, Separable states with unique decompositions, arXiv:1210.1088v3), Ha and Kye proposed a decomposable entanglement witness whose SPA is entangled and argued that it is optimal. In this note, which is based on a comment to the latter work (Augusiak et al, Comment on "Separable states with unique decompositions", arXiv:1304.2040v1), we show, both analytically and numerically, that this entanglement witness is not optimal, and as such it is not a counterexample to the conjecture. To this end, we make use of a method for checking optimality of entanglement witnesses developed already in (Lewenstein et al 2000 Phys. Rev. A 62 052310), however, hardly exploited so far in the literature.
Optics Communications, 2010
We study extremality in various sets of states that have positive partial transposes. One of the ... more We study extremality in various sets of states that have positive partial transposes. One of the tools we use for this purpose is the recently formulated criterion allowing to judge if a given state is extremal in the set of PPT states. First we investigate qubit-ququart states and show that the only candidates for extremal PPT entangled states (PPTES) have ranks of the state and its partial transposition (5, 5) or (5, 6) (equivalently (6, 5)). Then, examples of extremal states of (5, 5) type and the so-called edge states of type (5, 6) are provided. We also make an attempt to explore the set of PPT states with ranks (5, 6). Finally, we discuss what are the possible configurations of ranks of density matrices and their respective partial transposition in general three-qubit and four-qubit symmetric states for which there may exist extremal entangled PPT states. For instance in the first case we show that the only possibilities are (4, 4, 4) and (4, 4, 5).
Physical Review A, 1982
Equations of motion for a sample filled with totally inverted two-level atoms coupled to one-dime... more Equations of motion for a sample filled with totally inverted two-level atoms coupled to one-dimensional radiation field are solved in the linear regime without the slowlyvarying-envelope approximation. The comparison with known results neg. ecting the coupling between leftand right-going waves is made.
Numerical simulations show that laser cooling of fermions on the repulsive side of the Feshbach r... more Numerical simulations show that laser cooling of fermions on the repulsive side of the Feshbach resonance can sympathetically cool molecules well below their condensation temperature.
Physical Review E, 1993
... networks Andrzej Nowak Institute for Social Studies, Warsaw University, ul. Stawki 5/7, 00-18... more ... networks Andrzej Nowak Institute for Social Studies, Warsaw University, ul. Stawki 5/7, 00-183 Warsaw, Poland Maciej Lewenstein* Centre d'Etudes de Saclay, Service des Photons, Atomes et Molecules, Bbtiment 22, 91191 Gif sur Yvette CEDEX, France Wojciech Tarkowski ...
Research in Optical Sciences, 2012
ABSTRACT
Physical Review Letters, 2013
We present numerical simulations of high-order harmonic generation in helium using a temporally s... more We present numerical simulations of high-order harmonic generation in helium using a temporally synthesised and spatially non-homogeneous strong laser field. The combination of temporal and spatial laser field synthesis results in a dramatic cutoff extension far beyond the usual semiclassical limit. Our predictions are based on the convergence of three complementary approaches: resolution of the three dimensional Time Dependent Schrödinger Equation, time-frequency analysis of the resulting dipole moment and classical trajectories extraction. Employing a combination of temporally and spatially synthesised laser field provides coherent XUV photons beyond the carbon K-edge which is of high interest for initiating inner-shell dynamics and study time-resolved intra-molecular attosecond spectroscopy.
Physical Review A, 2012
We present theoretical studies of above threshold ionization (ATI) produced by spatially inhomoge... more We present theoretical studies of above threshold ionization (ATI) produced by spatially inhomogeneous fields. This kind of field appears as a result of the illumination of plasmonic nanostructures and metal nanoparticles with a short laser pulse. We use the time-dependent Schrödinger equation (TDSE) in reduced dimensions to understand and characterize the ATI features in these fields. It is demonstrated that the inhomogeneity of the laser electric field plays an important role in the ATI process and it produces appreciable modifications to the energy-resolved photoelectron spectra. In fact, our numerical simulations reveal that high energy electrons can be generated. Specifically, using a linear approximation for the spatial dependence of the enhanced plasmonic field and with a near infrared laser with intensities in the mid-10 14 W/cm 2 range, we show it is possible to drive electrons with energies in the near-keV regime. Furthermore, we study how the carrier envelope phase influences the emission of ATI photoelectrons for few-cycle pulses. Our quantum mechanical calculations are supported by their classical counterparts.
Physical Review A, 1997
A variational technique is applied to solve the time-dependent nonlinear Schrödinger equation ͑Gr... more A variational technique is applied to solve the time-dependent nonlinear Schrödinger equation ͑Gross-Pitaevskii equation͒ with the goal to model the dynamics of dilute ultracold atom clouds in the Bose-Einstein condensed phase. We derive analytical predictions for the collapse, equilibrium widths, and evolution laws of the condensate parameters and find them to be in very good agreement with our numerical simulations of the nonlinear Schrödinger equation. It is found that not only the number of particles, but also both the initial width of the condensate and the effect of different perturbations to the condensate may play a crucial role in the collapse dynamics. The results are applicable when the shape of the condensate is sufficiently simple.
Physical Review A, 1996
In this paper we examine some effects of quantum interference on high harmonic generation. We dem... more In this paper we examine some effects of quantum interference on high harmonic generation. We demonstrate in particular that preparing the initial state in a coherent superposition of bound states leads to a harmonic spectrum with distinct plateaus with different conversion efficiencies. We show how this scheme may provide a way of controlling the coherent output that is produced in an experiment. ͓S1050-2947͑96͒03611-6͔
Journal of Physics A: Mathematical and General, 1992
The authors formulate a method for estimating the critical conditions for storage of sets of data... more The authors formulate a method for estimating the critical conditions for storage of sets of data in neural network memory. This variational method is based on random matrix theory and calculating the average spectrum of a matrix, whose elements are given by overlaps of the stored patterns. Several generic cases of random overlap matrices are considered. They investigate the cases of simply uncorrelated random patterns and 'spatially' and 'semantically' correlated ones. They obtain bounds of the critical curve in the control parameters space, which determine the stability of the stored data sets.
The four classes of axioms that define quantum mechanics are the class describing the state of a ... more The four classes of axioms that define quantum mechanics are the class describing the state of a physical system (the ``static'' description), the measurement axioms, the axiom for states of indistinguishable particles, and the axiom stating that the dynamics must be unitary. The second law of thermodynamics states that disorder of a physical system, as quantified by its von Neumann entropy, is preserved in reversible processes. We show that assuming the static description of quantum mechanics, the unitarity of the dynamics follows from the second law of thermodynamics.
Annalen der Physik, 2012
We present theoretical studies of high-order harmonic generation (HHG) in rare gases driven by pl... more We present theoretical studies of high-order harmonic generation (HHG) in rare gases driven by plasmonic field enhancement. This kind of fields appears when plasmonic nanostructures are illuminated by an intense few-cycle laser and have a particular spatial dependency, depending on the geometrical shape of the nanostructure. We demonstrate that the strong nonhomogeneous character of the laser enhanced field plays an important role in the HHG process and significantly extends the harmonic cutoff. Our models are based on numerical solution of the time dependent Schrödinger equation (TDSE) and supported by classical and semiclassical calculations.
Journal of Physics A: Mathematical and Theoretical, 2011
Entanglement witnesses (EWs) constitute one of the most important entanglement detectors in quant... more Entanglement witnesses (EWs) constitute one of the most important entanglement detectors in quantum systems. Nevertheless, their complete characterization, in particular with respect to the notion of optimality, is still missing, even in the decomposable case. Here we show that for any qubit-qunit decomposable EW (DEW) W the three statements are equivalent: (i) the set of product vectors obeying e, f |W |e, f = 0 spans the corresponding Hilbert space, (ii) W is optimal, (iii) W = Q Γ with Q denoting a positive operator supported on a completely entangled subspace (CES) and Γ standing for the partial transposition. While, implications (i) ⇒ (ii) and (ii) ⇒ (iii) are known, here we prove that (iii) implies (i). This is a consequence of a more general fact saying that product vectors orthogonal to any CES in 2 ⊗ n span after partial conjugation the whole space. On the other hand, already in the case of 3 ⊗ 3 Hilbert space, there exist DEWs for which (iii) does not imply (i). Consequently, either (i) does not imply (ii), or (ii) does not imply (iii), and the above transparent characterization obeyed by qubit-qunit DEWs, does not hold in general.
Journal of Physics A: Mathematical and Theoretical, 2014
In 2008, the conjecture that structural physical approximations to optimal entanglement witnesses... more In 2008, the conjecture that structural physical approximations to optimal entanglement witnesses are separable states (in general unnormalized) was posed. In an attempt to disprove it, in (Ha K-C and Kye S-H, Separable states with unique decompositions, arXiv:1210.1088v3), Ha and Kye proposed a decomposable entanglement witness whose SPA is entangled and argued that it is optimal. In this note, which is based on a comment to the latter work (Augusiak et al, Comment on "Separable states with unique decompositions", arXiv:1304.2040v1), we show, both analytically and numerically, that this entanglement witness is not optimal, and as such it is not a counterexample to the conjecture. To this end, we make use of a method for checking optimality of entanglement witnesses developed already in (Lewenstein et al 2000 Phys. Rev. A 62 052310), however, hardly exploited so far in the literature.
Optics Communications, 2010
We study extremality in various sets of states that have positive partial transposes. One of the ... more We study extremality in various sets of states that have positive partial transposes. One of the tools we use for this purpose is the recently formulated criterion allowing to judge if a given state is extremal in the set of PPT states. First we investigate qubit-ququart states and show that the only candidates for extremal PPT entangled states (PPTES) have ranks of the state and its partial transposition (5, 5) or (5, 6) (equivalently (6, 5)). Then, examples of extremal states of (5, 5) type and the so-called edge states of type (5, 6) are provided. We also make an attempt to explore the set of PPT states with ranks (5, 6). Finally, we discuss what are the possible configurations of ranks of density matrices and their respective partial transposition in general three-qubit and four-qubit symmetric states for which there may exist extremal entangled PPT states. For instance in the first case we show that the only possibilities are (4, 4, 4) and (4, 4, 5).
Physical Review A, 1982
Equations of motion for a sample filled with totally inverted two-level atoms coupled to one-dime... more Equations of motion for a sample filled with totally inverted two-level atoms coupled to one-dimensional radiation field are solved in the linear regime without the slowlyvarying-envelope approximation. The comparison with known results neg. ecting the coupling between leftand right-going waves is made.
Numerical simulations show that laser cooling of fermions on the repulsive side of the Feshbach r... more Numerical simulations show that laser cooling of fermions on the repulsive side of the Feshbach resonance can sympathetically cool molecules well below their condensation temperature.