Papers by Wieslaw Leonski
Einstein-Podolsky-Rosen steering and squeezing effect in system two coupled nonlinear oscillators
We discuss a system consisting of two coupled nonlinear Kerr-like oscillators. For such a model, ... more We discuss a system consisting of two coupled nonlinear Kerr-like oscillators. For such a model, we study the time-evolution of the steering parameter and the normally ordered variances of the quadratures operators. We discuss the relationships between the generation of steerable and squeezed states.
Acta Physica Polonica A
The influence of the PT-symmetry breaking on the chaotic properties of the coupled magnetic pendu... more The influence of the PT-symmetry breaking on the chaotic properties of the coupled magnetic pendulums is investigated. The PT-symmetric system is described by the classical approach using coupled second-order nonlinear differential equations. Using the damping coefficient A as the control parameter for the PT-symmetry and evaluating the two-dimensional basin plot of the pendulum's motion, the fractal of measure for unbroken PT-symmetry is calculated to be D f 2 and changes to D f 1.25 for broken symmetry.
Entanglement generation in a system of continuously excited anharmonic quantum oscillators
22nd Polish-Slovak-Czech Optical Conference on Wave and Quantum Aspects of Contemporary Optics
Symmetry
We consider two PT-symmetric models, consisting of two or three single-mode cavities. In both mod... more We consider two PT-symmetric models, consisting of two or three single-mode cavities. In both models, the cavities are coupled to each other by linear interactions, forming a linear chain. Additionally, the first and last of such cavities interact with an environment. Since the models are PT-symmetric, they are described by non-Hermitian Hamiltonians that, for a specific range of system parameters, possess real eigenvalues. We show that in the models considered in the article, the steering generation process strongly depends on the coupling strengths and rates of the gains/losses in energy. Moreover, we find the values of parameters describing the system for which the steering appears.
Above-threshold Ionization Photoelectron Spectrum Induced by a Train of Ultra-short Laser Pulses
Journal of Modern Optics, 1992
We discuss an atomic system comprising a single discrete, ground level and two orthogonal continu... more We discuss an atomic system comprising a single discrete, ground level and two orthogonal continua. We assume that the continua are structured m we discuss two cases: that of Lorentzian continua, and the case of Gaussian structures. Our system is irradiated by an external laser field in the form of a train of ultra-short pulses. The analytic formulas for long-time
Solitary waves in an elastic rod: analytical solutions
18th Czech-Polish-Slovak Optical Conference on Wave and Quantum Aspects of Contemporary Optics, 2012
In this paper we consider a generalized double dispersion equation of Porubov’s type4,5. which de... more In this paper we consider a generalized double dispersion equation of Porubov’s type4,5. which describes the propagation of the longitudinal strain waves in the rod. By analogy with the optical case2, the higher orders of nonlinearity have been included which leads to an interesting class of traveling solitary waves for both cases: without cubic nonlinearity and with its presence. The F-expansion method described in3 has been used. As a byproduct, we obtain the results given previously by other authors4,5. It will be shown that our analytical solutions describe very well the results obtained by numerical simulations6.
Quantum Laser Field Effect on the Photoelectron Spectrum for Auto-ionizing Systems
Journal of Modern Optics, 1990
... The atomic system under discussion is the same as that of Rzaiewski and Eberly [3]. The very ... more ... The atomic system under discussion is the same as that of Rzaiewski and Eberly [3]. The very important difference between our system and that used in [3] 0950-0340190 $3.00 {(l 1990 Taylor & Francis Ltd Page 2. ... Quantum laser field effect 1 92 5 Radmore and Knight [12]. ...
Physics Letters A, 2009
We deal with a system comprising a nonlinear (Kerr-like) oscillator excited by a series of ultra-... more We deal with a system comprising a nonlinear (Kerr-like) oscillator excited by a series of ultra-short external pulses. We introduce the fidelity-based entropic parameter that can be used as an indicator of quantum chaos. Moreover, we propose to use the fidelity-like parameter comprising the information about the mean number of photons in the system. We shall concentrate on the long-time behaviour of the parameters discussed, showing that for deep chaos cases the quantum fidelities behave chaotically in the classical sense despite their strictly quantum character.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Chaos: An Interdisciplinary Journal of Nonlinear Science, 2018
Journal of Physics B: Atomic, Molecular and Optical Physics, 2015
Two auto-ionization systems in a stationary optical field mutually interacting via the dipole-dip... more Two auto-ionization systems in a stationary optical field mutually interacting via the dipole-dipole interaction are considered. Their evolution is analytically found. Joint spectra of two ionized electrons are analyzed in detail in the long-time limit for comparable strengths of direct and indirect ionization paths as well as the dominating indirect ionization path. Entanglement in the state of two ionized electrons is quantified using the density of quadratic negativity. Suitable conditions for obtaining highly entangled states are discussed.
Entropy, 2022
We consider a family of states describing three-qubit systems. We derived formulas showing the re... more We consider a family of states describing three-qubit systems. We derived formulas showing the relations between linear entropy and measures of coherence such as degree of coherence, first- and second-order correlation functions. We show that qubit–qubit states are strongly entangled when linear entropy reaches some range of values. For such states, we derived the conditions determining boundary values of linear entropy parametrized by measures of coherence.
Kerr-type nonlinear quantum oscillator: quantum correlations, chaotic, and regular dynamics
We propose the second-order correlation function g(2) as an indicator of quantum chaotic evolutio... more We propose the second-order correlation function g(2) as an indicator of quantum chaotic evolution. We discuss a nonlinear Kerr-like oscillator's system excited by a series of ultra-short coherent pulses. For such model, we study the time-evolution of the function g(2) for various values of the strength of excitation which corresponds to the regular and chaotic behaviors of the classical counterpart of the Kerr-like quantum system.
Photonics, 2021
We consider a quantum nonlinear Kerr-like oscillator externally pumped by a series of ultrashort ... more We consider a quantum nonlinear Kerr-like oscillator externally pumped by a series of ultrashort coherent pulses to analyze the quantum time-correlations appearing while the system evolves. For that purpose, we examine the violation of the Leggett–Garg inequality. We show how the character of such correlations changes when the system’s dynamics correspond to the regular and chaotic regions of its classical counterpart.
Journal of Physical Studies, 2011
We discuss a system of the Kerr-like quantum nonlinear oscillator excited by a series of ultrasho... more We discuss a system of the Kerr-like quantum nonlinear oscillator excited by a series of ultrashort external pulses. These coherent excitations, along with the nonlinearity involved in the system, can lead to the quantum chaotic behaviour. For that model, we calculate the fidelities of the wave function which describe the system's dynamics. We show that such defined fidelity and its decay rate can be applied as an indicator of the quantum chaotic behaviour appearance. We also discuss the problem of how the initial distance between the two close wave functions can influence the fidelity changes.
Chaos Theory, Mar 28, 2018
Here, we present a brief insight into some current methods allowing for the detection of quantum ... more Here, we present a brief insight into some current methods allowing for the detection of quantum chaos phenomena. In particular, we show examples of proposals of the parameters which could be applied as indicators of quantum-chaotic behavior and already were presented in the literature. We concentrate here on the quantum fidelity and the fidelity-like functions, defined for the wave functions describing system's evolution. The definition of the fidelity-like parameter also involves the operator of the mean number of photons/phonons. Discussing such parameter, we show here how it is possible to take into account in the discussion of quantum-chaotic systems simultaneously the behavior of the divergence of wave functions and the energy of the system represented by the mean number of photons/phonons. Next, we discuss entropy-type parameter which can also be a good candidate for the indicators of quantum chaos' phenomena. We show the ability of all considered here parameters to be witnesses of quantum-chaotic behavior for the systems of the quantum nonlinear Kerr-like oscillator-the classical counterpart of such system can exhibit chaotic evolution in its canonical form.
Journal of the Optical Society of America B, 2018
We discuss the electromagnetically induced transparency (EIT) phenomenon for a model in which a s... more We discuss the electromagnetically induced transparency (EIT) phenomenon for a model in which a structured continuum is described by a so-called double Fano structure; instead of one autoionizing (AI) state, two such states are embedded in a flat continuum. Such a Fano structure is the upper level of a Λ-like three-level system and is coupled to two lower ones by an external laser field involving δ-correlated, Gaussian, Markov process (white noise), simulating realistic conditions of the experiment. For such a system we derived and solved a set of coupled stochastic integrodifferential equations in the stationary regime, obtaining exact formulas determining the electric susceptibility of the system. Dispersion and absorption spectra of the medium susceptibility were calculated and compared with those already discussed in the literature. We have shown that the presence of an additional AI level considerably changes the structure of transparency windows and how noisy excitation influences the EIT processes.
Physical Review A, 2019
A two-mode optical parity-time (PT) symmetric system, with gain and damping, described by a quant... more A two-mode optical parity-time (PT) symmetric system, with gain and damping, described by a quantum quadratic Hamiltonian with additional small Kerr-like nonlinear terms, is analyzed from the point of view of nonclassical-light generation. Two kinds of stationary states with different types of (in)stability are revealed. Properties of one of these are related to the presence of semiclassical exceptional points, i.e., exotic degeneracies of the non-Hermitian Hamiltonian describing the studied system without quantum jumps. The evolution of the logarithmic negativity, principal squeezing variances, and sub-shot-noise photon-number correlations, considered as entanglement and nonclassicality quantifiers, is analyzed in the approximation of linear-operator corrections to the classical solution. Suitable conditions for nonclassical-light generation are identified in the oscillatory regime, especially at and around exceptional points that considerably enhance the nonlinear interaction and, thus, the non-classicality of the generated light. The role of quantum fluctuations, inevitably accompanying attenuation and amplification in the evolution of quantum states, is elucidated. The evolution of the system is analyzed for different initial conditions.
Acta Physica Polonica A, 2019
We discuss a model consisting of two nonlinear oscillators, where a train of periodic ultrashort ... more We discuss a model consisting of two nonlinear oscillators, where a train of periodic ultrashort laser pulses excites one of them. We show that the system can behave as a two-qubit system and produce maximally entangled Bell states. Such generation is more effective than that for the system with continuous excitation.
Nonlinear Dynamics, 2019
We discuss a model of a short Bose-Hubbard dimer involving two anharmonic quantum oscillators mut... more We discuss a model of a short Bose-Hubbard dimer involving two anharmonic quantum oscillators mutually coupled with the use of the linear interaction and additionally driven by a series of ultra-short external pulses. We show that under some conditions the system behaves as a two-qubit one, and contrary to its continuously driven counterpart can be a source of maximally entangled states (MES). We discuss the cases when the system is excited only in one mode and in both ones, and additionally when the cross-Kerr-type interaction is present or omitted. We show that the generation of maximally (or almost maximally) entangled states depends on the time of free evolution of oscillators and hence, the proper steer
Uploads
Papers by Wieslaw Leonski