Theoretic Studies On Ionizations Of Atoms And Coherent Controls Of Two-state Quantum Systems With Intense Pulse Laser

The advent of the ultrastrong pulse laser has been a significance influence on physical ionizations and generations of ions with a very high degree of ionization.The ionizations of atom, molecular and ion,as the one topic of the important and basic studies in ultrastrong laser fields, play a necessary basic role on the study of other characters and nonlinear optics phenomena.At present,one aspect of arousing widely the interest is the coherent control of the ionization in two-color laser fields.On the other hand,quantum information can accomplish new functions which classical information cannot do and it has consequentially great scientific significance and potential value.The unique characteristic of quantum information is attracting much attention of many authors.One of the key points in the field is to find out the reasonable physics model that quantum computing can be applied and practical physics system that can be realized.The theory and experiment on the intense laser field and tow-state quantum system coherent control research will play a fundamental role for the development of quantum information science.The present thesis discusses firstly coherent controls on ionizations of atoms in two-color laser fields and improving the ionization possibility.Secondly,the coherent control of the two-color laser pulses propagating in a two-level medium is investigated. Finally,we analyze the presumable quantum information processing in the wall of cytoskeletal microtubule.The main results are showed as follows:1.The influences of two-color pulse laser fields on the ionizations of the linear multi-atom molecular ion.The one-dimensional time-dependent Schr(?)dinger equation is numerically solved with the symmetric splitting of the short-time exponential propagator and the fast Fourier transformation.The theory results show that the dependence of ionization probability on the atomic distance can be altered obviously by the laser intensity of the fundamental wave field,but unchanged with respect to the different ratios of the intensities.In addition,the continuous interaction of laser pulse can enhance molecular ionization,which,however,comes up to saturate when the interaction time reaches 75fs for the parameters adopted in this work.These results can be explained with the static-electric-field ionization model.2.The influences of intense pulse lasers on the ionizations of muon-atomμ³He in the muon-catalysed fusion.In order to reduce the muonic sticking loss in the muon-catalyed fusion,we suggest an approach about the ionizations of muon-atomμ³He produced in the muon-catalysed fusion by using the intense pulse lasers.The one-dimensional time-dependent Schr(?)dinger equation is numerically solved;based on that,we not only study the influence of different laser intensities and wavelengths on muon-atomμ³He ionizations,but also compare the influence of the one-color laser on the ionization with that of the two-color laser.Theoretic results show that the ionization probability is about 2.7 percent when the magnitudes of one-color laser intensities are from 10¹⁹ W/cm² to 10²³ W/cm²,and can increase obviously when the laser intensity reaches 3.0×10²⁴W/cm².Furthermore,the ionization probability increases with the laser intensity and wavelength,and the effective ionization of muon-atomμ³He can be finished in the continuous interaction of laser pulse.It is useful to enhance the efficiency of the muon-catalysed fusion.In addition,in the two-color laser field,the ionization probability is much more than that in the one-color laser field,but is not the straightforward sum of that in the one-color laser field.We futher find that the ionization probability ofμ³He changes along with relative phases and the ionization probability in the laser(ω_h= 3ω_f) is shown larger than that in the laser(ω_h=2ω_f)3.Two-color laser-induced evolution of quantum state in two-level quantum system. To attempt to control the quantum state of a physical system with a femtosecond two-color laser field,a model for the two-level system is analyzed,which is widely applied in the field of quantum information science.We derive the evolution equation of periodical density operator with the time;investigate the coherent control of the two-color laser pulses propagating in a two-level medium;and especially,calculate the influence of laser field with various laser parameters on the electron dynamics and the influence of continuous lasers on the qubit flip.It is shown that the electronic state can be changed up and down by choosing the appropriate laser pulses and the continuous qubit flip can be finished in the continuous interaction of laser pulse.Moreover,results show the coherent control of two-color laser pulses can substantially modify the behavior of the electronic dynamics:quicker change of two states can be produced even for small pulse duration.In addition,the oscillatory structures around the resonant frequency and the propagation features of the laser pulses depend sensitively on the relative phase of the two-color laser pulses.Finally,something related a finite life time of the upper level and the dynamics of nuclear spin-1/2 system in a strong bichromatic RF-field are discussed in brief.4.Ultrashort pulse laser-induced quantum information processing in the wall of cytoskeletal microtubules(MTs).In the MT wall,tubulin dimers can be figured as "lattice" sites similar to crystal lattices.Based on the pseudo-spin model,two different location states of the mobile electron in each dimer are developed.Accordingly,the MT wall is described as an anisotropic two-dimensional(2-D) pseudo-spin system considering a periodic triangular "lattice".Because three different "spin-spin" interactions in each cell exist periodically in the whole MT wall,the system may be shown to be an array of three types of two-pseudo-spin-state dimers.For the above-mentioned condition,the processing of quantum information is presented by using the scheme developed by Lloyd;futhermore,the four resonance frequencies of each dimer can be calculated.