We theoretically investigate high-order harmonic generation by employing strong-field approximation （SFA） and present a new approach to the extension of the high-order harmonic cutoff frequency via an exploration of the dependence of high-order harmonic generation on the waveform of laser fields. The dependence is investigated via detailed analysis of the classical trajectories of the ionized electron moving in the continuum in the velocity-position plane. The classical trajectory consists of three sections （Acceleration Away, Deceleration Away, and Acceleration Back）, and their relationship with the electron recollision energy is investigated. The analysis of classical trajectories indicates that, besides the final （Acceleration Back） section, the electron recollision energy also relies on the previous two sections. We simultaneously optimize the waveform in all three sections to increase the electron recollision energy, and an extension of the cutoff frequency up to Ip ＋ 20.26Up is presented with a theoretically synthesized waveform of the laser field.
We provide a fast iteration method to calculate the ion equilibrium temperature in an ultracold neutral plasma(UNP).The temperature as functions of electron initial temperature and ion density is obtained and compared with the recent UNP experimental data.The theoretical predictions agree with the experimental results very well.The calculated ion equilibrium temperature by this method can be applied to study the UNP expansion process more effectively.
LI Jin-XingCAO Ming-TaoHAN LiangQI Yue-RongZHANG Shou-GangGAO HongLI Fu-LiT.C.Killian
We consider a qubit symmetrically and transversely coupled to an XY spin chain with Dzyaloshinsky-Moriya（DM） interaction in the presence of a transverse magnetic field.An analytical expression for the geometric phase of the qubit is obtained in the weak coupling limit.We find that the modification of the geometrical phase induced by the spin chain environment is greatly enhanced by DM interaction in the weak coupling limit around the quantum phase transition point of the spin chain.
The correlation dynamics are investigated for various bi-partitions of a composite quantum system consisting of two qubits and two independent and non-identical noisy environments. The two qubits have no direct interaction with each other and locally interact with their environments. Classical and quantum correlations including the entanglement are initially prepared only between the two qubits. We find that contrary to the identical noisy environment case, the quantum correlation transfer direction can be controlled by combining different noisy environments. The amplitude- damping environment determines whether there exists the entanglement transfer among bi-partitions of the system. When one qubit is coupled to an amplitude-damping environment and the other one to a bit-flip one, we find a very interesting result that all the quantum and the classical correlations, and even the entanglement, originally existing between the qubits, can be completely transferred without any loss to the qubit coupled to the bit-flit environment and the amplitude-damping environment. We also notice that it is possible to distinguish the quantum correlation from the classical correlation and the entanglement by combining different noisy environments.
We provide a theoretical study to calculate the spin-dependent optical lattice with rubidium Bose-Einstein condensation(BEC)in a steady magnetic field.The optical dipole potential variation at different Zeeman levels are obtained.We also show that atoms can be transported in three dimensions by changing the polarization of the trapping field.An explanation of this transportation process in an atomic coordinate is presented.
CAO Ming-TaoHAN LiangQI Yue-RongZHANG Shou-GangGAO HongLI Fu-Li
We present an experimental and theoretical study of self-rotation of optical polarization in a rubidium vapor.The atomic vapor is placed in a magnetic shielding cavity to suppress the Faraday rotation effect.In our experiment,Doppler-free spectroscopy configuration is used,and F = 2 → F ＇ = 3 transition of 87Rb D2 line is chosen.We observe self-rotation of optical polarization effect at different pump light ellipticities.A theoretical analysis is then provided based on the experimental conditions.Theoretical simulation and experimental results are in good agreement.
The fourier-transform patterns of an object are usually observed in the far-field region or obtained in the near-field region with the help of lenses. Here we propose and experimentally demonstrate a scheme of Fourier-transform patterns in the Fresnel diffraction region with thermal light. In this scheme, neither a lens nor a bearnsplitter is used, and only one single charge coupled device （CCD） is employed. It means that dividing one beam out of a light source into signal and reference beams is not as necessary as the one done by the use of a beamsplitter in usual ghost interference experiments. Moreover, the coincidence measurement of two point detectors is not necessary and data recorded on a single CCD are sufficient for reconstructing the ghost diffraction patterns. The feature of the scheme promises a great potential application in the fields of X-ray and neutron diffraction imaging processes.
Energy transfer processes between two aggregates in a coupled chromophoric-pigment （protein） system are studied via the standard master equation approach. Each pigment of the two aggregates is modeled as a two-level system. The excitation energy is assumed to be transferred from the donor aggregate to the acceptor aggregate. The model can be used to theoretically simulate many aspects of light-harvesting complexes （LHCs）. By applying the real bio-parameters of photosynthesis, we numerically investigate the efficiency of energy transfer （EET） between the two aggregates in terms of some factors, e.g., the initial coherence of the donor aggregate, the coupling strengthes between the two aggregates and between different pigments, and the effects of noise from the environment. Our results provide evidence for that the actual numbers of pigments in the chromophoric tings of LHCs should be the optimum parameters for a high EET. We also give a detailed analysis of the effects of noise on the EET.
In this paper, the effects of quantum and classical correlations on the excitation energy transfer in a three-quasi- spin-pigment system are investigated. We first study the dependence of the energy transfer efficiency on various initial correlations of the donor pigments, and find that the initial concurrence is crucial to the efficiency no matter whether the initial states are pure or mixed. We then demonstrate the dynamics of correlations of the system and observe the appearance of sudden death of quantum correlations in the donor pigments. The relation between the energy transfer efficiency and the dynamics of correlations in the donor pigments is also discussed.
