Quantum path control using attosecond pulse trains via UV-assisted resonance enhance ionization

We theoretically investigate the quantum path selection in an ultraviolet （UV）-assisted near-infrared field with an UV energy below the ionization threshold. By calculating the ionization probability with different assistant UV frequencies, we find that a resonance-enhanced ionization peak emerges in the region Euv 〈 Ip, where Euv is the photon energy and Ip is the ionization energy. With an attosecond pulse train （APT） centered in the resonance region, we show that the short quantum path can be well selected in the continuum case. By performing the electron trajectory analysis, we have further explained the physical mechanism of the quantum path selection. Moreover, we also demonstrate that in the resonance region, the harmonic emission from the selected paths is more efficient than that with the APT energy above the ionization threshold.

Role of quantum paths in generation of attosecond pulses

We investigate the role of core potential in high ionization potential systems on high harmonic generation (HHG) spectra and obtain attosecond pulses. In our scheme, we use a standard soft core potential to model high ionization potential systems and irradiated these systems with fixed laser parameters. We observe the role of these systems on all the three steps involved in HHG process including ionization, propagation and recombination. In our study, the results illustrate that for high ionization potential systems, the HHG process is more sensitive to the ionization probability compared to the recombination amplitude. We also observe that due to the stronger core potential, small oscillations of the electrons during the propagation do not contribute to the HHG spectrum, which implies the dominance of only long quantum paths in the HHG spectrum. Our results, for attosecond pulse generation, show that long quantum path electrons are responsible for the supercontinuum region near the cutoff, which is suitable for the extraction of a single attosecond pulse in this region.

Quantum Path Selection and Isolated-Attosecond-Pulse Generation of H2+ with an Intense Laser Pulse and a Static Field

We theoretically investigate the high-order-harmonic generation from the H2^＋ molecular ion exposed to the combi- nation of an intense trapezoidal laser and a static field. The results show that the harmonic spectrum is obviously extended and the short quantum path is selected to contribute to the spectrum, because the corresponding long path is seriously suppressed. Then the combined Coulomb and laser field potentials and the time-dependent electron wave packet distributions are applied to illustrate the physical mechanism of high-order harmonic gen- eration. Finally, by adjusting the intensity of the static field and superposing a properly selected range of the HHG spectrum, a 90-as isolated attosecond pulse is straightforwardly obtained.

Quantum Path Predictability for an Electronic Mach-Zehnder Interferometer in Presence of Environment Induced Decoherence and Quantum Erasing Process

In this paper, we have estimated the temperature dependent path predictability for an electronic Mach-Zehnder interferometer. The increment of path predictability can directly be associated with stronger decoherence process. We have also theoretically predicted that placing two detectors in both the paths, which are at the same equilibrium temperature with the system, erases all the memory of path information and hence acts like a quantum eraser.

Atom interferometers with weak-measurement path detectors and their quantum mechanical analysis

According to the orthodox interpretation of quantum physics, wave-particle duality(WPD) is the intrinsic property of all massive microscopic particles. All gedanken or realistic experiments based on atom interferometers(AI) have so far upheld the principle of WPD, either by the mechanism of the Heisenberg’s position-momentum uncertainty relation or by quantum entanglement. In this paper, we propose and make a systematic quantum mechanical analysis of several schemes of weak-measurement atom interferometer(WM-AI) and compare them with the historical schemes of strongmeasurement atom interferometer(SM-AI), such as Einstein’s recoiling slit and Feynman’s light microscope. As the critical part of these WM-AI setups, a weak-measurement path detector(WM-PD) deliberately interacting with the atomic internal electronic quantum states is designed and used to probe the which-path information of the atom, while only inducing negligible perturbation of the atomic center-of-mass motion. Another instrument that is used to directly interact with the atomic center-of-mass while being insensitive to the internal electronic quantum states is used to monitor the atomic centerof-mass interference pattern. Two typical schemes of WM-PD are considered. The first is the micromaser-cavity path detector, which allows us to probe the spontaneously emitted microwave photon from the incoming Rydberg atom in its excited electronic state and record unanimously the which-path information of the atom. The second is the optical-lattice Bragg-grating path detector, which can split the incoming atom beam into two different directions as determined by the internal electronic state and thus encode the which-path information of the atom into the internal states of the atom. We have used standard quantum mechanics to analyze the evolution of the atomic center-of-mass and internal electronic state wave function by directly solving Schr¨odinger’s equation for the composite atom-electron-photon system in these WM-AIs. We have also compared our analysis with the theoretical and experimental studies that have been presented in the previous literature. The results show that the two sets of instruments can work separately, collectively, and without mutual exclusion to enable simultaneous observation of both wave and particle nature of the atoms to a much higher level than the historical SM-AIs, while avoiding degradation from Heisenberg’s uncertainty relation and quantum entanglement. We have further investigated the space–time evolution of the internal electronic quantum state, as well as the combined atom–detector system and identified the microscopic origin and role of quantum entanglement, as emphasized in numerous previous studies. Based on these physics insights and theoretical analyses, we have proposed several new WM-AI schemes that can help to elucidate the puzzling physics of the WPD of the atoms. The principle of WM-AI scheme and quantum mechanical analyses made in this work can be directly extended to examine the principle of WPD for other massive particles.

Fuzzification of Feynman Path Integral and Its Effect on Field Theory and Quantum Gravity—Reformation and Redevelopment of Quantum Theory

The quantum probability theory of fuzzy event is suggested by using the idea and method of fuzzy mathematics, giving the form of fuzzy event path integral, membership degree amplitude, fuzzy field function, Green function, physical quantity and fuzzy diagram. This theory reforms quantum mechanics, making the later become its special case. This theory breaks unitarity, gauge invariance, probability conservation and information conservation, making these principles become approximate ones under certain conditions. This new theory, which needs no renormalization and can naturally give meaningful results which are in accordance with the experiments, is the proper theory to describe microscopic high-speed phenomenon, whereas quantum mechanics is only a proper theory to describe microscopic low-speed phenomenon. This theory is not divergent under the condition of there being no renormalization and infinitely many offsetting terms, thereby it can become the theoretical framework required for the quantization of gravity.

利用非均匀正交激光选择谐波发射短量子路径

理论研究了谐波发射的量子路径在非均匀正交激光场下的调控机制.结果表明,在适当的双色激光偏振角和非均匀参数的组合下,不仅谐波截止能量有明显增大;谐波发射的短量子路径可以被单独选择出来对谐波连续区起到贡献作用.并且,该方案在长脉宽激光下依然适用.最后,利用谐波连续区可以获得脉宽在50 as的孤立阿秒脉冲.

Optimization of extreme ultraviolet vortex beam based on high harmonic generation

In high harmonic generation(HHG),Laguerre–Gaussian(LG) beams are used to generate extreme ultraviolet(XUV)vortices with well-defined orbital angular momentum(OAM),which have potential applications in fields such as microscopy and spectroscopy.An experimental study on the HHG driven by vortex and Gaussian beams is conducted in this work.It is found that the intensity of vortex harmonics is positively correlated with the laser energy and gas pressure.The structure and intensity distribution of the vortex harmonics exhibit significant dependence on the relative position between the gas jet and the laser focus.The ring-like structures observed in the vortex harmonics,and the interference of quantum paths provide an explanation for the distinct structural characteristics.Moreover,by adjusting the relative position between the jet and laser focus,it is possible to discern the contributions from different quantum paths.The optimization of the HH vortex field is applicable to the XUV,which opens up a new way for exploiting the potential in optical spin or manipulating electrons by using the photon with tunable orbital angular momentum.

适用于量子混合网络的量子多路纠缠分组交换方法

适用于量子混合网络的量子多路纠缠分组交换方法,首先将需要发送的量子报文,按照集中式路由计算得出的多路径资源进行匹配分组,然后采用虚电路方式并行建立端到端量子纠缠多路径,控制消息和测量结果采用分布式路由数据报方式传送,最终通过量子远程传态完成量子信息的端到端传递。这种方法将分组交换的两种技术虚电路和数据报结合使用,同时将集中式路由和分布式路由有机结合,形成了一种新的量子多路纠缠分组传输方法。该方法提高了网络资源利用率,达到多路并行、分流和缩短量子信息传送时间的效果。

利用多周期空间非均匀啁啾场产生单个短阿秒脉冲

提出了一种直接生成单个短阿秒脉冲的有效方案.采用数值求解一维含时薛定谔方程,理论研究了多周期空间非均匀啁啾场驱动预激发氦离子的高次谐波辐射和阿秒脉冲的产生.结果表明:在空间非均匀啁啾场作用下,谐波截止可扩展至1050阶次,并且高于300阶次以上的谐波是连续的.由于连续谱来自单一量子路径的贡献,滤出连续谱上880-1120阶次的谐波,直接产生了一个脉宽为11.4 as的单个脉冲.通过增加驱动脉冲的持续时间,可获得一个脉宽短至10 as的单个脉冲.

Continuous Quantum Nondemolition Measurements of a Particle in Electromagnetic and Gravitational Fields

The detection of a particle in electromagnetic plus gravitational fields is investigated. We obtain a set of quantum nondemolition variables. The continuous measurements of these nondemolition parameters are analyzed in the framework of restricted path integral formalism. We manipulate the corresponding propagators, and deduce the probabilities associated with the possible measurement outputs.

Path integral approach to electron scattering in classical electromagnetic potential

As is known to all, the electron scattering in classical electromagnetic potential is one of the most widespread applications of quantum theory. Nevertheless, many discussions about electron scattering are based upon single-particle Schrodinger equation or Dirac equation in quantum mechanics rather than the method of quantum field theory. In this paper, by using the path integral approach of quantum field theory, we perturbatively evaluate the scattering amplitude up to the second order for the electron scattering by the classical electromagnetic potential. The results we derive are convenient to apply to all sorts of potential forms. Furthermore, by means of the obtained results, we give explicit calculations for the one-dimensional electric potential.

Phase Space Path Integral Representation for Wigner Function

Quantum interference and exchange statistical effects can affect the momentum distribution functions making them non-Maxwellian. Such effects may be important in studies of kinetic properties of matter at low temperatures and under extreme conditions. In this work we have generalized the path integral representation for Wigner function to strongly coupled three-dimensional quantum system of particles with Boltzmann and Fermi statistics. In suggested approach the explicit expression for Wigner function was obtained in harmonic approximation and Monte Carlo method allowing numerical calculation of Wigner function, distribution functions and average quantum values has been developed. As alternative more accurate single-momentum approach and related Monte Carlo method have been developed to calculation of the distribution functions of degenerate system of interacting fermions. It allows partially overcoming the well-known sign problem for degenerate Fermi systems.

Reformulation of Relativistic Quantum Field Theory Using Region-Like Idealization of the Elementary Particle

The existence of any elementary particle in universe requires the existence of some region of universe occupied by it. By taking the volume of this occupied region, the author will reformulate the relativistic quantum field theory using new 3-dimensional region-like idealization of elementary particles and hereinafter will call the total volume of all regions occupied by the elementary constituent particles of the quantum system the occupied volume. Also the author will call the set of all regions of universe filled by elementary constituent particles of the quantum system the occupied path. Always any quantum system is existed at a head of its occupied path. This path is growing by mutual filling and leaving regions of universe by its elementary constituent particles. The conservation of this elementary constituent particle requires the conservation of its occupied volume during this process. This requirement could be summarized by the following conditions: 1) the total volume of all regions of universe filled by the elementary constituent particles of the quantum system minus the total volume of all regions of universe left by these elementary constituent particles must be equal to the occupied volume of the quantum system;2) the total increase in the occupied volume of the quantum system due to the absorption of another elementary particles from outside its occupied regions minus the total decreasing in its occupied volume due to the emission of another elementary particles outside its occupied regions must be equal to the occupied volume of it. The wave-particle duality of the elementary constituent particles implied accumulation of them as the finite set of interfered waves. This accumulation of elementary constituent particles causes the absolute probabilistic nature of event of finding the elementary consistent particle in specified interfered wave, and hence the mathematical representation of this interfered wave should take into account the value of probability amplitude of finding an elementary particle inside the region occupied specified interfered wave. In quantum theory this probability amplitude corresponds to complex amplitude of the wave function of interfered wave. Also in Hilbert’s representation of the quantum theory these wave functions are representing the components of the quantum state vector. In this paper the author will develop the transformation theory of the region-like quantum state of the quantum system.

基于梯度统计变异量子遗传算法的车辆路径规划

针对传统路径规划算法收敛速度慢、稳定性差、易陷入局部极值的问题,提出一种基于梯度统计变异量子遗传算法的车辆路径规划方法.首先在依据染色体适应度值动态调整旋转角步长的基础上,引入梯度下降思想对量子旋转门调整策略进行改进;根据染色体变化趋势的统计特性,设计基于梯度统计的变异算子实现变异操作,提出基于量子位概率密度的自适应变异策略;以路径最短为指标建立车辆路径规划模型,通过仿真实验验证改进算法在车辆路径规划中的有效性,与其他优化算法相比,本文改进算法所规划路径长度更短,搜索稳定性更好,能有效控制算法陷入局部最优.

Path Integral Molecular Dynamics Simulation on Atomic Distribution in Amorphized Ice Ic

We have investigated the effects of compression and quantization on atomic distribution in ice Ic and in its compressed states at 77 K and 10 K, using the path integral molecular dynamics (PIMD) simulations over wide range of volume. It has been found that the high density amorphous ice (HDA) is attained by compression but volume range to retain ice structure is wider at 10 K than 77 K. We have discovered that quantum dispersion of atoms in ice Ic at 10 K induces non-zero probability that hydrogen-bonded H2O molecular molecules are oriented nonlinearly in the crystal structure, which was believed to contain exclusively linear orientation of hydrogen-bonded molecular pairs in this ice. It has been found that for HDA there is each non-zero probability of orientational disorder of hydrogen-bonded H2O pairs, of such uniform distribution of H atoms as observed in supercritical fluids in general, and of H atoms located at the O-O midpoint. The present PIMD simulations have revealed that these observed anomalous characteristics of atomic distribution in HDA are caused by both quantization of atoms and compression of the system.

Hamiltonian, Path Integral and BRST Formulations of the Restricted Gauge Theory of <i>QCD₂</i>

We study the Hamiltonian, path integral and Becchi-Rouet-Stora and Tyutin (BRST) formulations of the restricted gauge theory of QCD2 à la Cho et al. under appropriate gauge-fixing conditions.

路径积分传播子测量的研究进展

传播子在路径积分理论中扮演着核心角色,因此在路径积分理论可使用的多个现代量子物理领域中有重要价值.然而,由于其一直未能在实验中被直接测量,基于路径积分表述研究量子系统的实验进展受到了严重制约.最近,基于波函数直接测量方法,我们提出了传播子测量方案,并利用单光子实验首次成功实现了传播子的实验测量.此外,在这项研究中还首次演示了量子力学的最小作用量原理.该研究成功解决了路径积分实验研究中的技术难题.本文综述了此领域的研究进展,具体为简述波函数直接测量的基本概念和研究进展,并详细介绍传播子测量的理论模型、实验设计和实验结果.最后,介绍了一个重要的应用范例,即通过传播子测量实现最小作用量原理的实验演示.本文综述的传播子测量研究进展,将为今后使用该方法开展相关实验研究提供重要的参考.

基于改进量子粒子群算法的AUV路径规划研究

针对海洋环境下自主水下机器人(AUV)的路径规划问题,提出了一种基于框架四叉树的改进量子粒子群算法(QPSO),首先使用框架四叉树的方法对障碍物建模,该方法提高了建模的精度且对后续算法的效率也有极大的改进,之后设计改进的量子粒子群算法,并且结合水下环境的特殊性设计适应度函数,综合考虑航线路径长度、偏转角度以及海流影响,使得算法可以在水下环境中寻得能耗最短的解路径。最后通过仿真试验验证,相比于传统的栅格法和粒子群算法,改进量子粒子群算法的运算时间更短,收敛速度更快,其独特的适应度函数可以使AUV能更好适应水下多变的环境,且能利用海流设计能耗更小的路径,具有很大的实用价值。

Exact Quasi-Classical Asymptotic beyond Maslov Canonical Operator and Quantum Jumps Nature

Exact quasi-classical asymptotic beyond WKB-theory and beyond Maslov canonical operator to the Colombeau solutions of the n-dimensional Schrodinger equation is presented. Quantum jumps nature is considered successfully. We pointed out that an explanation of quantum jumps can be found to result from Colombeau solutions of the Schrodinger equation alone without additional postulates.