运用量子约束动力学对具有耗散的量子位的追踪控制

在有限温度环境内，量子约束动力学及其追踪控制可使退相干系统的相干性稳定一段时间.约束方程产生的控制场能够按量子比特的动力学状态进行控制(量子动力学轨道的反馈控制)；依靠量子比特的这种反馈效应，可使量子位稳定在设定的时间内.同时，在量子位的稳定方面，温度扮演一种消极的角色. 关键词： 量子约束动力学 耗散量子位的控制 追踪控制 量子比特的反馈效应     

Mixing of electronic states in molybdenum complexes involved in nitrogen activation

The mechanism for nitrogen activation by molybdenum complexes is a complicated one, involving as it does the coupling of a quartet molybdenum reactant with a singlet nitrogen molecule, passing via a series of quartet and doublet encounter complexes to a triplet intermediate, with the subsequent spin crossing to the singlet surface which then leads via a singlet transition state to the final pair of singlet products. We have investigated in detail a variety of levels of theory to describe the crossing of these electronic surfaces and have calculated both lower-bound and actual minimum energy crossing points for the key spin inversion processes.     

Spin Polarization and Spin‐Flip Through Phosphorene Superlattice

The spin‐dependent transport properties, including spin polarization and spin‐flip for phosphorene superlattice in the presence of an extrinsic Rashba spin‐orbit interaction (RSOI) based on the transfer matrix method, are studied. The results show that the number of barriers in the superlattice structure plays a dominant role in output spin polarization, which can be used in designing optimized spintronic devices. In addition, by controlling on the Rashba strength, an incident spin‐up electron can be transmitted as a spin‐down electron. Also, it enables to convert the unpolarized incident electronic beam (with zero spin polarization) into an arbitrary output spin polarization, which plays a significant role in qubit circuits.     

Efficient implementation of restricted active space configuration interaction with the hole and particle approximation

The restricted active space configuration interaction (RASCI) formalism with the hole and particle truncation of the wavefunction, that is, RASCI(h,p), holds very nice properties such as balanced treatment of ground and low‐lying excited states, spin‐completeness, large flexibility of the wavefunction, and moderate computational cost. In this article, I present a new implementation of the RASCI(h,p) method using a general algorithm based on the integral‐driven approach. The new implementation allows to choose any electronic configuration as the single reference in combination with an excitation operator with any number of ionization, electron attachment, or spin‐flip (SF) excitations. The applicability and good performance of the new computational code is tested in the ground state calculation of water molecule with increasingly large active spaces and up to the full‐CI limit, the calculation of all‐trans linear polyenes with variable number of SF excitations, and the low‐lying states of fluorine molecule with a double‐ionization potential operator. © 2012 Wiley Periodicals, Inc.     

Codimension-4 resonant homoclinic bifurcations with orbit flips and inclination flips

The paper studies a codimension-4 resonant homoclinic bifurcation with one orbit flip and two inclination flips, where the resonance takes place in the tangent direction of homoclinic orbit.Local active coordinate system is introduced to construct the Poincar′e returning map, and also the associated successor functions. We prove the existence of the saddle-node bifurcation, the perioddoubling bifurcation and the homoclinic-doubling bifurcation, and also locate the corresponding 1-periodic orbit, 1-homoclinic orbit, double periodic orbits and some 2n-homoclinic orbits.     

The photoisomerization of 11‐cis‐retinal protonated schiff base in gas phase: Insight from spin‐flip density functional theory

This extensive theoretical study employed the spin‐flip density functional theory (SFDFT) method to investigate the photoisomerization of 11‐cis‐retinal protonated Schiff base (PSB11) and its minimal model tZt‐penta‐3,5‐dieniminium cation (PSB3). Our calculated results indicate that SFDFT can perform very well in describing the ground‐ and excited‐state geometries of PSB3 and PSB11. We located the conical intersection (CI) point and constructed the photoisomerization reaction path of PSB3 and PSB11 by using the SFDFT method. To further verify the SFDFT results, we computed the energy profiles along the constructed linearly interpolated internal coordinate (LIIC) pathways by using high‐level theoretical methods, such as the EOM‐CCSD, CR‐EOM‐CCSD(T), CASPT2, NEVPT2, and XMCQDPT2 methods. The SFDFT method predicts that the photoisomerization of PSB3 is barrierless, in accordance with previous complete‐active‐space self‐consistent‐field (CASSCF) results. However, an energy barrier is predicted along the LIIC pathways of PSB11. This finding is different from previous CASSCF results and may indicate that the photoisomerization of PSB11 in gas phase is similar to that in solution. However, the higher spin contamination of the SFDFT method in the vicinity of the CI point caused the located CI geometry to deviate from that of the real CI. In addition, the LIIC pathways are only approximations to the minimum energy path (MEP). Thus, further experimental and theoretical studies are needed to verify the existence of an energy barrier along the photoisomerization reaction path of PSB11 in gas phase. © 2013 Wiley Periodicals, Inc.     

Theoretical investigations of spin-orbit coupling and intersystem crossing in reaction carbon dioxide activated by [Re(CO)2]+

In order to further explore the detailed reaction mechanism of carbon dioxide activated by [Re(CO)₂]⁺ complex, CCSD(T) methods was performed to determine related potential energy surface (PES). Crossing point is determined by using a partially optimized method. The result shows that larger spin-orbital coupling (155.37 cm⁻¹) and intersystem crossing probabilities in spin-forbidden region causes the electron to spin flip at the minimum energy crossing point and access to the lower singlet PES. Nonadiabatic rate constant k is estimated to be quite rapid, so transition state (¹TS1) is rate-controlled steps. In addition, the electronic structure of oxygen-atom transfer process is further analyzed by localized molecular orbital and Mayer bond order. The analysis finds that the form of main bonding orbital is the electron contribution from the p(O) in CO₂ to the empty d(Re) orbital.     

A Concise Method to Predict the Mean Dynamic Pressure on a Plunge Pool Slab

Hydrodynamic pressure exerted on a plunge pool slab by jet impingement is of high interest in high dam projects. The present study experimentally investigated the characteristics of pressure induced by a jet through a constant width flip bucket (CFB) and a slit flip bucket (SFB). A pressurized plane pipe was employed in the flume experiments to control the inlet velocities in the flip buckets. A concise method is proposed to predict the mean dynamic pressure field. Its implementation is summarized as follows: First, the position of the pressure field is determined by the trajectories of free jets, and to calculate its trajectories, an equation based on parabolic trajectory theory is used; second, the maximum mean dynamic pressure is obtained through dimensional analysis, and then the pressure field is established by applying the law of Gaussian distribution. Those steps are integrated into a concise computing procedure by using some easy-to-obtain parameters. Some key parameters, such as takeoff velocity coefficient, takeoff angle coefficient, and the parameter k2, are also investigated in this paper. The formulas of these coefficients are obtained by fitting the experimental data. Using the proposed method, the easy-to-obtain geometric parameters and initial hydraulic conditions can be used to calculate the maximum mean dynamic pressure on the slab. A comparison between experimental data and calculated results confirmed the practicability of this model. These research results provide a reference for hydraulic applications.     

A Classical Formulation of Quantum Theory?

We explore a particular way of reformulating quantum theory in classical terms, starting with phase space rather than Hilbert space, and with actual probability distributions rather than quasiprobabilities. The classical picture we start with is epistemically restricted, in the spirit of a model introduced by Spekkens. We obtain quantum theory only by combining a collection of restricted classical pictures. Our main challenge in this paper is to find a simple way of characterizing the allowed sets of classical pictures. We present one promising approach to this problem and show how it works out for the case of a single qubit.     

亚稳态分子间复合物反应机理研究

亚稳态分子间复合物（metastable intermolecular composite,MIC）由于具有超高反应燃烧速率及能量释放速率、高体积能量密度、低扩散距离和绿色环保等优点,在微型含能器件、火箭推进剂和绿色火工药剂等军用领域展现了很好的应用潜力。其反应机制与传统的含能材料不同,且具有超高速反应的瞬时性及复杂性,对其反应机理仍然缺乏清晰的认识,这限制了其应用研究的进展。本文对近年来亚稳态分子间复合物的反应机理研究进行综述,重点讨论具有代表性的“金属-氧翻转机理”和“预点火-熔结机理”。对于MIC材料的反应机理研究,本文主要从实验研究、理论模型研究和数值模拟研究三个方面进行分析。改性MIC材料是对材料性能进行调控的重要手段,是目前及未来的重要发展趋势之一,在论文最后对其反应机理做了重点叙述。通过对当前研究现状的归纳与分析,给出了当前的重要研究成果以及研究中出现的问题,并对未来的研究发展趋势进行了展望。