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density matrix for Mesoscopic Distributed Parameter Circuits

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Communications in Theoretical Physics 2005年第3期43卷 547-550页

作者： JIYing-Hua WANGQi LUOHai-Mei LEIMin-Sheng DepartmentofPhysics JiangxiNormalUniversityNanchang330027China

Under the Born-von-Karmann periodic boundary condition, we propose a quantization scheme for non-dissipative distributed parameter circuits (i.e. a uniform periodic transmission line). We find the unitary operator for diagonalizing the Hamiltonian of the uniform periodic transmission line. The unitary operator is expressed in a coordinate representation that brings convenience to deriving the density matrix rho(q,q',beta). The quantum fluctuations of charge and current at a definite temperature have been studied. It is shown that quantum fluctuations of distributed parameter circuits, which also have distributed properties, are related to both the circuit parameters and the positions and the mode of signals and temperature T. The higher the temperature is, the stronger quantum noise the circuit exhibits.

关键词： mesoscopic distributed parameter circuits density matrix quantum fluctuations

No-relationship Between Impossibility of Faster-Than-Light Quantum Communication and Distinction of Ensembles with the Same density matrix

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Communications in Theoretical Physics 2005年第4X期44卷 622-624页

作者： WANG Chuan LONG Gui-Lu SUN Yang Department of Physics and Key Laboratory for Quantum Information and Measurements Tsinghua University Beijing 100084 China Key Laboratory for Atomic and Molecular NanoSciences Tsinghua University Beijing 100084 China Department of Physics University of Notre Dame Notre Dame Indiana 46556 USA

It has been claimed in the literature that impossibility of faster-than-light quantum communication has an origin of indistinguishability of ensembles with the same density matrix. We show that the two concepts are not *** argue that even with an ideal single-atom-precision measurement, it is generally impossible to produce two ensembles with exactly the same density matrix; or to produce ensembles with the same density matrix, classical communication is necessary. Hence the impossibility of faster-than-light communication does not imply the indistinguishability of ensembles with the same density matrix.

关键词： faster-than-light communication distinction of ensembles density matrix

density matrix of two interacting particles with kinetic coupling derived in bipartite entangled state representation

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Chinese Physics B 2007年第9期16卷 2544-2548页

作者： Guo Qi 郭琴 Department of Physics Shanghai Jiaotong University Shanghai 200030 China Department of Physics Jiangxi Normal University Nanchang 330022 China

A density matrix is usually obtained by solving the Bloch equation, however only a few Hamiltonians＇ density matrices can be analytically derived. The density matrix for two interacting particles with kinetic coupling is hard to derive by the usual method due to this coupling; this paper solves this problem by using the bipartite entangled state representation.

关键词： density matrix the bipartite entangled state representation kinetic coupling

Optimizing the Computation of Many-Pair density matrix in VDPC

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Journal of Applied Mathematics and Physics 2022年第7期10卷 2303-2312页

作者： Jin Li Wanli Ma Department of Physics University of Shanghai for Science and Technology Shanghai China Department of Mathematics University of Shanghai for Science and Technology Shanghai China

Recently an algorithm that acts the variational principle directly to a coherent-pair condensate (VDPC) has been proposed. This algorithm can avoid time-consuming projection while maintaining particle number conservation. Quickly computation of many-pair density matrix (MPDM) is one of the keys to improve the computational efficiency of VDPC algorithm. In this work, we propose a scheme that limits the energy range of block particles to the vicinity of the Fermi surface, which reduces the time complexity of computing the MPDM without losing physical details. The results show that by appropriately limiting the energy range, we can greatly reduce the number of matrix elements that need to be computed, and reducing the time required for the computation.

关键词： Nuclear Structure Mean-Field Theory BCS density matrix VDPC

Ultrafast Relaxation of Coherent Control Photocurrent in AlGaAs／GaAs Multi Quantum Wells

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Chinese Physics Letters 2005年第1期22卷 188-190页

作者：林位株寿倩刘鲁宁吴羽文锦辉赖天树 StateKeyLaboratoryofOptoelectronicMaterialsandTechnologies SunYat-SenUniversityGuangzhou510275

We theoretically and experimentally study the ultrafast dynamics of coherent control photocurrent in As-GaAs/GaAs multi quantum wells at room temperature. A ballistic photocurrent relaxation time of similar to200fs is deduced based on the theory of density matrix and is evidenced with the three-colour femtosecond pump-probe measurements.

关键词： GAAS SEMICONDUCTORS CURRENTS Quantum wells Relaxation time Photocurrent gallium arsenides currents density matrix Semiconductor materials

Production and detection of ultracold Cs_2 molecules via four-photon adiabatic passage

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Chinese Physics B 2014年第1期23卷 108-111页

作者：李健刘勇丛书林 School of Physics and Optoelectronic Technology Dalian University of Technology

We study theoretically how to produce and detect the ultracold ground-state Cs2 molecule from Feshbach state. Nu- merical calculations are performed by solving the quantum Liouville equation based on multilevel Bloch model. The producing efficiency reaches 55% and the detecting efficiency is 31%. The producing and detecting efficiencies are closely related to the Rabi frequencies of laser pulses. The decay of relevant electronic and vibrational states obviously reduces the producing and detecting efficiencies.

关键词： ultracold Cs2molecules Liouville equation density matrix chainwise stimulated Raman adia-batic passage (STIRAP)

A RIGOROUS DERIVATION OF THE GROSS-PITAEVSKII HIERARCHY FOR WEAKLY COUPLED TWO-DIMENSIONAL BOSONS

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Acta Mathematica Scientia 2010年第3期30卷 841-856页

作者：刘创业 Wuhan Institute of Physics and Mathematics Chinese Academy of Sciences

In this article, we consider the dynamics of N two-dimensional boson systems interacting through a pair potential N-1Va（xi -xj） where Va（x） = a^-2V（x/a）. It is well known that the Cross-Pitaevskii （GP） equation is a nonlinear SchrSdinger equation and the GP hierarchy is an infinite BBGKY hierarchy of equations so that if ut solves the GP equation, then the family of k-particle density matrices { k ut, k≥1} solves the GP hierarchy. Denote by ψN,t the solution to the N-particle Schrodinger equation. Under the assumption that a = N^-ε for 0 〈 ε 〈 3/4, we prove that as N→∞ the limit points of the k-particle density matrices of CN,t are solutions of the GP hierarchy with the coupling constant in the nonlinear term of the GP equation given by f V（x） dx.

关键词： Cross-Pitaevskii equation Boson system density matrix BBGKY hierarchy

Exploitation of symmetry in periodic Self-Consistent-Field ab initio calculations: application to large three-dimensional compounds

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Science China Chemistry 2014年第10期57卷 1418-1426页

作者： DE LA PIERRE Marco ORLANDO Roberto FERRABONE Matteo ZICOVICH-WILSON Claudio M. DOVESI Roberto Dipartimento di Chimica Università di Torino and NIS Nanostructured Interfaces and Surfaces Centre of Excellence Via P. Giuria 7 10125 Torino Italy Nanochemistry Research Institute Department of Chemistry Curtin University GPO Box U1987 Perth WA 6845 Australia Facultad de Ciencias Universidad Autónoma del Estado de Morelos Av. Universidad 1001 Col. Chamilpa 62209 Cuernavaca (Morelos) Mexico

Symmetry can dramatically reduce the computational cost （running time and memory allocation） of Self-Consistent-Field ab initio calculations for crystalline systems. Crucial for running time is use of symmetry in the evaluation of one- and two-electron integrals, diagonalization of the Fock matrix at selected points in reciprocal space, reconstruction of the density matrix. As regards memory allocation, full square matrices （overlap, Fock and density） in the Atomic Orbital （AO） basis are avoided and a direct transformation from the packed AO to the SACO （Symmetry Adapted Crystalline Orbital） basis is per- formed, so that the largest matrix to be handled has the size of the largest sub-block in the latter basis. We here illustrate the effectiveness of this scheme, following recent advancements in the CRYSTAL code, concerning memory allocation and direct basis set transformation. Quantitative examples are given for large unit cell systems, such as zeolites （all-silica faujasite and silicalite MF1） and garnets （pyrope）. It is shown that the full SCF of 3D systems containing up to 576 atoms and 11136 Atomic Orbitals in the cell can be run with a hybrid functional on a single core PC with 500 MB RAM in about 8 h.

关键词： point symmetry Symmetry Adapted Crystalline Orbitals Fock matrix density matrix CPU time memory allocation quantum-mechanical calculations CRYSTAL code

Quantum Fisher Information for density Matrices with Arbitrary Ranks

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Communications in Theoretical Physics 2014年第1期61卷 45-50页

作者：刘京井晓辛钟伟王晓光 Zhejiang Institute of Modern Physics Department of PhysicsZhejiang University

We provide a new expression of the quantum Fisher information(QFI) for a general *** this expression,the QFI for a non-full rank density matrix is only determined by its *** expression can bring convenience for an inf... 详细信息

关键词： quantum Fisher information quantum metrology density matrix