共查询到18条相似文献,搜索用时 140 毫秒
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量子场论中的自旋算符 总被引:2,自引:0,他引:2
从量子场论的角度对相对论粒子的运动自旋概念作了进一步深入研究.构造了场量子自旋以及场系统运动自旋两个新算符.给出了场量子自旋动量空间的显式表达式以及用Poincar啨群生成元表示的场系统运动自旋的显式表达式.借助这两个算符,可以干净地解决有关场自旋的问题,表明它们才是场自旋的恰当的算符. 相似文献
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在非相对论框架内,从非相对论薛定谔方程出发,将自由电子的非相对论哈密顿算符开方,推出了自由的两分量泡利旋量满足的动力学方程;进而在经典外电磁场中,利用最小耦合原理,推出了在外电磁场中非相对论电子满足的泡利方程.在此基础上,讨论经典电动力学与量子力学不一致之处,并从群表示论和量子化对粒子的自旋进行了分析. 相似文献
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提出利用二粒子部分纠缠态概率性地实现开靶目标的非局域量子可控非(CNOT)门的操控方案.首先考虑利用3个二粒子部分纠缠态实现3个靶目标共享的非局域量子CNOT门的受控操作,然后将该方案推广到N个靶目标共享的情形. 在该方案中,控制端Alice的局域正定算符值测量(POVM)起着关键作用,给出了该测量算符的数学表式.值得注意的是, 用二粒子部分纠缠态可确定性地实现非局域CNOT门.
关键词:
二粒子部分纠缠态
非局域可控非门
开靶目标
正定算符值测量 相似文献
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Relativistic Spin Operators 总被引:1,自引:0,他引:1
ZHANGPeng-Fei RUANTu-Nan 《理论物理通讯》2001,35(3):293-300
A systematic theory on the appropriate spin operators for the relativistic states is developed.For a massive relativistic particle with arbitrary nonzero spin,the spin operator should be replaced with the relativistic one,which is called in this paper as moving spin.Further the concept of moving spin is discussed in the quantum field theory.A new operator,field quanta spin is defined and in terms of the generators of Poincare group the moving spin of field system is constructed.It is shown that,in virtue of the two operators,problems in quantum field concerned spin can be neatly settled. 相似文献
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We discuss the form of the spin operator in relativistic quantum mechanics. We derive the form of the spin operator in the case when the states with negative energies are admitted. It appears that for a Dirac particle the spin operator reduces to the so called mean-spin operator introduced by Foldy and Wouthuysen. We show that the spin operator transforms under Lorentz group action according to an operator Wigner rotation, analogously as a Bloch vector describing polarization of a particle in momentum representation. 相似文献
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根据Heisenberg对应原理(HCP),在经典极限下厄密算符的量子矩阵元对应经典物理量的Fourier展开系数.将HCP应用到相对论领域的Dirac方程中,对于自由粒子和在匀磁场中的带电粒子,其量子算符的矩阵元在经典极限下对应着相对论物理方程的解.计算表明,在经典极限下量子期望值就是对应经典物理量的时间平均值. 相似文献
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Spin is an important quantum degree of freedom in relativistic quantum information theory. This paper provides a first-principles derivation of the observable corresponding to a Stern–Gerlach measurement with relativistic particle velocity. The specific mathematical form of the Stern–Gerlach operator is established using the transformation properties of the electromagnetic field. To confirm that this is indeed the correct operator we provide a detailed analysis of the Stern–Gerlach measurement process. We do this by applying a WKB approximation to the minimally coupled Dirac equation describing an interaction between a massive fermion and an electromagnetic field. Making use of the superposition principle we show that the +1 and −1 spin eigenstates of the proposed spin operator are split into separate packets due to the inhomogeneity of the Stern–Gerlach magnetic field. The operator we obtain is dependent on the momentum between particle and Stern–Gerlach apparatus, and is mathematically distinct from two other commonly used operators. The consequences for quantum tomography are considered. 相似文献
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According to the Heisenberg correspondence principle, in the classical limit, quantum matrix element of a Hermitian operator reduces to the coefficient of the Fourier expansion of the corresponding classical quantity. In this article, such a quantum-classical connection is generalized to the relativistic regime. For the relativistic free particle or the charged particle moving in a constant magnetic field, it is shown that matrix elements of quantum operators go to quantities in Einstein’s special relativity in the classical limit. Especially, matrix element of the standard velocity operator in the Dirac theory reduces to the classical velocity. Meanwhile, it is shown that the classical limit of quantum expectation value is the time average of the classical variable. 相似文献
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For a relativistic spinning particle with an anomalous magnetic moment, Lienard-Wiechert potentials are constructed within the pseudoclassical approach. Some specific cases of the motion of a spinning particle are considered on the basis of general expressions obtained in this study for the Lienard-Wiechert potentials. In particular, the intensity of the synchrotron radiation from a transversely polarized particle moving along a circle at a constant speed is investigated as a function of the particle spin. In the specific case of particles having no anomalous magnetic moment and moving in an external uniform magnetic field, the resulting expressions coincide with familiar formulas from the quantum theory of radiation. The spin dependence of the polarization of synchrotron radiation is investigated. 相似文献
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Zubarev’s method of non-equilibrium statistical operator is applied to problems of relativistic kinetic theory. Within this method, a generalized relativistic quantum kinetic equation for the relativistic Wigner function is derived with taking into account the drift term of the Vlasov type and the collision integral of the second order in particle interaction. It is shown that this result holds as well for gauge invariant theories in the case of slowly changing fields. An advantage of the developed approach is exemplified by the consideration of relativistic nuclear matter within the Walecka and Nambu-Jona-Lasinio models. Typical relativistic effects like retardation, spin degrees of freedom and antiparticle evolution are taken into consideration. 相似文献
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Relativistic symmetries with the trigonometric Pschl-Teller potential plus Coulomb-like tensor interaction 下载免费PDF全文
The Dirac equation is solved to obtain its approximate bound states for a spin-1/2 particle in the presence of trigonometric Pschl-Teller(tPT) potential including a Coulomb-like tensor interaction with arbitrary spin-orbit quantum number κ using an approximation scheme to substitute the centrifugal terms κ(κ± 1)r-2.In view of spin and pseudo-spin(p-spin) symmetries,the relativistic energy eigenvalues and the corresponding two-component wave functions of a particle moving in the field of attractive and repulsive tPT potentials are obtained using the asymptotic iteration method(AIM).We present numerical results in the absence and presence of tensor coupling A and for various values of spin and p-spin constants and quantum numbers n and κ.The non-relativistic limit is also obtained. 相似文献