量子力学混合态表象

在以往的文献中量子力学的表象都是纯态表象,在本文中我们从算符的合理排序和概率统计的正态分布思想出发,首次提出了量子力学混合态表象的概念,并证明了其完备性和正交性.量子力学混合态表象的优点是可以反映算符的多种表示以及其相应的排序规则.     

Wave-function collapse induced by thermal fluctuations of detector variables. statistical collapse of wave functions

We present a simple example where the wave-function collapse is realized by thermal fluctuations of detector variables. This mechanism for the wave-function collapse is essentially due to the indeterminacy of the initial internal-states of detectors by the thermal fluctuation. Two types of the collapse are shown: One is the mechanism of the collapse arising from the phase ambiguity of the initial detector state and another is that derived from the fluctuation of the number of particles in the detector actively working in single measurement process.     

在量子力学里先有算符,还是先有态矢

论证了在量子力学中,描写系统状态的态矢即即概率幅的概念是最根本的概念,它比描写动力学变量的算符的对易关系等性质更为重要。还举出了一般教材中常见的几个问题做例子来说明这一点。     

On the final state of spherical gravitational collapse

Following our recent finding [1] that, for the final state of continued spherical gravitational collapse of sufficiently massive bodies, the final gravitational mass of the fluidM _? → 0, we show that for a physical fluid the eventual value of 2M_?/R_? → 1 rather than 2M_?/R_?2M_?/R_? < 1 (the speed of light c = 1 and the gravitational constantG = 1), indicating the approach to a zero-mass black hole. We also point out that, as the final state is approached, the curvature components tend to blow up; also the proper radial distancel and the proper time (measured along a radial worldline) Τ → ∞, indicating that actually the singularity is never attained. We also identify that the final state may correspond to the local 3-speed attaining eitherV = 0 orV → c, even though invariant circumference contraction speedU =dR/dΤ → 0. Nonetheless, at a finite observation epoch, such Eternally Collapsing Objects (ECOs) may have a local speed of collapseV?c and the lab frame speed of collapse may be negligible because of high surface gravitational redshift. However, if quantum back reaction in the strong gravity regime would cause a phase transition of the form pressurep = - ρ, where ρ is the density of the collapsing fluid, it may be possible to have static Ultra Compact Objects (ûCOs) of arbitrary high mass [2]. While supposed Black Holes have no intrinsic magnetic field, ECOs or UCOs are likely to possess strong intrinsic magnetic fields, and we point out that there are already some tentative evidence for existence of such intrinsic magnetic fields in some Black Hole Candidates [3,4]. For the benefit of the readers who may not have gone through Paper I, we also include here the summary of the same. It clearly shows that the central result of Paper I can be derived even without knowing the meaning of the nomenclatureV or without imposing any of property ofV such as whetherV < 1 or not. In addition, we consolidate the same result from other physical considerations too.     

Electron excitation from ground state to first excited state:Bohmian mechanics method

The excitation process of electrons from the ground state to the first excited state via the resonant laser pulse is investigated by the Bohmian mechanics method. It is found that the Bohmian particles far away from the nucleus are easier to be excited and are excited firstly, while the Bohmian particles in the ground state is subject to a strong quantum force at a certain moment, being excited to the first excited state instantaneously. A detailed analysis for one of the trajectories is made, and finally we present the space and energy distribution of 2000 Bohmian particles at several typical instants and analyze their dynamical process at these moments.     

用纠缠态表象推导广义Ehrenfest定理

利用两粒子相对坐标和总动量的共同本征态|η〉构成的连续变量纠缠态表象,推导了转动系统的Ehrenfest定理,从而说明了在满足某些近似的情况下,量子力学不但能够与经典物理完美自洽,而且利用量子力学的规律可以导出相应的经典物理规律.     

Determinism,realism, and Stapp's 1985 proof of nonlocality

Two recent criticisms of Stapp's 1985 proof of an incompatibility between locality and quantum mechanics are clarified. One of these criticisms (charging that the proof requires determinism) is supported by a detailed logical analysis of the locality conditions in the proof. The other criticism (charging that the proof assumes realism) is shown to be based upon a misinterpretation of the rôle of counterfactuals in the proof. Further, Stapp's own replies to these criticisms are shown to be inadequate.     

用一个纠缠态实现多粒子纠缠态的量子隐形传送

提出分别在二维和高维系统中利用一个纠缠态作量子通道实现M粒子纠缠态的量子隐形传送方案. 该方案有多个接收者,通过控制引进辅助粒子数,可以任意调节传送后的纠缠态在各接收者之间的粒子数分布, 且成功传送的概率为1. 关键词： 量子隐形传态 纠缠态 量子通道     

量子力学定态不是驻波

作为一种经典或半经典的观点，可以认为定态是由波的干涉形成的驻波，但在量子力学中，定态本身是基本的，不是驻波。     

Covariant fuzzy observables and coarse-graining

A fuzzy observable is regarded as a smearing of a sharp observable, and the structure of covariant fuzzy observables is studied. It is shown that the covariant coarse-grainings of sharp observables are exactly the covariant fuzzy observables. A necessary and sufficient condition for a covariant fuzzy observable to be informationally equivalent to the corresponding sharp observable is given.     

Classicality without Decoherence: A Reply to Schlosshauer

Schlosshauer has criticized the conclusion of Wiebe and Ballentine (Phys. Rev. A 72:022109, 2005) that decoherence is not essential for the emergence of classicality from quantum mechanics. I reply to the issues raised in his critique, which range from the interpretation of quantum mechanics to the criterion for classicality, and conclude that the role of decoherence in these issues is much more restricted than is often claimed.     

用两粒子纠缠对进行{\bf\large{N}}粒子纠缠态的隐形传送

本文提出了一个方案:将三粒子纠缠态从一个发送者传给两个接收者之一,并将其推广到N粒子纠缠态的传送。这里，我们仅用两粒子纠缠对作通道就实现了N粒子纠缠态的传送。此方案相比以往的方案节省了大量纠缠资源，且成功传送的几率达到了1。     

Bound state solutions of the two-electron Dirac-Coulomb equation

We show that the Dirac-Coulomb Hamiltonian hasnormalizable eigenfunctions corresponding to bound states.     

Quantum state sharing of an arbitrary qudit state by using nonmaximally generalized GHZ state

We present a scheme for quantum state sharing of an arbitrary qudit state by using nonmaximally entangled generalized Greenberger-Horne-Zeilinger （GHZ） states as the quantum channel and generalized Bell-basis states as the joint measurement basis. We show that the probability of successful sharing an unknown qudit state depends on the joint measurements chosen by Alice. We also give an expression for the maximally probability of this scheme.     

关于态叠加原理的认同与争议

给出了不同学者关于量子力学态叠加原理的几种表述,分析比较了关于该原理的有关观点的争议,并对其中的原因进行了讨论。     

利用cluster态隐形传送任意三原子W态

提出一个隐形传送任意三原子纠缠W态的方案,在此方案中,选用由四个全同的二能级原子组成的cluster态作为量子信道.研究表明,接收者基于发送者的经典信息,借助于一个附加原子,实行联合幺正变换以及单原子幺正变换,可实现三原子W态的隐形传送.该方案不受外界热场和腔场耗散的影响,不需要贝尔态测量,成功实现传送的几率为1.     

Probabilistic teleportation of an arbitrary GHZ-class state with a pure entangled two-particle quantum channel and its application in quantum state sharing

This paper presents a scheme for probabilistic teleportation of an arbitrary GHZ-class state with a pure entangled two-particle quantum channel. The sender Alice first teleports the coefficients of the unknown state to the receiver Bob, and then Bob reconstructs the state with an auxiliary particle and some unitary operations if the teleportation succeeds. This scheme has the advantage of transmitting much less particles for teleporting an arbitrary GHZ-class state than others. Moreover, it discusses the application of this scheme in quantum state sharing.     

Quantum secure direct communication with Greenberger-Horne-Zeilinger-type state （GHZ state） over noisy channels

We propose a quantum error-rejection scheme for direct communication with three-qubit quantum codes based on the direct communication of secret messages without any secret key shared in advance. Given the symmetric and independent errors of the transmitted qubits, our scheme can tolerate a bit of error rate up to 33.1%, thus the protocol is deterministically secure against any eavesdropping attack even in a noisy channel.     

Several teleportation schemes of an arbitrary unknown multi-particle state via different quantum channels

We first provide four new schemes for two-party quantum teleportation of an arbitrary unknown multi-particle state by using three-, four-, and five-particle states as the quantum channel, respectively. The successful probability and fidelity of the four schemes reach 1. In the first two schemes, the receiver can only apply one of the unitary transformations to reconstruct the original state, making it easier for these two schemes to be directly realized. In the third and fourth schemes, the sender can preform Bell-state measurements instead of multipartite entanglement measurements of the existing similar schemes, which makes real experiments more suitable. It is found that the last three schemes may become tripartite controlled teleportation schemes of teleporting an arbitrary multi-particle state after a simple modification. Finally, we present a new scheme for three-party sharing an arbitrary unknown multi-particle state. In this scheme, the sender first shares three three-particle GHZ states with two agents. After setting up the secure quantum channel, an arbitrary unknown multi-particle state can be perfectly teleported if the sender performs three Bell-state measurements, and either of two receivers operates an appropriate unitary transformation to obtain the original state with the help of other receiver's three single-particle measurements. The successful probability and fidelity of this scheme also reach 1. It is demonstrated that this scheme can be generalized easily to the case of sharing an arbitrary unknown multi-particle state among several agents.