Exact symplectic structures and a classical model for the Dirac electron

We show how the classical model for the Dirac electron of Barut and coworkers can be obtained as a Hamiltonian theory by constructing an exact symplectic form on the total space of the spin bundle over spacetime.     

New loophole for the Einstein-Podolsky-Rosen paradox

Using the new concept of "stochastic gauge system", we describe a novel loophole to circumvent the Einstein-Podolsky-Rosen (EPR) paradox. We derive a "realistic" (i.e., classical) model, free from any paradox, which exactly emulates the spin EPR experiment. We conclude that Bell's inequalities are violated in classical physics as well, or, conversely that quantum mechanical theory is logically consistent with relativity.     

Classical and Quantum Theories of Spin

A great effort has been devoted to formulating a classical relativistic theory of spin compatible with quantum relativistic wave equations. The main difficulty in connecting classical and quantum theories rests in finding a parameter that plays the role of proper time at a purely quantum level. We present a partial review of several proposals of classical and quantum spin theories from the pioneering works of Thomas and Frenkel, revisited in the classical BMT work, to the semiclassical model of Barut and Zanghi. We show that the last model can be obtained from a semiclassical limit of the Feynman proper time parametrization of the Dirac equation. At the quantum level, we derive spin precession equations in the Heisenberg picture. Analogies and differences with respect to classical theories are discussed in detail.     

Common cause and contextual realization of Bell correlation

Considering the common cause principle, we construct a local-contextual hidden-variable model for the Bohm version of EPR experiment. Our proposed model can reproduce the predictions of quantum mechanics. It can be also extended to classical examples in which similar correlations may be revealed.     

Spontaneous emission in cavities: How much more classical can you get?

Cavity-induced changes in atomic spontaneous emission rates are often interpreted in terms of quantum electrodynamical zero-point field fluctuations. A completely classical method of computing this effect in terms of the unquantized normal mode structure of the cavity is presented here. Upon applying the result to a classical dipole radiating between parallel mirrors, we obtain the same cavity correction as that for atomic spontaneous emission in such a cavity. The theory is then compared with a recent experiment in the radio-frequency domain.It is a pleasure and an honor to dedicate this paper to Professor Asim O. Barut, who, as my teacher, advisor, and friend, has been a great inspiration to me as well as many, many others.Work supported by the National Research Council of the United States.     

A nonstandard model

An elementary-particle picture developed primarily by Barut as an alternative to the standard model is re-examined. This model is formulated on the basis of strong short-range magnetic interactions among the stable particles (p, e^–, v) and at present is able to account qualitatively for most of the known phenomena.     

Electrolytic coloration of cuprous chloride crystals

Electrolytic coloration of cuprous chloride crystals is observed. Visible optical absorption spectra, coloration kinetics so as electric current kinetics are recorded at high temperature. EPR experiments are performed both at high temperature and with quenched samples. Two types of defects are found, one being metastable, the other stable, remaining after quenching. All experimental results do not agree with the classical theory of absorption of light by metal colloids. A model is proposed which qualitatively explains all experimental features of these phenomena.     

一种网络多用户量子认证和密钥分配理论方案

提出了一种网络多用户量子认证和密钥分配理论方案.类似于现代密码学中的网络认证体系结构提出了一种基于网络中用户与所属的可信服务器之间共享Einstein-Podolsky-Rosen(EPR)纠缠对进行身份认证和密钥分配的分布式客户机/服务器体系结构.基于该体系结构实现网络中任意用户之间的身份认证和密钥分配.可信服务器只提供用户的身份认证以及 交换粒子之间的纠缠使得两个想要秘密通信的用户的粒子纠缠起来.密钥的生成由发起请求 的用户自己完成.网络中的用户只需和所属的可信服务器共享EPR纠缠对通过经典信道和量子 信道与服务器通信.用户不需要互相共享EPR纠缠对，这使得网络中的EPR对的数量由O(n²)减小到O(n). 关键词： 量子认证 量子密钥分配 客户机/服务器 纠缠交换     

Quantum teleportation of a polarization state with a complete bell state measurement

We report a quantum teleportation experiment in which nonlinear interactions are used for the Bell state measurements. The experimental results demonstrate the working principle of irreversibly teleporting an unknown arbitrary polarization state from one system to another distant system by disassembling into and then later reconstructing from purely classical information and nonclassical EPR correlations. The distinct feature of this experiment is that all four Bell states can be distinguished in the Bell state measurement. Teleportation of a polarization state can thus occur with certainty in principle.     

Classical foundations of quantum groups

The concept of classical r matrices is developed from a purely canonical standpoint. The final purpose of this work is to bring about a synthesis between recent developments in the theory of integrable systems and the general theory of quantization as a deformation of classical mechanics. The concept of quantization algebra is here dominant; in integrable systems this is the set of dynamical variables that appear in the Lax pair. The nature of this algebra, a solvable Lie algebra in such models as the Sine-Gordon and Toda field theories but semisimple in the case of spin systems, provides a useful scheme for the classification of integrable models. A completely different classification is obtained by the nature of the r matrix employed; there are three kinds: rational, trigonometric, and elliptic. All cases are studied in detail, with numerous examples. Some of the problems connected with quantization are discussed.This paper is dedicated to my friend Asim Barut.     

Simultaneous acquisition of pulse EPR orientation selective spectra

High resolution pulse EPR methods are usually applied to resolve weak magnetic electron-nuclear or electron-electron interactions that are otherwise unresolved in the EPR spectrum. Complete information regarding different magnetic interactions, namely, principal components and orientation of principal axis system with respect to the molecular frame, can be derived from orientation selective pulsed EPR measurements that are performed at different magnetic field positions within the inhomogeneously broadened EPR spectrum. These experiments are usually carried out consecutively, namely a particular field position is chosen, data are accumulated until the signal to noise ratio is satisfactory, and then the next field position is chosen and data are accumulated. Here we present a new approach for data acquisition of pulsed EPR experiments referred to as parallel acquisition. It is applicable when the spectral width is much broader than the excitation bandwidth of the applied pulse sequence and it is particularly useful for orientation selective pulse EPR experiments. In this approach several pulse EPR measurements are performed within the waiting (repetition) time between consecutive pulse sequences during which spin lattice relaxation takes place. This is achieved by rapidly changing the main magnetic field, B(0), to different values within the EPR spectrum, performing the same experiment on the otherwise idle spins. This scheme represents an efficient utilization of the spectrometer and provides the same spectral information in a shorter time. This approach is demonstrated on W-band orientation selective electron-nuclear double resonance (ENDOR), electron spin echo envelope modulation (ESEEM), electron-electron double resonance (ELDOR)--detected NMR and double electron-electron resonance (DEER) measurements on frozen solutions of nitroxides. We show that a factors of 3-6 reduction in total acquisition time can be obtained, depending on the experiment applied.     

晶体NiX2(X=Cl,Br,I)的光谱和电子顺磁共振谱研究

在强场耦合图像中,采用双自旋-轨道耦合(SO)参量模型建立了过渡族3d2(3d8)离子的三角对称下全组态光谱能级和电子顺磁共振(EPR)公式.与经典的晶体场理论(仅考虑中心金属离子的自旋-轨道耦合作用)相比较,该公式还包括了配体离子的自旋-轨道耦合作用的贡献,这一模型在应用于计算共价性较强的晶体光谱和电子顺磁共振谱可得到合理的结果.作为验证,用完全对角化方法研究了品体NiX2(X=Cl,Br,I)的光谱和电子顺磁共振谱,结果表明,理论与实验很好地符合.建立的全组态谱能级和电子顺磁共振公式为更精确地计算光谱和电子顺磁共振谱提供了一条可行方法.     

Influence of carbonic nanostructure formation on EPR line parameters during carbonization of wheat bran

Carbonized wheat bran samples were studied by electron paramagnetic resonance (EPR) spectroscopy, elemental analysis and electron microscopy. The carbonization was performed in the temperature range from 250 to 800 °C in argon medium. The carbon content increased with temperature. At high temperatures a sharp decrease in the concentration of free radicals takes place. It is shown that at high temperatures the EPR line width reduces from 0.87 (initial) to 0.11 mT. This phenomenon is explained by the fact that at high temperatures there occurs the formation not only of graphitelike structures (classical interpretation) but also of different nanosize structures. The electron microscopy data verify the formation of different forms of nanostructures in the carbonized wheat bran samples. Presented at the 5th Asia-Pacific EPR/ESR Symposium, August 24–27, 2006, Novosibirsk, Russian Federation.     

The Wave Function Collapse as an Effect of Field Quantization

It is pointed out that ordinary quantum mechanics as a classical field theory cannot account for the wave function collapse if it is not seen within the framework of field quantization. That is needed to understand the particle structure of matter during wave function evolution and to explain the collapse as symmetry breakdown by detection. The decay of a two-particle bound s state and the Stern-Gerlach experiment serve as examples. The absence of the nonlocality problem in Bohm’s version of the EPR arrangement favours the approach described.     

利用大失谐Jaynes-Cummings模型实现原子的隐形传态

提出了一个未知原子的隐形传态方案,它是通过原子与腔场大失谐相互作用实现的.方案中,两原子缠结的EPR态作为联系发送者与接收者之间的量子信息通道,将欲传送的未知原子和EPR态中的一个原子依次注入到初始制备于相干态 |α>的腔场,然后分别对两原子和腔场进行联合测量,通过经典信息通道将测量结果传递给接收者.这样,接收者只要对EPR的另一个原子执行相应的幺正操作就能重构未知原子态.     

Dirac equation in Robertson-Walker metric

We recast the Dirac relativistic equation within the theoretical framework of the Robertson-Walker metric, using spatial hypersurfaces that are essentially curved, and hence more general, as compared to the flat ones employed by Barut and Duru.     

Comment on “analytic solution of the covariant shell model of three Dirac fermions with harmonic forces”

We point out that there is an error in a recent paper by Strobel and Hughes that invalidates the authors' arguments unless the centre-of-mass frame is chosen. An analogical error appears also in an earlier paper by Barut and Strobel. It concerns the problem of two as well as of three Dirac particles.     

New experimental tests of the photon’s indivisibility

We consider the old foundational problem of quantum/classical optics ?C indivisibility of photon. Quantum theory predicts that in experiments on coincidence detection double clicks are impossible (up to noise); on the other hand, the known semiclassical and classical models predict a relatively high rate of coincidence. We present a model of the classical (random) wave type which predicts that in the same way as in quantum optics coincidence of clicks is a rare event. However, this model has a new prediction compared to quantum optics, namely, that the rate of double clicks depends substantially on the discrimination threshold of a detector. We propose to perform new detailed tests to check the discrimination threshold dependence predicted by our model. In experiments on coincidence detection performed to date, for example, the Grangier experiment does not contain statistical data on the threshold dependence.     

Quantum teleportation of one－ and two－photon superposition states

Quantum teleportation of one- and two-photon superposition states based on EPR entanglement of continuous-wave two-mode squeezed state is discussed. The fidelities of teleportation axe deduced for two different input quantum states. The dependence of the fidelity on the parameters of EPR entanglement and the gain of the classical channels are shown numerically. Comparing with the teleportation of Fock state and coherent state, it is pointed out that for given EPR entanglement and classical gain, the higher the nonclassicality of the input state, the lower the accessible fidelity of teleportation.