Spin correlation in stochastic mechanics

Stochastic mechanics may be used to described the spin of atomic particles. The spin variables have the same expectations as in quantum mechanics, but not the same distributions. They play the role of hidden variables that influence, but do not determine, the results of Stern-Gerlach experiments involving magnets. During the course of such an experiment spin becomes correlated with position. The case of two particles with zero total spin occurs in Bohm's version of the Einstein-Rosen-Podolsky experiment.This material is based upon work supported by the National Science Foundation under Grant No. MCS-8002945.     

Observation of the continuous stern-gerlach effect on an electron bound in an atomic Ion

We report on the first observation of the continuous Stern-Gerlach effect on an electron bound in an atomic ion. The measurement was performed on a single hydrogenlike ion ( 12C5+) in a Penning trap. The measured g factor of the bound electron, g = 2.001 042(2), is in excellent agreement with the theoretical value, confirming the relativistic correction at a level of 0.1%. This proves the possibility of g-factor determinations on atomic ions to high precision by using the continuous Stern-Gerlach effect. The result demonstrates the feasibility of conducting experiments on single heavy highly charged ions to test quantum electrodynamics in the strong electric field of the nucleus.     

Decoherence due to internal mesoscopic environment: a possible experimental test

Following the fundamentals of the Stern-Gerlach experiment, we propose for an experimental situation eventually revealing the decoherence effect due to the internal mesoscopic environment. The experiment-set-up we propose is a straightforward extension of the set-up recently used in the neutron optics interference experiments. First, we point to and discuss the occurrence of decoherence for the atoms path in the Stern-Gerlach experiment. Then, comparing a Stern-Gerlach apparatus with the apparatus of our set-up-proposal, we point out the occurrence of decoherence and consequently of non-violation of the Bells inequality for a single atoms degree of freedom due to the environment consisting of the order of 10² particles.Received: 29 December 2003, Published online: 17 February 2004PACS: 03.65.Yz Decoherence; open systems; quantum statistical methods - 03.75.Dg Atom and neutron interferometry - 03.65.Ud Entanglement and quantum nonlocality (e.g. EPR paradox, Bells inequalities, GHZ states, etc.)     

Measurement Theory in Deutsch’s Algorithm Based on the Truth Values

We propose a new measurement theory, in qubits handling, based on the truth values, i.e., the truth T (1) for true and the falsity F (0) for false. The results of measurement are either 0 or 1. To implement Deutsch’s algorithm, we need both observability and controllability of a quantum state. The new measurement theory can satisfy these two. Especially, we systematically describe our assertion based on more mathematical analysis using raw data in a thoughtful experiment.     

Is Nonlocality Responsible for the Violation of Bell’s Inequalities?

Bell’s theorem has been widely argued to show that some of the predictions of quantum mechanics which are obtained by applying the Born’s rule to a class of entangled states, are not compatible with any local-causal statistical model, via the violation of Bell’s inequalities. On the other hand, in the previous works, we have shown that quantum dynamics and kinematics are emergent from a statistical model that is singled out uniquely by the principle of Locality. Here we shall show that the local-causal model supports entangled states and give the statistical origin of their generation. We then study the Stern-Gerlach experiment to show that the Born’s rule can also be derived as a mathematical theorem in the local-causal model. These results lead us to argue that nonlocality is not responsible for the quantum mechanical and most importantly experimental violation of Bell’s inequalities. The source(s) of violation has to be sought somewhere else.     

碱束斯特恩-盖拉赫实验

利用K束斯特恩－盖拉赫实验装置，通过对束源和表面电离探测器的改进，实现Li,Na,K,Rb,Cs全碱束斯特恩－盖拉赫实验。     

Generalized Stern-Gerlach effect for chiral molecules

The Stern-Gerlach effect is well known as spin-dependent splitting of a beam of atoms with magnetic moments by a magnetic-field gradient. Here, we show that an induced gauge potential may lead to a similar effect for chiral molecules. In the presence of three inhomogeneous light fields, the center of mass of a three-level chiral molecule is subject to an optically induced gauge potential, and the internal dynamics of the molecule can be described as an adiabatic evolution in the reduced pseudospin subspace of the two lowest energy levels. We demonstrate numerically that such an induced gauge potential can lead to observable pseudospin-dependent and chirality-dependent generalized Stern-Gerlach effects for mixed left- and right-handed chiral molecules under realistic conditions.     

Collapse of the wave function related to the use of Schmidt decomposition

In the measurement process, certain degrees of freedom of the observables are selected and correlations are produced with corresponding degrees of freedom of the measuring macroscopic device. These correlations are described, in the present paper, by using the Schmidt decomposition, in which the eigenvalues of the reduced density matrices of these two systems are equal. The measurement process is related to the trace operation over the observable degrees of freedom, since we do not directly measure the microscopic system but its corresponding macroscopic part in the Schmidt decomposition. This trace operation leads only to partial information on the microscopic system referred to as the “collapse” of the wave function. This interpretation is demonstrated by analyzing Stern-Gerlach experiments.     

Playing with Quantum Toys: Julian Schwinger’s Measurement Algebra and the Material Culture of Quantum Mechanics Pedagogy at Harvard in the 1960s

In the early 1960s, a PhD student in physics, Costas Papaliolios, designed a simple—and playful—system of Polaroid polarizer filters with a specific goal in mind: explaining the core principles behind Julian Schwinger’s quantum mechanical measurement algebra, developed at Harvard in the late 1940s and based on the Stern-Gerlach experiment confirming the quantization of electron spin. Papaliolios dubbed his invention “quantum toys.” This article looks at the origins and function of this amusing pedagogical device, which landed half a century later in the Collection of Historical Scientific Instruments at Harvard University. Rendering the abstract tangible was one of Papaliolios’s demonstration tactics in reforming basic teaching of quantum mechanics. This article contends that Papaliolios’s motivation in creating the quantum toys came from a renowned endeavor aimed, inter alia, at reforming high-school physics training in the United States: Harvard Project Physics. The pedagogical study of these quantum toys, finally, compels us to revisit the central role playful discovery performs in pedagogy, at all levels of training and in all fields of knowledge.     

Diffraction Enhancement of the Stern—Gerlach Effect for a Neutron in a Crystal

JETP Letters - The spatial splitting of an unpolarized neutron beam into two spin components in an inhomogeneous magnetic field (an analog of the Stern-Gerlach experiment) with small gradients has...     

关节测量臂在上海光源元件标定中的应用

 关节测量臂以便携、高精度的小尺寸测量性能在上海光源的元件标定过程中得到了广泛应用。介绍了上海光源元件标定的方案设计,操作工艺以及质量保证措施等,着重探讨了关节测量臂的合理使用。在仪器使用过程中,利用软件的学习功能有效地提高了工作效率;通过将温度变化控制在2 ℃范围内,并利用标准尺及不同仪器的标定结果相互比较来控制、监测系统误差等,从而保证高精度的测量结果。     

Can the Statistical Interpretation of Quantum Mechanics be Inferred from the Schrödinger Equation?—Bell and Gottfried

In his paper titled ‘Against “measurement”?’ [Physics World 3(8), 33–40 [1990]], Bell criticised arguments that use the concept of measurement to justify the statistical interpretation of quantum theory. Among these was the text of Gottfried [Quantum Mechanics (Benjamin, New York, [1966])]. Gottfried has replied to this criticism, claiming to show that, for systems with both continuous and discrete degrees of freedom, the statistical interpretation for the discrete variables is implied by requiring that the continuous variables are described classically. In the present paper, Gottfried’s argument is criticised. It is suggested that he takes over aspects of classical physics which are in conflict with the classical limit of the Schrödinger equation. He incorrectly assumes that, in the output from a Stern-Gerlach apparatus, the wave-function of any ion is restricted to one or another of the beams.     

Spin State Determination Using a Stern-Gerlach Device

The well-known Stern-Gerlach device is proposed here for determination of a particle spin state instead of using it for measurement of spin observables. It is shown that measurement of particle momentum distributions (before and after the action of the device magnetic field) allows one to determine the particle initial spin state in the case of an arbitrary spin value. It is demonstrated that one cannot use for this purpose the usual treatment of the Stern-Gerlach experiment based on the entanglement of spin and spatial states.     

High pressure studies at the photon factory

Abstract

The Photon Factory has unique features from the point of view of high pressure research. Six beamlines have been used for high pressure experiments, two of which were constructed as dedicated beamlines for large high pressure devices. Various kinds of high pressure studies, such as powder and single crystal x-ray diffraction and absorption experiments, have been carried out on these beamlines by more than 30 user groups, including foreign visitors. Two types of high pressure apparatuses are most frequently used. One is the large volume high pressure devices (MAX80 and MAX90) combined with high energy and/or high brightness synchrotron radiation. The other is a system combining the diamond anvil cell with a 2-dimensional detector, the IMAGE PLATE. Many improvements have been made both in the high pressure techniques and the diffraction measurement methods.

Presented at the IUCr Workshop on ‘Synchrotron Radiation Instrumentation for High Pressure Crystallography’. Daresbury Laboratory 20-21 July 1991     

Uncertainty relations for noise and disturbance in generalized quantum measurements

Heisenberg’s uncertainty relation for measurement noise and disturbance is commonly understood to state that in any measurement the product of the position measurement noise and the momentum disturbance is not less than Planck’s constant divided by 4π. However, it has been shown in many ways that this relation holds only for a restricted class of measuring apparatuses in the most general formulation of measuring processes. Here, Heisenberg’s uncertainty relation is generalized to a relation that holds for all the possible quantum measurements, from which rigorous conditions are obtained for measuring apparatuses to satisfy Heisenberg’s relation. In particular, every apparatus with the noise and the disturbance statistically independent from the measured object is proven to satisfy Heisenberg’s relation. For this purpose, all the possible quantum measurements are characterized by naturally acceptable axioms. Then, a mathematical notion of the distance between probability operator valued measures and observables is introduced and the basic properties are explored. Based on this notion, the measurement noise and disturbance are naturally defined for any quantum measurements in a model independent formulation. Under this formulation, various relations for noise and disturbance are also derived for apparatuses with independent noise, independent disturbance, unbiased noise, and unbiased disturbance as well as noiseless apparatuses and nondisturbing apparatuses. Two models of position measurements are also discussed in the light of the new uncertainty relations to show that Heisenberg’s relation can be violated even by approximately repeatable position measurements.     

变值测量结构及其可视化统计分布

利用测量计算模型和系统化参量统计方法模拟双态量子交互作用系统,在多种交互作用模式下模拟双路量子干涉测量的统计分布效应.从量子交互作用出发,对Einstein受激发射,Mach-Zehnder干涉仪和Stern-Gerlach自旋测量等测量模式形成测量四元组.利用多变量逻辑函数和变值原理,在N元0-1输入/输出序对上形成变值测量四元组,建立变值双路模拟模型.变值模型根据:概率、同步/异步、对称/反对称等不同组合条件特征输出统计分布结果,形成2组8个统计直方图.     

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.     

Is spin coherence like Humpty-Dumpty? I. Simplified treatment

When Humpty-Dumpty had his great fall nobody could put him together again. A vastly more moderate challenge is to reunite the two partial beams of a Stern-Gerlach apparatus with such precision that the original spin state is recovered. Nevertheless, as we demonstrate, a substantial loss of spin coherence always occurs, unless the experimenter is able to control the magnetic field's inhomogeneity with an accuracy of at least one part in 10⁵.     

Implementing the Deutsch algorithm with atoms and cavities

It is shown that the Deutsch algorithm can be implemented using high-Q cavities in which the qubits are represented by single cavity modes restricted in the space spanned by the two lowest Fock states.