Physica B+C最新文献

This paper introduces an information operator specifying the rate of change of probability to obtain a modified Schrödinger equation (MSE) which provides automatic state vector collapse under the conditions of “complete measurement” interaction.

Already in 1926, Schrödinger constructed “minimum uncertainty wave packets” for the harmonic oscillator, later popularized as “coherent states”, which today are widely used, for instance in quantum optics (laser theory) and in quantum field theory (infrared behaviour in QED and QCD). It is argued that Schrödinger's discovery of coherent states played a crucial role in Heisenberg's discovery of the uncertainty principle in 1927.

An achromatic imaging instrument for neutrons of wavelengths larger than 1.2 nm is described. The measured resolution of 28.5 μm is not too far away from the ultimate limit of 6 μm calculated by wave mechanics.

The methods we will describe are somewhat related to classical optics. They have been used at the research reactor in Munich and later at the Institute Laue-Langevin in Grenoble, helping to improve research in neutron scattering and in nuclear physics using neutrons.

A brief summarizing review is given of all those neutron interferometric experiments performed hitherto which explicitly use the spin-$\text{1}\text{2}$ particle properties of the neutron. It covers topics as the verification of the 4π-periodicity of spinors, the cooperative action of nuclear phase shift and spin-rotation on the neutron wave function, the demonstration of the quantum mechanical principles of fermion spin-state superposition and the more recent double resonance experiments where the two interfering beams propagate through spatially separated oscillatory magnetic fields. Finally a proposal will be presented also for a so-called “late-choice” experiment with polarized neutrons.

The interaction of a single Rydberg atom with a single mode of the electromagnetic field and the resonance fluorescence of a single atomic ion stored in radio-frequency trap were investigated. In the former experiment, the quantum collapse and revival of the atomic inversion predicted by the Jaynes-Cummings model could be demonstrated for the first time. In the latter experiment, antibunching and sub-Poissonian photon statistics were detected in the fluorescent light. Furthermore the observation of the crystallization of few ions in a trap is described. Since the stored ions can be cooled by the laser light and heated by the radio frequency field of the trap, subsequent phase transitions could be observed.

For didactic as well as historical reasons it does not make much sense for about thirty years to speak of the diffraction of electron waves by microscopic slits as an “imaginary experiment”.

The coherence length of electron waves has been measured by the phase shift of a coherent partial electron wave propagating through a metallic micro-tube to which an electric potential is applied.

The statement by H. Hora that the phase shift of electron waves due to the magnetic vector potential depends on electron velocity is not supported by experiments.

There is no principal upper limit for the electron-optical path length difference due to an enclosed magnetic flux.

This paper describes our progress on a neutron interferometry search for the Aharonov-Casher (A-C) effect. Unpolarized neutrons are passed through a 40 kV/mm vacuum electrode system. The spin-dependent phase is set to maximum sensitivity with a magnetic field, and the spin-independent phase is adjusted to zero (modulo 2π) using the Earth's gravitational field. Upon reversal of the electric field, the predicted A-C phase shift is 0.2°. Currently, our results are statistically limited.

Using an electron biprism interferometer completely different in its technical design compared to conventional instruments, we hope to prove the rotationally induced phase shift of electron waves. Besides its unconventional design, another unique feature of our instrument is a Wien filter incorporated in its beam path which allows to shift the coherent wave packets relative to each other longitudinally. This provides the possibility of (1) reestablishing maximum overlap of the wave packets and in turn maximum contrast of the interference fringes and (2) of measuring coherence lengths of electron waves as well as, via Fourier spectroscopy, the energy distribution of the electrons.