Physica B+C最新文献

A novel theory, when it appears, cannot but use old words to label new concepts. In some cases, the extension in meaning thus conferred to standard terminology is natural enough so that the transfer may not lead to too many misunderstandings. Most often, however, and especially when the conceptual gap between the old and the new theory is a wide one, a casual transfer of términology may lead to epistemological and pedagogical difficulties. This situation has been and still is particularly serious in quantum theory. Here, the careless use of words taken from classical physics — such as quantum “mechanics”, “uncertainty”, etc. — , is compounded by the uncritical use of interpretative terms linked to a definite, if implicit, philosophical point of view — such as “complementarity”, “wave-particle duality”, “observables”, etc. While these words and the ideas they represent have played a major role in the birth of quantum physics more than half a century ago, they are no longer necessarily the best ones to be used today. It is not argued here that we should start afresh and create from scratch a supposedly adequate vocabulary for quantum physics. Abuse of language certainly is unavoidable in science as it is in any human communication; without it, language would not live and evolve. But, at the very least, let us recognize it for what it is, so that it does not add its troubles to already complicated issues. And in some definite instances, still, a willing effort to replace specially ambiguous words might be worthwhile.

A coherent state interacting with a suitable nonlinearity can be transformed into a quantum superposition of two coherent states 180° out of phase with each other. The interference between the two macroscopic components of this Schrödinger's cat-like state can be detected with a homodyne detector.

We report numerical solution of a Schrödinger equation modified by the nonlinear term b ln|ψ|² as proposed by Bialynicki-Birula and Mycielski. Experiments on the diffraction of cold neutrons at an absorbing straight edge performed earlier had set a very low upper limit on b, the strength of the nonlinearity, and it was the purpose of the present calculations to check the validity of some approximations made in the evaluation of that experiment. The numerical solutions show diffraction both in the usual spatial domain and in the time domain. When compared with the earlier estimates we find agreement within a factor of two.

The theory of dynamical diffraction is formulated such that it displays the anisotropy of the wave vector distribution of the diffracted beam explicitly. The result can be interpreted such that the coherence lengths of the diffracted beam are extremely different. It is also used to explain the “non-dispersive” phase shift in perfect-crystal interferometers.

The basic considerations and experimental results of electron interference and holography are presented here. More than 1600 biprism fringes have been attained in a JEM-200CX thermionic electron gun microscope. Contour maps of MgO smoke particles were observed by the double-time exposure method.

The Aharonov-Bohm effect effords a beautiful insight into the non-local nature of quantum theory. Unfortunately, because of the topological aspects to that effect, which are quite fascinating in their own right, there is an unfortunate tendency to connect these two independent elements. The present effect exhibits the non-locality, free of topological considerations, although it is related to the Berry phase, another much-discussed recent phenomenon. The effect consists of keeping a particle confined to a small region of a box with infinite walls. If the wall of the box is moved, then even though the particle is nowhere near the wall, it will experience a phase shift, which in principle is subject to experimental verification.

This is a short survey of the solution to a theoretical problem stated by E. Schrödinger in 1931–1932 in relation with the role of probability theory in quantum mechanics. It is founded on a novel probabilistic interpretation of the classical heat (or diffusion) equation. The new resulting classical theory is the closest classical analogy of quantum mechanics.

Because quantum mechanics has severe interpretational problems which have not been resolved within the theory of quantum mechanics, a new approach to basic physics is proposed. Elementary particles are hypothesized to be the constructive interference peaks of a wave system extending throughout the universe. It is then shown that the wave system is in the lowest energy state when the wave modes constructively interfere. Consequently, the interference peaks are stable entities since any reduction in the constructive interference would raise the energy of the system. The Schrödinger equation is derived from the wave system based on the Lorentz invariance of the classical wave equation subject to the condition that the constructive interference peaks remain in-phase with the wave modes. In addition, the results of the two-slit interference experiment are logically explained.

Since their advent interferometry with X-rays and neutrons have developed steadily. A number of excellent reviews is covering the development up to about five years ago. Advances since then are treated in this review. Topics included are: understanding of angstrom wave interferometers, theory of operation, types, contrast, complementarity, strategies and refinement of measurement, nonlinear Fizeau effect with neutrons, action of gravity and inertia on neutron phase, interferometers with separated crystals, interferometer combining X-ray and optical operation, interferometer combining X-ray and neutron operation.