The interference effect between the neutron spinor components is investigated. It is shown that the diffusion of the neutron wave-packet under an unhomogeneous magnetic field is related to the phase shift angle between the two spinor components. We propose that this effect could be used to detect the phase-shift of a coherent neutron beam having passed through some medium. In the interference experiment based upon this principle one will not need to use Bragg reflection from crystal planes for splitting and recombining the beam, and the dimension of the phase shift region will be much longer than that of the usual Bonse-Kart type neutron interferometer.
The interference effect between the neutron spinor components is investigated. It is shown that the diffusion of the neutron wave-packet under an unhomogeneous magnetic field is related to the phase shift angle between the two spinor components. We propose that this effect could be used to detect the phase-shift of a coherent neutron beam having passed through some medium. In the interference experiment based upon this principle one will not need to use Bragg reflection from crystal planes for splitting and recombining the beam, and the dimension of the phase shift region will be much longer than that of the usual Bonse-Kart type neutron interferometer.
The interfererice between the spinor components of the potarized neutron beam passing through a Mezei-coil investigated. The authors proposed a method to detect the phase shift of the spinor Components a to test the principle of the fermion spin superposition. The influence of the earth gravity on the spinor interference is considered. The results show that the Planck's constant and the Newtonian gravitational constant G(or q) both are involved in the phase shift , which is independent of the neutron mass.
If a spin-½ particle is placed in a constant uniform magnetic field for a time t during which, classically, the Larmor precession angle would be θ, then according to quantum mechanics the components of the spin part of the wave function undergo phase changes of ±θ/2. Hence, corresponding to a classical precession of 2π radians, there is a sign change of the spinor, whatever the initial polarization may be. Bernstein pointed out that this sign change can be observed by coherently splitting a fermion beam, subjecting one part to the magnetic field, and coherently recombining the parts. Evidently, the same interference effect can be achieved by subjecting the two parts of the beam to fields which would classically cause precessions of π radians in opposite senses. He noted advantages in studying neutral rather than charged particles, and outlined a proposal for an interferometry experiment with neutrons. The recent invention and application of a remarkable single-crystal neutron interferometer greatly increases the feasibility of observing the sign change. In the experiment of Ref. 3 a neutron beam is split, and the two parts follow paths of different elevations. The interference of the recombined parts exhibits the effect of gravitational potential difference between the two elevations. In the experiment which we propose, the paths could be kept at the same elevation, but phase differences would be produced by appropriate magnetic fields.
Abstract Advanced neutron interferometry includes the spinor properties of the neutrons. This makes it necessary to consider the influence of the mirrors on the spinor propagation. It is shown how the effect of an arbitrary mirror can be uniquely decomposed into a known kinematical part which is necessarily present, and a dynamical part which goes back to an interaction the neutron experiences in its rest‐space. For any particular realization of a mirror this dynamical part can be determined experimentally. An argument is given as to why it vanishes for the usual perfect‐crystal interferometer. The first relativistic approximations of the spinor reflection formula are discussed.
The neutron interferometer is a unique instrument that allows one to construct a neutron wave packet of macroscopic size, divide it into two components separated by centimeters, and then coherently recombine them. A number of experiments clearly showing the difference between quantum and classical theory have been performed with it, which are suitable for presentation in elementary quantum courses. This article presents a simple mathematical model of the interferometer, which can be used to illustrate clearly many of the surprising features of quantum systems. For example, one can describe an experiment to determine which component beam the neutron takes (an analog of the two-slit electron experiment). One can then trace in detail the loss of coherence of the wave function, rather than merely invoke the usual "handwaving" uncertainty arguments. The author discusses the effect of gravity on the neutron beam [the classic COW (Colella, Overhauser, and Werner) experiment], including a simple analysis in an accelerated reference frame, and its relation to the equivalence principle, the red shift, and the twin paradox. Also described are the effect of rotation of the neutron by 360\ifmmode^\circ\else\textdegree\fi{} to change its phase, the effect on the wave function of measuring the absence of the particle from a beam ("Dicke's paradox"), and a realizable version of Wheeler's "delayed-choice" experiments, as well as their relation to the problem of "Schr\"odinger's cat." The treatment is suitable for bright undergraduates and first-year graduate students.
The phase shift of matter wave due to the Earth's rotation and gravity has been demonstrated in the neutron-interferometry experiments where the Bragg reflection of the neutron wave from crystals is used to form a closed path. In the literature, the rotation-induced phase shift is ascribed to an extra energy term associated with angular momentum in the Hamiltonian. In this investigation, based on a classical treatment of the collision of neutrons with the lattice planes, the modifications in the particle velocity due to the Earth's rotation as well as those due to gravity are calculated. Then, in conjunction with the relation between the particle velocity and the propagation vector of matter wave, it is shown that the corresponding phase shifts in matter wave are in accord with the interference experiments. Thereby, based on the velocity modification due to collision, a reinterpretation of the effects of the Earth's rotation and gravity on the neutron-wave interference is presented. Meanwhile, a null effect of the Earth's orbital motion is predicted.
A phase shifter in neutron interferometry creates not only a phase shift but also a spatial displacement of the neutron wave packet, leading to a reduced interference contrast. This wave-packet displacement constitutes a major hindrance in measuring large phase shifts. Here we present a nondispersive configuration with two identical phase shifters placed on one path in successive gaps of a symmetric triple Laue (LLL) interferometer. As compared to a single phase shifter, the dual phase shifter generates double the phase shift, yet a net null displacement of the wave packet. The interferometer thus remains fully focused however large the phase shift or the incident wavelength spread, permitting a white incident neutron beam as in the case of a purely topological phase measurement. Misalignment angles of a monolithic nondispersive dual phase shifter are equal and opposite in the two gaps. Its phase therefore remains nondispersive over a much wider angular range and attains a minimum magnitude at the correct orientation, obviating the need to alternate the phase shifter between the two interferometer paths during its alignment. The setup is hence ideally suited for measuring neutron coherent scattering lengths to ultrahigh precision.