The Young-Feynman controlled double-slit electron interference experiment

Abstract

The key features of quantum mechanics are vividly illustrated by the Young-Feynman two-slit thought experiment, whose second part discusses the recording of an electron distribution with one of the two slits partially or totally closed by an aperture. Here, we realize the original Feynman proposal in a modern electron microscope equipped with a high brightness gun and two biprisms, with one of the biprisms used as a mask. By exciting the microscope lenses to conjugate the biprism plane with the slit plane, observations are carried out in the Fraunhofer plane with nearly ideal control of the covering of one of the slits. A second, new experiment is also presented, in which interference phenomena due to partial overlap of the slits are observed in the image plane. This condition is obtained by inserting the second biprism between the two slits and the first biprism and by biasing it in order to overlap their images.

Which-way identification by an asymmetrical double-slit experiment with monochromatic photons

“…However, an assessment of the contribution of each component or cannot identify their pure ontological ”which-way”, because, one can never isolate the interference mixing photons passing through one or another slit. Any attempt to label a given slit of a photon path will fail to conserve interference fringes, as happened in the recent double-slit experiments with a Feynman condition 7 , 8 .…”

“…Feynman considered that a double-slit experiment with single electrons using a movable mask for closing or opening one of the slits would serve as a key test of the fundamental problem of physical reality in quantum mechanics 6 . Only recently, based on state-of-the-art electronic microscopy, the so-called Young-Feynman ”thought” double-slit experiments have finally become real 7 , 8 , which seems to confirm the incompatibility of wave and particle features of a quantum substance following the principle of complementarity. Regarding de Broglie-Bohm theory with hidden parameters 9 – 11 , experimental verification of Bell inequality 12 , 13 in the early 1980s denied the local physical reality.…”

Quantum mechanical double slit for molecular scattering

“…One of the earliest and most fundamental demonstrations of quantum mechanical interference was Young's original double-slit experiment with optical waves. Following this, a long series of experiments have been designed that use monoenergetic beams of particles ranging in mass from electrons to large molecules to show matter-wave interferences when the particles pass through two mechanical slits (3)(4)(5)(6). These interferences only appear when the transverse coherence is maintained across both slits either by using a sufficiently large De Broglie wavelength or by restricting the size of the slit that admits the particle beam into the double-slit interferometer.…”

Physical reality in asymmetrical double-slit experiments

“…In a later experiment with low intensity electron beams, one could see self-interference of a single electron [5]. The Feynman thought experiments have recently turned out to be available [6,7], identifying single electrons as particles or waves by intervention of a moving mask opening one or both slits, which seem to reconfirm wave-particle incompatibility in the same measurement. Indeed, the problem of quantum physical reality remains a big puzzle.…”