In a microscopic quantum system one cannot perform a simultaneous measurement of particle and wave properties. This, however, may not be true for macroscopic quantum systems. As a demonstration, we propose to measure the local macroscopic current passed through two slits in a superconductor. According to the theory based on the linearized Ginzburg–Landau equation for the macroscopic pseudo wave function, the streamlines of the measured current should have the same form as particle trajectories in the Bohmian interpretation of quantum mechanics. By an explicit computation we find that the streamlines should show a characteristic wiggling, which is a consequence of quantum interference.
In a microscopic quantum system one cannot perform a simultaneous measurement of particle and wave properties. This, however, may not be true for macroscopic quantum systems. As a demonstration, we propose to measure the local macroscopic current passed through two slits in a superconductor. According to the theory based on the linearized Ginzburg–Landau equation for the macroscopic pseudo wave function, the streamlines of the measured current should have the same form as particle trajectories in the Bohmian interpretation of quantum mechanics. By an explicit computation we find that the streamlines should show a characteristic wiggling, which is a consequence of quantum interference.
The Bohm’s quantum potential, introduced in 1952, and the quantum force in superconductor, introduced in 2001, allow to describe non‐local force‐free momentum transfer observed in the Ahronov‐Bohm effects. Comparison of the Ahronov‐Bohm effects in the two‐slit interference experiment and in superconductor ring reveals fundamental difference between the Schrodinger wave function and the wave function describing macroscopic quantum phenomena. The Ginzburg‐Landau wave function describing the superconductivity phenomenon can not collapse and an additional postulate, which was implied first by L.D. Landau, must be used for the description of macroscopic quantum phenomena. It is note that quantum principles and postulates should not be universal till the quantum formalism is only phenomenological theory but no description of an unique reality.
The double-slit experiment has stood for a century as the paradigmatic demonstration of quantum superposition: the standard interpretation holds that a particle passes through both slits simultaneously, existing in a superposition of two spatially separated states. This paper proposes a physically distinct alternative: the particle's matter wave — a real physical wave propagating through space in accordance with de Broglie's relation λ = h/p — passes through both slits, while the particle itself (matter) remains in an undetermined state until a constructive interference maximum is formed at the detection screen. The particle does not simultaneously occupy two locations; the wave does. This distinction eliminates the need for superposition as an ontological commitment while fully reproducing the observed interference pattern. We further show that the disappearance of the interference pattern upon which-path measurement is explained without invoking wavefunction collapse: the measurement interaction redirects the matter wave to a single-slit geometry, eliminating the two-wave interference condition. Three experimentally testable predictions distinguish this framework from the standard interpretation: (1) weak-measurement trajectory reconstruction should reveal single particle paths inconsistent with simultaneous two-slit passage; (2) diffraction fringe spacing should depend on the mass density of the slit material, because denser slit edges generate a steeper refractive-index gradient for the matter wave; (3) the fringe pattern should exhibit a density-dependent phase shift measurable with current matter-wave interferometry technology. This reinterpretation requires no new mathematical formalism — the Schrödinger equation and Born's rule are retained — but replaces the ontological claim of simultaneous multi-location existence with the physically consistent picture of matter-wave propagation through an undetermined-state particle.
]. We rise to the challenge with an alternative to the wave function-centered interpretations: instead of a quantum wave passing through both slits, we have a localized particle with nonlocal interactions with the other slit. Key to this explanation is dynamical nonlocality, which naturally appears in the Heisenberg picture as nonlocal equations of motion. This insight led us to develop an approach to quantum mechanics which relies on pre- and postselection, weak measurements, deterministic, and modular variables. We consider those properties of a single particle that are deterministic to be primal. The Heisenberg picture allows us to specify the most complete enumeration of such deterministic properties in contrast to the Schrödinger wave function, which remains an ensemble property. We exercise this approach by analyzing a version of the double-slit experiment augmented with postselection, showing that only it and not the wave function approach can be accommodated within a time-symmetric interpretation, where interference appears even when the particle is localized. Although the Heisenberg and Schrödinger pictures are equivalent formulations, nevertheless, the framework presented here has led to insights, intuitions, and experiments that were missed from the old perspective.
This work proposes a novel variation of the double-slit experiment in which two different types of quantum particles — for example, electrons and photons — pass simultaneously through a shared double-slit apparatus. The primary objective is to test the hypothesis that the act of measurement may not only collapse the wave function of the observed particle, but could also influence the interference pattern of an unmeasured, co-propagating particle of a different type. In the proposed configuration, photons and electrons are emitted in synchrony and directed through the same set of slits. Immediately after the slits, a path-detecting measurement apparatus is applied only to one type of particle (e.g., photons), while the interference pattern of the other type (e.g., electrons) is recorded on a distant screen. The experiment is designed to explore whether the destruction of coherence through measurement is strictly local, or whether it can propagate to other particles through a shared medium, entangled fields, or an unknown interaction. If the unmeasured particle continues to display interference, this would support the locality of measurement effects. Conversely, if interference vanishes for both, it could indicate a more global or field-level decoherence process. This investigation aims to contribute new insights into the nature of quantum measurement, the role of observation, and the interdependence of coherent systems involving distinct particle species.
In this thesis we will describe theoretically a current in a superconductor on the basis of phenomenological Ginzburg-Landau equation. We will show that, in a suitable approximation, current streamlines have the same form as the Bohmian trajectories of the point-like current-carriers. Although Heisenberg inequalities prevents us from directly measuring these trajectories, we can use a Hall probe to measure a current in a superconductor and arrive at the measurements which are, in a way, averaged over a large number of particles. The experiment is envisioned on a planar superconductor having a barrier and two slits. In this case both wave and particle properties are clearly present, i.e. intereference which is manifested in particle trajectories. By measuring these quantities it would be seen how a macroscopic current exibits wave-particle properties and we would thus acquire an additional confirmation that the concept of Bohmian trajectories is not merely a hyphotethical one, but that they are, in some sense, measurable in a laboratory.
Abstract Superconducting quantum interference devices (SQUIDs) are made by a superconducting loop interrupted by one or more Josephson junctions. They are described in terms of a macroscopic variable, the magnetic flux, which shows quantum effects such as tunnelling through a potential barrier. Besides making up the source of a quantum state, SQUIDs also provide the instruments necessary for its probing: as a fact, SQUID based magnetometers have a sensitivity approaching the quantum limit. In this paper I will review the working principle of these devices and illustrate the system of SQUIDs realized in my group to test the quantum behavior at a macroscopic level.