Abstract We investigate the possibility that idealized quantum state-reduction processes may produce a local violation of charge conservation. If this occurs, the corresponding electromagnetic fields cannot be consistently described within Maxwell electrodynamics, and a natural alternative is provided by Aharonov–Bohm electrodynamics, which reduces to Maxwell theory when local charge conservation holds, but remains compatible with non-conserved sources. Within this framework, we first analyze how state reduction may generate non-conserved local currents, including statistically compensated cases and biased tunneling configurations with persistent average current. We then study the interaction of gauge waves with fermionic and bosonic quantum systems, the latter being described by a modified Schrödinger equation previously proposed for boson matter. As an application, we discuss the interaction of gauge waves with superconductors and show that they can effectively shield such waves. Finally, we present experimental proposals based on inverse-biased diodes and estimate the expected detector response.
Marletto and Vedral [Phys. Rev. Lett. 125, 040401 (2020)] propose that the Aharonov-Bohm (AB) phase is locally mediated by entanglement between a charged particle and the quantized electromagnetic field, asserting gauge independence for non-closed paths. In this Comment, we critically analyze their model and demonstrate that the AB phase arises from the interaction with the vector potential
A, not from entanglement, which is a byproduct of the quantum electrodynamics (QED) framework. We show that their field-based energy formulation, intended to reflect local electromagnetic interactions, is mathematically flawed due to an incorrect prefactor and yields
+qv⋅As in the Coulomb gauge, conflicting with QED's
−qv⋅As. This equivalence to
qv⋅As holds only approximately in the Coulomb gauge under static conditions, failing for time-dependent fields and other gauges, undermining their claim of a gauge-independent local mechanism. Furthermore, we confirm that the AB phase is gauge-dependent for non-closed paths, contradicting their assertion. Our analysis reaffirms the conventional explanation in the semi-classical picture, where the AB phase is driven by the vector potential
A, with entanglement playing no causal role in its generation.
The simplest model for superconductor electrodynamics are the London equations, which treats the impact of electromagnetic fields on the current density as a localized phenomenon. However, the charge carriers of superconductivity are quantum mechanical objects, and their wavefunctions are delocalized within the superconductor, leading to non-local effects. The Pippard equation is the generalization of London electrodynamics which incorporates this intrinsic non-locality through the introduction of a new superconducting characteristic length, \xi_0, called the Pippard coherence length. When building nano-scale superconducting devices, the inclusion of the coherence length into electrodynamics calculations becomes paramount. In this thesis, we provide numerical calculations of various electrodynamic quantities of interest in the non-local regime, and discuss their implications for building superconducting devices. We place special emphasis on Superconducting QUantum Inteference Devices (SQUIDs), and their usage as flux quantum bits (qubits) in quantum computation. One of the main limitations of these flux qubits is the presence of intrinsic flux noise, which leads to decoherence of the qubits. Although the origin of this flux noise is not known, there is evidence that it is related to spin impurities within the superconducting material. We present calculations which show that the flux noise in the non-local regime is signi cantly different from the local case. We also demonstrate that non-local electrodynamics greatly affect the self-inductance of the qubit.