Inductive van der Waals Force between Two Quantum Loops

TL;DR

This paper investigates the van der Waals-London force between two superconducting loops, revealing a primarily attractive interaction through quantum electrodynamic analysis, and proposes a new experimental platform for measuring such forces in artificial atoms.

Contribution

It introduces a quantum electrodynamic framework for the inductive van der Waals interaction in superconducting loops, highlighting a dominant attractive force and a novel two-photon exchange mechanism.

Findings

QED predicts a predominantly attractive force

Semiclassical model suggests repulsion

Two-photon exchange is key to attraction

Abstract

We study the van der Waals-London force, which is typically associated with fluctuating dipoles in atoms, in a mesoscopic circuit consisting of two inductively coupled superconducting loops. We investigate the ``inductive" van der Waals-London interaction using both semiclassical and quantum electrodynamic (QED) approaches. The semiclassical model predicts a repulsive interaction due to anticorrelated current fluctuations. In contrast, the QED framework, which incorporates virtual photon exchange, reveals a predominantly attractive force. A key contribution comes from a state-independent two-photon exchange, which is absent in the semiclassical description and undetectable by spectroscopy. Our study introduces a new experimental platform for measuring the van der Waals force between individual artificial atoms via controlled mesoscopic circuits.