Double well potentials with a quantum moat barrier or a quantum wall barrier give rise to similar entangled wave functions

TL;DR

This paper demonstrates that double well potentials with either a quantum moat or wall barrier produce similar entangled wave functions, extending the understanding of superposition in quantum systems with different barrier types.

Contribution

It introduces the concept that attractive potentials like a quantum moat can create superposition states similar to traditional repulsive double wells, using historical concepts like orthogonalized plane waves.

Findings

Both moat and wall barriers lead to superposition of localized states.

The effective low-energy model describes entangled states in both potential types.

Historical concepts like pseudopotentials help explain these phenomena.

Abstract

The solution to a problem in quantum mechanics is generally a linear superposition of states. The solutions for double well potentials epitomize this property, and go even further than this: they can often be described by an effective model whose low energy features can be described by two states --- one in which the particle is on one side of the barrier, and a second where the particle is on the other side. Then the ground state remains a linear superposition of these two macroscopic-like states. In this paper we illustrate that this property is achieved similarly with an attractive potential that separates two regions of space, as opposed to the traditionally repulsive one. In explaining how this comes about we revisit the concept of "orthogonalized plane waves," first discussed in 1940 to understand electronic band structure in solids, along with the accompanying concept of a pseudopotential. We show how these ideas manifest themselves in a simple double well potential, whose "barrier" consists of a moat instead of the conventional wall.