On the size of linear superpositions in molecular nanomagnets

TL;DR

This paper quantifies the size of quantum superpositions in molecular nanomagnets, revealing how they can be increased and addressing their micro or macroscopic nature, with implications for quantum information processing.

Contribution

It introduces measures for superposition size in nanomagnets and explores criteria for enhancing these sizes, including specific analysis of Mn12, Fe8, Cr7Ni, and V15 molecules.

Findings

Superposition sizes vary across different nanomagnets.

Criteria for increasing superposition sizes are proposed.

Superpositions in low-spin systems are larger than a single spin but not proportional to total spins.

Abstract

Molecular nanomagnets are zero-dimensional spin systems, that exhibit quantum mechanical behavior at low temperatures. Exploiting quantum-information theoretic measures, we quantify here the size of linear superpositions that can be generated within the ground multiplet of high- and low-spin nanomagnets. Amongst the former class of systems, we mainly focus on Mn12 and Fe8. General criteria for further increasing such sizes are also outlined, and illustrated in the case of spin rings. The actual character (micro or macroscopic) of linear superpositions in low-spin systems is inherently ill-defined. Here, this issue is addressed with specific reference to the Cr7Ni and V15 molecules, characterized by an S=1/2 ground state. In both cases, the measures we obtain are larger than those of a single s=1/2 spin, but not proportionate to the number and value of the constituent spins.