Molecular Nanomagnet $\text{Cu}^\text{II}\text{Ni}^\text{II}\text{Cu}^\text{II}$ as Resource for Bipartite and Tripartite Quantum Entanglement and Coherence

TL;DR

This study analyzes the quantum entanglement and coherence properties of a specific molecular nanomagnet modeled as a mixed spin Heisenberg trimer, demonstrating its potential as a quantum resource at relatively high temperatures and magnetic fields.

Contribution

It provides the first detailed analysis of bipartite and tripartite entanglement in a real molecular nanomagnet with mixed spins, combining analytical and numerical methods.

Findings

Significant bipartite entanglement persists up to 37 K.

Robust tripartite entanglement remains at high magnetic fields.

Coherence is maintained at elevated temperatures.

Abstract

We investigate key quantum characteristics of the mixed spin-(1/2,1,1/2) Heisenberg trimer under the influence of an external magnetic field. Specifically, we analyze the distributions of bipartite and tripartite entanglement quantified through the respective negativities, and the $l_1$-norm of coherence with the help of rigorous analytical and numerical methods. Our findings suggest that the heterotrinuclear molecular nanomagnet $[\{\text{Cu}^\text{II}\text{L}\}_2\text{Ni}^\text{II}(\text{H}_2\text{O})_2](\text{ClO}_4)_{2} . 3\text{H}_2\text{O}$, which represents an experimental realization of the mixed spin-(1/2,1,1/2) Heisenberg trimer, exhibits a significant bipartite entanglement between $\text{Cu}^\text{II}$ and $\text{Ni}^\text{II}$ magnetic ions along with robust tripartite entanglement among all three constituent $\text{Cu}^\text{II}\text{Ni}^\text{II}\text{Cu}^\text{II}$ magnetic ions. The significant bipartite and tripartite entanglement persists even at relatively high temperatures up to $37\,\text{K}$ and magnetic fields up to $46\,\text{T}$, whereby the coherence is maintained even at elevated temperatures. {It is evidenced that the aforementioned molecular complex with the magnetic core $\text{Cu}^\text{II}\text{Ni}^\text{II}\text{Cu}^\text{II}$ provides an intriguing quantum resource, which exhibits a star-shaped state within the singlet eigenstate at low magnetic fields and W-like state within the triplet eigenstate at moderate magnetic fields.