# Signature of Quantum Entanglement in NH4CuPO4.H2O

## TL;DR

This study detects and analyzes quantum entanglement in the solid state material NH4CuPO4.H2O using experimental magnetic susceptibility and specific heat data, revealing its temperature and field dependence.

## Contribution

It demonstrates a method to detect quantum entanglement in solid state systems through experimental thermodynamic measurements, applying it to NH4CuPO4.H2O.

## Key findings

- Entanglement exists up to a certain critical temperature.
- Entanglement is confirmed via susceptibility and specific heat measures.
- Field-dependent entanglement behavior is characterized.

## Abstract

Entangled solid state systems have gained a great deal of attention due to their fruitful applications in modern quantum technologies. Herein, detection of entanglement content from experimental magnetic susceptibility and specific heat data is reported for NH4CuPO4.H2O in its solid state crystalline form. NH4CuPO4.H2O is a prototype of Heisenberg spin 1/2 dimer system. Temperature dependent magnetic susceptibility and specific data are fitted to an isolated dimer model and the exchange coupling constant is determined. Field dependent magnetization isotherms taken at different temperatures are plotted in a three dimensional plot. Subsequently, entanglement is detected both from susceptibility and specific heat through two different entanglement measures; entanglement witness and entanglement of formation. The temperature evolution of entanglement is studied and the critical temperature is determined up to which entanglement exists. Temperature dependent nature of entanglement extracted from susceptibility and specific heat shows good consistency with each other. Moreover, the field dependent entanglement is also investigated.

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Source: https://tomesphere.com/paper/1906.02769