Quantum Correlations in NMR systems

TL;DR

This paper explores nonclassical quantum correlations like contextuality, Leggett-Garg correlations, and quantum discord in NMR systems, despite their low polarization and lack of entanglement, supported by theoretical and experimental insights.

Contribution

It identifies and discusses three types of quantum correlations observable in NMR systems, expanding understanding beyond entanglement in such low-purity states.

Findings

Quantum contextuality observed in NMR experiments.

Leggett-Garg correlations demonstrated in NMR systems.

Quantum discord present despite low polarization.

Abstract

In conventional NMR experiments, the Zeeman energy gaps of the nuclear spin ensembles are much lower than their thermal energies, and accordingly exhibit tiny polarizations. Generally such low-purity quantum states are devoid of quantum entanglement. However, there exist certain nonclassical correlations which can be observed even in such systems. In this chapter, we discuss three such quantum correlations, namely, quantum contextuality, Leggett-Garg temporal correlations, and quantum discord. In each case, we provide a brief theoretical background and then describe some results from NMR experiments.