Nonclassical correlation in NMR quadrupolar systems

TL;DR

This paper investigates the dynamics of quantum and classical correlations in NMR quadrupolar systems, demonstrating how relaxation affects these correlations through theoretical and experimental analysis, and providing a method for their computation.

Contribution

It introduces a method to compute quantum and classical correlations from NMR deviation-density matrices and analyzes their decay due to environmental relaxation in quadrupolar systems.

Findings

Correlations decay monotonically over time due to relaxation.

The method applies broadly to systems using deviation-density matrices.

Experimental and theoretical results align on correlation decay behavior.

Abstract

The existence of quantum correlation (as revealed by quantum discord), other than entanglement and its role in quantum-information processing (QIP), is a current subject for discussion. In particular, it has been suggested that this nonclassical correlation may provide computational speedup for some quantum algorithms. In this regard, bulk nuclear magnetic resonance (NMR) has been successfully used as a test bench for many QIP implementations, although it has also been continuously criticized for not presenting entanglement in most of the systems used so far. In this paper, we report a theoretical and experimental study on the dynamics of quantum and classical correlations in an NMR quadrupolar system. We present a method for computing the correlations from experimental NMR deviation-density matrices and show that, given the action of the nuclear-spin environment, the relaxation produces a monotonic time decay in the correlations. Although the experimental realizations were performed in a specific quadrupolar system, the main results presented here can be applied to whichever system uses a deviation-density matrix formalism.