Characterizing quantum correlations in spin chains

TL;DR

This paper introduces a method to quantify the quantum nature of spin chains by analyzing single-element density matrices, revealing entanglement and non-locality with implications for quantum technologies.

Contribution

It presents a novel approach to assess quantum correlations in spin chains through single-element density matrix analysis, applicable to ground and thermal states.

Findings

Single-element density matrices encode entanglement and non-locality.

Method applicable to experimentally accessible spin systems.

Potential for tailoring quantum effects in quantum computing and metrology.

Abstract

The growth in the demand for precisely crafted many-body systems of spin-$1/2$ particles/qubits is due to their top-notch versatility in application-oriented quantum-enhanced protocols and the fundamental tests of quantum theory. Here we address the question: how quantum is a chain of spins? We demonstrate that a single element of the density matrix carries the answer. Properly analyzed it brings information about the extent of the many-body entanglement and the non-locality. This method can be used to tailor and witness highly non-classical effects in many-body systems with possible applications to quantum computing, ultra-precise metrology or large-scale tests of quantum mechanics. As a proof of principle, we investigate the extend of non-locality and entanglement in ground states and thermal states of experimentally accessible spin chains.