Inequality relation between entanglement and Bell nonlocality for arbitrary two-qubit states

TL;DR

This paper explores the quantitative relationship between entanglement and Bell nonlocality in two-qubit states, establishing inequality bounds and identifying extremal states through extensive numerical analysis.

Contribution

It introduces a constraint inequality between entanglement and Bell nonlocality for two-qubit states and characterizes extremal states that maximize or minimize Bell nonlocality at fixed entanglement.

Findings

Derived an inequality relation between entanglement and Bell nonlocality.

Identified states that maximize or minimize Bell nonlocality for given entanglement.

Analyzed the relation for a class of mixed states transformed by unitaries.

Abstract

Entanglement and Bell nonlocality are used to describe quantum inseparabilities. Bell-nonlocal states form a strict subset of entangled states. A natural question arises concerning how much territory Bell nonlocality occupies entanglement for a general two-qubit entangled state. In this work, we investigate the relation between entanglement and Bell nonlocality by using lots of randomly generated two-qubit states, and give out a constraint inequality relation between the two quantum resources. For studying the upper or lower boundary of the inequality relation, we discover maximally (minimally) nonlocal entangled states, which maximize (minimize) the value of the Bell nonlocality for a given value of the entanglement. Futhermore, we consider a special kind of mixed state transformed by performing an arbitrary unitary operation on werner state. It is found that the special mixed state's entanglement and Bell nonlocality are related to ones of a pure state transformed by the unitary operation performed on the Bell state.