Creating quantum correlations in generalized entanglement swapping

TL;DR

This paper investigates how different quantum measurements in a generalized entanglement swapping protocol can generate, transfer, or destroy various quantum correlations, providing a method to produce diverse correlated states and exploring network nonlocality.

Contribution

It introduces a generalized entanglement swapping framework using POVMs to control quantum correlations and extends the analysis to mixed states and network nonlocality.

Findings

Different POVMs can generate or destroy specific quantum correlations.

The protocol creates families of quantum states with varied correlation properties.

Certain measurements demonstrate or do not demonstrate network nonlocality.

Abstract

We study how different types of quantum correlations can be established as the consequence of a generalized entanglement swapping protocol where starting from two Bell pairs (1, 2) and (3, 4), a general quantum measurement (denoted by a positive operator-valued measure or POVM) is performed on the pair (2, 3), which results in creating quantum correlation in (1, 4) shared between two spatially separated observers. Contingent upon using different kinds of POVMs, we show generation or destruction of different quantum correlations in the pairs (1, 4), (1, 2) and (3, 4). This thus reflects non-trivial transfer of quantum correlations from the pairs (1, 2) and (3, 4) to the pair (1, 4). As an offshoot, this study provides an operational tool to generate different types of single parameter families of quantum correlated states (for example, entangled but not EPR steerable, or EPR steerable but not Bell nonlocal, or Bell nonlocal) by choosing different quantum measurements in the basic entanglement swapping setup. We further extend our study by taking mixed initial states shared by the pairs (1,2) and (3,4). Finally, we study network nonlocality in our scenario. Here, we find out appropriate POVM measurement for which the generated correlation demonstrates/does not demonstrate network nonlocality for the whole range of the measurement parameter.