Entanglement harvesting of three Unruh-DeWitt detectors

TL;DR

This paper investigates how three Unruh-DeWitt detectors can extract tripartite entanglement from a quantum field, revealing configuration-dependent efficiency and conditions for entanglement harvesting, including cases with large spacelike separations.

Contribution

It introduces a detailed analysis of tripartite entanglement harvesting with various detector configurations, highlighting new insights into entanglement distribution and CKW inequality violations.

Findings

More entanglement is harvested in linear configurations than equilateral.

Tripartite entanglement can be harvested at larger spacelike separations.

Bipartite correlations can surpass tripartite ones at small separations, violating CKW inequality.

Abstract

We analyze a tripartite entanglement harvesting protocol with three Unruh-DeWitt detectors adiabatically interacting with a quantum scalar field. We consider linear, equilateral triangular, and scalene triangular configurations for the detectors. We find that, under the same parameters, more entanglement can be extracted in the linear configuration than the equilateral one, consistent with single instantaneous switching results. No bipartite entanglement is required to harvest tripartite entanglement. Furthermore, we find that tripartite entanglement can be harvested even if one detector is at larger spacelike separations from the other two than in the corresponding bipartite case. We also find that for small detector separations bipartite correlations become larger than tripartite ones, leading to an apparent violation of the Coffman-Kundu-Wootters (CKW) inequality. We show that this is not a consequence of our perturbative expansion but that it instead occurs because the harvesting qubits are in a mixed state.