Measurements in QFT: Weakly coupled local particle detectors and entanglement harvesting

We present a comparison of the AQFT-based Fewster-Verch framework with the Unruh-DeWitt particle detector models commonly employed in relativistic quantum information and QFT in curved space. We use this comparison to respond to a recent paper [M. H. Ruep, Weakly coupled local particle detectors cannot harvest entanglement, arXiv:2103.13400.] in which it was argued that the Reeh-Schlieder theorem prevents weakly coupled local particle detectors from harvesting vacuum entanglement from a quantum field. Their claim can be traced back to the mixedness that a local particle detector cannot escape from because of the entanglement that it must have with the quantum fields outside of the localization area. We argue that for any realistic scale of localization for physical particle detectors, the effect of that mixedness is negligible, and that weakly coupled, localized particle detectors are not impeded from harvesting vacuum entanglement.

Automated summary

In this work, we compare the AQFT-based Fewster-Verch framework with the commonly used Unruh-DeWitt particle detector models in relativistic quantum information and QFT in curved space. We argue that weakly coupled, localized particle detectors are not impeded from harvesting vacuum entanglement despite claims in a recent paper. The mixedness resulting from entanglement with quantum fields outside the localization area is deemed negligible for realistic scales of localization for physical particle detectors.