• DOI:10.1088/1361-6382/ac1b08
• Corpus ID: 232352419

Weakly coupled local particle detectors cannot harvest entanglement

@article{Ruep2021WeaklyCL,
  title={Weakly coupled local particle detectors cannot harvest entanglement},
  author={Maximilian H Ruep},
  journal={Classical and Quantum Gravity},
  year={2021},
  volume={38}
}

• Maximilian H Ruep
• Published 24 March 2021
• Physics
• Classical and Quantum Gravity

Many states of linear real scalar quantum fields (in particular Reeh–Schlieder states) on flat as well as curved spacetime are entangled on spacelike separated local algebras of observables. It has been argued that this entanglement can be ‘harvested’ by a pair of so-called particle detectors, for example singularly or non-locally coupled quantum mechanical harmonic oscillator Unruh detectors. In an attempt to avoid such imperfect coupling, we analyse a model-independent local and covariant entanglement harvesting protocol based on the local probes of a recently proposed measurement theory of quantum fields. We then introduce the notion of a local particle detector concretely given by a local mode of a linear real scalar probe field on possibly curved spacetime and possibly under the influence of external fields. In a non-perturbative analysis we find that local particle detectors cannot harvest entanglement below a critical coupling strength when the corresponding probe fields are initially prepared in quasi-free Reeh–Schlieder states and are coupled to a system field prepared in a quasi-free state. This is a consequence of the fact that Reeh–Schlieder states restrict to truly mixed states on any local mode.