# All coherent field states entangle equally

## TL;DR

This paper demonstrates that particle detectors interacting with any coherent state of a scalar field harvest the same entanglement as with the vacuum, showing equal entanglement potential across all coherent states.

## Contribution

It reveals that the entanglement harvested by detectors is independent of the specific coherent state of the field, a novel insight into quantum field interactions.

## Key findings

- Eigenvalues of post-interaction density matrices are field-state independent.
- Detectors harvest equal entanglement from any coherent state and the vacuum.
- Entanglement extraction does not depend on the specific coherent state.

## Abstract

We analyze the interactions of particle detectors with coherent states of a free scalar field. We find that the eigenvalues of the post-interaction density matrices of i) a single detector, ii) two detectors, and iii) the partial transpose of the latter, are all independent of which coherent state the field was in. A consequence of these results is that a detector pair can harvest the same amount of entanglement from any coherent field state as from the vacuum.