# Degenerate detectors are unable to harvest spacelike entanglement

## TL;DR

This paper demonstrates that identical particle detectors in spacelike separation can only harvest entanglement from the vacuum if they have a non-zero energy gap, highlighting the protective role of energy gaps against local noise.

## Contribution

It establishes a general no-go result for degenerate detectors in entanglement harvesting, emphasizing the importance of a non-zero energy gap for entanglement extraction.

## Key findings

- Degenerate detectors cannot effectively harvest entanglement from the vacuum.
- Non-zero energy gaps enable detectors to become entangled through quantum fields.
- Results provide insight into the role of energy gaps in protecting against local noise.

## Abstract

We show, under a very general set of assumptions, that pairs of identical particle detectors in spacelike separation, such as atomic probes, can only harvest entanglement from the vacuum state of a quantum field when they have a non-zero energy gap. Furthermore, we show that degenerate probes are strongly challenged to become entangled through their interaction through scalar and electromagnetic fields even in full light-contact. We relate these results to previous literature on remote entanglement generation and entanglement harvesting, giving insight into the energy gap's protective role against local noise, which prevents the detectors from getting entangled through the interaction with the field.