Detector Based Evaluation of Extractable Entanglement in Flat spacetime

TL;DR

This paper investigates the physically extractable entanglement in quantum fields using Unruh-DeWitt detectors, revealing that the operationally accessible entanglement diverges more slowly than the total entanglement entropy predicted by conformal field theory.

Contribution

It introduces an operational approach to measure extractable entanglement in quantum fields and establishes an upper bound scaling as a double logarithm of the UV cutoff.

Findings

Upper bound on extractable entanglement derived

Scaling of extractable entanglement is double logarithmic

Operational limits on entanglement extraction established

Abstract

Entanglement entropy (EE) is widely used to quantify quantum correlations in field theory, with the well-known result in two-dimensional conformal field theory (CFT) predicting a logarithmic divergence with the ultraviolet (UV) cutoff. However, this expression lacks operational meaning: it remains unclear how much of the entanglement is physically extractable via local measurements. In this work, we investigate the operationally accessible entanglement by employing a pair of Unruh-DeWitt detectors, each interacting with complementary regions of a quantum field. We derive an upper bound on the entanglement that can be harvested by such detectors and show that it scales as a double logarithm with respect to the UV cutoff-significantly weaker than the single-logarithmic divergence of the standard CFT result. This work provides an operational perspective on field-theoretic entanglement and sets fundamental limits on its extractability.