Sustainable entanglement production from a quantum field

TL;DR

This paper introduces a protocol called entanglement farming, where unentangled particles repeatedly interact with a quantum field in a cavity, leading to a stable entangled state suitable for experimental realization.

Contribution

It demonstrates a non-perturbative method for entanglement harvesting that drives the cavity towards a stable entangled state, enabling reliable entanglement production in quantum systems.

Findings

The cavity reaches a non-thermal metastable state facilitating entanglement.

Successive particles emerge significantly entangled after multiple interactions.

The fixed point state is largely independent of initial cavity conditions.

Abstract

We propose a protocol by which entanglement can be extracted repeatedly from a quantum field. In analogy with prior work on entanglement harvesting, we call this protocol entanglement farming. It consists of successively sending pairs of unentangled particles through an optical cavity. Using non-perturbative Gaussian methods, we show that in certain generic circumstances this protocol drives the cavity field towards a non-thermal metastable state. This state of the cavity is such that successive pairs of unentangled particles sent through the cavity will reliably emerge significantly entangled. We calculate thermodynamic aspects of the harvesting process, such as energies and entropies, and also the long-term behavior beyond the few-mode approximation. Significant for possible experimental realizations is the fact that this entangling fixed point state of the cavity is reached largely independently of the initial state in which the cavity was prepared. Our results suggest that reliable entanglement farming on the basis of such a fixed point state should be possible also in various other experimental settings, namely with the to-be-entangled particles replaced by arbitrary qudits and with the cavity replaced by a suitable reservoir system.