Fate of multiparticle entanglement when one particle becomes classical

TL;DR

This paper investigates how multiparticle entanglement changes when one particle is measured and effectively becomes classical, providing bounds and conditions for entanglement preservation or loss, with implications for quantum resource management.

Contribution

It introduces new bounds and analysis methods for understanding entanglement change during classicalization of a particle, advancing quantum resource theory.

Findings

Entanglement change can be arbitrarily large when one qubit becomes classical.

Provided bounds on entanglement variation during classicalization.

Identified cases with no residual entanglement after classicalization.

Abstract

We study the change of multiparticle entanglement if one particle becomes classical, in the sense that this particle is destructed by a measurement, but the gained information is encoded into a new register. We present an estimation of this change for different entanglement measures and ways of encoding. We first simplify the numerical calculation to analyze the change of entanglement under classicalization in special cases. Second, we provide general upper and lower bounds on the entanglement change. Third, we show that the entanglement change caused by classicalization of one qubit only can still be arbitrarily large. Finally, we discuss cases where no entanglement is left under classicalization for any possible measurement. Our results shed light on the storage of quantum resources and help to develop a novel direction in the field of quantum resource theories.