Quantum cloning of steering

TL;DR

This paper investigates the possibility and limitations of cloning quantum steering, showing that perfect cloning is only possible for states with zero discord and demonstrating EPR steering in cloned states, challenging previous no-cloning claims.

Contribution

It provides a detailed analysis of quantum steering cloning, establishing conditions for perfect cloning and revealing EPR steering in cloned states, contradicting earlier results.

Findings

Perfect cloning only possible for zero discord states

EPR steering observed in cloned subsystems

Contradicts previous no-cloning conclusions based on mutual information

Abstract

Quantum steering in a global state allows an observer to remotely steer a subsystem into different ensembles by performing different local measurements on the other part. We show that, in general, this property cannot be perfectly cloned by any joint operation between a steered subsystem and a third system. Perfect cloning is viable if and only if the initial state is of zero discord. We also investigate the process of cloning the steered qubit of a Bell state using a universal cloning machine. Einstein-Podolsky-Rosen (EPR) steering, which is a type of quantum correlation existing in the states without a local-hidden-state model, is observed in the two copy subsystems. This contradicts the conclusion of no-cloning of quantum steering (EPR steering) [C. Y. Chiu et al., npj Quantum Inf. 2, 16020 (2016)] based on a mutual information criterion for EPR steering.