Cloning of Quantum Entanglement

TL;DR

This paper reports the first experimental demonstration of quantum cloning of entangled photon pairs, showing that a maximally entangled pair can be broadcast into two entangled pairs with fidelities above 50%, advancing quantum information science.

Contribution

It presents the first experimental realization of quantum cloning of entanglement using a multiphoton linear optics platform, demonstrating the feasibility of cloning complex quantum systems.

Findings

Successfully cloned entangled photon pairs with fidelities above 50%

Demonstrated broadcasting of a maximally entangled pair into two entangled pairs

Provided new insights into quantum entanglement and cloning capabilities

Abstract

Quantum no-cloning, the impossibility of perfectly cloning an arbitrary unknown quantum state, is one of the most fundamental limitations due to the laws of quantum mechanics, which underpin the physical security of quantum key distribution. Quantum physics does allow, however, approximate cloning with either imperfect state fidelity and/or probabilistic success. Whereas approximate quantum cloning of single-particle states has been tested previously, experimental cloning of quantum entanglement -- a highly non-classical correlation -- remained unexplored. Based on a multiphoton linear optics platform, we demonstrate quantum cloning of two photon entangled states for the first time. Remarkably our results show that one maximally entangled photon pair can be broadcast into two entangled pairs, both with state fidelities above 50\%. Our results are a key step towards cloning of complex quantum systems, and are likely to provide new insights into quantum entanglement.