Quantum Cloning of Continuous Variable Entangled States

TL;DR

This paper introduces two types of entanglement cloning machines for continuous variable states, demonstrating that a global e-cloner better preserves entanglement and fidelity than a local one, using linear optical components.

Contribution

The paper presents a novel implementation of entanglement cloning machines using linear optics and compares their effectiveness in preserving entanglement.

Findings

Global e-cloner outperforms local e-cloner in fidelity and entanglement preservation.

Minimum input entanglement required for the global e-cloner to preserve entanglement.

Implementation using beam splitters, homodyne detection, and squeeze gates.

Abstract

We consider the quantum cloning of continuous variable entangled states. This is achieved by introducing two symmetric entanglement cloning machines (or e-cloners): a local e-cloner and a global e-cloner; where we look at the preservation of entanglement in the clones under the condition that the fidelity of the clones is maximized. These cloning machines are implemented using simple linear optical elements such as beam splitters and homodyne detection along with squeeze gates. We show that the global e-cloner out-performs the local e-cloner both in terms of the fidelity of the cloned states as well as the strength of the entanglement of the clones. There is a minimum strength of entanglement (3dB for the inseparability criterion and 5.7dB for the EPR paradox criterion) of the input state of the global e-cloner that is required to preserve the entanglement in the clones.