Quantum Correlations in Quantum Cloning

TL;DR

This paper investigates quantum correlations in quantum cloning machines using quantum discord, revealing non-classical correlations can exist without entanglement, thus distinguishing quantum discord from entanglement.

Contribution

It characterizes quantum correlations in a quantum cloning machine using quantum discord, highlighting non-zero discord without entanglement in certain parameter regimes.

Findings

Quantum discord can be non-negative without entanglement.

Non-classical correlations exist in quantum cloning beyond entanglement.

Quantum discord and entanglement are not equivalent.

Abstract

We utilize quantum discord to charecterize the correlation present in Buzek-Hillery quantum copying machine \cite{bh} (not necessarily universal quantum cloning machine). In other words we quantify the correlation present beetween the original and the replicated copy of the quantum state obtained at the outport port, Interestingly, we find some domain of the machine parameter, for which the quantum disord is non negative even in the mere absence of entanglement. These non zero values of the quantum discord is a strong signature for the presence of non classical correlations. This is one step forward evidence in the support of the fact that quantum discord and entanglement are not synonymous.