Unified Universal Quantum Cloning Machine and Fidelities

TL;DR

This paper introduces a unified quantum cloning machine that consolidates various existing models, simplifies implementation through symmetric projection, and can be adapted for asymmetric cloning with comprehensive fidelity analysis.

Contribution

A novel unified framework for universal quantum cloning machines that simplifies implementation and extends to asymmetric cases with detailed fidelity metrics.

Findings

Unified cloning machine produces identical output states.

Cloning process is simplified via symmetric projection.

Can be modified for asymmetric cloning with arbitrary fidelities.

Abstract

We present a unified universal quantum cloning machine, which combines several different existing universal cloning machines together including the asymmetric case. In this unified framework, the identical pure states are projected equally into each copy initially constituted by input and one half of the maximally entangled states. We show explicitly that the output states of those universal cloning machines are the same. One importance of this unified cloning machine is that the cloning procession is always the symmetric projection which reduces dramatically the difficulties for implementation. Also it is found that this unified cloning machine can be directly modified to the general asymmetric case. Besides the global fidelity and the single-copy fidelity, we also present all possible arbitrary-copy fidelities.