Optimal mirror phase-covariant cloning

TL;DR

This paper introduces a new quantum cloning machine called mirror phase-covariant cloning, which optimally clones qubits with known expectation value modulus, providing analytical solutions and physical implementation methods.

Contribution

It presents the first analytical derivation of the optimal mirror phase-covariant cloning transformation and fidelity, along with quantum circuit designs and physical realization in quantum-dot systems.

Findings

Analytical expressions for cloning transformation and fidelity.

Derivation of extremal equations for optimal cloning.

Quantum circuit implementation and physical realization in quantum-dot systems.

Abstract

We propose a quantum cloning machine, which clones a qubit into two clones assuming known modulus of expectation value of Pauli Z-matrix. The process is referred to as the mirror phase-covariant cloning, for which the input state is a priori less known than that for the standard phase-covariant cloning. Analytical expressions describing the cloning transformation and fidelity of the clones are found. Extremal equations for the optimal cloning are derived and analytically solved by generalizing a method of Fiurasek [Phys. Rev. A 64, 062310 (2001)]. Quantum circuits implementing the optimal cloning transformation and their physical realization in a quantum-dot system are described.