On the Phase Covariant Quantum Cloning

Abstract

It is known that in phase covariant quantum cloning the equatorial states on the Bloch sphere can be cloned with a fidelity higher than the optimal bound established for universal quantum cloning. We generalize this concept to include other states on the Bloch sphere with a definite $z$ component of spin. It is shown that once we know the $z$ component, we can always clone a state with a fidelity higher than the universal value and that of equatorial states. We also make a detailed study of the entanglement properties of the output copies and show that the equatorial states are the only states which give rise to separable density matrix for the outputs.

Revtex4, 6 pages, 5 eps figures

References in corpus (5)

• Experimental Quantum Cloning of Single Photons
• Approximate Quantum Cloning with Nuclear Magnetic Resonance
• Phase-covariant quantum cloning of qudits
• Quantum cloning with an optical fiber amplifier
• How the no-cloning theorem got its name

Cited by in corpus (12)

• Quantum Cloning Machines and the Applications
• Experimental Quantum Cloning with Prior Partial Information
• Experimental quantum forgery of quantum optical money
• Separability in Asymmetric Phase-Covariant Cloning
• Phase-covariant cloning of coherent states
• Quantum-phase synchronization
• Temperature effects on quantum cloning of states and entanglement
• General quantum phase estimation and calibration of a timepiece in a quantum dot system
• Asymmetric universal entangling machine
• Photonic quantum simulator for unbiased phase covariant cloning
• Process-optimized phase covariant quantum cloning
• Single Qubit Multi-Party Transmission Using Universal Symmetric Quantum Cloning