  We show that the quantum states generated by universal optimal quantum
cloning of a single photon represent an universal set of quantum superpositions
resilient to decoherence. We adopt Bures distance as a tool to investigate the
persistence ofquantum coherence of these quantum states. According to this
analysis, the process of universal cloning realizes a class of quantum
superpositions that exhibits a covariance property in lossy configuration over
the complete set of polarization states in the Bloch sphere.
