  No-cloning theorem forbids perfect cloning of an unknown quantum state. A
universal quantum cloning machine (UQCM), capable of producing two copies of
any input qubit with the optimal fidelity, is of fundamental interest and has
applications in quantum information processing. This is enabled by delicately
tailored nonclassical correlations between the input qubit and the copying
qubits, which distinguish the UQCM from a classical counterpart, but whose
experimental demonstrations are still lacking. We here implement the UQCM in a
superconducting circuit, and investigate these correlations. The measured
entanglements well agree with our theoretical prediction that they are
independent of the input state and thus constitute a universal quantum behavior
of the UQCM that was not previously revealed. Another feature of our experiment
is the realization of deterministic and individual cloning, in contrast to
previously demonstrated UQCMs, which either were probabilistic or did not
constitute true cloning of individual qubits.
