Experimental demonstration of entanglement-enabled universal quantum cloning in a circuit

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