Contextual, Optimal, and Universal Realization of the Quantum Cloning Machine and of the NOT Gate
F. De Martini, Daniele Pelliccia, Fabio Sciarrino · Physical Review Letters · 2004
A simultaneous realization of the universal optimal quantum cloning machine and of the universal-NOT gate by a quantum injected optical parametric amplification, is reported. The two processes, forbidden in their exact form for fundamental quantum limitations, are found universal and optimal, and the measured fidelity F<1 is found close to the limit values evaluated by quantum theory. This work may enlighten the yet little explored interconnections of fundamental axiomatic properties within the deep structure of quantum mechanics.