Experimental demonstration of optimal universal asymmetric quantum cloning of polarization states of single photons by partial symmetrization
Antonín Černoch, Jan Soubusta, Lucie Čelechovská, Miloslav Dušek, Jaromı́r Fiurášek · Physical Review A · 2009
We report on experimental implementation of the optimal universal asymmetric $1\ensuremath{\rightarrow}2$ quantum cloning machine for qubits encoded into polarization states of single photons. Our linear-optical machine performs asymmetric cloning by partially symmetrizing the input polarization state of signal photon and a blank copy idler photon prepared in a maximally mixed state. We show that the employed method of measurement of mean clone fidelities exhibits strong resilience to imperfect calibration of the relative efficiencies of single-photon detectors used in the experiment. Reliable characterization of the quantum cloner is thus possible even when precise detector calibration is difficult to achieve.