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F. De Martini, G. Milani, S. Giacomini, F. Sciarrino, E. Lombardi.
All these previous quantum state teleportation (QST) realizations nevertheless correspond to simplified, incomplete ''passive'' schemes by which the success of the protocol is demonstrated indirectly by the mere detection of the nonlocal correlations established a posteriori between the extreme stations, Alice and Bob. These passive realizations have the advantage of avoiding the difficult implementation of the final stage of QST i.e. of the unitary transformations U restoring the exact input qubit at Bob's site under Alice's control through the QST local channel. The main problem faced here is due to the relatively long time T needed to switch, under single-photon excitation by the Alice's Bell-measurement apparatus the high-voltage (HV) pulses driving the electro-optic Pockels-cells (EOP) which implement the necessary U-unitaries at Bob's site.
Of course, in order to preserve an appreciable QST fidelity it must be: T<< t, being t the characteristic time of the de-coherence process affecting the nonlocal channel, i.e. the one that dephases the corresponding entangled singlet. The present work realizes for the first time the complete, i.e. active qubit teleportation process by completing the corresponding optical scheme according to the standard QST protocol. As a basic qubit-QST scheme, the vacuum-1 photon configuration was adopted. This scheme provides a discrete variable optical quantum teleportation as complete as possible using linear optics.
Figure 2. Interferometric fringe patterns due to coincidence experiments involving different pairs of detectors within the active QST verification procedure upon variation of the phase j of the measured fields.
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