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arXiv · 1201.6234

Experimental linear-optical implementation of a multifunctional optimal qubit cloner

Karel Lemr·Karol Bartkiewicz·Antonin Cernoch·Jan Soubusta·Adam Miranowicz
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Abstract

We present the first experimental implementation of a multifunctional device for the optimal cloning of one to two qubits. Previous implementations have always been designed to optimize the cloning procedure with respect to one single type of a priori information about the cloned state. In contrast, our "all-in-one" implementation is optimal for several prominent regimes such as universal cloning, phase-covariant cloning, and also the first ever realized mirror phase-covariant cloning, when the square of the expected value of Pauli's Z operator is known in advance. In all these regimes the experimental device yields clones with almost maximum achievable average fidelity (97.5% of theoretical limit). Our device has a wide range of possible applications in quantum information processing, especially in quantum communication. For instance, one can use it for incoherent and coherent attacks against a variety of cryptographic protocols, including the Bennett-Brassard 1984 protocol of quantum key distribution through the Pauli damping channels. It can be also applied as a state-dependent photon multiplier in practical quantum networks.

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Karel Lemr, Karol Bartkiewicz, Antonin Cernoch, Jan Soubusta, Adam Miranowicz. 2012-05-18. Experimental linear-optical implementation of a multifunctional optimal qubit cloner. https://doi.org/10.1103/physreva.85.050307

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