Experimental reversion of the optimal quantum cloning and flipping processes

The quantum cloner machine maps an unknown arbitrary input qubit into two optimal clones and one optimal flipped qubit. By combining linear and non-linear optical methods we experimentally implement a scheme that, after the cloning transformation, restores the original input qubit in one of the output channels, by using local measurements, classical communication and feedforward. This significant teleportation-like method demonstrates how the information is preserved during the cloning process. The realization of the reversion process is expected to find useful applications in the field of modern multi-partite quantum cryptography. Typeset using REVTEX 1 The conservation of information can be assumed as a basic principle of physics [1]. Accordingly, since two perfect copies of an unknown arbitrary quantum state |φ〉 carry more information than the latter one, it is impossible to realize a perfect quantum cloning machine [2]. On the same token, since more information about |φ〉 can be extracted from a pair of two orthogonal qubits |φ〉 ∣