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Optimal quantum machines by linear and non‐linear optics
Author(s) -
Sciarrino F.,
De Martini F.
Publication year - 2004
Publication title -
fortschritte der physik
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.469
H-Index - 71
eISSN - 1521-3978
pISSN - 0015-8208
DOI - 10.1002/prop.200410177
Subject(s) - quantum information , quantum error correction , quantum cloning , quantum network , computer science , quantum teleportation , quantum , quantum mechanics , physics , qubit , quantum entanglement , quantum channel , no teleportation theorem , quantum technology , topology (electrical circuits) , open quantum system , mathematics , combinatorics
Abstract Since manipulations of qubits are constrained by the quantum mechanical rules, several classical information tasks can not be perfectly extended to the quantum world. The more relevant limitations in quantum information processing are the impossibility to perfectly clone any unknown qubit and to map it in its orthogonal state. Even if these two processes are unrealizable in their exact forms, they can be optimally approximated by the so‐called universal quantum machines: the optimal quantum cloning machine (UOQCM) and the universal‐NOT (U‐NOT) gate. Investigation of these optimal transformations is important since it reveals bounds on optimal manipulations of information with quantum systems. The 1−>1 U‐NOT gate and the 1−>2 UOQCM have been experimentally demonstrated by adopting the process of stimulated emission into an optical parametric amplifier and by slightly modifying the quantum state teleportation protocol.