par Cerf, Nicolas 
Référence Lecture Notes in Computer Science, 1509, page (218-234)
Publication Publié, 1999
Référence Lecture Notes in Computer Science, 1509, page (218-234)
Publication Publié, 1999
Article révisé par les pairs
| Résumé : | An information-theoretic approach to quantum copying is discussed, relying on the notion of quantum loss, a quantity that reflects the transmission quality in a noisy quantum channel. More specifically, an entropic no-cloning inequality is derived for a Hilbert space of arbitrary dimension, which describes the tradeoff between the losses of the channels leading to the two copies. Then, focusing on quantum bits, a family of Pauli cloning machines is introduced. These machines produce two imperfect copies of a single quantum bit that emerge from two distinct Pauli channels. The balance between the quality of the two copies is shown to result from a genuine complementarity principle. In the special probability p and p′, the domain in (√p, √p′-spacelocatedginsideaeparticular ellipse representing close-to-perfect cloning is forbidden. Finally, the class of symmetric Pauli cloning machines is used to provide an upper py and pz. The capacity is proven to be vanishing if (√px, √py, √pz) lies outside an ellipsoid whose pole coincides with the depolarizing channel that underlies the universal cloning machine. |
