Cloning transformations in spin networks without external control
- NEST- INFM and Scuola Normale Superiore, piazza dei Cavalieri 7, I-56126 Pisa (Italy)
- INFM and Dipartimento di Fisica 'A. Volta', Via Bassi 6, I-27100 Pavia (Italy)
- NEST-INFM and Dipartimento di Tecnologie dell'Informazione, Universita degli studi di Milano, via Bramante 65, I-26013 Crema, CR (Italy)
In this paper we present an approach to quantum cloning with unmodulated spin networks. The cloner is realized by a proper design of the network and a choice of the coupling between the qubits. We show that in the case of phase covariant cloner the XY coupling gives the best results. In the 1{yields}2 cloning we find that the value for the fidelity of the optimal cloner is achieved, and values comparable to the optimal ones in the general N{yields}M case can be attained. If a suitable set of network symmetries are satisfied, the output fidelity of the clones does not depend on the specific choice of the graph. We show that spin network cloning is robust against the presence of static imperfections. Moreover, in the presence of noise, it outperforms the conventional approach. In this case the fidelity exceeds the corresponding value obtained by quantum gates even for a very small amount of noise. Furthermore, we show how to use this method to clone qutrits and qudits. By means of the Heisenberg coupling it is also possible to implement the universal cloner although in this case the fidelity is 10% off that of the optimal cloner.
- OSTI ID:
- 20718336
- Journal Information:
- Physical Review. A, Vol. 72, Issue 1; Other Information: DOI: 10.1103/PhysRevA.72.012328; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
- Country of Publication:
- United States
- Language:
- English
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