Extremal quantum cloning machines

Journal Article · Sat Oct 15 04:00:00 EDT 2005 · Physical Review. A

DOI:https://doi.org/10.1103/PhysRevA.72.042336· OSTI ID:20718729

Chiribella, G; D'Ariano, G M; Perinotti, P; Cerf, N J ^[1]

---

1. QUIT Quantum Information Theory Group of the INFM, Unita di Pavia and Dipartimento di Fisica 'A. Volta', via Bassi 6, I-27100 Pavia (Italy)

We investigate the problem of cloning a set of states that is invariant under the action of an irreducible group representation. We then characterize the cloners that are extremal in the convex set of group covariant cloning machines, among which one can restrict the search for optimal cloners. For a set of states that is invariant under the discrete Weyl-Heisenberg group, we show that all extremal cloners can be unitarily realized using the so-called double-Bell states, whence providing a general proof of the popular ansatz used in the literature for finding optimal cloners in a variety of settings. Our result can also be generalized to continuous-variable optimal cloning in infinite dimensions, where the covariance group is the customary Weyl-Heisenberg group of displacement000.

• OSTI ID: 20718729
• Journal Information: Physical Review. A, Journal Name: Physical Review. A Journal Issue: 4 Vol. 72; ISSN 1050-2947; ISSN PLRAAN
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
BELL THEOREM
CLONING
CORRELATIONS
ENERGY LEVELS
QUANTUM CRYPTOGRAPHY
QUANTUM MECHANICS
SECRECY PROTECTION