[1] Natl Res Council CNR, Natl Inst Opt INO, Largo Enrico Fermi 6, I-50125 Florence, Italy
[2] Univ Florence, Natl Inst Nucl Phys INFN, Dept Phys & Astron, Via Sansone 1, I-50019 Sesto Fiorentino, FI, Italy
[3] Czech Acad Sci, Inst Informat Theory & Automat, Pod Vodarenskou Vezi 4, Prague 18208, Czech Republic
[4] Opificio Pietre Dure Firenze, Florence, Italy