文档介绍：arXiv:quant-ph/0309044v1 4 Sep 2003 Orbital angular momentum of the down converted photons Xi-Feng Ren ?, Guo-Ping Guo ?, Bo Yu, Jian Li, and Guang-Can Guo Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei 230026, People’s Republic of China We calculate the relative amplitude of orbital angular mo- mentum(OAM) entangled photon pairs fromthe spontaneous parametric down conversion. The results show that the am- plitude depends on both the two Laguerre indicesl, p. We also discuss the in?uences of the mostly used holograms and mono-mode ?bers for mode analyzation. We conclude that only a few dimensions can be explored from the in?nite OAM modes of the down-converted photon pairs. PACS number(s): , , I. INTRODUCTION Quantum entanglement is a very important property of quantum mechanics. It is the foundation of quantum teleportation [1], putation [2–4], quantum cryptography [5], superdense coding [6], etc. Up to now most of the theoretical discussions and experiments are focused on quantum states belonging to two-dimensional states, or qubits [7–10]. In recent years, the interest in multi-dimensional states, or qudits, is steadily growing for its promise to realize new types of mu- nication protocols [11–13], and its properties in quan- tum cryptography better than qubits [12–15]. These theoretical disscuss