Quantum optics cryptography

Due to an increasing number of applications, from quantum optics, quantum cryptography and the realization of quantum optical gates, significant efforts have been expended recently in the development of new and reliable single-... 

The quantized nature of the field and its fundamental interaction with atoms lead to many further interesting non-classical phenomena, which are treated in a field generally referred to as quantum optics [4.20- -4.28]. The field also comprises emerging practical applications such as quantum computing and quantum cryptography. 

Approximate versions of the translational EPR state, wherein the -function correlations are replaced by finite-width (Gaussian) distributions, have been shown to characterize the quadratures of the two optical-field outputs of parametric down-conversion, or of a fiber interferometer with Kerr nonlinearity. Such states allow for various schemes of continuous-variable quantum information processing such as quantum teleportation [Braunstein 1998 (b) Furu-sawa 1998] or quantum cryptography [Silberhorn 2002], A similar state has also been predicted and realized using collective spins of large atomic samples [Polzik 1999 Julsgaard 2001]. It has been shown that if suitable interaction schemes can be realized, continuous-variable quantum states of the original EPR type could even serve for quantum computation. 

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