Entangled states of the W-class are considered as a quantum channel for teleportation or the states to be sent. The protocols have been found by unitary transformations of the schemes, based on the multiuser GHZ channel. The main feature of the W-quantum channels is a set of non-local operators, that allow receivers recovering unknown state.

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Large number of multimode entangled states of light generated in down conversion processes belongs to a collection which is natural generalization of the W ‐class. A brief overview of these states, schemes for their preparation, experimental implementations and possible applications are presented. (© 2006 by Astro, Ltd. Published exclusively by WILEY‐VCH Verlag GmbH & Co. KGaA)

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A scheme, where three atomic ensembles can be prepared in the states of the W-class via Raman type interaction of strong classical field and a projection measurement involved three single-photon detectors and two beamsplitters, are considered. The obtained atomic entanglement consists of the Dicke or W-states of each of the ensembles.

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Collective operators corresponding to two different algebras have been introduced for a simple system con sisting of a single two level atom and a high quality cavity mode. The generators of the first algebra satisfy boson commutation relations, whereas the generators of the second algebra have been obtained by polyno mial deformation of su(2) algebra. It has been shown that dual squeezed states identified using the considered commutation relations can be observed in the system placed in an entangled bath with quantum correlations.

A set of protocols for teleportation and dense coding schemes based on a multiparticle quantum channel, represented by the $N$-particle entangled states of the GHZ class, is introduced. Using a found representation for the GHZ states, it was shown that for dense coding schemes enhancement of the classical capacity of the channel due from entanglement is $N/N-1$. Within the context of our schemes it becomes clear that there is no one-to one correspondence between teleportation and dense coding schemes in comparison when the EPR channel is exploited. A set of schemes, for which two additional operations as entanglement and disentanglement are permitted, is considered.