Four-level quantum teleportation, swapping and collective translations   of multipartite quantum entanglement
  In this paper, an optimal scheme of four-level quantum teleportation and swapping of quantum entanglement is given. We construct a complete orthogonal basis of the bipartite ququadrit systems. Using this basis, the four-level quantum teleportation and swapping can be achieved according to the standard steps. In addition, associate the above bases with the unextendible product bases and the exact entanglement bases, we prove that in the $2\times 2\times 2$ systems or $3\times 3$ systems the collective translations of multipartite quantum entanglement can be realized.   PACC numbers: 03.67.Mn, 03.65.Ud, 03.67.Hk.   Keywords: Ququadrit systems, Bases, Four-level teleportation, Swapping, Collective translations. 
Zai-Zhe Zhong