Abstract: In this paper we introduce a new communication (teleportation) protocol for transferring arbitrary two qubits by using concatenated three particle entangled states as quantum channels which are robust in noisy environments. Due to almost inevitable existence of noise, which can create devastation in the communication systems, such robust quantum channels become necessary. The protocol is a perfect teleportation protocol. An advantage of the process is that only one fourth of the measurement basis elements of the sender appear in the protocol.
In this thesis, we investigate how protocols in quantum communication theory are influenced by noise. Specifically, we take into account noise during the transmission of quantum information and noise during the processing of quantum information. We describe three novel quantum communication protocols which can be accomplished efficiently in a noisy environment: (1) Factorization of Eve: We show that it is possible to disentangle transmitted qubits a posteriori from the quantum channel's degrees of freedom. (2) Cluster state purification: We give multi-partite entanglement purification protocols for a large class of entangled quantum states. (3) Entanglement purification protocols from quantum codes: We describe a constructive method to create bipartite entanglement purification protocols form quantum error correcting codes, and investigate the properties of these protocols, which can be operated in two different modes, which are related to quantum communication and quantum computation protocols, respectively.
We show how noncommuting noises could cause a Bell state ${\ensuremath{\chi}}_{0}$ to suffer entanglement sudden death (ESD). ESD may similarly occur when a noisy operation acts, if the corresponding Hamiltonian and Lindblad operator do not commute. We study the implications of these in special dense coding
S. When noises that cause ESD act, we show that ${\ensuremath{\chi}}_{0}$ may lose its capacity for
S before ESD occurs. Similarly, ${\ensuremath{\chi}}_{0}$ may fail to yield information transfer better than classically possible when the encoding operations are noisy, though entanglement is not destroyed in the process.