Paper detail

Direct quantum communication without actual transmission of the message qubits

Recently an orthogonal state based protocol of direct quantum communication without actual transmission of particles is proposed by Salih \emph{et al.}{[}Phys. Rev. Lett. \textbf{110} (2013) 170502{]} using chained quantum Zeno effect. As the no-transmission of particle claim is criticized by Vaidman {[}arXiv:1304.6689 (2013){]}, the condition (claim) of Salih \emph{et al.} is weaken here to the extent that transmission of particles is allowed, but transmission of the message qubits (the qubits on which the secret information is encoded) is not allowed. Remaining within this weaker condition it is shown that there exists a large class of quantum states, that can be used to implement an orthogonal state based protocol of secure direct quantum communication using entanglement swapping, where actual transmission of the message qubits is not required. The security of the protocol originates from monogamy of entanglement. As the protocol can be implemented without using conjugate coding its security is independent of non-commutativity.