Three-particle QKD protocol against a collective noise

The research on decoherence-free subspace has both theoretical and practical significance. DFS is a subspace of quantum system states which is robust against a specific form of decoherence. The method of constructing DFS based algebra, which is different from the way based on the special Bell states, is introduced. Then a three-particle QKD protocol against collective-bit flipping noise is presented according to this method. Finally, we make a security analysis of our protocol.