Fault tolerant quantum dialogue protocol over a collective noise channel

In this paper, we propose two kinds of fault tolerant quantum dialogue (QD) protocols against collective-dephasing noise and collective-rotation noise, respectively. For resisting the collective noise in quantum channels, decoherence-free subspace (DFS) has been constructed with two logical qubits. The combinations of two logical qubits form four kinds of photon quartets depending on the spatial degree of freedom. Both protocols are constructed with photon quartets, which are immune to the collective noise, thereby the protocols can provide higher communication fidelity with respect to the existing QD protocols. Furthermore, we had demonstrated that the protocols can withstand the problem of information leakage and Eve’s active eavesdropping attacks