Distinct single-photon blockades based on topological edge states and bulk states in a dimer chain

Topological photonics, combining the advantages of topological properties with those of optical systems, is anticipated to be significant for various applications. However, how to leverage its benefits for realizing single-photon blockade (PB) remains rarely studied. Here, we propose schemes to generate single PBs in a dimer chain featuring multiple qubits and a two-photon Jaynes-Cummings interaction. We demonstrate that with specific intracell and intercell hopping amplitudes of the lattice, the quantum level lattices are characterized by the form of a one-dimensional array with topological edge states in both two-excitation and three-excitation spaces, resulting in suppressed two-photon excitations and enhanced single-photon excited states. This further leads to a remarkable single PB effect under the resonance-driven case. Interestingly, single PBs can be observed in the off-resonance scenario under coupling strengths with opposite trends, while satisfying that two-excitation and three-excitation transitions are resonant whereas single-photon transition is detuned. We refer to this as an abnormal mechanism compared to previous regimes. Moreover, we show the superiority of the multiqubit-cavity topological chain by comparing with scenarios with different numbers of qubits. Our study not only sheds light on the generation of the single PB effect based on an abnormal mechanism but also establishes a pathway for realizing quantum blockade in topological optical systems, with potential applications in quantum information processing and quantum communication.