Second-order correlation function,, calculated with a weak incident coherent state for spacing. First row is for transmitted photons, second row for reflected photons. The columns correspond to qubits coupled to the waveguide. The photon frequency is chosen so that . The result for uncorrelated photons, , is marked (dashed line) for comparison. In the three qubit case, note the strong bunching in transmission [panel (c)] and striking quantum beats in reflection [panel (f)].