Figure 4

Second-order correlation function,${\mathit{g}}_{\mathbf{2}}\mathbf{(}\mathit{t}\mathbf{)}$, calculated with a weak incident coherent state for spacing${\mathit{k}}_{\mathbf{0}}\mathit{L}\mathbf{=}\mathit{\pi }\mathbf{/}\mathbf{4}$. First row is for transmitted photons, second row for reflected photons. The columns correspond to $N=1,2,\text{ or }3$ qubits coupled to the waveguide. The photon frequency is chosen so that $T=50\mathrm{\%}$. The result for uncorrelated photons, $g_2=1$, is marked (dashed line) for comparison. In the three qubit case, note the strong bunching in reflection [panel (f)] and long anti-bunching interval after the initial bunching in transmission [panel (c)].