  We study the photon blockade of two-photon scattering in a one-dimensional
waveguide, which contains two atoms coupled via the Rydberg interaction. We
obtain the analytic scattering solution of photonic wave packets with the
Laplace transform method. We examine the photon correlation by addressing the
two-photon relative wave function and the second-order correlation function in
the single- and two-photon resonance cases. It is found that, under the
single-photon resonance condition, photon bunching and antibunching can be
observed in the two-photon transmission and reflection, respectively. In
particular, the bunching and antibunching effects become stronger with the
increasing of the Rydberg coupling strength. In addition, we find a phenomenon
of bunching-antibunching transition caused by the two-photon resonance.
