  Waveguide quantum electrodynamics represents a powerful platform to generate
entanglement and tailor photonic states. We consider a pair of identical qubits
coupled to a parity invariant waveguide in the microwave domain. By working in
the one- and two-excitation sectors, we provide a unified view of decay
processes and we show the common origin of directional single photon emission
and two photon directional bunching. Unveiling the quantum trajectories, we
demonstrate that both phenomena are rooted in the selective coupling of
orthogonal qubits Bell states with different photon propagation directions. We
comment on how to use this mechanism to implement optimized post-selection of
Bell states, heralded by the detection of photons on one qubits side.
