  We address the design of optimal heralding schemes in linear optical quantum
computing context. The problem admits unit fidelity formulation in relevant
Fock space, thanks to linear optic feasibility criteria of [Phys. Rev. A100,
022301; arXiv:1901.06178]. Corresponding solution methodology is presented. As
an application we inspect optimality of a few known schemes of Bell states
generation. It is shown that in case of six modes and two ancillary photons
success rate 2/27 is suboptimal.
