  The scalability of photonic implementations of fault-tolerant quantum
computing based on Gottesman-Kitaev-Preskill (GKP) qubits is injured by the
requirements of inline squeezing and reconfigurability of the linear optical
network. In this work we propose a topologically error-corrected architecture
that does away with these elements at no cost - in fact, at an advantage - to
state preparation overheads. Our computer consists of three modules: a 2D array
of probabilistic sources of GKP states; a depth-four circuit of static
beamsplitters, phase shifters, and single-time-step delay lines; and a 2D array
of homodyne detectors. The symmetry of our proposed circuit allows us to
combine the effects of finite squeezing and uniform photon loss within the
noise model, resulting in more comprehensive threshold estimates. These jumps
over both architectural and analytical hurdles considerably expedite the
construction of a photonic quantum computer.
