  Bell state measurements (BSM) play a significant role in quantum information
and quantum computing, in particular, in fusion-based quantum computing (FBQC).
The FBQC model is a framework for universal quantum computing provided that we
are able to perform entangling measurements, called fusions, on qubits within
small entangled resource states. Here we analyse the usage of different
linear-optical BSM circuits as fusions in the FBQC schemes and numerically
evaluate hardware requirements for fault-tolerance in this framework. We
examine and compare the performance of several BSM circuits with varying
additional resources and estimate the requirements on losses for every
component of the linear-optical realization of fusions under which errors in
fusion networks caused by these losses can be corrected. Our results show that
fault-tolerant quantum computing in the FBQC model is possible with currently
achievable levels of optical losses in an integrated photonic implementation,
provided that we can create and detect single photons of the resource states
with a total marginal efficiency higher than 0.973.
