  We consider a hybrid digital-analog quantum computing approach, which allows
implementing any quantum algorithm without standard two-qubit gates. This
approach is based on the always-on interaction between qubits, which can
provide an alternative to such gates. We show how digital-analog approach can
be applied to simulate the dynamics of fermionic systems, in particular the
Fermi-Hubbard model, using fermionic SWAP network and refocusing technique.
  We concentrate on the effects of connectivity topology, spread of interaction
constants as well as on errors of entangling operations. We find that an
optimal connectivity topology of qubits for the digital-analog simulation of
fermionic systems of arbitrary dimensionality is a chain for spinless fermions
and a ladder for spin-1/2 particles. Such a simple connectivity topology makes
digital-analog approach attracting for the fermionic quantum simulation.
