Quantum simulation of fermionic systems using hybrid digital–analog quantum computing approach

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, the 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 attractive for the simulation of quantum materials and molecules.