  Quantum computers can efficiently solve problems which are widely believed to
lie beyond the reach of classical computers. In the near-term, hybrid
quantum-classical algorithms, which efficiently embed quantum hardware in
classical frameworks, are crucial in bridging the vast divide in the
performance of the purely-quantum algorithms and their classical counterparts.
Here, a hybrid quantum-classical algorithm is presented for the computation of
non-perturbative characteristics of quantum field theories. The presented
algorithm relies on a universal parametrized quantum circuit ansatz based on
Euler and Cartan's decompositions of single and two-qubit operators. It is
benchmarked by computing the energy spectra of lattice realizations of quantum
field theories with both short and long range interactions. Low depth circuits
are provided for false vacua as well as highly excited states corresponding to
mesonic and baryonic excitations occurring in the analyzed models. The
described algorithm opens a hitherto-unexplored avenue for the investigation of
mass-ratios, scattering amplitudes and false-vacuum decays in quantum field
theories.
