  We calculate the energy levels and corresponding eigenstates of an
interacting scalar quantum field theory on a lattice using a
continuous-variable version of the quantum imaginary time evolution algorithm.
Only a single qumode is needed for the simulation of the field at each point on
the lattice. Our quantum algorithm avoids the use of non-Gaussian quantum gates
and relies, instead, on detectors projecting onto eigenstates of the
photon-number operator. Using Xanadu's Strawberry Fields simulator, we obtain
results on energy levels that are in very good agreement with results from
exact calculations. We propose an experimental setup that can be realized with
existing technology.
