  Quantum computing has demonstrated the potential to revolutionize our
understanding of nuclear, atomic, and molecular structure by obtaining
forefront solutions in non-relativistic quantum many-body theory. In this work,
we show that quantum computing can be used to solve for the structure of
hadrons, governed by strongly-interacting relativistic quantum field theory.
Following our previous work on light unflavored mesons as a relativistic
bound-state problem within the nonperturbative Hamiltonian formalism, we
present the numerical calculations on simulated quantum devices using the basis
light-front quantization (BLFQ) approach. We implement and compare the
variational quantum eigensolver (VQE) and the subspace-search variational
quantum eigensolver (SSVQE) to find the low-lying mass spectrum of the light
meson system and its corresponding light-front wave functions as quantum states
from ideal simulators, noisy simulators, and IBM quantum computers. Based on
obtained quantum states, we evaluate the meson decay constants and parton
distribution functions directly on the quantum circuits. Our calculations on
the quantum computers and simulators are in reasonable agreement with accurate
numerical solutions solved on classical computers when noises are moderately
small, and our overall results are comparable with the available experimental
data.
