Demonstration of subspace-search variational quantum eigensolver using photonic orbital angular momentum qudits
This work experimentally implemented a subspace-search variational quantum eigensolver (SSVQE) using single photons encoded in orbital angular momentum (OAM) qudits. By preparing mutually orthogonal OAM states via spatial light modulators, the method efficiently finds excited state energies for molecular and chain systems. The approach avoids complex ancilla estimation, showing good convergence toward theoretical values for tested models.