Finding ground states and low-lying excitations of a given Hamiltonian is one of the most important
problems in many fields of physics. As a novel approach, quantum computing on Noisy Intermediate-Scale
Quantum (NISQ) devices offers the prospect to efficiently perform such computations and may eventually outperform
classical computers. However, current quantum devices still suffer from inherent quantum noise. In this work, we propose an error mitigation scheme suitable for
parametric quantum circuits. This scheme is based on projecting a general quantum noise channel onto
depolarization errors. Our method can efficiently reduce errors in quantum computations, which we demonstrate by carrying out simulations both on classical and IBM's quantum devices. In particular, we test the performance of the method by computing the mass gap of the transverse-field Ising model using the variational quantum eigensolver algorithm.