Non-unitary operations for ground-state calculations in near term quantum computers

Understand

We introduce a quantum Monte Carlo inspired reweighting scheme to accurately compute energies from optimally short quantum circuits.

• This effectively hybrid quantum-classical approach features both entanglement provided by a short quantum circuit, and the presence of an effective non-unitary operator at the same time.
• The functional form of this projector is borrowed from classical computation and is able to filter-out high-energy components generated by a sub-optimal variational quantum heuristic ansatz.
• The accuracy of this approach is demonstrated numerically in finding energies of entangled ground-states of many-body lattice models.