Efficient quantum information-inspired ansatz for variational quantum eigensolver algorithm: Applications to atomic systems
Abdul Kalam, Prasenjit Deb, Akitada Sakurai, B. K. Sahoo, V. S. Prasannaa, B. P. Das · Physical Review Research · 2026
We present a quantum information-inspired ansatz for the variational quantum eigensolver and demonstrate its efficacy in calculating ground-state energies of atomic systems. Instead of adopting a heuristic approach, we start with an approximate multiqubit target state and utilize two quantum information-theoretic quantities, i.e., von Neumann entropy and quantum mutual information, to construct our ansatz. The quantum information encoded in the target state helps us design unique blocks and identify qubit pairs that exhibit maximal quantum correlations within the multi-qubit system, thereby enabling us to deterministically place two-qubit entanglers in the suitably constructed parametrized quantum circuit. We find that our approach offers the advantage of reduced circuit depth compared to the physics-inspired unitary coupled-cluster (UCC) ansatz, while yielding accurate results. To test the performance of our ansatz, we apply it to compute ground-state energies of atomic systems in the relativistic regime. Our results show that for up to 12-qubits (12-spinorbitals) noiseless calculations, our ansatz yields energies within chemical accuracy ( ∼ 1.6 mhartree) relative to the complete active space configuration interaction values, while utilizing only a few blocks that contain in the best case 98 % fewer two-qubit gates when compared with the UCC ansatz in the singles and doubles approximation.