Mitigating noise-induced barren plateaus using non-unitary ansatz

Noise in quantum hardware has been shown to induce barren plateaus [Nature Communications 12, 6961 (2021)], where the gradients vanish even under infinitesimal noise, severely limiting the scalability of Variational Quantum Algorithms (VQAs). We propose and demonstrate that a non-unitary ansatz can overcome this limitation. Our numerical simulations confirm the robustness of this strategy against noise induced barren plateaus. Our approach is analytically demonstrated using a mean-field Ising model, which we examine through a Floquet formalism, treating the ansatz layer as a Floquet superoperator. Building on these results, we aim to extend this framework to simulate the steady state of a reaction involving a DNA molecule, inspired by an experimental work [ACS Appl. Bio Mater. 2024, 7, 8, 5308–5317]. This study establishes VQAs with non-unitary ansatz as a promising route for simulation of open quantum systems on near-term quantum devices.