Reducing unitary coupled cluster circuit depth by classical stochastic amplitude prescreening

Unitary coupled cluster (UCC) approaches are an appealing route to utilizing quantum hardware perform chemistry calculations, as computers can in principle UCC calculations a polynomially scaling fashion, compared with the exponential required on classical computers. Current noisy intermediate scale limited by both capacity number of logical qubits and noise introduced deep circuits for using variational eigensolver (VQE) approach. We present combined classical-quantum approach where stochastic preprocessing step is used determine important excitations Ansatz. The reduced selected then UCC-based VQE calculation. This gives systematically improvable approximation, we show that significant reductions resources be achieved, simulations ${\mathrm{CH}}_{2}, {\mathrm{N}}_{2}$, ${\mathrm{N}}_{2}{\mathrm{H}}_{2}$ molecules giving submillihartree errors.