Extracting vacuum expectation values from approximate vacuum prepared by the adiabatic quantum computation

We propose a procedure to extract vacuum expectation values from approximate vacuum prepared by the adiabatic quantum computation. We use plural ancilla bits with hierarchical structure, intending to gradually put up approximate precision. We exhibit simulation results for a typical one-qubit system and a two-qubits system based on the (1+1)-dimensional Schwinger model using classically emulated digital quantum simulator.