Gate-free state preparation for fast variational quantum eigensolver simulations

The variational quantum eigensolver (VQE) is a leading algorithm for solving electronic structure problems on near-term quantum computers. This paper proposes an alternative algorithm, ctrl-VQE, which variationally optimizes device-level pulse shapes for state preparation instead of using parameterized quantum circuits. This significantly reduces the coherence time required, leading to reductions in state preparation times of roughly three orders of magnitude compared to gate-based strategies. Numerical demonstrations using H₂, HeH⁺, and LiH show the accuracy and efficiency of ctrl-VQE.

Oinam Romesh Meitei, Bryan T. Gard, George S. Barron, David P. Pappas, Sophia E. Economou, Edwin Barnes, Nicholas J. Mayhall