Co-Designed Adaptive Quantum State Preparation Protocols

The ADAPT-VQE algorithm is a main contender in the quest for quantum advantage. Due to its shallow and trainable ansätze, it is particularly suitable for near-term quantum computers. However, the original algorithm workflow is agnostic to the target architecture, leading to high transpilation overheads and suboptimal results. In this work, we propose a co-designed variant of ADAPT-VQE (Co-ADAPT-VQE) where the quantum hardware is taken into account in the construction of the ansatz. This framework can be readily used to optimize state preparation circuits for any device, addressing shortcomings such as limited connectivity, short coherence times, and variable gate errors. We exemplify the impact of Co-ADAPT-VQE by creating state preparation circuits for devices with linear nearest-neighbor (LNN) connectivity. We show a reduction of the CNOT count of the final circuits by up to 97% for 12-14 qubit systems, with the impact being greater for larger and more strongly correlated systems. Surprisingly, the circuits created by Co-ADAPT-VQE provide an over 70% CNOT count reduction with respect to the original ADAPT-VQE in all-to-all connectivity, despite being restricted to LNN qubit interactions.