Exploiting subspace constraints and ab initio variational methods for quantum chemistry

Variational methods offer a highly promising route to exploiting quantum computers for chemistry tasks. Here we employ described in sister paper the present report, entitled ab initio machine synthesis of circuits, order solve problems using adaptively evolving circuits. Consistent with prior authors find that this approach can outperform human-designed circuits such as coupled-cluster or hardware-efficient ans\"atze, and make comparisons larger instances up 14 qubits. Moreover introduce novel constraining circuit evolution physically relevant subspace, finding greatly improves performance compactness We consider both static dynamics properties molecular systems. The emulation environments used is QuESTlink; all resources are open source linked from paper.