Table 1. Quantum circuit resource estimation for the calculation of the ground-state vibrational energy of CO₂, H₂CO, and HCOOH with the UVCC and CHC approaches including single and double excitations. The number of CNOT gates (CX) is given for both approaches. The number of variational parameters is the same in both wavefunctions.

Molecule	Modes	Modals	CX UVCC	CX CHC	Parameters
CO2	4	2	304	44	10
		4	2640	348	66
		6	7280	940	170
		8	14 224	1820	322
		10	23 472	2988	522
H2CO	6	2	744	102	21
		4	6552	846	153
		6	18 120	2310	405
		8	35 448	4494	777
		10	58 536	7398	1269
HCOOH	9	2	1764	234	45
		4	15 660	1998	351
		6	43 380	5490	945
		8	84 924	10 710	1827
		10	140 292	17 658	2997