Table 2. Number of Pauli Terms 
for a Selection of (Tapered) Ansätzea.
| number
of terms in ansatz operator |
||||
|---|---|---|---|---|
| molecule |  |
UCCSDT (full/proj)b | UCCSD (full/proj)b | ADAPT-VQEc |
| Be | 3 | (48/6) | (48/6) | 5 |
| B | 3 | (48/12) | (32/4) | 3 |
| LiH | 4 | (704/53) | (192/53) | 5 |
| BeH+ | 6 | (646/191) | (166/79) | 11 |
| HF | 4 | (92/57) | (92/57) | 4 |
| BeH2 | 7 | (1312/352) | (224/96) | 10 |
| H2O | 7 | (1892/942) | (324/238) | 21 |
| F2 | 10 | (176/114) | (176/114) | 12 |
| HCl | 4 | (348/40) | (348/40) | 4 |
b
The number of qubits in the contextual subspace over which the ansatz is projected; each tuple (full/proj) gives the number of terms pre- and postprojection.
c
The number of ADAPT-VQE cycles required to achieve chemical precision, with the operator pool consisting of the projected UCCSD terms.