Entry H2O_ccpvdz_PAR_HEA_v4_tapered__sha256_b50cee1c91dc0410 | QEncode

Molecule / Problem

NameH2O

Basis setcc-pvdz

GeometryO 0.0 0.0 0.0; H 0.0 0.757 0.586; H 0.0 -0.757 0.586

Charge0

Spin0

Active electrons4

Active orbitals4

Orbital optimizationHF

Encoding / Circuit

Qubit mappingparity

Ansatz typehea

Ansatz reps (HEA)2

TaperingZ2 symmetry — 4 symmetries removed

Qubits (original)8

Qubits (tapered)4

Num parameters12

Circuit depth9

2Q gates6

Non-Clifford gates12

T gates (FT estimate)144 (ε = 0.001)

T-gate count is the resource-relevant cost of a fault-tolerant implementation. It is an estimate from the non-Clifford rotations in the pre-transpilation circuit, assuming standard rotation synthesis to precision ε — not a compiled count for a specific device.

Energy Results

HF energy-76.0267936450 Ha

MP2 energy-76.2307620086 Ha

CCSD energy-76.2400859051 Ha

CCSD(T) energy-76.2431421376 Ha

CASCI ground state-76.0273383586 Ha

VQE best energy-76.0269391502 Ha

|VQE − CASCI| gap3.992084e-4 Ha

CCSD(T) correlation-2.163485e-1 Ha

Optimizer / Run Config

AlgorithmCOBYLA

Multistart runs1

Max iterations500

Total func evals500

Num parameters12

Backenddefault.qubit

Provenance / Reproducibility

Entry IDH2O_ccpvdz_PAR_HEA_v4_tapered__sha256_b50cee1c91dc0410

Schema version4.0.0

Created (UTC)2026-09-07T12:10:25.275274+00:00

SHA-256 hashb50cee1c91dc04104d6ba7f39c0b0e9dc86d468911a3f50dd49b973ad765837d

Python3.11.15

PySCF2.6.2

PennyLane0.45.0

OpenFermion1.6.1

NumPy2.2.6

SciPy1.13.1

Reproduce this result

# Clone repo and install pinned environment

git clone https://github.com/qencode-benchmark/qencode-benchmark

cd qencode-benchmark

pip install -r requirements-v4.txt

# Run this entry

python scripts/generate_entry_v4.py \

--molecule H2O \

--mapping parity \

--ansatz-type hea \

--reps 2 \

--multistart 1 \

--max-iter 500 \

--out-dir releases/v4/db

View raw JSON on GitHub