QEncode Benchmark
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NH3

/parity/hea
Certified
Beats CCSD(T)
cc-pvdz

NH3_ccpvdz_PAR_HEA_v4_tapered__sha256_aa3769fb20846ec5

VQE Gap

6.9115e-3 Ha

CASCI ref

-56.197889 Ha

Qubits (tapered)

5

CCSD(T) corr.

-2.085e-1 Ha

Molecule / Problem

NameNH3
Basis setcc-pvdz
GeometryN 0.0 0.0 0.1173; H 0.0 0.9289 -0.2737; H 0.8045 -0.4645 -0.2737; H -0.8045 -0.4645 -0.2737
Charge0
Spin0
Active electrons4
Active orbitals4
Orbital optimizationHF

Encoding / Circuit

Qubit mappingparity
Ansatz typehea
Ansatz reps (HEA)2
TaperingZ2 symmetry — 3 symmetries removed
Qubits (original)8
Qubits (tapered)5
Num parameters15
Circuit depth10
2Q gates8

Energy Results

HF energy-56.1957314939 Ha
MP2 energy-56.3845132569 Ha
CCSD energy-56.4004649816 Ha
CCSD(T) energy-56.4042812742 Ha
CASCI ground state-56.1978885887 Ha
VQE best energy-56.1909771263 Ha
|VQE − CASCI| gap6.911462e-3 Ha
CCSD(T) correlation-2.085498e-1 Ha

Optimizer / Run Config

AlgorithmCOBYLA
Multistart runs10
Max iterations500
Total func evals5,000
Num parameters15
Backenddefault.qubit

Provenance / Reproducibility

Entry IDNH3_ccpvdz_PAR_HEA_v4_tapered__sha256_aa3769fb20846ec5
Schema version4.0.0
Created (UTC)2026-07-15T13:22:43.079931+00:00
SHA-256 hashaa3769fb20846ec5419f3db03b27928792e89d78d26c3c941b464ebd812bae55
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 NH3 \

--mapping parity \

--ansatz-type hea \

--reps 2 \

--multistart 10 \

--max-iter 500 \

--out-dir releases/v4/db