QEncode Benchmark
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H2

/parity/uccsd tapered
Certified
Beats CCSD(T)
cc-pvdz

H2_ccpvdz_PAR_UCCSD_v4_tapered__sha256_b321a0331d6d13eb

VQE Gap

0.0000e+0 Ha

CASCI ref

-1.131287 Ha

Qubits (tapered)

1

CCSD(T) corr.

-3.459e-2 Ha

Molecule / Problem

NameH2
Basis setcc-pvdz
GeometryH 0.0 0.0 0.0; H 0.0 0.0 0.735
Charge0
Spin0
Active electrons2
Active orbitals2
Orbital optimizationHF

Encoding / Circuit

Qubit mappingparity
Ansatz typeuccsd_tapered
Ansatz reps (HEA)1
TaperingZ2 symmetry — 3 symmetries removed
Qubits (original)4
Qubits (tapered)1
Num parameters1
Circuit depth2
2Q gates0

Note on UCCSD circuit metrics

UCCSD uses exponential Pauli operators (exp(iθH)) that are symbolic before compilation. Circuit depth and 2-qubit gate counts are not reported here — they depend on the target hardware and transpiler.

Energy Results

HF energy-1.1286227699 Ha
MP2 energy-1.1549489623 Ha
CCSD energy-1.1632095636 Ha
CCSD(T) energy-1.1632095636 Ha
CASCI ground state-1.1312865113 Ha
VQE best energy-1.1312865113 Ha
|VQE − CASCI| gap0.000000e+0 Ha
CCSD(T) correlation-3.458679e-2 Ha

Optimizer / Run Config

AlgorithmCOBYLA
Multistart runs10
Max iterations500
Total func evals114
Num parameters1
Backenddefault.qubit

Provenance / Reproducibility

Entry IDH2_ccpvdz_PAR_UCCSD_v4_tapered__sha256_b321a0331d6d13eb
Schema version4.0.0
Created (UTC)2026-07-15T13:22:29.109380+00:00
SHA-256 hashb321a0331d6d13eba2db5c9c0e53b0b589e62a48b616eb06ff67571175a8b90c
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 H2 \

--mapping parity \

--ansatz-type uccsd \

--multistart 10 \

--max-iter 500 \

--out-dir releases/v4/db

View raw JSON on GitHub