QEncode Benchmark
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H2

/bravyi kitaev/hea
Certified
Beats CCSD(T)
cc-pvdz

H2_ccpvdz_BK_HEA_v4_tapered__sha256_aa7360a68d23f35c

VQE Gap

8.5912e-9 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 mappingbravyi-kitaev
Ansatz typehea
Ansatz reps (HEA)2
TaperingZ2 symmetry — 3 symmetries removed
Qubits (original)4
Qubits (tapered)1
Num parameters3
Circuit depth4
2Q gates0
Non-Clifford gates3
T gates (FT estimate)36 (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-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-1.1312865027 Ha
|VQE − CASCI| gap8.591151e-9 Ha
CCSD(T) correlation-3.458679e-2 Ha

Optimizer / Run Config

AlgorithmCOBYLA
Multistart runs1
Max iterations500
Total func evals42
Num parameters3
Backenddefault.qubit

Provenance / Reproducibility

Entry IDH2_ccpvdz_BK_HEA_v4_tapered__sha256_aa7360a68d23f35c
Schema version4.0.0
Created (UTC)2026-09-07T11:04:28.856415+00:00
SHA-256 hashaa7360a68d23f35cb6487ea63d878d727ae713692744aa73ed9bead75d144e88
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 bravyi_kitaev \

--ansatz-type hea \

--reps 2 \

--multistart 1 \

--max-iter 500 \

--out-dir releases/v4/db

View raw JSON on GitHub