QEncode Benchmark
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LiH

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

LiH_ccpvdz_PAR_HEA_v4_tapered__sha256_b4373017ff3b1438

VQE Gap

3.3702e-3 Ha

CASCI ref

-7.983773 Ha

Qubits (tapered)

5

CCSD(T) corr.

-3.110e-2 Ha

Molecule / Problem

NameLiH
Basis setcc-pvdz
GeometryLi 0.0 0.0 0.0; H 0.0 0.0 1.6
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
Non-Clifford gates15
T gates (FT estimate)180 (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-7.9836422316 Ha
MP2 energy-8.0064478384 Ha
CCSD energy-8.0147376230 Ha
CCSD(T) energy-8.0147469479 Ha
CASCI ground state-7.9837729770 Ha
VQE best energy-7.9804028157 Ha
|VQE − CASCI| gap3.370161e-3 Ha
CCSD(T) correlation-3.110472e-2 Ha

Optimizer / Run Config

AlgorithmCOBYLA
Multistart runs1
Max iterations500
Total func evals500
Num parameters15
Backenddefault.qubit

Provenance / Reproducibility

Entry IDLiH_ccpvdz_PAR_HEA_v4_tapered__sha256_b4373017ff3b1438
Schema version4.0.0
Created (UTC)2026-09-07T12:10:14.258113+00:00
SHA-256 hashb4373017ff3b14389f643ecb41eb2a3d775840c2fde2c05a3a970c898bb8f7ea
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 LiH \

--mapping parity \

--ansatz-type hea \

--reps 2 \

--multistart 1 \

--max-iter 500 \

--out-dir releases/v4/db

View raw JSON on GitHub