Entry BeH2_ccpvdz_PAR_UCCSD_v4_tapered__sha256_f71541a4f8d3e964 | QEncode

VQE Gap

2.2225e-3 Ha

CASCI ref

-15.768411 Ha

Qubits (tapered)

CCSD(T) corr.

-6.896e-2 Ha

Molecule / Problem

NameBeH2

Basis setcc-pvdz

GeometryH 0.0 0.0 -1.30; Be 0.0 0.0 0.0; H 0.0 0.0 1.30

Charge0

Spin0

Active electrons4

Active orbitals4

Orbital optimizationHF

Encoding / Circuit

Qubit mappingparity

Ansatz typeuccsd_tapered

Ansatz reps (HEA)1

TaperingZ2 symmetry — 5 symmetries removed

Qubits (original)8

Qubits (tapered)3

Num parameters12

Circuit depth22

2Q gates8

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-15.7664276149 Ha

MP2 energy-15.8183028207 Ha

CCSD energy-15.8349590260 Ha

CCSD(T) energy-15.8353910120 Ha

CASCI ground state-15.7684109880 Ha

VQE best energy-15.7661884701 Ha

|VQE − CASCI| gap2.222518e-3 Ha

CCSD(T) correlation-6.896340e-2 Ha

Optimizer / Run Config

AlgorithmCOBYLA

Multistart runs10

Max iterations500

Total func evals3,412

Num parameters12

Backenddefault.qubit

Provenance / Reproducibility

Entry IDBeH2_ccpvdz_PAR_UCCSD_v4_tapered__sha256_f71541a4f8d3e964

Schema version4.0.0

Created (UTC)2026-07-15T13:21:10.928451+00:00

SHA-256 hashf71541a4f8d3e9643e97ab6695da59dd99d619ef333dca6b4acd9977d9002926

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 BeH2 \

--mapping parity \

--ansatz-type uccsd \

--multistart 10 \

--max-iter 500 \

--out-dir releases/v4/db

View raw JSON on GitHub