Entry C4H4_ccpvdz_JW_UCCSD_v4_casscf_tapered__sha256_a26c030f93eb230d | QEncode

Molecule / Problem

NameC4H4

Basis setcc-pvdz

GeometryC 0.673 0.783 0.0; C -0.673 0.783 0.0; C -0.673 -0.783 0.0; C 0.673 -0.783 0.0; H 1.377 1.602 0.0; H -1.377 1.602 0.0; H -1.377 -1.602 0.0; H 1.377 -1.602 0.0

Charge0

Spin0

Active electrons4

Active orbitals4

Orbital optimizationCASSCF

Encoding / Circuit

Qubit mappingjordan-wigner

Ansatz typeuccsd_tapered

Ansatz reps (HEA)1

TaperingZ2 symmetry — 2 symmetries removed

Qubits (original)8

Qubits (tapered)6

Num parameters152

Circuit depth286

2Q gates32

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.

This entry has 152 variational parameters — a large landscape requiring multistart optimisation. 1 independent restarts were run.

Energy Results

HF energy-153.6528244194 Ha

MP2 energy-154.1870717643 Ha

CCSD energy-154.2235763592 Ha

CCSD(T) energy-154.2485698632 Ha

CASSCF energy-153.6734265502 Ha

CASCI ground state-153.6734265503 Ha

VQE best energy-153.6655097925 Ha

|VQE − CASCI| gap7.916758e-3 Ha

CCSD(T) correlation-5.957454e-1 Ha

Optimizer / Run Config

AlgorithmCOBYLA

Multistart runs1

Max iterations500

Total func evals500

Num parameters152

Backenddefault.qubit

Provenance / Reproducibility

Entry IDC4H4_ccpvdz_JW_UCCSD_v4_casscf_tapered__sha256_a26c030f93eb230d

Schema version4.0.0

Created (UTC)2026-07-16T13:08:24.482985+00:00

SHA-256 hasha26c030f93eb230d3dc5b7bc3533a9a8030cc052265b1419bbe42ac854363818

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 C4H4 \

--mapping jordan_wigner \

--ansatz-type uccsd \

--orbital-opt casscf \

--multistart 1 \

--max-iter 500 \

--out-dir releases/v4/db

View raw JSON on GitHub