Entry water_dimer_ccpvdz_JW_UCCSD_v4_tapered__sha256_6383f47170758daa | QEncode

Molecule / Problem

Namewater_dimer

Basis setcc-pvdz

GeometryO -1.551007 -0.114520 0.000000; H -1.934259 0.762503 0.000000; H -0.599677 0.040712 0.000000; O 1.350625 0.111469 0.000000; H 1.680398 -0.373741 -0.758561; H 1.680398 -0.373741 0.758561

Charge0

Spin0

Active electrons4

Active orbitals4

Orbital optimizationHF

Encoding / Circuit

Qubit mappingjordan-wigner

Ansatz typeuccsd_tapered

Ansatz reps (HEA)1

TaperingZ2 symmetry — 3 symmetries removed

Qubits (original)8

Qubits (tapered)5

Num parameters56

Circuit depth105

2Q gates20

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-152.0625362496 Ha

MP2 energy-152.4734315200 Ha

CCSD energy-152.4912439611 Ha

CCSD(T) energy-152.4977225163 Ha

CASCI ground state-152.0627193590 Ha

VQE best energy-152.0627174339 Ha

|VQE − CASCI| gap1.925048e-6 Ha

CCSD(T) correlation-4.351863e-1 Ha

Optimizer / Run Config

AlgorithmCOBYLA

Multistart runs1

Max iterations500

Total func evals500

Num parameters56

Backenddefault.qubit

Provenance / Reproducibility

Entry IDwater_dimer_ccpvdz_JW_UCCSD_v4_tapered__sha256_6383f47170758daa

Schema version4.0.0

Created (UTC)2026-07-16T13:11:13.953680+00:00

SHA-256 hash6383f47170758daafe44c0a9ef50e7b794da0e5151b51662ec645c7583986195

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 water_dimer \

--mapping jordan_wigner \

--ansatz-type uccsd \

--multistart 1 \

--max-iter 500 \

--out-dir releases/v4/db

View raw JSON on GitHub