H2 QPE Validation¶
This tutorial validates the small H2 path used as the first q2m3 smoke test. It compares vacuum and MM-embedded H2 Hamiltonians and reports stabilization in kcal/mol after explicit conversion from Hartree.
Run The Script¶
uv run python examples/h2_qpe_validation.py
The script performs four steps:
Build vacuum and solvated PennyLane Hamiltonians from PySCF data.
Run classical Hartree-Fock references for vacuum and MM-embedded systems.
Execute QPE for both Hamiltonians.
Compare HF and QPE stabilization energies.
What The Example Builds¶
Component |
Value |
|---|---|
Molecule |
H2 |
Bond length |
0.74 Angstrom |
Basis |
STO-3G |
Active space |
2 electrons, 2 orbitals |
System qubits |
4 |
MM environment |
2 TIP3P waters as point charges |
Default QPE register |
4 estimation wires |
The MM point charges are placed about 3 Angstrom from H2. This keeps the example small while still exercising the MM embedding path.
Interpreting Results¶
The maintained example README records these current H2 checks:
Quantity |
Current reference |
|---|---|
QPE-HF signed energy offset |
|
Absolute offset equivalent |
|
QPE solvation stabilization |
|
PennyLane HF vs PySCF HF agreement |
|
Treat the H2 script as an integration validation, not as a broad chemistry benchmark. The thresholds are example-specific and intentionally relaxed for the POC scale.
Common Adjustments¶
Use more estimation wires for better phase resolution, and increase Trotter steps only after confirming memory and runtime are acceptable. If the energy appears to wrap or jump by a large amount, inspect the base time and shifted QPE parameters before interpreting the difference physically.