Line data    Source code

       1             : # SPDX-FileCopyrightText: 2024 PairInteraction Developers
       2             : # SPDX-License-Identifier: LGPL-3.0-or-later
       3             : 
       4           1 : from __future__ import annotations
       5             : 
       6           1 : from typing import TYPE_CHECKING
       7             : 
       8           1 : import numpy as np
       9           1 : import pytest
      10             : 
      11           1 : from .utils import REFERENCE_PATHS, compare_eigensystem_to_reference
      12             : 
      13             : if TYPE_CHECKING:
      14             :     from .utils import PairinteractionModule
      15             : 
      16             : 
      17           1 : def test_pair_potential(pi_module: PairinteractionModule, generate_reference: bool) -> None:
      18             :     """Test calculating a pair potential."""
      19             :     # Create a single-atom system
      20           1 :     basis = pi_module.BasisAtom("Rb", n=(58, 62), l=(0, 2))
      21           1 :     print(f"Number of single-atom basis states: {basis.number_of_states}")
      22             : 
      23           1 :     system = pi_module.SystemAtom(basis)
      24             : 
      25             :     # Create two-atom systems for different interatomic distances
      26           1 :     ket = pi_module.KetAtom("Rb", n=60, l=0, m=0.5)
      27           1 :     delta_energy = 3  # GHz
      28           1 :     min_energy = 2 * ket.get_energy(unit="GHz") - delta_energy
      29           1 :     max_energy = 2 * ket.get_energy(unit="GHz") + delta_energy
      30             : 
      31           1 :     basis_pair = pi_module.BasisPair([system, system], energy=(min_energy, max_energy), energy_unit="GHz", m=(1, 1))
      32           1 :     print(f"Number of two-atom basis states: {basis_pair.number_of_states}")
      33             : 
      34           1 :     distances = np.linspace(1, 5, 5)
      35           1 :     system_pairs = [pi_module.SystemPair(basis_pair).set_distance(d, unit="micrometer") for d in distances]
      36             : 
      37             :     # Diagonalize the systems in parallel
      38           1 :     pi_module.diagonalize(system_pairs, diagonalizer="eigen", sort_by_energy=True)
      39             : 
      40             :     # Get the overlap with |ket, ket>
      41           1 :     overlaps = np.array([system.get_eigenbasis().get_overlaps([ket, ket]) for system in system_pairs])
      42             : 
      43             :     # Ensure that the overlaps sum up to one
      44           1 :     np.testing.assert_allclose(np.sum(overlaps, axis=1), np.ones(5))
      45             : 
      46             :     # Compare to reference data
      47           1 :     kets = [ket.get_label("raw") for ket in basis_pair.kets]
      48           1 :     eigenenergies = np.array([system.get_eigenenergies(unit="GHz") for system in system_pairs])
      49           1 :     eigenvectors = np.array([system.get_eigenbasis().get_coefficients().todense().A1 for system in system_pairs])
      50             : 
      51           1 :     reference_path = REFERENCE_PATHS["pair_potential"]
      52           1 :     if generate_reference:
      53           1 :         reference_path.mkdir(parents=True, exist_ok=True)
      54           1 :         np.savetxt(reference_path / "kets.txt", kets, fmt="%s", delimiter="\t")
      55           1 :         np.savetxt(reference_path / "eigenenergies.txt", eigenenergies)
      56           1 :         np.savetxt(reference_path / "overlaps.txt", overlaps)
      57           1 :         pytest.skip("Reference data generated, skipping comparison test")
      58             : 
      59           1 :     compare_eigensystem_to_reference(reference_path, eigenenergies, overlaps, eigenvectors, kets)