qat.fermion.chemistry.wrapper.MoleculeInfo

class qat.fermion.chemistry.wrapper.MoleculeInfo(hamiltonian: MolecularHamiltonian, n_electrons: int, noons: ndarray | List[float], orbital_energies: ndarray)

MoleculeInfo helper class. This class is a even higher level version of the MolecularHamiltonian.

Parameters:

hamiltonian (MolecularHamiltonian) – The MolecularHamiltonian of the studied molecule.
n_electrons (int) – Number of electrons.
noons (Union[np.ndarray, List[float]]) – Natural orbital occupation number.
orbital_energies (np.ndarray) – Orbital energies.

nqbits

The total number of qubits.

Type:: int

one_body_integrals

One-body integrals \(I_{uv}\).

Type:: np.ndarray

two_body_integrals

Two-body integrals \(I_{uvwx}\).

Type:: np.ndarray

constant_coeff

Constant coefficient \(r\) (core repulsion).

Type:: np.ndarray

hamiltonian

The MolecularHamiltonian of the studied molecule.

Type:: MolecularHamiltonian

n_electrons

Number of electrons.

Type:: int

noons

Natural orbital occupation number.

Type:: Union[np.ndarray, List[float]]

orbital_energies

Orbital energies.

Type:: np.ndarray

Example

import numpy as np
from qat.fermion.chemistry import MolecularHamiltonian, MoleculeInfo

# For illustration purpose, initialize random one- and two-body integrals, and a constant
one_body_integral = np.random.randn(2, 2)
two_body_integral = np.random.randn(2, 2, 2, 2)
constant = np.random.rand()
noons = list(np.random.randn(10))
orbital_energies = list(np.random.randn(10))

# Define the MolecularHamiltonian
mol_h = MolecularHamiltonian(one_body_integral, two_body_integral, constant)

# Define MoleculeInfo
molecule = MoleculeInfo(
    mol_h,
    n_electrons=4,
    noons=noons,
    orbital_energies=orbital_energies
)

print(molecule)

MoleculeInfo(
 - MolecularHamiltonian(
    * constant_coeff : 0.8327012878181406
    * integrals shape
       ** one_body_integrals : (2, 2)
       ** two_body_integrals : (2, 2, 2, 2)
   )
 - n_electrons = 4
 - noons = [0.8848039286953441, -0.08447307594996871, 1.6480322409077044, -0.046173838659272236, -0.3020002857619635, -0.9953108107712418, 1.079076148072277, -0.029582851908594103, 0.44148913338331186, 0.3443574849031922]
 - orbital energies = [-0.9876259427659785, 1.0905719998668333, -1.2663837739825259, 0.8223303637867233, -1.4392212088596434, 2.123483518965686, -0.752743106961605, 0.3995784384211595, 0.5625574139135663, -0.2924654286629466]
)

restrict_active_space(threshold_1: float | None = 0.02, threshold_2: float | None = 0.001)

Same method as the MolecularHamiltonian method select_active_space(), except it also modifies all the molecule parameters accordingly (NOONs, orbital energies, and number of electrons).

For more information, see select_active_space() documentation.

Parameters:

threshold_1 (Optional[float]) – The upper threshold \(\varepsilon_1\) on the NOON of an active orbital.
threshold_2 (Optional[float]) – The lower threshold \(\varepsilon_2\) on the NOON of an active orbital.