qat.fermion.chemistry.wrapper.MoleculeInfo

class qat.fermion.chemistry.wrapper.MoleculeInfo(hamiltonian: MolecularHamiltonian, n_electrons: int, noons: Union[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 : 0.4096651275295301
    * integrals shape
       ** one_body_integrals : (2, 2)
       ** two_body_integrals : (2, 2, 2, 2)
   )
 - n_electrons = 4
 - noons = [0.2508015021932889, -0.5756450684139017, -0.1606462623557909, -0.05005915198580562, -0.34108752423527294, 4.631947798728623e-05, 0.3820591846665703, 0.4562267235643896, -2.1812835843846727, 0.7305267823964061]
 - orbital energies = [0.1926751777996219, -0.037325803941252324, 1.0958122591235606, -0.3483155758051236, -0.10065785764858304, 1.0247360240943677, -0.964350940795339, 0.3927438392560454, -0.4565369248855421, -0.4249934831632985]
)

restrict_active_space(threshold_1: Optional[float] = 0.02, threshold_2: Optional[float] = 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.