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 : 0.21001301673612804
    * integrals shape
       ** one_body_integrals : (2, 2)
       ** two_body_integrals : (2, 2, 2, 2)
   )
 - n_electrons = 4
 - noons = [-0.5595268370603503, -0.5873847145459093, 1.3495702765913749, 0.4928812750324355, -0.5491382580714882, -0.47072391542551434, -1.762767791527091, 0.09637198556102475, -0.7654915442737239, -0.20159435490481556]
 - orbital energies = [0.6406121631422277, 0.7749502013971262, 2.1878531986349135, -2.6877747369098763, 1.9755856124387632, -0.45974232841639623, 0.4210955155860996, -1.1646866665996374, 0.09995058437474011, 1.6013705967577683]
)

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.