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 : 0.04177870736814948
    * integrals shape
       ** one_body_integrals : (2, 2)
       ** two_body_integrals : (2, 2, 2, 2)
   )
 - n_electrons = 4
 - noons = [-1.0100533009275747, 1.3651792062089054, -1.5250480359711358, -0.4129916783805803, 1.3941035820146916, 0.5439404125579158, -0.16433624458188872, 0.7107864457183962, -1.7197232855690283, 0.4803447042010155]
 - orbital energies = [-1.1789943085418724, 0.334696975191843, -0.2805374310878261, 1.054967376194832, 0.33372695417310516, -0.9498379659466147, -1.3836350430255007, -1.1008442001537453, 2.2735951029161745, 2.156667523724669]
)

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.