quri_parts.openfermion.ansatz.kupccgsd module#

class KUpCCGSD(n_spin_orbitals, k=1, fermion_qubit_mapping=<quri_parts.openfermion.transforms.OpenFermionJordanWignerFactory object>, trotter_number=1, delta_sz=0, singlet_excitation=False)#

Bases: ImmutableLinearMappedUnboundParametricQuantumCircuit

k-unitary pair coupled-cluster generalized singles and doubles (k-UpCCGSD) ansatz. The ansatz consists of the exponentials of generalized single excitation and pair double excitation operators decomposed by first- order Trotter product formula repeated k times. The term “generalized” means excitation operators created regardless of the occupied orbitals. Here the double excitations are limited to ‘pair’ excitation, which means two electrons from one spatial orbital to another.

Ref:

Lee et al., Generalized Unitary Coupled Cluster Wave functions for Quantum Computation, J. Chem. Theory Comput. 15, 311–324 (2019), arXiv:1810.02327.

PennyLane’s documentations, qml.kUpCCGSD

Parameters:

  • n_spin_orbitals (int) – Number of spin orbitals.

  • k (int) – Number of repetitions.

  • fermion_qubit_mapping (OpenFermionMappingMethods) – Mapping from FermionOperator to Operator

  • trotter_number (int) – Number for first-order Trotter product formula.

  • delta_sz (int) – Changes of spin in the excitation.

  • singlet_excitation (bool) – If True, single excitations that start from and end at the same spatial orbitals will share the same circuit parameter. For the double excitations, the excitations are paired, so the singlet excitation condition is satisfied automatically.