qiskit.chemistry.components.variational_forms.UCCSD

class UCCSD(num_orbitals, num_particles, reps=1, active_occupied=None, active_unoccupied=None, initial_state=None, qubit_mapping='parity', two_qubit_reduction=True, num_time_slices=1, shallow_circuit_concat=True, z2_symmetries=None, method_singles='both', method_doubles='ucc', excitation_type='sd', same_spin_doubles=True, skip_commute_test=False)

This trial wavefunction is a Unitary Coupled-Cluster Single and Double excitations variational form. For more information, see https://arxiv.org/abs/1805.04340 And for the singlet q-UCCD (full) and pair q-UCCD) see: https://arxiv.org/abs/1911.10864

Constructor.

Parameters

• num_orbitals (int) – number of spin orbitals, has a min. value of 1.

• num_particles (Union[List[int], int]) – number of particles, if it is a list, the first number is alpha and the second number if beta.

• reps (int) – number of repetitions of basic module, has a min. value of 1.

• active_occupied (Optional[List[int]]) – list of occupied orbitals to consider as active space.

• active_unoccupied (Optional[List[int]]) – list of unoccupied orbitals to consider as active space.

• initial_state (Optional[InitialState]) – An initial state object.

• qubit_mapping (str) – qubit mapping type.

• two_qubit_reduction (bool) – two qubit reduction is applied or not.

• num_time_slices (int) – parameters for dynamics, has a min. value of 1.

• shallow_circuit_concat (bool) – indicate whether to use shallow (cheap) mode for circuit concatenation.

• z2_symmetries (Optional[Z2Symmetries]) – represent the Z2 symmetries, including symmetries, sq_paulis, sq_list, tapering_values, and cliffords.

• method_singles (str) – specify the single excitation considered. ‘alpha’, ‘beta’, ‘both’ only alpha or beta spin-orbital single excitations or both (all of them).

• method_doubles (str) – specify the single excitation considered. ‘ucc’ (conventional ucc), succ (singlet ucc), succ_full (singlet ucc full), pucc (pair ucc).

• excitation_type (str) – specify the excitation type ‘sd’, ‘s’, ‘d’ respectively for single and double, only single, only double excitations.

• same_spin_doubles (bool) – enable double excitations of the same spin.

• skip_commute_test (bool) –

  when tapering excitation operators we test and exclude any that do

  not commute with symmetries. This test can be skipped to include all tapered excitation operators whether they commute or not.

  Raises:

  ValueError: Num particles list is not 2 entries

__init__(num_orbitals, num_particles, reps=1, active_occupied=None, active_unoccupied=None, initial_state=None, qubit_mapping='parity', two_qubit_reduction=True, num_time_slices=1, shallow_circuit_concat=True, z2_symmetries=None, method_singles='both', method_doubles='ucc', excitation_type='sd', same_spin_doubles=True, skip_commute_test=False)

Constructor.

Parameters

• num_orbitals (int) – number of spin orbitals, has a min. value of 1.

• num_particles (Union[List[int], int]) – number of particles, if it is a list, the first number is alpha and the second number if beta.

• reps (int) – number of repetitions of basic module, has a min. value of 1.

• active_occupied (Optional[List[int]]) – list of occupied orbitals to consider as active space.

• active_unoccupied (Optional[List[int]]) – list of unoccupied orbitals to consider as active space.

• initial_state (Optional[InitialState]) – An initial state object.

• qubit_mapping (str) – qubit mapping type.

• two_qubit_reduction (bool) – two qubit reduction is applied or not.

• num_time_slices (int) – parameters for dynamics, has a min. value of 1.

• shallow_circuit_concat (bool) – indicate whether to use shallow (cheap) mode for circuit concatenation.

• z2_symmetries (Optional[Z2Symmetries]) – represent the Z2 symmetries, including symmetries, sq_paulis, sq_list, tapering_values, and cliffords.

• method_singles (str) – specify the single excitation considered. ‘alpha’, ‘beta’, ‘both’ only alpha or beta spin-orbital single excitations or both (all of them).

• method_doubles (str) – specify the single excitation considered. ‘ucc’ (conventional ucc), succ (singlet ucc), succ_full (singlet ucc full), pucc (pair ucc).

• excitation_type (str) – specify the excitation type ‘sd’, ‘s’, ‘d’ respectively for single and double, only single, only double excitations.

• same_spin_doubles (bool) – enable double excitations of the same spin.

• skip_commute_test (bool) –

  when tapering excitation operators we test and exclude any that do

  not commute with symmetries. This test can be skipped to include all tapered excitation operators whether they commute or not.

  Raises:

  ValueError: Num particles list is not 2 entries

Methods

__init__(num_orbitals, num_particles[, …])	Constructor.
compute_excitation_lists(num_particles, …)	Computes single and double excitation lists.
compute_excitation_lists_singlet(double_exc, …)	Outputs the list of lists of grouped excitation.
construct_circuit(parameters[, q])	Construct the variational form, given its parameters.
get_entangler_map(map_type, num_qubits[, offset])	returns entangler map
group_excitations(list_de, num_orbitals)	Groups the excitations and gives out the remaining ones in the list_de_temp list because those excitations are controlled by the same parameter in full singlet UCCSD unlike in usual UCCSD where every excitation has its own parameter.
group_excitations_if_same_ao(list_de, …)	Define that, given list of double excitations list_de and number of spin-orbitals num_orbitals, which excitations involve the same spatial orbitals for full singlet UCCSD.
manage_hopping_operators()	Triggers the adaptive behavior of this UCCSD instance.
order_labels_for_hopping_ops(double_exc, gde)	Orders the hopping operators according to the grouped excitations for the full singlet UCCSD.
pop_hopping_operator()	Pops the hopping operator that was added last.
push_hopping_operator(excitation)	Pushes a new hopping operator.
same_ao_double_excitation_block_spin(de_1, …)	Regroups the excitations that involve same spatial orbitals for example, with labeling.
validate_entangler_map(entangler_map, num_qubits)	validate entangler map

Attributes

double_excitations	Getter of double excitation list :returns: double excitation list :rtype: list[list[int]]
excitation_pool	Returns the full list of available excitations (called the pool).
num_parameters	Number of parameters of the variational form.
num_qubits	Number of qubits of the variational form.
parameter_bounds	Parameter bounds.
preferred_init_points	Getter of preferred initial points based on the given initial state.
setting
single_excitations	Getter of single excitation list :returns: single excitation list :rtype: list[list[int]]
support_parameterized_circuit	Whether or not the sub-class support parameterized circuit.

static compute_excitation_lists(num_particles, num_orbitals, active_occ_list=None, active_unocc_list=None, same_spin_doubles=True, method_singles='both', method_doubles='ucc', excitation_type='sd')

Computes single and double excitation lists.

Parameters

• num_particles (Union(list, int)) – number of particles, if it is a tuple, the first number is alpha and the second number if beta.

• num_orbitals (int) – Total number of spin orbitals

• active_occ_list (list) – List of occupied orbitals to include, indices are 0 to n where n is max(num_alpha, num_beta)

• active_unocc_list (list) – List of unoccupied orbitals to include, indices are 0 to m where m is num_orbitals // 2 - min(num_alpha, num_beta)

• same_spin_doubles (bool) – True to include alpha,alpha and beta,beta double excitations as well as alpha,beta pairings. False includes only alpha,beta

• excitation_type (str) – choose ‘sd’, ‘s’, ‘d’ to compute q-UCCSD, q-UCCS, q-UCCD excitation lists

• method_singles (str) – specify type of single excitations, ‘alpha’, ‘beta’, ‘both’ only alpha or beta spin-orbital single excitations or both (all single excitations)

• method_doubles (str) – choose method for double excitations ‘ucc’ (conventional ucc), ‘succ’ (singlet ucc), ‘succ_full’ (singlet ucc full), ‘pucc’ (pair ucc)

Returns

Single excitation list list: Double excitation list

Return type

list

Raises

• ValueError – invalid setting of number of particles

• ValueError – invalid setting of number of orbitals

static compute_excitation_lists_singlet(double_exc, num_orbitals)

Outputs the list of lists of grouped excitation. A single list inside is controlled by the same parameter theta.

Parameters

• double_exc (list) – exc.group. [[0,1,2,3], […]]

• num_orbitals (int) – number of molecular orbitals

Returns

de_groups grouped excitations

Return type

list

construct_circuit(parameters, q=None)

Construct the variational form, given its parameters.

Parameters

• parameters (Union(numpy.ndarray, list[Parameter], ParameterVector)) – circuit parameters

• q (QuantumRegister, optional) – Quantum Register for the circuit.

Returns

a quantum circuit with given parameters

Return type

QuantumCircuit

Raises

ValueError – the number of parameters is incorrect.

property double_excitations

Getter of double excitation list :returns: double excitation list :rtype: list[list[int]]

property excitation_pool

Returns the full list of available excitations (called the pool).

Return type

List[WeightedPauliOperator]

static get_entangler_map(map_type, num_qubits, offset=0)

returns entangler map

static group_excitations(list_de, num_orbitals)

Groups the excitations and gives out the remaining ones in the list_de_temp list because those excitations are controlled by the same parameter in full singlet UCCSD unlike in usual UCCSD where every excitation has its own parameter.

Parameters

• list_de (list) – list of the double excitations grouped

• num_orbitals (int) – number of spin-orbitals (qubits)

Returns

list_same_ao_group, list_de_temp, the grouped double_exc (that involve same spatial orbitals)

Return type

tuple

static group_excitations_if_same_ao(list_de, num_orbitals)

Define that, given list of double excitations list_de and number of spin-orbitals num_orbitals, which excitations involve the same spatial orbitals for full singlet UCCSD.

Parameters

• list_de (list) – list of double exc

• num_orbitals (int) – number of spin-orbitals

Returns

grouped list of excitations

Return type

list

manage_hopping_operators()

Triggers the adaptive behavior of this UCCSD instance. This function is used by the Adaptive VQE algorithm. It stores the full list of available hopping operators in a so called “excitation pool” and clears the previous list to be empty. Furthermore, the depth is asserted to be 1 which is required by the Adaptive VQE algorithm.

property num_parameters

Number of parameters of the variational form.

Returns

An integer indicating the number of parameters.

Return type

int

property num_qubits

Number of qubits of the variational form.

Returns

An integer indicating the number of qubits.

Return type

int

static order_labels_for_hopping_ops(double_exc, gde)

Orders the hopping operators according to the grouped excitations for the full singlet UCCSD.

Parameters

• double_exc (list) – list of double excitations

• gde (list of lists) – list of grouped excitations for full singlet UCCSD

Returns

ordered_labels to order hopping ops

Return type

list

property parameter_bounds

Parameter bounds.

Returns

A list of pairs indicating the bounds, as (lower, upper). None indicates an unbounded parameter in the corresponding direction. If None is returned, problem is fully unbounded.

Return type

list

pop_hopping_operator()

Pops the hopping operator that was added last.

property preferred_init_points

Getter of preferred initial points based on the given initial state.

push_hopping_operator(excitation)

Pushes a new hopping operator.

Parameters

excitation (WeightedPauliOperator) – the new hopping operator to be added

static same_ao_double_excitation_block_spin(de_1, de_2, num_orbitals)

Regroups the excitations that involve same spatial orbitals for example, with labeling.

2— —5 1— —4 0-o- -o-3

excitations [0,1,3,5] and [0,2,3,4] are controlled by the same parameter in the full singlet UCCSD unlike in usual UCCSD where every excitation is controlled by independent parameter.

Parameters

• de_1 (list) – double exc in block spin [ from to from to ]

• de_2 (list) – double exc in block spin [ from to from to ]

• num_orbitals (int) – number of molecular orbitals

Returns

says if given excitation involves same spatial orbitals 1 = yes, 0 = no.

Return type

int

property setting

property single_excitations

Getter of single excitation list :returns: single excitation list :rtype: list[list[int]]

property support_parameterized_circuit

Whether or not the sub-class support parameterized circuit.

Returns

indicate the sub-class support parameterized circuit

Return type

boolean

static validate_entangler_map(entangler_map, num_qubits)

validate entangler map