qiskit.aqua.algorithms.IQPE¶

class IQPE(operator=None, state_in=None, num_time_slices=1, num_iterations=1, expansion_mode='suzuki', expansion_order=2, shallow_circuit_concat=False, quantum_instance=None)[source]¶

The Iterative Quantum Phase Estimation algorithm.

IQPE, as its name suggests, iteratively computes the phase so as to require fewer qubits. It has the same set of parameters as QPE, except for the number of ancillary qubits num_ancillae, being replaced by num_iterations and that an Inverse Quantum Fourier Transform (IQFT) is not used for IQPE.

Reference:

[1]: Dobsicek et al. (2006), Arbitrary accuracy iterative phase estimation algorithm as a two: qubit benchmark, arxiv/quant-ph/0610214

Parameters

operator (Union[OperatorBase, LegacyBaseOperator, None]) – The hamiltonian Operator
state_in (Union[QuantumCircuit, InitialState, None]) – An InitialState component representing an initial quantum state.
num_time_slices (int) – The number of time slices, has a minimum value of 1.
num_iterations (int) – The number of iterations, has a minimum value of 1.
expansion_mode (str) – The expansion mode (‘trotter’|’suzuki’)
expansion_order (int) – The suzuki expansion order, has a min. value of 1.
shallow_circuit_concat (bool) – Set True to use shallow (cheap) mode for circuit concatenation of evolution slices. By default this is False.
quantum_instance (Union[QuantumInstance, Backend, BaseBackend, None]) – Quantum Instance or Backend

__init__(operator=None, state_in=None, num_time_slices=1, num_iterations=1, expansion_mode='suzuki', expansion_order=2, shallow_circuit_concat=False, quantum_instance=None)[source]¶

Parameters

operator (Union[OperatorBase, LegacyBaseOperator, None]) – The hamiltonian Operator
state_in (Union[QuantumCircuit, InitialState, None]) – An InitialState component representing an initial quantum state.
num_time_slices (int) – The number of time slices, has a minimum value of 1.
num_iterations (int) – The number of iterations, has a minimum value of 1.
expansion_mode (str) – The expansion mode (‘trotter’|’suzuki’)
expansion_order (int) – The suzuki expansion order, has a min. value of 1.
shallow_circuit_concat (bool) – Set True to use shallow (cheap) mode for circuit concatenation of evolution slices. By default this is False.
quantum_instance (Union[QuantumInstance, Backend, BaseBackend, None]) – Quantum Instance or Backend

Methods

`__init__`([operator, state_in, …])	type operator `Union`[`OperatorBase`, `LegacyBaseOperator`, `None`]
`compute_minimum_eigenvalue`([operator, …])	Computes minimum eigenvalue.
`construct_circuit`([k, omega, measurement])	Construct the kth iteration Quantum Phase Estimation circuit.
`run`([quantum_instance])	Execute the algorithm with selected backend.
`set_backend`(backend, **kwargs)	Sets backend with configuration.
`supports_aux_operators`()	Whether computing the expectation value of auxiliary operators is supported.

Attributes

`aux_operators`	Returns aux operators
`backend`	Returns backend.
`operator`	Returns operator
`quantum_instance`	Returns quantum instance.
`random`	Return a numpy random.

property aux_operators¶

Returns aux operators

Return type: Optional[List[Union[OperatorBase, LegacyBaseOperator]]]

property backend¶

Returns backend.

Return type: Union[Backend, BaseBackend]

compute_minimum_eigenvalue(operator=None, aux_operators=None)[source]¶

Computes minimum eigenvalue. Operator and aux_operators can be supplied here and if not None will override any already set into algorithm so it can be reused with different operators. While an operator is required by algorithms, aux_operators are optional. To ‘remove’ a previous aux_operators array use an empty list here.

Parameters

operator (Union[OperatorBase, LegacyBaseOperator, None]) – If not None replaces operator in algorithm
aux_operators (Optional[List[Union[OperatorBase, LegacyBaseOperator]]]) – If not None replaces aux_operators in algorithm

Return type

MinimumEigensolverResult

Returns

MinimumEigensolverResult

construct_circuit(k=None, omega=0, measurement=False)[source]¶

Construct the kth iteration Quantum Phase Estimation circuit.

For details of parameters, please see Fig. 2 in https://arxiv.org/pdf/quant-ph/0610214.pdf.

Parameters

k (Optional[int]) – the iteration idx.
omega (float) – the feedback angle.
measurement (bool) – Boolean flag to indicate if measurement should be included in the circuit.

Returns

the quantum circuit per iteration

Return type

QuantumCircuit

property operator¶

Returns operator

Return type: Union[OperatorBase, LegacyBaseOperator, None]

property quantum_instance¶

Returns quantum instance.

Return type: Optional[QuantumInstance]

property random¶: Return a numpy random.

run(quantum_instance=None, **kwargs)¶

Execute the algorithm with selected backend.

Parameters

quantum_instance (Union[QuantumInstance, Backend, BaseBackend, None]) – the experimental setting.
kwargs (dict) – kwargs

Returns

results of an algorithm.

Return type

dict

Raises

AquaError – If a quantum instance or backend has not been provided

set_backend(backend, **kwargs)¶

Sets backend with configuration.

Return type: None

classmethod supports_aux_operators()¶

Whether computing the expectation value of auxiliary operators is supported.

If the minimum eigensolver computes an eigenstate of the main operator then it can compute the expectation value of the aux_operators for that state. Otherwise they will be ignored.

Return type: bool
Returns: True if aux_operator expectations can be evaluated, False otherwise