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)
The Iterative Quantum Phase Estimation algorithm.
IQPE, as its name suggests, iteratively computes the phase so as to require fewer qubits. It takes 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 (
Optional[InitialState]) – 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,BaseBackend,None]) – Quantum Instance or Backend
Attributes
aux_operators
Type: Optional[List[Union[qiskit.aqua.operators.operator_base.OperatorBase, qiskit.aqua.operators.legacy.base_operator.LegacyBaseOperator]]]
Returns aux operators
Return type
Optional[List[Union[OperatorBase, LegacyBaseOperator]]]
backend
operator
Type: Optional[Union[qiskit.aqua.operators.operator_base.OperatorBase, qiskit.aqua.operators.legacy.base_operator.LegacyBaseOperator]]
Returns operator
Return type
Union[OperatorBase, LegacyBaseOperator, None]
quantum_instance
Type: Union[None, qiskit.aqua.quantum_instance.QuantumInstance]
Returns quantum instance.
Return type
Optional[QuantumInstance]
random
Return a numpy random.
Methods
compute_minimum_eigenvalue
IQPE.compute_minimum_eigenvalue(operator=None, aux_operators=None)
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
Returns
MinimumEigensolverResult
construct_circuit
IQPE.construct_circuit(k=None, omega=0, measurement=False)
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
run
IQPE.run(quantum_instance=None, **kwargs)
Execute the algorithm with selected backend.
Parameters
- quantum_instance (
Union[QuantumInstance,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
IQPE.set_backend(backend, **kwargs)
Sets backend with configuration.
Return type
None
supports_aux_operators
IQPE.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