# qiskit.aqua.algorithms.QPE¶

class QPE(operator=None, state_in=None, iqft=None, num_time_slices=1, num_ancillae=1, expansion_mode='trotter', expansion_order=1, shallow_circuit_concat=False, quantum_instance=None)[código fonte]

The Quantum Phase Estimation algorithm.

QPE (also sometimes abbreviated as PEA, for Phase Estimation Algorithm), has two quantum registers, control and target, where the control consists of several qubits initially put in uniform superposition, and the target a set of qubits prepared in an eigenstate (often a guess of the eigenstate) of the unitary operator of a quantum system. QPE then evolves the target under the control using dynamics on the unitary operator. The information of the corresponding eigenvalue is then ‘kicked-back’ into the phases of the control register, which can then be deconvoluted by an Inverse Quantum Fourier Transform (IQFT), and measured for read-out in binary decimal format. QPE also requires a reasonably good estimate of the eigen wave function to start the process. For example, when estimating molecular ground energies in chemistry, the Hartree-Fock method could be used to provide such trial eigen wave functions.

Parâmetros
• operator (Union[OperatorBase, LegacyBaseOperator, None]) – The Hamiltonian Operator

• state_in (Union[QuantumCircuit, InitialState, None]) – An optional InitialState component representing an initial quantum state. None may be supplied.

• iqft (Optional[QuantumCircuit]) – A Inverse Quantum Fourier Transform component

• num_time_slices (int) – The number of time slices, has a minimum value of 1.

• num_ancillae (int) – The number of ancillary qubits to use for the measurement, has a min. 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. See qiskit.aqua.operators.common.evolution_instruction() for more information.

• quantum_instance (Union[QuantumInstance, Backend, BaseBackend, None]) – Quantum Instance or Backend

__init__(operator=None, state_in=None, iqft=None, num_time_slices=1, num_ancillae=1, expansion_mode='trotter', expansion_order=1, shallow_circuit_concat=False, quantum_instance=None)[código fonte]
Parâmetros
• operator (Union[OperatorBase, LegacyBaseOperator, None]) – The Hamiltonian Operator

• state_in (Union[QuantumCircuit, InitialState, None]) – An optional InitialState component representing an initial quantum state. None may be supplied.

• iqft (Optional[QuantumCircuit]) – A Inverse Quantum Fourier Transform component

• num_time_slices (int) – The number of time slices, has a minimum value of 1.

• num_ancillae (int) – The number of ancillary qubits to use for the measurement, has a min. 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. See qiskit.aqua.operators.common.evolution_instruction() for more information.

• quantum_instance (Union[QuantumInstance, Backend, BaseBackend, None]) – Quantum Instance or Backend

Methods

 __init__([operator, state_in, iqft, …]) type operator Union[OperatorBase, LegacyBaseOperator, None] compute_minimum_eigenvalue([operator, …]) Computes minimum eigenvalue. construct_circuit([measurement]) Construct circuit. run([quantum_instance]) Execute the algorithm with selected backend. set_backend(backend, **kwargs) Sets backend with configuration. 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

Tipo de retorno

Optional[List[Union[OperatorBase, LegacyBaseOperator]]]

property backend

Returns backend.

Tipo de retorno

Union[Backend, BaseBackend]

compute_minimum_eigenvalue(operator=None, aux_operators=None)[código fonte]

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.

Parâmetros
• 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

Tipo de retorno

MinimumEigensolverResult

Retorna

MinimumEigensolverResult

construct_circuit(measurement=False)[código fonte]

Construct circuit.

Parâmetros

measurement (bool) – Boolean flag to indicate if measurement should be included in the circuit.

Retorna

quantum circuit.

Tipo de retorno

QuantumCircuit

property operator

Returns operator

Tipo de retorno

Optional[LegacyBaseOperator]

property quantum_instance

Returns quantum instance.

Tipo de retorno

Optional[QuantumInstance]

property random

Return a numpy random.

run(quantum_instance=None, **kwargs)

Execute the algorithm with selected backend.

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

• kwargs (dict) – kwargs

Retorna

results of an algorithm.

Tipo de retorno

dict

Levanta

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

set_backend(backend, **kwargs)

Sets backend with configuration.

Tipo de retorno

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.

Tipo de retorno

bool

Retorna

True if aux_operator expectations can be evaluated, False otherwise