qiskit.algorithms.AmplificationProblem¶

class AmplificationProblem(oracle, state_preparation=None, grover_operator=None, post_processing=None, objective_qubits=None, is_good_state=None)[source]¶

The amplification problem is the input to amplitude amplification algorithms, like Grover.

This class contains all problem-specific information required to run an amplitude amplification algorithm. It minimally contains the Grover operator. It can further hold some post processing on the optimal bitstring.

Parameters

oracle (QuantumCircuit) – The oracle reflecting about the bad states.
state_preparation (Optional[QuantumCircuit]) – A circuit preparing the input state, referred to as \(\mathcal{A}\). If None, a layer of Hadamard gates is used.
grover_operator (Optional[QuantumCircuit]) – The Grover operator \(\mathcal{Q}\) used as unitary in the phase estimation circuit. If None, this operator is constructed from the oracle and state_preparation.
post_processing (Optional[Callable[[str], Any]]) – A mapping applied to the most likely bitstring.
objective_qubits (Union[int, List[int], None]) – If set, specifies the indices of the qubits that should be measured. If None, all qubits will be measured. The is_good_state function will be applied on the measurement outcome of these qubits.
is_good_state (Optional[Callable[[str], bool]]) – A function to check whether a string represents a good state.

__init__(oracle, state_preparation=None, grover_operator=None, post_processing=None, objective_qubits=None, is_good_state=None)[source]¶

Parameters

oracle (QuantumCircuit) – The oracle reflecting about the bad states.
state_preparation (Optional[QuantumCircuit]) – A circuit preparing the input state, referred to as \(\mathcal{A}\). If None, a layer of Hadamard gates is used.
grover_operator (Optional[QuantumCircuit]) – The Grover operator \(\mathcal{Q}\) used as unitary in the phase estimation circuit. If None, this operator is constructed from the oracle and state_preparation.
post_processing (Optional[Callable[[str], Any]]) – A mapping applied to the most likely bitstring.
objective_qubits (Union[int, List[int], None]) – If set, specifies the indices of the qubits that should be measured. If None, all qubits will be measured. The is_good_state function will be applied on the measurement outcome of these qubits.
is_good_state (Optional[Callable[[str], bool]]) – A function to check whether a string represents a good state.

Methods

__init__(oracle[, state_preparation, …])

type oracle: QuantumCircuit

Attributes

`grover_operator`	Get the \(\mathcal{Q}\) operator, or Grover operator.
`is_good_state`	Check whether a provided bitstring is a good state or not.
`objective_qubits`	The indices of the objective qubits.
`oracle`	Return the oracle.
`post_processing`	Apply post processing to the input value.
`state_preparation`	Get the state preparation operator \(\mathcal{A}\).

property grover_operator¶

Get the \(\mathcal{Q}\) operator, or Grover operator.

If the Grover operator is not set, we try to build it from the \(\mathcal{A}\) operator and objective_qubits. This only works if objective_qubits is a list of integers.

Return type: Optional[QuantumCircuit]
Returns: The Grover operator, or None if neither the Grover operator nor the \(\mathcal{A}\) operator is set.

property is_good_state¶

Check whether a provided bitstring is a good state or not.

Return type: Callable[[str], float]
Returns: A callable that takes in a bitstring and returns True if the measurement is a good state, False otherwise.

property objective_qubits¶

The indices of the objective qubits.

Return type: List[int]
Returns: The indices of the objective qubits as list of integers.

property oracle¶

Return the oracle.

Return type: QuantumCircuit
Returns: The oracle.

property post_processing¶

Apply post processing to the input value.

Return type: Callable[[str], Any]
Returns: A handle to the post processing function. Acts as identity by default.

property state_preparation¶

Get the state preparation operator \(\mathcal{A}\).

Return type: QuantumCircuit
Returns: The \(\mathcal{A}\) operator as QuantumCircuit.