qiskit.algorithms.AmplificationProblem

class AmplificationProblem(oracle, state_preparation=None, grover_operator=None, post_processing=None, objective_qubits=None, is_good_state=None)

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)

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`


`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 $\mathcal{A}$ .

\mathcal{Q}

\mathcal{A}

Return type

Optional [QuantumCircuit]

Returns

\mathcal{A}

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.

The indices of the objective qubits.

Return type

List [int]

Returns

The indices of the objective qubits as list of integers.

Return the oracle.

Return type

QuantumCircuit

Returns

The oracle.

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.

\mathcal{A}

Return type

QuantumCircuit

Returns

\mathcal{A}

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