AmplificationProblem

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

Bases: object

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 | Statevector) – The oracle reflecting about the bad states.

• state_preparation (QuantumCircuit | None) – A circuit preparing the input state, referred to as $\mathcal{A}$. If None, a layer of Hadamard gates is used.

• grover_operator (QuantumCircuit | None) – 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 (Callable[[str], Any] | None) – A mapping applied to the most likely bitstring.

• objective_qubits (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 (Callable[[str], bool] | list[int] | list[str] | Statevector | None) – A function to check whether a string represents a good state. By default if the oracle argument has an evaluate_bitstring method (currently only provided by the PhaseOracle class) this will be used, otherwise this kwarg is required and must be specified.

Attributes

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.

Returns:

The Grover operator, or None if neither the Grover operator nor the $\mathcal{A}$ operator is set.

is_good_state

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

Returns:

A callable that takes in a bitstring and returns True if the measurement is a good state, False otherwise.

objective_qubits

The indices of the objective qubits.

Returns:

The indices of the objective qubits as list of integers.

oracle

Return the oracle.

Returns:

The oracle.

post_processing

Apply post processing to the input value.

Returns:

A handle to the post processing function. Acts as identity by default.

state_preparation

Get the state preparation operator $\mathcal{A}$.

Returns:

The $\mathcal{A}$ operator as QuantumCircuit.