QAOAAnsatz

class qiskit.circuit.library.QAOAAnsatz(cost_operator=None, reps=1, initial_state=None, mixer_operator=None, name='QAOA', flatten=None)

GitHub

Bases: EvolvedOperatorAnsatz

A generalized QAOA quantum circuit with a support of custom initial states and mixers.

References

[1]: Farhi et al., A Quantum Approximate Optimization Algorithm.

arXiv:1411.4028

Parameters

cost_operator (BaseOperator or OperatorBase, optional) – The operator representing the cost of the optimization problem, denoted as $U(C, \gamma)$ in the original paper. Must be set either in the constructor or via property setter.
reps (int) – The integer parameter p, which determines the depth of the circuit, as specified in the original paper, default is 1.
initial_state (QuantumCircuit, optional) – An optional initial state to use. If None is passed then a set of Hadamard gates is applied as an initial state to all qubits.
mixer_operator (BaseOperator or OperatorBase or QuantumCircuit, optional) – An optional custom mixer to use instead of the global X-rotations, denoted as $U(B, \beta)$ in the original paper. Can be an operator or an optionally parameterized quantum circuit.
name (str) – A name of the circuit, default ‘qaoa’
flatten (bool | None) – Set this to True to output a flat circuit instead of nesting it inside multiple layers of gate objects. By default currently the contents of the output circuit will be wrapped in nested objects for cleaner visualization. However, if you’re using this circuit for anything besides visualization its strongly recommended to set this flag to True to avoid a large performance overhead for parameter binding.

Attributes

cost_operator

Returns an operator representing the cost of the optimization problem.

Returns

cost operator.

Return type

BaseOperator or OperatorBase

initial_state

Returns an optional initial state as a circuit

mixer_operator

Returns an optional mixer operator expressed as an operator or a quantum circuit.

Returns

mixer operator or circuit.

Return type

BaseOperator or OperatorBase or QuantumCircuit, optional

num_qubits

operators

The operators that are evolved in this circuit.

Returns

The operators to be evolved

(and circuits) in this ansatz.

Return type

List[Union[BaseOperator, OperatorBase, QuantumCircuit]]

parameter_bounds

The parameter bounds for the unbound parameters in the circuit.

Returns

A list of pairs indicating the bounds, as (lower, upper). None indicates an unbounded parameter in the corresponding direction. If None is returned, problem is fully unbounded.

reps

Returns the reps parameter, which determines the depth of the circuit.

name

Type: str

A human-readable name for the circuit.

Example

from qiskit import QuantumCircuit
 
qc = QuantumCircuit(2, 2, name="my_circuit")
print(qc.name)

my_circuit