qat.opt.circuit_generator.CircuitGenerator

class qat.opt.circuit_generator.CircuitGenerator

Class for circuit generation interface from a diagonal observable.

abstract get_observable()

Generates a cost Hamiltonian encoding a problem or a cost function. This cost Hamiltonian will be used as a basis to build a digital Ansatz.

qaoa_ansatz(depth, cnots=True, strategy='coloring', to_circ_args=None, **kwargs)

Generates a QAOA Ansatz using the cost observable returned by the abstract method get_observable.

Warning

When setting the cnots option to False, the circuit might make use of generalized many-qubits Z rotations. In that case, you might want to instantiate your variational plugins using a gate set that contains definition of these gates. If not, some matrices in the circuit structure will be missing and some QPUs may not be able to handle the circuit.

The following piece of code should allow you to link the correct gate set to a variational plugin:

from qat.plugins import ScipyMinimizePlugin
from qat.vsolve.ansatz import get_qaoa_gate_set

# This plugin will no be able to bind variables inside a
# job generated with cnot set to False!
my_plugin = ScipyMinimizePlugin()

# This plugin can now be used with job generated with the
# cnots option sets to False!
my_plugin = ScipyMinimizePlugin(gate_set=get_qaoa_gate_set())
Parameters

  • depth (int) – the depth of the Ansatz

  • strategy (str) – the strategy to adopt to generate the circuit. Possible strategies are “default” or “coloring”. The “coloring” strategy uses a greedy coloring heuristics to try to optimize the overall depth of the Ansatz. Default is “default” which synthesize the circuit without optimizing the term ordering.

  • cnots (optional, bool) – If set to True the Ansatz will only use CNOT gates. If set to False, some abstract gates will be used to generate collective pauli rotations, resulting in a lower gate count. Defaults to True.

  • **kwargs – optional arguments that will be transfered to the job’s constructor (e.g nbshots, etc).

Returns

a qlm job, ready to run

Return type

Job