DAGDependency

class DAGDependency

Bases: object

Object to represent a quantum circuit as a directed acyclic graph via operation dependencies (i.e. lack of commutation).

The nodes in the graph are operations represented by quantum gates. The edges correspond to non-commutation between two operations (i.e. a dependency). A directed edge from node A to node B means that operation A does not commute with operation B. The object’s methods allow circuits to be constructed.

The nodes in the graph have the following attributes: ‘operation’, ‘successors’, ‘predecessors’.

Example:

Bell circuit with no measurement.

      ┌───┐
qr_0: ┤ H ├──■──
      └───┘┌─┴─┐
qr_1: ─────┤ X ├
           └───┘

The dependency DAG for the above circuit is represented by two nodes. The first one corresponds to Hadamard gate, the second one to the CNOT gate as the gates do not commute there is an edge between the two nodes.

Reference:

[1] Iten, R., Moyard, R., Metger, T., Sutter, D. and Woerner, S., 2020. Exact and practical pattern matching for quantum circuit optimization. arXiv:1909.05270

Create an empty DAGDependency.

Methods

add_clbits	Add individual clbit wires.
add_creg	Add clbits in a classical register.
add_op_node	Add a DAGDepNode to the graph and update the edges.
add_qreg	Add qubits in a quantum register.
add_qubits	Add individual qubit wires.
copy	Function to copy a DAGDependency object.
depth	Return the circuit depth.
direct_predecessors	Direct predecessors id of a given node as sorted list.
direct_successors	Direct successors id of a given node as sorted list.
draw	Draws the DAGDependency graph.
get_all_edges	Enumeration of all edges.
get_edges	Edge enumeration between two nodes through method get_all_edge_data.
get_in_edges	Enumeration of all incoming edges for a given node.
get_node	param node_id label of considered node.
get_nodes	returns iterator over all the nodes.
get_out_edges	Enumeration of all outgoing edges for a given node.
predecessors	Predecessors id of a given node as sorted list.
size	Returns the number of gates in the circuit
successors	Successors id of a given node as sorted list.
to_networkx	Returns a copy of the DAGDependency in networkx format.
to_retworkx	Returns the DAGDependency in retworkx format.
topological_nodes	Yield nodes in topological order.

Attributes

calibrations

Return calibration dictionary.

The custom pulse definition of a given gate is of the form

{‘gate_name’: {(qubits, params): schedule}}

global_phase

Return the global phase of the circuit.