CouplingMap

CouplingMap.add_edge(src, dst)

Add directed edge to coupling graph.

src (int): source physical qubit dst (int): destination physical qubit

CouplingMap.add_physical_qubit(physical_qubit)

Add a physical qubit to the coupling graph as a node.

physical_qubit (int): An integer representing a physical qubit.

Raises

CouplingError – if trying to add duplicate qubit

CouplingMap.compute_distance_matrix()

Compute the full distance matrix on pairs of nodes.

The distance map self._dist_matrix is computed from the graph using all_pairs_shortest_path_length. This is normally handled internally by the distance_matrix attribute or the distance() method but can be called if you’re accessing the distance matrix outside of those or want to pre-generate it.

CouplingMap.distance(physical_qubit1, physical_qubit2)

Returns the undirected distance between physical_qubit1 and physical_qubit2.

Parameters

• physical_qubit1 (int) – A physical qubit
• physical_qubit2 (int) – Another physical qubit

Returns

The undirected distance

Return type

int

Raises

CouplingError – if the qubits do not exist in the CouplingMap

CouplingMap.draw()

Draws the coupling map.

This function calls the graphviz_draw() function from the rustworkx package to draw the CouplingMap object.

Returns

Drawn coupling map.

Return type

PIL.Image

classmethod CouplingMap.from_full(num_qubits, bidirectional=True)

Return a fully connected coupling map on n qubits.

Return type

CouplingMap

classmethod CouplingMap.from_grid(num_rows, num_columns, bidirectional=True)

Return a coupling map of qubits connected on a grid of num_rows x num_columns.

Return type

CouplingMap

classmethod CouplingMap.from_heavy_hex(distance, bidirectional=True)

Return a heavy hexagon graph coupling map.

A heavy hexagon graph is described in:

https://journals.aps.org/prx/abstract/10.1103/PhysRevX.10.011022

Parameters

• distance (int) – The code distance for the generated heavy hex graph. The value for distance can be any odd positive integer. The distance relates to the number of qubits by: $n = \frac{5d^2 - 2d - 1}{2}$ where $n$ is the number of qubits and $d$ is the distance parameter.
• bidirectional (bool) – Whether the edges in the output coupling graph are bidirectional or not. By default this is set to True

Returns

A heavy hex coupling graph

Return type

CouplingMap

classmethod CouplingMap.from_heavy_square(distance, bidirectional=True)

Return a heavy square graph coupling map.

A heavy square graph is described in:

https://journals.aps.org/prx/abstract/10.1103/PhysRevX.10.011022

Parameters

• distance (int) – The code distance for the generated heavy square graph. The value for distance can be any odd positive integer. The distance relates to the number of qubits by: $n = 3d^2 - 2d$ where $n$ is the number of qubits and $d$ is the distance parameter.
• bidirectional (bool) – Whether the edges in the output coupling graph are bidirectional or not. By default this is set to True

Returns

A heavy square coupling graph

Return type

CouplingMap

classmethod CouplingMap.from_hexagonal_lattice(rows, cols, bidirectional=True)

Return a hexagonal lattice graph coupling map.

Parameters

• rows (int) – The number of rows to generate the graph with.
• cols (int) – The number of columns to generate the graph with.
• bidirectional (bool) – Whether the edges in the output coupling graph are bidirectional or not. By default this is set to True

Returns

A hexagonal lattice coupling graph

Return type

CouplingMap

classmethod CouplingMap.from_line(num_qubits, bidirectional=True)

Return a coupling map of n qubits connected in a line.

Return type

CouplingMap

classmethod CouplingMap.from_ring(num_qubits, bidirectional=True)

Return a coupling map of n qubits connected to each of their neighbors in a ring.

Return type

CouplingMap

CouplingMap.get_edges()

Gets the list of edges in the coupling graph.

Returns

Each edge is a pair of physical qubits.

Return type

Tuple(int,int)

CouplingMap.is_connected()

Test if the graph is connected.

Return True if connected, False otherwise

CouplingMap.largest_connected_component()

Return a set of qubits in the largest connected component.

CouplingMap.make_symmetric()

Convert uni-directional edges into bi-directional.

CouplingMap.neighbors(physical_qubit)

Return the nearest neighbors of a physical qubit.

Directionality matters, i.e. a neighbor must be reachable by going one hop in the direction of an edge.

CouplingMap.reduce(mapping)

Returns a reduced coupling map that corresponds to the subgraph of qubits selected in the mapping.

Parameters

mapping (list) – A mapping of reduced qubits to device qubits.

Returns

A reduced coupling_map for the selected qubits.

Return type

CouplingMap

Raises

CouplingError – Reduced coupling map must be connected.

CouplingMap.shortest_undirected_path(physical_qubit1, physical_qubit2)

Returns the shortest undirected path between physical_qubit1 and physical_qubit2.

Parameters

• physical_qubit1 (int) – A physical qubit
• physical_qubit2 (int) – Another physical qubit

Returns

The shortest undirected path

Return type

List

Raises

CouplingError – When there is no path between physical_qubit1, physical_qubit2.

CouplingMap.size()

Return the number of physical qubits in this graph.

CouplingMap.subgraph(nodelist)

Return a CouplingMap object for a subgraph of self.

nodelist (list): list of integer node labels

Return the distance matrix for the coupling map.

Test if the graph is symmetric.

Return True if symmetric, False otherwise

Returns a sorted list of physical_qubits