332 lines
11 KiB
Plaintext
332 lines
11 KiB
Plaintext
---
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title: CouplingMap
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description: API reference for qiskit.transpiler.CouplingMap
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in_page_toc_min_heading_level: 1
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python_api_type: class
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python_api_name: qiskit.transpiler.CouplingMap
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---
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# CouplingMap
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<Class id="qiskit.transpiler.CouplingMap" isDedicatedPage={true} github="https://github.com/qiskit/qiskit/tree/stable/0.22/qiskit/transpiler/coupling.py" signature="CouplingMap(couplinglist=None, description=None)" modifiers="class">
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Bases: `object`
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Directed graph specifying fixed coupling.
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Nodes correspond to physical qubits (integers) and directed edges correspond to permitted CNOT gates, with source and destination corresponding to control and target qubits, respectively.
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Create coupling graph. By default, the generated coupling has no nodes.
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**Parameters**
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* **couplinglist** (*list or None*) – An initial coupling graph, specified as an adjacency list containing couplings, e.g. \[\[0,1], \[0,2], \[1,2]]. It is required that nodes are contiguously indexed starting at 0. Missed nodes will be added as isolated nodes in the coupling map.
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* **description** (*str*) – A string to describe the coupling map.
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## Methods
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### add\_edge
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<Function id="qiskit.transpiler.CouplingMap.add_edge" signature="CouplingMap.add_edge(src, dst)">
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Add directed edge to coupling graph.
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src (int): source physical qubit dst (int): destination physical qubit
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</Function>
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### add\_physical\_qubit
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<Function id="qiskit.transpiler.CouplingMap.add_physical_qubit" signature="CouplingMap.add_physical_qubit(physical_qubit)">
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Add a physical qubit to the coupling graph as a node.
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physical\_qubit (int): An integer representing a physical qubit.
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**Raises**
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**CouplingError** – if trying to add duplicate qubit
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</Function>
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### compute\_distance\_matrix
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<Function id="qiskit.transpiler.CouplingMap.compute_distance_matrix" signature="CouplingMap.compute_distance_matrix()">
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Compute the full distance matrix on pairs of nodes.
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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`](qiskit.transpiler.CouplingMap#distance_matrix "qiskit.transpiler.CouplingMap.distance_matrix") attribute or the [`distance()`](qiskit.transpiler.CouplingMap#distance "qiskit.transpiler.CouplingMap.distance") method but can be called if you’re accessing the distance matrix outside of those or want to pre-generate it.
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</Function>
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### distance
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<Function id="qiskit.transpiler.CouplingMap.distance" signature="CouplingMap.distance(physical_qubit1, physical_qubit2)">
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Returns the undirected distance between physical\_qubit1 and physical\_qubit2.
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**Parameters**
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* **physical\_qubit1** (*int*) – A physical qubit
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* **physical\_qubit2** (*int*) – Another physical qubit
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**Returns**
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The undirected distance
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**Return type**
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int
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**Raises**
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**CouplingError** – if the qubits do not exist in the CouplingMap
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</Function>
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### draw
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<Function id="qiskit.transpiler.CouplingMap.draw" signature="CouplingMap.draw()">
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Draws the coupling map.
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This function calls the `graphviz_draw()` function from the `retworkx` package to draw the [`CouplingMap`](qiskit.transpiler.CouplingMap "qiskit.transpiler.CouplingMap") object.
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**Returns**
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Drawn coupling map.
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**Return type**
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PIL.Image
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</Function>
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### from\_full
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<Function id="qiskit.transpiler.CouplingMap.from_full" signature="CouplingMap.from_full(num_qubits, bidirectional=True)" modifiers="classmethod">
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Return a fully connected coupling map on n qubits.
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**Return type**
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[`CouplingMap`](qiskit.transpiler.CouplingMap "qiskit.transpiler.coupling.CouplingMap")
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</Function>
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### from\_grid
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<Function id="qiskit.transpiler.CouplingMap.from_grid" signature="CouplingMap.from_grid(num_rows, num_columns, bidirectional=True)" modifiers="classmethod">
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Return a coupling map of qubits connected on a grid of num\_rows x num\_columns.
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**Return type**
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[`CouplingMap`](qiskit.transpiler.CouplingMap "qiskit.transpiler.coupling.CouplingMap")
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</Function>
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### from\_heavy\_hex
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<Function id="qiskit.transpiler.CouplingMap.from_heavy_hex" signature="CouplingMap.from_heavy_hex(distance, bidirectional=True)" modifiers="classmethod">
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Return a heavy hexagon graph coupling map.
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A heavy hexagon graph is described in:
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[https://journals.aps.org/prx/abstract/10.1103/PhysRevX.10.011022](https://journals.aps.org/prx/abstract/10.1103/PhysRevX.10.011022)
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**Parameters**
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* **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.
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* **bidirectional** (*bool*) – Whether the edges in the output coupling graph are bidirectional or not. By default this is set to `True`
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**Returns**
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A heavy hex coupling graph
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**Return type**
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[CouplingMap](qiskit.transpiler.CouplingMap "qiskit.transpiler.CouplingMap")
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</Function>
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### from\_heavy\_square
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<Function id="qiskit.transpiler.CouplingMap.from_heavy_square" signature="CouplingMap.from_heavy_square(distance, bidirectional=True)" modifiers="classmethod">
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Return a heavy square graph coupling map.
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A heavy square graph is described in:
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[https://journals.aps.org/prx/abstract/10.1103/PhysRevX.10.011022](https://journals.aps.org/prx/abstract/10.1103/PhysRevX.10.011022)
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**Parameters**
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* **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.
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* **bidirectional** (*bool*) – Whether the edges in the output coupling graph are bidirectional or not. By default this is set to `True`
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**Returns**
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A heavy square coupling graph
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**Return type**
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[CouplingMap](qiskit.transpiler.CouplingMap "qiskit.transpiler.CouplingMap")
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</Function>
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### from\_hexagonal\_lattice
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<Function id="qiskit.transpiler.CouplingMap.from_hexagonal_lattice" signature="CouplingMap.from_hexagonal_lattice(rows, cols, bidirectional=True)" modifiers="classmethod">
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Return a hexagonal lattice graph coupling map.
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**Parameters**
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* **rows** (*int*) – The number of rows to generate the graph with.
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* **cols** (*int*) – The number of columns to generate the graph with.
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* **bidirectional** (*bool*) – Whether the edges in the output coupling graph are bidirectional or not. By default this is set to `True`
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**Returns**
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A hexagonal lattice coupling graph
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**Return type**
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[CouplingMap](qiskit.transpiler.CouplingMap "qiskit.transpiler.CouplingMap")
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</Function>
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### from\_line
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<Function id="qiskit.transpiler.CouplingMap.from_line" signature="CouplingMap.from_line(num_qubits, bidirectional=True)" modifiers="classmethod">
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Return a coupling map of n qubits connected in a line.
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**Return type**
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[`CouplingMap`](qiskit.transpiler.CouplingMap "qiskit.transpiler.coupling.CouplingMap")
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</Function>
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### from\_ring
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<Function id="qiskit.transpiler.CouplingMap.from_ring" signature="CouplingMap.from_ring(num_qubits, bidirectional=True)" modifiers="classmethod">
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Return a coupling map of n qubits connected to each of their neighbors in a ring.
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**Return type**
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[`CouplingMap`](qiskit.transpiler.CouplingMap "qiskit.transpiler.coupling.CouplingMap")
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</Function>
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### get\_edges
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<Function id="qiskit.transpiler.CouplingMap.get_edges" signature="CouplingMap.get_edges()">
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Gets the list of edges in the coupling graph.
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**Returns**
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Each edge is a pair of physical qubits.
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**Return type**
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Tuple(int,int)
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</Function>
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### is\_connected
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<Function id="qiskit.transpiler.CouplingMap.is_connected" signature="CouplingMap.is_connected()">
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Test if the graph is connected.
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Return True if connected, False otherwise
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</Function>
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### largest\_connected\_component
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<Function id="qiskit.transpiler.CouplingMap.largest_connected_component" signature="CouplingMap.largest_connected_component()">
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Return a set of qubits in the largest connected component.
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</Function>
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### make\_symmetric
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<Function id="qiskit.transpiler.CouplingMap.make_symmetric" signature="CouplingMap.make_symmetric()">
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Convert uni-directional edges into bi-directional.
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</Function>
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### neighbors
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<Function id="qiskit.transpiler.CouplingMap.neighbors" signature="CouplingMap.neighbors(physical_qubit)">
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Return the nearest neighbors of a physical qubit.
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Directionality matters, i.e. a neighbor must be reachable by going one hop in the direction of an edge.
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</Function>
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### reduce
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<Function id="qiskit.transpiler.CouplingMap.reduce" signature="CouplingMap.reduce(mapping)">
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Returns a reduced coupling map that corresponds to the subgraph of qubits selected in the mapping.
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**Parameters**
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**mapping** (*list*) – A mapping of reduced qubits to device qubits.
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**Returns**
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A reduced coupling\_map for the selected qubits.
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**Return type**
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[CouplingMap](qiskit.transpiler.CouplingMap "qiskit.transpiler.CouplingMap")
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**Raises**
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**CouplingError** – Reduced coupling map must be connected.
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</Function>
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### shortest\_undirected\_path
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<Function id="qiskit.transpiler.CouplingMap.shortest_undirected_path" signature="CouplingMap.shortest_undirected_path(physical_qubit1, physical_qubit2)">
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Returns the shortest undirected path between physical\_qubit1 and physical\_qubit2.
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**Parameters**
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* **physical\_qubit1** (*int*) – A physical qubit
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* **physical\_qubit2** (*int*) – Another physical qubit
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**Returns**
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The shortest undirected path
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**Return type**
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List
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**Raises**
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**CouplingError** – When there is no path between physical\_qubit1, physical\_qubit2.
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</Function>
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### size
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<Function id="qiskit.transpiler.CouplingMap.size" signature="CouplingMap.size()">
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Return the number of physical qubits in this graph.
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</Function>
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### subgraph
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<Function id="qiskit.transpiler.CouplingMap.subgraph" signature="CouplingMap.subgraph(nodelist)">
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Return a CouplingMap object for a subgraph of self.
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nodelist (list): list of integer node labels
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</Function>
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## Attributes
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### description
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<Attribute id="qiskit.transpiler.CouplingMap.description" />
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### graph
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<Attribute id="qiskit.transpiler.CouplingMap.graph" />
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### distance\_matrix
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<Attribute id="qiskit.transpiler.CouplingMap.distance_matrix">
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Return the distance matrix for the coupling map.
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</Attribute>
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### is\_symmetric
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<Attribute id="qiskit.transpiler.CouplingMap.is_symmetric">
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Test if the graph is symmetric.
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Return True if symmetric, False otherwise
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</Attribute>
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### physical\_qubits
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<Attribute id="qiskit.transpiler.CouplingMap.physical_qubits">
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Returns a sorted list of physical\_qubits
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</Attribute>
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</Class>
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