260 lines
12 KiB
Plaintext
260 lines
12 KiB
Plaintext
---
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title: Layout
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description: API reference for qiskit.transpiler.Layout
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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.Layout
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---
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# qiskit.transpiler.Layout
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<Class id="qiskit.transpiler.Layout" isDedicatedPage={true} github="https://github.com/qiskit/qiskit/tree/stable/0.17/qiskit/transpiler/layout.py" signature="Layout(input_dict=None)" modifiers="class">
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Two-ways dict to represent a Layout.
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construct a Layout from a bijective dictionary, mapping virtual qubits to physical qubits
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### \_\_init\_\_
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<Function id="qiskit.transpiler.Layout.__init__" signature="__init__(input_dict=None)">
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construct a Layout from a bijective dictionary, mapping virtual qubits to physical qubits
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</Function>
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## Methods
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| -------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------- |
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| [`__init__`](#qiskit.transpiler.Layout.__init__ "qiskit.transpiler.Layout.__init__")(\[input\_dict]) | construct a Layout from a bijective dictionary, mapping virtual qubits to physical qubits |
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| [`add`](#qiskit.transpiler.Layout.add "qiskit.transpiler.Layout.add")(virtual\_bit\[, physical\_bit]) | Adds a map element between bit and physical\_bit. |
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| [`add_register`](#qiskit.transpiler.Layout.add_register "qiskit.transpiler.Layout.add_register")(reg) | Adds at the end physical\_qubits that map each bit in reg. |
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| [`combine_into_edge_map`](#qiskit.transpiler.Layout.combine_into_edge_map "qiskit.transpiler.Layout.combine_into_edge_map")(another\_layout) | Combines self and another\_layout into an “edge map”. |
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| [`copy`](#qiskit.transpiler.Layout.copy "qiskit.transpiler.Layout.copy")() | Returns a copy of a Layout instance. |
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| [`from_dict`](#qiskit.transpiler.Layout.from_dict "qiskit.transpiler.Layout.from_dict")(input\_dict) | Populates a Layout from a dictionary. |
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| [`from_intlist`](#qiskit.transpiler.Layout.from_intlist "qiskit.transpiler.Layout.from_intlist")(int\_list, \*qregs) | Converts a list of integers to a Layout mapping virtual qubits (index of the list) to physical qubits (the list values). |
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| [`from_qubit_list`](#qiskit.transpiler.Layout.from_qubit_list "qiskit.transpiler.Layout.from_qubit_list")(qubit\_list, \*qregs) | Populates a Layout from a list containing virtual qubits, Qubit or None. |
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| [`generate_trivial_layout`](#qiskit.transpiler.Layout.generate_trivial_layout "qiskit.transpiler.Layout.generate_trivial_layout")(\*regs) | Creates a trivial (“one-to-one”) Layout with the registers and qubits in regs. |
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| [`get_physical_bits`](#qiskit.transpiler.Layout.get_physical_bits "qiskit.transpiler.Layout.get_physical_bits")() | Returns the dictionary where the keys are physical (qu)bits and the values are virtual (qu)bits. |
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| [`get_registers`](#qiskit.transpiler.Layout.get_registers "qiskit.transpiler.Layout.get_registers")() | Returns the registers in the layout \[QuantumRegister(2, ‘qr0’), QuantumRegister(3, ‘qr1’)] :returns: A set of Registers in the layout :rtype: Set |
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| [`get_virtual_bits`](#qiskit.transpiler.Layout.get_virtual_bits "qiskit.transpiler.Layout.get_virtual_bits")() | Returns the dictionary where the keys are virtual (qu)bits and the values are physical (qu)bits. |
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| [`order_based_on_type`](#qiskit.transpiler.Layout.order_based_on_type "qiskit.transpiler.Layout.order_based_on_type")(value1, value2) | decides which one is physical/virtual based on the type. |
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| [`reorder_bits`](#qiskit.transpiler.Layout.reorder_bits "qiskit.transpiler.Layout.reorder_bits")(bits) | Given an ordered list of bits, reorder them according to this layout. |
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| [`swap`](#qiskit.transpiler.Layout.swap "qiskit.transpiler.Layout.swap")(left, right) | Swaps the map between left and right. |
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### add
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<Function id="qiskit.transpiler.Layout.add" signature="add(virtual_bit, physical_bit=None)">
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Adds a map element between bit and physical\_bit. If physical\_bit is not defined, bit will be mapped to a new physical bit (extending the length of the layout by one.)
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**Parameters**
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* **virtual\_bit** (*tuple*) – A (qu)bit. For example, (QuantumRegister(3, ‘qr’), 2).
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* **physical\_bit** (*int*) – A physical bit. For example, 3.
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</Function>
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### add\_register
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<Function id="qiskit.transpiler.Layout.add_register" signature="add_register(reg)">
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Adds at the end physical\_qubits that map each bit in reg.
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**Parameters**
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**reg** (*Register*) – A (qu)bit Register. For example, QuantumRegister(3, ‘qr’).
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</Function>
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### combine\_into\_edge\_map
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<Function id="qiskit.transpiler.Layout.combine_into_edge_map" signature="combine_into_edge_map(another_layout)">
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Combines self and another\_layout into an “edge map”.
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For example:
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```python
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self another_layout resulting edge map
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qr_1 -> 0 0 <- q_2 qr_1 -> q_2
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qr_2 -> 2 2 <- q_1 qr_2 -> q_1
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qr_3 -> 3 3 <- q_0 qr_3 -> q_0
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```
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The edge map is used to compose dags via, for example, compose.
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**Parameters**
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**another\_layout** ([*Layout*](#qiskit.transpiler.Layout "qiskit.transpiler.Layout")) – The other layout to combine.
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**Returns**
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A “edge map”.
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**Return type**
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dict
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**Raises**
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**LayoutError** – another\_layout can be bigger than self, but not smaller. Otherwise, raises.
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</Function>
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### copy
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<Function id="qiskit.transpiler.Layout.copy" signature="copy()">
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Returns a copy of a Layout instance.
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</Function>
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### from\_dict
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<Function id="qiskit.transpiler.Layout.from_dict" signature="from_dict(input_dict)">
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Populates a Layout from a dictionary.
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The dictionary must be a bijective mapping between virtual qubits (tuple) and physical qubits (int).
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**Parameters**
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**input\_dict** (*dict*) –
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e.g.:
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```python
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{(QuantumRegister(3, 'qr'), 0): 0,
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(QuantumRegister(3, 'qr'), 1): 1,
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(QuantumRegister(3, 'qr'), 2): 2}
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Can be written more concisely as follows:
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* virtual to physical::
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{qr[0]: 0,
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qr[1]: 1,
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qr[2]: 2}
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* physical to virtual::
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{0: qr[0],
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1: qr[1],
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2: qr[2]}
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```
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</Function>
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### from\_intlist
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<Function id="qiskit.transpiler.Layout.from_intlist" signature="from_intlist(int_list, *qregs)" modifiers="static">
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Converts a list of integers to a Layout mapping virtual qubits (index of the list) to physical qubits (the list values).
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**Parameters**
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* **int\_list** (*list*) – A list of integers.
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* **\*qregs** (*QuantumRegisters*) – The quantum registers to apply the layout to.
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**Returns**
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The corresponding Layout object.
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**Return type**
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[Layout](#qiskit.transpiler.Layout "qiskit.transpiler.Layout")
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**Raises**
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**LayoutError** – Invalid input layout.
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</Function>
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### from\_qubit\_list
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<Function id="qiskit.transpiler.Layout.from_qubit_list" signature="from_qubit_list(qubit_list, *qregs)" modifiers="static">
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Populates a Layout from a list containing virtual qubits, Qubit or None.
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**Parameters**
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* **qubit\_list** (*list*) – e.g.: \[qr\[0], None, qr\[2], qr\[3]]
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* **\*qregs** (*QuantumRegisters*) – The quantum registers to apply the layout to.
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**Returns**
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the corresponding Layout object
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**Return type**
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[Layout](#qiskit.transpiler.Layout "qiskit.transpiler.Layout")
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**Raises**
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**LayoutError** – If the elements are not Qubit or None
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</Function>
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### generate\_trivial\_layout
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<Function id="qiskit.transpiler.Layout.generate_trivial_layout" signature="generate_trivial_layout(*regs)" modifiers="static">
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Creates a trivial (“one-to-one”) Layout with the registers and qubits in regs.
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**Parameters**
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**\*regs** (*Registers, Qubits*) – registers and qubits to include in the layout.
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**Returns**
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A layout with all the regs in the given order.
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**Return type**
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[Layout](#qiskit.transpiler.Layout "qiskit.transpiler.Layout")
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</Function>
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### get\_physical\_bits
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<Function id="qiskit.transpiler.Layout.get_physical_bits" signature="get_physical_bits()">
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Returns the dictionary where the keys are physical (qu)bits and the values are virtual (qu)bits.
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</Function>
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### get\_registers
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<Function id="qiskit.transpiler.Layout.get_registers" signature="get_registers()">
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Returns the registers in the layout \[QuantumRegister(2, ‘qr0’), QuantumRegister(3, ‘qr1’)] :returns: A set of Registers in the layout :rtype: Set
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</Function>
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### get\_virtual\_bits
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<Function id="qiskit.transpiler.Layout.get_virtual_bits" signature="get_virtual_bits()">
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Returns the dictionary where the keys are virtual (qu)bits and the values are physical (qu)bits.
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</Function>
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### order\_based\_on\_type
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<Function id="qiskit.transpiler.Layout.order_based_on_type" signature="order_based_on_type(value1, value2)" modifiers="static">
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decides which one is physical/virtual based on the type. Returns (virtual, physical)
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</Function>
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### reorder\_bits
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<Function id="qiskit.transpiler.Layout.reorder_bits" signature="reorder_bits(bits)">
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Given an ordered list of bits, reorder them according to this layout.
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The list of bits must exactly match the virtual bits in this layout.
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**Parameters**
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**bits** (*list\[Bit]*) – the bits to reorder.
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**Returns**
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ordered bits.
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**Return type**
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List
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</Function>
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### swap
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<Function id="qiskit.transpiler.Layout.swap" signature="swap(left, right)">
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Swaps the map between left and right.
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**Parameters**
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* **left** (*tuple or int*) – Item to swap with right.
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* **right** (*tuple or int*) – Item to swap with left.
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**Raises**
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**LayoutError** – If left and right have not the same type.
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</Function>
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</Class>
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