NLocal

class qiskit.circuit.library.NLocal(num_qubits=None, rotation_blocks=None, entanglement_blocks=None, entanglement=None, reps=1, insert_barriers=False, parameter_prefix='θ', overwrite_block_parameters=True, skip_final_rotation_layer=False, skip_unentangled_qubits=False, initial_state=None, name='nlocal', flatten=None)

GitHub

Bases: BlueprintCircuit

The n-local circuit class.

The structure of the n-local circuit are alternating rotation and entanglement layers. In both layers, parameterized circuit-blocks act on the circuit in a defined way. In the rotation layer, the blocks are applied stacked on top of each other, while in the entanglement layer according to the entanglement strategy. The circuit blocks can have arbitrary sizes (smaller equal to the number of qubits in the circuit). Each layer is repeated reps times, and by default a final rotation layer is appended.

For instance, a rotation block on 2 qubits and an entanglement block on 4 qubits using 'linear' entanglement yields the following circuit.

┌──────┐ ░ ┌──────┐                      ░ ┌──────┐
┤0     ├─░─┤0     ├──────────────── ... ─░─┤0     ├
│  Rot │ ░ │      │┌──────┐              ░ │  Rot │
┤1     ├─░─┤1     ├┤0     ├──────── ... ─░─┤1     ├
├──────┤ ░ │  Ent ││      │┌──────┐      ░ ├──────┤
┤0     ├─░─┤2     ├┤1     ├┤0     ├ ... ─░─┤0     ├
│  Rot │ ░ │      ││  Ent ││      │      ░ │  Rot │
┤1     ├─░─┤3     ├┤2     ├┤1     ├ ... ─░─┤1     ├
├──────┤ ░ └──────┘│      ││  Ent │      ░ ├──────┤
┤0     ├─░─────────┤3     ├┤2     ├ ... ─░─┤0     ├
│  Rot │ ░         └──────┘│      │      ░ │  Rot │
┤1     ├─░─────────────────┤3     ├ ... ─░─┤1     ├
└──────┘ ░                 └──────┘      ░ └──────┘
 
|                                 |
+---------------------------------+
       repeated reps times

If specified, barriers can be inserted in between every block. If an initial state object is provided, it is added in front of the NLocal.

Parameters

num_qubits (int | None) – The number of qubits of the circuit.
rotation_blocks (QuantumCircuit |list[QuantumCircuit] | qiskit.circuit.Instruction |list[qiskit.circuit.Instruction] | None) – The blocks used in the rotation layers. If multiple are passed, these will be applied one after another (like new sub-layers).
entanglement_blocks (QuantumCircuit |list[QuantumCircuit] | qiskit.circuit.Instruction |list[qiskit.circuit.Instruction] | None) – The blocks used in the entanglement layers. If multiple are passed, these will be applied one after another. To use different entanglements for the sub-layers, see get_entangler_map().
entanglement (list[int] | list[list[int]] | None) – The indices specifying on which qubits the input blocks act. If None, the entanglement blocks are applied at the top of the circuit.
reps (int) – Specifies how often the rotation blocks and entanglement blocks are repeated.
insert_barriers (bool) – If True, barriers are inserted in between each layer. If False, no barriers are inserted.
parameter_prefix (str) – The prefix used if default parameters are generated.
overwrite_block_parameters (bool |list[list[Parameter]]) – If the parameters in the added blocks should be overwritten. If False, the parameters in the blocks are not changed.
skip_final_rotation_layer (bool) – Whether a final rotation layer is added to the circuit.
skip_unentangled_qubits (bool) – If True, the rotation gates act only on qubits that are entangled. If False, the rotation gates act on all qubits.
initial_state (QuantumCircuit | None) – A QuantumCircuit object which can be used to describe an initial state prepended to the NLocal circuit.
name (str | None) – The name of the circuit.
flatten (bool | None) – Set this to True to output a flat circuit instead of nesting it inside multiple layers of gate objects. By default currently the contents of the output circuit will be wrapped in nested objects for cleaner visualization. However, if you’re using this circuit for anything besides visualization its strongly recommended to set this flag to True to avoid a large performance overhead for parameter binding.

Raises

ValueError – If reps parameter is less than or equal to 0.
TypeError – If reps parameter is not an int value.

Attributes

ancillas

Returns a list of ancilla bits in the order that the registers were added.

calibrations

Return calibration dictionary.

The custom pulse definition of a given gate is of the form {'gate_name': {(qubits, params): schedule}}

clbits

Returns a list of classical bits in the order that the registers were added.

data

entanglement

Get the entanglement strategy.

Returns

The entanglement strategy, see get_entangler_map() for more detail on how the format is interpreted.

entanglement_blocks

The blocks in the entanglement layers.

Returns

The blocks in the entanglement layers.

flatten

Returns whether the circuit is wrapped in nested gates/instructions or flattened.

global_phase

Return the global phase of the current circuit scope in radians.

initial_state

Return the initial state that is added in front of the n-local circuit.

Returns

The initial state.

insert_barriers

If barriers are inserted in between the layers or not.

Returns

True, if barriers are inserted in between the layers, False if not.

instances

Default value: 198

layout

Return any associated layout information about the circuit

This attribute contains an optional TranspileLayout object. This is typically set on the output from transpile() or PassManager.run() to retain information about the permutations caused on the input circuit by transpilation.

There are two types of permutations caused by the transpile() function, an initial layout which permutes the qubits based on the selected physical qubits on the Target, and a final layout which is an output permutation caused by SwapGates inserted during routing.

metadata

The user provided metadata associated with the circuit.

The metadata for the circuit is a user provided dict of metadata for the circuit. It will not be used to influence the execution or operation of the circuit, but it is expected to be passed between all transforms of the circuit (ie transpilation) and that providers will associate any circuit metadata with the results it returns from execution of that circuit.

num_ancillas

Return the number of ancilla qubits.

num_clbits

Return number of classical bits.

num_layers

Return the number of layers in the n-local circuit.

Returns

The number of layers in the circuit.

num_parameters

num_parameters_settable

The number of total parameters that can be set to distinct values.

This does not change when the parameters are bound or exchanged for same parameters, and therefore is different from num_parameters which counts the number of unique Parameter objects currently in the circuit.

Returns

The number of parameters originally available in the circuit.

Note

This quantity does not require the circuit to be built yet.

num_qubits

Returns the number of qubits in this circuit.

Returns

The number of qubits.

op_start_times

Return a list of operation start times.

This attribute is enabled once one of scheduling analysis passes runs on the quantum circuit.

Returns

List of integers representing instruction start times. The index corresponds to the index of instruction in QuantumCircuit.data.

Raises

AttributeError – When circuit is not scheduled.

ordered_parameters

The parameters used in the underlying circuit.

This includes float values and duplicates.

Examples

>>> # prepare circuit ...
>>> print(nlocal)
     ┌───────┐┌──────────┐┌──────────┐┌──────────┐
q_0: ┤ Ry(1) ├┤ Ry(θ[1]) ├┤ Ry(θ[1]) ├┤ Ry(θ[3]) ├
     └───────┘└──────────┘└──────────┘└──────────┘
>>> nlocal.parameters
{Parameter(θ[1]), Parameter(θ[3])}
>>> nlocal.ordered_parameters
[1, Parameter(θ[1]), Parameter(θ[1]), Parameter(θ[3])]

Returns

The parameters objects used in the circuit.

parameter_bounds

The parameter bounds for the unbound parameters in the circuit.

Returns

A list of pairs indicating the bounds, as (lower, upper). None indicates an unbounded parameter in the corresponding direction. If None is returned, problem is fully unbounded.

parameters

preferred_init_points

The initial points for the parameters. Can be stored as initial guess in optimization.

Returns

The initial values for the parameters, or None, if none have been set.

prefix

Default value: 'circuit'

qregs

Type: list[QuantumRegister]

A list of the quantum registers associated with the circuit.

qubits

Returns a list of quantum bits in the order that the registers were added.

reps

The number of times rotation and entanglement block are repeated.

Returns

The number of repetitions.

rotation_blocks

The blocks in the rotation layers.

Returns

The blocks in the rotation layers.

Methods

add_layer

add_layer(other, entanglement=None, front=False)

GitHub

Append another layer to the NLocal.

Parameters

other (QuantumCircuit |qiskit.circuit.Instruction) – The layer to compose, can be another NLocal, an Instruction or Gate, or a QuantumCircuit.
entanglement (list[int] | str |list[list[int]] | None) – The entanglement or qubit indices.
front (bool) – If True, other is appended to the front, else to the back.

Returns

self, such that chained composes are possible.

Raises

TypeError – If other is not compatible, i.e. is no Instruction and does not have a to_instruction method.

Return type

NLocal

assign_parameters

assign_parameters(parameters, inplace=False, **kwargs)

GitHub

Assign parameters to the n-local circuit.

This method also supports passing a list instead of a dictionary. If a list is passed, the list must have the same length as the number of unbound parameters in the circuit. The parameters are assigned in the order of the parameters in ordered_parameters().

Returns

A copy of the NLocal circuit with the specified parameters.

Raises

AttributeError – If the parameters are given as list and do not match the number of parameters.

Return type

QuantumCircuit | None

get_entangler_map

get_entangler_map(rep_num, block_num, num_block_qubits)

GitHub

Get the entangler map for in the repetition rep_num and the block block_num.

The entangler map for the current block is derived from the value of self.entanglement. Below the different cases are listed, where i and j denote the repetition number and the block number, respectively, and n the number of qubits in the block.

entanglement type	entangler map

Note that all indices are to be taken modulo the length of the array they act on, i.e. no out-of-bounds index error will be raised but we re-iterate from the beginning of the list.

Parameters