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)
Bases: BlueprintCircuit
The nlocal circuit class.
The structure of the nlocal circuit are alternating rotation and entanglement layers. In both layers, parameterized circuitblocks 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(opens in a new tab)  None) – The number of qubits of the circuit.
 rotation_blocks (QuantumCircuit list(opens in a new tab)[QuantumCircuit]  qiskit.circuit.Instruction list(opens in a new tab)[qiskit.circuit.Instruction]  None) – The blocks used in the rotation layers. If multiple are passed, these will be applied one after another (like new sublayers).
 entanglement_blocks (QuantumCircuit list(opens in a new tab)[QuantumCircuit]  qiskit.circuit.Instruction list(opens in a new tab)[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 sublayers, see
get_entangler_map()
.  entanglement (list(opens in a new tab)[int(opens in a new tab)]  list(opens in a new tab)[list(opens in a new tab)[int(opens in a new tab)]]  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(opens in a new tab)) – Specifies how often the rotation blocks and entanglement blocks are repeated.
 insert_barriers (bool(opens in a new tab)) – If
True
, barriers are inserted in between each layer. IfFalse
, no barriers are inserted.  parameter_prefix (str(opens in a new tab)) – The prefix used if default parameters are generated.
 overwrite_block_parameters (bool(opens in a new tab) list(opens in a new tab)[list(opens in a new tab)[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(opens in a new tab)) – Whether a final rotation layer is added to the circuit.
 skip_unentangled_qubits (bool(opens in a new tab)) – If
True
, the rotation gates act only on qubits that are entangled. IfFalse
, 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(opens in a new tab)  None) – The name of the circuit.
 flatten (bool(opens in a new tab)  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 toTrue
to avoid a large performance overhead for parameter binding.
Raises
 ValueError(opens in a new tab) – If
reps
parameter is less than or equal to 0.  TypeError(opens in a new tab) – If
reps
parameter is not an int value.
Attributes
ancillas
A list of AncillaQubit
s in the order that they were added. You should not mutate this.
calibrations
Return calibration dictionary.
The custom pulse definition of a given gate is of the form {'gate_name': {(qubits, params): schedule}}
clbits
A list of Clbit
s in the order that they were added. You should not mutate this.
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
The global phase of the current circuit scope in radians.
initial_state
Return the initial state that is added in front of the nlocal 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: 180
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 SwapGate
s inserted during routing.
metadata
Arbitrary userdefined metadata for the circuit.
Qiskit will not examine the content of this mapping, but it will pass it through the transpiler and reattach it to the output, so you can track your own metadata.
num_ancillas
Return the number of ancilla qubits.
num_captured_vars
The number of realtime classical variables in the circuit marked as captured from an enclosing scope.
This is the length of the iter_captured_vars()
iterable. If this is nonzero, num_input_vars
must be zero.
num_clbits
Return number of classical bits.
num_declared_vars
The number of realtime classical variables in the circuit that are declared by this circuit scope, excluding inputs or captures.
This is the length of the iter_declared_vars()
iterable.
num_input_vars
The number of realtime classical variables in the circuit marked as circuit inputs.
This is the length of the iter_input_vars()
iterable. If this is nonzero, num_captured_vars
must be zero.
num_layers
Return the number of layers in the nlocal 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.
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.
num_vars
The number of realtime classical variables in the circuit.
This is the length of the iter_vars()
iterable.
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(opens in a new tab) – 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 QuantumRegister
s in this circuit. You should not mutate this.
qubits
A list of Qubit
s in the order that they were added. You should not mutate this.
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.
name
Type: str
A humanreadable name for the circuit.
cregs
Type: list[ClassicalRegister]
A list of the ClassicalRegister
s in this circuit. You should not mutate this.
duration
Type: int  float  None
The total duration of the circuit, set by a scheduling transpiler pass. Its unit is specified by unit
.
unit
The unit that duration
is specified in.
Methods
add_layer
add_layer(other, entanglement=None, front=False)
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(opens in a new tab)[int(opens in a new tab)]  str(opens in a new tab) list(opens in a new tab)[list(opens in a new tab)[int(opens in a new tab)]]  None) – The entanglement or qubit indices.
 front (bool(opens in a new tab)) – If True,
other
is appended to the front, else to the back.
Returns
self, such that chained composes are possible.
Raises
TypeError(opens in a new tab) – If other is not compatible, i.e. is no Instruction and does not have a to_instruction method.
Return type
assign_parameters
assign_parameters(parameters, inplace=False, **kwargs)
Assign parameters to the nlocal 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(opens in a new tab) – 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)
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 

 None
 [[0, ..., n  1]]

 str
(e.g 'full'
)  the specified connectivity on n
qubits 
 List[int]
 [entanglement
] 
 List[List[int]]
 entanglement

 List[List[List[int]]]
 entanglement[i]

 List[List[List[List[int]]]]
 entanglement[i][j]

 List[str]
 the connectivity specified in entanglement[i]

 List[List[str]]
 the connectivity specified in entanglement[i][j]

 Callable[int, str]
 same as List[str]

 Callable[int, List[List[int]]]
 same as List[List[List[int]]]

Note that all indices are to be taken modulo the length of the array they act on, i.e. no outofbounds index error will be raised but we reiterate from the beginning of the list.
Parameters
 rep_num (int(opens in a new tab)) – The current repetition we are in.
 block_num (int(opens in a new tab)) – The block number within the entanglement layers.
 num_block_qubits (int(opens in a new tab)) – The number of qubits in the block.
Returns
The entangler map for the current block in the current repetition.
Raises
ValueError(opens in a new tab) – If the value of entanglement
could not be cast to a corresponding entangler map.
Return type
Sequence(opens in a new tab)[Sequence(opens in a new tab)[int(opens in a new tab)]]
get_unentangled_qubits
get_unentangled_qubits()
Get the indices of unentangled qubits in a set.
Returns
The unentangled qubits.
Return type
print_settings
print_settings()
Returns information about the setting.
Returns
The class name and the attributes/parameters of the instance as str
.
Return type