WhileLoopOp
class qiskit.circuit.WhileLoopOp(condition, body, label=None)
Bases: ControlFlowOp
A circuit operation which repeatedly executes a subcircuit (body) until a condition (condition) evaluates as False.
The classical bits used in condition must be a subset of those attached to body.
Parameters
- condition (tuple[ClassicalRegister, int] | tuple[Clbit, int] | expr.Expr) – A condition to be checked prior to executing
body. Can be specified as either a tuple of aClassicalRegisterto be tested for equality with a givenint, or as a tuple of aClbitto be compared to either aboolor anint. - body (QuantumCircuit) – The loop body to be repeatedly executed.
- label (str | None) – An optional label for identifying the instruction.
Attributes
base_class
Get the base class of this instruction. This is guaranteed to be in the inheritance tree of self.
The “base class” of an instruction is the lowest class in its inheritance tree that the object should be considered entirely compatible with for _all_ circuit applications. This typically means that the subclass is defined purely to offer some sort of programmer convenience over the base class, and the base class is the “true” class for a behavioral perspective. In particular, you should not override base_class if you are defining a custom version of an instruction that will be implemented differently by hardware, such as an alternative measurement strategy, or a version of a parametrized gate with a particular set of parameters for the purposes of distinguishing it in a Target from the full parametrized gate.
This is often exactly equivalent to type(obj), except in the case of singleton instances of standard-library instructions. These singleton instances are special subclasses of their base class, and this property will return that base. For example:
>>> isinstance(XGate(), XGate)
True
>>> type(XGate()) is XGate
False
>>> XGate().base_class is XGate
TrueIn general, you should not rely on the precise class of an instruction; within a given circuit, it is expected that Instruction.name should be a more suitable discriminator in most situations.
blocks
condition
The classical condition on the instruction.
condition_bits
Get Clbits in condition.
decompositions
Get the decompositions of the instruction from the SessionEquivalenceLibrary.
definition
Return definition in terms of other basic gates.
duration
Get the duration.
label
Return instruction label
mutable
Is this instance is a mutable unique instance or not.
If this attribute is False the gate instance is a shared singleton and is not mutable.
name
Return the name.
num_clbits
Return the number of clbits.
num_qubits
Return the number of qubits.
params
unit
Get the time unit of duration.
Methods
add_decomposition
add_decomposition(decomposition)
Add a decomposition of the instruction to the SessionEquivalenceLibrary.
assemble
assemble()
Assemble a QasmQobjInstruction
The method qiskit.circuit.instruction.Instruction.assemble() is deprecated as of qiskit 1.2. It will be removed in the 2.0 release. The Qobj class and related functionality are part of the deprecated BackendV1 workflow, and no longer necessary for BackendV2. If a user workflow requires Qobj it likely relies on deprecated functionality and should be updated to use BackendV2.
broadcast_arguments
broadcast_arguments(qargs, cargs)
Validation of the arguments.
Parameters
- qargs (List) – List of quantum bit arguments.
- cargs (List) – List of classical bit arguments.
Yields
Tuple(List, List) – A tuple with single arguments.
Raises
CircuitError – If the input is not valid. For example, the number of arguments does not match the gate expectation.
c_if
c_if(classical, val)
Set a classical equality condition on this instruction between the register or cbit classical and value val.
This is a setter method, not an additive one. Calling this multiple times will silently override any previously set condition; it does not stack.
copy
copy(name=None)
Copy of the instruction.
Parameters
name (str) – name to be given to the copied circuit, if None then the name stays the same.
Returns
a copy of the current instruction, with the name updated if it was provided
Return type
inverse
inverse(annotated=False)
Invert this instruction.
If annotated is False, the inverse instruction is implemented as a fresh instruction with the recursively inverted definition.
If annotated is True, the inverse instruction is implemented as AnnotatedOperation, and corresponds to the given instruction annotated with the “inverse modifier”.
Special instructions inheriting from Instruction can implement their own inverse (e.g. T and Tdg, Barrier, etc.) In particular, they can choose how to handle the argument annotated which may include ignoring it and always returning a concrete gate class if the inverse is defined as a standard gate.
Parameters
annotated (bool) – if set to True the output inverse gate will be returned as AnnotatedOperation.
Returns
The inverse operation.
Raises
CircuitError – if the instruction is not composite and an inverse has not been implemented for it.
is_parameterized
iter_captured_vars
iter_captured_vars()
Get an iterator over the unique captured variables in all blocks of this construct.
Return type
repeat
repeat(n)
Creates an instruction with self repeated :math`n` times.
If this operation has a conditional, the output instruction will have the same conditional and the inner repeated operations will be unconditional; instructions within a compound definition cannot be conditioned on registers within Qiskit’s data model. This means that it is not valid to apply a repeated instruction to a clbit that it both writes to and reads from in its condition.
Parameters
n (int) – Number of times to repeat the instruction
Returns
Containing the definition.
Return type
Raises
CircuitError – If n < 1.
replace_blocks
replace_blocks(blocks)
Return a new version of this control-flow operations with the blocks mapped to the given new ones.
Typically this is used in a workflow such as:
existing_op = ...
def map_block(block: QuantumCircuit) -> QuantumCircuit:
new_block = block.copy_empty_like()
# ... do something to `new_block` ...
return new_block
new_op = existing_op.replace_blocks(
map_block(block) for block in existing_op.blocks
)It is the caller’s responsibility to ensure that the mapped blocks are defined over a unified set of circuit resources, much like constructing a ControlFlowOp using its default constructor.
Parameters
blocks – the new subcircuit blocks to use.
Returns
New ControlFlowOp with replaced blocks.
reverse_ops
reverse_ops()
For a composite instruction, reverse the order of sub-instructions.
This is done by recursively reversing all sub-instructions. It does not invert any gate.
Returns
a new instruction with
sub-instructions reversed.
Return type
soft_compare
soft_compare(other)
Soft comparison between gates. Their names, number of qubits, and classical bit numbers must match. The number of parameters must match. Each parameter is compared. If one is a ParameterExpression then it is not taken into account.
Parameters
other (instruction) – other instruction.
Returns
are self and other equal up to parameter expressions.
Return type
to_mutable
to_mutable()
Return a mutable copy of this gate.
This method will return a new mutable copy of this gate instance. If a singleton instance is being used this will be a new unique instance that can be mutated. If the instance is already mutable it will be a deepcopy of that instance.