Barrier#

class qiskit.circuit.library.Barrier(num_qubits, label=None)[source]#

Bases: Instruction

Barrier instruction.

A barrier is a visual indicator of the grouping of a circuit section. It also acts as a directive for circuit compilation to separate pieces of a circuit so that any optimizations or re-writes are constrained to only act between barriers.

Create new barrier instruction.

Parameters:

num_qubits (int) -- the number of qubits for the barrier type [Default: 0].
label (str) -- the barrier label

Raises:

TypeError -- if barrier label is invalid.

Attributes

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

name#: Return the name.

num_clbits#: Return the number of clbits.

num_qubits#: Return the number of qubits.

params#: return instruction params.

unit#: Get the time unit of duration.

Methods

add_decomposition(decomposition)#: Add a decomposition of the instruction to the SessionEquivalenceLibrary.

assemble()#: Assemble a QasmQobjInstruction

broadcast_arguments(qargs, cargs)[source]#

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(classical, val)[source]#: Set a classical equality condition on this instruction between the register or cbit classical and value val.

Note

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(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:: qiskit.circuit.Instruction

inverse()[source]#: Special case. Return self.

is_parameterized()#: Return True .IFF. instruction is parameterized else False

qasm()#

Return a default OpenQASM string for the instruction.

Derived instructions may override this to print in a different format (e.g. measure q[0] -> c[0];).

Deprecated since version 0.25.0: The method qiskit.circuit.instruction.Instruction.qasm() is deprecated as of qiskit-terra 0.25.0. It will be removed no earlier than 3 months after the release date. Correct exporting to OpenQASM 2 is the responsibility of a larger exporter; it cannot safely be done on an object-by-object basis without context. No replacement will be provided, because the premise is wrong.

repeat(n)#

Creates an instruction with gate repeated n amount of times.

Parameters:: n (int) -- Number of times to repeat the instruction
Returns:: Containing the definition.
Return type:: qiskit.circuit.Instruction
Raises:: CircuitError -- If n < 1.

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:

qiskit.circuit.Instruction

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:: bool

validate_parameter(parameter)#: Instruction parameters has no validation or normalization.