QuantumCircuit
qiskit.circuit.QuantumCircuit(*regs, name=None, global_phase=0, metadata=None)
Bases: object
(opens in a new tab)
Create a new circuit.
A circuit is a list of instructions bound to some registers.
Parameters

regs (list(
Register
) or list(int
) or list(list(Bit
))) –The registers to be included in the circuit.

If a list of
Register
objects, represents theQuantumRegister
and/orClassicalRegister
objects to include in the circuit.For example:
QuantumCircuit(QuantumRegister(4))
QuantumCircuit(QuantumRegister(4), ClassicalRegister(3))
QuantumCircuit(QuantumRegister(4, 'qr0'), QuantumRegister(2, 'qr1'))

If a list of
int
, the amount of qubits and/or classical bits to include in the circuit. It can either be a single int for just the number of quantum bits, or 2 ints for the number of quantum bits and classical bits, respectively.For example:
QuantumCircuit(4) # A QuantumCircuit with 4 qubits
QuantumCircuit(4, 3) # A QuantumCircuit with 4 qubits and 3 classical bits

If a list of python lists containing
Bit
objects, a collection ofBit
s to be added to the circuit.


name (str (opens in a new tab)) – the name of the quantum circuit. If not set, an automatically generated string will be assigned.

global_phase (float (opens in a new tab) orParameterExpression) – The global phase of the circuit in radians.

metadata (dict (opens in a new tab)) – Arbitrary key value metadata to associate with the circuit. This gets stored as freeform data in a dict in the
metadata
attribute. It will not be directly used in the circuit.
Raises
CircuitError – if the circuit name, if given, is not valid.
Examples
Construct a simple Bell state circuit.
from qiskit import QuantumCircuit
qc = QuantumCircuit(2, 2)
qc.h(0)
qc.cx(0, 1)
qc.measure([0, 1], [0, 1])
qc.draw('mpl')
Construct a 5qubit GHZ circuit.
from qiskit import QuantumCircuit
qc = QuantumCircuit(5)
qc.h(0)
qc.cx(0, range(1, 5))
qc.measure_all()
Construct a 4qubit BernsteinVazirani circuit using registers.
from qiskit import QuantumRegister, ClassicalRegister, QuantumCircuit
qr = QuantumRegister(3, 'q')
anc = QuantumRegister(1, 'ancilla')
cr = ClassicalRegister(3, 'c')
qc = QuantumCircuit(qr, anc, cr)
qc.x(anc[0])
qc.h(anc[0])
qc.h(qr[0:3])
qc.cx(qr[0:3], anc[0])
qc.h(qr[0:3])
qc.barrier(qr)
qc.measure(qr, cr)
qc.draw('mpl')
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
Return the circuit data (instructions and context).
Returns
a listlike object containing the CircuitInstruction
s for each instruction.
Return type
QuantumCircuitData
extension_lib
= 'include "qelib1.inc";'
global_phase
Return the global phase of the current circuit scope in radians.
header
= 'OPENQASM 2.0;'
instances
= 183
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
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_parameters
The number of parameter objects in the circuit.
num_qubits
Return 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 (opens in a new tab) – When circuit is not scheduled.
parameters
The parameters defined in the circuit.
This attribute returns the Parameter
objects in the circuit sorted alphabetically. Note that parameters instantiated with a ParameterVector
are still sorted numerically.
Examples
The snippet below shows that insertion order of parameters does not matter.
>>> from qiskit.circuit import QuantumCircuit, Parameter
>>> a, b, elephant = Parameter("a"), Parameter("b"), Parameter("elephant")
>>> circuit = QuantumCircuit(1)
>>> circuit.rx(b, 0)
>>> circuit.rz(elephant, 0)
>>> circuit.ry(a, 0)
>>> circuit.parameters # sorted alphabetically!
ParameterView([Parameter(a), Parameter(b), Parameter(elephant)])
Bear in mind that alphabetical sorting might be unintuitive when it comes to numbers. The literal “10” comes before “2” in strict alphabetical sorting.
>>> from qiskit.circuit import QuantumCircuit, Parameter
>>> angles = [Parameter("angle_1"), Parameter("angle_2"), Parameter("angle_10")]
>>> circuit = QuantumCircuit(1)
>>> circuit.u(*angles, 0)
>>> circuit.draw()
┌─────────────────────────────┐
q: ┤ U(angle_1,angle_2,angle_10) ├
└─────────────────────────────┘
>>> circuit.parameters
ParameterView([Parameter(angle_1), Parameter(angle_10), Parameter(angle_2)])
To respect numerical sorting, a ParameterVector
can be used.
>>> from qiskit.circuit import QuantumCircuit, Parameter, ParameterVector
>>> x = ParameterVector("x", 12)
>>> circuit = QuantumCircuit(1)
>>> for x_i in x:
... circuit.rx(x_i, 0)
>>> circuit.parameters
ParameterView([
ParameterVectorElement(x[0]), ParameterVectorElement(x[1]),
ParameterVectorElement(x[2]), ParameterVectorElement(x[3]),
..., ParameterVectorElement(x[11])
])
Returns
The sorted Parameter
objects in the circuit.
prefix
= 'circuit'
qubits
Returns a list of quantum bits in the order that the registers were added.
Methods
add_bits
add_bits(bits)
Add Bits to the circuit.
add_calibration
add_calibration(gate, qubits, schedule, params=None)
Register a lowlevel, custom pulse definition for the given gate.
Parameters
 gate (Union[Gate, str (opens in a new tab)]) – Gate information.
 qubits (Union[int (opens in a new tab), Tuple[int (opens in a new tab)]]) – List of qubits to be measured.
 schedule (Schedule) – Schedule information.
 params (Optional[List[Union[float (opens in a new tab), Parameter]]]) – A list of parameters.
Raises
Exception (opens in a new tab) – if the gate is of type string and params is None.
add_register
add_register(*regs)
Add registers.
append
append(instruction, qargs=None, cargs=None)
Append one or more instructions to the end of the circuit, modifying the circuit in place.
The qargs
and cargs
will be expanded and broadcast according to the rules of the given Instruction
, and any nonBit
specifiers (such as integer indices) will be resolved into the relevant instances.
If a CircuitInstruction
is given, it will be unwrapped, verified in the context of this circuit, and a new object will be appended to the circuit. In this case, you may not pass qargs
or cargs
separately.
Parameters
 instruction (Operation CircuitInstruction) –
Instruction
instance to append, or aCircuitInstruction
with all its context.  qargs (Sequence[QubitSpecifier]  None) – specifiers of the
Qubit
s to attach instruction to.  cargs (Sequence[ClbitSpecifier]  None) – specifiers of the
Clbit
s to attach instruction to.
Returns
a handle to the CircuitInstruction
s that were actually added to the circuit.
Return type
Raises
CircuitError – if the operation passed is not an instance of Instruction
.
assign_parameters
assign_parameters
assign_parameters(parameters: Mapping[Parameter, ParameterExpression  float]  Sequence[ParameterExpression  float], inplace: Literal[False] = False, *, flat_input: bool = False, strict: bool = True) → QuantumCircuit
assign_parameters(parameters: Mapping[Parameter, ParameterExpression  float]  Sequence[ParameterExpression  float], inplace: Literal[True] = False, *, flat_input: bool = False, strict: bool = True) → None
Assign parameters to new parameters or values.
If parameters
is passed as a dictionary, the keys must be Parameter
instances in the current circuit. The values of the dictionary can either be numeric values or new parameter objects.
If parameters
is passed as a list or array, the elements are assigned to the current parameters in the order of parameters
which is sorted alphabetically (while respecting the ordering in ParameterVector
objects).
The values can be assigned to the current circuit object or to a copy of it.
Parameters
 parameters – Either a dictionary or iterable specifying the new parameter values.
 inplace – If False, a copy of the circuit with the bound parameters is returned. If True the circuit instance itself is modified.
 flat_input – If
True
andparameters
is a mapping type, it is assumed to be exactly a mapping of{parameter: value}
. By default (False
), the mapping may also containParameterVector
keys that point to a corresponding sequence of values, and these will be unrolled during the mapping.  strict – If
False
, any parameters given in the mapping that are not used in the circuit will be ignored. IfTrue
(the default), an error will be raised indicating a logic error.
Raises
 CircuitError – If parameters is a dict and contains parameters not present in the circuit.
 ValueError (opens in a new tab) – If parameters is a list/array and the length mismatches the number of free parameters in the circuit.
Returns
A copy of the circuit with bound parameters if inplace
is False, otherwise None.
Examples
Create a parameterized circuit and assign the parameters inplace.
from qiskit.circuit import QuantumCircuit, Parameter
circuit = QuantumCircuit(2)
params = [Parameter('A'), Parameter('B'), Parameter('C')]
circuit.ry(params[0], 0)
circuit.crx(params[1], 0, 1)
circuit.draw('mpl')
circuit.assign_parameters({params[0]: params[2]}, inplace=True)
circuit.draw('mpl')
Bind the values outofplace by list and get a copy of the original circuit.
from qiskit.circuit import QuantumCircuit, ParameterVector
circuit = QuantumCircuit(2)
params = ParameterVector('P', 2)
circuit.ry(params[0], 0)
circuit.crx(params[1], 0, 1)
bound_circuit = circuit.assign_parameters([1, 2])
bound_circuit.draw('mpl')
circuit.draw('mpl')
barrier
barrier(*qargs, label=None)
Apply Barrier
. If qargs
is empty, applies to all qubits in the circuit.
Parameters
 qargs (QubitSpecifier) – Specification for one or more qubit arguments.
 label (str (opens in a new tab)) – The string label of the barrier.
Returns
handle to the added instructions.
Return type
bind_parameters
bind_parameters(values)
Assign numeric parameters to values yielding a new circuit.
If the values are given as list or array they are bound to the circuit in the order of parameters
(see the docstring for more details).
To assign new Parameter objects or bind the values inplace, without yielding a new circuit, use the assign_parameters()
method.
The method qiskit.circuit.quantumcircuit.QuantumCircuit.bind_parameters()
is deprecated as of qiskit 0.45.0. It will be removed no earlier than 3 months after the release date. Use assign_parameters() instead
Parameters
values (Mapping (opens in a new tab)[Parameter, float (opens in a new tab)]  Sequence (opens in a new tab)[float (opens in a new tab)]) – {parameter: value, ...}
or [value1, value2, ...]
Raises
 CircuitError – If values is a dict and contains parameters not present in the circuit.
 TypeError (opens in a new tab) – If values contains a ParameterExpression.
Returns
Copy of self with assignment substitution.
Return type
break_loop
break_loop()
Apply BreakLoopOp
.
If you are using the contextmanager “builder” forms of if_test()
, for_loop()
or while_loop()
, you can only call this method if you are within a loop context, because otherwise the “resource width” of the operation cannot be determined. This would quickly lead to invalid circuits, and so if you are trying to construct a reusable loop body (without the context managers), you must also use the noncontextmanager form of if_test()
and if_else()
. Take care that the BreakLoopOp
instruction must span all the resources of its containing loop, not just the immediate scope.
Returns
A handle to the instruction created.
Raises
CircuitError – if this method was called within a builder context, but not contained within a loop.
Return type
cast
static cast(value, type_)
Best effort to cast value to type. Otherwise, returns the value.
Return type
S  T
cbit_argument_conversion
cbit_argument_conversion(clbit_representation)
Converts several classical bit representations (such as indexes, range, etc.) into a list of classical bits.
Parameters
clbit_representation (Object) – representation to expand
Returns
Where each tuple is a classical bit.
Return type
List(tuple (opens in a new tab))
ccx
ccx(control_qubit1, control_qubit2, target_qubit, ctrl_state=None)
Apply CCXGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 control_qubit1 (QubitSpecifier) – The qubit(s) used as the first control.
 control_qubit2 (QubitSpecifier) – The qubit(s) used as the second control.
 target_qubit (QubitSpecifier) – The qubit(s) targeted by the gate.
 ctrl_state (str (opens in a new tab) int (opens in a new tab)  None) – The control state in decimal, or as a bitstring (e.g. ‘1’). Defaults to controlling on the ‘1’ state.
Returns
A handle to the instructions created.
Return type
ccz
ccz(control_qubit1, control_qubit2, target_qubit, label=None, ctrl_state=None)
Apply CCZGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 control_qubit1 (QubitSpecifier) – The qubit(s) used as the first control.
 control_qubit2 (QubitSpecifier) – The qubit(s) used as the second control.
 target_qubit (QubitSpecifier) – The qubit(s) targeted by the gate.
 label (str (opens in a new tab)  None) – The string label of the gate in the circuit.
 ctrl_state (str (opens in a new tab) int (opens in a new tab)  None) – The control state in decimal, or as a bitstring (e.g. ‘10’). Defaults to controlling on the ‘11’ state.
Returns
A handle to the instructions created.
Return type
ch
ch(control_qubit, target_qubit, label=None, ctrl_state=None)
Apply CHGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 control_qubit (QubitSpecifier) – The qubit(s) used as the control.
 target_qubit (QubitSpecifier) – The qubit(s) targeted by the gate.
 label (str (opens in a new tab)  None) – The string label of the gate in the circuit.
 ctrl_state (str (opens in a new tab) int (opens in a new tab)  None) – The control state in decimal, or as a bitstring (e.g. ‘1’). Defaults to controlling on the ‘1’ state.
Returns
A handle to the instructions created.
Return type
clear
clear()
Clear all instructions in self.
Clearing the circuits will keep the metadata and calibrations.
cls_instances
classmethod cls_instances()
Return the current number of instances of this class, useful for auto naming.
Return type
cls_prefix
classmethod cls_prefix()
Return the prefix to use for auto naming.
Return type
cnot
cnot(control_qubit, target_qubit, label=None, ctrl_state=None)
Apply CXGate
.
For the full matrix form of this gate, see the underlying gate documentation.
The method qiskit.circuit.quantumcircuit.QuantumCircuit.cnot()
is deprecated as of qiskit 0.45.0. It will be removed no earlier than 3 months after the release date. Use QuantumCircuit.cx as direct replacement.
Parameters
 control_qubit (QubitSpecifier) – The qubit(s) used as the control.
 target_qubit (QubitSpecifier) – The qubit(s) targeted by the gate.
 label (str (opens in a new tab)  None) – The string label of the gate in the circuit.
 ctrl_state (str (opens in a new tab) int (opens in a new tab)  None) – The control state in decimal, or as a bitstring (e.g. ‘1’). Defaults to controlling on the ‘1’ state.
Returns
A handle to the instructions created.
Return type
QuantumCircuit.cx: the same function with a different name.
compose
compose(other, qubits=None, clbits=None, front=False, inplace=False, wrap=False)
Compose circuit with other
circuit or instruction, optionally permuting wires.
other
can be narrower or of equal width to self
.
Parameters
 other (qiskit.circuit.Instruction orQuantumCircuit) – (sub)circuit or instruction to compose onto self. If not a
QuantumCircuit
, this can be anything thatappend
will accept.  qubits (list (opens in a new tab)[Qubitint (opens in a new tab)]) – qubits of self to compose onto.
 clbits (list (opens in a new tab)[Clbitint (opens in a new tab)]) – clbits of self to compose onto.
 front (bool (opens in a new tab)) – If True, front composition will be performed. This is not possible within controlflow builder context managers.
 inplace (bool (opens in a new tab)) – If True, modify the object. Otherwise return composed circuit.
 wrap (bool (opens in a new tab)) – If True, wraps the other circuit into a gate (or instruction, depending on whether it contains only unitary instructions) before composing it onto self.
Returns
the composed circuit (returns None if inplace==True).
Return type
Raises
 CircuitError – if no correct wire mapping can be made between the two circuits, such as if
other
is wider thanself
.  CircuitError – if trying to emit a new circuit while
self
has a partially built controlflow context active, such as the contextmanager forms ofif_test()
,for_loop()
andwhile_loop()
.  CircuitError – if trying to compose to the front of a circuit when a controlflow builder block is active; there is no clear meaning to this action.
Examples
>>> lhs.compose(rhs, qubits=[3, 2], inplace=True)
┌───┐ ┌─────┐ ┌───┐
lqr_1_0: ───┤ H ├─── rqr_0: ──■──┤ Tdg ├ lqr_1_0: ───┤ H ├───────────────
├───┤ ┌─┴─┐└─────┘ ├───┤
lqr_1_1: ───┤ X ├─── rqr_1: ┤ X ├─────── lqr_1_1: ───┤ X ├───────────────
┌──┴───┴──┐ └───┘ ┌──┴───┴──┐┌───┐
lqr_1_2: ┤ U1(0.1) ├ + = lqr_1_2: ┤ U1(0.1) ├┤ X ├───────
└─────────┘ └─────────┘└─┬─┘┌─────┐
lqr_2_0: ─────■───── lqr_2_0: ─────■───────■──┤ Tdg ├
┌─┴─┐ ┌─┴─┐ └─────┘
lqr_2_1: ───┤ X ├─── lqr_2_1: ───┤ X ├───────────────
└───┘ └───┘
lcr_0: 0 ═══════════ lcr_0: 0 ═══════════════════════
lcr_1: 0 ═══════════ lcr_1: 0 ═══════════════════════
continue_loop
continue_loop()
Apply ContinueLoopOp
.
If you are using the contextmanager “builder” forms of if_test()
, for_loop()
or while_loop()
, you can only call this method if you are within a loop context, because otherwise the “resource width” of the operation cannot be determined. This would quickly lead to invalid circuits, and so if you are trying to construct a reusable loop body (without the context managers), you must also use the noncontextmanager form of if_test()
and if_else()
. Take care that the ContinueLoopOp
instruction must span all the resources of its containing loop, not just the immediate scope.
Returns
A handle to the instruction created.
Raises
CircuitError – if this method was called within a builder context, but not contained within a loop.
Return type
control
control(num_ctrl_qubits=1, label=None, ctrl_state=None)
Control this circuit on num_ctrl_qubits
qubits.
Parameters
 num_ctrl_qubits (int (opens in a new tab)) – The number of control qubits.
 label (str (opens in a new tab)) – An optional label to give the controlled operation for visualization.
 ctrl_state (str (opens in a new tab) orint (opens in a new tab)) – The control state in decimal or as a bitstring (e.g. ‘111’). If None, use
2**num_ctrl_qubits  1
.
Returns
The controlled version of this circuit.
Return type
Raises
CircuitError – If the circuit contains a nonunitary operation and cannot be controlled.
copy
copy(name=None)
Copy the circuit.
Parameters
name (str (opens in a new tab)) – name to be given to the copied circuit. If None, then the name stays the same.
Returns
a deepcopy of the current circuit, with the specified name
Return type
copy_empty_like
copy_empty_like(name=None)
Return a copy of self with the same structure but empty.
That structure includes:
 name, calibrations and other metadata
 global phase
 all the qubits and clbits, including the registers
Parameters
name (str (opens in a new tab)) – Name for the copied circuit. If None, then the name stays the same.
Returns
An empty copy of self.
Return type
count_ops
count_ops()
Count each operation kind in the circuit.
Returns
a breakdown of how many operations of each kind, sorted by amount.
Return type
OrderedDict
cp
cp(theta, control_qubit, target_qubit, label=None, ctrl_state=None)
Apply CPhaseGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 theta (ParameterValueType) – The angle of the rotation.
 control_qubit (QubitSpecifier) – The qubit(s) used as the control.
 target_qubit (QubitSpecifier) – The qubit(s) targeted by the gate.
 label (str (opens in a new tab)  None) – The string label of the gate in the circuit.
 ctrl_state (str (opens in a new tab) int (opens in a new tab)  None) – The control state in decimal, or as a bitstring (e.g. ‘1’). Defaults to controlling on the ‘1’ state.
Returns
A handle to the instructions created.
Return type
crx
crx(theta, control_qubit, target_qubit, label=None, ctrl_state=None)
Apply CRXGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 theta (ParameterValueType) – The angle of the rotation.
 control_qubit (QubitSpecifier) – The qubit(s) used as the control.
 target_qubit (QubitSpecifier) – The qubit(s) targeted by the gate.
 label (str (opens in a new tab)  None) – The string label of the gate in the circuit.
 ctrl_state (str (opens in a new tab) int (opens in a new tab)  None) – The control state in decimal, or as a bitstring (e.g. ‘1’). Defaults to controlling on the ‘1’ state.
Returns
A handle to the instructions created.
Return type
cry
cry(theta, control_qubit, target_qubit, label=None, ctrl_state=None)
Apply CRYGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 theta (ParameterValueType) – The angle of the rotation.
 control_qubit (QubitSpecifier) – The qubit(s) used as the control.
 target_qubit (QubitSpecifier) – The qubit(s) targeted by the gate.
 label (str (opens in a new tab)  None) – The string label of the gate in the circuit.
 ctrl_state (str (opens in a new tab) int (opens in a new tab)  None) – The control state in decimal, or as a bitstring (e.g. ‘1’). Defaults to controlling on the ‘1’ state.
Returns
A handle to the instructions created.
Return type
crz
crz(theta, control_qubit, target_qubit, label=None, ctrl_state=None)
Apply CRZGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 theta (ParameterValueType) – The angle of the rotation.
 control_qubit (QubitSpecifier) – The qubit(s) used as the control.
 target_qubit (QubitSpecifier) – The qubit(s) targeted by the gate.
 label (str (opens in a new tab)  None) – The string label of the gate in the circuit.
 ctrl_state (str (opens in a new tab) int (opens in a new tab)  None) – The control state in decimal, or as a bitstring (e.g. ‘1’). Defaults to controlling on the ‘1’ state.
Returns
A handle to the instructions created.
Return type
cs
cs(control_qubit, target_qubit, label=None, ctrl_state=None)
Apply CSGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 control_qubit (QubitSpecifier) – The qubit(s) used as the control.
 target_qubit (QubitSpecifier) – The qubit(s) targeted by the gate.
 label (str (opens in a new tab)  None) – The string label of the gate in the circuit.
 ctrl_state (str (opens in a new tab) int (opens in a new tab)  None) – The control state in decimal, or as a bitstring (e.g. ‘1’). Defaults to controlling on the ‘1’ state.
Returns
A handle to the instructions created.
Return type
csdg
csdg(control_qubit, target_qubit, label=None, ctrl_state=None)
Apply CSdgGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 control_qubit (QubitSpecifier) – The qubit(s) used as the control.
 target_qubit (QubitSpecifier) – The qubit(s) targeted by the gate.
 label (str (opens in a new tab)  None) – The string label of the gate in the circuit.
 ctrl_state (str (opens in a new tab) int (opens in a new tab)  None) – The control state in decimal, or as a bitstring (e.g. ‘1’). Defaults to controlling on the ‘1’ state.
Returns
A handle to the instructions created.
Return type
cswap
cswap(control_qubit, target_qubit1, target_qubit2, label=None, ctrl_state=None)
Apply CSwapGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 control_qubit (QubitSpecifier) – The qubit(s) used as the control.
 target_qubit1 (QubitSpecifier) – The qubit(s) targeted by the gate.
 target_qubit2 (QubitSpecifier) – The qubit(s) targeted by the gate.
 label (str (opens in a new tab)  None) – The string label of the gate in the circuit.
 ctrl_state (str (opens in a new tab) int (opens in a new tab)  None) – The control state in decimal, or as a bitstring (e.g.
'1'
). Defaults to controlling on the'1'
state.
Returns
A handle to the instructions created.
Return type
csx
csx(control_qubit, target_qubit, label=None, ctrl_state=None)
Apply CSXGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 control_qubit (QubitSpecifier) – The qubit(s) used as the control.
 target_qubit (QubitSpecifier) – The qubit(s) targeted by the gate.
 label (str (opens in a new tab)  None) – The string label of the gate in the circuit.
 ctrl_state (str (opens in a new tab) int (opens in a new tab)  None) – The control state in decimal, or as a bitstring (e.g. ‘1’). Defaults to controlling on the ‘1’ state.
Returns
A handle to the instructions created.
Return type
cu
cu(theta, phi, lam, gamma, control_qubit, target_qubit, label=None, ctrl_state=None)
Apply CUGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 theta (ParameterValueType) – The $\theta$ rotation angle of the gate.
 phi (ParameterValueType) – The $\phi$ rotation angle of the gate.
 lam (ParameterValueType) – The $\lambda$ rotation angle of the gate.
 gamma (ParameterValueType) – The global phase applied of the U gate, if applied.
 control_qubit (QubitSpecifier) – The qubit(s) used as the control.
 target_qubit (QubitSpecifier) – The qubit(s) targeted by the gate.
 label (str (opens in a new tab)  None) – The string label of the gate in the circuit.
 ctrl_state (str (opens in a new tab) int (opens in a new tab)  None) – The control state in decimal, or as a bitstring (e.g. ‘1’). Defaults to controlling on the ‘1’ state.
Returns
A handle to the instructions created.
Return type
cx
cx(control_qubit, target_qubit, label=None, ctrl_state=None)
Apply CXGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 control_qubit (QubitSpecifier) – The qubit(s) used as the control.
 target_qubit (QubitSpecifier) – The qubit(s) targeted by the gate.
 label (str (opens in a new tab)  None) – The string label of the gate in the circuit.
 ctrl_state (str (opens in a new tab) int (opens in a new tab)  None) – The control state in decimal, or as a bitstring (e.g. ‘1’). Defaults to controlling on the ‘1’ state.
Returns
A handle to the instructions created.
Return type
cy
cy(control_qubit, target_qubit, label=None, ctrl_state=None)
Apply CYGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 control_qubit (QubitSpecifier) – The qubit(s) used as the controls.
 target_qubit (QubitSpecifier) – The qubit(s) targeted by the gate.
 label (str (opens in a new tab)  None) – The string label of the gate in the circuit.
 ctrl_state (str (opens in a new tab) int (opens in a new tab)  None) – The control state in decimal, or as a bitstring (e.g. ‘1’). Defaults to controlling on the ‘1’ state.
Returns
A handle to the instructions created.
Return type
cz
cz(control_qubit, target_qubit, label=None, ctrl_state=None)
Apply CZGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 control_qubit (QubitSpecifier) – The qubit(s) used as the controls.
 target_qubit (QubitSpecifier) – The qubit(s) targeted by the gate.
 label (str (opens in a new tab)  None) – The string label of the gate in the circuit.
 ctrl_state (str (opens in a new tab) int (opens in a new tab)  None) – The control state in decimal, or as a bitstring (e.g. ‘1’). Defaults to controlling on the ‘1’ state.
Returns
A handle to the instructions created.
Return type
dcx
dcx(qubit1, qubit2)
Apply DCXGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 qubit1 (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) to apply the gate to.
 qubit2 (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) to apply the gate to.
Returns
A handle to the instructions created.
Return type
decompose
decompose(gates_to_decompose=None, reps=1)
Call a decomposition pass on this circuit, to decompose one level (shallow decompose).
Parameters
 gates_to_decompose (type (opens in a new tab) orstr (opens in a new tab) orlist (opens in a new tab)(type (opens in a new tab), str (opens in a new tab))) – Optional subset of gates to decompose. Can be a gate type, such as
HGate
, or a gate name, such as ‘h’, or a gate label, such as ‘My H Gate’, or a list of any combination of these. If a gate name is entered, it will decompose all gates with that name, whether the gates have labels or not. Defaults to all gates in circuit.  reps (int (opens in a new tab)) – Optional number of times the circuit should be decomposed. For instance,
reps=2
equals callingcircuit.decompose().decompose()
. can decompose specific gates specific time
Returns
a circuit one level decomposed
Return type
delay
delay(duration, qarg=None, unit='dt')
Apply Delay
. If qarg is None
, applies to all qubits. When applying to multiple qubits, delays with the same duration will be created.
Parameters
 duration (int (opens in a new tab) orfloat (opens in a new tab) orParameterExpression) – duration of the delay.
 qarg (Object) – qubit argument to apply this delay.
 unit (str (opens in a new tab)) – unit of the duration. Supported units:
's'
,'ms'
,'us'
,'ns'
,'ps'
, and'dt'
. Default is'dt'
, i.e. integer time unit depending on the target backend.
Returns
handle to the added instructions.
Return type
Raises
CircuitError – if arguments have bad format.
depth
depth(filter_function=<function QuantumCircuit.<lambda>>)
Return circuit depth (i.e., length of critical path).
Parameters
filter_function (callable) – A function to filter instructions. Should take as input a tuple of (Instruction, list(Qubit), list(Clbit)). Instructions for which the function returns False are ignored in the computation of the circuit depth. By default filters out “directives”, such as barrier or snapshot.
Returns
Depth of circuit.
Return type
Notes
The circuit depth and the DAG depth need not be the same.
diagonal
diagonal(diag, qubit)
Attach a diagonal gate to a circuit.
The decomposition is based on Theorem 7 given in “Synthesis of Quantum Logic Circuits” by Shende et al. (https://arxiv.org/pdf/quantph/0406176.pdf (opens in a new tab)).
The method qiskit.circuit.quantumcircuit.QuantumCircuit.diagonal()
is pending deprecation as of qiskit 0.45.0. It will be marked deprecated in a future release, and then removed no earlier than 3 months after the release date. Instead, compose the circuit with a qiskit.circuit.library.Diagonal circuit.
Parameters
 diag (list (opens in a new tab)) – list of the 2^k diagonal entries (for a diagonal gate on k qubits). Must contain at least two entries
 qubit (QuantumRegister list (opens in a new tab)) – list of k qubits the diagonal is acting on (the order of the qubits specifies the computational basis in which the diagonal gate is provided: the first element in diag acts on the state where all the qubits in q are in the state 0, the second entry acts on the state where all the qubits q[1],…,q[k1] are in the state zero and q[0] is in the state 1, and so on)
Returns
the diagonal gate which was attached to the circuit.
Return type
Raises
QiskitError – if the list of the diagonal entries or the qubit list is in bad format; if the number of diagonal entries is not 2^k, where k denotes the number of qubits
draw
draw(output=None, scale=None, filename=None, style=None, interactive=False, plot_barriers=True, reverse_bits=None, justify=None, vertical_compression='medium', idle_wires=True, with_layout=True, fold=None, ax=None, initial_state=False, cregbundle=None, wire_order=None, expr_len=30)
Draw the quantum circuit. Use the output parameter to choose the drawing format:
text: ASCII art TextDrawing that can be printed in the console.
mpl: images with color rendered purely in Python using matplotlib.
latex: highquality images compiled via latex.
latex_source: raw uncompiled latex output.
Support for Expr
nodes in conditions and SwitchCaseOp.target
fields is preliminary and incomplete. The text
and mpl
drawers will make a besteffort attempt to show data dependencies, but the LaTeXbased drawers will skip these completely.
Parameters
 output (str (opens in a new tab)) – select the output method to use for drawing the circuit. Valid choices are
text
,mpl
,latex
,latex_source
. By default the text drawer is used unless the user config file (usually~/.qiskit/settings.conf
) has an alternative backend set as the default. For example,circuit_drawer = latex
. If the output kwarg is set, that backend will always be used over the default in the user config file.  scale (float (opens in a new tab)) – scale of image to draw (shrink if < 1.0). Only used by the mpl, latex and latex_source outputs. Defaults to 1.0.
 filename (str (opens in a new tab)) – file path to save image to. Defaults to None.
 style (dict (opens in a new tab) orstr (opens in a new tab)) – dictionary of style or file name of style json file. This option is only used by the mpl or latex output type. If style is a str, it is used as the path to a json file which contains a style dict. The file will be opened, parsed, and then any style elements in the dict will replace the default values in the input dict. A file to be loaded must end in
.json
, but the name entered here can omit.json
. For example,style='iqp.json'
orstyle='iqp'
. If style is a dict and the'name'
key is set, that name will be used to load a json file, followed by loading the other items in the style dict. For example,style={'name': 'iqp'}
. If style is not a str and name is not a key in the style dict, then the default value from the user config file (usually~/.qiskit/settings.conf
) will be used, for example,circuit_mpl_style = iqp
. If none of these are set, the clifford style will be used. The search path for style json files can be specified in the user config, for example,circuit_mpl_style_path = /home/user/styles:/home/user
. See:DefaultStyle
for more information on the contents.  interactive (bool (opens in a new tab)) – when set to true, show the circuit in a new window (for mpl this depends on the matplotlib backend being used supporting this). Note when used with either the text or the latex_source output type this has no effect and will be silently ignored. Defaults to False.
 reverse_bits (bool (opens in a new tab)) – when set to True, reverse the bit order inside registers for the output visualization. Defaults to False unless the user config file (usually
~/.qiskit/settings.conf
) has an alternative value set. For example,circuit_reverse_bits = True
.  plot_barriers (bool (opens in a new tab)) – enable/disable drawing barriers in the output circuit. Defaults to True.
 justify (string) – options are
left
,right
ornone
. If anything else is supplied, it defaults to left justified. It refers to where gates should be placed in the output circuit if there is an option.none
results in each gate being placed in its own column.  vertical_compression (string) –
high
,medium
orlow
. It merges the lines generated by the text output so the drawing will take less vertical room. Default ismedium
. Only used by the text output, will be silently ignored otherwise.  idle_wires (bool (opens in a new tab)) – include idle wires (wires with no circuit elements) in output visualization. Default is True.
 with_layout (bool (opens in a new tab)) – include layout information, with labels on the physical layout. Default is True.
 fold (int (opens in a new tab)) – sets pagination. It can be disabled using 1. In text, sets the length of the lines. This is useful when the drawing does not fit in the console. If None (default), it will try to guess the console width using
shutil.get_terminal_size()
. However, if running in jupyter, the default line length is set to 80 characters. In mpl, it is the number of (visual) layers before folding. Default is 25.  ax (matplotlib.axes.Axes (opens in a new tab)) – Only used by the mpl backend. An optional Axes object to be used for the visualization output. If none is specified, a new matplotlib Figure will be created and used. Additionally, if specified there will be no returned Figure since it is redundant.
 initial_state (bool (opens in a new tab)) – Optional. Adds
0>
in the beginning of the wire. Default is False.  cregbundle (bool (opens in a new tab)) – Optional. If set True, bundle classical registers. Default is True, except for when
output
is set to"text"
.  wire_order (list (opens in a new tab)) – Optional. A list of integers used to reorder the display of the bits. The list must have an entry for every bit with the bits in the range 0 to (
num_qubits
+num_clbits
).  expr_len (int (opens in a new tab)) – Optional. The number of characters to display if an
Expr
is used for the condition in aControlFlowOp
. If this number is exceeded, the string will be truncated at that number and ‘…’ added to the end.
Returns
TextDrawing
or matplotlib.figure
or PIL.Image
or str
(opens in a new tab):

TextDrawing (output=’text’)
A drawing that can be printed as ascii art.

matplotlib.figure.Figure (output=’mpl’)
A matplotlib figure object for the circuit diagram.

PIL.Image (output=’latex’)
An inmemory representation of the image of the circuit diagram.

str (output=’latex_source’)
The LaTeX source code for visualizing the circuit diagram.
Raises
 VisualizationError – when an invalid output method is selected
 ImportError (opens in a new tab) – when the output methods requires noninstalled libraries.
Example
from qiskit import QuantumRegister, ClassicalRegister, QuantumCircuit
q = QuantumRegister(1)
c = ClassicalRegister(1)
qc = QuantumCircuit(q, c)
qc.h(q)
qc.measure(q, c)
qc.draw(output='mpl', style={'backgroundcolor': '#EEEEEE'})
ecr
ecr(qubit1, qubit2)
Apply ECRGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 qubit1 (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubits to apply the gate to.
 qubit2 (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubits to apply the gate to.
Returns
A handle to the instructions created.
Return type
find_bit
find_bit(bit)
Find locations in the circuit which can be used to reference a given Bit
.
Parameters
bit (Bit) – The bit to locate.
Returns
A 2tuple. The first element (index
)
contains the index at which the Bit
can be found (in either qubits
, clbits
, depending on its type). The second element (registers
) is a list of (register, index)
pairs with an entry for each Register
in the circuit which contains the Bit
(and the index in the Register
at which it can be found).
Return type
namedtuple(int (opens in a new tab), List[Tuple(Register, int (opens in a new tab))])
Notes
The circuit index of an AncillaQubit
will be its index in qubits
, not ancillas
.
Raises
 CircuitError – If the supplied
Bit
was of an unknown type.  CircuitError – If the supplied
Bit
could not be found on the circuit.
Return type
BitLocations
for_loop
for_loop
for_loop(indexset: Iterable[int], loop_parameter: Parameter  None, body: None, qubits: None, clbits: None, *, label: str  None) → qiskit.circuit.controlflow.for_loop.ForLoopContext
for_loop(indexset: Iterable[int], loop_parameter: Parameter  None, body: QuantumCircuit, qubits: Sequence[Qubit  QuantumRegister  int  slice  Sequence[Qubit  int]], clbits: Sequence[Clbit  ClassicalRegister  int  slice  Sequence[Clbit  int]], *, label: str  None) → InstructionSet
Create a for
loop on this circuit.
There are two forms for calling this function. If called with all its arguments (with the possible exception of label
), it will create a ForLoopOp
with the given body
. If body
(and qubits
and clbits
) are not passed, then this acts as a context manager, which, when entered, provides a loop variable (unless one is given, in which case it will be reused) and will automatically build a ForLoopOp
when the scope finishes. In this form, you do not need to keep track of the qubits or clbits you are using, because the scope will handle it for you.
For example:
from qiskit import QuantumCircuit
qc = QuantumCircuit(2, 1)
with qc.for_loop(range(5)) as i:
qc.h(0)
qc.cx(0, 1)
qc.measure(0, 0)
qc.break_loop().c_if(0, True)
Parameters

indexset (Iterable[int (opens in a new tab)]) – A collection of integers to loop over. Always necessary.

loop_parameter (Optional[Parameter]) –
The parameter used within
body
to which the values fromindexset
will be assigned. In the contextmanager form, if this argument is not supplied, then a loop parameter will be allocated for you and returned as the value of thewith
statement. This will only be bound into the circuit if it is used within the body.If this argument is
None
in the manual form of this method,body
will be repeated once for each of the items inindexset
but their values will be ignored. 
body (Optional[QuantumCircuit]) – The loop body to be repeatedly executed. Omit this to use the contextmanager mode.

qubits (Optional[Sequence[QubitSpecifier]]) – The circuit qubits over which the loop body should be run. Omit this to use the contextmanager mode.

clbits (Optional[Sequence[ClbitSpecifier]]) – The circuit clbits over which the loop body should be run. Omit this to use the contextmanager mode.

label (Optional[str (opens in a new tab)]) – The string label of the instruction in the circuit.
Returns
depending on the call signature, either a context manager for creating the for loop (it will automatically be added to the circuit at the end of the block), or an InstructionSet
handle to the appended loop operation.
Return type
InstructionSet or ForLoopContext
Raises
CircuitError – if an incorrect calling convention is used.
fredkin
fredkin(control_qubit, target_qubit1, target_qubit2)
Apply CSwapGate
.
For the full matrix form of this gate, see the underlying gate documentation.
The method qiskit.circuit.quantumcircuit.QuantumCircuit.fredkin()
is deprecated as of qiskit 0.45.0. It will be removed no earlier than 3 months after the release date. Use QuantumCircuit.cswap as direct replacement.
Parameters
 control_qubit (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) used as the control.
 target_qubit1 (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) targeted by the gate.
 target_qubit2 (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) targeted by the gate.
Returns
A handle to the instructions created.
Return type
QuantumCircuit.cswap: the same function with a different name.
from_instructions
static from_instructions(instructions, *, qubits=(), clbits=(), name=None, global_phase=0, metadata=None)
Construct a circuit from an iterable of CircuitInstructions.
Parameters
 instructions (Iterable[CircuitInstruction tuple (opens in a new tab)[qiskit.circuit.Instruction]  tuple (opens in a new tab)[qiskit.circuit.Instruction, Iterable[Qubit]]  tuple (opens in a new tab)[qiskit.circuit.Instruction, Iterable[Qubit], Iterable[Clbit]]]) – The instructions to add to the circuit.
 qubits (Iterable[Qubit]) – Any qubits to add to the circuit. This argument can be used, for example, to enforce a particular ordering of qubits.
 clbits (Iterable[Clbit]) – Any classical bits to add to the circuit. This argument can be used, for example, to enforce a particular ordering of classical bits.
 name (str (opens in a new tab)  None) – The name of the circuit.
 global_phase (ParameterValueType) – The global phase of the circuit in radians.
 metadata (dict (opens in a new tab)  None) – Arbitrary key value metadata to associate with the circuit.
Returns
The quantum circuit.
Return type
from_qasm_file
static from_qasm_file(path)
Read an OpenQASM 2.0 program from a file and convert to an instance of QuantumCircuit
.
Parameters
path (str (opens in a new tab)) – Path to the file for an OpenQASM 2 program
Returns
The QuantumCircuit object for the input OpenQASM 2.
Return type
qasm2.load()
: the complete interface to the OpenQASM 2 importer.
from_qasm_str
static from_qasm_str(qasm_str)
Convert a string containing an OpenQASM 2.0 program to a QuantumCircuit
.
Parameters
qasm_str (str (opens in a new tab)) – A string containing an OpenQASM 2.0 program.
Returns
The QuantumCircuit object for the input OpenQASM 2
Return type
qasm2.loads()
: the complete interface to the OpenQASM 2 importer.
get_instructions
get_instructions(name)
Get instructions matching name.
Parameters
name (str (opens in a new tab)) – The name of instruction to.
Returns
list of (instruction, qargs, cargs).
Return type
list (opens in a new tab)(tuple (opens in a new tab))
h
h(qubit)
Apply HGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
qubit (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) to apply the gate to.
Returns
A handle to the instructions created.
Return type
hamiltonian
hamiltonian(operator, time, qubits, label=None)
Apply hamiltonian evolution to qubits.
This gate resolves to a UnitaryGate
as $U(t) = exp(i t H)$, which can be decomposed into basis gates if it is 2 qubits or less, or simulated directly in Aer for more qubits.
The method qiskit.circuit.quantumcircuit.QuantumCircuit.hamiltonian()
is pending deprecation as of qiskit 0.45.0. It will be marked deprecated in a future release, and then removed no earlier than 3 months after the release date. Instead, append a qiskit.circuit.library.HamiltonianGate to the circuit.
Parameters
 operator (matrix or Operator) – a hermitian operator.
 time (float (opens in a new tab) orParameterExpression) – time evolution parameter.
 qubits (Union[int (opens in a new tab), Tuple[int (opens in a new tab)]]) – The circuit qubits to apply the transformation to.
 label (str (opens in a new tab)) – unitary name for backend [Default: None].
Returns
The quantum circuit.
Return type
has_calibration_for
has_calibration_for(instruction)
Return True if the circuit has a calibration defined for the instruction context. In this case, the operation does not need to be translated to the device basis.
has_register
has_register(register)
Test if this circuit has the register r.
Parameters
register (Register) – a quantum or classical register.
Returns
True if the register is contained in this circuit.
Return type
i
i(qubit)
Apply IGate
.
For the full matrix form of this gate, see the underlying gate documentation.
The method qiskit.circuit.quantumcircuit.QuantumCircuit.i()
is deprecated as of qiskit 0.45.0. It will be removed no earlier than 3 months after the release date. Use QuantumCircuit.id as direct replacement.
Parameters
qubit (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) to apply the gate to.
Returns
A handle to the instructions created.
Return type
id
id(qubit)
Apply IGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
qubit (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) to apply the gate to.
Returns
A handle to the instructions created.
Return type
if_else
if_else(condition, true_body, false_body, qubits, clbits, label=None)
Apply IfElseOp
.
This method does not have an associated contextmanager form, because it is already handled by the if_test()
method. You can use the else
part of that with something such as:
from qiskit.circuit import QuantumCircuit, Qubit, Clbit
bits = [Qubit(), Qubit(), Clbit()]
qc = QuantumCircuit(bits)
qc.h(0)
qc.cx(0, 1)
qc.measure(0, 0)
with qc.if_test((bits[2], 0)) as else_:
qc.h(0)
with else_:
qc.x(0)
Parameters
 condition (tuple (opens in a new tab)[ClassicalRegister, int (opens in a new tab)]  tuple (opens in a new tab)[Clbit, int (opens in a new tab)]  tuple (opens in a new tab)[Clbit, bool (opens in a new tab)]) – A condition to be evaluated at circuit runtime which, if true, will trigger the evaluation of
true_body
. Can be specified as either a tuple of aClassicalRegister
to be tested for equality with a givenint
, or as a tuple of aClbit
to be compared to either abool
or anint
.  true_body (QuantumCircuit) – The circuit body to be run if
condition
is true.  false_body (QuantumCircuit) – The circuit to be run if
condition
is false.  qubits (Sequence[QubitSpecifier]) – The circuit qubits over which the if/else should be run.
 clbits (Sequence[ClbitSpecifier]) – The circuit clbits over which the if/else should be run.
 label (str (opens in a new tab)  None) – The string label of the instruction in the circuit.
Raises
CircuitError – If the provided condition references Clbits outside the enclosing circuit.
Returns
A handle to the instruction created.
Return type
if_test
if_test
if_test(condition: tuple[ClassicalRegister  Clbit, int], true_body: None, qubits: None, clbits: None, *, label: str  None) → qiskit.circuit.controlflow.if_else.IfContext
if_test(condition: tuple[ClassicalRegister  Clbit, int], true_body: QuantumCircuit, qubits: Sequence[Qubit  QuantumRegister  int  slice  Sequence[Qubit  int]], clbits: Sequence[Clbit  ClassicalRegister  int  slice  Sequence[Clbit  int]], *, label: str  None = None) → InstructionSet
Create an if
statement on this circuit.
There are two forms for calling this function. If called with all its arguments (with the possible exception of label
), it will create a IfElseOp
with the given true_body
, and there will be no branch for the false
condition (see also the if_else()
method). However, if true_body
(and qubits
and clbits
) are not passed, then this acts as a context manager, which can be used to build if
statements. The return value of the with
statement is a chainable context manager, which can be used to create subsequent else
blocks. In this form, you do not need to keep track of the qubits or clbits you are using, because the scope will handle it for you.
For example:
from qiskit.circuit import QuantumCircuit, Qubit, Clbit
bits = [Qubit(), Qubit(), Qubit(), Clbit(), Clbit()]
qc = QuantumCircuit(bits)
qc.h(0)
qc.cx(0, 1)
qc.measure(0, 0)
qc.h(0)
qc.cx(0, 1)
qc.measure(0, 1)
with qc.if_test((bits[3], 0)) as else_:
qc.x(2)
with else_:
qc.h(2)
qc.z(2)
Parameters
 condition (Tuple[Union[ClassicalRegister, Clbit], int (opens in a new tab)]) – A condition to be evaluated at circuit runtime which, if true, will trigger the evaluation of
true_body
. Can be specified as either a tuple of aClassicalRegister
to be tested for equality with a givenint
, or as a tuple of aClbit
to be compared to either abool
or anint
.  true_body (Optional[QuantumCircuit]) – The circuit body to be run if
condition
is true.  qubits (Optional[Sequence[QubitSpecifier]]) – The circuit qubits over which the if/else should be run.
 clbits (Optional[Sequence[ClbitSpecifier]]) – The circuit clbits over which the if/else should be run.
 label (Optional[str (opens in a new tab)]) – The string label of the instruction in the circuit.
Returns
depending on the call signature, either a context manager for creating the if
block (it will automatically be added to the circuit at the end of the block), or an InstructionSet
handle to the appended conditional operation.
Return type
InstructionSet or IfContext
Raises
 CircuitError – If the provided condition references Clbits outside the enclosing circuit.
 CircuitError – if an incorrect calling convention is used.
Returns
A handle to the instruction created.
initialize
initialize(params, qubits=None, normalize=False)
Initialize qubits in a specific state.
Qubit initialization is done by first resetting the qubits to $0\rangle$ followed by calling qiskit.extensions.StatePreparation
class to prepare the qubits in a specified state. Both these steps are included in the qiskit.extensions.Initialize
instruction.
Parameters

params (Sequence[complex (opens in a new tab)]  str (opens in a new tab) int (opens in a new tab)) –
The state to initialize to, can be either of the following.
 Statevector or vector of complex amplitudes to initialize to.
 Labels of basis states of the Pauli eigenstates Z, X, Y. See
Statevector.from_label()
. Notice the order of the labels is reversed with respect to the qubit index to be applied to. Example label ‘01’ initializes the qubit zero to $1\rangle$ and the qubit one to $0\rangle$.  An integer that is used as a bitmap indicating which qubits to initialize to $1\rangle$. Example: setting params to 5 would initialize qubit 0 and qubit 2 to $1\rangle$ and qubit 1 to $0\rangle$.

qubits (Sequence[QubitSpecifier]  None) – Qubits to initialize. If
None
the initialization is applied to all qubits in the circuit. 
normalize (bool (opens in a new tab)) – Whether to normalize an input array to a unit vector.
Returns
A handle to the instructions created.
Examples
Prepare a qubit in the state $(0\rangle  1\rangle) / \sqrt{2}$.
import numpy as np
from qiskit import QuantumCircuit
circuit = QuantumCircuit(1)
circuit.initialize([1/np.sqrt(2), 1/np.sqrt(2)], 0)
circuit.draw()
output:
┌──────────────────────────────┐
q_0: ┤ Initialize(0.70711,0.70711) ├
└──────────────────────────────┘
Initialize from a string two qubits in the state $10\rangle$. The order of the labels is reversed with respect to qubit index. More information about labels for basis states are in Statevector.from_label()
.
import numpy as np
from qiskit import QuantumCircuit
circuit = QuantumCircuit(2)
circuit.initialize('01', circuit.qubits)
circuit.draw()
output:
┌──────────────────┐
q_0: ┤0 ├
│ Initialize(0,1) │
q_1: ┤1 ├
└──────────────────┘
Initialize two qubits from an array of complex amplitudes.
import numpy as np
from qiskit import QuantumCircuit
circuit = QuantumCircuit(2)
circuit.initialize([0, 1/np.sqrt(2), 1.j/np.sqrt(2), 0], circuit.qubits)
circuit.draw()
output:
┌────────────────────────────────────┐
q_0: ┤0 ├
│ Initialize(0,0.70711,0.70711j,0) │
q_1: ┤1 ├
└────────────────────────────────────┘
inverse
inverse()
Invert (take adjoint of) this circuit.
This is done by recursively inverting all gates.
Returns
the inverted circuit
Return type
Raises
CircuitError – if the circuit cannot be inverted.
Examples
input:
┌───┐
q_0: ┤ H ├─────■──────
└───┘┌────┴─────┐
q_1: ─────┤ RX(1.57) ├
└──────────┘
output:
┌───┐
q_0: ──────■──────┤ H ├
┌─────┴─────┐└───┘
q_1: ┤ RX(1.57) ├─────
└───────────┘
iso
iso(isometry, q_input, q_ancillas_for_output, q_ancillas_zero=None, q_ancillas_dirty=None, epsilon=1e10)
Attach an arbitrary isometry from m to n qubits to a circuit. In particular, this allows to attach arbitrary unitaries on n qubits (m=n) or to prepare any state on n qubits (m=0). The decomposition used here was introduced by Iten et al. in https://arxiv.org/abs/1501.06911 (opens in a new tab).
The method qiskit.circuit.quantumcircuit.QuantumCircuit.iso()
is pending deprecation as of qiskit 0.45.0. It will be marked deprecated in a future release, and then removed no earlier than 3 months after the release date. Instead, append a qiskit.circuit.library.Isometry to the circuit.
Parameters
 isometry (ndarray) – an isometry from m to n qubits, i.e., a (complex) ndarray of dimension 2^n×2^m with orthonormal columns (given in the computational basis specified by the order of the ancillas and the input qubits, where the ancillas are considered to be more significant than the input qubits.).
 q_input (QuantumRegister list (opens in a new tab)[Qubit]) – list of m qubits where the input to the isometry is fed in (empty list for state preparation).
 q_ancillas_for_output (QuantumRegister list (opens in a new tab)[Qubit]) – list of nm ancilla qubits that are used for the output of the isometry and which are assumed to start in the zero state. The qubits are listed with increasing significance.
 q_ancillas_zero (QuantumRegister list (opens in a new tab)[Qubit]) – list of ancilla qubits which are assumed to start in the zero state. Default is q_ancillas_zero = None.
 q_ancillas_dirty (QuantumRegister list (opens in a new tab)[Qubit]) – list of ancilla qubits which can start in an arbitrary state. Default is q_ancillas_dirty = None.
 epsilon (float (opens in a new tab)) – error tolerance of calculations. Default is epsilon = _EPS.
Returns
the isometry is attached to the quantum circuit.
Return type
Raises
QiskitError – if the array is not an isometry of the correct size corresponding to the provided number of qubits.
isometry
isometry(isometry, q_input, q_ancillas_for_output, q_ancillas_zero=None, q_ancillas_dirty=None, epsilon=1e10)
Attach an arbitrary isometry from m to n qubits to a circuit. In particular, this allows to attach arbitrary unitaries on n qubits (m=n) or to prepare any state on n qubits (m=0). The decomposition used here was introduced by Iten et al. in https://arxiv.org/abs/1501.06911 (opens in a new tab).
The method qiskit.circuit.quantumcircuit.QuantumCircuit.iso()
is pending deprecation as of qiskit 0.45.0. It will be marked deprecated in a future release, and then removed no earlier than 3 months after the release date. Instead, append a qiskit.circuit.library.Isometry to the circuit.
Parameters
 isometry (ndarray) – an isometry from m to n qubits, i.e., a (complex) ndarray of dimension 2^n×2^m with orthonormal columns (given in the computational basis specified by the order of the ancillas and the input qubits, where the ancillas are considered to be more significant than the input qubits.).
 q_input (QuantumRegister list (opens in a new tab)[Qubit]) – list of m qubits where the input to the isometry is fed in (empty list for state preparation).
 q_ancillas_for_output (QuantumRegister list (opens in a new tab)[Qubit]) – list of nm ancilla qubits that are used for the output of the isometry and which are assumed to start in the zero state. The qubits are listed with increasing significance.
 q_ancillas_zero (QuantumRegister list (opens in a new tab)[Qubit]) – list of ancilla qubits which are assumed to start in the zero state. Default is q_ancillas_zero = None.
 q_ancillas_dirty (QuantumRegister list (opens in a new tab)[Qubit]) – list of ancilla qubits which can start in an arbitrary state. Default is q_ancillas_dirty = None.
 epsilon (float (opens in a new tab)) – error tolerance of calculations. Default is epsilon = _EPS.
Returns
the isometry is attached to the quantum circuit.
Return type
Raises
QiskitError – if the array is not an isometry of the correct size corresponding to the provided number of qubits.
iswap
iswap(qubit1, qubit2)
Apply iSwapGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 qubit1 (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubits to apply the gate to.
 qubit2 (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubits to apply the gate to.
Returns
A handle to the instructions created.
Return type
mcp
mcp(lam, control_qubits, target_qubit)
Apply MCPhaseGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 lam (ParameterExpression float (opens in a new tab)) – The angle of the rotation.
 control_qubits (Sequence (opens in a new tab)[Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]]) – The qubits used as the controls.
 target_qubit (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) targeted by the gate.
Returns
A handle to the instructions created.
Return type
mcrx
mcrx(theta, q_controls, q_target, use_basis_gates=False)
Apply MultipleControlled X rotation gate
Parameters
 self (QuantumCircuit) – The QuantumCircuit object to apply the mcrx gate on.
 theta (float (opens in a new tab)) – angle theta
 q_controls (QuantumRegister orlist (opens in a new tab)(Qubit)) – The list of control qubits
 q_target (Qubit) – The target qubit
 use_basis_gates (bool (opens in a new tab)) – use p, u, cx
Raises
QiskitError – parameter errors
mcry
mcry(theta, q_controls, q_target, q_ancillae=None, mode=None, use_basis_gates=False)
Apply MultipleControlled Y rotation gate
Parameters
 self (QuantumCircuit) – The QuantumCircuit object to apply the mcry gate on.
 theta (float (opens in a new tab)) – angle theta
 q_controls (list (opens in a new tab)(Qubit)) – The list of control qubits
 q_target (Qubit) – The target qubit
 q_ancillae (QuantumRegister ortuple (opens in a new tab)(QuantumRegister, int (opens in a new tab))) – The list of ancillary qubits.
 mode (string) – The implementation mode to use
 use_basis_gates (bool (opens in a new tab)) – use p, u, cx
Raises
QiskitError – parameter errors
mcrz
mcrz(lam, q_controls, q_target, use_basis_gates=False)
Apply MultipleControlled Z rotation gate
Parameters
 self (QuantumCircuit) – The QuantumCircuit object to apply the mcrz gate on.
 lam (float (opens in a new tab)) – angle lambda
 q_controls (list (opens in a new tab)(Qubit)) – The list of control qubits
 q_target (Qubit) – The target qubit
 use_basis_gates (bool (opens in a new tab)) – use p, u, cx
Raises
QiskitError – parameter errors
mct
mct(control_qubits, target_qubit, ancilla_qubits=None, mode='noancilla')
Apply MCXGate
.
The multicX gate can be implemented using different techniques, which use different numbers of ancilla qubits and have varying circuit depth. These modes are:
'noancilla'
: Requires 0 ancilla qubits.'recursion'
: Requires 1 ancilla qubit if more than 4 controls are used, otherwise 0.'vchain'
: Requires 2 less ancillas than the number of control qubits.'vchaindirty'
: Same as for the clean ancillas (but the circuit will be longer).
For the full matrix form of this gate, see the underlying gate documentation.
The method qiskit.circuit.quantumcircuit.QuantumCircuit.mct()
is deprecated as of qiskit 0.45.0. It will be removed no earlier than 3 months after the release date. Use QuantumCircuit.mcx as direct replacement.
Parameters
 control_qubits (Sequence[QubitSpecifier]) – The qubits used as the controls.
 target_qubit (QubitSpecifier) – The qubit(s) targeted by the gate.
 ancilla_qubits (QubitSpecifier  Sequence[QubitSpecifier]  None) – The qubits used as the ancillae, if the mode requires them.
 mode (str (opens in a new tab)) – The choice of mode, explained further above.
Returns
A handle to the instructions created.
Raises
 ValueError (opens in a new tab) – if the given mode is not known, or if too few ancilla qubits are passed.
 AttributeError (opens in a new tab) – if no ancilla qubits are passed, but some are needed.
Return type
QuantumCircuit.mcx: the same gate with a different name.
mcx
mcx(control_qubits, target_qubit, ancilla_qubits=None, mode='noancilla')
Apply MCXGate
.
The multicX gate can be implemented using different techniques, which use different numbers of ancilla qubits and have varying circuit depth. These modes are:
'noancilla'
: Requires 0 ancilla qubits.'recursion'
: Requires 1 ancilla qubit if more than 4 controls are used, otherwise 0.'vchain'
: Requires 2 less ancillas than the number of control qubits.'vchaindirty'
: Same as for the clean ancillas (but the circuit will be longer).
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 control_qubits (Sequence[QubitSpecifier]) – The qubits used as the controls.
 target_qubit (QubitSpecifier) – The qubit(s) targeted by the gate.
 ancilla_qubits (QubitSpecifier  Sequence[QubitSpecifier]  None) – The qubits used as the ancillae, if the mode requires them.
 mode (str (opens in a new tab)) – The choice of mode, explained further above.
Returns
A handle to the instructions created.
Raises
 ValueError (opens in a new tab) – if the given mode is not known, or if too few ancilla qubits are passed.
 AttributeError (opens in a new tab) – if no ancilla qubits are passed, but some are needed.
Return type
measure
measure(qubit, cbit)
Measure a quantum bit (qubit
) in the Z basis into a classical bit (cbit
).
When a quantum state is measured, a qubit is projected in the computational (Pauli Z) basis to either $\lvert 0 \rangle$ or $\lvert 1 \rangle$. The classical bit cbit
indicates the result of that projection as a 0
or a 1
respectively. This operation is nonreversible.
Parameters
 qubit (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – qubit(s) to measure.
 cbit (Clbit ClassicalRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Clbit int (opens in a new tab)]) – classical bit(s) to place the measurement result(s) in.
Returns
handle to the added instructions.
Return type
Raises
CircuitError – if arguments have bad format.
Examples
In this example, a qubit is measured and the result of that measurement is stored in the classical bit (usually expressed in diagrams as a double line):
from qiskit import QuantumCircuit
circuit = QuantumCircuit(1, 1)
circuit.h(0)
circuit.measure(0, 0)
circuit.draw()
┌───┐┌─┐
q: ┤ H ├┤M├
└───┘└╥┘
c: 1/══════╩═
0
It is possible to call measure
with lists of qubits
and cbits
as a shortcut for onetoone measurement. These two forms produce identical results:
circuit = QuantumCircuit(2, 2)
circuit.measure([0,1], [0,1])
circuit = QuantumCircuit(2, 2)
circuit.measure(0, 0)
circuit.measure(1, 1)
Instead of lists, you can use QuantumRegister
and ClassicalRegister
under the same logic.
from qiskit import QuantumCircuit, QuantumRegister, ClassicalRegister
qreg = QuantumRegister(2, "qreg")
creg = ClassicalRegister(2, "creg")
circuit = QuantumCircuit(qreg, creg)
circuit.measure(qreg, creg)
This is equivalent to:
circuit = QuantumCircuit(qreg, creg)
circuit.measure(qreg[0], creg[0])
circuit.measure(qreg[1], creg[1])
measure_active
measure_active(inplace=True)
Adds measurement to all nonidle qubits. Creates a new ClassicalRegister with a size equal to the number of nonidle qubits being measured.
Returns a new circuit with measurements if inplace=False.
Parameters
inplace (bool (opens in a new tab)) – All measurements inplace or return new circuit.
Returns
Returns circuit with measurements when inplace = False.
Return type
measure_all
measure_all(inplace=True, add_bits=True)
Adds measurement to all qubits.
By default, adds new classical bits in a ClassicalRegister
to store these measurements. If add_bits=False
, the results of the measurements will instead be stored in the already existing classical bits, with qubit n
being measured into classical bit n
.
Returns a new circuit with measurements if inplace=False
.
Parameters
 inplace (bool (opens in a new tab)) – All measurements inplace or return new circuit.
 add_bits (bool (opens in a new tab)) – Whether to add new bits to store the results.
Returns
Returns circuit with measurements when inplace=False
.
Return type
Raises
CircuitError – if add_bits=False
but there are not enough classical bits.
ms
ms(theta, qubits)
Apply MSGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 theta (ParameterExpression float (opens in a new tab)) – The angle of the rotation.
 qubits (Sequence (opens in a new tab)[Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]]) – The qubits to apply the gate to.
Returns
A handle to the instructions created.
Return type
num_connected_components
num_connected_components(unitary_only=False)
How many nonentangled subcircuits can the circuit be factored to.
Parameters
unitary_only (bool (opens in a new tab)) – Compute only unitary part of graph.
Returns
Number of connected components in circuit.
Return type
num_nonlocal_gates
num_nonlocal_gates()
Return number of nonlocal gates (i.e. involving 2+ qubits).
Conditional nonlocal gates are also included.
Return type
num_tensor_factors
num_tensor_factors()
Computes the number of tensor factors in the unitary (quantum) part of the circuit only.
Notes
This is here for backwards compatibility, and will be removed in a future release of Qiskit. You should call num_unitary_factors instead.
Return type
num_unitary_factors
num_unitary_factors()
Computes the number of tensor factors in the unitary (quantum) part of the circuit only.
Return type
p
p(theta, qubit)
Apply PhaseGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 theta (ParameterExpression float (opens in a new tab)) – THe angle of the rotation.
 qubit (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) to apply the gate to.
Returns
A handle to the instructions created.
Return type
pauli
pauli(pauli_string, qubits)
Apply PauliGate
.
Parameters
 pauli_string (str (opens in a new tab)) – A string representing the Pauli operator to apply, e.g. ‘XX’.
 qubits (Sequence (opens in a new tab)[Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]]) – The qubits to apply this gate to.
Returns
A handle to the instructions created.
Return type
power
power(power, matrix_power=False)
Raise this circuit to the power of power
.
If power
is a positive integer and matrix_power
is False
, this implementation defaults to calling repeat
. Otherwise, if the circuit is unitary, the matrix is computed to calculate the matrix power.
Parameters
 power (float (opens in a new tab)) – The power to raise this circuit to.
 matrix_power (bool (opens in a new tab)) – If True, the circuit is converted to a matrix and then the matrix power is computed. If False, and
power
is a positive integer, the implementation defaults torepeat
.
Raises
CircuitError – If the circuit needs to be converted to a gate but it is not unitary.
Returns
A circuit implementing this circuit raised to the power of power
.
Return type
prepare_state
prepare_state(state, qubits=None, label=None, normalize=False)
Prepare qubits in a specific state.
This class implements a state preparing unitary. Unlike qiskit.extensions.Initialize
it does not reset the qubits first.
Parameters

state (str (opens in a new tab) orlist (opens in a new tab) orint (opens in a new tab) orStatevector) –
 Statevector: Statevector to initialize to.
 str: labels of basis states of the Pauli eigenstates Z, X, Y. See
Statevector.from_label()
. Notice the order of the labels is reversed with respect to the qubit index to be applied to. Example label ‘01’ initializes the qubit zero to $1\rangle$ and the qubit one to $0\rangle$.  list: vector of complex amplitudes to initialize to.
 int: an integer that is used as a bitmap indicating which qubits to initialize to $1\rangle$. Example: setting params to 5 would initialize qubit 0 and qubit 2 to $1\rangle$ and qubit 1 to $0\rangle$.

qubits (QuantumRegister orQubit orint (opens in a new tab)) –
 QuantumRegister: A list of qubits to be initialized [Default: None].
 Qubit: Single qubit to be initialized [Default: None].
 int: Index of qubit to be initialized [Default: None].
 list: Indexes of qubits to be initialized [Default: None].

label (str (opens in a new tab)) – An optional label for the gate

normalize (bool (opens in a new tab)) – Whether to normalize an input array to a unit vector.
Returns
a handle to the instruction that was just initialized
Return type
Examples
Prepare a qubit in the state $(0\rangle  1\rangle) / \sqrt{2}$.
import numpy as np
from qiskit import QuantumCircuit
circuit = QuantumCircuit(1)
circuit.prepare_state([1/np.sqrt(2), 1/np.sqrt(2)], 0)
circuit.draw()
output:
┌─────────────────────────────────────┐
q_0: ┤ State Preparation(0.70711,0.70711) ├
└─────────────────────────────────────┘
Prepare from a string two qubits in the state $10\rangle$. The order of the labels is reversed with respect to qubit index. More information about labels for basis states are in Statevector.from_label()
.
import numpy as np
from qiskit import QuantumCircuit
circuit = QuantumCircuit(2)
circuit.prepare_state('01', circuit.qubits)
circuit.draw()
output:
┌─────────────────────────┐
q_0: ┤0 ├
│ State Preparation(0,1) │
q_1: ┤1 ├
└─────────────────────────┘
Initialize two qubits from an array of complex amplitudes .. codeblock:
import numpy as np
from qiskit import QuantumCircuit
circuit = QuantumCircuit(2)
circuit.prepare_state([0, 1/np.sqrt(2), 1.j/np.sqrt(2), 0], circuit.qubits)
circuit.draw()
output:
┌───────────────────────────────────────────┐
q_0: ┤0 ├
│ State Preparation(0,0.70711,0.70711j,0) │
q_1: ┤1 ├
└───────────────────────────────────────────┘
qasm
qasm(formatted=False, filename=None, encoding=None)
Return OpenQASM 2.0 string.
qasm2.dump()
and qasm2.dumps()
The preferred entry points to the OpenQASM 2 export capabilities. These match the interface for other serialisers in Qiskit.
Parameters
 formatted (bool (opens in a new tab)) – Return formatted OpenQASM 2.0 string.
 filename (str (opens in a new tab)) – Save OpenQASM 2.0 to file with name ‘filename’.
 encoding (str (opens in a new tab)) – Optionally specify the encoding to use for the output file if
filename
is specified. By default this is set to the system’s default encoding (ie whateverlocale.getpreferredencoding()
returns) and can be set to any valid codec or alias from stdlib’s codec module (opens in a new tab)
Returns
If formatted=False.
Return type
Raises
 MissingOptionalLibraryError – If pygments is not installed and
formatted
isTrue
.  QASM2ExportError – If circuit has free parameters.
 QASM2ExportError – If an operation that has no OpenQASM 2 representation is encountered.
qbit_argument_conversion
qbit_argument_conversion(qubit_representation)
Converts several qubit representations (such as indexes, range, etc.) into a list of qubits.
Parameters
qubit_representation (Object) – representation to expand
Returns
the resolved instances of the qubits.
Return type
List(Qubit)
qubit_duration
qubit_duration(*qubits)
Return the duration between the start and stop time of the first and last instructions, excluding delays, over the supplied qubits. Its time unit is self.unit
.
Parameters
*qubits (Qubit int (opens in a new tab)) – Qubits within self
to include.
Returns
Return the duration between the first start and last stop time of nondelay instructions
Return type
qubit_start_time
qubit_start_time(*qubits)
Return the start time of the first instruction, excluding delays, over the supplied qubits. Its time unit is self.unit
.
Return 0 if there are no instructions over qubits
Parameters
 *qubits (Qubit int (opens in a new tab)) – Qubits within
self
to include. Integers are allowed for qubits, indicating  self.qubits. (indices of) –
Returns
Return the start time of the first instruction, excluding delays, over the qubits
Raises
CircuitError – if self
is a notyet scheduled circuit.
Return type
qubit_stop_time
qubit_stop_time(*qubits)
Return the stop time of the last instruction, excluding delays, over the supplied qubits. Its time unit is self.unit
.
Return 0 if there are no instructions over qubits
Parameters
 *qubits (Qubit int (opens in a new tab)) – Qubits within
self
to include. Integers are allowed for qubits, indicating  self.qubits. (indices of) –
Returns
Return the stop time of the last instruction, excluding delays, over the qubits
Raises
CircuitError – if self
is a notyet scheduled circuit.
Return type
r
r(theta, phi, qubit)
Apply RGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 theta (ParameterExpression float (opens in a new tab)) – The angle of the rotation.
 phi (ParameterExpression float (opens in a new tab)) – The angle of the axis of rotation in the xy plane.
 qubit (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) to apply the gate to.
Returns
A handle to the instructions created.
Return type
rcccx
rcccx(control_qubit1, control_qubit2, control_qubit3, target_qubit)
Apply RC3XGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 control_qubit1 (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) used as the first control.
 control_qubit2 (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) used as the second control.
 control_qubit3 (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) used as the third control.
 target_qubit (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) targeted by the gate.
Returns
A handle to the instructions created.
Return type
rccx
rccx(control_qubit1, control_qubit2, target_qubit)
Apply RCCXGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 control_qubit1 (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) used as the first control.
 control_qubit2 (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) used as the second control.
 target_qubit (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) targeted by the gate.
Returns
A handle to the instructions created.
Return type
remove_final_measurements
remove_final_measurements(inplace=True)
Removes final measurements and barriers on all qubits if they are present. Deletes the classical registers that were used to store the values from these measurements that become idle as a result of this operation, and deletes classical bits that are referenced only by removed registers, or that aren’t referenced at all but have become idle as a result of this operation.
Measurements and barriers are considered final if they are followed by no other operations (aside from other measurements or barriers.)
Parameters
inplace (bool (opens in a new tab)) – All measurements removed inplace or return new circuit.
Returns
Returns the resulting circuit when inplace=False
, else None.
Return type
repeat
repeat(reps)
Repeat this circuit reps
times.
Parameters
reps (int (opens in a new tab)) – How often this circuit should be repeated.
Returns
A circuit containing reps
repetitions of this circuit.
Return type
reset
reset(qubit)
Reset the quantum bit(s) to their default state.
Parameters
qubit (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – qubit(s) to reset.
Returns
handle to the added instruction.
Return type
reverse_bits
reverse_bits()
Return a circuit with the opposite order of wires.
The circuit is “vertically” flipped. If a circuit is defined over multiple registers, the resulting circuit will have the same registers but with their order flipped.
This method is useful for converting a circuit written in littleendian convention to the bigendian equivalent, and vice versa.
Returns
the circuit with reversed bit order.
Return type
Examples
input:
┌───┐
a_0: ┤ H ├──■─────────────────
└───┘┌─┴─┐
a_1: ─────┤ X ├──■────────────
└───┘┌─┴─┐
a_2: ──────────┤ X ├──■───────
└───┘┌─┴─┐
b_0: ───────────────┤ X ├──■──
└───┘┌─┴─┐
b_1: ────────────────────┤ X ├
└───┘
output:
┌───┐
b_0: ────────────────────┤ X ├
┌───┐└─┬─┘
b_1: ───────────────┤ X ├──■──
┌───┐└─┬─┘
a_0: ──────────┤ X ├──■───────
┌───┐└─┬─┘
a_1: ─────┤ X ├──■────────────
┌───┐└─┬─┘
a_2: ┤ H ├──■─────────────────
└───┘
reverse_ops
reverse_ops()
Reverse the circuit by reversing the order of instructions.
This is done by recursively reversing all instructions. It does not invert (adjoint) any gate.
Returns
the reversed circuit.
Return type
Examples
input:
┌───┐
q_0: ┤ H ├─────■──────
└───┘┌────┴─────┐
q_1: ─────┤ RX(1.57) ├
└──────────┘
output:
┌───┐
q_0: ─────■──────┤ H ├
┌────┴─────┐└───┘
q_1: ┤ RX(1.57) ├─────
└──────────┘
rv
rv(vx, vy, vz, qubit)
Apply RVGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Rotation around an arbitrary rotation axis $v$, where $v$ is the angle of rotation in radians.
Parameters
 vx (ParameterExpression float (opens in a new tab)) – xcomponent of the rotation axis.
 vy (ParameterExpression float (opens in a new tab)) – ycomponent of the rotation axis.
 vz (ParameterExpression float (opens in a new tab)) – zcomponent of the rotation axis.
 qubit (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) to apply the gate to.
Returns
A handle to the instructions created.
Return type
rx
rx(theta, qubit, label=None)
Apply RXGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 theta (ParameterValueType) – The rotation angle of the gate.
 qubit (QubitSpecifier) – The qubit(s) to apply the gate to.
 label (str (opens in a new tab)  None) – The string label of the gate in the circuit.
Returns
A handle to the instructions created.
Return type
rxx
rxx(theta, qubit1, qubit2)
Apply RXXGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 theta (ParameterExpression float (opens in a new tab)) – The angle of the rotation.
 qubit1 (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) to apply the gate to.
 qubit2 (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) to apply the gate to.
Returns
A handle to the instructions created.
Return type
ry
ry(theta, qubit, label=None)
Apply RYGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 theta (ParameterValueType) – The rotation angle of the gate.
 qubit (QubitSpecifier) – The qubit(s) to apply the gate to.
 label (str (opens in a new tab)  None) – The string label of the gate in the circuit.
Returns
A handle to the instructions created.
Return type
ryy
ryy(theta, qubit1, qubit2)
Apply RYYGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 theta (ParameterExpression float (opens in a new tab)) – The rotation angle of the gate.
 qubit1 (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) to apply the gate to.
 qubit2 (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) to apply the gate to.
Returns
A handle to the instructions created.
Return type
rz
rz(phi, qubit)
Apply RZGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 phi (ParameterExpression float (opens in a new tab)) – The rotation angle of the gate.
 qubit (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) to apply the gate to.
Returns
A handle to the instructions created.
Return type
rzx
rzx(theta, qubit1, qubit2)
Apply RZXGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 theta (ParameterExpression float (opens in a new tab)) – The rotation angle of the gate.
 qubit1 (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) to apply the gate to.
 qubit2 (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) to apply the gate to.
Returns
A handle to the instructions created.
Return type
rzz
rzz(theta, qubit1, qubit2)
Apply RZZGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 theta (ParameterExpression float (opens in a new tab)) – The rotation angle of the gate.
 qubit1 (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) to apply the gate to.
 qubit2 (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) to apply the gate to.
Returns
A handle to the instructions created.
Return type
s
s(qubit)
Apply SGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
qubit (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) to apply the gate to.
Returns
A handle to the instructions created.
Return type
sdg
sdg(qubit)
Apply SdgGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
qubit (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) to apply the gate to.
Returns
A handle to the instructions created.
Return type
size
size(filter_function=<function QuantumCircuit.<lambda>>)
Returns total number of instructions in circuit.
Parameters
filter_function (callable) – a function to filter out some instructions. Should take as input a tuple of (Instruction, list(Qubit), list(Clbit)). By default filters out “directives”, such as barrier or snapshot.
Returns
Total number of gate operations.
Return type
snapshot
snapshot(label, snapshot_type='statevector', qubits=None, params=None)
Take a statevector snapshot of the internal simulator representation. Works on all qubits, and prevents reordering (like barrier).
For other types of snapshots use the Snapshot extension directly.
The method qiskit.circuit.quantumcircuit.QuantumCircuit.snapshot()
is deprecated as of qiskit 0.45.0. It will be removed no earlier than 3 months after the release date. The Snapshot instruction has been superseded by Qiskit Aer’s save instructions, see https://qiskit.org/ecosystem/aer/apidocs/aer_library.html#savingsimulatordata (opens in a new tab).
Parameters
 label (str (opens in a new tab)) – a snapshot label to report the result.
 snapshot_type (str (opens in a new tab)) – the type of the snapshot.
 qubits (list (opens in a new tab) or None) – the qubits to apply snapshot to [Default: None].
 params (list (opens in a new tab) or None) – the parameters for snapshot_type [Default: None].
Returns
with attached command
Return type
Raises
ExtensionError – malformed command
squ
squ(unitary_matrix, qubit, mode='ZYZ', up_to_diagonal=False)
Decompose an arbitrary 2*2 unitary into three rotation gates.
Note that the decomposition is up to a global phase shift. (This is a well known decomposition which can be found for example in Nielsen and Chuang’s book “Quantum computation and quantum information”.)
The method qiskit.circuit.quantumcircuit.QuantumCircuit.squ()
is deprecated as of qiskit 0.45.0. It will be removed no earlier than 3 months after the release date. Instead, use the QuantumCircuit.unitary method.
Parameters
 unitary_matrix (ndarray) – 2*2 unitary (given as a (complex) ndarray).
 qubit (QuantumRegister orQubit) – The qubit which the gate is acting on.
 mode (string) – determines the used decomposition by providing the rotation axes. The allowed modes are: “ZYZ” (default)
 up_to_diagonal (bool (opens in a new tab)) – if set to True, the singlequbit unitary is decomposed up to a diagonal matrix, i.e. a unitary u’ is implemented such that there exists a 2*2 diagonal gate d with u = d.dot(u’)
Returns
The singlequbit unitary instruction attached to the circuit.
Return type
Raises
QiskitError – if the format is wrong; if the array u is not unitary
swap
swap(qubit1, qubit2)
Apply SwapGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
 qubit1 (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubits to apply the gate to.
 qubit2 (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubits to apply the gate to.
Returns
A handle to the instructions created.
Return type
switch
switch
switch(target: Clbit  ClassicalRegister  int  slice  Sequence[Clbit  int], cases: None, qubits: None, clbits: None, *, label: str  None) → qiskit.circuit.controlflow.switch_case.SwitchContext
switch(target: Clbit  ClassicalRegister  int  slice  Sequence[Clbit  int], cases: Iterable[Tuple[Any, QuantumCircuit]], qubits: Sequence[Qubit  QuantumRegister  int  slice  Sequence[Qubit  int]], clbits: Sequence[Clbit  ClassicalRegister  int  slice  Sequence[Clbit  int]], *, label: str  None) → InstructionSet
Create a switch
/case
structure on this circuit.
There are two forms for calling this function. If called with all its arguments (with the possible exception of label
), it will create a SwitchCaseOp
with the given case structure. If cases
(and qubits
and clbits
) are not passed, then this acts as a context manager, which will automatically build a SwitchCaseOp
when the scope finishes. In this form, you do not need to keep track of the qubits or clbits you are using, because the scope will handle it for you.
Example usage:
from qiskit.circuit import QuantumCircuit, ClassicalRegister, QuantumRegister
qreg = QuantumRegister(3)
creg = ClassicalRegister(3)
qc = QuantumCircuit(qreg, creg)
qc.h([0, 1, 2])
qc.measure([0, 1, 2], [0, 1, 2])
with qc.switch(creg) as case:
with case(0):
qc.x(0)
with case(1, 2):
qc.z(1)
with case(case.DEFAULT):
qc.cx(0, 1)
Parameters
 target (Union[ClassicalRegister, Clbit]) – The classical value to switch one. This must be integerlike.
 cases (Iterable[Tuple[Any (opens in a new tab), QuantumCircuit]]) – A sequence of case specifiers. Each tuple defines one case body (the second item). The first item of the tuple can be either a single integer value, the special value
CASE_DEFAULT
, or a tuple of several integer values. Each of the integer values will be tried in turn; control will then pass to the body corresponding to the first match.CASE_DEFAULT
matches all possible values. Omit in contextmanager form.  qubits (Sequence[Qubit]) – The circuit qubits over which all case bodies execute. Omit in contextmanager form.
 clbits (Sequence[Clbit]) – The circuit clbits over which all case bodies execute. Omit in contextmanager form.
 label (Optional[str (opens in a new tab)]) – The string label of the instruction in the circuit.
Returns
If used in contextmanager mode, then this should be used as a with
resource, which will return an object that can be repeatedly entered to produce cases for the switch statement. If the full form is used, then this returns a handle to the instructions created.
Return type
InstructionSet or SwitchCaseContext
Raises
CircuitError – if an incorrect calling convention is used.
sx
sx(qubit)
Apply SXGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
qubit (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) to apply the gate to.
Returns
A handle to the instructions created.
Return type
sxdg
sxdg(qubit)
Apply SXdgGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
qubit (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) to apply the gate to.
Returns
A handle to the instructions created.
Return type
t
t(qubit)
Apply TGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
qubit (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) to apply the gate to.
Returns
A handle to the instructions created.
Return type
tdg
tdg(qubit)
Apply TdgGate
.
For the full matrix form of this gate, see the underlying gate documentation.
Parameters
qubit (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) to apply the gate to.
Returns
A handle to the instructions created.
Return type
tensor
tensor(other, inplace=False)
Tensor self
with other
.
Remember that in the littleendian convention the leftmost operation will be at the bottom of the circuit. See also the docs for more information.
┌────────┐ ┌─────┐ ┌─────┐
q_0: ┤ bottom ├ ⊗ q_0: ┤ top ├ = q_0: ─┤ top ├──
└────────┘ └─────┘ ┌┴─────┴─┐
q_1: ┤ bottom ├
└────────┘
Parameters
 other (QuantumCircuit) – The other circuit to tensor this circuit with.
 inplace (bool (opens in a new tab)) – If True, modify the object. Otherwise return composed circuit.
Return type
QuantumCircuit  None
Examples
from qiskit import QuantumCircuit
top = QuantumCircuit(1)
top.x(0);
bottom = QuantumCircuit(2)
bottom.cry(0.2, 0, 1);
tensored = bottom.tensor(top)
tensored.draw('mpl')
Returns
The tensored circuit (returns None if inplace==True).
Return type
to_gate
to_gate(parameter_map=None, label=None)
Create a Gate out of this circuit.
Parameters
 parameter_map (dict (opens in a new tab)) – For parameterized circuits, a mapping from parameters in the circuit to parameters to be used in the gate. If None, existing circuit parameters will also parameterize the gate.
 label (str (opens in a new tab)) – Optional gate label.
Returns
a composite gate encapsulating this circuit (can be decomposed back)
Return type
to_instruction
to_instruction(parameter_map=None, label=None)
Create an Instruction out of this circuit.
Parameters
 parameter_map (dict (opens in a new tab)) – For parameterized circuits, a mapping from parameters in the circuit to parameters to be used in the instruction. If None, existing circuit parameters will also parameterize the instruction.
 label (str (opens in a new tab)) – Optional gate label.
Returns
a composite instruction encapsulating this circuit (can be decomposed back)
Return type
toffoli
toffoli(control_qubit1, control_qubit2, target_qubit)
Apply CCXGate
.
For the full matrix form of this gate, see the underlying gate documentation.
The method qiskit.circuit.quantumcircuit.QuantumCircuit.toffoli()
is deprecated as of qiskit 0.45.0. It will be removed no earlier than 3 months after the release date. Use QuantumCircuit.ccx as direct replacement.
Parameters
 control_qubit1 (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) used as the first control.
 control_qubit2 (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) used as the second control.
 target_qubit (Qubit QuantumRegister int (opens in a new tab) slice (opens in a new tab) Sequence (opens in a new tab)[Qubit int (opens in a new tab)]) – The qubit(s) targeted by the gate.
Returns
A handle to the instructions created.
Return type
QuantumCircuit.ccx: the same gate with a different name.