# Gate

*class *`qiskit.circuit.Gate(name, num_qubits, params, label=None)`

Bases: `Instruction`

Unitary gate.

Create a new gate.

**Parameters**

**name**(*str*) – The Qobj name of the gate.**num_qubits**(*int*) – The number of qubits the gate acts on.**params**(*list*) – A list of parameters.**label**(*str**| None*) – An optional label for the gate.

## Attributes

### condition_bits

Get Clbits in condition.

### decompositions

Get the decompositions of the instruction from the SessionEquivalenceLibrary.

### definition

Return definition in terms of other basic gates.

### duration

Get the duration.

### label

Return instruction label

### name

Return the name.

### num_clbits

Return the number of clbits.

### num_qubits

Return the number of qubits.

### params

return instruction params.

### unit

Get the time unit of duration.

## Methods

### add_decomposition

`add_decomposition(decomposition)`

Add a decomposition of the instruction to the SessionEquivalenceLibrary.

### assemble

`assemble()`

Assemble a QasmQobjInstruction

### broadcast_arguments

`broadcast_arguments(qargs, cargs)`

Validation and handling of the arguments and its relationship.

For example, `cx([q[0],q[1]], q[2])`

means `cx(q[0], q[2]); cx(q[1], q[2])`

. This method yields the arguments in the right grouping. In the given example:

```
in: [[q[0],q[1]], q[2]],[]
outs: [q[0], q[2]], []
[q[1], q[2]], []
```

The general broadcasting rules are:

If len(qargs) == 1:

`[q[0], q[1]] -> [q[0]],[q[1]]`

If len(qargs) == 2:

`[[q[0], q[1]], [r[0], r[1]]] -> [q[0], r[0]], [q[1], r[1]] [[q[0]], [r[0], r[1]]] -> [q[0], r[0]], [q[0], r[1]] [[q[0], q[1]], [r[0]]] -> [q[0], r[0]], [q[1], r[0]]`

If len(qargs) >= 3:

`[q[0], q[1]], [r[0], r[1]], ...] -> [q[0], r[0], ...], [q[1], r[1], ...]`

**Parameters**

**Returns**

A tuple with single arguments.

**Raises**

**CircuitError** – If the input is not valid. For example, the number of arguments does not match the gate expectation.

**Return type**

### c_if

`c_if(classical, val)`

Set a classical equality condition on this instruction between the register or cbit `classical`

and value `val`

.

This is a setter method, not an additive one. Calling this multiple times will silently override any previously set condition; it does not stack.

### control

`control(num_ctrl_qubits=1, label=None, ctrl_state=None)`

Return controlled version of gate. See `ControlledGate`

for usage.

**Parameters**

**num_ctrl_qubits**(*int*) – number of controls to add to gate (default:`1`

)**label**(*str**| None*) – optional gate label**ctrl_state**(*int**|**str**| None*) – The control state in decimal or as a bitstring (e.g.`'111'`

). If`None`

, use`2**num_ctrl_qubits-1`

.

**Returns**

Controlled version of gate. This default algorithm uses `num_ctrl_qubits-1`

ancilla qubits so returns a gate of size `num_qubits + 2*num_ctrl_qubits - 1`

.

**Return type**

**Raises**

**QiskitError** – unrecognized mode or invalid ctrl_state

### copy

`copy(name=None)`

Copy of the instruction.

**Parameters**

**name** (*str*) – name to be given to the copied circuit, if `None`

then the name stays the same.

**Returns**

a copy of the current instruction, with the name updated if it was provided

**Return type**

### inverse

`inverse()`

Invert this instruction.

If the instruction is composite (i.e. has a definition), then its definition will be recursively inverted.

Special instructions inheriting from Instruction can implement their own inverse (e.g. T and Tdg, Barrier, etc.)

**Returns**

a fresh instruction for the inverse

**Return type**

**Raises**

**CircuitError** – if the instruction is not composite and an inverse has not been implemented for it.

### is_parameterized

`is_parameterized()`

Return True .IFF. instruction is parameterized else False

### power

`power(exponent)`

Creates a unitary gate as gate^exponent.

**Parameters**

**exponent** (*float*) – Gate^exponent

**Returns**

To which to_matrix is self.to_matrix^exponent.

**Return type**

**Raises**

**CircuitError** – If Gate is not unitary

### qasm

`qasm()`

Return a default OpenQASM string for the instruction.

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

).

The method `qiskit.circuit.instruction.Instruction.qasm()`

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

### repeat

`repeat(n)`

Creates an instruction with gate repeated n amount of times.

**Parameters**

**n** (*int*) – Number of times to repeat the instruction

**Returns**

Containing the definition.

**Return type**

**Raises**

**CircuitError** – If n < 1.

### reverse_ops

`reverse_ops()`

For a composite instruction, reverse the order of sub-instructions.

This is done by recursively reversing all sub-instructions. It does not invert any gate.

**Returns**

**a new instruction with**

sub-instructions reversed.

**Return type**

### soft_compare

`soft_compare(other)`

Soft comparison between gates. Their names, number of qubits, and classical bit numbers must match. The number of parameters must match. Each parameter is compared. If one is a ParameterExpression then it is not taken into account.

**Parameters**

**other** (*instruction*) – other instruction.

**Returns**

are self and other equal up to parameter expressions.

**Return type**

### to_matrix

`to_matrix()`

Return a Numpy.array for the gate unitary matrix.

**Returns**

if the Gate subclass has a matrix definition.

**Return type**

np.ndarray

**Raises**

**CircuitError** – If a Gate subclass does not implement this method an exception will be raised when this base class method is called.

### validate_parameter

`validate_parameter(parameter)`

Gate parameters should be int, float, or ParameterExpression