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# U1Gate

class qiskit.circuit.library.U1Gate(theta, label=None, *, duration=None, unit='dt')

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Bases: Gate

Single-qubit rotation about the Z axis.

This is a diagonal gate. It can be implemented virtually in hardware via framechanges (i.e. at zero error and duration).

Warning

This gate is deprecated. Instead, the following replacements should be used

$U1(\lambda) = P(\lambda)= U(0,0,\lambda)$
circuit = QuantumCircuit(1)
circuit.p(lambda, 0) # or circuit.u(0, 0, lambda)

Circuit symbol:

     ┌───────┐
q_0: ┤ U1(λ) ├
└───────┘

Matrix Representation:

$U1(\lambda) = \begin{pmatrix} 1 & 0 \\ 0 & e^{i\lambda} \end{pmatrix}$

Examples:

$U1(\lambda = \pi) = Z$ $U1(\lambda = \pi/2) = S$ $U1(\lambda = \pi/4) = T$

RZGate: This gate is equivalent to RZ up to a phase factor.

$U1(\lambda) = e^{i{\lambda}/2} RZ(\lambda)$

U3Gate: U3 is a generalization of U2 that covers all single-qubit rotations, using two X90 pulses.

Reference for virtual Z gate implementation: 1612.00858(opens in a new tab)

Create new U1 gate.

## Attributes

### base_class

Get the base class of this instruction. This is guaranteed to be in the inheritance tree of self.

The “base class” of an instruction is the lowest class in its inheritance tree that the object should be considered entirely compatible with for _all_ circuit applications. This typically means that the subclass is defined purely to offer some sort of programmer convenience over the base class, and the base class is the “true” class for a behavioural perspective. In particular, you should not override base_class if you are defining a custom version of an instruction that will be implemented differently by hardware, such as an alternative measurement strategy, or a version of a parametrised gate with a particular set of parameters for the purposes of distinguishing it in a Target from the full parametrised gate.

This is often exactly equivalent to type(obj), except in the case of singleton instances of standard-library instructions. These singleton instances are special subclasses of their base class, and this property will return that base. For example:

>>> isinstance(XGate(), XGate)
True
>>> type(XGate()) is XGate
False
>>> XGate().base_class is XGate
True

In general, you should not rely on the precise class of an instruction; within a given circuit, it is expected that Instruction.name should be a more suitable discriminator in most situations.

### condition

The classical condition on the instruction.

### condition_bits

Get Clbits in condition.

### decompositions

Get the decompositions of the instruction from the SessionEquivalenceLibrary.

### definition

Return definition in terms of other basic gates.

### duration

Get the duration.

### label

Return instruction label

### mutable

Is this instance is a mutable unique instance or not.

If this attribute is False the gate instance is a shared singleton and is not mutable.

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

### control

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

Return a (multi-)controlled-U1 gate.

Parameters

Returns

controlled version of this gate.

Return type

ControlledGate

### inverse

inverse()

Return inverted U1 gate ($U1(\lambda)^{\dagger} = U1(-\lambda)$)