CU3Gate

class qiskit.circuit.library.CU3Gate(theta, phi, lam, label=None, ctrl_state=None)

Bases: ControlledGate

Controlled-U3 gate (3-parameter two-qubit gate).

This is a controlled version of the U3 gate (generic single qubit rotation). It is restricted to 3 parameters, and so cannot cover generic two-qubit controlled gates).

Circuit symbol:

q_0: ──────■──────
     ┌─────┴─────┐
q_1: ┤ U3(ϴ,φ,λ) ├
     └───────────┘

Matrix representation:

\providecommand{\th}{\frac{\theta}{2}}\\\begin{split}CU3(\theta, \phi, \lambda)\ q_0, q_1 = I \otimes |0\rangle\langle 0| + U3(\theta,\phi,\lambda) \otimes |1\rangle\langle 1| = \begin{pmatrix} 1 & 0 & 0 & 0 \\ 0 & \cos(\th) & 0 & -e^{i\lambda}\sin(\th) \\ 0 & 0 & 1 & 0 \\ 0 & e^{i\phi}\sin(\th) & 0 & e^{i(\phi+\lambda)}\cos(\th) \end{pmatrix}\end{split}

Note

In Qiskit’s convention, higher qubit indices are more significant (little endian convention). In many textbooks, controlled gates are presented with the assumption of more significant qubits as control, which in our case would be q_1. Thus a textbook matrix for this gate will be:

     ┌───────────┐
q_0: ┤ U3(ϴ,φ,λ) ├
     └─────┬─────┘
q_1: ──────■──────

\begin{split}CU3(\theta, \phi, \lambda)\ q_1, q_0 = |0\rangle\langle 0| \otimes I + |1\rangle\langle 1| \otimes U3(\theta,\phi,\lambda) = \begin{pmatrix} 1 & 0 & 0 & 0 \\ 0 & 1 & 0 & 0 \\ 0 & 0 & \cos(\th) & -e^{i\lambda}\sin(\th) \\ 0 & 0 & e^{i\phi}\sin(\th) & e^{i(\phi+\lambda)}\cos(\th) \end{pmatrix}\end{split}

Create new CU3 gate.

Attributes

Get Clbits in condition.

Return the control state of the gate as a decimal integer.

Get the decompositions of the instruction from the SessionEquivalenceLibrary.

Return definition in terms of other basic gates. If the gate has open controls, as determined from self.ctrl_state, the returned definition is conjugated with X without changing the internal _definition.

Get the duration.

Return instruction label

Get name of gate. If the gate has open controls the gate name will become:

$<original_name_o<ctrl_state>$

where <original_name> is the gate name for the default case of closed control qubits and <ctrl_state> is the integer value of the control state for the gate.

Return the number of clbits.

Get number of control qubits.

Returns

The number of control qubits for the gate.

Return type

int

Return the number of qubits.

Get parameters from base_gate.

Returns

List of gate parameters.

Return type

list

Raises

CircuitError - Controlled gate does not define a base gate

Get the time unit of duration.

inverse()

Return inverted CU3 gate.

CU3(\theta,\phi,\lambda)^{\dagger} =CU3(-\theta,-\phi,-\lambda)

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