CSwapGate¶

class
CSwapGate
(label=None, ctrl_state=None)[Quellcode]¶ Bases:
qiskit.circuit.controlledgate.ControlledGate
ControlledSWAP gate, also known as the Fredkin gate.
Circuit symbol:
q_0: ─X─ │ q_1: ─X─ │ q_2: ─■─
Matrix representation:
\[\begin{split}CSWAP\ q_0, q_1, q_2 = 0 \rangle \langle 0 \otimes I \otimes I + 1 \rangle \langle 1 \otimes SWAP = \begin{pmatrix} 1 & 0 & 0 & 0 & 0 & 0 & 0 & 0 \\ 0 & 1 & 0 & 0 & 0 & 0 & 0 & 0 \\ 0 & 0 & 1 & 0 & 0 & 0 & 0 & 0 \\ 0 & 0 & 0 & 0 & 0 & 1 & 0 & 0 \\ 0 & 0 & 0 & 0 & 1 & 0 & 0 & 0 \\ 0 & 0 & 0 & 1 & 0 & 0 & 0 & 0 \\ 0 & 0 & 0 & 0 & 0 & 0 & 1 & 0 \\ 0 & 0 & 0 & 0 & 0 & 0 & 0 & 1 \\ \end{pmatrix}\end{split}\]Bemerkung
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_2. Thus a textbook matrix for this gate will be:
q_0: ─■─ │ q_1: ─X─ │ q_2: ─X─
\[\begin{split}CSWAP\ q_2, q_1, q_0 = 0 \rangle \langle 0 \otimes I \otimes I + 1 \rangle \langle 1 \otimes SWAP = \begin{pmatrix} 1 & 0 & 0 & 0 & 0 & 0 & 0 & 0 \\ 0 & 1 & 0 & 0 & 0 & 0 & 0 & 0 \\ 0 & 0 & 1 & 0 & 0 & 0 & 0 & 0 \\ 0 & 0 & 0 & 1 & 0 & 0 & 0 & 0 \\ 0 & 0 & 0 & 0 & 1 & 0 & 0 & 0 \\ 0 & 0 & 0 & 0 & 0 & 0 & 1 & 0 \\ 0 & 0 & 0 & 0 & 0 & 1 & 0 & 0 \\ 0 & 0 & 0 & 0 & 0 & 0 & 0 & 1 \\ \end{pmatrix}\end{split}\]In the computational basis, this gate swaps the states of the two target qubits if the control qubit is in the \(1\rangle\) state.
\[0, b, c\rangle \rightarrow 0, b, c\rangle 1, b, c\rangle \rightarrow 1, c, b\rangle\]Create new CSWAP gate.
Methods Defined Here
Return inverse CSwap gate (itself).
Attributes

ctrl_state
¶ Return the control state of the gate as a decimal integer.
 Rückgabetyp
int

decompositions
¶ Get the decompositions of the instruction from the SessionEquivalenceLibrary.

definition
¶ 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.
 Rückgabetyp
List

duration
¶ Get the duration.

label
¶ Return instruction label
 Rückgabetyp
str

name
¶ 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.
 Rückgabetyp
str

num_ctrl_qubits
¶ Get number of control qubits.
 Rückgabe
The number of control qubits for the gate.
 Rückgabetyp
int

params
¶ Get parameters from base_gate.
 Rückgabe
List of gate parameters.
 Rückgabetyp
list
 Verursacht
CircuitError – Controlled gate does not define a base gate

unit
¶ Get the time unit of duration.
