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Here it is explained how to define a custom non-parametric gate in Qiskit. How do I define a new parametric gate?

For example, I want to have the $CCR_y$ gate defined as

enter image description here

in order to use it as

qc.ccry(theta, c1, c2, targ)

Is this possible?

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    $\begingroup$ Does this answer your question? Custom gates on IBM Q $\endgroup$ Commented Aug 13, 2020 at 7:25
  • $\begingroup$ But the gate created there is not parametric. $\endgroup$
    – mavzolej
    Commented Aug 13, 2020 at 12:42
  • $\begingroup$ Also, the link to the tutorial is not working. $\endgroup$
    – mavzolej
    Commented Aug 13, 2020 at 12:43

1 Answer 1

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Although it might not be exactly what you are looking for, you can still use the method you would to create the non-parametric custom gate. You would just encapsulate it into a function that takes in the parameter and creates the custom gate:

def add_ccry(theta):
    qc = QuantumCircuit(3)
    qc.cry(theta/2, 1, 2)
    qc.cx(0, 1)
    qc.cry(-theta/2, 1, 2)
    qc.cx(0, 1)
    qc.cry(theta/2, 0, 2)
    gate = qc.to_gate()
    return gate

qc = QuantumCircuit(3, 3)
qc.append(add_ccry(np.pi), [0, 1, 2]) # As an example. Theta will be numpy.pi
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  • $\begingroup$ Thanks! This does the job. $\endgroup$
    – mavzolej
    Commented Aug 13, 2020 at 15:29

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