Bug: nested ctrl

PennyLane Help
1

I have a problem when I use nested qml.ctrl, indeed defining the following functions:


def fun_1(x):
   qml.ctrl(qml.RY,control=[1,2])(x,wires = 3)

def fun_2(x):
    qml.ctrl(fun_1,control=[0])(x)

Drawing the circuit yields the following:

0: ─╭●─────────┤  State
1: ─├RY(0.50)─┤  State
2: ─├RY(0.50)─┤  State
3: ─╰RY(0.50)─┤  State

While one would expect to have the following circuit

0: ─╭●─────────┤  State
1: ─├●─────────┤  State
2: ─├●─────────┤  State
3: ─╰RY(0.50)─┤  State

Am I missing something or is this a bug ?

2

Hey @alicewithoutbob! Welcome back to the forum :smiley:

I can’t seem to replicate your error :thinking:… I get the proper drawing:

import pennylane as qml

def fun_1(x):
   qml.ctrl(qml.RY,control=[1,2])(x,wires = 3)

def fun_2(x):
    qml.ctrl(fun_1,control=[0])(x)

dev = qml.device("default.qubit", wires=4)

@qml.qnode(dev)
def circuit():
    fun_2(0.5)
    return qml.state()

print(qml.draw(circuit)())

'''
0: ─╭●────────┤  State
1: ─├●────────┤  State
2: ─├●────────┤  State
3: ─╰RY(0.50)─┤  State
'''

Are you using the most up-to-date version of PennyLane? You can check by printing qml.__version__ — it should be 0.29.1 for the latest version. If it’s anything less than that, you can update it via pip install --upgrade pennylane. Let me know if that helps!