# Is Y equivalent to( S X Sdg)?

I have this code here to solve " I.14 Multi-qubit gate challenge" of the codebook here .

I could not figure out why state|11> is wrong, any idea

``````dev = qml.device("default.qubit", wires=3)

# State of first 2 qubits
state = [0, 1]

@qml.qnode(device=dev)
def apply_control_sequence(state):
# Set up initial state of the first two qubits
if state[0] == 1:
qml.PauliX(wires=0)
if state[1] == 1:
qml.PauliX(wires=1)

# Set up initial state of the third qubit - use |->
# so we can see the effect on the output
qml.PauliX(wires=2)

##################
##################

# IMPLEMENT THE MULTIPLEXER
# IF STATE OF FIRST TWO QUBITS IS 01,
#APPLY X TO THIRD QUBIT
qml.PauliX(wires=0)
qml.Toffoli(wires=[0,1,2])
qml.PauliX(wires=0)

# IF STATE OF FIRST TWO QUBITS IS 10,
#APPLY Z TO THIRD QUBIT

qml.PauliX(wires=1)
qml.Toffoli(wires=[0,1,2])
qml.PauliX(wires=1)

# IF STATE OF FIRST TWO QUBITS IS 11,
#APPLY Y TO THIRD QUBIT
qml.S(2)
qml.Toffoli(wires=[0,1,2])

return qml.state()

print(apply_control_sequence(state))
``````

I got this error:

Incorrect: your circuit does not have the correct action on |11>.

Hi @Afrah, youâ€™re almost there!

Take a close look at the ordering of the gates in the last part of your code. Is it the same to apply S first or adjoint(S) first?
I hope this hint helps you!