L
Loss
Quantum circuit
Trainable quantum layer
q0
H
RY
θ₀
q1
RZ
θ₁
RX
θ₄
q2
H
RY
θ₂
q3
RZ
θ₃
RX
θ₅
Parameters θ₀ … θ₅
Neural network
Classical learning layer
Weights W · 3 outputs
Forward · left to right
Autograd · right to left