Fig. 2
From: Barren plateaus in quantum neural network training landscapes
Structure of quantum circuits. a The generic subunit of circuits we study in this work, with a parameterized component Ul(θl) and non-parameterized unit Wl for each layer l. b Example schematic of the 1D random circuits used in our numerical experiments. The circuit begins with \(R_Y\left( {\frac{\pi }{4}} \right)\) gates applied to all qubits followed by a specified number of layers of randomly chosen Pauli rotations applied to each qubit and then a 1D ladder of controlled Z gates. The initial \(R_Y\left( {\frac{\pi }{4}} \right)\) gates are not repeated in each layer. The indices i and j in θi,j index the layer and qubit, respectively. For each layer and qub it Pi,j∈{X, Y, Z} and θi,j∈[0,2π) are sampled independently
