Figure 1

Variational quantum circuit component. The single-qubit gates \(R_y(\arctan (x_i))\) and \(R_z(\arctan (x_i^2))\) represent rotations along the y- and z-axis by the given angle \(\arctan (x_i)\) and \(\arctan (x_i^2)\), respectively. Arctan is used because the input values are not in the interval of \([-1, 1]\). The CNOT gates are used to entangle quantum states from each qubit and \(R(\alpha ,\beta ,\gamma )\) represents the general single qubit unitary gate with three parameters. The parameters labeled \(R_y(\arctan (x_i))\) and \(R_y(\arctan (x_i^2))\) are for state preparation and are not subject to iterative optimization. Parameters labeled \(\alpha _i\), \(\beta _i\) and \(\gamma _i\) are optimized iteratively. The dashed box denotes one layer of a quantum subcircuit. The dial to the far right represents that the circuit has one output that is the \(\sigma _z\) measurement of the first qubit.