The former constraint determines the number of hydrogen atoms, whereas the latter ensures that at most, one hydrogen atom is attached to one oxygen atom. For the purpose of this study, Fixstars Amplify AE 42 was used as the Ising machine. A single solution for bit string 𝐪 * that minimizes the FM model defined by Eq. ( ) was selected using the Fixstars Amplify AE. If the selected 𝐪 * was already included in the training data, then the bit string was randomly generated under the constraints of Eqs. ( ) and (3). Finally, in step four, DFT relaxation calculations were conducted using the initial proton configuration expressed by the selected 𝐪 * , and the total energy was obtained. The number of training data points was increased to 𝑀 + 1. Steps 2-4 were subsequently repeated as desired.