In Ref. (Int. J. Theor. Phys. 57, 2575–2584, 2018), Lu et al. developed a quantum adder algorithm that executes a quantum circuit to perform the addition operation on numbers provided through a given uniform superposition state. However, by applying the detailed steps and the elementary gates of the quantum circuit of their claimed algorithm to the identical case that was discussed in the same reference, significant mistakes are revealed. These errors, in turn, prove that the algorithm and its quantum circuit are unable to solve the problem statement as assumed in this reference. Furthermore, the quantum adder algorithm introduced by Lu et al. has been employed in various quantum algorithms (Jiang et al., Int. J. Theor. Phys. 58, 979–991, 2019; Jiang et al., Int. J. Theor. Phys. 59, 3533–3548 2020; Dai et al., Quantum Inf. Process. 20, 1–24, 2021; Li et al., Int. J. Theor. Phys. 60, 2037–2048 2021; Wang et al., Entropy 25, 1629 2023; Wang et al., Multimed. Tools Appl. 83, 79715–79739 2024; Tan et al., Int. J. Theor. Phys. 60, 1090–1102 2021). This could indicate widespread error propagation, which should be emphasized to prevent the development of more inaccurate quantum algorithms.
