  Recently, Liu and Yin (Int. J. Theor. Phys. 60, 2074-2083 (2021)) proposed a
two-party private set intersection protocol based on quantum Fourier transform.
We find the participant can deduce the other party's private information, which
violates the security requirement of private set computation. In order to solve
this problem, an improved private set intersection protocol based on Hadamard
gate is proposed. Firstly, the more feasible Hadamard gates are used to perform
on the original n qubits instead of the quantum Fourier transform, which may
reduce the difficulty of implementation. In addition, through the exclusive OR
calculation, the participant's private information is randomly chosen and
encoded on the additional n qubits, which prevents participants from obtaining
the result of the difference set S-diff , and then avoids the internal leakage
of private information. Finally, the correctness and security analysis are
conducted to show the proposed protocol can guarantee the correctness of
computation result as well as resist outside attacks and participant internal
attacks.
