Robust semi-quantum private comparison protocols against collective noises with decoherence-free states

Utilizing the advantage of decoherence-free (DF) states, two semi-quantum private comparison (SQPC) protocols against the collective-dephasing noise and collective-rotation noise are proposed, respectively. In the protocols, two semi-quantum parties (i.e. participants with limited quantum capabilities) can compare their secrets with the help of a semi-honest third party (TP). Some common outsider’s and insider’s attacks are also discussed. Moreover, the simulations of our protocols on the IBM Quantum Experience show that our protocols are not only robust under two collective noises, but also feasible under the current quantum technology.