Privacy-preserving computational geometry is the research area on the
intersection of the domains of secure multi-party computation (SMC) and
computational geometry. As an important field, the privacy-preserving geometric
intersection (PGI) problem is when each of the multiple parties has a private
geometric graph and seeks to determine whether their graphs intersect or not
without revealing their private information. In this study, through
representing Alice's (Bob's) private geometric graph G_A (G_B) as the set of
numbered grids S_A (S_B), an efficient privacy-preserving quantum two-party
geometric intersection (PQGI) protocol is proposed. In the protocol, the oracle
operation O_A (O_B) is firstly utilized to encode the private elements of
S_A=(a_0, a_1, ..., a_(M-1)) (S_B=(b_0, b_1, ..., b_(N-1))) into the quantum
states, and then the oracle operation O_f is applied to obtain a new quantum
state which includes the XOR results between each element of S_A and S_B.
Finally, the quantum counting is introduced to get the amount (t) of the states
|a_i+b_j> equaling to |0>, and the intersection result can be obtained by
judging t>0 or not. Compared with classical PGI protocols, our proposed
protocol not only has higher security, but also holds lower communication
complexity