Novel quantum gray-scale image matching

Image matching, also known as correspondence problem, can be defined as the establishment of the correspondence between two or more digital images depicting at least partly the same scene. In this paper, we propose a method for matching gray-scale images consisting of quantum information. Quantum template image is directly mapped with quantum reference image, i.e., the quantum register representing each corresponding pixel of the quantum template image is subtracted from that of the quantum reference image by running a quantum subtracter. According to the quantum measurement results, we can save the gray-scale difference and sum all the differences. Then we compare the sum with Tolerance value. If the sum is smaller than Tolerance value, then quantum image matching succeeds. Experimental simulations show that the proposed approach can distinguish any two quantum gray-scale images successfully. Compared to the schemes based on flexible representation of quantum images (FRQI), our approach based on novel enhanced quantum representation of digital images (NEQR) has the advantages of retrieving the original classical image accurately from the quantum image so that it can be generalized to the case where the dimension of quantum template image is smaller than that of quantum reference image.