A dynamic watermarking protocol for quantum images

A universal watermarking protocol for quantum images is designed in this paper. The protocol is developed based on quantum transform (QT) and quantum add operation (QAO). Moreover, a dynamic vector is introduced to control the embedding strength in the embedding process, which is obtained through the constraint that quantum image state should keep normalized in the entire computation process. Therefore, the dynamic vector is an optimal solution of an optimization equation, which makes the watermarked image with better visual quality. Compared with the other protocols or schemes, the proposed one can improve watermarking performance of visual quality and capacity. Experiments based on flexible representation of quantum image (FRQI) and Quantum Fourier transform (QFT) illustrate the superior effectiveness of the proposed protocol.