A new quantum watermark algorithm is presented by combining maximum pixel difference partitioning with the least significant bit substitution strategy. A quantum cover image with the novel enhanced quantum image representation is divided into non-overlapping blocks. And the difference between the maximal and the minimal pixel values in a block is calculated and compared with the predefined threshold. Then the current block is defined as an edge block or a smooth block according to the comparison result. Subsequently, an edge block could be embedded into more secret information than a smooth block due to the visual characteristic of human eyes. To enhance the security of the quantum watermark algorithm, the chaos matrix obtained by tent map is utilized in the scrambling and embedding process. The scrambled quantum watermark image is embedded into a quantum carrier image with the least significant bit substitution strategy. Quantum circuit analyses demonstrate that the complexity of embedding process is O(n²). Compared with other quantum watermark schemes, the proposed quantum watermark algorithm based on maximum pixel difference and tent map could achieve a better visual quality and a higher embedding capacity.

提出了一种新的量子水印算法，将最大像素差划分与最低有效位替换策略相结合。具有新颖增强量子图像表示的量子覆盖图像被划分为不重叠的块。并且计算块中最大和最小像素值之间的差值并与预定义阈值进行比较。然后根据比较结果将当前块定义为边缘块或平滑块。随后，由于人眼的视觉特性，边缘块可以嵌入比平滑块更多的秘密信息。为了增强量子水印算法的安全性，在加扰和嵌入过程中利用了帐篷图得到的混沌矩阵。将加扰后的量子水印图像嵌入到具有最低有效位替换策略的量子载体图像中。量子电路分析表明嵌入过程的复杂性是○ ( n ² )。与其他量子水印方案相比，所提出的基于最大像素差和帐篷图的量子水印算法可以获得更好的视觉质量和更高的嵌入能力。