Dear Dr. Vivek Verma,

You may want to look over following useful information presented below:

The NPCR (Normalized Pixel Change Rate) and UACI (Unified Average Changing Intensity) tests are commonly used to evaluate the quality and security of image encryption techniques. These tests are designed to measure how much the encrypted image changes when a single pixel is altered in the original image. High NPCR and low UACI values indicate good security and encryption quality.

It's important to note that achieving high NPCR and low UACI values in quantum image encryption, or any encryption method, is not solely dependent on the choice of gates (like CNOT or CCNOT) or chaotic maps used for diffusion. There are several factors that can affect the results of these tests, and getting the desired NPCR and UACI values often requires careful consideration of various parameters and aspects of your encryption scheme. Here are some factors to consider:

It's also important to remember that high NPCR and low UACI values are not the sole indicators of a secure encryption scheme. Other aspects of security, such as resistance to known attacks and robustness against various cryptographic analyses, should also be considered.

Ultimately, achieving the desired NPCR and UACI values requires a comprehensive approach to designing and implementing your quantum image encryption scheme, with attention to all the factors mentioned above. It may also involve making iterative improvements and optimizations to your technique. If the results are still not satisfactory, it's worth consulting with experts in quantum image encryption or cryptography for guidance and potential improvements.

Dear Sir, Thank you for your reply. I have tested the encrypted image with all the tests like information entropy, SSIM, correlation analysis, NIST test, Histogram, and Chi-square test and they all gave me better results compared to the existing quantum image encryption algorithms but the NPCR and UACI tests failed. Sir, because of fewer resources in quantum, we ultimately used quantum XOR for diffusion purposes using the CNOT gate or CCNOT gate. Many researchers mentioned the good results of NPCR and UACI, but I can't understand how they got good results from only quantum XOR. Please explain Sir.

Does anyone know how we can simulate the Quantum CCNOT gate and CNOT gate on MATLAB how can we apply it to the two images in which one image pixel is the control and another pixel is the target qubit? I am trying to code but am not getting the correct result.