Quantum image encryption is an emerging technology for efficiently protecting visual information. A quantum block image encryption scheme is designed based on quantum Arnold transform (QArT) and lately proposed sine chaotification model (SCM) in this paper. First, in order to flexibly manipulate image blocks, a quantum block image representation (QBIR) model for block image is proposed, which encodes pixel gray values and position information of image blocks into two entangled qubit sequences. Then, QArT is applied to scramble the positions of image blocks. The final ciphertext image is obtained by quantum xor operations, which is completed with a pseudorandom sequence generated from SCM. The introduction of SCM dramatically enlarges the key space to resist brute-force attack. Moreover, the generated sequence is dependent on the original image to resist the chosen-plaintext attack. The main quantum circuits are given and the numerical simulation results demonstrate that the proposed quantum image encryption scheme is valid and reliable for quantum image protection in terms of security and computational complexity. INDEX TERMS Quantum image representation, quantum image encryption, quantum Arnold transform, sine chaotification model, XOR operation. XINGBIN LIU received the Ph.D. degree from the School of Information and Electronics, Beijing Institute of Technology, in 2017. He is currently a Postdoctoral Researcher with the College of Computer Science, Chongqing University. His main research interests include image security, image fusion, and quantum information processing.

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Quantum image encryption offers major advantages over its classical counterpart in terms of key space, computational complexity, and so on. A novel double quantum image encryption approach based on quantum Arnold transform (QAT) and qubit random rotation is proposed in this paper, in which QAT is used to scramble pixel positions and the gray information is changed by utilizing random qubit rotation. Actually, the independent random qubit rotation operates once, respectively, in spatial and frequency domains with the help of quantum Fourier transform (QFT). The encryption process accomplishes pixel confusion and diffusion, and finally the noise-like cipher image is obtained. Numerical simulation and theoretical analysis verify that the method is valid and it shows superior performance in security and computational complexity.

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