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In this paper, we numerically study quantum walks on two kinds of two-dimensional graphs: cylindrical strip and Mobius strip. The two kinds of graphs are typical two-dimensional topological graph. We study the crossing property of quantum walks on these two models. Also, we study its dependence on the initial state, size of the model. At the same time, we compare the quantum walk and classical walk on these two models to discuss the difference of quantum walk and classical walk. [ABSTRACT FROM AUTHOR]

We propose a secure quantum protocol for comparing the equality of information with the help of a semi-honest third party (Trent). Our protocol utilizes the triplet W states, and the single-particle measurement. The technique for preparing W state is mature, which ensures the utility of our protocol. The security of our protocol with respect to both outsider attack and participant attack is discussed. Any information about the private information, the comparison result will not be leaked out, even the third party cannot know these information. [ABSTRACT FROM AUTHOR]

We have recently proposed the two-particle controlled interacting quantum walks for building quantum Hash schemes (Li et al. Quantum Inf Proc, . doi:). In this paper, we adopt the mutual information, the measurement-induced disturbance and the quantum mutual information to measure the classical correlation, the quantum correlation and the total correlation between two particles respectively. Our conclusion is that the correlation between the particles of the two-particle controlled interacting quantum walks is similar to that of the two-particle interacting quantum walks. It is superb for keeping the quantum Hash scheme safe. [ABSTRACT FROM AUTHOR]

Recently, a quantum private comparison (QPC) protocol with a dishonest third party (TP) (Yang et al. in Quantum Inf Process, 2012. doi:) was proposed, which pointed out that the assumption of semi-honest third party (TP) is unreasonable. Here we find this protocol is not so secure as it was expected, and then we give some improvement strategies, which ensure that both players' secrets will not be leaked to anyone. We also discuss the assumption for TP in QPC protocls, which gives a constructive suggestions for the design of a new QPC protocol. [ABSTRACT FROM AUTHOR]

Quantum watermarking is the technique which embeds the invisible quantum signal such as the owner's identification into quantum multimedia data (such as audio, video and image) for copyright protection. In this paper, a watermark strategy for quantum images is proposed based on flexible representation for quantum images (FRQI). Compared with the former strategy, which can only be used to verify the identity of the true owner of a carrier image, the proposed method can be used to find out who is the real owner, and our strategy's capacity reaches the largest. It is impossible for anyone except the copyrighter to clear off or extract the watermark images. [ABSTRACT FROM AUTHOR]

Two efficient quantum private comparison (QPC) protocols are proposed, employing single photons and collective detection. In the proposed protocols, two distrustful parties (Alice and Bob) compare the equivalence of information with the help of a semi-honest third party (TP). Utilizing collective detection, the cost of practical realization is reduced greatly. In the first protocol, TP gains the result of the comparison. While in the second protocol, TP cannot get the comparison result. In both of our protocols, Alice and Bob only need be equipped with unitary operation machines, such as phase plates. So Alice and Bob need not to have the expensive quantum devices, such as qubit generating machine, quantum memory machine and quantum measuring machine. Security of the protocols is ensured by theorems on quantum operation discrimination. [ABSTRACT FROM AUTHOR]

Recently a quantum steganographic communication protocol based on quantum key distribution (QKD) was proposed, where it is believed that QKD is a kind of suitable cover of a steganographic communication because QKD itself is not deterministic communication. Here we find that, as a special cryptographic application, the procedure of QKD can be used for deterministic secure communication, and consequently it is not suitable for steganography. Due to similar reasons, other quantum cryptographic schemes, including quantum secret sharing and quantum secure direct communication, are not suitable for steganography either. [ABSTRACT FROM AUTHOR]