Chen Han-Wu

Efficient Quantum Secure Direct Communication with Authentication

Two protocols of quantum direct communication with authentication [Phys. Rev. A 73 (2006) 042305] were recently indicated to be insecure against the authenticator Trent attacks [Phys. Rev. A 75 (2007) 026301]. We present two efficient protocols by using four Pauli operations, which are secure against inner Trent attacks as well as outer Eve attacks. Finally we generalize them to multiparty quantum direction communication.

An efficient deterministic secure quantum communication scheme based on cluster states and identity authentication

A novel efficient deterministic secure quantum communication scheme based on four-qubit cluster states and single-photon identity authentication is proposed. In this scheme, the two authenticated users can transmit two bits of classical information per cluster state, and its efficiency of the quantum communication is 1/3, which is approximately 1.67 times that of the previous protocol presented by Wang et al [Chin. Phys. Lett. 23 (2006) 2658]. Security analysis shows the present scheme is secure against intercept-resend attack and the impersonators attack. Furthermore, it is more economic with present-day techniques and easily processed by a one-way quantum computer.

Comment on “Improvement of Controlled Bidirectional Quantum Direct Communication Using a GHZ State" [Chin. Phys. Lett. 30 (2013) 040305]

The problem of definite information leakage existing in the controlled bidirectional quantum direct communication protocol using GHZ states [Chin. Phys. Lett. 23 (2006) 1680] was pointed out by Ye and Jiang [Chin. Phys. Lett. 30 (2013) 040305]. Then, they proposed two strategies to improve this security bug. However, if the revised versions are analyzed from the viewpoint of information theory, it can be found that they still have the problem of information leakage. That is, three quarters and one half of the information interchanged by the communication parties are leaked out unknowingly in the first and second revised protocols, respectively.

Fault detection for single and multiple missing-gate faults in reversible circuits

To ensure the validity and reliability of reversible circuits, fault detection is necessarily. Two methods to get complete test set with respect to missing-gate fault (MGF) in reversible circuits were introduced. They are the method that divided the circuit into subcircuit to get the complete test set which is not minimal and the set covering method to get the minimal complete test set. Comparing to DFT detection method, the methods introduced in this paper do not need additional gates; they do not change the structure of the circuits and do not depend on implement technologies. So, it can be widely applied.

Comment on “A Quantum Network System of QSS-QDC Using χ-Type Entangled States" [Chin. Phys. Lett. 29 (2012) 050303]

Two quantum secret sharing (QSS) protocols in a multiuser quantum direct communication (QDC) network system were put forward by Hong et al. [Chin. Phys. Lett. 29 (2012) 050303]. However, we find that either agent (Bob or Charlie) alone can obtain half the information about the senders secret without collaboration with the other, which does not satisfy the security requirement of QSS. Moreover, the secret message sent by Alice in the second protocol can be eavesdropped on or its communication can be disturbed by the builder of quantum channels (Trent).

Constructions of asymmetric quantum stabilizer codes based on classical Goppa codes

Since Calderbank et al. established CRSS construction, which constructs quantum error-correcting codes (QECC) from classical error-correcting codes, many QECC demonstrating good performance have been constructed from classical error-correcting codes; these codes are referred to as quantum stabilizer codes. Recent physical experiments indicate that the probabilities of occurrence of qubit- ip errors are much less than those of phase- ip errors in most quantum mechanical systems. Error-correcting codes thus constructed are referred to as asymmetric quantum codes. In this paper, series of asymmetric quantum stabilizer codes are constructed using nested Goppa codes and dual contained Goppa codes. In the construction of asymmetric quantum codes based on nested Goppa codes, the choice of Goppa codes is limited to construct codes with analysis methods. In normal circumstances, the construction is executed with the help of mathematical software Matlab, which is used to compute the minimum distance of Goppa codes. In the construction of asymmetric quantum codes based on dual contained Goppa codes, the error correction ability of the codes constructed in this paper is re ected in the correction of Z-type errors

Generate Seed Generators for Quantum Stabilizer Codes

Stabilizer is a very important description method of quantum error-correcting code. Before to generate quantum codes based on the stabilizer it needs to generate seed generator. The problem of finding seed generators is transformed into the problems of determining linear independence or linear dependence of vectors and finding the solutions of equations; we also present quick determinant method, sort and find method and solve equations method to verify the validity of the operator; we present the total number of seed generators of the stabilizer code. The method introduced in this paper can be applied to the quantum stabilizer code contains both type 1 and type 2 generator; and also can be applied to the quantum stabilizer code contains only type 1 generators. Through standardize the generator of the stabilizer and the seed generators at the same time; it can quickly get the quantum encoding circuit. It also presented the number of 2-qubit gates and 1-qubit gates needed for the encoding circuit.