Zhiqiang Li

Quantum secure direct communication with optimal quantum superdense coding by using general four-qubit states

From the perspective of quantum circuit, a construction framework and a measurement framework of a general kind of four-qubit states are sketched, respectively. By utilizing the properties of this kind of states, a quantum secure direct communication (QSDC) protocol is put forward, which adopts the idea of optimal quantum superdense coding to achieve a maximal efficiency and high resources capacity. The security of the proposed protocol is discussed in detail and it is proved to be secure theoretically. Moreover, the sufficient and necessary condition of which multipartite states are suitable for optimal quantum superdense coding in quantum secure direct communication is figured out.

Deterministic secure quantum communication without unitary operation based on high-dimensional entanglement swapping

By analysis of the basic properties of entanglement swapping of high-dimensional Bell states, a universal and general deterministic secure quantum communication (DSQC) protocol is proposed, in which unitary operation is not required. By making use of the results of high-dimensional Bell measurement, the sender and the receiver can encode and decode the message respectively by performing the modular addition and subtraction. Two mutually complementary bases are constructed; and according to the property of mutual complement, a method for checking security of the high-dimensional quantum channel is put forward. Some common attack strategies are analyzed, and the corresponding error rates are calculated. Then the upper bound of the threshold of error rate is deduced.

ANALYZING AND REVISING A TWO-WAY PROTOCOL FOR QUANTUM CRYPTOGRAPHY WITH A NONMAXIMALLY ENTANGLED QUBIT PAIR

The security of the second (STF-B) protocol of quantum cryptography proposed by Shimizu, Tamaki and Fukasaka (STF) [Phys. Rev. A80 (2009) 022323] is analyzed in a general way, which shows that the STF-B protocol is vulnerable under a kind of generalized attack. Sufficient and necessary condition for which Eve can successfully attack the message M without introducing errors is deduced. It shows that the correlation-elicitation (CE) attack strategy found by Qin et al. [Phys. Rev. A82 (2010) 036301] is a special case of the sufficient and necessary condition. Next, we advance an effective and efficient strategy to prevent the general attack. Hence, the STF-B protocol is revised to a secure one by improving the control mode.

Fast algorithm for 4-qubit reversible logic circuits synthesis

Owing to the exponential nature of the memory or run-tune complexity, many existing methods can only synthesize 3-qubit circuits, however, (G.W. Yang et al., 2005) can achieve 12 steps for the CNP (controlled-Not gate, NOT gate and Peres gate) library in 4-qubit circuit synthesis with mini-length by using an enhanced bi-directional synthesis approach. We mainly absorb the ideas of our 3-qubit synthesis algorithms based on hash table and present a novel and efficient algorithm which can construct almost all optimal 4-qubit reversible logic circuits with various types of gates and mini-length cost based on constructing the shortest coding and the specific topological compression, whose lossless compression ratios of the space of n-qubit circuits is near 2timesn!. Our algorithm has created all 3120218828 optimal 4-qubit circuits whose length is less than 9 for the CNT (Toffoli gate) library, and it can quickly achieve 16 steps through cascading created circuits. To the best of our knowledge, there are no other algorithms to achieve the contribution.

High-dimensional deterministic multiparty quantum secret sharing without unitary operations

A deterministic multiparty quantum secret sharing scheme is put forward, in which Bell states in high-dimensional Hilbert space are used. Only by preforming High-dimensional Bell measurements, all agents can recover the secret according to the dealer’s announcement when collaborating with each other. It shows that unitary operation for encoding deterministic secret is unnecessary in quantum communication. The security of the transmission of the high-dimensional Bell states can be ensured by randomly using one of the two mutually unbiased bases for eavesdropping checking, and thus by which the proposed quantum secret sharing scheme is secure against usual attacks. In addition, the proposed scheme has three advantages: generality, high resource capacity and high security.

Efficient Algorithms for Optimal 4-Bit Reversible Logic System Synthesis

Owing to the exponential nature of the memory and run-time complexity, many methods can only synthesize 3-bit reversible circuits and cannot synthesize 4-bit reversible circuits well. We mainly absorb the ideas of our 3-bit synthesis algorithms based on hash table and present the efficient algorithms which can construct almost all optimal 4-bit reversible logic circuits with many types of gates and at mini-length cost based on constructing the shortest coding and the specific topological compression; thus, the lossless compression ratio of the space of -bit circuits reaches near . This paper presents the first work to create all 3120218828 optimal 4-bit reversible circuits with up to 8 gates for the CNT (Controlled-NOT gate, NOT gate, and Toffoli gate) library, and it can quickly achieve 16 steps through specific cascading created circuits.

Efficient Many-to-One and One-to-Many Multiparty Quantum Secure Direct Dommunication with Authentication

In the multiparty communication, there are two types of Communication modes: the many-to-one mode and the one-to-many mode. In this paper, two efficient authenticated multiparty quantum secure direct communication protocols are presented by using GHZ states and dense coding, one is used for the many-to-one communication, and the other is suitable to the one-to-many communication. Analysis shows these protocols are secure against outer Evepsilas attacks and inner anticipators attacks (including Trents attacks), and show more efficiency on message transmission and the repeated use of secrete identity.

A Synthesis Algorithm for 4-Bit Reversible Logic Circuits with Minimum Quantum Cost

This article presents an algorithm which can quickly find the exact minimum solution to almost all of 4-bit reversible functions. We assume minimization of quantum cost (MQC). This algorithm is designed in the most memory-efficient way, or it will quickly run out of memory. Therefore, we construct the shortest coding of permutations, the topological compression and flexible data structures for the memory savings. First, hash tables are used for all 8-gate 4-bit circuits with the minimization of gate count (MGC) by using the GT library (with NOT, CNOT, Toffoli and Toffoli-4 gates). Second, we merge and split the hash tables, thus generating a single longer hash table for high-performance. Third, we synthesize these circuits with MQC by using the GTP library (with GT, Peres, and Inverted Peres gates) based on the hash table. Finally, according to the comparison of the QC of circuits, the algorithm can quickly converge for any 4-bit reversible circuit with MQC. By synthesizing all benchmark functions, in comparison with Szyprowski and Kerntopf [2011], the running time and QC are reduced up to 99.95% and 18.2%, respectively.

Effective Hash-Based Algorithm for Reversible Logic Circuits Synthesis with Minimum Cost

We present an effective algorithm which can construct optimal 3-qubit reversible logic circuits for any given reversible logic gates and costs by constructing a minimal perfect hash function. We also present an algorithm which can automatically construct quantum gate library. In the experiments on 3-qubit synthesis, our algorithm synthesizes all optimal reversible circuits with extremely fast speed--the average speed which synthesizes circuits with minimum cost is 365 times faster than that of best result.

Authenticated Quantum Secure Direct Communication with Qutrits

In this paper, a novel authenticated quantum secure direct communication scheme with three-dimension single photons is presented, where the message is encoded on batches of qutrits, and identity is mutual authenticated with their shared seed key. Security analysis shows that this scheme can efficiently resist Eves attacks and the impersonators attacks. Comparing with those protocols using entangled state, the presented scheme is more practical and economic within the present technology.