Dynamic Event-Triggered Consensus Control for Input Constrained Multi-Agent Systems With a Designable Minimum Inter-Event Time

This paper investigates the consensus control of multi-agent systems(MASs) with constrained input using the dynamic event-triggered mechanism(ETM).Consider the MASs with small-scale networks where a centralized dynamic ETM with global information of the MASs is first designed.Then,a distributed dynamic ETM which only uses local information is developed for the MASs with large-scale networks.It is shown that the semi-global consensus of the MASs can be achieved by the designed bounded control protocol where the Zeno phenomenon is eliminated by a designable minimum inter-event time.In addition,it is easier to find a trade-off between the convergence rate and the minimum inter-event time by an adjustable parameter.Furthermore,the results are extended to regional consensus of the MASs with the bounded control protocol.Numerical simulations show the effectiveness of the proposed approach.

Distributed Secondary Control of AC Microgrids With External Disturbances and Directed Communication Topologies:A Full-Order Sliding-Mode Approach

This paper addresses the problem of distributed secondary control for islanded AC microgrids with external disturbances.By using a full-order sliding-mode(FOSM)approach,voltage regulation and frequency restoration are achieved in finite time.For voltage regulation,a distributed observer is proposed for each distributed generator(DG)to estimate a reference voltage level.Different from some conventional observers,the reference voltage level in this paper is accurately estimated under directed communication topologies.Based on the observer,a new nonlinear controller is designed in a backstepping manner such that an FOSM surface is reached in finite time.On the surface,the voltages of DGs are regulated to the reference level in finite time.For frequency restoration,a distributed controller is further proposed such that a constructed FOSM surface is reached in finite time,on which the frequencies of DGs are restored to a reference level in finite time under directed communication topologies.Finally,case studies on a modified IEEE 37-bus test system are conducted to demonstrate the effectiveness,the robustness against load changes,and the plug-and-play capability of the proposed controllers.

Analysis and Improvement of an Efficient Controlled Quantum Secure Direct Communication and Authentication Protocol

The controlled quantum secure direct communication(CQSDC)with authentication protocol based on four particle cluster states via quantum one-time pad and local unitary operations is cryptanalyzed.It is found that there are some serious security issues in this protocol.An eavesdropper(Eve)can eavesdrop on some information of the identity strings of the receiver and the controller without being detected by the selective-CNOT-operation(SCNO)attack.By the same attack,Eve can also steal some information of the secret message that the sender transmits.In addition,the receiver can take the same kind of attack to eavesdrop on some information of the secret message out of the control of the controller.This means that the requirements of CQSDC are not satisfied.At last,we improve the original CQSDC protocol to a secure one.

Two-step quantum secure direct communication scheme with frequency coding

Quantum secure direct communication(QSDC) is an important branch of quantum cryptography. It can transmit secret information directly without establishing a key first, unlike quantum key distribution which requires this precursory event. Here we propose a QSDC scheme by applying the frequency coding technique to the two-step QSDC protocol, which enables the two-step QSDC protocol to work in a noisy environment. We have numerically simulated the performance of the protocol in a noisy channel, and the results show that the scheme is indeed robust against channel noise and loss. We also give an estimate of the channel noise upper bound.

Controlled Secure Direct Communication Protocol via the Three-Qubit Partially Entangled Set of States

In this paper,we first re-examine the previous protocol of controlled quantum secure direct communication of Zhang et al.’s scheme,which was found insecure under two kinds of attacks,fake entangled particles attack and disentanglement attack.Then,by changing the party of the preparation of cluster states and using unitary operations,we present an improved protocol which can avoid these two kinds of attacks.Moreover,the protocol is proposed using the three-qubit partially entangled set of states.It is more efficient by only using three particles rather than four or even more to transmit one bit secret information.Given our using state is much easier to prepare for multiqubit states and our protocol needs less measurement resource,it makes this protocol more convenient from an applied point of view.

Cryptanalysis of quantum broadcast communication and authentication protocol with a one-time pad

Chang et al.[Chin.Phys.623 010305(2014)]have proposed a quantum broadcast communication and authentication protocol.However,we find that an intercept-resend attack can be preformed successfully by a potential eavesdropper,who will be able to destroy the authentication function.Afterwards,he or she can acquire the secret transmitted message or even modify it while escaping detection,by implementing an efficient man-in-the-middle attack.Furthermore,we show a simple scheme to defend this attack,that is,applying non-reusable identity strings.

Controlled Quantum N-Party Simultaneous Direct Communication

In this paper,we propose a controlled quantum N-party simultaneous direct communication protocolwith single-qubit measurements.Many users can simultaneously exchange their secret messages in a set of devices withthe control of a supervisor.The eavesdropper's commonly used attacks can be detected through two security checkingprocesses.

Measurement-device-independent one-step quantum secure direct communication

The one-step quantum secure direct communication(QSDC)(Sci.Bull.67,367(2022))can effectively simplify QSDC’s operation and reduce message loss.For enhancing its security under practical experimental condition,we propose two measurement-device-independent(MDI)one-step QSDC protocols,which can resist all possible attacks from imperfect measurement devices.In both protocols,the communication parties prepare identical polarization-spatial-mode two-photon hyperentangled states and construct the hyperentanglement channel by hyperentanglement swapping.The first MDI one-step QSDC protocol adopts the nonlinear-optical complete hyperentanglement Bell state measurement(HBSM)to construct the hyperentanglement channel,while the second protocol adopts the linear-optical partial HBSM.Then,the parties encode the photons in the polarization degree of freedom and send them to the third party for the hyperentanglementassisted complete polarization Bell state measurement.Both protocols are unconditionally secure in theory.The simulation results show the MDI one-step QSDC protocol with complete HBSM attains the maximal communication distance of about354 km.Our MDI one-step QSDC protocols may have potential applications in the future quantum secure communication field.

Quantum Secure Direct Communication Protocol with Mutual Authentication Based on Single Photons and Bell States

Quantum secure direct communication(QSDC)can transmit secret messages directly from one user to another without first establishing a shared secret key,which is different from quantum key distribution.In this paper,we propose a novel quantum secure direct communication protocol based on signal photons and Bell states.Before the execution of the proposed protocol,two participants Alice and Bob exchange their corresponding identity IDA and IDB through quantum key distribution and keep them secret,respectively.Then the message sender,Alice,encodes each secret message bit into two single photons(|01>or|10>)or a Bell state(1|φ^(+)>=1/√2(|0>|-|1>1>)),and composes an ordered secret message sequence.To insure the security of communication,Alice also prepares the decoy photons and inserts them into secret message sequence on the basis of the values of IDA and IDB.By the secret identity IDA and IDB,both sides of the communication can check eavesdropping and identify each other.The proposed protocol not only completes secure direct communication,but also realizes the mutual authentication.The security analysis of the proposed protocol is presented in the paper.The analysis results show that this protocol is secure against some common attacks,and no secret message leaks even if the messages are broken.Compared with the two-way QSDC protocols,the presented protocol is a one-way quantum communication protocol which has the immunity to Trojan horse attack.Furthermore,our proposed protocol can be realized without quantum memory.

Non-verbal Communication in the Adaptation of Literary Work-Take A Dream of Red Mansions for Instance

Apart from intercultural communication and ESL education,non-verbal communication is also an ideal method to examine the visual adaptation of literary works when it is further classified into direct and indirect communication.Whether an actor or an actress’non-verbal performances are compatible to the non-verbal behaviour of the character he or she plays is of great importance in the appraisal,which is transparent through the comparison and contrast of non-verbal communication in two versions of A Dream of Red Mansions TV series.

一种改进的量子“乒乓”协议安全检测策略及其安全性分析(英文)

In order to transmit the secure messages,a deterministic secure quantum direct communication protocol,called the "Ping-pong"protocol was proposed by Bostrm and Felbinger [Phys.Rev.Lett.89,187902(2002) ].But the protocol was proved to have many vulnerabilities,and can be attacked by eavesdroppers.To overcome the problem,an improved security detection strategy which inserts the | 0〉,| 1〉,|+〉and |-〉particles into the messages as the decoy particles randomly in the"Ping-pong"protocol is presented.During the security analysis,the method of the entropy theory is introduced,and three detection strategies are compared quantitatively by using the constraint between the information which eavesdroppers can obtain and the interference introduced.Because of the presence of the trap particles |+〉and |-〉,the detection rate will be no less than 25% when Eve attacks the communication.The security analysis result shows that the efficiency of eavesdropping detection in the presented protocol is higher than the other two,so the detection strategy in the protocol can ensure that the "Ping-pong"protocol is more secure.

A Novel Quantum Stegonagraphy Based on Brown States

In this paper,a novel quantum steganography protocol based on Brown entangled states is proposed.The new protocol adopts the CNOT operation to achieve the transmission of secret information by the best use of the characteristics of entangled states.Comparing with the previous quantum steganography algorithms,the new protocol focuses on its anti-noise capability for the phase-flip noise,which proved its good security resisting on quantum noise.Furthermore,the covert communication of secret information in the quantum secure direct communication channel would not affect the normal information transmission process due to the new protocol’s good imperceptibility.If the number of Brown states transmitted in carrier protocol is many enough,the imperceptibility of the secret channel can be further enhanced.In aspect of capacity,the new protocol can further expand its capacity by combining with other quantum steganography protocols.Due to that the proposed protocol does not require the participation of the classic channel when it implements the transmission of secret information,any additional information leakage will not be caused for the new algorithm with good security.The detailed theoretical analysis proves that the new protocol can own good performance on imperceptibility,capacity and security.

A quantum secure direct communication scheme based on intermediate-basis

Quantum secure direct communication(QSDC)is a method of communication that transmits secret information directly through a quantum channel.This paper proposes a two-step QSDC scheme based on intermediate-basis,in which the intermediate-basis Einstein–Podolsky–Rosen(EPR)pairs can assist to detect channel security and help encode information.Specifically,the intermediate-basis EPR pairs reduce the probability of Eve choosing the correct measurement basis in the first step,enhancing the security of the system.Moreover,they encode information together with information EPR pairs to improve the transmission efficiency in the second step.We consider the security of the protocol under coherent attack when Eve takes different dimensions of the auxiliary system.The simulation results show that intermediate-basis EPR pairs can lower the upper limit of the amount of information that Eve can steal in both attack scenarios.Therefore,the proposed protocol can ensure that the legitimate parties get more confidential information and improve the transmission efficiency.

Experimental long-distance quantum secure direct communication

Quantum secure direct communication(QSDC) is an important quantum communication branch, which realizes the secure information transmission directly without encryption and decryption processes.Recently, two table-top experiments have demonstrated the principle of QSDC. Here, we report the first long-distance QSDC experiment, including the security test, information encoding, fiber transmission and decoding. After the fiber transmission of 0.5 km, quantum state fidelities of the two polarization entangled Bell states are 91% and 88%, respectively, which are used for information coding. We theoretically analyze the performance of the QSDC system based on current optical communication technologies,showing that QSDC over fiber links of several tens kilometers could be expected. It demonstrates the potential of long-distance QSDC and supports its future applications on quantum communication networks.

Experimental quantum secure direct communication with single photons

Quantum secure direct communication is an important mode of quantum communication in which secret messages are securely communicated directly over a quantum channel.Quantum secure direct communication is also a basic cryptographic primitive for constructing other quantum communication tasks,such as quantum authentication and quantum dialog.Here,we report the first experimental demonstration of quantum secure direct communication based on the DL04 protocol and equipped with single-photon frequency coding that explicitly demonstrated block transmission.In our experiment,we provided 16 different frequency channels,equivalent to a nibble of four-bit binary numbers for direct information transmission.The experiment firmly demonstrated the feasibility of quantum secure direct communication in the presence of noise and loss.

Quantum secure direct communication with cluster states

A quantum secure direct communication protocol with cluster states is proposed.Compared with the deterministic secure quantum communication protocol with the cluster state proposed by Yuan and Song(Int.J.Quant.Inform.,2009,7:689),this protocol can achieve higher intrinsic efficiency by using two-step transmission.The implementation of this protocol is also discussed.

Generic security analysis framework for quantum secure direct communication

Quantum secure direct communication provides a direct means of conveying secret information via quantum states among legitimate users.The past two decades have witnessed its great strides both theoretically and experimentally.However,the security analysis of it still stays in its infant.Some practical problems in this field to be solved urgently,such as detector efficiency mismatch,side-channel effect and source imperfection,are propelling the birth of a more impeccable solution.In this paper,we establish a new framework of the security analysis driven by numerics where all the practical problems may be taken into account naturally.We apply this framework to several variations of the DL04 protocol considering real-world experimental conditions.Also,we propose two optimizing methods to process the numerical part of the framework so as to meet different requirements in practice.With these properties considered,we predict the robust framework would open up a broad avenue of the development in the field.

Quantum secure direct communication with entanglement source and single-photon measurement

Quantum secure direct communication(QSDC)transmits information directly over a quantum channel.In addition to security in transmission,it avoids loopholes of key loss and prevents the eavesdropper from getting ciphertext.In this article,we propose a QSDC protocol using entangled photon pairs.This protocol differs from existing entanglement-based QSDC protocols because it does not perform Bell-state measurement,and one photon of the entangled pair is measured after the entanglement distribution.It has the advantage of high signal-to-noise ratio due to the heralding function of entanglement pairs,and it also has the relative ease in performing single-photon measurement.The protocol can use a practical entanglement source from spontaneous parametric down-conversion(SPDC);Gottesman-Lo-Lu¨tkenhaus-Preskill theory and the decoy state method give a better estimate of the error rate.Security analysis is completed with Wyner’s wiretap channel theory,and the lower bound of the secrecy capacity is estimated.Numerical simulations were carried out to study the performance of the protocol.These simulations demonstrated that the protocol with a practical SPDC entanglement source performed well and was close to the case with an ideal entanglement source.

Practical decoy-state quantum secure direct communication

Quantum secure direct communication(QSDC) has been demonstrated in both fiber-based and free-space channels using attenuated lasers. Decoy-state QSDC by exploiting four decoy states has been proposed to address the problem of photon-numbersplitting attacks caused by the use of attenuated lasers. In this study, we present an analysis of the practical aspects of decoy-state QSDC. First, we design a two-decoy-state protocol that only requires two decoy states, thereby significantly reducing experimental complexity. Second, we successfully perform full parameter optimization for a real-life QSDC system by introducing a genetic algorithm. Our simulation results show that the two-decoy-state protocol could be the best choice for developing a practical QSDC system. Furthermore, full optimization is crucial for a high-performance QSDC system. Our work serves as a major step toward the further development of practical decoy-state QSDC systems.

One-step device-independent quantum secure direct communication

Device-independent quantum secure direct communication(DI-QSDC)can relax the security assumptions about the devices’internal working,and effectively enhance QSDC’s security.In this paper,we put forward the first hyperentanglement-based one-step DI-QSDC protocol.In this protocol,the communication parties adopt the nonlocal hyperentanglement-assisted complete Bell state analysis,which enables the photons to transmit in the quantum channel for only one round.The one-step DI-QSDC can directly transmit 2 bits of messages by a hyperentangled photon pair,and is unconditionally secure in theory.Compared with the original DI-QSDC protocol(Sci.Bull.65,12(2020)),the one-step DI-QSDC protocol can simplify the experiment and reduce the message loss.In particular,with the help of the hyperentanglement heralded amplification and the hyperentanglement purification,the message loss and the message error caused by the channel noise can be completely eliminated,and the communication distance can be largely extended.By using the photon source with a repetition rate of 10 GHz,the one-step DI-QSDC’s secret message capacity under 50 km communication distance achieves about 7 bit/s with the initial fidelity in each degree of freedom of 0.8.Combined with the quantum repeater,it is possible for researchers to realize the one-step DI-QSDC with an arbitrarily long distance.