Novel multiparty quantum key agreement protocol with GHZ states

In many circumstances, a shared key is needed to realize secure communication. Based on quantum mechanics principles, quantum key agreement (QKA) is a good method to establish a shared key by every party’s fair participation. In this paper, we propose a novel three-party QKA protocol, which is designed by using Greenberger–Horne–Zeilinger (GHZ) states. To realize the protocol, the distributor of the GHZ states needs only one quantum communication with the other two parties, respectively, and everyone performs single-particle measurements simply. Then, we extend the three-party QKA protocol to arbitrary multiparty situation. At last, we discuss the security and fairness of the multiparty protocol. It shows that the new scheme is secure and fair to every participant.     

Fault tolerant deterministic quantum communications using GHZ states over collective-noise channels

This study proposes two new coding functions for a GHZ state and a GHZ-like state, respectively. Based on these coding functions, two fault tolerant deterministic quantum communication (DQC) protocols are proposed. Each of the new DQC’s is robust under one kind of collective noises: collective-dephasing noise and collective-rotation noise, respectively. The sender can use the proposed coding functions to encode his/her message, and the receiver can perform the Bell measurement to obtain the sender’s message. In comparison to the existing fault tolerant DQC protocols over collective-noise channels, the proposed protocols provide the best qubit efficiency. Moreover, the proposed protocols are also free from the ordinary eavesdropping and the information leakage.     

A dynamic multiparty quantum direct secret sharing based on generalized GHZ states

This paper proposes a new dynamic multiparty quantum direct secret sharing (DQDSS) using mutually unbiased measurements based on generalized GHZ states. Without any unitary operations, an agent can obtain a shadow of the secret by simply performing a measurement on single photons. In the proposed scheme, multiple agents can be added or deleted and the shared secret need not be changed. Our DQDSS scheme has several advantages. The dealer is not required to retain any photons and can further share a predetermined key instead of a random key to the agents. Agents can update their shadows periodically, and the dealer does not need to be online. Furthermore, the proposed scheme can resist not only the existing attacks, but also cheating attacks from dishonest agents. Hence, compared to some famous DQSS schemes, the proposed scheme is more efficient and more practical. Finally, we establish a mathematical model about the efficiency and security of the scheme and perform simulation analyses with different parameters using MATLAB.     

基于GHZ态的无酉操作多方量子秘密共享方案

为了简化多方量子秘密共享协议,利用Greenberger-Horne-Zeilinger（GHZ）态和互补基特性,提出了一种简单高效的多方量子秘密共享方案。该方案无需进行任何酉操作,发送方和多个接收方之间只需一次量子通信,并使用互补基进行测量即可完成信道安全检测和秘密共享。除去少量用于检测量子信道安全的粒子,其余每个GHZ态粒子共享一个比特的经典信息。安全性分析表明该方案是安全可靠的。     

Two authenticated quantum dialogue protocols based on three-particle entangled states

In this paper, we propose two authenticated quantum dialogue protocols based on three-particle entangled states, which are both completely secure and more efficient. The first controlled quantum dialogue protocol with authentication is creatively proposed, which is secure under not only some famous external attacks but also internal attacks, for example, the dishonest controller’s attack. This protocol has a slightly increasing efficiency and less qubit cost compared to previous protocols. Besides, we present the second authenticated quantum dialogue protocol, which has a high efficiency with 80% by integrating dense coding. This protocol can also resist various well-known attacks.     

Efficient deterministic secure quantum communication protocols using multipartite entangled states

We propose two deterministic secure quantum communication protocols employing three-qubit GHZ-like states and five-qubit Brown states as quantum channels for secure transmission of information in units of two bits and three bits using multipartite teleportation schemes developed here. In these schemes, the sender’s capability in selecting quantum channels and the measuring bases leads to improved qubit efficiency of the protocols.     

Genuine three-partite entanglement in coherent states via permutation and parity symmetries

By using the works, Spiridonov (Phys Rev A 52:1909, 1995), and Wang et al. (J Phys A Math Gen 33:7451, 2000), we propose an approach to obtain genuine three-partite entangled coherent states in which the permutation symmetry and the parity one play crucial roles. We exploit the permutation and parity symmetry to construct entanglement in the standard coherent states of a system composed of three-mode bosonic field and three identical atoms. It is shown that by making use of entanglement witnesses (EW) based on GHZ-states the reduced density matrices of the three-mode bosonic field and three-atomic subsystems, after encoding as three-qubit systems, in some range of their respective parameters, are genuinely entangled.     

Fault tolerant quantum key distributions using entanglement swapping of GHZ states over collective-noise channels

This work proposes two fault tolerant quantum key distribution (QKD) protocols. Each of which is robust under one kind of collective noises: collective-dephasing noise and collective-rotation noise, respectively. Due to the use of the entanglement swapping of Greenberger–Horne–Zeilinger (GHZ) state as well as the decoy logical qubits, the new protocols provide the best qubit efficiency among the existing fault tolerant QKD protocols over the same collective-noise channel. The receiver simply performs two Bell measurements to obtain the raw key. Moreover, the proposed protocols are free from several well-known attacks and can also be secure over a lossy channel.     

Biseparability of noisy pseudopure,W and GHZ states using conditional quantum relative Tsallis entropy

We employ the conditional version of sandwiched Tsallis relative entropy to determine \(1:N-1\) separability range in the noisy one-parameter families of pseudopure and Werner-like N-qubit W, GHZ states. The range of the noisy parameter, for which the conditional sandwiched Tsallis relative entropy is positive, reveals perfect agreement with the necessary and sufficient criteria for separability in the \(1:N-1\) partition of these one parameter noisy states.     

Using human error information for error prevention

Developing error-free software requirements is of critical importance to the success of a software project. Problems that occur during requirements collection and specification, if not fixed early, are costly to fix later. Therefore, it is important to develop techniques that help requirements engineers detect and prevent requirements problems. As a human-centric activity, requirements engineering can be influenced by psychological research about human errors, which are the failings of human cognition during the process of planning and executinge a task. We have employed human error research to describe the types of problems that occur during requirements engineering. The goals of this research are: (1) to evaluate whether understanding human errors contributes to the prevention of errors and concomitant faults during requirements engineering and (2) to identify error prevention techniques used in industrial practice. We conducted a controlled classroom experiment to evaluate the benefits that knowledge of errors has on error prevention. We then analyzed data from two industrial surveys to identify specific prevention and mitigation approaches employed in practice. The classroom study showed that the better a requirements engineer understands human errors, the fewer errors and concomitant faults that engineer makes when developing a new requirements document. Furthermore, different types of Human Errors have different impacts on fault prevention. The industry study results identified prevention and mitigation mechanisms for each error type. Human error information is useful for fault prevention during requirements engineering. There are practices that requirements engineers can employ to prevent or mitigate specific human errors.     

Nonlocal quantum information in bipartite quantum error correction

We show how to convert an arbitrary stabilizer code into a bipartite quantum code. A bipartite quantum code is one that involves two senders and one receiver. The two senders exploit both nonlocal and local quantum resources to encode quantum information with local encoding circuits. They transmit their encoded quantum data to a single receiver who then decodes the transmitted quantum information. The nonlocal resources in a bipartite code are ebits and nonlocal information qubits, and the local resources are ancillas and local information qubits. The technique of bipartite quantum error correction is useful in both the quantum communication scenario described above and in fault-tolerant quantum computation. It has application in fault-tolerant quantum computation because we can prepare nonlocal resources offline and exploit local encoding circuits. In particular, we derive an encoding circuit for a bipartite version of the Steane code that is local and additionally requires only nearest-neighbor interactions. We have simulated this encoding in the CNOT extended rectangle with a publicly available fault-tolerant simulation software. The result is that there is an improvement in the “pseudothreshold” with respect to the baseline Steane code, under the assumption that quantum memory errors occur less frequently than quantum gate errors.     

Improving ancilla states for quantum computation

We analyze the improvement in output state fidelity upon improving the construction accuracy of ancilla states. Specifically, we simulate gates and syndrome measurements on a single qubit of information encoded into the [[7,1,3]] quantum error correction code and determine the output state fidelity as a function of the accuracy with which Shor states (for syndrome measurements) and magic states (to implement T-gates) are constructed. When no syndrome measurements are applied during the gate sequence, we observe that the fidelity increases after performance of a T-gate and improving magic states construction slows the fidelity decay rate. In contrast, when syndrome measurements are applied, loss of fidelity occurs primarily after the syndrome measurements taken after a T-gate. Improving magic state construction slows the fidelity decay rate, and improving Shor state construction raises the initial fidelity but does not slow the fidelity decay rate. Along the way, we show that applying syndrome measurements after every gate does not maximize the output state fidelity. Rather, syndrome measurements should be applied sparingly.     

A comparative study of protocols for secure quantum communication under noisy environment: single-qubit-based protocols versus entangled-state-based protocols

The effect of noise on various protocols of secure quantum communication has been studied. Specifically, we have investigated the effect of amplitude damping, phase damping, squeezed generalized amplitude damping, Pauli type as well as various collective noise models on the protocols of quantum key distribution, quantum key agreement, quantum secure direct quantum communication and quantum dialogue. From each type of protocol of secure quantum communication, we have chosen two protocols for our comparative study: one based on single-qubit states and the other one on entangled states. The comparative study reported here has revealed that single-qubit-based schemes are generally found to perform better in the presence of amplitude damping, phase damping, squeezed generalized amplitude damping noises, while entanglement-based protocols turn out to be preferable in the presence of collective noises. It is also observed that the effect of noise depends upon the number of rounds of quantum communication involved in a scheme of quantum communication. Further, it is observed that squeezing, a completely quantum mechanical resource present in the squeezed generalized amplitude channel, can be used in a beneficial way as it may yield higher fidelity compared to the corresponding zero squeezing case.     

Prospective issues for error detection

From the literature on error detection, the authors select several concepts relating error detection mechanisms and prospective memory features. They emphasize the central role of intention in the classification of the errors into slips/lapses/mistakes, in the error handling process and in the usual distinction between action-based and outcome-based detection. Intention is again a core concept in their investigation of prospective memory theory, where they point out the contribution of intention retrievals, intention persistence and output monitoring in the individual's possibilities for detecting their errors. The involvement of the frontal lobes in prospective memory and in error detection is also analysed. From the chronology of a prospective memory task, the authors finally suggest a model for error detection also accounting for neural mechanisms highlighted by studies on error-related brain activity.     

Prospective issues for error detection

From the literature on error detection, the authors select several concepts relating error detection mechanisms and prospective memory features. They emphasize the central role of intention in the classification of the errors into slips/lapses/mistakes, in the error handling process and in the usual distinction between action-based and outcome-based detection. Intention is again a core concept in their investigation of prospective memory theory, where they point out the contribution of intention retrievals, intention persistence and output monitoring in the individual's possibilities for detecting their errors. The involvement of the frontal lobes in prospective memory and in error detection is also analysed. From the chronology of a prospective memory task, the authors finally suggest a model for error detection also accounting for neural mechanisms highlighted by studies on error-related brain activity.     

Termination detection protocols for mobile distributed systems

This paper studies a fundamental problem, the termination detection problem, in distributed systems. Under a wireless network environment, we show how to handle the host mobility and disconnection problems. In particular, when some distributed processes are temporarily disconnected, we show how to capture a weakly terminated state where silence has been reached only by those currently connected processes. A user may desire to know such a state to tell whether the mobile distributed system is still running or is silent because some processes are disconnected. Our protocol tries to exploit the network hierarchy by combining two existing protocols together. It employs the weight-throwing scheme on the wired network side, and the diffusion-based scheme on each wireless cell. Such a hybrid protocol can better pave the gaps of computation and communication capability between static and mobile hosts, thus more scalable to larger distributed systems. Analysis and simulation results are also presented     

Continuous-variable quantum network coding for coherent states

As far as the spectral characteristic of quantum information is concerned, the existing quantum network coding schemes can be looked on as the discrete-variable quantum network coding schemes. Considering the practical advantage of continuous variables, in this paper, we explore two feasible continuous-variable quantum network coding (CVQNC) schemes. Basic operations and CVQNC schemes are both provided. The first scheme is based on Gaussian cloning and ADD/SUB operators and can transmit two coherent states across with a fidelity of 1/2, while the second scheme utilizes continuous-variable quantum teleportation and can transmit two coherent states perfectly. By encoding classical information on quantum states, quantum network coding schemes can be utilized to transmit classical information. Scheme analysis shows that compared with the discrete-variable paradigms, the proposed CVQNC schemes provide better network throughput from the viewpoint of classical information transmission. By modulating the amplitude and phase quadratures of coherent states with classical characters, the first scheme and the second scheme can transmit \(4{\log _2}N\) and \(2{\log _2}N\) bits of information by a single network use, respectively.     

A measure of non-Gaussianity for quantum states

We propose a measure of non-Gaussianity for quantum states of a system of n oscillator modes. Our measure is based on the quasi-probability \({Q(\alpha),\alpha\in\mathcal{C}^n}\) . Since any measure of non-Gaussianity is necessarily an attempt at making a quantitative statement on the departure of the shape of the Q function from Gaussian, any good measure of non-Gaussianity should be invariant under transformations which do not alter the shape of the Q functions, namely displacements, passage through passive linear systems, and uniform scaling of all the phase space variables: Q(α) → λ²ⁿ Q(λα). Our measure which meets this ‘shape criterion’ is computed for a few families of states, and the results are contrasted with existing measures of non-Gaussianity. The shape criterion implies, in particular, that the non-Gaussianity of the photon-added thermal states should be independent of temperature.     

Entanglement measure for pure six-qubit quantum states

In this work we propose a six-way entanglement measure for pure six-qubit quantum states. The proposed measure is used to quantify the entanglement of some six-qubit states useful in quantum information processing and in the analysis of entanglement variation of some parameterized six-qubit states.     

Explicit error syndrome calculation for quantum graph codes

In Schlingemann (J Math Phys 45:4322, 2004) it was proved that for any calculated error syndrome for quantum graph codes exists an appropriate local correction operation. In this paper we propose an explicit operator to perform the calculation of the syndrome to these codes. Our method makes use of the inverse quantum Fourier transform.