Multi-agent controlled teleportation of multi-qubit quantum information via two-step protocol

Utilizing both the general quantum teleportation and the two-step protocol, a new method is presented by which multi-qubit quantum information can be teleported in a much easier way from a sender Alice to a receiver Bob via the control of many agents in a network than by Yang et al＇s method. In this method, only all the agents collaborate with Bob can the unknown states in Alice＇s qubits be fully reconstructed in Bob＇s qubits. Comparisons between the method and Yang et al＇s method are made. Results show that, in this method, the preparation difficulty of initial states and the identification difficulty of entangled states are considerably reduced, new method is more feasible in technique, and Hadamard operations are not needed at all.

Deterministic quantum teleportation and information splitting via a peculiar W-class state

In the paper （Phys. Rev. 2006 A 4 062320） Agrawal et al. have introduced a kind of W-class state which can be used for the quantum teleportation of single-particle state via a three-particle von Neumann measurement, and they thought that the state could not be used to teleport an unknown state by making two-particle and one-particle measurements. Here we reconsider the features of the W-class state and the quantum teleportation process via the W-class state. We show that, by introducing a unitary operation, the quantum teleportation can be achieved deterministically by making two-particle and one-particle measurements. In addition, our protocol is extended to the process of teleporting two-particle state and splitting information.

Information security through controlled quantum teleportation networks

Information security is the backbone of current intelligent systems,such as the Internet of Things(IoT),smart grids,and Machine-to-Machine(M2M)communication.The increasing threat of information security requires new models to ensure the safe transmission of information through such systems.Recently,quantum systems have drawn much attention since they are expected to have a significant impact on the research in information security.This paper proposes a quantum teleportation scheme based on controlled multi-users to ensure the secure information transmission among users.Quantum teleportation is an original key element in a variety of quantum information tasks as well as quantum-based technologies,which plays a pivotal role in the current progress of quantum computing and communication.In the proposed scheme,the sender transmits the information to the receiver under the control of a third user or controller.Here,we show that the efficiency of the proposed scheme depends on the properties of the transmission channel and the honesty of the controller.Compared with various teleportation scheme presented recently in the literature,the most important difference in the proposed scheme is the possibility of suspicion about the honesty of the controller and,consequently,taking proper precautions.

Many-Agent Controlled Teleportation of Multi-qubit Quantum Information via Quantum Entanglement Swapping

We present a method to teleport multi-qubit quantum information in an easy way from a sender to a receiver via the control of many agents in a network. Only when all the agents collaborate with the quantum information receiver can the unknown states in the sender's qubits be fully reconstructed in the receiver's qubits. In our method,agents's control parameters are obtained via quantum entanglement swapping. As the realization of the many-agent controlled teleportation is concerned, compared to the recent method [C.P. Yang, et al., Phys. Rev. A 70 (2004) 022329],our present method considerably reduces the preparation difficulty of initial states and the identification difficulty of entangled states, moreover, it does not need local Hadamard operations and it is more feasible in technology.

Controlled Teleportation of Multi-qutrit Quantum Information by Swapping Entanglement

我们在场为在一个网络经由许多代理人的控制从一个发送者移植 multi-qutrit 量信息到接收装置的电视的一个计划。代理人的控制参数经由量纠纷交换被获得。在我们的计划，张和人是 QSS 协议[Phys。加快。一 72 (2005 ) 022303 ] 基于钟状态，纠纷交换被概括到一个 qutrit 盒子。我们的计划拥有比工作有更高的代码能力和更好的安全的优点[Commun。Theor。Phys。44 (2005 ) 847 ] 在为 multi-qubit 的控制远距传物上。

Controlled Teleportation of Multi-qudit Quantum Information by Entanglement Swapping

在这篇论文，我们在场为移植 multi-qudit 量状态的电视的一个计划从到经由许多控制器的接收装置查理的艾莉斯摆动的发送者，谁的控制参数，用纠纷交换格言联盟者被获得 d 维的 EPR 对。在我们的计划，杨的 qutrit 控制了远距传物协议[Commun。Theor。Phys。49 (2008 ) 338 ] 基于钟状态，纠纷交换被概括到 qudit 盒子。multi-qudit 的计划拥有比 multi-qutrit 的有更高的代码能力和更好的安全的优点。

A controlled quantum teleportation scheme of an N-particle unknown state via three-particle W1 states

In this paper a controlled quantum teleportation scheme of an N-particle unknown state is proposed when N groups of three-particle W1 states are utilized as quantum channels. The quantum information of N-particle unknown state is transmitted from the sender to the recipient under the control of all supervisors. It can be realized with a certain probability. After the sender makes Bell-state measurements and the supervisors perform the computational basis measurements, the recipient will introduce auxiliary particles and carry out unitary transformations depending on classical information from the sender and the supervisors. Finally, the computational basis measurement will be performed by the recipient to confirm whether the teleportation succeeds or not. The successful completion of the scheme relies on all supervisors＇ cooperation. In addition, the fidelity and security of the scheme are discussed.

Quantum Teleportation Schemes of an N-Particle State via Three-Particle General W States

当三粒子的一般 W 状态的 N 组作为量隧道被利用时，移植任意的 N 粒子和未知状态的电视的二个计划被建议。在第一个计划，量隧道被发送者和接受者分享。在发送者他的上的钟状态大小以后(她的) 粒子，接受者在他的上执行单一的转变(她的) 粒子。然后，接受者执行计算基础大小认识到远距传物。如果，接受者能与成功的远距传物的相等的最大的概率粒子序列在也上恢复状态他(她) 执行适当单一的转变。在第二个计划，量隧道被发送者，接受者和第三分享。在如果他们同意合作，发送者的钟状态大小和第三大小是计算基础大小以后，接受者将介绍辅助粒子并且执行适当单一的转变。最后，接受者执行计算基础大小完成远距传物。如果并且仅当第三同意与接受者合作，第二个计划能被认识到。

Demonstration of controlled high-dimensional quantum teleportation

Controlled quantum teleportation(CQT), which is regarded as the prelude and backbone for a genuine quantum internet, reveals the cooperation, supervision, and control relationship among the sender, receiver, and controller in the quantum network within the simplest unit. Compared with low-dimensional counterparts, high-dimensional CQT can exhibit larger information transmission capacity and higher superiority of the controller's authority. In this article, we report a proof-of-principle experimental realization of three-dimensional(3D) CQT with a fidelity of 97.4% ± 0.2%. To reduce the complexity of the circuit, we simulate a standard 4-qutrit CQT protocol in a 9×9-dimensional two-photon system with high-quality operations. The corresponding control powers are 48.1% ± 0.2% for teleporting a qutrit and 52.8% ± 0.3% for teleporting a qubit in the experiment, which are both higher than the theoretical value of control power in 2-dimensional CQT protocol(33%). The results fully demonstrate the advantages of high-dimensional multi-partite entangled networks and provide new avenues for constructing complex quantum networks.

Improving the teleportation of quantum Fisher information under non-Markovian environment

Quantum teleportation is designed to send an unknown quantum state between two parties.In the perspective of remote quantum metrology,one may be interested in teleporting the information that is encoded by physical parameters synthesized by quantum Fisher information(QFI).However,the teleported QFI is often destroyed by the unavoidable interaction between the system and the environment.Here,we propose two schemes to improve the teleportation of QFI in the non-Markovian environment.One is to control the quantum system through the operations of weak measurement(WM)and corresponding quantum measurement reversal(QMR).The other is to modify the quantum system based on the monitoring result of the environment(i.e.,environment-assisted measurement,EAM).It is found that,in the non-Markovian environment,these two schemes can improve the teleportation of QFI.By selecting the appropriate strengths of WM and QMR,the environment noise can be completely eliminated and the initial QFI is perfectly teleported.A comprehensive comparison shows that the second scheme not only has a higher probability of success than the first one,but also has a significant improvement of the teleported QFI.

Recovering information in probabilistic quantum teleportation

In this paper we redesign the probabilistic teleportation scheme considered in Phys.Rev.A 61,034301(2000)by Wan-Li Li et al.,where the optimal state extraction protocol complements the basic teleportation process with a partially entangled pure state channel,in order to transfer the unknown state with fidelity 1.Unlike that scheme,where the information of the unknown state is lost if the state extraction fails,our proposal teleports exactly and optimally an unknown state,and allows to recover faithfully that state when the process has not succeeded.In order to study the resilience of the scheme,we apply it to the teleportation problem through a quantum channel in a mixed state with pure dephasing.We find that a successful process transfers an unfaithful state,namely,the outcome state acquires the decoherence of the channel,but the unknown state is recovered by the sender with fidelity 1 if the teleportation fails.In addition,in this case,the fidelity of the teleported state has quantum features only if the channel has an amount of entanglement different from zero.

Several teleportation schemes of an arbitrary unknown multi-particle state via different quantum channels

We first provide four new schemes for two-party quantum teleportation of an arbitrary unknown multi-particle state by using three-, four-, and five-particle states as the quantum channel, respectively. The successful probability and fidelity of the four schemes reach 1. In the first two schemes, the receiver can only apply one of the unitary transformations to reconstruct the original state, making it easier for these two schemes to be directly realized. In the third and fourth schemes, the sender can preform Bell-state measurements instead of multipartite entanglement measurements of the existing similar schemes, which makes real experiments more suitable. It is found that the last three schemes may become tripartite controlled teleportation schemes of teleporting an arbitrary multi-particle state after a simple modification. Finally, we present a new scheme for three-party sharing an arbitrary unknown multi-particle state. In this scheme, the sender first shares three three-particle GHZ states with two agents. After setting up the secure quantum channel, an arbitrary unknown multi-particle state can be perfectly teleported if the sender performs three Bell-state measurements, and either of two receivers operates an appropriate unitary transformation to obtain the original state with the help of other receiver＇s three single-particle measurements. The successful probability and fidelity of this scheme also reach 1. It is demonstrated that this scheme can be generalized easily to the case of sharing an arbitrary unknown multi-particle state among several agents.

Controlled Quantum Network Coding Without Loss of Information

Quantum network coding is used to solve the congestion problem in quantum communication,which will promote the transmission efficiency of quantum information and the total throughput of quantum network.We propose a novel controlled quantum network coding without information loss.The effective transmission of quantum states on the butterfly network requires the consent form a third-party controller Charlie.Firstly,two pairs of threeparticle non-maximum entangled states are pre-shared between senders and controller.By adding auxiliary particles and local operations,the senders can predict whether a certain quantum state can be successfully transmitted within the butterfly network based on the Z-{10>,|1>}basis.Secondly,when trans-mission fails upon prediction,the quantum state will not be lost,and it will sill be held by the sender.Subsequently,the controller Charlie re-prepares another three-particle non-maximum entangled state to start a new round.When the predicted transmission is successful,the quantum state can be transmitted successfully within the butterfly network.If the receiver wants to receive the effective quantum state,the quantum measurements from Charlie are needed.Thirdly,when the transmission fails,Charlie does not need to integrate the X-{1+>,1->}basis to measure its own particles,by which quantum resources are saved.Charlie not only controls the effective transmission of quantum states,but also the usage of classical and quantum channels.Finally,the implementation of the quantum circuits,as well as a flow chart and safety analysis of our scheme,is proposed.

The Security Analysis of Two-Step Quantum Direct Communication Protocol in Collective-Rotation Noise Channel

To analyze the security of two-step quantum direct communication protocol （QDCP） by using Einstein-Podolsky Rosen pair proposed by Deng et al. [Phys. Rev. A 68 （2003）042317] in collective-rotation noise channel, an excellent model of noise analysis is proposed. In the security analysis, the method of the entropy theory is introduced, and is compared with QDCP, an error rate point Qo（M ： （Q0, 1.0）） is given. In different noise levels, if Eve wants to obtain the same amount of information, the error rate Q is distinguishable. The larger the noise level ~ is, the larger the error rate Q is. When the noise level ~ is lower than 11%, the high error rate is 0.153 without eavesdropping. Lastly, the security of the proposed protocol is discussed. It turns out that the quantum channel will be safe when Q 〈 0.153. Similarly, if error rate Q〉 0.153 = Q0, eavesdropping information I 〉 1, which means that there exist eavesdroppers in the quantum channel, and the quantum channel will not be safe anymore.

Information Field and Physical Noise Generator Entanglement

In experiments with physical noise generators based on electronic or photonic quantum events, significant deviations from random distributions have been repeatedly observed. To explain these effects, intention-based interactions between consciousness and mind with physical random processes have been suggested, either being caused by individual minds or by a proposed global mind. As these explanations involve physically undefined objects such as “mind” and “consciousness”, an explanatory model based on the concept of an information field is given herein, based on the concept of generalized quantum entanglement, including the entanglement of physical noise processes with information fields and an analogy to quantum teleportation. In addition, the non-random hypothesis of using such a physical noise generator in capturing qualitative characteristics of individuals is tested in a randomized controlled study with 100 participants.

On the Security of Quantum Key Distribution Ping-Pong Protocol

Computational based cryptography might not guarantee long term security if computational algorithms, computers, and so on are made remarkable progress. Therefore, quantum cryptography with unconditionally security attracts attention. In this paper, we consider security of a two-way quantum key distribution protocol, so called Ping-Pong protocol. As a result, we introduce not only robustness but also a different information disturbance theorem, which denotes a trade-off relationship between information gain for an eavesdropper and error rate, from the related works for an attack model.

Classical Capacity for a Continuous Variable Teleportation Channel

The process of quantum teleportation can be considered as a quantum channel, The exact classical capacity of the continuous variable teleportation channel is presented and the channel fidelity is also derived.

量子远距传态(Teleportation)在量子计算网络中的实现

本文提出了一个通过量子计算网络来对三个未知量子态同时进行量子远距传态（ｔｅｌｅｐｏｒｔａｔｉｏｎ）的方案，对比以前的远距传态方案，本方案不仅效率高，更符合量子远距传态（ｔｅｌｅｐｏｒｔａｔｉｏｎ）的原始定义，而且容易扩展到同时传输多个未知量子态和多粒子最大纠缠态．

Controlled Teleportation of an Unknown N-qubit Entangled GHZ State

<正> A scheme for controlled teleportation of an unknown N-qubit entangled GHZ state from the sender Aliceto the distant receiver Bob is proposed.And m-qubit GHZ state is sufficient for the task of control by m spatially-separated supervisors.Conditioned on the local operations executed by all participants,Bob can faithfully restore theoriginal state by performing relevant unitary transformations with the aid of some classical message about measurementresults.Anyone's absence will absolutely lead to the failure of teleportation.