Generalized tripartite scheme for sharing arbitrary 2n-qudit state

Utilizing three non-maximally entangled qutrit pairs as quantum channels, we first propose a generalized tripartite scheme for sharing an arbitrary two-qutrit state with generalized Bell-state measurements. In the scheme if and only if the two recipients collaborate together, they can recover the split qutrit state with the probability determined uniquely by the smallest coefficients of the non-maximally entangled pairs. Afterwards, we further extend the scheme for sharing an arbitrary 2n-qudit state by taking 3n non-maximally entangled qudit pairs as quantum channels. Moreover, the scheme success probability relative to the inherent entanglement in quantum channels and its structure is simply discussed.     

Continuous Variable Quantum Secret Sharing with Chinese Remainder Theorem

Motivated by the structure characteristics of Chinese Remainder Theorem(CRT), a continuous variable quantum secret sharing scheme is proposed to ensure the security of the network-based communication system. The initial secret is decomposed and recovered by solving the equations of CRT which provides various threshold structures to enhance the universality, flexibility and practicability of the scheme. The shares are encoded to two-mode squeezed vacuum state by displacement operation for secret distributing. Compared with the discrete variable quantum secret sharing, this scheme can increase the transmission capacity due to the improved data-processing for quantum state generation, manipulation, and detection. The security analysis is elucidated by calculating the bit error rates(BERs) under different conditions and it demonstrates that the scheme has the capability to protect secrets from eavesdropping of dishonest players no matter with the channel transmission efficiency.

     

The influences of electric field and temperature on state energies of a strong-coupling polaron in an asymmetric Gaussian potential quantum well

We investigate the electric field effect on the ground state (GS), the first-excited state (FES) and the excitation energies of a strong-coupled polaron in an asymmetric Gaussian potential (AGP) quantum well (QW) by using a variational method of the Pekar type (VMPT). By employing the quantum statistics theory (QST), we also study the temperature effects on the state energies (SE). It is found that the SE of polaron are an increasing function of temperature. The polaron's SE are decreasing functions of electric field, but the excitation energy is an increasing one.     

量子比特的普适远程翻转和克隆

提出一种把量子隐形传态、最佳普适量子比特翻转和最佳普适量子克隆三者结合起来的量子比特普适远程翻转和克隆方案.当发送者和处于不同地点的三个接收者共享一个特定的四粒子纠缠态作为量子信道时,通过发送者的Bell基测量、经典通信和各个接收者的局域幺正变换,一个接收者能够以2/3的最佳保真度得到一份原未知量子比特的正交补态,另外两个接收者能够分别以5/6的最佳保真度得到原未知量子比特的一份拷贝.此方案用较少的量子纠缠资源同时完成了未知量子比特的普适远程翻转和克隆,且其保真度分别达到了最佳.实现此方案的关键在于构造出发送者和接收者共享的特定四粒子纠缠态作为量子信道,分析了此特殊四粒子态内在的纠缠结构.     

Quantum Sharing an Unknown Multi-Particle State via POVM

Our purpose in this paper is to present a new tripartite quantum state sharing using partially quantum resources. The first scheme is to probabilistically split an unknown n-particle state using pre-shared a partially entangled four-particle cluster state as quantum resource by constructing some proper POVM. This scheme is further extended to share an unknown multi-particle cluster state using different states as quantum resources. Our schemes with general quantum channels are useful for various quantum information processing and quantum network tasks.     

Wigner function and the entanglement of quantized Bessel—Gaussian vortex state of quantized radiation field

A new kind of quantum non-Gaussian state with vortex structure, termed Bessel-Gaussian vortex state, is constructed, which is an eigenstate of sum of squared annihilation operators a² + b². The Wigner function of the quantum vortex state is derived and exhibits negativity which is an indication of nonclassicality. It is also found that quantized vortex state is always in entanglement. And a scheme for generating such quantized vortex states is proposed.     

Quantum Communication Scheme Using Non-symmetric Quantum Channel

A theoretical quantum communication scheme based on entanglement swapping and superdense coding is proposed with a 3-dimensional Bell state and 2-dimensional Bell state function as quantum channel. quantum key distribution and quantum secure direct communication can be simultaneously accomplished in the scheme. The scheme is secure and has high source capacity. At last, we generalize the quantum communication scheme to d-dimensional quantum channel.     

High efficient scheme for remote state preparation with cavity QED

In this paper, a scheme is proposed for remote state preparation （RSP） with cavity quantum electrodynamics （QED）. In our scheme, two observers share two-atom nonmaximally entangled state as quantum channels and can realize remote preparation of state of an atom. We also propose a generalization for remote preparation of N-atom entangled state by （N＋1）-atom GHZ-like state （N ≥ 2）. By this scheme, one single-atom projective measurement is enough for the RSP of a qubit or N-atom entangled state, and the probability of success for RSP is unity. Furthermore, we have considered the case where observers use W-like state as quantum channels to realize RSP of a qubit. We compare our scheme with existing ones.     

Wigner function and the entanglement of a quantized Bessel-Gaussian vortex state of a quantized radiation field

A new kind of quantum non-Gaussian state with a vortex structure,termed a Bessel-Gaussian vortex state,is constructed,which is an eigenstate of the sum of squared annihilation operators a2+b2.The Wigner function of the quantum vortex state is derived and exhibits negativity which is an indication of nonclassicality.It is also found that a quantized vortex state is always in entanglement.And a scheme for generating such quantized vortex states is proposed.     

Description of physical systems

A general “logical” scheme, containing both classical and quantum mechanics, is developed on the basis of plausible axioms. We introduce the division of states and yes-no measurements into sharp and diffuse ones, and prove that sharp states possess their carriers. Owing to this result, the existence of lattice joins and meets is proved for a wide class of elements of the logic. This “semi-lattice” structure gives the familiar lattice picture for special cases of classical and quantum mechanics. The notion of quantum superposition is introduced in this general scheme. It is proved that if in a theory appear nontrivial quantum superpositions, then this theory is “undeterministic” and vise versa. Further analysis of the pure state space leads to the construction of the canonical embedding of the general logic into an orthomodular complete ortho-lattice. After defining the probability of transition between pure states, the pure state space appears to be a generalization of Mielnik's “probability space” of quantum mechanics.     

利用一个三粒子W态隐形传送N粒子GHZ态

杨洪钦等提出一个用两个三粒子W态作为量子信道将N粒子GHZ态从发送者传送给两个接收者中任意一个的量子隐形传送方案. 给出其理论分析,并提出了一个仅用一个三粒子W态作为量子信道将N粒子GHZ态传送给两个接收者之一的量子隐形传送的方案. 关键词： 隐形传态 GHZ态 W态量子信道     

Quantum state sharing of an arbitrary m-qudit state with two-qudit entanglements and generalized Bell-state measurements

A scheme for quantum state sharing of an arbitrary m-qudit state is proposed with two-qudit entanglements and generalized Bell-state (GBS) measurements. In this scheme, the sender Alice should perform m two-particle GBS measurements on her 2m qudits, and the controllers also take GBS measurements on their qudits and transfer their quantum information to the receiver with entanglement swapping if the agents cooperate. We discuss two topological structures for this quantum state sharing scheme, a dispersive one and a circular one. The former is better at the aspect of security than the latter as it requires the number of the agents who should cooperate for recovering the quantum secret larger than the other one.     

Quantum state sharing of an arbitrary two-qubit state with two-photon entanglements and Bell-state measurements

Two schemes for sharing an arbitrary two-qubit state based on entanglement swapping are proposed with Bell-state measurements and local unitary operations. One is based on the quantum channel with four Einstein-Podolsky-Rosen (EPR) pairs shared in advance. The other is based on a circular topological structure, i.e., each user shares an EPR pair with his neighboring one. The advantage of the former is that the construction of the quantum channel between the agents is controlled by the sender Alice, which will improve the security of the scheme. The circular scheme reduces the quantum resource largely when the number of the agents is large. Both of those schemes have the property of high efficiency as almost all the instances can be used to split the quantum information. They are more convenient in application than the other schemes existing as they require only two-qubit entanglements and two-qubit joint measurements for sharing an arbitrary two-qubit state.     

Quantum information splitting of an arbitrary three-qubit state via the cavity input–output process

We propose a realizable quantum information splitting (QIS) scheme for an arbitrary three-qubit state via the cavity input–output process. In our scheme, a four-qubit cluster state and a three-qubit Greenberger–Horne–Zeilinge (GHZ) state are used as quantum channel. The sender and controller only need to perform Bell-state measurements and a single-qubit measurement, respectively. The receiver can reconstruct the arbitrary three-qubit state by classical communication and local operations. Compared with the scheme in Nie et al. [Optics Communications 284 (2011) 1457], the quantum resources and classical information in our scheme are decreased by 5 qubits and 1 bit, respectively. Moreover, we replace the W-state category measurement in the former with Bell-state measurements and a single-qubit measurement, which is more simple and feasible in experiment.     

Circular Controlled Quantum Teleportation by a Genuine Seven-qubit Entangled State

A scheme of circular controlled quantum teleportation, which is a novel version of bidirectional controlled quantum teleportation, is proposed using a specific genuine seven-qubit entangled state as quantum channel, and then it is generalized to the scene with a general genuine seven-qubit entangled state as channel. This means that with the control of the supervisor Daniel while Alice teleportates an unknown qubit state to Bob, Bob can also teleportate an unknown qubit state to Charlie and Charlie can also teleportate an unknown qubit state to Alice circularly, simultaneously. Compared with the BCQT schemes proposed before, the intrinsic efficiency of our scheme is optimal.

     

Revisiting “Quantum State Sharing of an Arbitrary Two-Atom State by Using a Six-Atom Cluster State in Cavity QED”

In Nie et al. (Int. J. Theor. Phys. 50: 2526, 2011), authors put forward a cavity QED scheme for deterministic quantum state sharing (QSTS) of an arbitrary two-atom state. They claimed that, the quantum channel of the QSTS scheme is a six-atom cluster state. After simple calculation, one can see that the quantum channel they used is a direct product of two three-atom GHZ states. In this paper, we propose a cavity QED scheme for QSTS of an arbitrary two-atom state via a six-atom cluster state channel. In our scheme, two two-atom Bell state measurements are transformed into the discrimination of single-atom product states. Moreover, the two-atom unitary operation is changed to single-qubit unitary operations. Our scheme is insensitive to the cavity decay. The necessary time for the scheme is much shorter than the Rydberg-atom lifespan, therefore atom decays do not need to be considered.     

通过Raman相互作用隐形传送未知多原子纠缠态

基于多粒子纠缠态在证明量子非定域性和量子信息处理方面的重要应用,提出一种方案隐形传送未知原子纠缠态.方案基于Λ型三能级原子与单模腔场的简并Raman相互作用.首先让n个原子相继通过一个相干腔场来制备量子通道.然后发送者让携带未知纠缠态的另n个原子相继通过相干腔场并通过对原子与腔场的探测作联合测量.当｜α｜1时,可以用探测正交态的方法探测腔场.最后接收者根据由经典通道得到的联合测量结果重构初始态.方案的特点是用一个相干态与多个原子的纠缠态作为量子通道,简单易行.该方案有望在证明量子非定域性和量子信息过程中有重要的应用价值.     

用非最大纠缠信道对任意二粒子纠缠态的量子秘密分享

提出一个对任意二粒子纠缠态在N者之间的量子秘密分享方案,该方案利用非最大纠缠Einstein-Podolsky-Rosen(EPR)对作为量子信道,利用广义的贝尔基进行测量.接收者通过引入辅助粒子,并对其做选择性测量,就会概率性地得到最初的量子态. 关键词： 非最大纠缠的Einstein-Podolsky-Rosen(EPR)对 广义的贝尔测量     

量子无线广域网构建与路由策略

提出了一种基于多阶量子隐形传态的量子路由方案, 在量子移动终端之间没有共享纠缠对的情况下, 仍然可以完成量子态的无线传输. 该量子路由方案可以用来构建量子无线广域网, 其传输时延与所经过的链路距离和基站数目无关, 传输一个量子态所需的时间与采用量子隐形传态所需的时间相同. 因此, 从数据传输速率的观点来看, 该方案优于基于纠缠交换的量子路由方案. 关键词： 量子通信 多阶量子隐形传态 量子路由 量子无线广域网     

Generalized Multiparty Quantum Single-Qutrit-State Sharing

We present a three-party quantum single-qutrit-state sharing scheme with a non-maximally entangled three-qutrit state as the quantum channel. In the scheme, the sender’s secret quantum information (i.e., the single-qutrit state) is split in such a way that it can be probabilistically reconstructed through introducing an auxiliary qutrit and performing appropriate operations provided that the receivers both collaborate together. We work out the success probability and reveal the relation between the probability and the parameters characterizing the quantum channel. After this, we then briefly introduce the generalization of the three-party scheme to a more-party one.