Hierarchically controlled remote preparation of an arbitrary single-qubit state by using a four-qubit $$|\chi \rangle $$ entangled state

In this paper, we present a scheme for Hierarchically controlled remote preparation of an arbitrary single-qubit state via a four-qubit \(|\chi \rangle \) state as the quantum channel. In this scheme, a sender wishes to help three agents to remotely prepare a quantum state, respectively. The three agents are divided into two grades, that is, an agent is in the upper grade and other two agents are in the lower grade. It is shown that the agent of the upper grade only needs the assistance of any one of the other two agents for recovering the sender’s original state, while an agent of the lower grade needs the collaboration of all the other two agents. In other words, the agents of two grades have different authorities to recover sender’s original state.     

Quantum private comparison protocol based on the entanglement swapping between $$\chi ^+$$ state and W-Class state

Quantum private comparison (QPC) protocol, including Alice, Bob and the third party Charlie, aims at comparing Alice and Bob’s secret inputs correctly without leaking them. Firstly, \(\chi ^+\) state and W-Class state are used to conduct the entanglement swapping in this protocol. Either the basis \(\{|\phi ^\pm \rangle ,|\psi ^\pm \rangle \}\) or the basis \(\{|\chi ^\pm \rangle ,|\omega ^\pm \rangle \}\) is chosen by Alice and Bob based on the predetermined value to measure the particle pairs. And three bits of secret inputs can be compared in this protocol in every comparison time, while most of previous QPC protocols can only compare one or two bits. The qubit efficiency of this protocol is 60% more than others, which are 50% at most. Secondly, if the eavesdropper intends to obtain the secret inputs, it is important and primary to get the measurement results of particle pairs. In this protocol, even if the eavesdropper gets the accurate particle pairs, he cannot get the right measurement results without the right basis. Finally, this protocol is analyzed to be able to defend the secret inputs against various kinds of attack.     

Deterministic transmission of an arbitrary single-photon polarization state through bit-flip error channel

We present two error-tolerance transmission protocols of a single-photon polarization state when bit-flip error is taken into account. For achieving the transmission target of the single-photon state, the first protocol needs to encode it to a nonmaximally entangled Bell state. Exploiting the interaction of the polarization entanglement with spatial entanglement between two photons, its success probability is 100 %. Different from the first protocol, the second one utilizes the idea of teleportation with an auxiliary Bell state. By performing quantum nondemolition measurement to analyze the parity, conventional measurement, and unitary transformation operations, the success probability of the second protocol is approximately unity. Furthermore, the second protocol can be generalized to the error-tolerance transmission of an arbitrary mixed state or the distribution of an arbitrary multi-photon entangled state.     

Efficient schemes for the quantum teleportation of a sub-class of tripartite entangled states

In this paper we propose two schemes for teleportation of a sub-class of tripartite states, the first one with the four-qubit cluster state and the second one with two Bell pairs as entanglement channels. A four-qubit joint measurement in the first case and two Bell measurements in the second are performed by the sender. Appropriate unitary operations on the qubits at the receiver’s end along with an ancilla qubit result in the perfect teleportation of the tripartite state. Analysis of the quantum circuits employed in these schemes reveal that in our technique the desired quantum tasks are achieved with lesser quantum cost, gate count and classical communication bits compared with other similar schemes.     

Remote two-qubit state creation and its robustness

We consider the problem of remote two-qubit state creation using the two-qubit excitation pure initial state of the sender. The communication line is based on the optimized boundary-controlled chain with two pairs of properly adjusted coupling constants. We show that the communication line can be characterized by a set of parameters independent of the initial state of the sender. These parameters are permanent attributes of a communication line and can be either calculated theoretically or measured in experiment. In particular, they determine the creatable subregion of the receiver’s state space. The creation of a particular state within the creatable region is achieved by a proper choice of the independent parameters of the sender’s initial state (control parameters) and reduces to the solvability of a certain system of algebraic equations. The creation of the two-qubit Werner state is considered as an example. We also study the effects of imperfections of the chain on the state creation.     

Hybrid entanglement concentration using quantum dot and microcavity coupled system

We present two hybrid entanglement concentration protocols based on quantum dots (QDs) and optical microcavity coupled systems. The system is theoretically analyzed and used for photon and electron hybrid entanglement generation. Also, the proposed system can be further used for parity check that allows a quantum nondemolition measurement on the spin parity. By performing parity check process on electron spins, the entangled state can be concentrated into maximally entangled state efficiently.     

Cyclic joint remote state preparation in noisy environment

We propose a scheme of cyclic joint remote state preparation for three sides, which takes advantage of three GHZ states to compose product state as quantum channel. Suppose there are six legitimate participants, says Alice, Bob, Charlie, David, Emma and Fred in the scheme. It can be shown that Alice and David can remotely prepare a single-qubit state on Bob’s side; meanwhile, Bob and Emma can remotely prepare a desired quantum state on Charlie’s side, and Charlie and Fred can also remotely prepare a single-qubit state on Alice’s side at the same time. Further, it can be achieved in the opposite direction of the cycle by changing the quantum channel. Based on it, we generalize this protocol to \(N (N\ge 3)\) sides utilizing three multi-qubit GHZ-type states as quantum channel. Therefore, the scheme can achieve cyclic joint remote state preparation, which remotely prepares N states in quantum network with N-party, simultaneously. In addition, we consider that the effect of amplitude-damping noise of the initial states is prepared in four different laboratory. Clearly, we use fidelity to describe how much information has been lost in the cyclic process. Our investigation about the effect of noise shows that the preparing of the initial state in different laboratories will affect the loss of information.     

Controlled remote state preparation protocols via AKLT states

In this paper, we proposed two controlled remote state preparation of an arbitrary single-qubit state schemes one for deterministic controlled remote state preparation the other for probabilistic controlled-joint remote state preparation with 2/3 probability. Both of them used the Affleck–Kennedy–Lieb–Tasaki (AKLT) state which consisted of bulk spin-1’s and two spin-1 \(/\) 2’s at the ends. Up to now, no RSP protocols using AKLT gapped ground states as a shared quantum resource had been presented thus far and Fan et al. showed the other AKLT property was that if we performed a Bell measurement on bulk, then a maximally entangled state would be shared by two ends. We utilized these properties to develop our controlled protocols.     

Analysis of optical parity gates of generating Bell state for quantum information and secure quantum communication via weak cross-Kerr nonlinearity under decoherence effect

We demonstrate the advantages of an optical parity gate using weak cross-Kerr nonlinearities (XKNLs), quantum bus (qubus) beams, and photon number resolving (PNR) measurement through our analysis, utilizing a master equation under the decoherence effect (occurred the dephasing and photon loss). To generate Bell states, parity gates based on quantum non-demolition measurement using XKNL are extensively employed in quantum information processing. When designing a parity gate via XKNL, the parity gate can be diversely constructed according to the measurement strategies. In practice, the interactions of XKNLs in optical fiber are inevitable under the decoherence effect. Thus, by our analysis of the decoherence effect, we show that the designed parity gate employing homodyne measurement would not be expected to provide reliable quantum operation. Furthermore, compared with a parity gate using a displacement operator and PNR measurement, we conclude there is experimental benefit from implementation of a parity gate via qubus beams and PNR measurement under the decoherence effect.     

基于广播机制的多方量子远程制备协议

量子态远程制备(RSP)是量子信息过程的一个重要分支。为了解决一个发送者向多个接收者同时制备相同量子态的问题,提出了基于广播机制的1对2三方量子态远程制备协议,并将其拓展到1对N多方量子态远程制备中。该协议使用GHZ态作为量子信道,通过构造两组特殊测量基,发送方进行两次多粒子投影测量,接收方根据测量结果进行幺正操作,最终实现1个发送者向多个接收者同时制备相同的粒子态。经分析,协议的这种广播制备模式可以适用于任意多个接收者的情形。     

Two-step entanglement concentration for arbitrary electronic cluster state

We present an efficient protocol for concentrating an arbitrary four-electron less-entangled cluster state into a maximally entangled cluster state. As a two-step entanglement concentration protocol (ECP), it only needs one pair of less-entangled cluster state, which makes this ECP more economical. With the help of electronic polarization beam splitter (PBS) and the charge detection, the whole concentration process is essentially the quantum nondemolition (QND) measurement. Therefore, the concentrated maximally entangled state can be remained for further application. Moreover, the discarded terms in some traditional ECPs can be reused to obtain a high success probability. It is feasible and useful in current one-way quantum computation.     

基于可重用的不对称三粒子纠缠态的量子秘密共享

本方案利用可重用的不对称三粒子纠缠态作为载体,发送方用控制非门操作将信息编码到载体上,接收方再利用控制非门操作解除纠缠,实现量子秘密共享。为了检测是否有窃听者,通过随机插入诱骗粒子的方法作窃听检测,随后进行二次检测窃听,使其安全性具有双重保证。分析表明方案能有效防止窃听,抵御纠缠欺骗攻击。     

Approximate conditional teleportation of a $$\varLambda $$-type three-level atomic state based on cavity QED method beyond Bell-state measurement

Inspiring from the scheme proposed in (Zheng in Phys Rev A 69:064,302 2004), our aim is to teleport an unknown qubit atomic state using the cavity QED method without using the explicit Bell-state measurement, and so the additional atom is not required. Two identical \(\varLambda \)-type three-level atoms are interacted separately and subsequently with a two-mode quantized cavity field where each mode is expressed with a single-photon field state. The interaction between atoms and field is well described via the Jaynes–Cummings model. It is then shown that how if the atomic detection results a particular state of atom 1, an unknown state can be appropriately teleported from atom 1 to atom 2. This teleportation procedure successfully leads to the high fidelity F (success probability \(P_g\)) in between \(69\%\lesssim F\lesssim 100\%\) (\(0.14\lesssim P_g\lesssim 0.56\)). At last, we illustrated that our scheme considerably improves similar previous proposals.     

Three-party remote state preparation schemes based on entanglement

By exploiting the entanglement correlation in quantum mechanics, two three-party remote state preparation (RSP) schemes are proposed. One is three-party remote preparation of a single-particle quantum state, and the other is three-party remote preparation of a two-particle entangled state. In the proposed schemes, the sender Alice knows the quantum states to be prepared, while the receivers Bob and Charlie do not know the quantum states; Alice performs measurement and unitary operations on her own particles with two three-particle GHZ states as the quantum channel. According to Alice’s measurement results, Bob and Charlie measure their own particles on the corresponding quantum measurement bases and perform unitary operations on the corresponding particles to reconstruct the quantum states, respectively. Compared with multiparty joint remote preparation and two-party RSP of a quantum state, the proposed schemes realize quantum multicast communication successfully, which enables Bob and Charlie to obtain the prepared quantum states simultaneously in the case of just knowing Alice’s measurement results, while Bob and Charlie do not know each other’s prepared quantum states. It is shown that only three classical bits are required for the two proposed RSP schemes when Bob and Alice introduce an auxiliary particle, respectively, and the proposed schemes are secure after the quantum channel authentication.     

Super-quantum correlation for SU(2) invariant state in $$4\otimes 2$$ system

We analytically evaluate the weak one-way deficit and super-quantum discord for a system composed of spin-3/2 and spin-1/2 subsystems possessing SU(2) symmetry. We also make a comparative study of the relationships among the quantum discord, one-way deficit, weak one-way deficit, and super-quantum discord for the SU(2) invariant state. It is shown that super-quantum discord via weak measurement is greater than that via von Neumann measurement. But weak one-way deficit is less than the one-way deficit. As a result, weak measurement do not always reveal more quantumness.     

On the role of the four-qubit state in two-qubit gate teleportation

The full analysis of quantum protocols requires the knowledge of the role of quantum states, bases of measurement and quantum gates involved. In what concerns the famous two-qubit quantum gate teleportation protocol, the role of the basis of measurement was considered in a recent work by Mendes and Ramos. In this work, we analyze the role of the four-qubit state used as resource. We show that the quantum two-qubit gate teleportation divides the set of pure four-qubit states in two classes. For one class, deterministic and probabilistic teleportation can be achieved, while for the other class, probabilistic remote two-qubit gate preparation is achieved.     

Minimal prime state filters and state radicals on state pseudo $${ }$$-algebras

The aim of this paper is the study of some classes of state filters of a state pseudo BL-algebra. The concepts of minimal prime state filter and of state hyperarchimedean pseudo BL-algebra are introduced and a characterization of a state hyperarchimedean pseudo BL-algebra is presented. Also, we define the notion of a state radical of a state filter of a state pseudo BL-algebra, we present a characterization of a state radical and some of its properties. The algebra of state radicals of a state pseudo BL-algebra is studied.     

Scheme for assisted cloning an unknown arbitrary three-qubit state

We present a scheme for perfect cloning or orthogonal complementing an unknown arbitrary three-qubit state with assistance. This cloning scheme is divided into two stages. In the first stage, the initial state can be teleported from a sender to a receiver probabilistically via three partially entangled states. In the second stage, the exact copying and orthogonal complementing of the three-qubit state can be created with unity fidelity in a probabilistic manner with the state preparer performing an appropriate tri-particle projective measurement. It is shown that for some special ensembles of the three-qubit state our assisted cloning scheme can be achieved exactly and deterministically.     

A type safe state abstraction for coordination in Java-like languages

The state of a concurrent object, intended as some abstraction over the values of the fields of the object, usually determines its coordination behavior. Therefore, state is always in the programmer’s mind, even though implicitly. We suggest a feature for Java-like languages, which makes the state of a concurrent object explicit and supports the expression of the object’s behavior depending on the state it is currently in. Namely, an object will be in one of the states declared in its class. The state determines the presence of fields and methods. State transition statements explicitly change the state of an object, and thus change the availability of fields and methods. When a thread calls a method which is declared in the object’s class but absent from its current state, it waits, until the state of the object changes to a state which does contain that method. This directly expresses coordination. We claim that this feature makes it easier to understand and develop concurrent programs, and substantiate our claim through the discussion of some popular examples of concurrent programs written using this feature.We develop a type and effect system, which guarantees that, during execution of a method invoked on a concurrent object ${\tt o}$ : (1) No attempt will be made to access fields not available in the current state of ${\tt o}$ , and (2) No method invoked on a receiver (syntactically) different from ${\tt this}$ may cause the invocation of a method on ${\tt o}$ . The latter guarantee helps to enforce the former and prevents a family of accidental violations of the intended coordination protocol.     

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.