Tripartite Arbitrary Two-Qutrit Quantum State Sharing

A tripartite scheme for securely sharing an arbitrary unknown two-qutrit state is proposed, where two generalized Greenberger-Horne-Zeilinger （GHZ） states serve as the quantum channel linking the three legitimate parties. The quantum information （i.e., the arbitrary unknown two-qutrit state） from the sender can be split in such a way that it can be reconstructed deterministically by any agent via a proper unitary operation provided that both agents collaborates together. Moreover, the generalization of the tripartite scheme to more-party case is also outlined.     

Remote Three-Party Quantum State Sharing Based on Three-Atom Entangled States Assisted by Cavity QED and Flying Qubits

We present a remote three-party quantum state sharing (QSTS) schemewith three-atom Greenberger-Horne-Zeilinger (GHZ) states assisted bycavity QED and flying qubits. It exploits some photons to act as the flying qubits for setting up the quantum channel securely with three-atom systems in a GHZ state, which maybe make this remote QSTS scheme more practical than some other schemes based on atom systems only or ion-trap systems as photons interact with their environments weakly. The coherence of the stationary atom qubits in cavities provides the convenience for the parties in QSTS to check eavesdropping, different from entangled photon systems. Moreover, the present scheme works in a collective-noise condition and it may be more practical than others in applications in future.     

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.     

Scheme for Quantum Dense Coding with Secret Sharing in Cavity QED

Quantum dense coding （QDC） is a process originally proposed to send two classical bits information from a sender to a receiver by sending only one qubit. Our scheme of QDC is proposed following some ideas on secret sharing with entanglement in cavity QED. Based on the theory of secret sharing the QDC process can be more secure.     

Controlled Remote Preparation of a Two-Qubit State via an Asymmetric Quantum Channel

I present a new scheme for probabilistic remote preparation of a general two-qubit state from a sender to either of two receivers. The quantum channel is composed of a partial entangled tripartite Greenberger-Horne-Zeilinger (GHZ) state and a W-type state. I try to realize the remote two-qubit preparation by using the usual projective measurement and the method of positive operator-valued measure, respectively. The corresponding success probabilities of the scheme with different methods as well as the total classical communicationcost required in this scheme are also calculated.     

Multi-Party Quantum Secret Sharing Based on GHZ State

In this paper, we propose an efficient multi-party quantum secret sharing scheme based on GHZ entangled state. The participants in this scheme are divided into two groups, and share secrets as a group. There is no need to exchange any measurement information between the two groups, reducing the security problems caused by the communication process. Each participant holds one particle from each GHZ state; it can be found that the particles of each GHZ state are related after measuring them, and the eavesdropping detection can detect external attacks based on this characteristic. Furthermore, since the participants within the two groups encode the measured particles, they can recover the same secrets. Security analysis shows that the protocol can resist the intercept-and-resend attack and entanglement measurement attack, and the simulation results show that the probability of an external attacker being detected is proportional to the amount of information he can obtain. Compared with the existing protocols, this proposed protocol is more secure, has less quantum resources and is more practical.     

基于腔QED技术的量子信息的多方秘密共享

提出了一个基于腔QED技术的量子信息的多方秘密共享方案.该方案不受腔的衰减和热场的影响,并考虑了几种可能偷听下的安全性.     

Scheme for Implementing Assisted Cloning of an Unknown d-Dimension Equatorial Quantum State by Remote State Preparation

In this paper, we propose a protocol that can produce perfect copy of an unknown d-dimensional equatorial quantum state with assistance from a state preparer. In this protocol, the maximally and non-maximally entangled bipartite d-dimensional of states are used as the quantum channels, respectively. The first stage of the protocol requires usual teleportation. In the second stage of the protocol, with the assistance of the preparer, the perfect copy of an original unknown state can be produced.     

Generalized Quantum Two-Qutrit-State Splitting

A three-party scheme for splitting an arbitrary unknown two-qutrit state is proposed, where two nonmaximally-entangled three-qutrit states are taken as the quantum channel among three parties. With the sender＇s help, if and only if both receivers collaborate together, they can securely share the quantum state in a probabilistic way by introducing an ancilla qutrit and performing appropriate unitary operations. The relation between the success probability and coefficients characterizing the quantum channel is revealed. The security of the present scheme is analyzed and confirmed. Moreover, the generalization of the three-party scheme to more-party case is also sketched.     

Generalized Quantum Two-Qutrit-State Splitting

A three-party scheme for splitting an arbitrary unknown two-qutrit state is proposed, where two non-maximally-entangled three-qutrit states are taken as the quantum channel among three parties. With the sender's help, if and only if both receivers collaborate together, they can securely share the quantum state in a probabilistic way by introducing an ancilla qutrit and performing appropriate unitary operations. The relation between the success probability and coefficients characterizing the quantum channel is revealed. The security of the present scheme is analyzed and confirmed. Moreover, the generalization of the three-party scheme to more-party case is also sketched.     

Quantum Distributed Ballot Scheme Based on Greenberger-Horne-Zeilinger State

Motivated by the complementary relations of the Greenberger-Horne-Zeilinger （GHZ） entangled tripletparticle states, a novel way of realizing quantum distributed ballot scheme is proposed. The ballot information is encoded by local operations performed on the particles of entangled GHZ triplet states, which ensures the security of the present scheme. In order to guarantee the security of this scheme, the checking phase is designed in detail on the basis of the entangled GHZ triplet state. The analysis shows the security of the proposed scheme.     

A Theoretical Scheme for Multiparty Multi-particle State Sharing

A theoretical scheme for multiparty multi-particle state sharing is proposed. After she introduces auxiliary particles and Einstein-Podolsky-Rosen （EPIC） pairs, the sender （Alice） performs Hadamard （14） gate operations and Controlled-NOT （CNOT） gate operations on them. Subsequently, the sender leaves one particle sequence and distributes the rest particles to the other participants. And then, the sender makes Bell-state measurements on her particles and publishes the measurement outcomes via the classical channel to realize the quantum state sharing among the others. Only the simple operations are used to realize quantum state sharing. The sender may increase or decrease the number of the participants by changing the number of the auxiliary particles.     

Quantum Distributed Ballot Scheme Based on Greenberger-Horne-Zeilinger State

Motivated by the complementary relations of theGreenberger-Horne-Zeilinger (GHZ) entangled triplet-particle states,a novel way of realizing quantum distributed ballot scheme isproposed. The ballot information is encoded by local operationsperformed on the particles of entangled GHZ triplet states, whichensures the security of the present scheme. In order to guaranteethe security of this scheme, the checking phase is designed indetail on the basis of the entangled GHZ triplet state. The analysisshows the security of the proposed scheme.     

Improved Multipartite Quantum Secret Sharing Protocol Using PresharedGreenberger-Horne-Zeilinger States

Inspired by the protocol presented by Bagherinezhad and Karimipour [Phys. Rev. A 67 (2003) 044302], which will be shown to be insecure, we present a multipartite quantum secret sharing protocol using reusable Greenberger-Horne-Zeilinger (GHZ) states. This protocol is robust against eavesdropping and could be used for the circumstance of many parties.     

An Efficient Scheme for Multiparty Multi-particle State Sharing

We present an efficient scheme for sharing an arbitrary m-qubit state with n agents. In our scheme, the sender Alice first shares m Bell states with the agent Bob, who is designated to recover the original m-qubit state. Furthermore, Alice introduces n- 1 auxiliary particles in the initial state ｜0）, applies Hadamard （H） gate and Controlled-Not （CNOT） gate operations on the particles, which make them entangled with one of m particle pairs in Bell states, and then sends them to the controllers （i.e., other n - 1 agents）, where each controller only holds one particle in hand. After Alice performing m Bell-basis measurements and each controller a single-particle measurement, the recover Bob can obtain the original unknown quantum state by applying the corresponding local unitary operations on his particles. Its intrinsic efficiency for qubits approaches 100%, and the total efficiency really approaches the maximal value.     

Quantum Generalized Measurement and Deterministic Generation of Maximum Entangled Pure State

We propose the concept of the quantum generalized projector measurcment (QGPM) for finite-dimensional quantum systems by studying the quantum generalized measurement. This research reveals a distinguished property of this quantum generalized measurement: no matter what the system state is prior to the measurement and what the result of the measurement occurs, the state of the system after the measurement can be collapsed into any specified pure state, i.e., the state of quantum system can be deterministically reduced to any specified pure state just by a single QGPM. Subsequently, QGPM can be used to deterministically generate the maximum entangled pure state for quantum systems. We give three concrete theoretic schemes of generating the maximum quantum entangled pure stazes for two 2-level particles, three 2-level particles and two 3-level particles, respectively.     

Quantum Generalized Measurement and Deterministic Generation of Maximum Entangled Pure State

We propose the concept of the quantum generalized projector measurement （QGPM） for finite-dimensional quantum systems by studying the quantum generalized measurement. This research reveals a distinguished property of this quantum generalized measurement： no matter what the system state is prior to the measurement and what the result of the measurement occurs, the state of the system after the measurement can be collapsed into any specified pure state, i.e., the state of quantum system can be deterministically reduced to any specified pure state just by a single QGPM. Subsequently. QGPM can be used to deterministically generate the maximum entangled pure state for quantum systems. We give three concrete theoretic schemes of generating the maximum quantum entangled pure states for two 2-Jevel particles, three 2-level particles and two 3-Jevel particles, respectively.     

Simplified Four-Qubit Cluster State for Splitting Arbitrary Single-Qubit Information＊

The simplified four-qubit cluster state （i.e., （｜0000〉 ＋ ｜0011〉 ＋ ｜1100〉 -｜1111〉）/2） is explored for splitting an arbitrary single-qubit quantum information （QI）. Various feasible distributions of the four qubits among the Q,I sender and receivers for tri-splitting or hi-splitting are found out. For the distribution representations the corresponding splitting schemes and their LOCCs （local operation and classical communication） are presented amply while others are mentioned concisely.     

Scheme for Probabilistic Remotely Preparing a d-Dimensional Equatorial Quantum State

We present a scheme for probabilistic remote preparation of a d-dimensional equatorial quantum state. In the scheme, a bipartite d-dimensional partial entangled state is used as the quantum channel, and the single-qudit projective measurement and appropriate unitary transformation are needed. As a special, the remote preparation in three dimension is studied. The project supported Natural Science Foundation of Education Bureau of Jiangsu Province of China (Grant No 05 KJD 140035 and 06 KJD 520027).