Dynamic quantum secret sharing protocol based on two-particle transform of Bell states

To solve the problems of updating sub-secrets or secrets as well as adding or deleting agents in the quantum secret sharing protocol, we propose a two-particle transform of Bell states, and consequently present a novel dynamic quantum secret sharing protocol. The new protocol can not only resist some typical attacks, but also be more efficient than the existing protocols. Furthermore, we take advantage of the protocol to establish the dynamic secret sharing of a quantum state protocol for two-particle maximum entangled states.     

High-Dimensional Circular Quantum Secret Sharing Using Orbital Angular Momentum

Quantum secret sharing is to distribute secret message securely between multi-parties. Here exploiting orbital angular momentum (OAM) state of single photons as the information carrier, we propose a high-dimensional circular quantum secret sharing protocol which increases the channel capacity largely. In the proposed protocol, the secret message is split into two parts, and each encoded on the OAM state of single photons. The security of the protocol is guaranteed by the laws of non-cloning theorem. And the secret messages could not be recovered except that the two receivers collaborated with each other. Moreover, the proposed protocol could be extended into high-level quantum systems, and the enhanced security could be achieved.     

Comment on: “Efficient high-capacity quantum secret sharing with two-photon entanglement” [Phys. Lett. A 372 (2008) 1957]

In a recent Letter [F.G. Deng, X.H. Li, H.Y. Zhou, Phys. Lett. A 372 (2008) 1957], an efficient high-capacity quantum secret sharing scheme was proposed. However, in this comment, it is shown that the protocol does not complete the task of secret sharing well when the message sender uses the nonorthogonal entangled states as the quantum information carriers. Finally a feasible improvement of this quantum secret sharing protocol is proposed.     

Scheme for sharing classical information via tripartite entangled states

We investigate schemes for quantum secret sharing and quantum dense coding via tripartite entangled states. We present a scheme for sharing classical information via entanglement swapping using two tripartite entangled GHZ states. In order to throw light upon the security affairs of the quantum dense coding protocol, we also suggest a secure quantum dense coding scheme via W state by analogy with the theory of sharing information among involved users.     

Teleportation of Quantum States through Mixed Entangled Pairs

We describe a protocol for quantum state teleportation via mixed entangled pairs. With the help of an ancilla, near-perfect teleportation might be achieved. For pure entangled pairs, perfect teleportation might be achieved with a certain probability without using an ancilla. The protocol is generalized to teleportation of multiparticle states and quantum secret sharing.     

利用N粒子纠缠态的量子秘密共享

 为了高效实现多方之间的量子秘密共享,引入了一种纠缠度较高的N粒子纠缠态,并提出了利用该N粒子纠缠态在一方与（N-1）方之间形成共享秘密位串的方案.该方案在建立秘密位串的过程中,Alice对发送的粒子随机选择么正操作I和σx,并选择一部分粒子用于检测信道的安全|之后Alice根据（N-1）方选择的操作又选择了一部分粒子用于对参与者诚实度检测及信道安全检测.通过多次对窃听者的检测,很好地保证了信道的安全性及产生的秘密位串的可用性.最终在Alice及另外（N-1）方之间可形成n[1-(N-1)/2 N-1]/6个共享秘密位.     

基于N个有序纠缠光子对的量子机密共享方案

提出了一种基于N个有序纠缠光子对量子机密共享方案.用纠缠光子作为信息的载体,密钥管理者Alice将纠缠光子对分成两个序列,其中一个序列直接发送给合作者之一Bob,在确保第一个序列发送安全后,再对第二个序列进行编码,发送给另一个合作者Charlie.Bob和Charlie分别对他们所接收到的光子序列进行Bell基联合测量...     

Circular threshold quantum secret sharing

This paper proposes a circular threshold quantum secret sharing （TQSS） scheme with polarized single photons. A polarized single photon sequence runs circularly among any t or more of n parties and any t or more of n parties can reconstruct the secret key when they collaborate. It shows that entanglement is not necessary for quantum secret sharing. Moreover, the theoretic efficiency is improved to approach 100% as the single photons carrying the secret key are deterministically forwarded among any t or more of n parties, and each photon can carry one bit of information without quantum storage. This protocol is feasible with current technology.     

Quantum secret sharing between multiparty and multiparty with four states

A protocol of quantum secret sharing between multiparty and multiparty with four states was presented. It was shown that this protocol can nullify the Trojan horse attack with a multi-photon signal, the fake-signal attack with Einstein-Podolsky-Rosen pairs, the attack with single photons, and the attack with invisible photons. In addition, the upper bounds of the average success probabilities were given for dishonest agent eavesdropping encryption using the fake-signal attack with any two-particle entangled states. Supported by the National Natural Science Foundation of China (Grant No. 10671054), the Key Project of Science and Technology Research of Education Ministry of China (Grant No. 207011) and the Natural Science Foundation of Hebei Province, China (Grant Nos. A2005000140 and 07M006)     

Multiparty quantum secret sharing of secure direct communication using single photons

We propose a protocol for multiparty quantum secret sharing of secure direct communication using single photons. In this protocol, random phase shift operations instead of some special discrete unitary operations used usually are employed to realize the sharing controls. The security of this protocol with respect to various kinds of attacks is discussed. Due to the complete randomicity of the phase shift characterizing the unitary operations, the security of secret sharing is therefore enhanced.     

Quantum Secret Sharing with Two-Particle Entangled States

We present a new protocol for the quantum secret sharing （QSS） task among multiparties with two-particle entangled states. In our scheme, the secret is split among a number of participatlng partners and the reconstruction requires collaboration of all the authorized partners. Instead of multiparticle Greenberger-Horne-Zeillnger states, only two-particle entangled states are employed in this scheme. By local operations and individual measurements on either of the two entangled particles, each authorized partner obtains a sequence of secret bits shared with other authorized partners. This protocol can be experimentally realized using only linear optical elements and simple entanglement source. It is scalable in practice.     

Quantum Secret Sharing Based on Quantum Search Algorithm

Quantum secret sharing (QSS) and quantum search algorithm (QSA) are considered as two important but different research topics in quantum information science. This paper recognizes an important feature in the well-known Grover’s QSA and then applies it to propose a QSS protocol. In contrast to the existing QSA-based QSS protocols, the newly proposed protocol has the following two advantages: (1)?no quantum memory is required by the agents, whereas the agents in the existing QSA-based QSS protocols need long-term quantum memories to store their secret shadows; (2)?the agents can cooperate to recover the boss’s secret by using shadows in classical bits, whereas, the others have to combine their shadows in photons and perform a unitary operation on the retained photons. The proposed QSS protocol is also shown to be secure against eavesdroppers or malicious agents.     

Efficient high-capacity quantum secret sharing with two-photon entanglement

An efficient high-capacity quantum secret sharing scheme is proposed following some ideas in quantum dense coding with two-photon entanglement. The message sender, Alice prepares and measures the two-photon entangled states, and the two agents, Bob and Charlie code their information on their photons with four local unitary operations, which makes this scheme more convenient for the agents than others. This scheme has a high intrinsic efficiency for qubits and a high capacity.     

Universal Three-Party Quantum Secret Sharing Against Collective Noise

we present a robust and universal quantum secret sharing protocol with four-qubit decoherence-free (DF) states against collective noise. The transmission's safety is ensured by the nonorthogonality of the noiseless states traveling on the quantum channel. Although this scheme uses entangled states for encoding, only single-particle product measurements are required.     

Three-party quantum secret sharing of secure direct communication based on χ-type entangled states

Based on χ-type entangled states and the two-step protocol [Deng F G,Long G L and Liu X S 2003 Phys.Rev.A 68 042317],a quantum secret sharing protocol of secure direct communication based on χ-type entangled states |χ00 3214 is proposed.Using some interesting entanglement properties of this state,the agent entirety can directly obtain the secret message from the message sender only if they collaborate together.The security of the scheme is also discussed.     

Quantum Secret Sharing Protocol between Multiparty and Multiparty with Single Photons and Unitary Transformations

We propose a scheme of quantum secret sharing between Alice＇s group and Bob＇s group with single photons and unitary transformations. In the protocol, one member in Alice＇s group prepares a sequence of single photons in one of four different states, while other members directly encode their information on the sequence of single photons via unitary operations; after that, the last member sends the sequence of single photons to Bob＇s group. Then Bob＇s, except for the last one, do work similarly. Finally the last member in Bob＇s group measures the qubits. If the security of the quantum channel is guaranteed by some tests, then the qubit states sent by the last member of Alice＇s group can be used as key bits for secret sharing. It is shown that this scheme is safe.     

Information Leakage in Quantum Secret Sharing of Multi-Bits by an Entangled Six-Qubit State

In a recent paper Long et al. (J. Phys. A: Math. Theor. 45: 195303, 2012), a quantum secret sharing protocol was presented, in which the genuinely maximally entangled six-qubit states were used. According to the protocol, Alice could share three bits among three agents, which showed that it was more efficient than previous protocols. Here, we analyze it and point out that the information about the transmitted secret will be partly leaked out unknowingly. Through the classical public channel, 2/3 of Alice’s secret messages is leaked out to Bob₁ and Bob₂, and 1/3 secret messages is leaked out to Bob₃, respectively. This phenomenon should be strictly forbidden in a quantum secret sharing protocol.     

An enhancement on Shi et al.'s multiparty quantum secret sharing protocol

Recently, Shi et al. proposed a multiparty quantum secret sharing (QSS) using Bell states and Bell measurements. In their protocol, for sharing two classical bits, all parties have to possess two photons after entanglement swapping. This paper proposes an enhancement of Shi et al.'s protocol. Based on the idea that all parties (except dealer) possess two photons to share two classical bits, the qubit efficiency has further improved by removing the photons the dealer has to hold in Shi et al.'s protocol. Moreover, an insider attack is also prevented in the proposed scheme.     

Enhancing the security of quantum secret sharing against multiphoton attack

It is generally believed that nonorthogonal operations which can realize the state transformation between two nonorthogonal bases may ensure the security of many quantum communication protocols. However, in this paper, we present a powerful attack against quantum secret sharing protocols of these kinds. Applying entangled photons as fake signals, Eve can successfully steal the exact information without being revealed. We also give our effective modification to improve it. Under the suggested checking strategy, even to Eve's most general attack, it is robust and secure.     

Quantum secret sharing between <Emphasis Type="Italic">m</Emphasis>-party and <Emphasis Type="Italic">n</Emphasis>-party with six states

A quantum secret sharing scheme between an m-party group and an n-party group is proposed using three conjugate bases. A sequence of single photons, each of which is prepared in one of the six states, is used directly to encode classical information in the quantum secret sharing process. In this scheme, each of all m members in group 1 chooses randomly his/her own secret key individually and independently, and directly encodes his/her respective secret information on the states of single photons via unitary operations, then the last one sends 1/n of the resulting qubits to each member of group 2. By measuring their respective qubits, all members in group 2 share the secret information shared by all members in group 1. It renders impossible a Trojan horse attack with a multi-photon signal, a fake-signal attack with EPR pairs, an attack with single photons, and an attack with invisible photons. We give the upper bounds on the average success probabilities for dishonest agent eavesdropping encryption using the fake-signal attack with any two-particle entangled states. Supported by the National Natural Science Foundation of China (Grant No. 10671054), the Key Project of Science and Technology Research of Education Ministry of China (Grant No. 207011) and the Natural Science Foundation of Hebei Province, China (Grant Nos. 07M006 and F2009000311)