Mediated Semi‐Quantum Key Distribution Using Single Photons

A new mediated semi‐quantum key distribution (SQKD) protocol is proposed, allowing two classical participants to share a secret key with the help of an untrusted third party, who only needs to generate single photons and perform Bell measurements. This is the first work attempting to reduce the quantum overhead of the untrusted third party, which makes the mediated SQKD even more practical. The proposed protocol is shown to be free from several well‐known attacks.     

Teleportation of a Pure EPR State via GHZ-like State

This study proposes a novel teleportation using the GHZ-like state \frac12(|001?+|010?+|100?+|111?)\frac{1}{2}(|001\rangle+|010\rangle+|100\rangle+|111\rangle), in which a pure EPR state α|01〉+β|10〉 can be perfectly teleported. Furthermore, the teleportation scheme is applied to construct a quantum secret state sharing (QSSS) protocol.     

Improvement of “Novel Multiparty Quantum Key Agreement Protocol with GHZ States”

Quantum key agreement (QKA) protocol is a method for negotiating a fair and secure key among mutually untrusted participants. Recently, Xu et al. (Quantum Inf. Process. 13:2587–2594, 2014) proposed a multi-party QKA protocol based on Greenberger-Horne-Zeilinger (GHZ) states. However, this study points out that Xu et al.’s protocol cannot provide the fairness property. That is, the last involved participant in the protocol can manipulate the final shared secret key without being detected by the other participants. Moreover, according to Yu et al.’s research (2015), Xu et al.’s protocol cannot avoid the public discussion attack too. To avoid these weaknesses, an improved QKA protocol is proposed.     

Man-in-the-Middle Attack on “Quantum Dialogue with Authentication Based on Bell States”

Recently, Shen et al. (Int. J. Theor. Phys. doi:10.1007/s10773-012-1276-6, 2012) proposed a quantum dialogue with authentication protocol based on Bell states. This study points out that Shen et al.’s protocol suffers from a man-in-the-middle attack. By manipulating the photons and classical information transmitted between two communicants, an attacker can not only pass the mutual identity authentication, but also obtain their secret messages and new authentication keys without being detected.     

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.     

Enhancement of GAO's Multiparty Quantum SecretSharing

A multiparty quantum secret sharing (MQSS) protocol with two-photon three-dimensional Bell states was proposed by Gao [Commun. Theor. Phys.52 (2009) 421] recently. This study points out that the performance of Gao's protocol can be much improved by using the technique of decoy single photons
and carefully modifying the protocol to remove some unnecessary unitary operations, devices, and transmissions.     

Revisiting Deng et al.’s Multiparty Quantum Secret Sharing Protocol

The multiparty quantum secret sharing protocol [Deng et al. in Chin. Phys. Lett. 23: 1084–1087, 2006] is revisited in this study. It is found that the performance of Deng et al.’s protocol can be much improved by using the techniques of block-transmission and decoy single photons. As a result, the qubit efficiency is improved 2.4 times and only one classical communication, a public discussion, and two quantum communications between each agent and the secret holder are needed rather than n classical communications, n public discussions, and \frac3n2\frac{3n}{2} quantum communications required in the original scheme.     

Deterministic quantum communication using the symmetric W state

This study proposes a new coding function for the symmetric W state.Based on the new coding function,a theoretical protocol of deterministic quantum communication(DQC) is proposed.The sender can use the proposed coding function to encode his/her message,and the receiver can perform the imperfect Bell measurement to obtain the sender’s message.In comparison to the existing DQC protocols that also use the W class state,the proposed protocol is more efcient and also more practical within today’s technology.Moreover,the security of this protocol is analyzed to show that any eavesdropper will be detected with a very high probability under both the ideal and the noisy quantum channel.     

Semi-quantum Key Distribution Robust Against Combined Collective Noise

This paper first proposes a new coding function for the six-qubit decoherence-free states that can resist both types of collective noise (i.e., dephasing and rotation noise) simultaneously. Subsequently, based on the coding function, a semi-quantum key distribution (SQKD) protocol is designed such that a sender with strong quantum capabilities can send a key to a classical receiver who can merely perform classical operations. This is the first SQKD protocol that can resist the combined collective noise. Analyses show that this protocol is secure and effective.