Deterministic Teleportation Channel Using Bell State Measurements Only

Teleportation schemes based on probabilistic channels usually rely heavily on the implementation of high-dimensional unitary operations. Since high-dimensional unitary operations are very difficult to directly implement in physics experiments, methods are used to avoid high-dimensional unitary operations during the teleportation process. This paper describes how to construct a deterministic teleportation channel and a control channel using Bell state measurements only instead of high-dimensional unitary operations. Here, the general four-particle and five-particle class states are used as the potential quantum channel and the control channel for deterministic teleportation even without access to the relevant parameters. The results show that this scheme makes physical realization of teleportation more reasonable.

Teleportation of Two-Particle Entangled State via Cluster State

In this paper, two schemes for teleporting an unknown two-particle entangled state from the sender （Alice） to the receiver （Bob） via a four-particle entangled cluster state are proposed. In these two schemes, the unknown twoparticle entangled state can be teleported perfectly. The successful probabilities and fidelities of the schemes can reach unity.

Probabilistic Teleportation of Two—Particle State of General Formation

A scheme for probabilistic teleporting an unknown two-particle state of general formation by partly pure entangled four-particle state is proposed. It is shown that after performing two Bell state measurements, proper unitary transformation and the measurement on an auxiliary qubit, the unknown two-particle state of general formation, which was destroyed at one place, can be reconstructed at another place with certain probability.

Controlled Teleportation of an Unknown N-qubit Entangled GHZ State

A scheme for controlled teleportation of an unknown N-qubit entangled GHZ state from the sender Alice to the distant receiver Bob is proposed. And m-qubit GHZ state is sufficient for the task of control by m spatially- separated supervisors. Conditioned on the local operations executed by all participants, Bob can faithfully restore the original state by performing relevant unitary transformations with the aid of some classical message about measurement results. Anyone＇s absence will absolutely lead to the failure of teleportation.

Quantum Secure Direct Communication and Quantum Sealed-Bid Auction with EPR Pairs

I present a new protocol for three-party quantum secure direct communication （QSDC） with a set of ordered M Einstein-Podolsky-Rosen （EPR） pairs. In the scheme, by performing two unitary operations and Bell state measurements, it is shown that the three legitimate parties can exchange their respective secret message simultaneously. Then I modify it for an experimentally feasible and secure quantum sealed-bid auction （QSBD） protocol. Furthermore, I also analyze th^ecurity of the protocol, and the scheme is proven to be secure against the intercept-and-resend attack, the disturbancb attack and the entangled-and-measure attack.

Measurement-device-independent one-step quantum secure direct communication

The one-step quantum secure direct communication(QSDC)(Sci.Bull.67,367(2022))can effectively simplify QSDC’s operation and reduce message loss.For enhancing its security under practical experimental condition,we propose two measurement-device-independent(MDI)one-step QSDC protocols,which can resist all possible attacks from imperfect measurement devices.In both protocols,the communication parties prepare identical polarization-spatial-mode two-photon hyperentangled states and construct the hyperentanglement channel by hyperentanglement swapping.The first MDI one-step QSDC protocol adopts the nonlinear-optical complete hyperentanglement Bell state measurement(HBSM)to construct the hyperentanglement channel,while the second protocol adopts the linear-optical partial HBSM.Then,the parties encode the photons in the polarization degree of freedom and send them to the third party for the hyperentanglementassisted complete polarization Bell state measurement.Both protocols are unconditionally secure in theory.The simulation results show the MDI one-step QSDC protocol with complete HBSM attains the maximal communication distance of about354 km.Our MDI one-step QSDC protocols may have potential applications in the future quantum secure communication field.

High-capacity device-independent quantum secure direct communication based on hyper-encoding

Quantum secure direct communication(QSDC)can directly transmit secret messages through quantum channel without keys.Device-independent(DI)QSDC guarantees the message security relying only on the observation of the Bell-inequality violation,but not on any detailed description or trust of the devices'inner workings.Compared with conventional QSDC,DI-QSDC has relatively low secret message capacity.To increase DI-QSDC's secret messages capacity,we propose a high-capacity DI-QSDC protocol based on the hyper-encoding technique.The total message leakage rate of our DI-QSDC protocol only relies on the most robust degree of freedom.We provide the numerical simulation of its secret message capacity altered with the communication distance.Our work serves as an important step toward thefurther development of DI-QSDC systems.

Probabilistic Teleportation of Three-Atom State via Five-Atom Cluster State

A scheme for probabilistic teleportation of an unknown three-atom entangled state via a five-atom non- maximally entangled cluster state as quantum channel is proposed. In this scheme, the sender performs two Bell state and a single-atom measurements on the atoms, the receiver can reconstruct the original state with a certain probability by introducing an auxiliary atom and operating appropriate unitary transformations and controlled-not （C-not） operations according to the sender Alice＇s measurement results. As a result, the probability of successful teleportation is determined by the smallest two of the coefficients＇ absolute values of the cluster state. The considerable advantage of our scheme is that we employ a non-maximally entangled cluster state as quantum channel in the scheme, which can greatly reduce the amount of entanglement resources and need less classical bits. If we employ a maximally entangled cluster state as quantum channel, the probabilistic teleportation scheme becomes usual teleportation, the successful probability being 100%.

Experimental long-distance quantum secure direct communication

Quantum secure direct communication(QSDC) is an important quantum communication branch, which realizes the secure information transmission directly without encryption and decryption processes.Recently, two table-top experiments have demonstrated the principle of QSDC. Here, we report the first long-distance QSDC experiment, including the security test, information encoding, fiber transmission and decoding. After the fiber transmission of 0.5 km, quantum state fidelities of the two polarization entangled Bell states are 91% and 88%, respectively, which are used for information coding. We theoretically analyze the performance of the QSDC system based on current optical communication technologies,showing that QSDC over fiber links of several tens kilometers could be expected. It demonstrates the potential of long-distance QSDC and supports its future applications on quantum communication networks.