We present a scheme for probabilistic teleportation via a non-maximally entangled GHZ state. Quantum teleportation will succeed with a calculable probability. The teleportation process requires the sender to make a generalized Bell state measurement, the cooperator to perform a generalized X basis measurement, and the receiver to perform a collective unitary transformation and to make a measurement on an auxiliary particle. The success probability of the teleportation is given. We also obtain the maximum of the success probability of the teleportation. probabilistic teleportation, non-maximally entangled GHZ state, generalized measurement, success probability Citation: Yan F L, Yan T. Probabilistic teleportation via a non-maximally entangled GHZ state. Chinese Sci Bull, 2010, 55: 902−906, Quantum teleportation, which allows the transportation of an unknown state from a sender Alice to a spatially distant receiver Bob with the aid of classical communication and a previously shared entanglement is regarded as one of the most striking results of quantum information theory [1], and has played an important role in the development of quantum computation and quantum communication [2-9]. The original protocol of Bennett et al. [2]involved the teleportation of an arbitrary state of a qubit via an Einstein-Podolsky-Rosen (EPR) pair with the transmission of two bits of classical information from Alice to Bob. Here Alice knows neither the state to be teleported nor the location of the intended receiver, Bob. Bennett et al. also presented a protocol for teleporting an unknown state of a qubit by using a maximally entangled state in d×d dimensional Hilbert space and by sending 2log 2 d bits of classical information.Since then, quantum teleportation has undergone great development [10-23] and has been experimentally demonstrated by several groups [24][25][26][27]. It has also been generalized to a more general situation, where two parties may start not with a set of pure entangled states, but with a noisy quantum channel. In order to arrive at their goal of transmitting an unknown quantum state over this noisy quantum channel, they can, in principle, use an error correcting code [28], or alternatively they can share the entanglement through this noisy channel and then subsequently use teleportation [29].Quantum teleportation is also possible for infinite dimensional Hilbert spaces, for example in position-momentum space with continuously variable states. This is an example of what is known as continuously variable quantum teleportation [10][11][12].Somewhat later, Karlsson and Bourennane put forward the so-called controlled quantum teleportation protocol [14][15][16][17][18][19]. In this protocol, one can perfectly transport an unknown state from one place to another via a previously shared Greenberger-Horne-Zeilinger (GHZ) state using local operations and classical communications under the control of a third party. The signal state cannot be transmitted unless the third party gives permission. Controlled quantum teleportation ...

We present a quantum key distribution protocol based on four-level particle entanglement. Furthermore, a controlled quantum key distribution protocol is proposed using three four-level particles. We show that the two protocols are secure. quantum key distribution, four-level particles, entanglement Citation:Yan T, Yan F L. Quantum key distribution using four-level particles. Chinese Sci Bull, 2011Bull, , 56: 24−28, doi: 10.1007 Quantum key distribution (QKD) is one of the most important branches of quantum cryptography, and plays an important role in perfectly secure communication between two parties. In classic cryptography, there is nothing to prevent an eavesdropper from monitoring the key distribution channel without being detected by legitimate users. In quantum cryptography, the principle of quantum mechanics was introduced to ensure the security of the key distribution channel. Since the seminal work of Bennett [6] put forward a QKD protocol using the block transmission method to ensure the security of the key distribution channel. In this paper, we suggest a QKD protocol based on fourlevel particle entanglement. Then a controlled quantum key distribution protocol is proposed using three entangled four-level particles as the quantum key distribution channel. The security of the key distribution channels is guaranteed using the block transmission method proposed by Long et al. [6].