Asymmetric bidirectional quantum teleportation via six-qubit partially entangled state

In this paper, an asymmetric bidirectional controlled quantum teleportation via a six-qubit partially entangled state is given, in which Alice wants to transmit a two-qubit entangled state to Bob and Bob wants to transmit a single-qubit state to Alice on the same time. Although the six-qubit state as quantum channel is partially entangled, the teleportation is implemented deterministically. Furthermore, only Bell-state measurements, single-qubit measurements and some unitary operations are needed in the scheme.

High success perfect transmission of 1-qubit information using purposefully delayed sharing of non-maximally entangled 2-qubit resource and repeated generalized Bell-state measurements

We propose a new scheme in which perfect transmission of 1-qubit information is achieved with high success using purposefully delayed sharing of non-maximally entangled 2-qubit resource and repeated generalized Bell-state measurements (GBSM). Alice possesses initially all qubits and she makes repeated GBSM on the pair of qubits, consisting of (1) the qubit of information state and (2) one of the two entangled resource qubits (taken alternately) until transmission with perfect fidelity is indicated. Alice then sends to Bob, the qubit not used in the last GBSM and also the result of this GBSM and Bob applies a suitable unitary transformation to replicate exactly the information state. Continued probabilistic transmission with unit fidelity is achieved by changing continuously the generalized Bell basis and also the pair of measured qubits of the collapsed states. We calculate the success probability up to the third repeated attempt of GBSM and plot it with concurrence of the entangled resource state. We also discuss the maximal average fidelity.

Multi-Party Quantum Summation Based on Quantum Teleportation

We present a secure multi-party quantum summation protocol based on quantum teleportation, in which a malicious, but non-collusive, third party (TP) helps compute the summation. In our protocol, TP is in charge of entanglement distribution and Bell states are shared between participants. Users encode the qubits in their hand according to their private bits and perform Bell-state measurements. After obtaining participants’ measurement results, TP can figure out the summation. The participants do not need to send their encoded states to others, and the protocol is therefore congenitally free from Trojan horse attacks. In addition, our protocol can be made secure against loss errors, because the entanglement distribution occurs only once at the beginning of our protocol. We show that our protocol is secure against attacks by the participants as well as the outsiders.

Dense quantum communication using single- and two-particle operations on six-particle cluster state

Theory of controlled tripartite quantum dense coding for the transmission of four-binary bits between two distinct locations is presented. The entanglement resource for this transmission is provided by a six-qubit cluster state. Theoretical detail of an encoder that can encode sixteen different operations and a four-bit binary decoder required for this transmission is discussed. We show that in the absence of availability of any four-state analyzer decoding can be reduced to single-particle and two-particle Bell-state measurements ( BSM ). In our scheme, Bell-state measurements ( BSM ) performed during decoding, result in Bell-pairs, which along with single-particle projections are used to unambiguously discriminate all sixteen encoding operations. Proposed experiment to verify theory of tripartite quantum dense coding scheme, using photonic entanglement, is also briefly discussed. Success probability of the scheme is determined. In addition, long-distance implementation of this tripartite quantum dense coding scheme is discussed. Fault-tolerant quantum repeaters used in this long-distance scheme are based on quantum errorcorrection, which is achieved with the aid of Calderbank-Shor-Steane ( CSS ) encoding.

Information Delay Protocol Using the Bell State Measurement

in this paper we present an information delay protocol using quantum the Bell state measurement. By sharing EPR(Einstain-Rosen-Podolsky) pairs and perform Control-NOT operation and the Bell state measurements, one person can give the other person some information which cannot be read until he or she lets the latter do. The unconditional security of the protocol is guaranteed by the laws of quantum physics. When the one decides to let the other get the information, he or she need only to send some dictates through a public classical channel. So the protocol is easier to carry out and more robust in practice.

TRANSFORMATION FROM PROBABILISTIC CHANNEL TO DETERMINISTIC CHANNEL BASED ON EIGHT-QUBIT QUANTUM CHANNEL

In physics experiments, it is very difficult to realize directly using high-dimensional unitary operations. In order to decrease or avoid the shortage during the teleportation process based on probabilistic channel, we propose a new scheme to reconstruct a deterministic teleportation eight-qubit channel using Bell-state measurements based on the probabilistic channel, which replaces high-dimensional unitary operations. In our scheme, a new quantum channel without alterable parameters replaces the general quantum channel with parameters as probabilistic teleportation. It shows that if we choose an eight-qubit probabilistic channel to construct deterministic channel, the relevant parameters of the eight-qubit probabilistic channel can be avoided. Thus, in quantum teleportation process, quantum channel can be chosen as a deterministic channel. This shows that our scheme makes real experiments more suitable.