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The proposed quantum secret sharing protocol in this article conveys n bit secret messages from the sender to the n receivers making use of a secure direct communication. In this protocol, all users work together to access their secrets. As a result, the security of the proposed protocol is high. The channel used in this design is an entangled 2n-qubit state. The efficiency of this design has been compared with other designs and it turns out that the efficiency of the proposed protocol is equal to that of the best designs. We demonstrate that this protocol is more efficient than the only n-user confidential subscription plan. Also, all stages of the design in a noisy space have been examined.

It has been shown that AdS/CFT correspondence may be realized between some AdS-like cosmological space and CFT living on the boundary. By extending such works we studied the role of R2 term in the corrected action to the thermodynamic quantities, particularly by adding a boundary counterterms to the gravitational action and considering an AdS-like cosmological space. With such HD (higher derivative) terms and metric we calculated the free energy, as a function of N2T4 times 3/2(1 − 1/N2), that is comparable with perturbative result followed from boundary QFT. In fact the difference between the results obtained from AdS-like cosmological space and the results obtained from strong coupling limit of ℵ = 4 SCFT, by taking into account next to leading term in large N expansion, is just a 3/2 factor. Higher derivative term contributions also appear in entropy and energy via the redefinition of gravitation constant. We explicitly identify higher order counterterms effect in energy as a constant term namely E0. This value can be interpreted as the Casimir energy, so that, there is a full and perfect match between QFT and gravitational action when both R2 term and boundary counterterms are considered. So we can claim that our results have assured us that there is a good fit between AdS-like cosmological space and ℵ = 4 SU(N) super Yang-Mills quantum theory.

A new protocol of bidirectional quantum teleportation (BQT) is proposed in which the users can transmit a class of n-qubit state to each other simultaneously, by using (2n + 2)-qubit entangled states as quantum channel. The state of the art approaches can only transmit two-qubit states in each round. This scheme is based on control-not operation, single-qubit measurements and appropriate single-qubit unitary operations. It is shown that the protocol is secure in preparation phase.

In this paper, a new scheme of bidirectional quantum teleportation (BQT) making use of an eight-qubit entangled state as the quantum channel is presented. This scheme is the first protocol without controller by which the users can teleport an arbitrary two-qubit state to each other simultaneously. This protocol is based on the ControlledNOT operation, appropriate single-qubit unitary operations and single-qubit measurement in the Z-basis and X-basis.

In this paper, we derive the non-Markovian stochastic equation of motion (SEM) and master equations (MEs) for the open quantum system by using the non-Markovian stochastic Schrodinger equations (SSEs) for the quadrature unraveling in linear and nonlinear cases. The SSEs for quadrature unraveling arise as a special case of a quantum system. Also we derive the Markovian SEM and ME by using linear and nonlinear Ito SSEs for the measurement probabilities. In linear non-Markovian case, we calculate the convolutionless linear quadrature non-Markovian SEM and ME. We take advantage from example and show that corresponding theory.