Applications of quantum cryptographic switch: Various tasks related to controlled quantum communication can be performed using Bell states and permutation of particles

Recently, several aspects of controlled quantum communication (e.g., bidirectional controlled state teleportation, controlled quantum secure direct communication, controlled quantum dialogue, etc.) have been studied using $n$-qubit ($n\geq3$) entanglement. Specially, a large number of schemes for bidirectional controlled state teleportation are proposed using $m$-qubit entanglement ($m\in\{5,6,7\}$). Here, we propose a set of protocols to illustrate that it is possible to realize all these tasks related to controlled quantum communication using only Bell states and permutation of particles (PoP). As the generation and maintenance of a Bell state is much easier than a multi-partite entanglement, the proposed strategy has a clear advantage over the existing proposals. Further, it is shown that all the schemes proposed here may be viewed as applications of the concept of quantum cryptographic switch which was recently introduced by some of us. The performances of the proposed protocols as subjected to the amplitude damping and phase damping noise on the channels are also discussed.Comment: 12 pages, 3 figure

Design and experimental realization of an optimal scheme for teleportion of an nn-qubit quantum state

An explicit scheme (quantum circuit) is designed for the teleportation of an $n$-qubit quantum state. It is established that the proposed scheme requires an optimal amount of quantum resources, whereas larger amount of quantum resources has been used in a large number of recently reported teleportation schemes for the quantum states which can be viewed as special cases of the general $n$-qubit state considered here. A trade off between our knowledge about the quantum state to be teleported and the amount of quantum resources required for the same is observed. A proof of principle experimental realization of the proposed scheme (for a 2-qubit state) is also performed using 5-qubit superconductivity-based IBM quantum computer. Experimental results show that the state has been teleported with high fidelity. Relevance of the proposed teleportation scheme has also been discussed in the context of controlled, bidirectional, and bidirectional-controlled state teleportation.Comment: 11 pages 4 figure

A General Method for Selecting Quantum Channel for Bidirectional Controlled State Teleportation and Other Schemes of Controlled Quantum Communication

Recently, a large number of protocols for bidirectional controlled state teleportation (BCST) have been proposed using $n$-qubit entangled states ($n\in\{5,6,7\}$) as quantum channel. Here, we propose a general method of selecting multi-qubit $(n>4)$ quantum channels suitable for BCST and show that all the channels used in the existing protocols of BCST can be obtained using the proposed method. Further, it is shown that the quantum channels used in the existing protocols of BCST forms only a negligibly small subset of the set of all the quantum channels that can be constructed using the proposed method to implement BCST. It is also noted that all these quantum channels are also suitable for controlled bidirectional remote state preparation (CBRSP). Following the same logic, methods for selecting quantum channels for other controlled quantum communication tasks, such as controlled bidirectional joint remote state preparation (CJBRSP) and controlled quantum dialogue, are also provided.Comment: 8 pages, no figur

Comment on "Quantum Teleportation of Eight-Qubit State via Six-Qubit Cluster State"

Recently, Zhao et al., (Int. J. Theor. Phys. 57, 516-522 (2018)) have proposed a scheme for quantum teleportation of an eight-qubit quantum state using a six qubit cluster state. In this comment, it's shown that the quantum resource (multi-partite entangled state used as the quantum channel) used by Zhao et al., is excessively high and the task can be performed using any two Bell states as the task can be reduced to the teleportation of an arbitrary two qubit state. Further, a trivial conceptual mistake made by Zhao et al., in the description of the quantum channel has been pointed out. It's also mentioned that recently a trend of proposing teleportation schemes with excessively high quantum resources has been observed and the essence of this comment is applicable to all such proposals.Comment: It is shown that teleportation of multi qubit-states can be done using Bell state

Controlled cyclic remote state preparation of arbitrary qubit states

Quantum secure communications could securely transmit quantum information by using quantum resource. Recently, novel applications such as bidirectional and asymmetric quantum protocols have been developed. In this paper, we propose a new method for generating entanglement which is highly useful for multiparty quantum communications such as teleportation and Remote State Preparation (RSP). As one of its applications, we propose a new type of quantum secure communications, i.e. cyclic RSP protocols. Starting from a four-party controlled cyclic RSP protocol of one-qubit states, we show that this cyclic protocol can be generalized to a multiparty controlled cyclic RSP protocol for preparation of arbitrary qubit states. We point out that previous bidirectional and asymmetric protocols can be regarded as a simpler form of our cyclic RSP protocols