An interesting aspect of multipartite entanglement is that for perfect teleportation and superdense coding, not the maximally entangled W states but a special class of non-maximally entangled W-like states are required. Therefore, efficient preparation of such W-like states is of great importance in quantum communications, which has not been studied as much as the preparation of W states. In this letter, we propose a simple optical scheme for efficient preparation of large-scale polarization based entangled W-like states by fusing two W-like states or expanding a W-like state with an ancilla photon. Our scheme can also generate large-scale W states by fusing or expanding W or even W-like states. The cost analysis show that in generating large scale W states, the fusion mechanism achieves a higher efficiency with non-maximally entangled W-like states than maximally entangled W states. Our scheme can also start fusion or expansion with Bell states, and it is composed of a polarization dependent beam splitter, two polarizing beam splitters and photon detectors. Requiring no ancilla photons or controlled gates to operate, our scheme can be realized with the current photonics technology and we believe it enables advances in quantum teleportation and superdense coding in multipartite settings.
The states of W-class as shared resources for perfect teleportation and superdense coding
我们知道,三量子比特系统的态有两类:GHZ类和W类。本文考虑W类态的隐形传态和超密集编码,并将其推广到多粒子系统。首先,我们描述了两个转换的共享资源的隐形传态和超密集编码,这使得许多新的协议,从一些已知的。作为这些变换的应用,我们得到了W类态适合于理想隐形传态和超密编码的一个充要条件。作为另一个应用,我们发现状态$|W>_{123}={1/2}(|100>_{123}+|010>_{123}+\sqrt{2}|001>_{123})$可以通过发送两个量子比特来传输三个经典比特,这是P.Agrawal和A. Pati [Phys. Rev. A待出版]。我们将W类的态推广到高维的多量子比特系统和多粒子系统。我们提出了两个利用多量子比特系统的W态进行隐形传态和超密集编码的协议,推广了P.Agrawal和A.帕蒂我们得到了将多量子比特系统的W态分割成两个子系统的最优方法,使得它们之间的纠缠达到最大值。
The necessary and sufficient condition for perfect teleportation and superdense coding and all the suitable states for teleportation and superdense coding
Superdense coding is a paradigmatic protocol in quantum information science, employing a quantum communication channel to send classical information more efficiently. As we show here, it can be understood as a particular case of a prepare and measure experiment, a scenario that has attracted growing attention for its fundamental and practical applications. Formulating superdense coding as a prepare and measure scenario allows us to provide a semi-device-independent witness of entanglement that significantly improves over previous tests. Furthermore, we also show how to adapt our results into s…
We consider a task in which classical information is encoded into a quantum system by an operation restricted by symmetry. The maximum amount of classical information that can be encoded under this restriction, namely the symmetry-restricted classical information capacity, depends on the initial state of the system. Our focus is on whether the capacity of an asymmetric state can be strictly larger than that of any symmetric states, whereas the latter is a strictly positive constant. That is, we ask whether an analog of superdense coding is implementable in the resource theory of asymmetry. We …
Superdense coding uses entanglement as a resource to communicate classical information securely through quantum channels. A superdense coding method is optimal when its capacity reaches Holevo bound. We show that for optimality, maximal entanglement is a necessity across the bipartition of Alice and Bob, but neither absolute nor genuine multipartite entanglement is required. Unlike the previous schemes, which can transmit either even or odd bits of information, we have demonstrated a generalized dense coding protocol using the genuine multipartite entangled GHZ state to send arbitrary informat…
Construction of a fault-tolerant quantum computer remains a challenging problem due to unavoidable noise in quantum states and the fragility of quantum entanglement. However, most of the error-correcting codes increases the complexity of the algorithms, thereby decreasing any quantum advantage. Here we present a task-specific error-correction technique that provides a complete protection over a restricted set of quantum states. Specifically, we give an automated error correction in Superdense Coding algorithms utilizing n-qubit generalized Bell states. At its core, it is based on non-destructi…
Utility of noiseless linear amplification and attenuation in single-rail discrete-variable quantum communications
University of Queensland(昆士兰大学);The Australian National University(澳大利亚国立大学);A*STAR Quantum Innovation Centre (Q.InC), Agency for Science, Technology and Research (A*STAR)(新加坡科技研究局量子创新中心);Q-CTRL
Coherence Scaling in Quantum Communication Protocols
Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas (UNICAMP)(坎皮纳斯州立大学格莱布·瓦塔金物理研究所);Institut für Physik, Carl-von-Ossietzky Universität Oldenburg(奥尔登堡卡尔·冯·奥西茨基大学物理研究所)