Abstract Quantum network scales the advantages of quantum communication protocols to more than two detached users, which offers great potential to realize the quantum internet. Here, a fully connected continuous‐variable (CV) quantum teleportation network architecture is presented, in which a squeezed state of light distributes each pair of entangled sideband modes to each communication link that bridges any pair of users. The quantum teleportation scheme is similar to standard two‐party ones for each communication link, without sacrificing communication capability and reliability. The demonstration based on CV‐entangled sideband modes opens an innovative possibility to implement many tasks of deterministic quantum information processing.
Abstract Quantum network scales the advantages of quantum communication protocols to more than two detached users, which offers great potential to realize the quantum internet. Here, a fully connected continuous‐variable (CV) quantum teleportation network architecture is presented, in which a squeezed state of light distributes each pair of entangled sideband modes to each communication link that bridges any pair of users. The quantum teleportation scheme is similar to standard two‐party ones for each communication link, without sacrificing communication capability and reliability. The demonstration based on CV‐entangled sideband modes opens an innovative possibility to implement many tasks of deterministic quantum information processing.
Quantum network allows communication among more than two users with quantum teleportation and high quantum fidelity enabled by non-classical resources. As one of the most versatile architectures, all users are connected mediated by the central station in the star topology network, leading to the realization of the information interconnection and interoperability. In this work, we experimentally demonstrate a 4-branch continuous variable (CV) quantum teleportation network with star topology by employing entangled sideband modes from one squeezed state of light. Here, multiple pairs of entangled sideband modes are distributed on demand to central station and four nodes, respectively. Each node linked to the network has its own communication channel with the central station, where the deterministic CV quantum teleportation protocol is implemented with the fidelities above 0.830.
Introduction: Continuous-variable quantum teleportation and entanglement distribution are fundamental building blocks for future quantum internet infrastructures. Quantum passive optical networks (QPONs) provide a promising architecture for scalable multi-user quantum communication by exploiting the mature passive optical network infrastructure. Materials and methods: We develop a theoretical framework for continuous-variable entanglement distribution and quantum teleportation in QPONs using two-mode squeezed vacuum states propagating through splitter–combiner–loss channels. Both downlink and uplink architectures are investigated under assisted and non-assisted protocols. The performance is analyzed using covariance matrix formalism, logarithmic negativity, and teleportation fidelity, and closed-form analytical expressions are derived together with numerical evaluations. Results: The analysis demonstrates that downlink entanglement distribution consistently outperforms the uplink architecture in terms of both logarithmic negativity and teleportation fidelity except in noise-less channels. Assisted protocols further enhance the achievable performance compared with non-assisted schemes. We derive the optimum squeezing parameter for non-assisted teleportation, showing that excessive squeezing may become detrimental because of network loss and splitting. Numerical results quantify the effects of network size, transmission distance, channel excess noise, detector imperfections, and measurement-added noise on entanglement distribution and teleportation performance. Also, we have showed that the time-division multiple-access is the preferred scheduling scheme between the users. Conclusions: The proposed framework establishes fundamental performance limits for continuous-variable QPONs and identifies practical design guidelines for scalable quantum access networks. The results demonstrate the advantages of downlink entanglement distribution and assisted teleportation, providing theoretical support for the development of future multi-user quantum communication and quantum internet infrastructures.
Very recently, we took part in a new development of quantum information, the so-called continuous variable (CV) quantum information theory. Such a further development is mainly due to the experimental and theoretical advantages offered by CV systems, i.e., quantum systems described by a set of observables, like position and momentum, which have a continuous spectrum of eigenvalues. According to this novel trend, quantum information protocols like quantum teleportation have been suitably extended to the CV framework. Here, we briefly review some mathematical tools relative to CV systems, and we consequently develop the concepts of quantum entanglement and teleportation in the CV framework by analogy with the qubit-based approach. Some connections between teleportation fidelity and entanglement properties of the underlying quantum channel are inspected. Next, we address the study of CV quantum teleportation networks where more users share a multipartite state and an arbitrary pair of them performs quantum teleportation. In this context, we show alternative protocols, and we investigate the optimal strategy that maximizes the performance of the network.
Quantum teleportation is a building block in quantum computation and quantum communication. The continuous-variable polarization squeezed state is a key resource in quantum networks, offering advantages for long-distance distribution and direct interfacing of quantum nodes. Although polarization squeezed state has been generated and distributed between remote users, it is a long-standing goal to implement controlled quantum teleportation of the polarization squeezed state with multiple remote users. Here, we propose a feasible scheme to teleport a polarization squeezed state among multiple remote users under control. The polarization state is transferred between different remote quantum networks, and the controlled quantum teleportation of the polarization state can be implemented in one quantum network involving multiple remote users. The results show that such a controlled quantum teleportation can be realized with 36 users through about 6-km free-space or fiber quantum channels, where the fidelity of 0.352 is achieved beyond the classical limit of 0.349 with an input squeezing variance of 0.25. This scheme provides a direct reference for the experimental implementation of remote and controlled quantum teleportation of polarization states, thus enabling more teleportation-based quantum network protocols.
Quantum teleportation is one of the most fundamental subjects in quantum information technology. This is because quantum teleportation can be used as not only a communication network but also a building block for universal quantum information processing. It is well known that there are two approaches (i. e. discrete and continuous variable approaches) in quantum information processing. In particular, continuous variable one has some advantages, that is, capability for deterministic and efficient quantum operations. In the case of continuous variable quantum teleportation, however, we cannot teleport quantum states perfectly due to finite level of quadrature squeezed states. Hence it is important to improve the fidelity of teleportation to realize more advanced quantum network and circuits. Thanks to the recent improvement of squeezing level, fidelity up to F=0.83 has been achieved. In this article, we review the experiment of high fidelity quantum teleportation for continuous variables, and its applications.
The wave-particle duality of light has led to two different encodings of optical quantum information. One approach, referred to as the discrete-variable (DV) one, relies on finite dimensional quantum systems, while the other one, referred to as the continuous-variable (CV) one, is based on wave-like states belonging to an infinite dimensional Hilbert space. These two encodings have historically been separated, but recently, new hybrid protocols which aim at combining the advantages of the two encodings have emerged [1] . In that prospect our recent demonstration of the measurement-induced generation of hybrid entanglement between discrete- and continuous-variable quantum states [2] , [3] , located at distant places and connected by a lossy channel, has opened the way to the implementation of hybrid protocols and heterogeneous quantum networks. Following the first protocols based on this resource, such as the remote preparation of continuous-variable qubits [4] , or a violation of an Einstein-Podolsky-Rosen steering inequality [5] , we will here report our latest experimental results on entanglement swapping and quantum teleportation protocols using hybrid entangled states based on different encodings [6] .