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Applied Sciences

Multipartite Continuous Variable Quantum Conferencing Network with Entanglement in the Middle

Zhaoyuan Zhang, Ronghua Shi, Ying Guo

Published Aug 7, 2018• 14 citations
Publisher

Abstract

We suggest a continuous variable quantum conferencing network scheme with an entangled source in the middle. Here, the source generates a multipartite entangled state and distributes the modes of the state to an arbitrary number of legitimate network users. The entangled modes that were received and measured by the users share mutual information, which is utilized to generate secure conferencing key between users. The scheme is proven secure against collective attacks on both the untrusted source in the middle and all the quantum links. Simulation results show that the presented scheme can achieve high rate secure conferencing for 100 users within a 400 m-radius community or factory area.

DOI
10.3390/app8081312

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We suggest a continuous variable quantum conferencing network scheme with an entangled source in the middle. Here, the source generates a multipartite entangled state and distributes the modes of the state to an arbitrary number of legitimate network users. The entangled modes that were received and measured by the users share mutual information, which is utilized to generate secure conferencing key between users. The scheme is proven secure against collective attacks on both the untrusted source in the middle and all the quantum links. Simulation results show that the presented scheme can achieve high rate secure conferencing for 100 users within a 400 m-radius community or factory area.
Abstract Multipartite quantum key distribution (QKD) is crucial for quantum communicating and may link massive private information to the complex quantum network protocols. In this paper, we tackle one of the difficulties in multipartite quantum communications by designing a quantum key distribution scheme with improved secret key rates. We suggest an entanglement-based tripartite continuous variable quantum key distribution (CVQKD) scheme for quantum network, where the source in the middle generates tripartite state and distributes the modes of the state to legitimate parties, respectively. We analyze the mutual information among the distributed modes of the tripartite state of protocols involving different attack strategies of the eavesdropper in varied circumstances. Numeric simulation results show that the CVQKD system enables the generations of secret keys against optimal coherent attacks.
Establishing a high-rate, cost-effective, and secure quantum communication network is critical for developing the quantum internet. A promising approach is to place a complex and expensive entangled source at a shared central node, which allows for efficient utilization of quantum resources in constructing a star-shaped downstream quantum access network. In this study, we propose a continuous-variable quantum passive optical network (CV-QPON) that employs a shared entangled source. We evaluate the network's security under two scenarios: one with a fully characterized entangled source and the other with a partially characterized entangled source. Both scenarios involve practical mixed entangled states. By combining the biased basis scheme, the renovated protocol outperforms the previous coherent state protocols in the secret key rate, transmission distance, the number of supported users, and tolerable excess noise. The results indicate that for a fully characterized entangled source, even at a transmission distance of 50 km, a moderate entangled source with 7 dB squeezing can still support up to 256 users accessing the network. Our scheme for a partially characterized entangled source relaxes the security assumptions regarding the central node, which is crucial for the downstream CV-QPON system. In this case, a 7 dB squeezing entangled source achieves a positive key rate for 64 users over a 30 km transmission distance, and it can even support up to 128 users at a 10 km transmission distance. With a 10 dB squeezing entangled source, 256 users can still be supported at a 30 km transmission distance. Furthermore, we analyze the protocol's security in the finite-size scenario and identify an optimal biased basis ratio that maximizes the key rate of the protocol. Given the rapid advancements in integrated entangled sources, our scheme offers a promising pathway for developing low-cost, high-rate, high-security, and large-scale quantum communication networks.
We introduce a measurement-device independent star network which is conveniently based on continuous variable systems and standard linear optics. Here an arbitrary number of users send modulated coherent states to an untrusted relay where a generalized Bell detection creates multi-partite secret correlations. These correlations are then distilled into a shared secret key to implement a completely-secure quantum conference or, alternatively, a protocol of quantum secret-sharing. Our scheme is composably secure and able to achieve high rates with cheap optical implementation.
Quantum conference (QC) is a cryptographic task in secure communications that involves more than two users wishing to establish identical secret keys among N users. The Greenberger–Horne–Zeilinger (GHZ) entangled state is the basic resource for quantum cryptographic communication due to the existence of multipartite quantum correlations. An unconditional and efficient quantum network can be established with a continuous variable (CV) GHZ entangled state because of its deterministic entanglement. Here, we report an implementation of QC scheme using a CV multipartite GHZ entangled state. The submodes of a quadripartite GHZ entangled state are distributed to four spatially separated users. The proposed QC scheme is proved to be secure even when the entanglement is distributed through lossy quantum channels and the collective Gaussian attacks are in the all lossy channels. The presented QC scheme has the capability to be directly extended to a larger scale quantum network by using entangled states with more submodes.
Abstract One of the main open problems in quantum communication is the design of efficient quantum-secured networks. This is a challenging goal, because it requires protocols that guarantee both unconditional security and high communication rates, while increasing the number of users. In this scenario, continuous-variable systems provide an ideal platform where high rates can be achieved by using off-the-shelf optical components. At the same time, the measurement-device independent architecture is also appealing for its feature of removing a substantial portion of practical weaknesses. Driven by these ideas, here we introduce a modular design of continuous-variable network where each individual module is a measurement-device-independent star network. In each module, the users send modulated coherent states to an untrusted relay, creating multipartite secret correlations via a generalized Bell detection. Using one-time pad between different modules, the network users may share a quantum-secure conference key over arbitrary distances at constant rate.
We analyze the performance of continuous-variable quantum key distribution protocols where the entangled source originates not from one of the trusted parties, Alice or Bob, but from the malicious eavesdropper in the middle. This is in contrast to the typical simulations where Alice creates the entangled source and sends it over an insecure quantum channel to Bob. By using previous techniques and identifying certain error-correction-protocol equivalences, we show that Alice and Bob do not need to trust their source and can still generate a positive key rate. Such a situation can occur in a quantum network where the untrusted source originated in between the two users.