40-user fully connected entanglement-based quantum key distribution network without trusted node

Abstract

Quantum key distribution (QKD) would play an important role in future information technologies due to its theoretically proven security based on the laws of quantum mechanics. How to realize QKDs among multiple users in an effective and simple way is crucial for its real applications in communication networks. In this work, we propose and demonstrate a fully connected QKD network without trusted node for a large number of users. Using flexible wavelength division multiplexing/demultiplexing and space division multiplexing, entanglement resources generated by a broadband energy-time entangled quantum light source are distributed to 40 users. Any two users share a part of entanglement resources, by which QKD is established between them. As a result, it realizes a fully connected network with 40 users and 780 QKD links. The performance of this network architecture is also discussed theoretically, showing its potential on developing quantum communication networks with large user numbers owing to its simplicity, scalability, and high efficiency.

Realizing an entanglement-based multi-user quantum network with integrated photonics

“…However, the photons generated by our MRR source inherently have narrow linewidths (∼ 650MHz), so the wavelength dependence of the beam splitter's splitting ratio within this range can be ignored. Recently, there are several platforms that use wavelength division multiplexing schemes to realize multi-user quantum networks [16][17][18][19][20]. And some of these platforms have already been implemented in real-world scenarios.…”

“…Particularly, the frequency DOF of a single photon is attractive due to its compatibility with standard optical fiber infrastructure, and ability to perform routing based on optical frequencies [14]. Multiplexing the frequency DOF of photons is not only an efficient approach towards high data rates in classical communications [15] but also a promising way to provide connectivity for quantum networks (QNs) [16][17][18][19][20].…”

“…To date, QNs based on trusted relays or active/passive routing have been widely deployed [22][23][24][25][26] and entanglement-swapping-based quantum direct communication network have also been demonstrated [27,28]. Fully and simultaneously connected QN schemes have been proposed and realized based on entanglement distribution without relying on trusted nodes [16][17][18][19]. In these pioneering studies, each pair of users share a bipartite entanglement through carving the broadband signal/idler spectrum into a series of slices and multiplexing them.…”

First Request First Service Entanglement Routing Scheme for Quantum Networks

“…Establishing the entanglement connections has been a key challenge for large-scale and long-distance quantum networks. To address this, a fully connected entanglement network [ 31 ] was first implemented with the dense wavelength division multiplexing (DWDM) strategy, but wavelength channels are required for n users, which limits the network scale to a few users [ 32 , 33 , 34 ]. Afterward, a fully connected quantum network on a city-wide scale with passive beam splitters and DWDMs was demonstrated in 2020, which decreased the requirement of the wavelength channels to [ 32 ].…”

Gain-gain and gain-lossless PT-symmetry broken from PT-phase diagram

“…Depending on the nature of the input and output light, beam splitting can be used in quantum and classical optics [28]. Among them, classical beam splitting can be used to design optical routers [29], logic gates [30,31] and other devices [32,33], while quantum beam splitting is valuable in studying anti-bunching [34], squeezed states [35] and quantum entanglement [36,37]. However, most of previous studies on beam splitting have focused on the Hermitian system [38].…”