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arXiv:1607.01693 · Quantum Science and Technology

Multi-user quantum key distribution with entangled photons from an AlGaAs chip

Claire Autebert, J Trapateau, Adeline Orieux, Aristide Lemaître, C. Gómez, Eleni Diamanti, Isabelle Zaquine, S. Ducci

Published Dec 1, 2016• 46 citations
arXivHTMLPDF

Abstract

Abstract In view of real-world applications of quantum information technologies, the combination of miniature quantum resources with existing fibre networks is a crucial issue. Among such resources, on-chip entangled photon sources play a central role for applications spanning quantum communications, computing and metrology. Here, we use a semiconductor source of entangled photons operating at room temperature in conjunction with standard telecom components to demonstrate multi-user quantum key distribution, a core protocol for securing communications in quantum networks. The source consists of an AlGaAs chip-emitting polarisation entangled photon pairs over a large bandwidth in the main telecom band around 1550 nm without the use of any off-chip compensation or interferometric scheme; the photon pairs are directly launched into a dense wavelength division multiplexer (DWDM) and secret keys are distributed between several pairs of users communicating through different channels. We achieve a visibility measured after the DWDM of 87% and show long-distance key distribution using a 50-km standard telecom fibre link between two network users. These results illustrate a promising route to practical, resource-efficient implementations adapted to quantum network infrastructures.

DOI
10.1088/2058-9565/1/1/01lt02

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In view of real world applications of quantum information technologies, the combination of miniature quantum resources with existing fibre networks is a crucial issue. Among such resources, on-chip entangled photon sources play a central role for applications spanning quantum communications, computing and metrology. Here, we use a semiconductor source of entangled photons operating at room temperature in conjunction with standard telecom components to demonstrate multi-user quantum key distribution, a core protocol for securing communications in quantum networks. The source consists of an AlGaAs chip emitting polarization entangled photon pairs over a large bandwidth in the main telecom band around 1550 nm without the use of any off-chip compensation or interferometric scheme; the photon pairs are directly launched into a dense wavelength division multiplexer (DWDM) and secret keys are distributed between several pairs of users communicating through different channels. We achieve a visibility measured after the DWDM of 87% and show long-distance key distribution using a 50-km standard telecom fibre link between two network users. These results illustrate a promising route to practical, resource-efficient implementations adapted to quantum network infrastructures.
Abstract Quantum communication networks enable applications ranging from highly secure communication to clock synchronization and distributed quantum computing. Miniaturized, flexible, and cost-efficient resources will be key elements for ensuring the scalability of such networks as they progress towards large-scale deployed infrastructures. Here, we bring these elements together by combining an on-chip, telecom-wavelength, broadband entangled photon source with industry-grade flexible-grid wavelength division multiplexing techniques, to demonstrate reconfigurable entanglement distribution between up to 8 users in a resource-optimized quantum network topology. As a benchmark application we use quantum key distribution, and show low error and high secret key generation rates across several frequency channels, over both symmetric and asymmetric metropolitan-distance optical fibered links and including finite-size effects. By adapting the bandwidth allocation to specific network constraints, we also illustrate the flexible networking capability of our configuration. Together with the potential of our semiconductor source for distributing secret keys over a 60 nm bandwidth with commercial multiplexing technology, these results offer a promising route to the deployment of scalable quantum network architectures.
Quantum cryptography with entangled photon pairs can be more powerful than protocols based onsingle photons or weak coherent pulses: they can tolerate higher losses and thus allow thedistribution of quantum secret keys (QKD) over longer distances [1], they also provide a waytowards device-independent quantum cryptography [2]. However, in order to enable a wide use ofentangled photon pairs in future quantum telecommunication systems, further developments areneeded to demonstrate performant sources that can be easily fabricated and integrated into Telecomfiber networks.Here we present a source consisting of an aluminium gallium arsenide waveguide generatingphoton pairs in the Telecom band by type II spontaneous parametric down-conversion [3]. Such adevice has already been proven to work under electrical pumping [4]. Thanks to the very smallbirefringence of the guided modes, the pairs are directly generated in a polarization-entangled Bellstate, without the need for any post-compensation. Moreover, as the photons are emitted over alarge bandwidth (about 100 nm) with a joint spectrum that exhibits frequency anticorrelation, thesame source can be used to simultaneously distribute keys among multiple pairs of users by usingstandard Telecom wavelength demultiplexers [5]. Here, we experimentally show the distribution ofquantum secret keys with the BBM92 QKD protocol [6] between four different pairs of users with acommercial 100 GHz demultiplexer (0.8 nm channel width and spacing). Under CW pumpingconditions, using free-running InGaAs single-photon detectors, we achieve a secret key rate of 0.21bits/s and a qubit error rate (QBER) of 6.9% over 50 km of standard optical fiber.Our results, obtained with a robust and simple experimental set-up, open the way towards theimplementation of practical device-independent quantum communication protocols.
Abstract A fully connected quantum network with a wavelength division multiplexing architecture plays an increasingly pivotal role in quantum information technology. With such architecture, an entanglement-based network has been demonstrated in which an entangled photon-pair source distributes quantum entanglement resources to many users. Despite these remarkable advances, the scalability of the architecture could be constrained by the finite spectrum resource, where O(N2){\mathscr{O}}\left({N}^{2}\right)O(N2) O N 2 wavelength channels are needed to connect N users, thus impeding further progress in real-world scenarios. Here, we propose a scheme for the wavelength division multiplexing entanglement-based network using a state-multiplexing quantum light source. With a dual-pump configuration, the feasibility of our approach is demonstrated by generating state-multiplexing photon pairs at multiple wavelength channels with a silicon nitride microring resonator chip. In our demonstration, we establish a fully connected graph between four users with six wavelength channels—saving half of which without sacrificing functionality and performance of the secure communication. A total asymptotic secure key rate of 1946.9 bps is obtained by performing the BBM92 protocol with the distributed state. The network topology of our method has great potential for developing a scalable quantum network with significantly minimized infrastructure requirements.