Scientific Publications

Title

An InP-based integrated modulated coherent state source for differential phase shift quantum key distribution

Authors

Abstract

A low-cost integrated differential phase shift QKD transmitter, which consist of a distributed Bragg reflector laser, a phase modulator, and Mach-Zehnder modulator sections for pulse carving and optical attenuation is presented. Initial characterization results of the laser, and the modulator sections are demonstrated.

Venue

24th annual IEEE Photonics Benelux Symposium 2019

Place and Date

Netherlands, Amsterdam, 21 – 22 November 2019

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Title

Differential Phase-Shift QKD in a 2:16-Split Lit PON with 19 Carrier-Grade Channels

Authors

N. Vokić, D. Milovančev, B. Schrenk, M. Hentschel, and H. Hübel

Abstract

We investigate the practical network integration of differential phase shift quantum key distribution following a cost-optimized deployment scheme where complexity is off-loaded to a centralized location. User terminal equipment for quantum state preparation at 1 GHz symbol rate is kept technologically lean through use of a directly-modulated laser as optical encoder. Integration in a passive optical network infrastructure is experimentally studied for legacy and modern optical access standards. We analyze the implications that result from Raman scattering arising from different spectral allocations of the classical channels in the O-, S-, C- and L-band, and prove that the quantum channel can co-exist with up to 19 classical channels of a fully-loaded modern access standard. Secure-key generation at a rate of 5.1×10 ⁻⁷ bits/pulse at a quantum bit error ratio of 3.28% is obtained over a 13.5 km reach, 2:16 split passive network configuration. The high power difference of 93.8 dB between launched classical and quantum signals in the lit access network leads to a low penalty of 0.52% in terms of error ratio.

Venue

IEEE Journal Selected Topics in Quantum Electronics

Title 

11.2 Tb/s Classical Channel Coexistence with DV-QKD over a 7-Core Multicore Fiber

Author

E. Hugues-Salas, O. Alia, R. Wang, K. Rajkumar, G. T. Kanellos, R. Nejabati and D. Simeonidou

Abstract

The feasibility of transmitting discrete-variable quantum key distribution channels with carrier-grade classical optical channels over multicore fibers is experimentally explored in terms of achievable quantum bit error rates, secret key rates as well as classical signal bit error rates. A coexistence transmission record of 11.2Tb/s is achieved for the classical channels simultaneously with a DV-QKD channel over a 1km-long 7-core multicore fiber. Coexistence over the same multicore fiber core is identified as a dominant factor for the performance of the quantum channel requiring optical bandpass filtering of 17nm for the quantum channel to avoid the effect of Raman noise. Also, counter-propagation of classical channels and quantum channels probe more tolerance to noise proliferation than co-propagation. In addition, the performance of the quantum channel is maintained when more than three cores are used for the classical channels. Furthermore, by adding a second DV-QKD channel in the multicore fiber, the simultaneous transmission of classical channels as well as the generation of quantum-secured keys of two QKD channels is achieved with an operational range of 10dBs of launched power into the MCF.

Venue

IEEE Journal of Lightwave Technology

Title

Compact, low-threshold squeezed light source

Authors

J. Arnbark, C. S. Jacobsen, R. B. Andrade, X. Guo, J. S. Neergaard-Nielsen, U. L. Andersen, T. Gehring

Abstract

Strongly squeezed light finds many important applications within the fields of
quantum metrology, quantum communication and quantum computation. However, due to the
bulkiness and complexity of most squeezed light sources of today, they are still not a standard tool
in quantum optics labs. We have taken the first steps in realizing a compact, high-performance
1550 nm squeezing source based on commercially available fiber components combined with
a free-space double-resonant parametric down-conversion source. The whole setup, including
single-pass second-harmonic generation in a waveguide, fits on a 30 cm×45 cm breadboard and
produces 9.3 dB of squeezing at a 5 MHz sideband-frequency. The setup is currently limited
by phase noise, but further optimization and development should allow for a 19″ sized turn-key
squeezing source capable of delivering more than 10 dB of squeezing.

Venue

Optics Express, vol 27

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Title

End-to-End Quantum Secured Inter-Domain 5G Service Orchestration Over Dynamically Switched Flex-Grid Optical Networks Enabled by a q-ROADM

Authors

Rui Wang, Rodrigo Stange Tessinari, Emilio Hugues Salas, Anderson Bravalheri, Navdeep Uniyal, Abubakar Muqaddas, Rafael Silva Guimaraes, Thierno Diallo, Shadi Moazzeni, Qibing Wang, George Kanellos, Reza Nejabati, Dimitra Simeonidou

Abstract

Dynamic and flexible optical networking enabled by NFV and SDN are the key technology enablers for supporting the dynamicity and bandwidth requirements of emerging 5G network services. To achieve the objective of 5G, Network Services (NSes) must be often deployed transparently over multiple administrative and technological domains. Such case often presents security risks since a typical NS may comprise a chain of network functions, each executed in different remote locations, and tampering within the network infrastructure may compromise their communication. To avoid such threats, QKD has been identified and proposed as a future-proof method immune to any algorithmic cryptanalysis based on quantum-physics mechanisms. The maturity of QKD has enabled the R&D of quantum networks coexisting with optical networks using telecom equipment. This makes the QKD a suitable candidate for the security of distributed and virtualised network services.
In this paper, for the first time, we propose a dynamic quantum-secured optical network for supporting network services that are dynamically created by chaining VNF over multiple network domains. This work includes a new quantum-ROADM, extensions to SDN-enabled optical control plane, and extensions to NFV orchestration to achieve quantum-aware, on-demand chaining of VNFs. The experimental results verify the capability of routing quantum and classical data channels both individually and dynamically over shared fibre links. Moreover, quantum secured chaining of VNFs in 5G networks is experimentally demonstrated via interconnecting four autonomous 5G islands simultaneously through the q-ROADM with eight optical channels using the 5GUK Exchange orchestration platform. The experimental scenarios and results confirm the benefit of the proposed data plane architecture and control/management plane framework.

Venue

Journal of Lightwave Technology (Invited), vol. 38, no. 1, pp. 139-149, 1 Jan.1, 2020

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Title

Coexistence of 11.2Tb/s Carrier-Grade Classical Channels and a DV-QKD Channel over a 7-Core Multicore Fibre

Authors

Emilio Hugues-Salas, Qibing Wang, Rui Wang, Kalyani Rajkumar, George T. Kanellos, Reza Nejabati, Dimitra Simeonidou

Abstract

We successfully demonstrate coexistence of record-high 11.2 Tb/s (56x200Gb/s) classical channels with a discrete-variable-QKD channel over a multicore fibre. Continuous secret key generation is confirmed together with classical channel performance below the SDFEC limit and a minimum quantum channel spacing of 17nm in the C-band.

Venue

European Conference on Optical Communication (ECOC),

Place and Date

Dublin, Ireland, 22 – 26 September 2019, Dublin

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Title

Field Trial of Dynamic DV-QKD Networking in the SDNControlled Fully-Meshed Optical Metro Network of the Bristol City 5GUK Test Network

Authors

R. S. Tessinari, A. Bravalheri, E. Hugues-Salas, R. Collins, D. Aktas, R.S. Guimaraes, O. Alia, J. Rarity, G. T. Kanellos, R. Nejabati, and D. Simeonidou

Abstract

We demonstrate for the first time a field trial of a fully meshed metro network with dynamic QKD networking capabilities across four optical network nodes in the 5GUK Test Network, where the DV-QKD quantum channels co-exist with classical channels and are dynamically switched and rerouted utilising QKD-aware SDN control.

Venue

European Conference on Optical Communications (ECOC’19). Post-deadline Paper PD3.6

Place and Date

Dublin, Ireland. September, 2019. 

Title

A platform approach towards hybrid photonic integration and assembly for communications, sensing, and quantum technologies based on a polymer waveguide technology

Authors

Moritz Kleinert, Madeleine Nuck, Hauke Conradi, David de Felipe, Martin Kresse, Walter Brinker, Crispin Zawadzki, Norbert Keil, Martin Schell

Abstract

We present functionalities of photonic integrated circuits and a generic assembly approach for their hybrid integration with other components in the polymer waveguide platform PolyBoard. In addition to standard integrated optics capabilities, the PolyBoard approach allows for the realization of flexible interconnects, the fabrication of multilayer waveguide structures with low intra-layer coupling losses, and the integration of bulk optical crystals in on-chip free-space sections. These functionalities enable PICs with applications ranging from communications, via sensing, to quantum technology. The semiautomated assembly process presented in the second part of this paper ensures the compatibility of all individual functionalities and the scalability of the developed approaches towards production.

Venue

2019 IEEE CPMT Symposium Japan (ICSJ)

Place and Date

Kyoto, Japan, 18-20 November 2019

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Title

General framework for the analysis of imperfections in nonlinear systems

Authors

Matteo Santandrea, Michael Stefszky, and Christine Silberhorn

Abstract

In this Letter, we derive a framework to understand the effect of imperfections on the phase-matching spectrum of a wide class of nonlinear systems. We show that this framework is applicable to many physical systems, such as waveguides or fibers. Furthermore, this treatment reveals that the product of the system length and magnitude of the imperfections completely determines the phase-matching properties of these systems, thus offering a general rule for system design. Additionally, our framework provides a simple method to compare the performance of a wide range of nonlinear systems.

Venue 

Optics Letters, 15 November 2019, Volume 44, Issue 22, pp. 5394-5649

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Title

Characterisation of fabrication inhomogeneities in Ti:LiNbO3 waveguides

Authors

Matteo Santandrea, Michael Stefszky, Ganaël Roeland and Christine Silberhorn

Abstract

Nonlinear processes in integrated, guiding systems are fundamental for both classical and quantum experiments. Integrated components allow for compact, modular and stable light-processing systems and as such their use in real-world systems continues to expand. In order to use these devices in the most demanding applications, where efficiency and/or spectral performance are critical, it is important that the devices are fully optimised. In order to achieve these optimisations, it is first necessary to gain a thorough understanding of current fabrication limits and their impact on the devices’ final performance. In this paper we investigate the current fabrication limits of titanium indiffused lithium niobate waveguides produced using a masked photolithographic method. By dicing a long (~8 cm) sample into smaller pieces and recording the resulting phase matching spectra, the fabrication error present in the UV photolithographic process is characterised. The retrieved imperfections fit well with theoretical expectations and from the measured imperfection profile it is shown that one can directly reconstruct the original distorted phase matching spectrum. Therefore, our measurements directly quantify the intrinsic limitations of the current standard UV photolitographically produced titanium-indiffused lithium niobate waveguides.

Venue

New Journal of Physics, Volume 21, December 2019

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