scientific publications
Results from the QT Flagship project UNIQORN
Advances in quantum cryptography
Title
Advances in quantum cryptography
Authors
S. Pirandola, U. L. Andersen, L. Banchi, M. Berta, D. Bunandar, R. Colbeck, D. Englund, T. Gehring, C. Lupo, C. Ottaviani, J. L. Pereira, M. Razavi, J. Shamsul Shaari, M. Tomamichel, V. C. Usenko, G. Vallone, P. Villoresi, and P. Wallden
Abstract
Quantum cryptography is arguably the fastest growing area in quantum information science. Novel theoretical protocols are designed on a regular basis, security proofs are constantly improving, and experiments are gradually moving from proof-of-principle lab demonstrations to in-field implementations and technological prototypes. In this paper, we provide both a general introduction and a state-of-the-art description of the recent advances in the field, both theoretical and experimental. We start by reviewing protocols of quantum key distribution based on discrete variable systems. Next we consider aspects of device independence, satellite challenges, and protocols based on continuous-variable systems. We will then discuss the ultimate limits of point-to-point private communications and how quantum repeaters and networks may overcome these restrictions. Finally, we will discuss some aspects of quantum cryptography beyond standard quantum key distribution, including quantum random number generators and quantum digital signatures.
Venue
OSA Publishing, Advances in Optics and Photonics, Vol. 12, Issue 4, pp. 1012-1236 (2020)
Hybrid Polymer Integration for Communications, Sensing and Quantum Technologies from the Visible to the Infrared
Title
Hybrid Polymer Integration for Communications, Sensing and Quantum Technologies from the Visible to the Infrared
Authors
Moritz Kleinert, David de Felipe, Hauke Conradi, Martin Kesse, Lennart Jehle, Madleine Weigel, Tianwen Qian, Klara Mihov, Jakob Reck, Crispin Yawadyki, Norbert Keil, Martin Schell
Abstract
We present concepts for transferring PIC building blocks from classical implementations in the C band towards shorter wavelengths. Exemplary functionalities include hybrid tunable lasers for 785 nm and 1064 nm, on-chip free-space sections for non-linear optics, and dielectric thin-film filters with 68 dB suppression
Venue
ECOC 2021 (https://www.ecoc2021.org/)
Place and Date
Bordeaux – France, 13-16 September 2021
Integrated balanced homodyne photonic–electronic detector for beyond 20 GHz shot-noise-limited measurements
Title
Integrated balanced homodyne photonic–electronic detector for beyond 20 GHz shot-noise-limited measurements
Authors
Cédric Bruynsteen, Michael Vanhoecke, Johan Bauwelinck, and Xin Yin
Abstract
Optical homodyne detection is used in numerous quantum and classical applications that demand high levels of sensitivity. However, performance is typically limited due to the use of bulk optics and discrete receiver electronics. To address these performance issues, in this work we present a co-integrated balanced homodyne detector consisting of a silicon photonics optical front end and a custom integrated transimpedance amplifier designed in a 100 nm GaAs pHEMT technology. The high level of co-design and integration provides enhanced levels of stability, bandwidth, and noise performance. The presented detector shows a linear operation up to 28 dB quantum shot noise clearance and a high degree of common-mode rejection, at the same time achieving a shot-noise-limited bandwidth of more than 20 GHz. The high performance of the developed devices provide enhanced operation to many sensitive quantum applications such as continuous variable quantum key distribution, quantum random number generation, or high-speed quantum tomography.
Venue
Optica 8, 1146-1152 (2021), OSA Publishing
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A Quantum Key Distribution simulator for BB84-type protocols with decoy states
Title
A Quantum Key Distribution simulator for BB84-type protocols with decoy states
Authors
Florian Prawits, Christoph Pacher and Hannes Hübel
Abstract
BB84-type DV-QKD protocols that implement weak coherent laser pulses as the carrier for the encoded information are severely limited in their maximally achievable transmission distance due to the inherent threat of photon number splitting (PNS) attacks. This potential weakness can be elegantly eliminated by the adaption of the protocol to include so-called decoy states (DS) in the transmission. These decoy states allow Alice and Bob to probe their transmission channel and statistically infer whether a PNS type attack is occurring, thus precluding Eve from successfully using this strategy. The added degrees of freedom of deciding how often to send decoy states and which intensities to use for them however further complicates the already complex task of predicting the impact on protocol performance and finding a set of suitable parameters to achieve optimal secret key rates (skr). In order to predict optimal performance, as a function of characteristics of the QKD setup like channel losses and device imperfections, state preparation fidelity, decoy state parameters and finite size effects, the software simulator pyDSsim has been developed. The tool is written in Python and implements the recent security proof framework introduced in [1,2]. The software can be scripted from the command line or used via a graphical user interface (GUI: QT5 framework) for easy exploration via parametrized x-y plots of over 40 different variables, allowing a comprehensive evaluation of their interdependencies. The main feature however is the option to numerically compute the set of protocol variables for a given QKD-setup which maximizes the secret key rate under constraints typical for practical implementations: fixed block sizes or fixed acquisition times for the raw key. To this end two different algorithms (differential-evolution [3] and L-BFGS-B [4]) are utilized, allowing for a cross-check of the acquired results and choice between speed and accuracy of the approach.
References [1] Rusca, D., Boaron, A., Grünenfelder, F., Martin, A. & Zbinden, H. Finite-key analysis on the 1-decoy state QKD protocol. Appl. Phys. Lett. 112, 171104 (2018) [2] Lim, C. C. W., Curty, M., Walenta, N., Xu, F. & Zbinden, H. Concise security bounds for practical decoy-state quantum key distribution. Phys. Rev. A 89, 022307 (2014) [3] R. H. Byrd, P. Lu and J. Nocedal. A Limited Memory Algorithm for Bound Constrained Optimization, (1995), SIAM Journal on Scientific and Statistical Computing, 16, 5, pp. 1190-1208. [4] Storn, R and Price, K, Differential Evolution – a Simple and Efficient Heuristic for Global Optimization over Continuous Spaces, Journal of Global Optimization, 1997, 11, 341 – 359.
Venue
QCrypt 2021 (https://2021.qcrypt.net/)
Place and Date
Online, 23 – 27 August 2021
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1.6 Tbps Classical Channel Coexistence With DV-QKD Over Hollow Core Nested Antiresonant Nodeless Fibre (HC-NANF)
Title
1.6 Tbps Classical Channel Coexistence With DV-QKD Over Hollow Core Nested Antiresonant Nodeless Fibre (HC-NANF)
Authors
O. Alia(1)*, R. S. Tessinari(1), T. D. Bradley(2), H. Sakr(2), K. Harrington(2), J. Hayes(2), Y. Chen(2),
P. Petropoulos(2), D. Richardson(2), F. Poletti(2) G. T. Kanellos(1), R. Nejabati(1), D. Simeonidou(1)
(1) High Performance Networks Group, University of Bristol, Woodland Road, Bristol, UK
(2) Optoelectronics Research Centre, University of Southampton, Southampton, SO17 1BJ, UK
*Corresponding author: obada.alia@bristol.ac.uk
Abstract
We demonstrate for the first time the coexistence of a quantum-channel and 8200 Gpbs 16-QAM
optical channels with launching powers as high as -9dBm/channel in a 2 km HC-NANF. Comparative
analysis with single-mode fibre reveals that the quantum-channel could not be sustained at such powerlevels.
Venue
ECOC 2021 (https://www.ecoc2021.org/)
Place and Date
Bordeaux – France, 13-16 September 2021
Coexistence of a Quantum QKD Channel and 4×100 Gbps Classical Channels in Nested Antiresonant Nodeless Hollow Core Fibre
Title
Coexistence of a Quantum QKD Channel and 4×100 Gbps Classical Channels in Nested Antiresonant Nodeless Hollow Core Fibre
Authors
O. Alia*, R. S. Tessinari, T. D. Bradley, H. Sakr, K. Harrington, J. Hayes, Y. Chen, P. Petropoulos, D. Richardson, F. Poletti, G. T. Kanellos, R. Nejabati, D. Simeonidou
Abstract
We demonstrated for the first time a coexistence between a quantum QKD channel and 4×100 Gbps pm-qpsk carrier-grade classical optical channels in a 2 km Nested Antiresonant Nodeless Hollow Core fibre. Our results show a drop of less than 10% in the Secret Key Rate (SKR) when using a HCF compared to a significant drop of 97% in the SKR when quantum and classical signals coexist on a single core of a Multicore fibre (MCF) with equal losses, indicating that NANF type HCF significantly outperforms single-mode fibres (SMF) performance for quantum/classical coexistence. This significant difference in the SKR drop is due to the ultra-low nonlinear effects in HCF comparing to glass core fibres such as SMF and MCF.
Venue
Qcrypt 2021 (https://2021.qcrypt.net/)
Place and Date
Online, 23 – 27 August 2021
Linear SPAD array for quantum communication
Title
Linear SPAD array for quantum communication
Authors
A. Incoronato, F. Severini, F. Madonini, F. Villa, F. Zappa
Abstract
Quantum communication is a fast-growing field that takes advantage of the quantum physics laws to protect and secure sensitive data. This work takes part of the European project UNIQORN (Affordable Quantum Communication for Everyone: Revolutionizing the Ecosystem from Fabrication to Application) whose aim is to develop a Quantum Systemon- Chip (QSoC) for telecom application. One components of the overall developed systems is an integrated circuit with photodetectors to enable the Quantum Random Number Generator (QRNG) block of the system, tailored to communicate with a non-linear optics circuit to be assembled onto it.
The integrated circuit, fabricated in a BCD 160 nm technology, consists of a 32×1 linear array based on Single-Photon Avalanche-Diode (SPAD) detectors for the generation of a raw random number, by revealing the position on the array of the single photon impinging on it. The linear array architecture consists of 32 pixels, with 125 μm pitch, each made by 4 SPADs with different diameter (5 μm, 10 μm, 20 μm, and 50 μm). Two operation modes are implemented: Single-Hit Mode (able to reveal the 5-bit position of the pixel triggered by a single photon, representing a pseudorandom number, in a time window synchronous with the laser emission) and Multi-Hit Mode (used to identify a coincidence of a given number of photons detected within a specified time window).
Venue
SPIE Optics + Optoelectronics, 2021
Place and date
Online, 19 – 23 April 2021
Demonstration of a Dynamic QKD NetworkControl Using a QKD-Aware SDN ApplicationOver a Programmable Hardware Encryptor
Title
Demonstration of a Dynamic QKD NetworkControl Using a QKD-Aware SDN ApplicationOver a Programmable Hardware Encryptor
Authors
E. Arabul, R. S. Tessinari, O. Alia, E. Hugues-Salas, G. T. Kanellos, R. Nejabati, D. Simeonidou.
Abstract
We successfully implemented a QKD-Aware SDN application capable of realtime monitoring and controlling a quantum secure network paired with a programmable FPGA encryption/decryption technology to provide on-demand encryption algorithms for network services between different sites.
Venue
OFC 2021 – The Optical Networking and Communication Conference
Place and date
Hosted in San Francisco, United States, but virtual on 06 – 11 June 2021