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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Title

Deployment Opportunities for DPS-QKD in the Co-Existence Regime of Lit GPON / NG-PON2 Access Networks

Authors

N. Vokic, D. Milovancev, B. Schrenk, M. Hentschel, and H. Hübel

Abstract 

We demonstrate cost-effective QKD integration for GPON and NG-PON2. Operation at 5.1×10^-7 secure bits/pulse and a QBER of 3.28% is accomplished for a 13.5-km reach, 2:16-split PON, with 0.52% co-existence penalty for 19 classical channels.

Venue

The Optical Fiber Communication Conference & Exhibition (OFC 2020)

Place and Date

San Diego Convention Center, San Diego, California, USA, 8 – 12 March 2020

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Title

Flexible Entanglement Distribution Overlay for Cloud/Edge DC Interconnect as Seed for IT-Secure Primitives

Authors

F. Laudenbach, B. Schrenk, M. Achleitner, N. Vokic, D. Milovancev, and H. Hübel

Abstract 

We leverage spectral assets of entanglement and spatial switching to realize a flexible distribution map for cloud-to-edge and edge-to-edge quantum pipes that seed IT-secure primitives. Dynamic bandwidth allocation and co-existence with classical control are demonstrated.

Venue

The Optical Fiber Communication Conference & Exhibition (OFC 2020)

Place and Date

San Diego Convention Center, San Diego, California, USA, 8 – 12 March 2020

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Title

Compact Differential Phase-Shift Quantum Receiver Assisted by a SOI / BiCMOS Micro-Ring Resonator

Authors

N. Vokic, D. Milovancev, W. Boxleitner, H. Hübel, and B. Schrenk

Abstract 

We demonstrate a phase-selective and colorless quantum receiver assisted by a silicon-on-insulator microring, enabling a low 1.3% QBER at 5.3kb/s secure-key rate. No penalty incurs compared to a delay interferometer. BiCMOS 3D-integration is proven feasible.

Venue

The Optical Fiber Communication Conference & Exhibition (OFC 2020)

Place and Date

San Diego Convention Center, San Diego, California, USA, 8 – 12 March 2020

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Title

On the Filter Issues in Multiplexing Classical and QKD Links through WSS-based Nodes

Authors

D. Zavitsanos (NTUA), G. Giannoulis (NTUA), A. Raptakis (NTUA), Ch. Kouloumentas (NTUA), and H. Avramopoulos (NTUA)

Abstract

We present an extensive study on the quantum link multiplexed with intense classical signal in a WSS-based node. Theoretical results on QBER and SKR performance revealed the dependence of BB84-QKD link on passband spectral response.

Venue

Asia Communications and Photonics Conference (ACP) 2019

Place and date

Chengdu, China, Nov. 2-5, 2019

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Title

Photon-Pair Sources and Quantum Cryptography using Continuous Variables

Authors

Fabian Laudenbach (AIT Austrian Institute of Technology)

Abstract 

The counter-intuitive phenomena of quantum mechanics are currently leaping from their mere exploration to their deployment in real-life applications. Quantum superposition, the uncertainty principle, the no-cloning theorem and, most prominently, quantum entanglement are proven to allow for computing and cryptography algorithms, simulation of complex physical phenomena and sensing of physical quantities in new and beneficial ways which are unparalleled by classical devices. In particular, quantum technologies based on photons offer a straightforward way to protect quantum states from decoherence and, if necessary, transmit them from one place to another reliably. Most applications in the realm of optical quantum technology have successfully been demonstrated in proof-of-principle experiments. However, in order for quantum technologies to unleash their full potential and establish in the shape of wide-spread applications with a true advantage over their classical counterparts, they need to become scalable in size, quantity, performance and cost. This thesis is divided into two parts dealing with different aspects of quantum optics: The first part discusses ways to generate photon pairs with high brightness and, at the same time, high quality in terms of their performance in quantum experiments. The second part provides a theoretical discussion and experimental demonstration of quantum cryptography based on continuous variables — a promising concept to make the striking advantages of quantum communication compatible with off-the-shelf telecom hardware and fibre networks. As I hope, the research presented in both parts of this thesis will, in one way or another, make a contribution to the scalability of quantum technologies and thereby help to enforce the breakthrough of the so-called quantum revolution.