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Journal of the Optical Society of America B

Realizing long-term quantum cryptography

Abdul Mirza, Francesco Petruccione

Published May 21, 2010• 52 citations
Publisher

Abstract

We present a set of long-term quantum key distribution (QKD) results from the QuantumCity initiative in Durban, South Africa. Many QKD experimental setups have failed to provide a long-term analysis of QKD systems in commercial environments. Long-term analysis of the stability and performance of these systems is an imperative step towards the market acceptance of QKD technology. The Durban–QuantumCity project intends to develop a multi-user quantum communication network that is currently overlaid on the fiber infrastructure of the eThekwini Municipality. The first phase of this project includes the deployment of a four-node star network. To date, two links have been deployed and one link has run continuously for a number of months. We provide a brief overview of practical implementations of quantum networks and the first set of results from the live data encryption of the QuantumCity project.

DOI
10.1364/josab.27.00a185

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We present a set of long-term quantum key distribution (QKD) results from the QuantumCity initiative in Durban, South Africa. Many QKD experimental setups have failed to provide a long-term analysis of QKD systems in commercial environments. Long-term analysis of the stability and performance of these systems is an imperative step towards the market acceptance of QKD technology. The Durban–QuantumCity project intends to develop a multi-user quantum communication network that is currently overlaid on the fiber infrastructure of the eThekwini Municipality. The first phase of this project includes the deployment of a four-node star network. To date, two links have been deployed and one link has run continuously for a number of months. We provide a brief overview of practical implementations of quantum networks and the first set of results from the live data encryption of the QuantumCity project.
The QuantumCity and QuantumStadium projects are aimed at developing and examining quantum‐secured communication networks in a long‐term, commercial environment. Many Quantum Key Distribution (QKD) experimental setups to date have failed to provide a long‐term analysis of the systems as well as report on the robustness of the devices within an industrial context. The aforementioned projects provide an insight into these characteristics respectively. The projects are hosted within the eThekwini Municipality’s fibre optic network. They securely connect relevant Municipal buildings, providing the client nodes with an option of quantumsecured communication. The QuantumCity initiative has deployed QKD solutions for almost 2 years while the QuantumStadium project ran for the duration of the 2010 FIFA World Cup.
The information society that presides today is dependent on the communication industry to facilitate unintelligible data transfers between authenticated parties. Such requirements have, to date, taken advantage of security based on the mathematical complexities of certain algorithms. However, the advancement of computing power and the advent of the quantum computer together with the vulnerability of this scheme to mathematical progress have prompted the introduction of quantum cryptography. This process, through the laws of quantum physics, ensures provably secure data communication. Quantum cryptography provides physical protection to individual bits of information thus providing a hardware implemented solution. The implementation of this theoretical concept requires much practical innovation for transparent deployment into current cryptographic solutions. This thesis introduces the concept of quantum cryptography in a practical perspective. It raises a few core concerns with the present quantum cryptographic technology and provides some solutions towards the practical deployment of commercially feasible quantum cryptographic systems. The thesis commences with an introduction to classical cryptography focussing on key management protocols. This is followed by the presentation of the basic concepts of Quantum Key Distribution (QKD) together with an explanation of some QKD protocols and parameter required to classify such protocols. Chapter 2 discusses the theoretical and practical aspects of quantum channels in particular optical fibre. The primary challenges of transferring classical and quantum data along these channels are mentioned together with some solutions. A description of experimental usage with present QKD solutions is presented in Chapter 3. An investigation into highly efficient QKD protocols follows illustrating effective post-distribution processing for increasing the efficiency of the BB84 protocol. Chapter 4 begins with the limitations of present day QKD systems and explicates Quantum Networks as a possible solution. An introduction to classical networking theory is first presented after which some quantum network architectures based on passive optical networks are illustrated. Finally the proposed Quantum City project in conjunction with the eThekwini Municipality is explained. The realization of this project is intended to be complete by the third quarter of 2008 effectively making Durban into the first Quantum City in the world.
Quantum key distribution (QKD) offers unconditional information security by allowing two distant users to establish a common encryption key resilient to hacking. Resultingly, QKD networks interconnecting critical infrastructure and enabling the secure exchange of classified information, can provide a solution to the increasing number of successful cyberattacks. To efficiently deploy quantum networks, the technology must be integrated over existing communication infrastructure, such as optical fibre links. Yet, QKD poses stringent requirements on the conditions of the network over which it is deployed. This work demonstrates the first quantum communication network in Cyprus via the deployment of a multi-node quantum network, exploiting existing commercial underground optical fibre. The network employs bidirectional occupation of fibres and wavelength multiplexing in a ring architecture to achieve, with minimal use of dark fibres, high-rate QKD. Results obtained reveal consistent key generation rates across all nodes, confirming reliable operation in a real-world environment. This deployment highlights the feasibility of leveraging existing telecom infrastructure for quantum-secured communication, marking a significant step toward scalable and cost-effective quantum networks suited for critical applications.
The performances of Quantum Key Distribution (QKD) systems have notably progressed since the early experimental demonstrations and several recent works indicate that the pace of this progression is very likely to be maintained -if not increased- in the future years. In parallel to this fast progression of QKD techniques, commercial products are also being developed, making QKD deployment for securization of some specific “real” data networks more and more likely to occur. It is the goal to the European project Secoqc to deploy a secure long-distance network based on quantum cryptography. It implies the conception of a specific architecture able to connect multiple users that may possibly be very far away from each other while QKD links are currently ″point-to-point only″and intrinsically limited in distance.
Quantum Key Distribution (QKD), also known as quantum cryptography, uses quantum physics to transmit symmetric encryption keys and is secure against attacks by quantum computers. The paper deals with the practical deployment of a commercial QKD device into an existing academic network. As part of the implementation, problems with long-term monitoring, the influence of connectors reflection and the use of different versions of the quantum protocol on the parameters of quantum transmission were solved.
In this paper, we demonstrate for the first time, the coexistence architectures which enable quantum cryptographic systems to use the emerging optical network infrastructure. A vision of a future network that combines classical optical communications with ultra-low power quantum signals over a shared, reconfigurable fiber infrastructure is illustrated. We have used a fiber quantum key distribution (QKD) system to experimentally measure the effective QKD throughput for various types of optical switch elements, including opto-mechanical, lithium niobate, and 2D MEMS. We have investigated QKD coexistence with a commercial EDFA-amplified DWDM system using the experimental setup. These results are an important first step for scaling QKD beyond dedicated point-to-point fiber links and provide a context for understanding the applicability of QKD to the broader optical networking environment.