12 research outputs found
Topology Adaption for the Quantum Internet
In the quantum repeater networks of the quantum Internet, the varying
stability of entangled quantum links makes dynamic topology adaption an
emerging issue. Here we define an efficient topology adaption method for
quantum repeater networks. The model assumes the random failures of entangled
links and several parallel demands from legal users. The shortest path defines
a set of entangled links for which the probability of stability is above a
critical threshold. The scheme is utilized in a base-graph of the overlay
quantum network to provide an efficient shortest path selection for the demands
of all users of the network. We study the problem of entanglement assignment in
a quantum repeater network, prove its computational complexity, and show an
optimization procedure. The results are particularly convenient for future
quantum networking, quantum-Internet, and experimental long-distance quantum
communications.Comment: 17 pages, Journal-ref: Quant. Inf. Proc. (2018
Towards a Distributed Quantum Computing Ecosystem
The Quantum Internet, by enabling quantum communications among remote quantum
nodes, is a network capable of supporting functionalities with no direct
counterpart in the classical world. Indeed, with the network and communications
functionalities provided by the Quantum Internet, remote quantum devices can
communicate and cooperate for solving challenging computational tasks by
adopting a distributed computing approach. The aim of this paper is to provide
the reader with an overview about the main challenges and open problems arising
with the design of a Distributed Quantum Computing ecosystem. For this, we
provide a survey, following a bottom-up approach, from a communications
engineering perspective. We start by introducing the Quantum Internet as the
fundamental underlying infrastructure of the Distributed Quantum Computing
ecosystem. Then we go further, by elaborating on a high-level system
abstraction of the Distributed Quantum Computing ecosystem. Such an abstraction
is described through a set of logical layers. Thereby, we clarify dependencies
among the aforementioned layers and, at the same time, a road-map emerges
Semi-Quantum Conference Key Agreement (SQCKA)
A need in the development of secure quantum communications is the scalable extension
of key distribution protocols. The greatest advantage of these protocols is the fact that its
security does not rely on mathematical assumptions and can achieve perfect secrecy. In
order to make these protocols scalable, has been developed the concept of Conference
Key Agreements, among multiple users.
In this thesis we propose a key distribution protocol among several users using a
semi-quantum approach. We assume that only one of the users is equipped with quantum
devices and generates quantum states, while the other users are classical, i.e., they are only
equipped with a device capable of measuring or reflecting the information. This approach has
the advantage of simplicity and reduced costs.
We prove our proposal is secure and we present some numerical results on the lower
bounds for the key rate. The security proof applies new techniques derived from some
already well established work.
From the practical point of view, we developed a toolkit called Qis|krypt⟩ that is able to
simulate not only our protocol but also some well-known quantum key distribution protocols.
The source-code is available on the following link:
- https://github.com/qiskrypt/qiskrypt/.Uma das necessidades no desenvolvimento de comunicações quânticas seguras é a extensão
escalável de protocolos de distribuição de chaves. A grande vantagem destes protocolos é o
facto da sua segurança não depender de suposições matemáticas e poder atingir segurança
perfeita. Para tornar estes protocolos escaláveis, desenvolveu-se o conceito de Acordo
de Chaves de Conferência, entre múltiplos utilizadores.
Nesta tese propomos um protocolo para distribuição de chaves entre vários utilizadores
usando uma abordagem semi-quântica. Assumimos que apenas um dos utilizadores está
equipado com dispositivos quânticos e é capaz de gerar estados quânticos, enquanto que
os outros utilizadores são clássicos, isto é, estão apenas equipados com dispositivos capazes
de efectuar uma medição ou refletir a informação. Esta abordagem tem a vantagem de ser
mais simples e de reduzir custos.
Provamos que a nossa proposta é segura e apresentamos alguns resultados numéricos
sobre limites inferiores para o rácio de geração de chaves. A prova de segurança aplica novas
técnicas derivadas de alguns resultados já bem estabelecidos.
Do ponto de vista prático, desenvolvemos uma ferramenta chamada Qis|krypt⟩ que é capaz
de simular não só o nosso protocolo como também outros protocolos distribuição de chaves
bem conhecidos. O código fonte encontra-se disponÃvel no seguinte link:
- https://github.com/qiskrypt/qiskrypt/