75 research outputs found
Optimal Routing for Quantum Networks
To fully unleash the potentials of quantum computing, several new challenges and open problems need to be addressed. From a routing perspective, the optimal routing problem, i.e., the problem of jointly designing a routing protocol and a route metric assuring the discovery of the route providing the highest quantum communication opportunities between an arbitrary couple of quantum devices, is crucial. In this paper, the optimal routing problem is addressed for generic quantum network architectures composed by repeaters operating through single atoms in optical cavities. Specifically, we first model the entanglement generation through a stochastic framework that allows us to jointly account for the key physical-mechanisms affecting the end-to-end entanglement rate, such as decoherence time, atom-photon and photon-photon entanglement generation, entanglement swapping, and imperfect Bell-state measurement. Then, we derive the closed-form expression of the end-to-end entanglement rate for an arbitrary path and we design an efficient algorithm for entanglement rate computation. Finally, we design a routing protocol and we prove its optimality when used in conjunction with the entanglement rate as routing metric
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
Quantum Internet: from Communication to Distributed Computing!
In this invited paper, the authors discuss the exponential computing speed-up
achievable by interconnecting quantum computers through a quantum internet.
They also identify key future research challenges and open problems for quantum
internet design and deployment.Comment: 4 pages, three figures, invited pape
Capacity Bounds for Quantum Communications through Quantum Trajectories
In both classical and quantum Shannon's information theory, communication
channels are generally assumed to combine through classical trajectories, so
that the associated network path traversed by the information carrier is
well-defined. Counter-intuitively, quantum mechanics enables a quantum
information carrier to propagate through a quantum trajectory, i.e., through a
path such that the causal order of the constituting communications channels
becomes indefinite. Quantum trajectories exhibit astonishing features, such as
providing non-null capacity even when no information can be sent through any
classical trajectory. But the fundamental question of investigating the
ultimate rates achievable with quantum trajectories is an open and crucial
problem. To this aim, in this paper, we derive closed-form expressions for both
the upper- and the lower-bound on the quantum capacity achievable via a quantum
trajectory. The derived expressions depend, remarkably, on computable
single-letter quantities. Our findings reveal the substantial advantage
achievable with a quantum trajectory over any classical combination of the
communications channels in terms of ultimate achievable communication rates.
Furthermore, we identify the region where a quantum trajectory incontrovertibly
outperforms the amount of transmissible information beyond the limits of
conventional quantum Shannon theory, and we quantify this advantage over
classical trajectories through a conservative estimate
Quantum Switch for the Quantum Internet: Noiseless Communications through Noisy Channels
Counter-intuitively, quantum mechanics enables quantum particles to propagate
simultaneously among multiple space-time trajectories. Hence, a quantum
information carrier can travel through different communication channels in a
quantum superposition of different orders, so that the relative time-order of
the communication channels becomes indefinite. This is realized by utilizing a
quantum device known as quantum switch. In this paper, we investigate, from a
communication-engineering perspective, the use of the quantum switch within the
quantum teleportation process, one of the key functionalities of the Quantum
Internet. Specifically, a theoretical analysis is conducted to quantify the
performance gain that can be achieved by employing a quantum switch for the
entanglement distribution process within the quantum teleportation with respect
to the case of absence of quantum switch. This analysis reveals that, by
utilizing the quantum switch, the quantum teleportation is heralded as a
noiseless communication process with a probability that, remarkably and
counter-intuitively, increases with the noise levels affecting the
communication channels considered in the indefinite-order time combination.Comment: 14 pages, double colum
Augmented Tree-based Routing Protocol for Scalable Ad Hoc Networks
In ad hoc networks scalability is a critical requirement if these
technologies have to reach their full potential. Most of the proposed routing
protocols do not operate efficiently with networks of more than a few hundred
nodes. In this paper, we propose an augmented tree-based address space
structure and a hierarchical multi-path routing protocol, referred to as
Augmented Tree-based Routing (ATR), which utilizes such a structure in order to
solve the scalability problem and to gain good resilience against node
failure/mobility and link congestion/instability. Simulation results and
performance comparisons with existing protocols substantiate the effectiveness
of the ATR.Comment: Routing, mobile ad hoc network, MANET, dynamic addressing,
multi-path, distributed hash table, DH
On Reliability of Dynamic Addressing Routing Protocols in Mobile Ad Hoc Networks
In this paper, a reliability analysis is carried out to state a performance
comparison between two recently proposed proactive routing algorithms. These
protocols are able to scale in ad hoc and sensor networks by resorting to
dynamic addressing, to face with the topology variability, which is typical of
ad hoc, and sensor networks. Numerical simulations are also carried out to
corroborate the results of the analysis.Comment: Proc. of WRECOM '07: Wireless Rural and Emergency Communications
Conference, Roma (Italy), October 200
A Reliability-based Framework for Multi-path Routing Analysis in Mobile Ad-Hoc Networks
Unlike traditional routing procedures that, at the best, single out a unique
route, multi-path routing protocols discover proactively several alternative
routes. It has been recognized that multi-path routing can be more efficient
than traditional one mainly for mobile ad hoc networks, where route failure
events are frequent. Most studies in the area of multi-path routing focus on
heuristic methods, and the performances of these strategies are commonly
evaluated by numerical simulations. The need of a theoretical analysis
motivates such a paper, which proposes to resort to the terminal-pair routing
reliability as performance metric. This metric allows one to assess the
performance gain due to the availability of route diversity. By resorting to
graph theory, we propose an analytical framework to evaluate the tolerance of
multi-path route discovery processes against route failures for mobile ad hoc
networks. Moreover, we derive a useful bound to easily estimate the performance
improvements achieved by multi-path routing with respect to any traditional
routing protocol. Finally, numerical simulation results show the effectiveness
of this performance analysis.Comment: To appear on IJCNDS: International Journal of Communication Networks
and Distributed System
Speeding up Future Video Distribution via Channel-Aware Caching-Aided Coded Multicast
Future Internet usage will be dominated by the consumption of a rich variety
of online multimedia services accessed from an exponentially growing number of
multimedia capable mobile devices. As such, future Internet designs will be
challenged to provide solutions that can deliver bandwidth-intensive,
delay-sensitive, on-demand video-based services over increasingly crowded,
bandwidth-limited wireless access networks. One of the main reasons for the
bandwidth stress facing wireless network operators is the difficulty to exploit
the multicast nature of the wireless medium when wireless users or access
points rarely experience the same channel conditions or access the same content
at the same time. In this paper, we present and analyze a novel wireless video
delivery paradigm based on the combined use of channel-aware caching and coded
multicasting that allows simultaneously serving multiple cache-enabled
receivers that may be requesting different content and experiencing different
channel conditions. To this end, we reformulate the caching-aided coded
multicast problem as a joint source-channel coding problem and design an
achievable scheme that preserves the cache-enabled multiplicative throughput
gains of the error-free scenario,by guaranteeing per-receiver rates unaffected
by the presence of receivers with worse channel conditions.Comment: 11 pages,6 figures,to appear in IEEE JSAC Special Issue on Video
Distribution over Future Interne
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