155 research outputs found
A 2D Quantum Walk Simulation of Two-Particle Dynamics
Multi-dimensional quantum walks can exhibit highly non-trivial topological
structure, providing a powerful tool for simulating quantum information and
transport systems. We present a flexible implementation of a 2D optical quantum
walk on a lattice, demonstrating a scalable quantum walk on a non-trivial graph
structure. We realized a coherent quantum walk over 12 steps and 169 positions
using an optical fiber network. With our broad spectrum of quantum coins we
were able to simulate the creation of entanglement in bipartite systems with
conditioned interactions. Introducing dynamic control allowed for the
investigation of effects such as strong non-linearities or two-particle
scattering. Our results illustrate the potential of quantum walks as a route
for simulating and understanding complex quantum systems
Witnessing effective entanglement over a 2km fiber channel
We present a fiber-based continuous-variable quantum key distribution system.
In the scheme, a quantum signal of two non-orthogonal weak optical coherent
states is sent through a fiber-based quantum channel. The receiver
simultaneously measures conjugate quadratures of the light using two homodyne
detectors. From the measured Q-function of the transmitted signal, we estimate
the attenuation and the excess noise caused by the channel. The estimated
excess noise originating from the channel and the channel attenuation including
the quantum efficiency of the detection setup is investigated with respect to
the detection of effective entanglement. The local oscillator is considered in
the verification. We witness effective entanglement with a channel length of up
to 2km.Comment: 11 pages, 5 figure
A Quantum Internet Architecture
Entangled quantum communication is advancing rapidly, with laboratory and
metropolitan testbeds under development, but to date there is no unifying
Quantum Internet architecture. We propose a Quantum Internet architecture
centered around the Quantum Recursive Network Architecture (QRNA), using
RuleSet-based connections established using a two-pass connection setup.
Scalability and internetworking (for both technological and administrative
boundaries) are achieved using recursion in naming and connection control. In
the near term, this architecture will support end-to-end, two-party
entanglement on minimal hardware, and it will extend smoothly to multi-party
entanglement and the use of quantum error correction on advanced hardware in
the future. For a network internal gateway protocol, we recommend (but do not
require) qDijkstra with seconds per Bell pair as link cost for routing; the
external gateway protocol is designed to build recursively. The strength of our
architecture is shown by assessing extensibility and demonstrating how robust
protocol operation can be confirmed using the RuleSet paradigm.Comment: 17 pages, 7 numbered figure
Optical Quantum Computation
We review the field of Optical Quantum Computation, considering the various
implementations that have been proposed and the experimental progress that has
been made toward realizing them. We examine both linear and nonlinear
approaches and both particle and field encodings. In particular we discuss the
prospects for large scale optical quantum computing in terms of the most
promising physical architectures and the technical requirements for realizing
them
Quantum Internet Protocol Stack: a Comprehensive Survey
Classical Internet evolved exceptionally during the last five decades, from a
network comprising a few static nodes in the early days to a leviathan
interconnecting billions of devices. This has been possible by the separation
of concern principle, for which the network functionalities are organized as a
stack of layers, each providing some communication functionalities through
specific network protocols. In this survey, we aim at highlighting the
impossibility of adapting the classical Internet protocol stack to the Quantum
Internet, due to the marvels of quantum mechanics. Indeed, the design of the
Quantum Internet requires a major paradigm shift of the whole protocol stack
for harnessing the peculiarities of quantum entanglement and quantum
information. In this context, we first overview the relevant literature about
Quantum Internet protocol stack. Then, stemming from this, we sheds the light
on the open problems and required efforts toward the design of an effective and
complete Quantum Internet protocol stack. To the best of authors' knowledge, a
survey of this type is the first of its own. What emerges from this analysis is
that the Quantum Internet, though still in its infancy, is a disruptive
technology whose design requires an inter-disciplinary effort at the border
between quantum physics, computer and telecommunications engineering
Bell nonlocality
Bell's 1964 theorem, which states that the predictions of quantum theory
cannot be accounted for by any local theory, represents one of the most
profound developments in the foundations of physics. In the last two decades,
Bell's theorem has been a central theme of research from a variety of
perspectives, mainly motivated by quantum information science, where the
nonlocality of quantum theory underpins many of the advantages afforded by a
quantum processing of information. The focus of this review is to a large
extent oriented by these later developments. We review the main concepts and
tools which have been developed to describe and study the nonlocality of
quantum theory, and which have raised this topic to the status of a full
sub-field of quantum information science.Comment: 65 pages, 7 figures. Final versio
The Strict-Sense Nonblocking Multirate l
This paper considers the nonblocking conditions for a multirate logd(N,0,p) switching network at the connection level. The necessary and sufficient conditions for the discrete bandwidth model, as well as sufficient and, in particular cases, also necessary conditions for the continuous bandwidth model, were given. The results given for dn-1/2f0≥f1+1 in the discrete bandwidth model are the same as those proposed by Hwang et al. (2005); however, in this paper, these results were extended to other values of f0, f1, and d. In the continuous bandwidth model for B+b>1, the results given in this paper are also the same as those by Hwang et al. (2005); however, for B+b≤1, it was proved that a smaller number of vertically stacked logdN switching networks are needed
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