61,985 research outputs found
Distributed measurement-based quantum computation
We develop a formal model for distributed measurement-based quantum
computations, adopting an agent-based view, such that computations are
described locally where possible. Because the network quantum state is in
general entangled, we need to model it as a global structure, reminiscent of
global memory in classical agent systems. Local quantum computations are
described as measurement patterns. Since measurement-based quantum computation
is inherently distributed, this allows us to extend naturally several concepts
of the measurement calculus, a formal model for such computations. Our goal is
to define an assembly language, i.e. we assume that computations are
well-defined and we do not concern ourselves with verification techniques. The
operational semantics for systems of agents is given by a probabilistic
transition system, and we define operational equivalence in a way that it
corresponds to the notion of bisimilarity. With this in place, we prove that
teleportation is bisimilar to a direct quantum channel, and this also within
the context of larger networks.Comment: 17 page
Automated Verification of Quantum Protocols using MCMAS
We present a methodology for the automated verification of quantum protocols
using MCMAS, a symbolic model checker for multi-agent systems The method is
based on the logical framework developed by D'Hondt and Panangaden for
investigating epistemic and temporal properties, built on the model for
Distributed Measurement-based Quantum Computation (DMC), an extension of the
Measurement Calculus to distributed quantum systems. We describe the
translation map from DMC to interpreted systems, the typical formalism for
reasoning about time and knowledge in multi-agent systems. Then, we introduce
dmc2ispl, a compiler into the input language of the MCMAS model checker. We
demonstrate the technique by verifying the Quantum Teleportation Protocol, and
discuss the performance of the tool.Comment: In Proceedings QAPL 2012, arXiv:1207.055
Distributed Measurement-based Quantum Computation
International audienc
Structure of multipartite entanglement in random cluster-like photonic systems
Quantum networks are natural scenarios for the communication of information
among distributed parties, and the arena of promising schemes for distributed
quantum computation. Measurement-based quantum computing is a prominent example
of how quantum networking, embodied by the generation of a special class of
multipartite states called cluster states, can be used to achieve a powerful
paradigm for quantum information processing. Here we analyze randomly generated
cluster states in order to address the emergence of multipartite correlations
as a function of the density of edges in a given underlying graph. We find that
the most widespread multipartite entanglement does not correspond to the
highest amount of edges in the cluster. We extend the analysis to higher
dimensions, finding similar results, which suggest the establishment of small
world structures in the entanglement sharing of randomised cluster states,
which can be exploited in engineering more efficient quantum information
carriers.Comment: 6 pages, 8 figures, revtex4-
Experimental Demonstration of Five-photon Entanglement and Open-destination Teleportation
Universal quantum error-correction requires the ability of manipulating
entanglement of five or more particles. Although entanglement of three or four
particles has been experimentally demonstrated and used to obtain the extreme
contradiction between quantum mechanics and local realism, the realization of
five-particle entanglement remains an experimental challenge. Meanwhile, a
crucial experimental challenge in multi-party quantum communication and
computation is the so-called open-destination teleportation. During
open-destination teleportation, an unknown quantum state of a single particle
is first teleported onto a N-particle coherent superposition to perform
distributed quantum information processing. At a later stage this teleported
state can be readout at any of the N particles for further applications by
performing a projection measurement on the remaining N-1 particles. Here, we
report a proof-of-principle demonstration of five-photon entanglement and
open-destination teleportation. In the experiment, we use two entangled photon
pairs to generate a four-photon entangled state, which is then combined with a
single photon state to achieve the experimental goals. The methods developed in
our experiment would have various applications e.g. in quantum secret sharing
and measurement-based quantum computation.Comment: 19 pages, 4 figures, submitted for publication on 15 October, 200
Multi-client distributed blind quantum computation with the Qline architecture
Universal blind quantum computing allows users with minimal quantum resources
to delegate a quantum computation to a remote quantum server, while keeping
intrinsically hidden input, algorithm, and outcome. State-of-art experimental
demonstrations of such a protocol have only involved one client. However, an
increasing number of multi-party algorithms, e.g. federated machine learning,
require the collaboration of multiple clients to carry out a given joint
computation. In this work, we propose and experimentally demonstrate a
lightweight multi-client blind quantum computation protocol based on a novel
linear quantum network configuration (Qline). Our protocol originality resides
in three main strengths: scalability, since we eliminate the need for each
client to have its own trusted source or measurement device, low-loss, by
optimizing the orchestration of classical communication between each client and
server through fast classical electronic control, and compatibility with
distributed architectures while remaining intact even against correlated
attacks of server nodes and malicious clients
Weak nonlinearities: A new route to optical quantum computation
Quantum information processing (QIP) offers the promise of being able to do
things that we cannot do with conventional technology. Here we present a new
route for distributed optical QIP, based on generalized quantum non-demolition
measurements, providing a unified approach for quantum communication and
computing. Interactions between photons are generated using weak
non-linearities and intense laser fields--the use of such fields provides for
robust distribution of quantum information. Our approach requires only a
practical set of resources, and it uses these very efficiently. Thus it
promises to be extremely useful for the first quantum technologies, based on
scarce resources. Furthermore, in the longer term this approach provides both
options and scalability for efficient many-qubit QIP.Comment: 7 Pages, 4 Figure
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