10 research outputs found
General Scheme for Perfect Quantum Network Coding with Free Classical Communication
This paper considers the problem of efficiently transmitting quantum states
through a network. It has been known for some time that without additional
assumptions it is impossible to achieve this task perfectly in general --
indeed, it is impossible even for the simple butterfly network. As additional
resource we allow free classical communication between any pair of network
nodes. It is shown that perfect quantum network coding is achievable in this
model whenever classical network coding is possible over the same network when
replacing all quantum capacities by classical capacities. More precisely, it is
proved that perfect quantum network coding using free classical communication
is possible over a network with source-target pairs if there exists a
classical linear (or even vector linear) coding scheme over a finite ring. Our
proof is constructive in that we give explicit quantum coding operations for
each network node. This paper also gives an upper bound on the number of
classical communication required in terms of , the maximal fan-in of any
network node, and the size of the network.Comment: 12 pages, 2 figures, generalizes some of the results in
arXiv:0902.1299 to the k-pair problem and codes over rings. Appeared in the
Proceedings of the 36th International Colloquium on Automata, Languages and
Programming (ICALP'09), LNCS 5555, pp. 622-633, 200
Quantum linear network coding as one-way quantum computation
Network coding is a technique to maximize communication rates within a
network, in communication protocols for simultaneous multi-party transmission
of information. Linear network codes are examples of such protocols in which
the local computations performed at the nodes in the network are limited to
linear transformations of their input data (represented as elements of a ring,
such as the integers modulo 2). The quantum linear network coding protocols of
Kobayashi et al [arXiv:0908.1457 and arXiv:1012.4583] coherently simulate
classical linear network codes, using supplemental classical communication. We
demonstrate that these protocols correspond in a natural way to
measurement-based quantum computations with graph states over over qudits
[arXiv:quant-ph/0301052, arXiv:quant-ph/0603226, and arXiv:0704.1263] having a
structure directly related to the network.Comment: 17 pages, 6 figures. Updated to correct an incorrect (albeit
hilarious) reference in the arXiv version of the abstrac
Secure Quantum Network Code without Classical Communication
We consider the secure quantum communication over a network with the presence
of a malicious adversary who can eavesdrop and contaminate the states. The
network consists of noiseless quantum channels with the unit capacity and the
nodes which applies noiseless quantum operations. As the main result, when the
maximum number m1 of the attacked channels over the entire network uses is less
than a half of the network transmission rate m0 (i.e., m1 < m0 / 2), our code
implements secret and correctable quantum communication of the rate m0 - 2m1 by
using the network asymptotic number of times. Our code is universal in the
sense that the code is constructed without the knowledge of the specific node
operations and the network topology, but instead, every node operation is
constrained to the application of an invertible matrix to the basis states.
Moreover, our code requires no classical communication. Our code can be thought
of as a generalization of the quantum secret sharing
A Survey on Quantum Channel Capacities
Quantum information processing exploits the quantum nature of information. It
offers fundamentally new solutions in the field of computer science and extends
the possibilities to a level that cannot be imagined in classical communication
systems. For quantum communication channels, many new capacity definitions were
developed in comparison to classical counterparts. A quantum channel can be
used to realize classical information transmission or to deliver quantum
information, such as quantum entanglement. Here we review the properties of the
quantum communication channel, the various capacity measures and the
fundamental differences between the classical and quantum channels.Comment: 58 pages, Journal-ref: IEEE Communications Surveys and Tutorials
(2018) (updated & improved version of arXiv:1208.1270
Natural dynamics of spin chains
In this thesis, we discuss the natural dynamics of spin chains with regards to their potential role as information carriers in quantum computers and also standalone uses in a quantum computational context. We discuss a range of spin chain devices, expanding existing results on linear chains and simple branched devices to more complex geometries and circular devices. Over the course of this work, we analyse requirements and feasibility of perfect state transfer using the natural dynamics of spin chains and present an extensive investigation into the effects of a number of perturbations on the dynamics of these devices. This includes both fabrication defects and other sources of perturbations. We also present other potential uses of spin chains, including state storage, and introduce an original protocol for the generation of cluster state ladders using only a single linear spin chain.EThOS - Electronic Theses Online ServiceGBUnited Kingdo