20,336 research outputs found
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
Finite-Block-Length Analysis in Classical and Quantum Information Theory
Coding technology is used in several information processing tasks. In
particular, when noise during transmission disturbs communications, coding
technology is employed to protect the information. However, there are two types
of coding technology: coding in classical information theory and coding in
quantum information theory. Although the physical media used to transmit
information ultimately obey quantum mechanics, we need to choose the type of
coding depending on the kind of information device, classical or quantum, that
is being used. In both branches of information theory, there are many elegant
theoretical results under the ideal assumption that an infinitely large system
is available. In a realistic situation, we need to account for finite size
effects. The present paper reviews finite size effects in classical and quantum
information theory with respect to various topics, including applied aspects
Field test of quantum key distribution in the Tokyo QKD Network
A novel secure communication network with quantum key distribution in a
metropolitan area is reported. Different QKD schemes are integrated to
demonstrate secure TV conferencing over a distance of 45km, stable long-term
operation, and application to secure mobile phones.Comment: 21 pages, 19 figure
Energy efficient mining on a quantum-enabled blockchain using light
We outline a quantum-enabled blockchain architecture based on a consortium of
quantum servers. The network is hybridised, utilising digital systems for
sharing and processing classical information combined with a fibre--optic
infrastructure and quantum devices for transmitting and processing quantum
information. We deliver an energy efficient interactive mining protocol enacted
between clients and servers which uses quantum information encoded in light and
removes the need for trust in network infrastructure. Instead, clients on the
network need only trust the transparent network code, and that their devices
adhere to the rules of quantum physics. To demonstrate the energy efficiency of
the mining protocol, we elaborate upon the results of two previous experiments
(one performed over 1km of optical fibre) as applied to this work. Finally, we
address some key vulnerabilities, explore open questions, and observe
forward--compatibility with the quantum internet and quantum computing
technologies.Comment: 25 pages, 5 figure
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