16,067 research outputs found
Quantum network communication -- the butterfly and beyond
We study the k-pair communication problem for quantum information in networks
of quantum channels. We consider the asymptotic rates of high fidelity quantum
communication between specific sender-receiver pairs. Four scenarios of
classical communication assistance (none, forward, backward, and two-way) are
considered. (i) We obtain outer and inner bounds of the achievable rate regions
in the most general directed networks. (ii) For two particular networks
(including the butterfly network) routing is proved optimal, and the free
assisting classical communication can at best be used to modify the directions
of quantum channels in the network. Consequently, the achievable rate regions
are given by counting edge avoiding paths, and precise achievable rate regions
in all four assisting scenarios can be obtained. (iii) Optimality of routing
can also be proved in classes of networks. The first class consists of directed
unassisted networks in which (1) the receivers are information sinks, (2) the
maximum distance from senders to receivers is small, and (3) a certain type of
4-cycles are absent, but without further constraints (such as on the number of
communicating and intermediate parties). The second class consists of arbitrary
backward-assisted networks with 2 sender-receiver pairs. (iv) Beyond the k-pair
communication problem, observations are made on quantum multicasting and a
static version of network communication related to the entanglement of
assistance.Comment: 15 pages, 17 figures. Final versio
Continuous Variable Quantum State Sharing via Quantum Disentanglement
Quantum state sharing is a protocol where perfect reconstruction of quantum
states is achieved with incomplete or partial information in a multi-partite
quantum networks. Quantum state sharing allows for secure communication in a
quantum network where partial information is lost or acquired by malicious
parties. This protocol utilizes entanglement for the secret state distribution,
and a class of "quantum disentangling" protocols for the state reconstruction.
We demonstrate a quantum state sharing protocol in which a tripartite entangled
state is used to encode and distribute a secret state to three players. Any two
of these players can collaborate to reconstruct the secret state, whilst
individual players obtain no information. We investigate a number of quantum
disentangling processes and experimentally demonstrate quantum state
reconstruction using two of these protocols. We experimentally measure a
fidelity, averaged over all reconstruction permutations, of F = 0.73. A result
achievable only by using quantum resources.Comment: Published, Phys. Rev. A 71, 033814 (2005) (7 figures, 11 pages
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
Classical Knowledge for Quantum Security
We propose a decision procedure for analysing security of quantum
cryptographic protocols, combining a classical algebraic rewrite system for
knowledge with an operational semantics for quantum distributed computing. As a
test case, we use our procedure to reason about security properties of a
recently developed quantum secret sharing protocol that uses graph states. We
analyze three different scenarios based on the safety assumptions of the
classical and quantum channels and discover the path of an attack in the
presence of an adversary. The epistemic analysis that leads to this and similar
types of attacks is purely based on our classical notion of knowledge.Comment: extended abstract, 13 page
Quantum cryptography: key distribution and beyond
Uniquely among the sciences, quantum cryptography has driven both
foundational research as well as practical real-life applications. We review
the progress of quantum cryptography in the last decade, covering quantum key
distribution and other applications.Comment: It's a review on quantum cryptography and it is not restricted to QK
Multiparty Quantum Communication Using Multiqubit Entanglement and Teleportation
We propose a 2N qubit entangled channel that can be used to teleport N qubits in a network to a single receiver. We describe the structure of this channel and explicitly demonstrate how the protocol works. The channel can be used to implement a scheme in which all parties have to participate in order for the teleportation to be successful. This can be advantageous in various scenarios and we discuss the potential application of this protocol to voting
A Quantum Key Distribution Network Through Single Mode Optical Fiber
Quantum key distribution (QKD) has been developed within the last decade that
is provably secure against arbitrary computing power, and even against quantum
computer attacks. Now there is a strong need of research to exploit this
technology in the existing communication networks. In this paper we have
presented various experimental results pertaining to QKD like Raw key rate and
Quantum bit error rate (QBER). We found these results over 25 km single mode
optical fiber. The experimental setup implemented the enhanced version of BB84
QKD protocol. Based upon the results obtained, we have presented a network
design which can be implemented for the realization of large scale QKD
networks. Furthermore, several new ideas are presented and discussed to
integrate the QKD technique in the classical communication networks.Comment: This paper has been submitted to the 2006 International Symposium on
Collaborative Technologies and Systems (CTS 2006)May 14-17, 2006, Las Vegas,
Nevada, US
Entanglement Verification in Quantum Networks with Tampered Nodes
In this paper, we consider the problem of entanglement verification across
the quantum memories of any two nodes of a quantum network. Its solution can be
a means for detecting (albeit not preventing) the presence of intruders that
have taken full control of a node, either to make a denial-of-service attack or
to reprogram the node. Looking for strategies that only require local
operations and classical communication (LOCC), we propose two entanglement
verification protocols characterized by increasing robustness and efficiency.Comment: 14 pages, 7 figure
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