Applications of Atomic Ensembles In Distributed Quantum Computing

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Title Applications of Atomic Ensembles In Distributed Quantum Computing
Author Zwierz, Marcin; Kok, Pieter
Journal Name International Journal of Quantum Information
Year Published 2010
Place of publication Singapore
Publisher World Scientific Publishing Co. Pte. Ltd.
Abstract Thesis chapter. The fragility of quantum information is a fundamental constraint faced by anyone trying to build a quantum computer. A truly useful and powerful quantum computer has to be a robust and scalable machine. In the case of many qubits which may interact with the environment and their neighbors, protection against decoherence becomes quite a challenging task. The scalability and decoherence issues are the main difficulties addressed by the distributed model of quantum computation. A distributed quantum computer consists of a large quantum network of distant nodes — stationary qubits which communicate via flying qubits. Quantum information can be transferred, stored, processed and retrieved in decoherence-free fashion by nodes of a quantum network realized by an atomic medium — an atomic quantum memory. Atomic quantum memories have been developed and demonstrated experimentally in recent years. With the help of linear optics and laser pulses, one is able to manipulate quantum information stored inside an atomic quantum memory by means of electromagnetically induced transparency and associated propagation phenomena. Any quantum computation or communication necessarily involves entanglement. Therefore, one must be able to entangle distant nodes of a distributed network. In this article, we focus on the probabilistic entanglement generation procedures such as well-known DLCZ protocol. We also demonstrate theoretically a scheme based on atomic ensembles and the dipole blockade mechanism for generation of inherently distributed quantum states so-called cluster states. In the protocol, atomic ensembles serve as single qubit systems. Hence, we review single-qubit operations on qubit defined as collective states of atomic ensemble. Our entangling protocol requires nearly identical single-photon sources, one ultra-cold ensemble per physical qubit, and regular photodetectors. The general entangling procedure is presented, as well as a procedure that generates in a single step Q-qubit GHZ states with success probability p_success ~ η^Q/2, where η is the combined detection and source efficiency. This is significantly more efficient than any known robust probabilistic entangling operation. The GHZ states form the basic building block for universal cluster states, a resource for the one-way quantum computer.
Peer Reviewed Yes
Published Yes
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Copyright Statement Electronic version of an article published in International Journal of Quantum Information, Vol. 8(1-2), 2010, pp. 181-218, Copyright World Scientific Publishing Company
Volume 8
Issue Number 1-2
Page from 181
Page to 218
ISSN 0219-7499
Date Accessioned 2011-12-05
Language en_US
Faculty Faculty of Science, Environment, Engineering and Technology
Subject Quantum Information, Computation and Communication; Quantum Optics; Quantum Physics
Publication Type Journal Articles (Refereed Article)
Publication Type Code c1x

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