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IBM Journal of Research and Development

Issue 1 • Date Jan. 2004

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Displaying Results 1 - 14 of 14
  • Preface

    Publication Year: 2004 , Page(s): 3
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (21 KB)  

    This issue of the IBM Journal of Research and Development contains papers honoring the life and career of IBM Fellow Charles H. Bennett on the occasion of his sixtieth birthday. Most of the papers are based on talks presented at a symposium held at the IBM Thomas J. Watson Research Center in Yorktown Heights, New York, on May 8 and 9, 2003. Nearly one hundred participants, some from far distant points on the globe, contributed to the lively discussions and celebrations at that symposium. The papers reflect the active intellectual atmosphere that prevailed at the symposium and show the wide range of Charlie's seminal contributions to several areas of fundamental science. Some of the authors have dug deep into their archives and unearthed photographic and other mementos of their interactions with Charlie, which the reader will find throughout the issue. View full abstract»

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  • Can complex structures be generically stable in a noisy world?

    Publication Year: 2004 , Page(s): 5 - 12
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (103 KB)  

    Toom's “NEC” cellular automaton is a simple model or dynamical “rule” that succeeds in producing two-phase coexistence generically, i.e., over a nonzero fraction of its two-dimensional parameter space. This paper reviews and explains the behavior of the NEC rule and discusses the implications of the rule for the generic stabilization of complex structures. Much of the discussion is based on work performed almost twenty years ago by Charles Bennett and the author. View full abstract»

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  • A pedestrian's introduction to spacetime crystallography

    Publication Year: 2004 , Page(s): 13 - 29
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (242 KB)  

    Ordinary crystallography deals with regular, discrete, static arrangements in space. Of course, dynamic considerations—and thus the additional dimension of time—must be introduced when one studies the origin of crystals (since they are emergent structures) and their physical properties such as conductivity and compressibility. The space and time of the dynamics in which the crystal is embedded are assumed to be those of ordinary continuous mechanics. In this paper, we take as the starting point a spacetime crystal, that is, the spacetime structure underlying a discrete and regular dynamics. A dynamics of this kind can be viewed as a “crystalline computer.” After considering transformations that leave this structure invariant, we turn to the possible states of this crystal, that is, the discrete spacetime histories that can take place in it and how they transform under different crystal transformations. This introduction to spacetime crystallography provides the rationale for making certain definitions and addressing specific issues; presents the novel features of this approach to crystallography by analogy and by contrast with conventional crystallography; and raises issues that have no counterpart there. View full abstract»

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  • Five big questions with pretty simple answers

    Publication Year: 2004 , Page(s): 31 - 45
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (130 KB)  

    Under the roof of one controversial assumption about physics, we discuss five big questions that can be addressed using concepts from a modern understanding of digital informational processes. The assumption is called finite nature. The digital mechanics model is obtained by applying the assumption to physics. The questions are as follows: 1. What is the origin of spin? 2. Why are there symmetries and CPT (charge conjugation, parity, and time reversal) 3. What is the origin of length? 4. What does a process model of motion tell us? 5. Can the finite nature assumption account for the efficacy of quantum mechanics? Digital mechanics predicts that for every continuous symmetry of physics there will be some microscopic process that violates that symmetry. We are, therefore, able to suggest experimental tests of the finite nature hypothesis. Finally, we explain why experimental evidence for such violations might be elusive and hard to recognize. View full abstract»

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  • The early days of experimental quantum cryptography

    Publication Year: 2004 , Page(s): 47 - 52
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (951 KB)  

    This paper describes the first quantum cryptography experiment, performed at the IBM Thomas J. Watson Research Center in the summer of 1989 by Charles H. Bennett and the author. The apparatus and some of the lesser-known details of the experiment are illustrated and discussed, and quantum cryptography is discussed in the light of some of the more recent research. Also included as an appendix is a short essay about Bennett written by Rolf Landauer. View full abstract»

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  • Copenhagen computation: How I learned to stop worrying and love Bohr

    Publication Year: 2004 , Page(s): 53 - 61
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (120 KB)  

    To celebrate the 60th birthday of Charles H. Bennett, I 1) publicly announce my referee reports for the original dense coding and teleportation papers, 2) present a very economical solution to the Bernstein–Vazirani problem that does not even hint at interference between multiple universes, and 3) describe how I inadvertently reinvented the Copenhagen interpretation in the course of constructing a simple, straightforward, and transparent introduction to quantum mechanics for computer scientists. View full abstract»

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  • What is actually teleported?

    Publication Year: 2004 , Page(s): 63 - 69
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    There are no “unknown quantum states.“ The phrase is self-contradictory. Moreover, Alice and Bob are only inanimate objects: They know nothing. What is teleported instantaneously from one system (Alice) to another system (Bob) is the applicability of the preparer's knowledge of the state of a particular qubit in the systems. The operation necessitates the use of dual classical and quantum channels. Other examples of dual transmission, including “unspeakable information,” are presented and discussed. This paper also includes a narrative of my recollections of how quantum teleportation was conceived. View full abstract»

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  • Is entanglement monogamous?

    Publication Year: 2004 , Page(s): 71 - 78
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2579 KB)  

    In this paper I discuss some of the early history of quantum information theory. By considering the question of whether entanglement is “monogamous,” I illustrate Charles Bennett's influence on modern quantum information theory. Finally, I review our recent answers to this entanglement question and its relation to Bell inequalities. View full abstract»

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  • Illustrating the concept of quantum information

    Publication Year: 2004 , Page(s): 79 - 85
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (92 KB)  

    Over the past decade, quantum information theory has developed into a vigorous field of research despite the fact that quantum information, as a precise concept, is undefined. Indeed, the very idea of viewing quantum states as carriers of some kind of information (albeit unknowable in classical terms) leads naturally to interesting questions that might otherwise never have been asked, and corresponding new insights. We discuss some illustrative examples, including a strengthening of the well-known no-cloning theorem leading to a property of permanence for quantum information, and considerations arising from information compression that reflect on fundamental issues. View full abstract»

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  • TelePOVM—A generalized quantum teleportation scheme

    Publication Year: 2004 , Page(s): 87 - 97
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (123 KB)  

    In this paper, we show that quantum teleportation is a special case of a generalized Einstein-Podolsky-Rosen (EPR) nonlocality. On the basis of the connection between teleportation and generalized measurements, we define conclusive teleportation. We show that perfect conclusive teleportation can be obtained with any pure entangled state, and it can be arbitrarily approached with a particular mixed state. View full abstract»

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  • Picturing qubits in phase space

    Publication Year: 2004 , Page(s): 99 - 110
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    Focusing particularly on one-qubit and two-qubit systems, I explain how the quantum state of a system of n qubits can be expressed as a real function—a generalized Wigner function—on a discrete 2n × 2n phase pace. The phase space is based on the finite field having 2n elements, and its geometric structure leads naturally to the construction of a complete set of 2n + 1 mutually conjugate bases. View full abstract»

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  • Some bipartite states do not arise from channels

    Publication Year: 2004 , Page(s): 111 - 114
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (82 KB)  

    It is well known that the action of a quantum channel on a state can be represented, using an auxiliary space, as the partial trace of an associated bipartite state. Recently, it was observed that for the bipartite state associated with the optimal average input of the channel, the entanglement of formation is simply the entropy of the reduced density matrix minus the Holevo capacity. It is natural to ask if every bipartite state can be associated with some channel in this way. We show that the answer is negative. View full abstract»

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  • The adaptive classical capacity of a quantum channel, or Information capacities of three symmetric pure states in three dimensions

    Publication Year: 2004 , Page(s): 115 - 137
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1792 KB)  

    We investigate the capacity of three symmetric quantum states in three real dimensions to carry classical information. Several such capacities have already been defined, depending on what operations are allowed in the protocols that the sender uses to encode classical information into these quantum states, and that the receiver uses to decode it. These include the C1,1 capacity, which is the capacity achievable if separate measurements must be used for each of the received states, and the C1,∞ capacity, which is the capacity achievable if joint measurements are allowed on the tensor product of all of the received states. We discover a new classical information capacity of quantum channels, the adaptive capacity C1,A, which lies strictly between the C1,1 and the C1,∞ capacities. The adaptive capacity allows the use of what is known as the LOCC (local operations and classical communication) model of quantum operations for decoding the channel outputs. This model requires each of the signals to be measured by a separate apparatus, but allows the quantum states of these signals to be measured in stages, with the first stage partially reducing their quantum states; measurements in subsequent stages may depend on the results of a classical computation taking as input the outcomes of the first round of measurements. We also show that even in three dimensions, with the information carried by an ensemble containing three pure states, achieving the C1,1 capacity may require a positive operator valued measure (POVM) with six outcomes. View full abstract»

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  • Quantum information isomorphism: Beyond the dilemma of the Scylla of ontology and the Charybdis of instrumentalism

    Publication Year: 2004 , Page(s): 139 - 147
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (101 KB)  

    In order to deal most effectively with the unanalyzable quantum whole, the Copenhagen interpretation takes as a “frame of reference” the preparation parameters and outcomes of measurements. It represents a passive, Ptolemaic-like instrumentalism directly related to “what we see in the sky,” i.e., to the “surface” of reality. However, the notion of quantum information leads to an active, Copernican-like realism which involves an (intrinsic) ordering principle and the view that the quantum whole is analyzable. It is then possible to consider subsystems as localized in space, controlled individually, and communicated. This makes it natural to treat quantum information (quantum states) not merely as knowledge. Moreover, it involves complementarity between local and nonlocal information. To avoid the dilemma between the Scylla of ontology and the Charybdis of instrumentalism, we propose the concept of quantum information isomorphism, according to which the quantum description of nature is isomorphic to nature itself. By definition it is not just one-to-one mapping, but it preserves the full structure of nature. In particular, it allows the treatment of the wave function of isomorphic images of quantum systems in the laboratory, implying that quantum information is indeed carried by these quantum systems. View full abstract»

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Aims & Scope

The IBM Journal of Research and Development is a peer-reviewed technical journal, published bimonthly, which features the work of authors in the science, technology and engineering of information systems.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Clifford A. Pickover
IBM T. J. Watson Research Center