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Physics and Computation, 1994. PhysComp '94, Proceedings., Workshop on

17-20 Nov 1994

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Displaying Results 1 - 25 of 35
  • On a method of solving SAT efficiently using the quantum Turing machine

    Publication Year: 1994, Page(s):177 - 185
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (556 KB)

    In this paper, under an assumption that superposed physical states can be observed without collapsing the superposition, we show that the satisfiability problem (SAT, for short) can be solved by a quantum Turing machine in O(2n/4) time. This assumption is not widely accepted among physicists, however, (Aharonov et al., 1993) conjecture that a physical state actually exists as a superpos... View full abstract»

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  • Quantum cellular automata: the physics of computing with arrays of quantum dot molecules

    Publication Year: 1994, Page(s):5 - 13
    Cited by:  Papers (43)  |  Patents (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (632 KB)

    We discuss the fundamental limits of computing using a new paradigm for quantum computation, cellular automata composed of arrays of coulombically coupled quantum dot molecules, which we term quantum cellular automata (QCA). Any logical or arithmetic operation can be performed in this scheme. QCA's provide a valuable concrete example of quantum computation in which a number of fundamental issues c... View full abstract»

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  • Chu spaces: automata with quantum aspects

    Publication Year: 1994, Page(s):186 - 195
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (896 KB)

    Chu spaces are a model of concurrent computation extending automata theory to express branching time and true concurrency. They exhibit in a primitive form the quantum mechanical phenomena of complementarity and uncertainty. The complementarity arises as the duality of information and time, automata and schedules, and states and events. Uncertainty arises when we define a measurement to be a morph... View full abstract»

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  • Can quantum computers have simple Hamiltonians?

    Publication Year: 1994, Page(s):63 - 68
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (432 KB)

    Recently, P. Shor (1994) has shown that quantum computers (computers which can operate simultaneously on a quantum superposition of inputs) permit efficient (i.e. polynomial-time) solutions of problems for which no efficient classical-mechanical solution is known. This has led to renewed interest in the question of whether or not quantum computers can be physically realized. One kind of quantum co... View full abstract»

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  • Thermal logic circuits

    Publication Year: 1994, Page(s):119 - 127
    Cited by:  Papers (2)  |  Patents (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (728 KB)

    Thermal logic is a hypothetical device technology that allows one to analyze the energetics of computing machines in a simpler setting than real device technologies. The paper describes the rudiments of thermal logic, and uses it to analyze reversible logic pipelines. The similarity between thermal logic and electronic logic is explained, and thermal analogs of electronic devices and circuits are ... View full abstract»

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  • Results on two-bit gate design for quantum computers

    Publication Year: 1994, Page(s):14 - 23
    Cited by:  Papers (1)  |  Patents (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (484 KB)

    We present numerical results which show how two-bit logic gates can be used in the design of a quantum computer. We show that the Toffoli gate, which is the universal gate for all classical reversible computation, can be implemented using a particular sequence of exactly five two-bit gates. An arbitrary three-bit unitary gate, which can be used to build up any arbitrary quantum computation, can be... View full abstract»

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  • Statistical mechanics of combinatorial search

    Publication Year: 1994, Page(s):196 - 202
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (520 KB)

    The statistical mechanics of combinatorial search problems is described using the example of the well-known NP-complete graph coloring problem. A simple parameter describing the problem structure predicts the difficulty of solving the problem, on average. However, because of the large variance associated with this prediction, it is of limited direct use for individual instances. Additional paramet... View full abstract»

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  • Quantum oblivious transfer is secure against all individual measurements

    Publication Year: 1994, Page(s):69 - 77
    Cited by:  Papers (5)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (604 KB)

    Shows that the BBCS-protocol (Bennett, Brassard, Cre´peau and Skubiszewska, CRYPTO'91, 1992) implementing one of the most important cryptographic primitives-`oblivious transfer'-is secure against any individual measurement allowed by quantum mechanics. We analyze the common situation where successive measurements on the same photon could be used to cheat in the protocol. We model this situat... View full abstract»

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  • A reversible instruction set architecture and algorithms

    Publication Year: 1994, Page(s):128 - 134
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (400 KB)

    We describe a reversible instruction set architecture using recently developed reversible logic design techniques. Such an architecture has the dual advantage of being able to run backwards and of being, in theory, implementable so as to dissipate less than log 2 kT joules per bit operation. We analyze several basic control structures and algorithms on the architecture, showing that, for example, ... View full abstract»

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  • Space and time in computation, topology and discrete physics

    Publication Year: 1994, Page(s):44 - 53
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (772 KB)

    A step can be regarded as an elementary ordering of two objects (or operators). A step is a distinction combined with an action that crosses the boundary of that distinction. The elementary step can be seen as a reference, as a division of space or as a tick of a clock. By looking at the structure of a step, we provide a context that unifies specific aspects of special relativity, Laws of Form, to... View full abstract»

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  • Multiprocessor architectures and physical law

    Publication Year: 1994, Page(s):24 - 29
    Cited by:  Papers (5)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (480 KB)

    We show that all highly symmetrical interconnection topologies for multiprocessors with low diameter require very long interconnect lengths. Therefore, such multicomputers do not scale well in the physical world with 3 dimensions. On the other hand, highly irregular (random) interconnection topologies have a very large subgraph of diameter two and therefore also require very long interconnect leng... View full abstract»

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  • Phase transitions and coarse-grained search

    Publication Year: 1994, Page(s):203 - 208
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (404 KB)

    Abstraction is a method for solving a variety of computational search problems that uses coarse-graining to simplify the search. When a coarse-grained, or abstract, solution is found, it is then refined to give a complete solution. We present a model of this abstraction process for constraint satisfaction problems, a well-known class of NP-complete search problems. This model is then used to ident... View full abstract»

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  • Physical computation and parallelism (constructive postmodern physics)

    Publication Year: 1994, Page(s):78 - 87
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (504 KB)

    There is increasing evidence that information may be the basic stuff of the universe. We consider this proposition in the light of Bohm and Hiley's (1993) quantum potential, the work of the ANPA group on the combinatorial hierarchy, and the natural philosophies of G. Kron (1963) and M. Jessel (1962). We compare and contrast the philosophical backgrounds of both these and the more conventional Cope... View full abstract»

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  • Encoded arithmetic for reversible logic

    Publication Year: 1994, Page(s):135 - 142
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (556 KB)

    The CCD based implementations of reversible logic consume a constant amount of energy per switching event which depends only on the charge packet size and not on the interconnect length. Within this model of computation, it seems possible to leverage data, encoding to reduce the number of switching events for the computation, resulting in lower overall computation energy. We explore the applicabil... View full abstract»

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  • Coupling computations through space

    Publication Year: 1994, Page(s):160 - 168
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (688 KB)

    A conceptual framework for models of coupled computations is developed, based on the assumption that the computations are performed by a population of processing agents whose structure is derived from Turing machines. As a fundamental premise, the agents are embedded in a well-defined space which ultimately provides constraints on the individual movements, thus enabling their autonomous behaviour.... View full abstract»

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  • Zig-zag path to understanding [physical limits of information handling]

    Publication Year: 1994, Page(s):54 - 59
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (420 KB)

    Our understanding of the fundamental physical limits of information handling has developed along a very convoluted path. Most of the initially plausible physical conjectures have turned out to be wrong. A participant's personal view of these events as not a disciplined contribution to the history of science. The author does, however, list his own mistakes along with those of others View full abstract»

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  • Impact of locality and dimensionality limits on architectural trends

    Publication Year: 1994, Page(s):30 - 35
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (480 KB)

    Since computing is a physical activity, all forms of computing must obey locality constraints imposed by physics. Unknowingly, many software abstractions violate locality constraints because they represent high dimensional topologies that have higher degrees of freedom than is uniformly implementable by the underlying physical architecture. This semantic gap between abstractions implemented in the... View full abstract»

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  • The Boltzmann entropy and randomness tests

    Publication Year: 1994, Page(s):209 - 216
    Cited by:  Papers (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (672 KB)

    In the context of the dynamical systems of classical mechanics, we introduce two new notions called “algorithmic fine-grain and coarse-grain entropy”. The fine-grain algorithmic entropy is, on the one hand, a simple variant of the Martin-Lof (and other) randomness tests, and, on the other hand, a connecting link between description (Kolmogorov) complexity, Gibbs entropy and Boltzmann e... View full abstract»

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  • Bit-string physics: a novel “theory of everything”

    Publication Year: 1994, Page(s):88 - 94
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (620 KB)

    Encodes the quantum numbers of the standard model of quarks and leptons using constructed bit-strings of length 256. These label a growing universe of bit-strings of growing length that eventually construct a finite and discrete space-time with reasonable cosmological properties. Coupling constants and mass ratios, computed from closure under XOR and a statistical hypothesis, using only h, c and m... View full abstract»

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  • Some results on invertible cellular automata

    Publication Year: 1994, Page(s):143 - 150
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (604 KB)

    Addresses certain questions concerning invertible cellular automata, and presents new results in this area. Specifically, we explicitly construct a cellular automaton in a class (a residual class) previously known not to be empty only via a nonconstructive existence proof. This class contains cellular automata that are invertible on every finite support but not on an infinite lattice. Moreover, we... View full abstract»

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  • Evolution, entropy, and parallel computation

    Publication Year: 1994, Page(s):246 - 254
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (480 KB)

    The relationship between evolution and entropy is described for a model of self-reproducing parallel computation. As was recently shown by Thearling and Ray (1994), the performance of some types of parallel computation can be increased though a process analogous to evolution by natural selection. The work discussed in this paper explores the process by which evolution manipulates the entropy of in... View full abstract»

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  • The complexity and entropy of Turing machines

    Publication Year: 1994, Page(s):227 - 232
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (528 KB)

    Addresses the relationship between dynamical systems theory and theoretical computer science, in particular the dynamical, information-theoretic and computational properties of systems that compute. These properties have been studied in cellular automata and the symbolic dynamics of maps over the unit interval, but have never been addressed in compact systems known to be capable of universal compu... View full abstract»

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  • Quantum waveguide structures and devices

    Publication Year: 1994, Page(s):169 - 176
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (544 KB)

    Nanometer structures in semiconductor heterojunction systems have been studied for several years and have conclusively shown evidence for quantum interference phenomena and granular effects due to the finite number of electrons and impurities. Various proposals have been made for novel devices based on such effects, which would serve as the basis for terabit memories and ultra-dense processing ele... View full abstract»

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  • Research toward nanoelectronic computing technologies in Japan

    Publication Year: 1994, Page(s):1 - 4
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (304 KB)

    A perspective of the research activities in Japan aimed at the development of new computing technologies based on structures with ultra-small dimensions is presented. Examples are given of work toward the development of resonant tunneling circuits, electron-wave interference and single-electron tunneling devices, and atomic-scale fabrication technologies View full abstract»

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  • The stabilisation of quantum computations

    Publication Year: 1994, Page(s):60 - 62
    Cited by:  Papers (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (180 KB)

    A quantum computer is a device capable of performing computational tasks that depend on characteristically quantum mechanical effects, in particular coherent quantum superposition. Such devices can efficiently perform classes of computation (e.g. factorisation) which are believed to be intractable on any classical computer. This makes it highly desirable to construct such devices. In this paper, w... View full abstract»

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