Showing papers by "IBM published in 1992"

Communication via One- and Two-Particle Operators on Einstein-Podolsky-Rosen States

Abstract: As is well known, operations on one particle of an Einstein-Podolsky-Rosen (EPR) pair cannot influence the marginal statistics of measurements on the other particle. We characterize the set of states accessible from an initial EPR state by one-particle operations and show that in a sense they allow two bits to be encoded reliably in one spin-1/2 particle: One party, ``Alice,'' prepares an EPR pair and sends one of the particles to another party, ``Bob,'' who applies one of four unitary operators to the particle, and then returns it to Alice. By measuring the two particles jointly, Alice can now reliably learn which operator Bob used.

Class-based n -gram models of natural language

Abstract: We address the problem of predicting a word from previous words in a sample of text. In particular, we discuss n-gram models based on classes of words. We also discuss several statistical algorithms for assigning words to classes based on the frequency of their co-occurrence with other words. We find that we are able to extract classes that have the flavor of either syntactically based groupings or semantically based groupings, depending on the nature of the underlying statistics.

Quantum cryptography using any two nonorthogonal states

Abstract: Quantum techniques for key distribution---the classically impossible task of distributing secret information over an insecure channel whose transmissions are subject to inspection by an eavesdropper, between parties who share no secret initially---have been proposed using (a) four nonorthogonally polarized single-photon states or low-intensity light pulses, and (b) polarization-entangled or spacetime-entangled two-photon states. Here we show that in principle any two nonorthogonal quantum states suffice, and describe a practical interferometric realization using low-intensity coherent light pulses.

Quantum cryptography without Bell's theorem.

Abstract: Ekert has described a cryptographic scheme in which Einstein-Podolsky-Rosen (EPR) pairs of particles are used to generate identical random numbers in remote places, while Bell's theorem certifies that the particles have not been measured in transit by an eavesdropper. We describe a related but simpler EPR scheme and, without invoking Bell's theorem, prove it secure against more general attacks, including substitution of a fake EPR source. Finally we show our scheme is equivalent to the original 1984 key distribution scheme of Bennett and Brassard, which uses single particles instead of EPR pairs.

Pricing via Processing or Combatting Junk Mail

Abstract: We present a computational technique for combatting junk mail in particular and controlling access to a shared resource in general. The main idea is to require a user to compute a moderately hard, but not intractable, function in order to gain access to the resource, thus preventing frivolous use. To this end we suggest several pricing Junctions, based on, respectively, extracting square roots modulo a prime, the Fiat-Shamir signature scheme, and the Ong-Schnorr-Shamir (cracked) signature scheme.

Perfectly-Secure Key Distribution for Dynamic Conferences

Abstract: A key distribution scheme for dynamic conferences is a method by which initially an (off-line) trusted server distributes private individual pieces of information to a set of users. Later any group of users of a given size (a dynamic conference) is able to compute a common secure key. In this paper we study the theory and applications of such perfectly secure systems. In this setting, any group of t users can compute a common key by each user computing using only his private piece of information and the identities of the other t - 1 group users. Keys are secure against coalitions of up to k users, that is, even if k users pool together their pieces they cannot compute anything about a key of any t-size conference comprised of other users.First we consider a non-interactive model where users compute the common key without any interaction. We prove a lower hound on the size of the user's piece of information of (k+t-1 t-1) times the size of the common key. We then establish the optimality of this bound, by describing and analyzing a scheme which exactly meets this limitation (the construction extends the one in [2]). Then, we consider the model where interaction is allowed in the common key computation phase, and show a gap between the models by exhibiting an interactive scheme in which the user's information is only k + t - 1 times the size of the common key. We further show various applications and useful modifications of our basic scheme. Finally, we present its adaptation to network topologies with neighborhood constraints.

Extending and formalizing the framework for information systems architecture

Abstract: John Zachman introduced a framework for information systems architecture (ISA) that has been widely adopted by systems analysts and database designers. It provides a taxonomy for relating the concepts that describe the real work to the concepts that describe an information system and its implementation. The ISA framework has a simple elegance that makes it easy to remember, yet it draws attention to fundamental distinctions that are often overlooked in systems design. This paper presents the framework and its recent extensions and shows how it can be formalized in the notation of conceptual graphs.

ARIES: a transaction recovery method supporting fine-granularity locking and partial rollbacks using write-ahead logging

Abstract: DB2TM, IMS, and TandemTM systems. ARIES is applicable not only to database management systems but also to persistent object-oriented languages, recoverable file systems and transaction-based operating systems. ARIES has been implemented, to varying degrees, in IBM's OS/2TM Extended Edition Database Manager, DB2, Workstation Data Save Facility/VM, Starburst and QuickSilver, and in the University of Wisconsin's EXODUS and Gamma database machine.

Configurational bias Monte Carlo: a new sampling scheme for flexible chains

Abstract: We propose a novel approach that allows efficient numerical simulation of systems consisting of flexible chain molecules. The method is especially suitable for the numerical simulation of dense chain systems and monolayers. A new type of Monte Carlo move is introduced that makes it possible to carry out large scale conformational changes of the chain molecule in a single trial move. Our scheme is based on the selfavoiding random walk algorithm of Rosenbluth and Rosenbluth. As an illustration, we compare the results of a calculation of mean-square end to end lengths for single chains on a two-dimensional square lattice with corresponding data gained from other simulations.

Magnetotransport properties of p-type (In,Mn)As diluted magnetic III-V semiconductors.

Abstract: Magnetotransport properties of p-type (In,Mn)As, a new diluted magnetic semiconductor based on a III-V semiconductor, are studied. The interaction between the holes and the Mn 3d spins is manifested in the anomalous Hall effect, which dominates the Hall resistivity from low temperature (0.4 K) to nearly room temperature, and in the formation of partial ferromagnetic order below 7.5 K, which is a cooperative phenomenon related to carrier localization. The coexistence of remanent magnetization and unsaturated spins as well as the large negative magnetoresistance at low temperatures is explained by the formation of large bound magnetic polarons.

Transmission through barriers and resonant tunneling in an interacting one-dimensional electron gas.

Abstract: We study theoretically transport of a one-dimensional single-channel interacting electron gas through barriers or constrictions. We find that electrons with repulsive interactions, incident upon a single barrier, are completely reflected at zero temperature. At finite temperature (T), the conductance is shown to vanish as a power of T, and at zero temperature, power-law current-voltage characteristics are predicted. For attractive interactions, we predict perfect transmission at zero temperature, with similar power-law corrections. We also study resonant tunneling through a double-barrier structure and related effects associated with the Coulomb blockade. Resonant peaks in the transmission are possible, provided the interactions are not too strongly repulsive. However, in contrast to resonant tunneling in a noninteracting electron gas, we find that in the presence of interactions the width of the resonance vanishes, as a power of temperature, in the zero-temperature limit. Moreover, the resonance line shapes are shown to be described by a universal scaling function, which has power law, but non-Lorentzian tails. For a particular choice of interaction strengths, we present an exact solution of our model, which verifies the scaling assumptions and provides an explicit expression for the scaling function. We also consider the role played by the electron-spin degree of freedom in modifying the trasnsmission through barriers. With spin, there are four possible phases corresponding to perfect transmission or perfect reflection of charge and spin. We present phase diagrams for these different behaviors and analyze the nontrivial transitions between them. At these transitions we find that the conductance or transmission is universal---depending only on the dimensionless conductance of the leads and not on the details of the barriers. In the case of resonant tunneling with spin, we discuss the ``Kondo'' resonance, which occurs when there is a spin degeneracy for electrons between the two barriers. Many of the predictions should be directly testable in gated GaAs wires.

Evolution of long-range fractal correlations and 1/f noise in DNA base sequences.

Abstract: A new method of quantifying correlations in symbolic sequences is applied to DNA nucleotides. Spectral density measurements of individual base positions demonstrate the ubiquity of low-frequency 1/${\mathit{f}}^{\mathrm{\ensuremath{\beta}}}$ noise and long-range fractal correlations as well as prominent short-range periodicities. Ensemble averages over classifications in the GenBank databank (primate, invertebrate, plant, etc.) show systematic changes in spectral exponent \ensuremath{\beta} with evolutionary category.

Orthogonal defect classification-a concept for in-process measurements

Abstract: Orthogonal defect classification (ODC), a concept that enables in-process feedback to software developers by extracting signatures on the development process from defects, is described. The ideas are evolved from an earlier finding that demonstrates the use of semantic information from defects to extract cause-effect relationships in the development process. This finding is leveraged to develop a systematic framework for building measurement and analysis methods. The authors define ODC and discuss the necessary and sufficient conditions required to provide feedback to a developer; illustrate the use of the defect type distribution to measure the progress of a product through a process; illustrate the use of the defect trigger distribution to evaluate the effectiveness and eventually the completeness of verification processes such as inspection or testing; provides sample results from pilot projects using ODC; and open the doors to a wide variety of analysis techniques for providing effective and fast feedback based on the concepts of ODC. >

Systematic study of insulator-metal transitions in perovskites RNiO3 (R=Pr,Nd,Sm,Eu) due to closing of charge-transfer gap.

Abstract: The detailed behavior of the phase transitions was mapped out for the series R${\mathrm{NiO}}_{3}$ as a function of the rare earth (R). A sharp insulator-metal transition is observed, which depends strongly on R.Forsmall$R it occurs at a higher temperature than the antiferromagnetic ordering (measured by muon-spin relaxation). By increasing either the temperature or the size of R, an insulator-metal transition is observed, most probably caused by the closing of the charge-transfer gap, induced by increase in the electronic bandwidth.

Practical Issues in Temporal Difference Learning

Abstract: This paper examines whether temporal difference methods for training connectionist networks, such as Sutton's TD(λ) algorithm, can be successfully applied to complex real-world problems. A number of important practical issues are identified and discussed from a general theoretical perspective. These practical issues are then examined in the context of a case study in which TD(λ) is applied to learning the game of backgammon from the outcome of self-play. This is apparently the first application of this algorithm to a complex non-trivial task. It is found that, with zero knowledge built in, the network is able to learn from scratch to play the entire game at a fairly strong intermediate level of performance, which is clearly better than conventional commercial programs, and which in fact surpasses comparable networks trained on a massive human expert data set. This indicates that TD learning may work better in practice than one would expect based on current theory, and it suggests that further analysis of TD methods, as well as applications in other complex domains, may be worth investigating.

Transport in a one-channel Luttinger liquid.

Abstract: We study theoretically the transport of a one-channel Luttinger liquid through a weak link. For repulsive electron interactions, the electrons are completely reflected by even the smallest scatterer, leading to a truly insulating weak link, in striking contrast to that for noninteracting electrons. At finite temperature (T) the conductance is nonzero, and is predicted to vanish as a power of T. At T=0 power-law current-voltage characteristics are predicted. For attractive interactions, a Luttinger liquid is argued to be perfectly transmitted through even the largest of barriers. The role of Fermi-liquid leads is also explored.

Directed-Graph Epidemiological Models of Computer viruses.

Abstract: The strong analogy between biological viruses and their computational counterparts has motivated the authors to adapt the techniques of mathematical epidemiology to the study of computer virus propagation In order to allow for the most general patterns of program sharing, a standard epidemiological model is extended by placing it on a directed graph and a combination of analysis and simulation is used to study its behavior The conditions under which epidemics are likely to occur are determined, and, in cases where they do, the dynamics of the expected number of infected individuals are examined as a function of time It is concluded that an imperfect defense against computer viruses can still be highly effective in preventing their widespread proliferation, provided that the infection rate does not exceed a well-defined critical epidemic threshold >

On Defining Proofs of Knowledge

Abstract: The notion of a "proof of knowledge," (suggested by Goldwasser, Micali and Rackoff, has been used in many works as a tool for the construction of cryptographic protocols and other schemes. Yet the commonly cited formalizations of this notion are unsatisfactory and in particular inadequate for some of the applications in which they are used. Consequently, new researchers keep getting misled by existing literature. The purpose of this paper is to indicate the source of these problems and suggest a definition which resolves them.

The CLP( ℛ ) language and system

Abstract: The CLP( ℛ ) programming language is defined, its underlying philosophy and programming methodology are discussed, important implementation issues are explored in detail, and finally, a prototype interpreter is described.CLP( ℛ ) is designed to be an instance of the Constraint Logic Programming Scheme, a family of rule-based constraint programming languages defined by Jaffar and Lassez. The domain of computation ℛ of this particular instance is the algebraic structure consisting of uninterpreted functors over real numbers. An important property of CLP( ℛ )is that the constraints are treated uniformly in the sense that they are used to specify the input parameters to a program, they are the only primitives used in the execution of a program, and they are used to describe the output of a program.Implementation of a CLP language, and of CLP( ℛ ) in particular, raises new problems in the design of a constraint-solver. For example, the constraint solver must be incremental in the sense that solving additional constraints must not entail the resolving of old constraints. In our system, constraints are filtered through an inference engine, an engine/solver interface, an equation solver and an inequality solver. This sequence of modules reflects a classification and prioritization of the classes of constraints. Modules solving higher priority constraints are isolated from the complexities of modules solving lower priority constraints. This multiple-phase solving of constraints, together with a set of associated algorithms, gives rise to a practical system.

Review of inductively coupled plasmas for plasma processing

Abstract: The need for large-area, high-density plasma sources for plasma-aided manufacturing of integrated circuits has created a renewed interest in inductively coupled plasmas (ICPs). Several ICP reactor geometries are briefly reviewed. Typically, inductive coupling of RF power (0.5-28 MHz) can produce ion densities in excess of 1012 cm-3 even at submillitorr pressures. Existing electromagnetic field models of ICPs are examined and found to be in reasonable agreement with experimental results. Sputter deposition, anodic silicon oxidation and polymer etching using ICPs are also described. It is concluded that ICPs are promising candidates for meeting the future requirements of plasma processing, although considerable process development, plasma characterization and modelling are still needed.

Scattering theory of current and intensity noise correlations in conductors and wave guides.

Abstract: The low-frequency current-fluctuation spectra of phase-coherent electron conductors are related to the scattering matrix of the conductor. Each contact of the conductor is connected to a thermal equilibrium electron reservoir. The current-current correlations of the conductor are compared with the intensity-intensity correlations of a photon wave guide with all its ports connected to blackbody radiation sources. Only two sources of noise are considered: (a) Fluctuations in the occupation numbers of the incident channels that reflect the thermal equilibrium fluctuations of the reservoir states and (b) a shot noise (or partition noise) that originates if a carrier can be scattered into more than one final state and is present even at zero temperature. The theory uses single-particle scattering states to build up multiparticle states with the proper symmetry. Second quantization provides an elegant treatment of this problem if annihilation and creation operators for both the input and output channels of the wave guide are introduced. At equilibrium, in the absence of transport, the correlations of flux fluctuations measured at two different contacts are negative for both fermions and bosons. Away from equilibrium, in the presence of a net flux, the fluctuations are related to transport coefficients which invoke products of four scattering matrices.The transport portion of the correlation of the flux fluctuations at two different contacts is negative for fermions but is positive for bosons. The transport portion (shot noise) is very sensitive to the transmission behavior of the wave guide. Both for fermions and for bosons completely open transmission channels give no contribution. In addition to two-terminal conductors, we consider four-probe conductors in high magnetic fields which have the property that carriers transmitted and reflected at a barrier reach separate contacts. We discuss a four-terminal experiment which explicitly shows that the correlation function in the presence of two particle sources is not an incoherent sum of correlations generated by particles originating in one of the sources but contains exchange terms due to the indistinguishability of identical particles. We discuss the conditions for such exchange terms to be sensitive to a quantum-mechanical phase and the possibility to tune this phase with the help of an Aharonov-Bohm flux.

Transport of dust particles in glow-discharge plasmas.

Abstract: A theory is presented for the transport of dust particles in glow-discharge plasmas. The forces which act on the negatively charged dust particles are examined and estimated. The dominant force is shown to be dependent upon the particle size and location within the discharge.

Method and apparatus for message handling in computer systems

Abstract: An Integrated Messaging System which integrates mail from a plurality of mail servers handling messages of different media types such as text, voice, facsimile, video and image. The IMS maintains the in-basket for all mail systems, eliminating the need to collect each type of mail separately. Any terminal interface, telephone or computer workstation can be used to collect, generate and act upon a message of any media type. Further, from the preferred system, the user can request another file server and its associated terminals to perform messaging services. The system includes a variety traditional E-mail and voice mail functions which can be used for any message. The IMS also includes synchronization means which checks to see whether the mail count in each in-basket is the same to guarantee that the same mail items are in each file server in-basket. An integrated messaging protocol is used to pass information between the file servers. It is designed in a generic manner to allow wide variety of foreign message formats at each of the respected media file server. For the majority of transactions, the protocol is independent of message body format, referencing only the message pointer or header.

Simple Constructions of Almost k-wise Independent Random Variables

Abstract: We present three alternative simple constructions of small probability spaces on n bits for which any k bits are almost independent. The number of bits used to specify a point in the sample space is (2 + o(1)) (log log n + k/2 + log k + log 1/ϵ), where ϵ is the statistical difference between the distribution induced on any k bit locations and the uniform distribution. This is asymptotically comparable to the construction recently presented by Naor and Naor (our size bound is better as long as ϵ < 1/(k log n)). An additional advantage of our constructions is their simplicity.

Method and system for multimedia access control enablement

Abstract: A method and system are disclosed for securely distributing a plurality of software files from a software distribution processor to a user processor, while selectively enabling the user processor to only use a subset of a lesser plurality of the software files. This is achieved by employing a customer key which includes a clear customer number and a derived portion derived from the customer number. The customer key is transformed into a second customer key which serves as a key expression for encrypting a file encryption key specifically intended for a respective one of the plurality of files. A plurality of software files can be stored together, for example on a CD-ROM, with each file encrypted under a corresponding file encryption key. The CD-ROM can be distributed to many user processors. When a specific user processor needs to run one of the software files, a request will be transmitted from the user processor to the software distribution processor. In response to that request, an encrypted file encryption key specific for the requested file, will be transmitted to the user processor. This will enable the user processor to decrypt only the requested file from the CD-ROM. All other files on the CD-ROM remain in their encrypted form and cannot be decrypted and used by the file encryption key received from the software distribution processor.

Photon antibunching in the fluorescence of a single dye molecule trapped in a solid

Abstract: The correlation between fluorescence photons emitted by an optically pumped single molecule of pentacene in a p-terphenyl host has been investigated at short times. The correlation function shows photon antibunching, a unique feature of a nonclassical radiation field, which decreases if two molecules rather than one are pumped at the same time. The peculiarities of the correlation function for a three-level molecule are discussed and the theoretical description outlined.