Showing papers on "Quantum computer published in 1992"

Rapid Solution of Problems by Quantum Computation

Abstract: A class of problems is described which can be solved more efficiently by quantum computation than by any classical or stochastic method. The quantum computation solves the problem with certainty in exponentially less time than any classical deterministic computation.

The quantum challenge to structural complexity theory

Abstract: A nontechnical survey of recent quantum-mechanical discoveries that challenge generally accepted complexity-theoretic versions of the Church-Turing thesis is presented. In particular, the authors construct an oracle relative to which there exists a set that can be recognized in quantum polynomal time (QP), yet any Turing machine that recognizes it would require exponential time even if allowed to be probabilistic, provided that errors are not tolerated. In particular, QP is not contained in or equal to ZPP relative to this oracle. Furthermore, there are cryptographic tasks that are demonstrably impossible to implement with unlimited computing power probabilistic interactive turning machines, yet they can be implemented even in practice by quantum mechanical apparatus. >

Oracle Quantum Computing

Abstract: Building on the work of Deutsch and Jozsa, we construct oracles relative to which (1) there is a decision problem that can be solved with certainty in worst-case polynomial time on the quantum computer, yet it cannot be solved classically in probabilistic expected polynomial time if errors are not tolerated, nor even in nondeterministic polynomial time, and (2) there is a decision problem that can be solved in exponential time on the quantum computer, which requires double exponential time on all but finitely many instances on any classical deterministic computer.

Linear Logic For Generalized Quantum Mechanics

Abstract: Quantum logic is static, describing automata having uncertain states but no state transitions and no Heisenberg uncertainty tradeoff. We cast Girard’s linear logic in the role of a dynamic quantum logic, regarded as an extension of quantum logic with time nonstandardly interpreted over a domain of linear automata and their dual linear schedules. In this extension the uncertainty tradeoff emerges via the “structure veil.” When VLSI shrinks to where quantum effects are felt, their computer-aided design systems may benefit from such logics of computational behavior having a strong connection to quantum mechanics.

Topology lattice as quantum logic

Abstract: We discuss the relations between the lattice of topologies for the simplest case of a three-point set and quantum logic. A hypothetical “topologymeter” is considered as a measuring apparatus, and it is shown that it necessarily possesses some quantum features, such as complementarity.

Steady, simultaneous quantum computation: a paradigm for the investigation of nondeterministic and non-recursive computation

Abstract: We introduce the notion of a class of abstract digital computers based on quantum reversibility and indeterminism (not 011 the classical sequential architecture), which are compatible with quantum laws and may perform nondeterministic and non-recursive computation.

Cryptographic Primitives And Quantum Theory

Abstract: only using public key cryptography, but using quantum mechanics as a support. This paper summarizes the current knowledge in the field of two-party cryptographic protocols devised f rom quantum systems. W e introduce the reader to the notion of cryptographic protocols and describe a number of sample building blocks to achieve them. W e also give pointers for the reader who i s interested to the quantum implementation of these building blocks. 2 Cryptographic Primitives We now introduce the main two basic primitives that have been widely considered as useful building blocks in the design of more elaborate cryptographic protocols:

Computation and Quantum Superposition

Abstract: We review recent work and some new results on the role of quantum superpositions in providing new modes of computation, not available to classical computers. For certain problems, these new modes can provide an exponential reduction in complexity over any classical computer demonstrating the importance of quantum processes for issues in complexity theory.

Reflected power effects in computer simulations using the quantum theory of mixing

Abstract: Attention is directed to the signal reflection gain and the signal-to-image conversion gain in the quantum theory of mixing. The theory gives two distinct types of solutions for the minimum noise temperature of an SIS (superconductor-insulator-superconductor) receiver. One has very high IF (intermediate frequency) conversion gain, and the returned signal and image powers are extremely high as well. The other has moderate IF conversion gain, but the returned powers tend to be very small. >

Computation And Quantum Superposition

Abstract: We review recent work and some new results on the role of quantum superpositions in providing new modes of computation, not available to classical computers. For certain problems, these new modes can provide an exponential reduction in complexity over any classical computer demonstrating the importance of quantum processes for issues in complexity theory.

On Convolution

Abstract: Convolution describes a variety of physical system dynamics, both quantum and classical. Convolution, in a discrete form, describes the nondeterministic d y namics of computational systems as well. Petri nets are used as the motivating model for the discrete convolution. The similarities are formal, but the description of manuals for physical experiments by Foulis and Randall also receives ezpression in terms of Petri nets b y this correspondence. The observations of Petri nets are contrasted with the observations of quantum systems. This brief, only descriptive, paper just mentions that there are relationships t o linear logic.

Can Quantum Computation Provide a Physically Realistic Model of the Self and Its Brain

Abstract: Support is provided from the theory of Lie computability and machines for Sir John Eccles hypothesis based on extensive neurophysiological evidence, that, “Mental events (may) cause neural events analogously to the probability fields of quantum mechanics” (1).

Quantum Mechanical Neural Networks: An Isoperimetric Extremization

Abstract: This paper introduces the i&a of a new and novel approach to Neural Netnrorkrs. Considering the HopfreEd Model us a protoqp, the apparatus of Quantum Mechanics is used to quantize the resultant weight fE1d A conjecture ih made ah~d tke correspondence between Hopfield attractom and eigenvalues. Directions for continued work axe givem

On the physical properties of a curved mesoscopic system

Abstract: Mesoscopic systems have been studied since some decades. These structures with dimensions of the order of nanometers present some typical properties of classic systems as well as other belonging to quantum systems. Examples of mesoscopic systems are quantum dots, antidots, quantum wires and rings. Understanding and characterization of these systems are very important to difierent branches like Basic Science (for example, Physics, Chemistry and Biology) and technological development. Lasers, photodetectors, quantum computation, solar cells and studies about biological systems: these are some examples of the several and distinct applications of the research about mesoscopic systems. Several growth techniques of mesoscopic systems are known and one of the most used is Molecular Beam Epitaxy (MBE). In the MBE process the deposited layer lies on a lattice structure and its orientation is identical to those of the substrate, also following a growth axis perpendicular to this substrate. But MBE is not perfect and one cannot have plain surfaces, because impurities often are present and rough surfaces take place. This way we found motivation for investigating the role played by curvature in the physical properties of mesoscopic systems. In this work we study a mesoscopic system grown over a surface with positive curvature, with the help of concepts related to Geometric Theory of Defects. Some important aspects of that geometrical approach can be found in the reference right below. We obtain the energy eigenvalues and the eigenfunctions for that system, both without magnetic fleld and with it.

Quantum Neurodynamics Or "where Is The State Vector"

Abstract: This paper deals more with the computation of physics than with the physics of computation. That, in itself, does not make these ideas unique among those presented at this Workshop: Fredkin's dinner discourse on the universe as a computer is in the same category, for example. However, the focus of this paper is the description of a computational architecture that is capable of autonomous modeling at least part of the universe, observing and comprehending it, predicting its behavior, and -through motors and transducers -altering its evolution. To achieve this capability, the architecture computes physics in the abstract, and uses methods from neurocomputing to build associative maps between its internal abstract dynamics and the observed world. It then uses these maps to transform observations of its environment into predictions about its behavior. The algorithms that we discuss below are not mere abstractions. They have been implemented in both serial and parallel form and they have been demonstrated to work on simple tasks comparable to those performed by the human visual system in tracking multiple moving objects in the visual field simultaneously. They have been developed over the past five years with almost $2 M in funding from Army, Navy, Air Force, DARPA, NSF and NASA sponsors, whose support we gratefully acknowledge.