Science.gov

Sample records for quantum computing technology

  1. TOPICAL REVIEW: Information, computing technology, and quantum computing

    NASA Astrophysics Data System (ADS)

    Keyes, Robert W.

    2006-05-01

    Information has long been described by physical structures. The spectacularly successful modern computers use silicon transistors to hold and process information. A number of attempts to repeat the success with other kinds of solid-state devices have failed. The reasons for the unique success of silicon transistors are found in the requirements of computing, the properties of transistors, and the variability in devices manufactured in the large quantities needed to build large computing systems. New challenges will be met in building quantum computers to meet the same requirements.

  2. Quantum computers.

    PubMed

    Ladd, T D; Jelezko, F; Laflamme, R; Nakamura, Y; Monroe, C; O'Brien, J L

    2010-03-01

    Over the past several decades, quantum information science has emerged to seek answers to the question: can we gain some advantage by storing, transmitting and processing information encoded in systems that exhibit unique quantum properties? Today it is understood that the answer is yes, and many research groups around the world are working towards the highly ambitious technological goal of building a quantum computer, which would dramatically improve computational power for particular tasks. A number of physical systems, spanning much of modern physics, are being developed for quantum computation. However, it remains unclear which technology, if any, will ultimately prove successful. Here we describe the latest developments for each of the leading approaches and explain the major challenges for the future. PMID:20203602

  3. Quantum computing

    PubMed Central

    Li, Shu-Shen; Long, Gui-Lu; Bai, Feng-Shan; Feng, Song-Lin; Zheng, Hou-Zhi

    2001-01-01

    Quantum computing is a quickly growing research field. This article introduces the basic concepts of quantum computing, recent developments in quantum searching, and decoherence in a possible quantum dot realization. PMID:11562459

  4. Quantum computing with trapped ions

    SciTech Connect

    Hughes, R.J.

    1998-01-01

    The significance of quantum computation for cryptography is discussed. Following a brief survey of the requirements for quantum computational hardware, an overview of the ion trap quantum computation project at Los Alamos is presented. The physical limitations to quantum computation with trapped ions are analyzed and an assessment of the computational potential of the technology is made.

  5. Quantum entanglement, quantum communication and the limits of quantum computing

    NASA Astrophysics Data System (ADS)

    Ambainis, Andris

    Quantum entanglement is a term describing the quantum correlations between different parts of a quantum system. Quantum information theory has developed sophisticated techniques to quantify and study quantum entanglement. In this thesis, we show how to apply those techniques to problems in quantum algorithms, complexity theory, communication and cryptography. The main results are: (1) quantum communication protocols that are exponentially more efficient that conventional (classical) communication protocols, (2) unconditionally secure quantum protocols for cryptographic problems, (3) a new "quantum adversary" method for proving lower bounds on quantum algorithms, (4) a study of "one clean qubit computation", a model related to the experimental implementation of quantum computers using NMR (nucleo-magnetic resonance) technology.

  6. Quantum computation for quantum chemistry

    NASA Astrophysics Data System (ADS)

    Aspuru-Guzik, Alan

    2010-03-01

    Numerically exact simulation of quantum systems on classical computers is in general, an intractable computational problem. Computational chemists have made progress in the development of approximate methods to tackle complex chemical problems. The downside of these approximate methods is that their failure for certain important cases such as long-range charge transfer states in the case of traditional density functional theory. In 1982, Richard Feynman suggested that a quantum device should be able to simulate quantum systems (in our case, molecules) exactly using quantum computers in a tractable fashion. Our group has been working in the development of quantum chemistry algorithms for quantum devices. In this talk, I will describe how quantum computers can be employed to carry out numerically exact quantum chemistry and chemical reaction dynamics calculations, as well as molecular properties. Finally, I will describe our recent experimental quantum computation of the energy of the hydrogen molecule using an optical quantum computer.

  7. Quantum walk computation

    SciTech Connect

    Kendon, Viv

    2014-12-04

    Quantum versions of random walks have diverse applications that are motivating experimental implementations as well as theoretical studies. Recent results showing quantum walks are “universal for quantum computation” relate to algorithms, to be run on quantum computers. We consider whether an experimental implementation of a quantum walk could provide useful computation before we have a universal quantum computer.

  8. Quantum Computing's Classical Problem, Classical Computing's Quantum Problem

    NASA Astrophysics Data System (ADS)

    Van Meter, Rodney

    2014-08-01

    Tasked with the challenge to build better and better computers, quantum computing and classical computing face the same conundrum: the success of classical computing systems. Small quantum computing systems have been demonstrated, and intermediate-scale systems are on the horizon, capable of calculating numeric results or simulating physical systems far beyond what humans can do by hand. However, to be commercially viable, they must surpass what our wildly successful, highly advanced classical computers can already do. At the same time, those classical computers continue to advance, but those advances are now constrained by thermodynamics, and will soon be limited by the discrete nature of atomic matter and ultimately quantum effects. Technological advances benefit both quantum and classical machinery, altering the competitive landscape. Can we build quantum computing systems that out-compute classical systems capable of some logic gates per month? This article will discuss the interplay in these competing and cooperating technological trends.

  9. Quantum Computer Games: Quantum Minesweeper

    ERIC Educational Resources Information Center

    Gordon, Michal; Gordon, Goren

    2010-01-01

    The computer game of quantum minesweeper is introduced as a quantum extension of the well-known classical minesweeper. Its main objective is to teach the unique concepts of quantum mechanics in a fun way. Quantum minesweeper demonstrates the effects of superposition, entanglement and their non-local characteristics. While in the classical

  10. Quantum Computer Games: Quantum Minesweeper

    ERIC Educational Resources Information Center

    Gordon, Michal; Gordon, Goren

    2010-01-01

    The computer game of quantum minesweeper is introduced as a quantum extension of the well-known classical minesweeper. Its main objective is to teach the unique concepts of quantum mechanics in a fun way. Quantum minesweeper demonstrates the effects of superposition, entanglement and their non-local characteristics. While in the classical…

  11. Cryptography, quantum computation and trapped ions

    SciTech Connect

    Hughes, Richard J.

    1998-03-01

    The significance of quantum computation for cryptography is discussed. Following a brief survey of the requirements for quantum computational hardware, an overview of the ion trap quantum computation project at Los Alamos is presented. The physical limitations to quantum computation with trapped ions are analyzed and an assessment of the computational potential of the technology is made.

  12. Quantum robots and quantum computers

    SciTech Connect

    Benioff, P.

    1998-07-01

    Validation of a presumably universal theory, such as quantum mechanics, requires a quantum mechanical description of systems that carry out theoretical calculations and systems that carry out experiments. The description of quantum computers is under active development. No description of systems to carry out experiments has been given. A small step in this direction is taken here by giving a description of quantum robots as mobile systems with on board quantum computers that interact with different environments. Some properties of these systems are discussed. A specific model based on the literature descriptions of quantum Turing machines is presented.

  13. Adiabatic Quantum Computing

    NASA Astrophysics Data System (ADS)

    Landahl, Andrew

    2012-10-01

    Quantum computers promise to exploit counterintuitive quantum physics principles like superposition, entanglement, and uncertainty to solve problems using fundamentally fewer steps than any conventional computer ever could. The mere possibility of such a device has sharpened our understanding of quantum coherent information, just as lasers did for our understanding of coherent light. The chief obstacle to developing quantum computer technology is decoherence--one of the fastest phenomena in all of physics. In principle, decoherence can be overcome by using clever entangled redundancies in a process called fault-tolerant quantum error correction. However, the quality and scale of technology required to realize this solution appears distant. An exciting alternative is a proposal called ``adiabatic'' quantum computing (AQC), in which adiabatic quantum physics keeps the computer in its lowest-energy configuration throughout its operation, rendering it immune to many decoherence sources. The Adiabatic Quantum Architectures In Ultracold Systems (AQUARIUS) Grand Challenge Project at Sandia seeks to demonstrate this robustness in the laboratory and point a path forward for future hardware development. We are building devices in AQUARIUS that realize the AQC architecture on up to three quantum bits (``qubits'') in two platforms: Cs atoms laser-cooled to below 5 microkelvin and Si quantum dots cryo-cooled to below 100 millikelvin. We are also expanding theoretical frontiers by developing methods for scalable universal AQC in these platforms. We have successfully demonstrated operational qubits in both platforms and have even run modest one-qubit calculations using our Cs device. In the course of reaching our primary proof-of-principle demonstrations, we have developed multiple spinoff technologies including nanofabricated diffractive optical elements that define optical-tweezer trap arrays and atomic-scale Si lithography commensurate with placing individual donor atoms with scanning-tunneling microscopy. I will review our experimental and theoretical progress in this plenary talk.[4pt] This work was supported by the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  14. Quantum Computation and Information

    NASA Astrophysics Data System (ADS)

    Carlini, A.

    2002-12-01

    We report on lectures about some of the main topics in the field of quantum computation and information theory, including a discussion of Shor's algorithm for factoring integers, the protocol of quantum teleportation, the role of decoherence and quantum error correction in quantum computation, the information processing of ion trap devices in noisy environments, new quantum algorithmics with quantum field theory, the meaning of information storage in the decoherence process and, finally, the role of quantum information in black hole physics.

  15. Introduction to Quantum Computation

    NASA Astrophysics Data System (ADS)

    Ekert, A.

    A computation is a physical process. It may be performed by a piece of electronics or on an abacus, or in your brain, but it is a process that takes place in nature and as such it is subject to the laws of physics. Quantum computers are machines that rely on characteristically quantum phenomena, such as quantum interference and quantum entanglement in order to perform computation. In this series of lectures I want to elaborate on the computational power of such machines.

  16. Quantum analogue computing.

    PubMed

    Kendon, Vivien M; Nemoto, Kae; Munro, William J

    2010-08-13

    We briefly review what a quantum computer is, what it promises to do for us and why it is so hard to build one. Among the first applications anticipated to bear fruit is the quantum simulation of quantum systems. While most quantum computation is an extension of classical digital computation, quantum simulation differs fundamentally in how the data are encoded in the quantum computer. To perform a quantum simulation, the Hilbert space of the system to be simulated is mapped directly onto the Hilbert space of the (logical) qubits in the quantum computer. This type of direct correspondence is how data are encoded in a classical analogue computer. There is no binary encoding, and increasing precision becomes exponentially costly: an extra bit of precision doubles the size of the computer. This has important consequences for both the precision and error-correction requirements of quantum simulation, and significant open questions remain about its practicality. It also means that the quantum version of analogue computers, continuous-variable quantum computers, becomes an equally efficient architecture for quantum simulation. Lessons from past use of classical analogue computers can help us to build better quantum simulators in future. PMID:20603371

  17. Photonic quantum technologies

    NASA Astrophysics Data System (ADS)

    O'Brien, Jeremy

    2013-03-01

    Of the approaches to quantum computing, photons are appealing for their low-noise properties and ease of manipulation, and relevance to other quantum technologies, including communication, metrology and measurement. We report an integrated waveguide approach to photonic quantum circuits for high performance, miniaturization and scalability [6-10]. We address the challenges of scaling up quantum circuits using new insights into how controlled operations can be efficiently realised, demonstrating Shor's algorithm with consecutive CNOT gates and the iterative phase estimation algorithm. We have shown how quantum circuits can be reconfigured, using thermo-optic phase shifters to realise a highly reconfigurable quantum circuit, and electro-optic phase shifters in lithium niobate to rapidly manipulate the path and polarisation of telecomm wavelength single photons. We have addressed miniaturisation using multimode interference architectures to directly implement NxN Hadamard operations, and by using high refractive index contrast materials such as SiOxNy, in which we have implemented quantum walks of correlated photons, and Si, in which we have demonstrated generation of orbital angular momentum states of light. We have incorporated microfluidic channels for the delivery of samples to measure the concentration of a blood protein with entangled states of light. We have begun to address the integration of superconducting single photon detectors and diamond and non-linear single photon sources. Finally, we give an overview of recent work on fundamental aspects of quantum measurement, including a quantum version of Wheeler's delayed choice experiment.

  18. Scalable optical quantum computer

    SciTech Connect

    Manykin, E A; Mel'nichenko, E V

    2014-12-31

    A way of designing a scalable optical quantum computer based on the photon echo effect is proposed. Individual rare earth ions Pr{sup 3+}, regularly located in the lattice of the orthosilicate (Y{sub 2}SiO{sub 5}) crystal, are suggested to be used as optical qubits. Operations with qubits are performed using coherent and incoherent laser pulses. The operation protocol includes both the method of measurement-based quantum computations and the technique of optical computations. Modern hybrid photon echo protocols, which provide a sufficient quantum efficiency when reading recorded states, are considered as most promising for quantum computations and communications. (quantum computer)

  19. Quantum computation as geometry.

    PubMed

    Nielsen, Michael A; Dowling, Mark R; Gu, Mile; Doherty, Andrew C

    2006-02-24

    Quantum computers hold great promise for solving interesting computational problems, but it remains a challenge to find efficient quantum circuits that can perform these complicated tasks. Here we show that finding optimal quantum circuits is essentially equivalent to finding the shortest path between two points in a certain curved geometry. By recasting the problem of finding quantum circuits as a geometric problem, we open up the possibility of using the mathematical techniques of Riemannian geometry to suggest new quantum algorithms or to prove limitations on the power of quantum computers. PMID:16497928

  20. Quantum computer games: quantum minesweeper

    NASA Astrophysics Data System (ADS)

    Gordon, Michal; Gordon, Goren

    2010-07-01

    The computer game of quantum minesweeper is introduced as a quantum extension of the well-known classical minesweeper. Its main objective is to teach the unique concepts of quantum mechanics in a fun way. Quantum minesweeper demonstrates the effects of superposition, entanglement and their non-local characteristics. While in the classical minesweeper the goal of the game is to discover all the mines laid out on a board without triggering them, in the quantum version there are several classical boards in superposition. The goal is to know the exact quantum state, i.e. the precise layout of all the mines in all the superposed classical boards. The player can perform three types of measurement: a classical measurement that probabilistically collapses the superposition; a quantum interaction-free measurement that can detect a mine without triggering it; and an entanglement measurement that provides non-local information. The application of the concepts taught by quantum minesweeper to one-way quantum computing are also presented.

  1. Quantum information and computation

    SciTech Connect

    Bennett, C.H.

    1995-10-01

    A new quantum theory of communication and computation is emerging, in which the stuff transmitted or processed is not classical information, but arbitrary superpositions of quantum states. {copyright} 1995 {ital American} {ital Institute} {ital of} {ital Physics}.

  2. Quantum Computing since Democritus

    NASA Astrophysics Data System (ADS)

    Aaronson, Scott

    2013-03-01

    1. Atoms and the void; 2. Sets; 3. Gdel, Turing, and friends; 4. Minds and machines; 5. Paleocomplexity; 6. P, NP, and friends; 7. Randomness; 8. Crypto; 9. Quantum; 10. Quantum computing; 11. Penrose; 12. Decoherence and hidden variables; 13. Proofs; 14. How big are quantum states?; 15. Skepticism of quantum computing; 16. Learning; 17. Interactive proofs and more; 18. Fun with the Anthropic Principle; 19. Free will; 20. Time travel; 21. Cosmology and complexity; 22. Ask me anything.

  3. Towards a Quantum Computer?

    NASA Astrophysics Data System (ADS)

    Bellac, Michel Le

    2014-11-01

    In everyday life, practically all the information which is processed, exchanged or stored is coded in the form of discrete entities called bits, which take two values only, by convention 0 and 1. With the present technology for computers and optical fibers, bits are carried by electrical currents and electromagnetic waves corresponding to macroscopic fluxes of electrons and photons, and they are stored in memories of various kinds, for example, magnetic memories. Although quantum physics is the basic physics which underlies the operation of a transistor (Chapter 6) or of a laser (Chapter 4), each exchanged or processed bit corresponds to a large number of elementary quantum systems, and its behavior can be described classically due to the strong interaction with the environment (Chapter 9). For about thirty years, physicists have learned to manipulate with great accuracy individual quantum systems: photons, electrons, neutrons, atoms, and so forth, which opens the way to using two-state quantum systems, such as the polarization states of a photon (Chapter 2) or the two energy levels of an atom or an ion (Chapter 4) in order to process, exchange or store information. In 2.3.2, we used the two polarization states of a photon, vertical (V) and horizontal (H), to represent the values 0 and 1 of a bit and to exchange information. In what follows, it will be convenient to use Dirac's notation (see Appendix A.2.2 for more details), where a vertical polarization state is denoted by |V> or |0> and a horizontal one by |H> or |1>, while a state with arbitrary polarization will be denoted by |?>. The polarization states of a photon give one possible realization of a quantum bit, or for short a qubit. Thanks to the properties of quantum physics, quantum computers using qubits, if they ever exist, would outperform classical computers for some specific, but very important, problems. In Sections 8.1 and 8.2, we describe some typical quantum algorithms and, in order to do so, we shall not be able to avoid some technical developments. However, these two sections may be skipped in a first reading, as they are not necessary for understanding the more general considerations of Sections 8.3 and 8.4.

  4. ASCR Workshop on Quantum Computing for Science

    SciTech Connect

    Aspuru-Guzik, Alan; Van Dam, Wim; Farhi, Edward; Gaitan, Frank; Humble, Travis; Jordan, Stephen; Landahl, Andrew J; Love, Peter; Lucas, Robert; Preskill, John; Muller, Richard P.; Svore, Krysta; Wiebe, Nathan; Williams, Carl

    2015-06-01

    This report details the findings of the DOE ASCR Workshop on Quantum Computing for Science that was organized to assess the viability of quantum computing technologies to meet the computational requirements of the DOE’s science and energy mission, and to identify the potential impact of quantum technologies. The workshop was held on February 17-18, 2015, in Bethesda, MD, to solicit input from members of the quantum computing community. The workshop considered models of quantum computation and programming environments, physical science applications relevant to DOE's science mission as well as quantum simulation, and applied mathematics topics including potential quantum algorithms for linear algebra, graph theory, and machine learning. This report summarizes these perspectives into an outlook on the opportunities for quantum computing to impact problems relevant to the DOE’s mission as well as the additional research required to bring quantum computing to the point where it can have such impact.

  5. Photonic quantum technologies (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    O'Brien, Jeremy L.

    2015-09-01

    The impact of quantum technology will be profound and far-reaching: secure communication networks for consumers, corporations and government; precision sensors for biomedical technology and environmental monitoring; quantum simulators for the design of new materials, pharmaceuticals and clean energy devices; and ultra-powerful quantum computers for addressing otherwise impossibly large datasets for machine learning and artificial intelligence applications. However, engineering quantum systems and controlling them is an immense technological challenge: they are inherently fragile; and information extracted from a quantum system necessarily disturbs the system itself. Of the various approaches to quantum technologies, photons are particularly appealing for their low-noise properties and ease of manipulation at the single qubit level. We have developed an integrated waveguide approach to photonic quantum circuits for high performance, miniaturization and scalability. We will described our latest progress in generating, manipulating and interacting single photons in waveguide circuits on silicon chips.

  6. Scalable optical quantum computer

    NASA Astrophysics Data System (ADS)

    Manykin, E. A.; Mel'nichenko, E. V.

    2014-12-01

    A way of designing a scalable optical quantum computer based on the photon echo effect is proposed. Individual rare earth ions Pr3+, regularly located in the lattice of the orthosilicate (Y2SiO5) crystal, are suggested to be used as optical qubits. Operations with qubits are performed using coherent and incoherent laser pulses. The operation protocol includes both the method of measurement-based quantum computations and the technique of optical computations. Modern hybrid photon echo protocols, which provide a sufficient quantum efficiency when reading recorded states, are considered as most promising for quantum computations and communications.

  7. Dissipative quantum computing with open quantum walks

    SciTech Connect

    Sinayskiy, Ilya; Petruccione, Francesco

    2014-12-04

    An open quantum walk approach to the implementation of a dissipative quantum computing scheme is presented. The formalism is demonstrated for the example of an open quantum walk implementation of a 3 qubit quantum circuit consisting of 10 gates.

  8. Quantum Analog Computing

    NASA Technical Reports Server (NTRS)

    Zak, M.

    1998-01-01

    Quantum analog computing is based upon similarity between mathematical formalism of quantum mechanics and phenomena to be computed. It exploits a dynamical convergence of several competing phenomena to an attractor which can represent an externum of a function, an image, a solution to a system of ODE, or a stochastic process.

  9. Quantum Computing with Quantum Dots

    NASA Astrophysics Data System (ADS)

    Burkard, Guido; Loss, Daniel

    1998-03-01

    We report recent results on the spin dynamics of coupled quantum dots and their potential as quantum computer devices. Using the Heitler-London approach, we obtain the exchange coupling J(B,a) between the excess electrons of coupled dots.(D.P. DiVincenzo and D. Loss, Quantum Computation is Physical), to appear in Superlattices and Microstructures. Special Issue on the occasion of Rolf Landauer's 70th Birthday, ed. S. Datta. See cond- mat/9710259. The dependence of J on the magnetic field B and the interdot distance 2a is of great importance for controlling the coherent time-evolution of the two-spin system as required for quantum computation.(D. Loss and D.P. DiVincenzo, Phys. Rev. A, in press. See cond- mat/9701055.) Our result, which is in good agreement with a more refined LCAO calculation, is accessible to experimental tests via magnetic response measurements.

  10. Quantum computational geometry

    NASA Astrophysics Data System (ADS)

    Lanzagorta, Marco; Uhlmann, Jeffrey K.

    2004-08-01

    The prospects for practical quantum computing have improved significantly over the past few years, and there is an increasing motivation for developing quantum algorithms to address problems that are presently impractical to solve using classical computing. In previous work we have indentified such problems in the areas of computer graphics applications, and we have derived quantum-based solutions. In this paper we examine quantum-based solutions to problems arising in the area of computational geometry. These types of problems are important in a variety of scientific, industrial and military applications such as large scale multi-object simulation, virtual reality systems, and multi-target tracking. In particular, we present quantum algorithms for multidimensional searches, convex hull construction, and collision detection.

  11. Quantum computation: Honesty test

    NASA Astrophysics Data System (ADS)

    Morimae, Tomoyuki

    2013-11-01

    Alice does not have a quantum computer so she delegates a computation to Bob, who does own one. But how can Alice check whether the computation that Bob performs for her is correct? An experiment with photonic qubits demonstrates such a verification protocol.

  12. Towards Quantum Computational Logics

    NASA Astrophysics Data System (ADS)

    Ledda, Antonio; Sergioli, Giuseppe

    2010-12-01

    Quantum computational logics have recently stirred increasing attention (Cattaneo et al. in Math. Slovaca 54:87-108, 2004; Ledda et al. in Stud. Log. 82(2):245-270, 2006; Giuntini et al. in Stud. Log. 87(1):99-128, 2007). In this paper we outline their motivations and report on the state of the art of the approach to the logic of quantum computation that has been recently taken up and developed by our research group.

  13. Layered Architectures for Quantum Computers and Quantum Repeaters

    NASA Astrophysics Data System (ADS)

    Jones, Nathan C.

    This chapter examines how to organize quantum computers and repeaters using a systematic framework known as layered architecture, where machine control is organized in layers associated with specialized tasks. The framework is flexible and could be used for analysis and comparison of quantum information systems. To demonstrate the design principles in practice, we develop architectures for quantum computers and quantum repeaters based on optically controlled quantum dots, showing how a myriad of technologies must operate synchronously to achieve fault-tolerance. Optical control makes information processing in this system very fast, scalable to large problem sizes, and extendable to quantum communication.

  14. Quantum computational webs

    SciTech Connect

    Gross, D.; Eisert, J.

    2010-10-15

    We discuss the notion of quantum computational webs: These are quantum states universal for measurement-based computation, which can be built up from a collection of simple primitives. The primitive elements--reminiscent of building blocks in a construction kit--are (i) one-dimensional states (computational quantum wires) with the power to process one logical qubit and (ii) suitable couplings, which connect the wires to a computationally universal web. All elements are preparable by nearest-neighbor interactions in a single pass, of the kind accessible in a number of physical architectures. We provide a complete classification of qubit wires, a physically well-motivated class of universal resources that can be fully understood. Finally, we sketch possible realizations in superlattices and explore the power of coupling mechanisms based on Ising or exchange interactions.

  15. Computational quantum chemistry website

    SciTech Connect

    1997-08-22

    This report contains the contents of a web page related to research on the development of quantum chemistry methods for computational thermochemistry and the application of quantum chemistry methods to problems in material chemistry and chemical sciences. Research programs highlighted include: Gaussian-2 theory; Density functional theory; Molecular sieve materials; Diamond thin-film growth from buckyball precursors; Electronic structure calculations on lithium polymer electrolytes; Long-distance electronic coupling in donor/acceptor molecules; and Computational studies of NOx reactions in radioactive waste storage.

  16. Undergraduate computational physics projects on quantum computing

    NASA Astrophysics Data System (ADS)

    Candela, D.

    2015-08-01

    Computational projects on quantum computing suitable for students in a junior-level quantum mechanics course are described. In these projects students write their own programs to simulate quantum computers. Knowledge is assumed of introductory quantum mechanics through the properties of spin 1/2. Initial, more easily programmed projects treat the basics of quantum computation, quantum gates, and Grover's quantum search algorithm. These are followed by more advanced projects to increase the number of qubits and implement Shor's quantum factoring algorithm. The projects can be run on a typical laptop or desktop computer, using most programming languages. Supplementing resources available elsewhere, the projects are presented here in a self-contained format especially suitable for a short computational module for physics students.

  17. Demonstration of blind quantum computing.

    PubMed

    Barz, Stefanie; Kashefi, Elham; Broadbent, Anne; Fitzsimons, Joseph F; Zeilinger, Anton; Walther, Philip

    2012-01-20

    Quantum computers, besides offering substantial computational speedups, are also expected to preserve the privacy of a computation. We present an experimental demonstration of blind quantum computing in which the input, computation, and output all remain unknown to the computer. We exploit the conceptual framework of measurement-based quantum computation that enables a client to delegate a computation to a quantum server. Various blind delegated computations, including one- and two-qubit gates and the Deutsch and Grover quantum algorithms, are demonstrated. The client only needs to be able to prepare and transmit individual photonic qubits. Our demonstration is crucial for unconditionally secure quantum cloud computing and might become a key ingredient for real-life applications, especially when considering the challenges of making powerful quantum computers widely available. PMID:22267806

  18. Blind topological measurement-based quantum computation.

    PubMed

    Morimae, Tomoyuki; Fujii, Keisuke

    2012-01-01

    Blind quantum computation is a novel secure quantum-computing protocol that enables Alice, who does not have sufficient quantum technology at her disposal, to delegate her quantum computation to Bob, who has a fully fledged quantum computer, in such a way that Bob cannot learn anything about Alice's input, output and algorithm. A recent proof-of-principle experiment demonstrating blind quantum computation in an optical system has raised new challenges regarding the scalability of blind quantum computation in realistic noisy conditions. Here we show that fault-tolerant blind quantum computation is possible in a topologically protected manner using the Raussendorf-Harrington-Goyal scheme. The error threshold of our scheme is 4.3 10(-3), which is comparable to that (7.5 10(-3)) of non-blind topological quantum computation. As the error per gate of the order 10(-3) was already achieved in some experimental systems, our result implies that secure cloud quantum computation is within reach. PMID:22948818

  19. Blind topological measurement-based quantum computation

    PubMed Central

    Morimae, Tomoyuki; Fujii, Keisuke

    2012-01-01

    Blind quantum computation is a novel secure quantum-computing protocol that enables Alice, who does not have sufficient quantum technology at her disposal, to delegate her quantum computation to Bob, who has a fully fledged quantum computer, in such a way that Bob cannot learn anything about Alice's input, output and algorithm. A recent proof-of-principle experiment demonstrating blind quantum computation in an optical system has raised new challenges regarding the scalability of blind quantum computation in realistic noisy conditions. Here we show that fault-tolerant blind quantum computation is possible in a topologically protected manner using the RaussendorfHarringtonGoyal scheme. The error threshold of our scheme is 4.310?3, which is comparable to that (7.510?3) of non-blind topological quantum computation. As the error per gate of the order 10?3 was already achieved in some experimental systems, our result implies that secure cloud quantum computation is within reach. PMID:22948818

  20. Relativistic quantum chemistry on quantum computers

    NASA Astrophysics Data System (ADS)

    Veis, Libor; Vi?k, Jakub; Fleig, Timo; Knecht, Stefan; Saue, Trond; Visscher, Lucas; Pittner, Ji?

    2012-03-01

    The past few years have witnessed a remarkable interest in the application of quantum computing for solving problems in quantum chemistry more efficiently than classical computers allow. Very recently, proof-of-principle experimental realizations have been reported. However, so far only the nonrelativistic regime (i.e., the Schrdinger equation) has been explored, while it is well known that relativistic effects can be very important in chemistry. We present a quantum algorithm for relativistic computations of molecular energies. We show how to efficiently solve the eigenproblem of the Dirac-Coulomb Hamiltonian on a quantum computer and demonstrate the functionality of the proposed procedure by numerical simulations of computations of the spin-orbit splitting in the SbH molecule. Finally, we propose quantum circuits with three qubits and nine or ten controlled-not (cnot) gates, which implement a proof-of-principle relativistic quantum chemical calculation for this molecule and might be suitable for an experimental realization.

  1. Quantum computers: Definition and implementations

    SciTech Connect

    Perez-Delgado, Carlos A.; Kok, Pieter

    2011-01-15

    The DiVincenzo criteria for implementing a quantum computer have been seminal in focusing both experimental and theoretical research in quantum-information processing. These criteria were formulated specifically for the circuit model of quantum computing. However, several new models for quantum computing (paradigms) have been proposed that do not seem to fit the criteria well. Therefore, the question is what are the general criteria for implementing quantum computers. To this end, a formal operational definition of a quantum computer is introduced. It is then shown that, according to this definition, a device is a quantum computer if it obeys the following criteria: Any quantum computer must consist of a quantum memory, with an additional structure that (1) facilitates a controlled quantum evolution of the quantum memory; (2) includes a method for information theoretic cooling of the memory; and (3) provides a readout mechanism for subsets of the quantum memory. The criteria are met when the device is scalable and operates fault tolerantly. We discuss various existing quantum computing paradigms and how they fit within this framework. Finally, we present a decision tree for selecting an avenue toward building a quantum computer. This is intended to help experimentalists determine the most natural paradigm given a particular physical implementation.

  2. Some Thoughts Regarding Practical Quantum Computing

    NASA Astrophysics Data System (ADS)

    Ghoshal, Debabrata; Gomez, Richard; Lanzagorta, Marco; Uhlmann, Jeffrey

    2006-03-01

    Quantum computing has become an important area of research in computer science because of its potential to provide more efficient algorithmic solutions to certain problems than are possible with classical computing. The ability of performing parallel operations over an exponentially large computational space has proved to be the main advantage of the quantum computing model. In this regard, we are particularly interested in the potential applications of quantum computers to enhance real software systems of interest to the defense, industrial, scientific and financial communities. However, while much has been written in popular and scientific literature about the benefits of the quantum computational model, several of the problems associated to the practical implementation of real-life complex software systems in quantum computers are often ignored. In this presentation we will argue that practical quantum computation is not as straightforward as commonly advertised, even if the technological problems associated to the manufacturing and engineering of large-scale quantum registers were solved overnight. We will discuss some of the frequently overlooked difficulties that plague quantum computing in the areas of memories, I/O, addressing schemes, compilers, oracles, approximate information copying, logical debugging, error correction and fault-tolerant computing protocols.

  3. Quantum Gravity on a Quantum Computer?

    NASA Astrophysics Data System (ADS)

    Kempf, Achim

    2014-05-01

    EPR-type measurements on spatially separated entangled spin qubits allow one, in principle, to detect curvature. Also the entanglement of the vacuum state is affected by curvature. Here, we ask if the curvature of spacetime can be expressed entirely in terms of the spatial entanglement structure of the vacuum. This would open up the prospect that quantum gravity could be simulated on a quantum computer and that quantum information techniques could be fully employed in the study of quantum gravity.

  4. Quantum Walk Schemes for Universal Quantum Computation

    NASA Astrophysics Data System (ADS)

    Underwood, Michael S.

    Random walks are a powerful tool for the efficient implementation of algorithms in classical computation. Their quantum-mechanical analogues, called quantum walks, hold similar promise. Quantum walks provide a model of quantum computation that has recently been shown to be equivalent in power to the standard circuit model. As in the classical case, quantum walks take place on graphs and can undergo discrete or continuous evolution, though quantum evolution is unitary and therefore deterministic until a measurement is made. This thesis considers the usefulness of continuous-time quantum walks to quantum computation from the perspectives of both their fundamental power under various formulations, and their applicability in practical experiments. In one extant scheme, logical gates are effected by scattering processes. The results of an exhaustive search for single-qubit operations in this model are presented. It is shown that the number of distinct operations increases exponentially with the number of vertices in the scattering graph. A catalogue of all graphs on up to nine vertices that implement single-qubit unitaries at a specific set of momenta is included in an appendix. I develop a novel scheme for universal quantum computation called the discontinuous quantum walk, in which a continuous-time quantum walker takes discrete steps of evolution via perfect quantum state transfer through small 'widget' graphs. The discontinuous quantum-walk scheme requires an exponentially sized graph, as do prior discrete and continuous schemes. To eliminate the inefficient vertex resource requirement, a computation scheme based on multiple discontinuous walkers is presented. In this model, n interacting walkers inhabiting a graph with 2n vertices can implement an arbitrary quantum computation on an input of length n, an exponential savings over previous universal quantum walk schemes. This is the first quantum walk scheme that allows for the application of quantum error correction. The many-particle quantum walk can be viewed as a single quantum walk undergoing perfect state transfer on a larger weighted graph, obtained via equitable partitioning. I extend this formalism to non-simple graphs. Examples of the application of equitable partitioning to the analysis of quantum walks and many-particle quantum systems are discussed.

  5. Quantum computing on encrypted data.

    PubMed

    Fisher, K A G; Broadbent, A; Shalm, L K; Yan, Z; Lavoie, J; Prevedel, R; Jennewein, T; Resch, K J

    2014-01-01

    The ability to perform computations on encrypted data is a powerful tool for protecting privacy. Recently, protocols to achieve this on classical computing systems have been found. Here, we present an efficient solution to the quantum analogue of this problem that enables arbitrary quantum computations to be carried out on encrypted quantum data. We prove that an untrusted server can implement a universal set of quantum gates on encrypted quantum bits (qubits) without learning any information about the inputs, while the client, knowing the decryption key, can easily decrypt the results of the computation. We experimentally demonstrate, using single photons and linear optics, the encryption and decryption scheme on a set of gates sufficient for arbitrary quantum computations. As our protocol requires few extra resources compared with other schemes it can be easily incorporated into the design of future quantum servers. These results will play a key role in enabling the development of secure distributed quantum systems. PMID:24445949

  6. Quantum computing on encrypted data

    NASA Astrophysics Data System (ADS)

    Fisher, K. A. G.; Broadbent, A.; Shalm, L. K.; Yan, Z.; Lavoie, J.; Prevedel, R.; Jennewein, T.; Resch, K. J.

    2014-01-01

    The ability to perform computations on encrypted data is a powerful tool for protecting privacy. Recently, protocols to achieve this on classical computing systems have been found. Here, we present an efficient solution to the quantum analogue of this problem that enables arbitrary quantum computations to be carried out on encrypted quantum data. We prove that an untrusted server can implement a universal set of quantum gates on encrypted quantum bits (qubits) without learning any information about the inputs, while the client, knowing the decryption key, can easily decrypt the results of the computation. We experimentally demonstrate, using single photons and linear optics, the encryption and decryption scheme on a set of gates sufficient for arbitrary quantum computations. As our protocol requires few extra resources compared with other schemes it can be easily incorporated into the design of future quantum servers. These results will play a key role in enabling the development of secure distributed quantum systems.

  7. Decoherence in adiabatic quantum computation

    NASA Astrophysics Data System (ADS)

    Albash, Tameem; Lidar, Daniel A.

    2015-06-01

    Recent experiments with increasingly larger numbers of qubits have sparked renewed interest in adiabatic quantum computation, and in particular quantum annealing. A central question that is repeatedly asked is whether quantum features of the evolution can survive over the long time scales used for quantum annealing relative to standard measures of the decoherence time. We reconsider the role of decoherence in adiabatic quantum computation and quantum annealing using the adiabatic quantum master-equation formalism. We restrict ourselves to the weak-coupling and singular-coupling limits, which correspond to decoherence in the energy eigenbasis and in the computational basis, respectively. We demonstrate that decoherence in the instantaneous energy eigenbasis does not necessarily detrimentally affect adiabatic quantum computation, and in particular that a short single-qubit T2 time need not imply adverse consequences for the success of the quantum adiabatic algorithm. We further demonstrate that boundary cancellation methods, designed to improve the fidelity of adiabatic quantum computing in the closed-system setting, remain beneficial in the open-system setting. To address the high computational cost of master-equation simulations, we also demonstrate that a quantum Monte Carlo algorithm that explicitly accounts for a thermal bosonic bath can be used to interpolate between classical and quantum annealing. Our study highlights and clarifies the significantly different role played by decoherence in the adiabatic and circuit models of quantum computing.

  8. Quantum computations on a topologically encoded qubit.

    PubMed

    Nigg, D; Mller, M; Martinez, E A; Schindler, P; Hennrich, M; Monz, T; Martin-Delgado, M A; Blatt, R

    2014-07-18

    The construction of a quantum computer remains a fundamental scientific and technological challenge because of the influence of unavoidable noise. Quantum states and operations can be protected from errors through the use of protocols for quantum computing with faulty components. We present a quantum error-correcting code in which one qubit is encoded in entangled states distributed over seven trapped-ion qubits. The code can detect one bit flip error, one phase flip error, or a combined error of both, regardless on which of the qubits they occur. We applied sequences of gate operations on the encoded qubit to explore its computational capabilities. This seven-qubit code represents a fully functional instance of a topologically encoded qubit, or color code, and opens a route toward fault-tolerant quantum computing. PMID:24925911

  9. Universal quantum computation with weakly integral anyons

    NASA Astrophysics Data System (ADS)

    Cui, Shawn X.; Hong, Seung-Moon; Wang, Zhenghan

    2015-08-01

    Harnessing non-abelian statistics of anyons to perform quantum computational tasks is getting closer to reality. While the existence of universal anyons by braiding alone such as the Fibonacci anyon is theoretically a possibility, accessible anyons with current technology all belong to a class that is called weakly integralanyons whose squared quantum dimensions are integers. We analyze the computational power of the first non-abelian anyon system with only integral quantum dimensions, the quantum double of . Since all anyons in have finite images of braid group representations, they cannot be universal for quantum computation by braiding alone. Based on our knowledge of the images of the braid group representations, we set up three qutrit computational models. Supplementing braidings with some measurements and ancillary states, we find a universal gate set for each model.

  10. Universal quantum computation by discontinuous quantum walk

    SciTech Connect

    Underwood, Michael S.; Feder, David L.

    2010-10-15

    Quantum walks are the quantum-mechanical analog of random walks, in which a quantum ''walker'' evolves between initial and final states by traversing the edges of a graph, either in discrete steps from node to node or via continuous evolution under the Hamiltonian furnished by the adjacency matrix of the graph. We present a hybrid scheme for universal quantum computation in which a quantum walker takes discrete steps of continuous evolution. This ''discontinuous'' quantum walk employs perfect quantum-state transfer between two nodes of specific subgraphs chosen to implement a universal gate set, thereby ensuring unitary evolution without requiring the introduction of an ancillary coin space. The run time is linear in the number of simulated qubits and gates. The scheme allows multiple runs of the algorithm to be executed almost simultaneously by starting walkers one time step apart.

  11. Interfacing External Quantum Devices to a Universal Quantum Computer

    PubMed Central

    Lagana, Antonio A.; Lohe, Max A.; von Smekal, Lorenz

    2011-01-01

    We present a scheme to use external quantum devices using the universal quantum computer previously constructed. We thereby show how the universal quantum computer can utilize networked quantum information resources to carry out local computations. Such information may come from specialized quantum devices or even from remote universal quantum computers. We show how to accomplish this by devising universal quantum computer programs that implement well known oracle based quantum algorithms, namely the Deutsch, Deutsch-Jozsa, and the Grover algorithms using external black-box quantum oracle devices. In the process, we demonstrate a method to map existing quantum algorithms onto the universal quantum computer. PMID:22216276

  12. Quantum Computation Using Optically Coupled Quantum Dot Arrays

    NASA Technical Reports Server (NTRS)

    Pradhan, Prabhakar; Anantram, M. P.; Wang, K. L.; Roychowhury, V. P.; Saini, Subhash (Technical Monitor)

    1998-01-01

    A solid state model for quantum computation has potential advantages in terms of the ease of fabrication, characterization, and integration. The fundamental requirements for a quantum computer involve the realization of basic processing units (qubits), and a scheme for controlled switching and coupling among the qubits, which enables one to perform controlled operations on qubits. We propose a model for quantum computation based on optically coupled quantum dot arrays, which is computationally similar to the atomic model proposed by Cirac and Zoller. In this model, individual qubits are comprised of two coupled quantum dots, and an array of these basic units is placed in an optical cavity. Switching among the states of the individual units is done by controlled laser pulses via near field interaction using the NSOM technology. Controlled rotations involving two or more qubits are performed via common cavity mode photon. We have calculated critical times, including the spontaneous emission and switching times, and show that they are comparable to the best times projected for other proposed models of quantum computation. We have also shown the feasibility of accessing individual quantum dots using the NSOM technology by calculating the photon density at the tip, and estimating the power necessary to perform the basic controlled operations. We are currently in the process of estimating the decoherence times for this system; however, we have formulated initial arguments which seem to indicate that the decoherence times will be comparable, if not longer, than many other proposed models.

  13. Entanglement and Quantum Computation: An Overview

    SciTech Connect

    Perez, R.B.

    2000-06-27

    This report presents a selective compilation of basic facts from the fields of particle entanglement and quantum information processing prepared for those non-experts in these fields that may have interest in an area of physics showing counterintuitive, ''spooky'' (Einstein's words) behavior. In fact, quantum information processing could, in the near future, provide a new technology to sustain the benefits to the U.S. economy due to advanced computer technology.

  14. Algorithms on ensemble quantum computers.

    PubMed

    Boykin, P Oscar; Mor, Tal; Roychowdhury, Vwani; Vatan, Farrokh

    2010-06-01

    In ensemble (or bulk) quantum computation, all computations are performed on an ensemble of computers rather than on a single computer. Measurements of qubits in an individual computer cannot be performed; instead, only expectation values (over the complete ensemble of computers) can be measured. As a result of this limitation on the model of computation, many algorithms cannot be processed directly on such computers, and must be modified, as the common strategy of delaying the measurements usually does not resolve this ensemble-measurement problem. Here we present several new strategies for resolving this problem. Based on these strategies we provide new versions of some of the most important quantum algorithms, versions that are suitable for implementing on ensemble quantum computers, e.g., on liquid NMR quantum computers. These algorithms are Shor's factorization algorithm, Grover's search algorithm (with several marked items), and an algorithm for quantum fault-tolerant computation. The first two algorithms are simply modified using a randomizing and a sorting strategies. For the last algorithm, we develop a classical-quantum hybrid strategy for removing measurements. We use it to present a novel quantum fault-tolerant scheme. More explicitly, we present schemes for fault-tolerant measurement-free implementation of Toffoli and ?(z)() as these operations cannot be implemented "bitwise", and their standard fault-tolerant implementations require measurement. PMID:21475662

  15. Simulating chemistry using quantum computers.

    PubMed

    Kassal, Ivan; Whitfield, James D; Perdomo-Ortiz, Alejandro; Yung, Man-Hong; Aspuru-Guzik, Aln

    2011-01-01

    The difficulty of simulating quantum systems, well known to quantum chemists, prompted the idea of quantum computation. One can avoid the steep scaling associated with the exact simulation of increasingly large quantum systems on conventional computers, by mapping the quantum system to another, more controllable one. In this review, we discuss to what extent the ideas in quantum computation, now a well-established field, have been applied to chemical problems. We describe algorithms that achieve significant advantages for the electronic-structure problem, the simulation of chemical dynamics, protein folding, and other tasks. Although theory is still ahead of experiment, we outline recent advances that have led to the first chemical calculations on small quantum information processors. PMID:21166541

  16. Quantum Computing: Solving Complex Problems

    ScienceCinema

    DiVincenzo, David [IBM Watson Research Center

    2009-09-01

    One of the motivating ideas of quantum computation was that there could be a new kind of machine that would solve hard problems in quantum mechanics. There has been significant progress towards the experimental realization of these machines (which I will review), but there are still many questions about how such a machine could solve computational problems of interest in quantum physics. New categorizations of the complexity of computational problems have now been invented to describe quantum simulation. The bad news is that some of these problems are believed to be intractable even on a quantum computer, falling into a quantum analog of the NP class. The good news is that there are many other new classifications of tractability that may apply to several situations of physical interest.

  17. Molecular Magnets for Quantum Computation

    NASA Astrophysics Data System (ADS)

    Kuroda, Takayoshi

    2009-06-01

    We review recent progress in molecular magnets especially in the viewpoint of the application for quantum computing. After a brief introduction to single-molecule magnets (SMMs), a method for qubit manipulation by using non-equidistant spin sublevels of a SMM will be introduced. A weakly-coupled dimer of two SMMs is also a candidate for quantum computing, which shows no quantum tunneling of magnetization (QTM) at zero field. In the AF ring Cr7Ni system, the large tunnel splitting is a great advantage to reduce decoherence during manipulation, which can be a possible candidate to realize quantum computer devices in future.

  18. The Physics of Quantum Computation

    NASA Astrophysics Data System (ADS)

    Falci, Giuseppe; Paladino, Elisabette

    2015-10-01

    Quantum Computation has emerged in the past decades as a consequence of down-scaling of electronic devices to the mesoscopic regime and of advances in the ability of controlling and measuring microscopic quantum systems. QC has many interdisciplinary aspects, ranging from physics and chemistry to mathematics and computer science. In these lecture notes we focus on physical hardware, present day challenges and future directions for design of quantum architectures.

  19. Geometric methods in quantum computation

    NASA Astrophysics Data System (ADS)

    Zhang, Jun

    Recent advances in the physical sciences and engineering have created great hopes for new computational paradigms and substrates. One such new approach is the quantum computer, which holds the promise of enhanced computational power. Analogous to the way a classical computer is built from electrical circuits containing wires and logic gates, a quantum computer is built from quantum circuits containing quantum wires and elementary quantum gates to transport and manipulate quantum information. Therefore, design of quantum gates and quantum circuits is a prerequisite for any real application of quantum computation. In this dissertation we apply geometric control methods from differential geometry and Lie group representation theory to analyze the properties of quantum gates and to design optimal quantum circuits. Using the Cartan decomposition and the Weyl group, we show that the geometric structure of nonlocal two-qubit gates is a 3-Torus. After further reducing the symmetry, the geometric representation of nonlocal gates is seen to be conveniently visualized as a tetrahedron. Each point in this tetrahedron except on the base corresponds to a different equivalent class of nonlocal gates. This geometric representation is one of the cornerstones for the discussion on quantum computation in this dissertation. We investigate the properties of those two-qubit operations that can generate maximal entanglement. It is an astonishing finding that if we randomly choose a two-qubit operation, the probability that we obtain a perfect entangler is exactly one half. We prove that given a two-body interaction Hamiltonian, it is always possible to explicitly construct a quantum circuit for exact simulation of any arbitrary nonlocal two-qubit gate by turning on the two-body interaction for at most three times, together with at most four local gates. We also provide an analytic approach to construct a universal quantum circuit from any entangling gate supplemented with local gates. Closed form solutions have been derived for each step in this explicit construction procedure. Moreover, the minimum upper bound is found to construct a universal quantum circuit from any Controlled-Unitary gate. A near optimal explicit construction of universal quantum circuits from a given Controlled-Unitary is provided. For the Controlled-NOT and Double-CNOT gate, we then develop simple analytic ways to construct universal quantum circuits with exactly three applications, which is the least possible for these gates. We further discover a new quantum gate (named B gate) that achieves the desired universality with minimal number of gates. Optimal implementation of single-qubit quantum gates is also investigated. Finally, as a real physical application, a constructive way to implement any arbitrary two-qubit operation on a spin electronics system is discussed.

  20. Efficient universal blind quantum computation.

    PubMed

    Giovannetti, Vittorio; Maccone, Lorenzo; Morimae, Tomoyuki; Rudolph, Terry G

    2013-12-01

    We give a cheat sensitive protocol for blind universal quantum computation that is efficient in terms of computational and communication resources: it allows one party to perform an arbitrary computation on a second party's quantum computer without revealing either which computation is performed, or its input and output. The first party's computational capabilities can be extremely limited: she must only be able to create and measure single-qubit superposition states. The second party is not required to use measurement-based quantum computation. The protocol requires the (optimal) exchange of O(Jlog2(N)) single-qubit states, where J is the computational depth and N is the number of qubits needed for the computation. PMID:24476238

  1. Programmable architecture for quantum computing

    NASA Astrophysics Data System (ADS)

    Chen, Jialin; Wang, Lingli; Charbon, Edoardo; Wang, Bin

    2013-08-01

    A programmable architecture called quantum FPGA (field-programmable gate array) (QFPGA) is presented for quantum computing, which is a hybrid model combining the advantages of the qubus system and the measurement-based quantum computation. There are two kinds of buses in QFPGA, the local bus and the global bus, which generate the cluster states and general multiqubit rotations around the z axis, respectively. QFPGA consists of quantum logic blocks (QLBs) and quantum routing channels (QRCs). The QLB is used to generate a small quantum logic while the QRC is used to combine them properly for larger logic realization. Considering the error accumulating on the qubus, the small logic is the general two-qubit quantum gate. However, for the application such as n-qubit quantum Fourier transform, one QLB can be reconfigured for four-qubit quantum Fourier transform. Although this is an implementation-independent architecture, we still make a rough analysis of its performance based on the qubus system. In a word, QFPGA provides a general architecture to integrate different quantum computing models for efficient quantum logic construction.

  2. Duality quantum computer and the efficient quantum simulations

    NASA Astrophysics Data System (ADS)

    Wei, Shi-Jie; Long, Gui-Lu

    2016-03-01

    Duality quantum computing is a new mode of a quantum computer to simulate a moving quantum computer passing through a multi-slit. It exploits the particle wave duality property for computing. A quantum computer with n qubits and a qudit simulates a moving quantum computer with n qubits passing through a d-slit. Duality quantum computing can realize an arbitrary sum of unitaries and therefore a general quantum operator, which is called a generalized quantum gate. All linear bounded operators can be realized by the generalized quantum gates, and unitary operators are just the extreme points of the set of generalized quantum gates. Duality quantum computing provides flexibility and a clear physical picture in designing quantum algorithms, and serves as a powerful bridge between quantum and classical algorithms. In this paper, after a brief review of the theory of duality quantum computing, we will concentrate on the applications of duality quantum computing in simulations of Hamiltonian systems. We will show that duality quantum computing can efficiently simulate quantum systems by providing descriptions of the recent efficient quantum simulation algorithm of Childs and Wiebe (Quantum Inf Comput 12(11-12):901-924, 2012) for the fast simulation of quantum systems with a sparse Hamiltonian, and the quantum simulation algorithm by Berry et al. (Phys Rev Lett 114:090502, 2015), which provides exponential improvement in precision for simulating systems with a sparse Hamiltonian.

  3. Entanglement echoes in quantum computation

    SciTech Connect

    Rossini, Davide; Benenti, Giuliano; Casati, Giulio

    2004-05-01

    We study the stability of entanglement in a quantum computer implementing an efficient quantum algorithm, which simulates a quantum chaotic dynamics. For this purpose, we perform a forward-backward evolution of an initial state in which two qubits are in a maximally entangled Bell state. If the dynamics is reversed after an evolution time t{sub r}, there is an echo of the entanglement between these two qubits at time t{sub e}=2t{sub r}. Perturbations attenuate the pairwise entanglement echo and generate entanglement between these two qubits and the other qubits of the quantum computer.

  4. Toward a superconducting quantum computer

    PubMed Central

    Tsai, Jaw-Shen

    2010-01-01

    Intensive research on the construction of superconducting quantum computers has produced numerous important achievements. The quantum bit (qubit), based on the Josephson junction, is at the heart of this research. This macroscopic system has the ability to control quantum coherence. This article reviews the current state of quantum computing as well as its history, and discusses its future. Although progress has been rapid, the field remains beset with unsolved issues, and there are still many new research opportunities open to physicists and engineers. PMID:20431256

  5. Insecurity of quantum secure computations

    NASA Astrophysics Data System (ADS)

    Lo, Hoi-Kwong

    1997-08-01

    It had been widely claimed that quantum mechanics can protect private information during public decision in, for example, the so-called two-party secure computation. If this were the case, quantum smart-cards, storing confidential information accessible only to a proper reader, could prevent fake teller machines from learning the PIN (personal identification number) from the customers' input. Although such optimism has been challenged by the recent surprising discovery of the insecurity of the so-called quantum bit commitment, the security of quantum two-party computation itself remains unaddressed. Here I answer this question directly by showing that all one-sided two-party computations (which allow only one of the two parties to learn the result) are necessarily insecure. As corollaries to my results, quantum one-way oblivious password identification and the so-called quantum one-out-of-two oblivious transfer are impossible. I also construct a class of functions that cannot be computed securely in any two-sided two-party computation. Nevertheless, quantum cryptography remains useful in key distribution and can still provide partial security in ``quantum money'' proposed by Wiesner.

  6. Computational Power of Quantum Machines, Quantum Grammars and Feasible Computation

    NASA Astrophysics Data System (ADS)

    Krishnamurthy, E. V.

    This paper studies the computational power of quantum computers to explore as to whether they can recognize properties which are in nondeterministic polynomial-time class (NP) and beyond. To study the computational power, we use the Feynman's path integral (FPI) formulation of quantum mechanics. From a computational point of view the Feynman's path integral computes a quantum dynamical analogue of the k-ary relation computed by an Alternating Turing machine (ATM) using AND-OR Parallelism. Hence, if we can find a suitable mapping function between an instance of a mathematical problem and the corresponding interference problem, using suitable potential functions for which FPI can be integrated exactly, the computational power of a quantum computer can be bounded to that of an alternating Turing machine that can solve problems in NP (e.g, factorization problem) and in polynomial space. Unfortunately, FPI is exactly integrable only for a few problems (e.g., the harmonic oscillator) involving quadratic potentials; otherwise, they may be only approximately computable or noncomputable. This means we cannot in general solve all quantum dynamical problems exactly except for those special cases of quadratic potentials, e.g., harmonic oscillator. Since there is a one to one correspondence between the quantum mechanical problems that can be analytically solved and the path integrals that can be exactly evaluated, we can say that the noncomputability of FPI implies quantum unsolvability. This is the analogue of classical unsolvability. The Feynman's path graph can be considered as a semantic parse graph for the quantum mechanical sentence. It provides a semantic valuation function of the terminal sentence based on probability amplitudes to disambiguate a given quantum description and obtain an interpretation in a linear time. In Feynman's path integral, the kernels are partially ordered over time (different alternate paths acting concurrently at the same time) and multiplied. The semantic valuation is computable only if the FPI is computable. Thus both the expressive power and complexity aspects quantum computing are mirrored by the exact and efficient integrability of FPI.

  7. Surfing Electrons in Quantum Computers?

    NASA Astrophysics Data System (ADS)

    Pomeau, Y.

    I take this opportunity of writing a piece of science for my friend Manuel G. Velarde to discuss things dear to his heart: surfing of electrons on acoustic waves. It has been claimed recently, but not by him, that transport of electrons by surf could be used to carry quantum information in quantum computers. This is physically impossible because this would require to maintain the quantum coherence linked to localisation, a coherence decaying very fastly in the real world.

  8. The quantum field as a quantum computer

    NASA Astrophysics Data System (ADS)

    D'Ariano, Giacomo Mauro

    2012-01-01

    It is supposed that at very small scales a quantum field is an infinite homogeneous quantum computer. On a quantum computer the information cannot propagate faster than c=a/?, a and ? being the minimum space and time distances between gates, respectively. For one space dimension it is shown that the information flow satisfies a Dirac equation, with speed v=?c and ?=?(m) mass-dependent. For c the speed of light ? is a vacuum refraction index that increases monotonically from ?(0)=1 to ?(M)=?, M being the Planck mass for 2a the Planck length. The Fermi anticommuting field can be entirely qubitized, i.e. it can be written in terms of local Pauli matrices and with the field interaction remaining local on qubits. Extensions to larger space dimensions are discussed.

  9. PERTURBATION APPROACH FOR QUANTUM COMPUTATION

    SciTech Connect

    G. P. BERMAN; D. I. KAMENEV; V. I. TSIFRINOVICH

    2001-04-01

    We discuss how to simulate errors in the implementation of simple quantum logic operations in a nuclear spin quantum computer with many qubits, using radio-frequency pulses. We verify our perturbation approach using the exact solutions for relatively small (L = 10) number of qubits.

  10. Quantum chromodynamics with advanced computing

    SciTech Connect

    Kronfeld, Andreas S.; /Fermilab

    2008-07-01

    We survey results in lattice quantum chromodynamics from groups in the USQCD Collaboration. The main focus is on physics, but many aspects of the discussion are aimed at an audience of computational physicists.

  11. Accelerating commutation circuits in quantum computer networks

    NASA Astrophysics Data System (ADS)

    Jiang, Min; Huang, Xu; Chen, Xiaoping; Zhang, Zeng-ke

    2012-12-01

    In a high speed and packet-switched quantum computer network, a packet routing delay often leads to traffic jams, becoming a severe bottleneck for speeding up the transmission rate. Based on the delayed commutation circuit proposed in Phys. Rev. Lett. 97, 110502 (2006), we present an improved scheme for accelerating network transmission. For two more realistic scenarios, we utilize the characteristic of a quantum state to simultaneously implement a data switch and transmission that makes it possible to reduce the packet delay and route a qubit packet even before its address is determined. This circuit is further extended to the quantum network for the transmission of the unknown quantum information. The analysis demonstrates that quantum communication technology can considerably reduce the processing delay time and build faster and more efficient packet-switched networks.

  12. Symmetrically private information retrieval based on blind quantum computing

    NASA Astrophysics Data System (ADS)

    Sun, Zhiwei; Yu, Jianping; Wang, Ping; Xu, Lingling

    2015-05-01

    Universal blind quantum computation (UBQC) is a new secure quantum computing protocol which allows a user Alice who does not have any sophisticated quantum technology to delegate her computing to a server Bob without leaking any privacy. Using the features of UBQC, we propose a protocol to achieve symmetrically private information retrieval, which allows a quantum limited Alice to query an item from Bob with a fully fledged quantum computer; meanwhile, the privacy of both parties is preserved. The security of our protocol is based on the assumption that malicious Alice has no quantum computer, which avoids the impossibility proof of Lo. For the honest Alice, she is almost classical and only requires minimal quantum resources to carry out the proposed protocol. Therefore, she does not need any expensive laboratory which can maintain the coherence of complicated quantum experimental setups.

  13. Artificial Life in Quantum Technologies.

    PubMed

    Alvarez-Rodriguez, Unai; Sanz, Mikel; Lamata, Lucas; Solano, Enrique

    2016-01-01

    We develop a quantum information protocol that models the biological behaviours of individuals living in a natural selection scenario. The artificially engineered evolution of the quantum living units shows the fundamental features of life in a common environment, such as self-replication, mutation, interaction of individuals, and death. We propose how to mimic these bio-inspired features in a quantum-mechanical formalism, which allows for an experimental implementation achievable with current quantum platforms. This study paves the way for the realization of artificial life and embodied evolution with quantum technologies. PMID:26853918

  14. Artificial Life in Quantum Technologies

    PubMed Central

    Alvarez-Rodriguez, Unai; Sanz, Mikel; Lamata, Lucas; Solano, Enrique

    2016-01-01

    We develop a quantum information protocol that models the biological behaviours of individuals living in a natural selection scenario. The artificially engineered evolution of the quantum living units shows the fundamental features of life in a common environment, such as self-replication, mutation, interaction of individuals, and death. We propose how to mimic these bio-inspired features in a quantum-mechanical formalism, which allows for an experimental implementation achievable with current quantum platforms. This study paves the way for the realization of artificial life and embodied evolution with quantum technologies. PMID:26853918

  15. Artificial Life in Quantum Technologies

    NASA Astrophysics Data System (ADS)

    Alvarez-Rodriguez, Unai; Sanz, Mikel; Lamata, Lucas; Solano, Enrique

    2016-02-01

    We develop a quantum information protocol that models the biological behaviours of individuals living in a natural selection scenario. The artificially engineered evolution of the quantum living units shows the fundamental features of life in a common environment, such as self-replication, mutation, interaction of individuals, and death. We propose how to mimic these bio-inspired features in a quantum-mechanical formalism, which allows for an experimental implementation achievable with current quantum platforms. This study paves the way for the realization of artificial life and embodied evolution with quantum technologies.

  16. Semiquantum key distribution with secure delegated quantum computation

    NASA Astrophysics Data System (ADS)

    Li, Qin; Chan, Wai Hong; Zhang, Shengyu

    2016-01-01

    Semiquantum key distribution allows a quantum party to share a random key with a “classical” party who only can prepare and measure qubits in the computational basis or reorder some qubits when he has access to a quantum channel. In this work, we present a protocol where a secret key can be established between a quantum user and an almost classical user who only needs the quantum ability to access quantum channels, by securely delegating quantum computation to a quantum server. We show the proposed protocol is robust even when the delegated quantum server is a powerful adversary, and is experimentally feasible with current technology. As one party of our protocol is the most quantum-resource efficient, it can be more practical and significantly widen the applicability scope of quantum key distribution.

  17. Semiquantum key distribution with secure delegated quantum computation

    PubMed Central

    Li, Qin; Chan, Wai Hong; Zhang, Shengyu

    2016-01-01

    Semiquantum key distribution allows a quantum party to share a random key with a “classical” party who only can prepare and measure qubits in the computational basis or reorder some qubits when he has access to a quantum channel. In this work, we present a protocol where a secret key can be established between a quantum user and an almost classical user who only needs the quantum ability to access quantum channels, by securely delegating quantum computation to a quantum server. We show the proposed protocol is robust even when the delegated quantum server is a powerful adversary, and is experimentally feasible with current technology. As one party of our protocol is the most quantum-resource efficient, it can be more practical and significantly widen the applicability scope of quantum key distribution. PMID:26813384

  18. Semiquantum key distribution with secure delegated quantum computation.

    PubMed

    Li, Qin; Chan, Wai Hong; Zhang, Shengyu

    2016-01-01

    Semiquantum key distribution allows a quantum party to share a random key with a "classical" party who only can prepare and measure qubits in the computational basis or reorder some qubits when he has access to a quantum channel. In this work, we present a protocol where a secret key can be established between a quantum user and an almost classical user who only needs the quantum ability to access quantum channels, by securely delegating quantum computation to a quantum server. We show the proposed protocol is robust even when the delegated quantum server is a powerful adversary, and is experimentally feasible with current technology. As one party of our protocol is the most quantum-resource efficient, it can be more practical and significantly widen the applicability scope of quantum key distribution. PMID:26813384

  19. Quantum technology and its applications

    SciTech Connect

    Boshier, Malcolm; Berkeland, Dana; Govindan, Tr; Abo - Shaeer, Jamil

    2010-12-10

    Quantum states of matter can be exploited as high performance sensors for measuring time, gravity, rotation, and electromagnetic fields, and quantum states of light provide powerful new tools for imaging and communication. Much attention is being paid to the ultimate limits of this quantum technology. For example, it has already been shown that exotic quantum states can be used to measure or image with higher precision or higher resolution or lower radiated power than any conventional technologies, and proof-of-principle experiments demonstrating measurement precision below the standard quantum limit (shot noise) are just starting to appear. However, quantum technologies have another powerful advantage beyond pure sensing performance that may turn out to be more important in practical applications: the potential for building devices with lower size/weight/power (SWaP) and cost requirements than existing instruments. The organizers of Quantum Technology Applications Workshop (QTAW) have several goals: (1) Bring together sponsors, researchers, engineers and end users to help build a stronger quantum technology community; (2) Identify how quantum systems might improve the performance of practical devices in the near- to mid-term; and (3) Identify applications for which more long term investment is necessary to realize improved performance for realistic applications. To realize these goals, the QTAW II workshop included fifty scientists, engineers, managers and sponsors from academia, national laboratories, government and the private-sector. The agenda included twelve presentations, a panel discussion, several breaks for informal exchanges, and a written survey of participants. Topics included photon sources, optics and detectors, squeezed light, matter waves, atomic clocks and atom magnetometry. Corresponding applications included communication, imaging, optical interferometry, navigation, gravimetry, geodesy, biomagnetism, and explosives detection. Participants considered the physics and engineering of quantum and conventional technologies, and how quantum techniques could (or could not) overcome limitations of conventional systems. They identified several auxiliary technologies that needed to be further developed in order to make quantum technology more accessible. Much of the discussion also focused on specific applications of quantum technology and how to push the technology into broader communities, which would in turn identify new uses of the technology. Since our main interest is practical improvement of devices and techniques, we take a liberal definition of 'quantum technology': a system that utilizes preparation and measurement of a well-defined coherent quantum state. This nomenclature encompasses features broader than entanglement, squeezing or quantum correlations, which are often more difficult to utilize outside of a laboratory environment. Still, some applications discussed in the workshop do take advantage of these 'quantum-enhanced' features. They build on the more established quantum technologies that are amenable to manipulation at the quantum level, such as atom magnetometers and atomic clocks. Understanding and developing those technologies through traditional engineering will clarify where quantum-enhanced features can be used most effectively, in addition to providing end users with improved devices in the near-term.

  20. Realizing universal Majorana fermionic quantum computation

    NASA Astrophysics Data System (ADS)

    Wu, Ya-Jie; He, Jing; Kou, Su-Peng

    2014-08-01

    Majorana fermionic quantum computation (MFQC) was proposed by S. B. Bravyi and A. Yu. Kitaev [Ann. Phys. (NY) 298, 210 (2002), 10.1006/aphy.2002.6254], who indicated that a (nontopological) fault-tolerant quantum computer built from Majorana fermions may be more efficient than that built from distinguishable two-state systems. However, until now scientists have not known how to realize a MFQC in a physical system. In this paper we propose a possible realization of MFQC. We find that the end of a line defect of a p-wave superconductor or superfluid in a honeycomb lattice traps a Majorana zero mode, which becomes the starting point of MFQC. Then we show how to manipulate Majorana fermions to perform universal MFQC, which possesses possibilities for high-level local controllability through individually addressing the quantum states of individual constituent elements by using timely cold-atom technology.

  1. Quantum ballistic evolution in quantum mechanics: Application to quantum computers

    NASA Astrophysics Data System (ADS)

    Benioff, Paul

    1996-08-01

    Quantum computers are important examples of processes whose evolution can be described in terms of iterations of single-step operators or their adjoints. Based on this, Hamiltonian evolution of processes with associated step operators T is investigated here. The main limitation of this paper is to processes which evolve quantum ballistically, i.e., motion restricted to a collection of nonintersecting or distinct paths on an arbitrary basis. The main goal of this paper is proof of a theorem which gives necessary and sufficient conditions that T must satisfy so that there exists a Hamiltonian description of quantum ballistic evolution for the process, namely, that T is a partial isometry and is orthogonality preserving and stable on some basis. Simple examples of quantum ballistic evolution for quantum Turing machines with one and with more than one type of elementary step are discussed. It is seen that for nondeterministic machines the basis set can be quite complex with much entanglement present. It is also proven that, given a step operator T for an arbitrary deterministic quantum Turing machine, it is decidable if T is stable and orthogonality preserving, and if quantum ballistic evolution is possible. The proof fails if T is a step operator for a nondeterministic machine. It is an open question if such a decision procedure exists for nondeterministic machines. This problem does not occur in classical mechanics. Also the definition of quantum Turing machines used here is compared with that used by other authors.

  2. Self-correcting quantum computers

    NASA Astrophysics Data System (ADS)

    Bombin, H.; Chhajlany, R. W.; Horodecki, M.; Martin-Delgado, M. A.

    2013-05-01

    Is the notion of a quantum computer (QC) resilient to thermal noise unphysical? We address this question from a constructive perspective and show that local quantum Hamiltonian models provide self-correcting QCs. To this end, we first give a sufficient condition on the connectedness of excitations for a stabilizer code model to be a self-correcting quantum memory. We then study the two main examples of topological stabilizer codes in arbitrary dimensions and establish their self-correcting capabilities. Also, we address the transversality properties of topological color codes, showing that six-dimensional color codes provide a self-correcting model that allows the transversal and local implementation of a universal set of operations in seven spatial dimensions. Finally, we give a procedure for initializing such quantum memories at finite temperature.

  3. Silicon-based Quantum Computing

    NASA Astrophysics Data System (ADS)

    Clark, Robert

    2002-03-01

    The Australian Centre for Quantum Computer Technology has as a central focus the construction of few-qubit silicon-based solid state devices for test, by a reliable, reproducable and potentially scalable fabrication route. A description will be given of the fabrication approaches underway, with progress to date. Three principal objectives are within reach: 1. The ability to dope silicon with phosphorus in an atomically-precise array, using STM-lithography and Si-MBE overgrowth. 2. The construction of few-donor QC devices using single-ion implantation through nanofabricated apertures, with on-chip detection, self-aligned control gates and single electron transistor (SET) readout devices. 3. A high frequency experiment, using rf-SETs, to measure the coherent electron transfer between two buried phosphorus donor atoms constituting a nanostructured H_2^+ molecule encapsulated in silicon. This work is being carried out in collaboration with Los Alamos National Laboratory and is funded by the Australian Research Council, the Australian Government, the US Army Research Office, National Security Agency and Advanced Research and Development Activity.

  4. Quantum computing and hidden variables

    SciTech Connect

    Aaronson, Scott

    2005-03-01

    This paper initiates the study of hidden variables from a quantum computing perspective. For us, a hidden-variable theory is simply a way to convert a unitary matrix that maps one quantum state to another into a stochastic matrix that maps the initial probability distribution to the final one in some fixed basis. We list five axioms that we might want such a theory to satisfy and then investigate which of the axioms can be satisfied simultaneously. Toward this end, we propose a new hidden-variable theory based on network flows. In a second part of the paper, we show that if we could examine the entire history of a hidden variable, then we could efficiently solve problems that are believed to be intractable even for quantum computers. In particular, under any hidden-variable theory satisfying a reasonable axiom, we could solve the graph isomorphism problem in polynomial time, and could search an N-item database using O(N{sup 1/3}) queries, as opposed to O(N{sup 1/2}) queries with Grover's search algorithm. On the other hand, the N{sup 1/3} bound is optimal, meaning that we could probably not solve NP-complete problems in polynomial time. We thus obtain the first good example of a model of computation that appears slightly more powerful than the quantum computing model.

  5. Computer Technology for Industry

    NASA Technical Reports Server (NTRS)

    1979-01-01

    In this age of the computer, more and more business firms are automating their operations for increased efficiency in a great variety of jobs, from simple accounting to managing inventories, from precise machining to analyzing complex structures. In the interest of national productivity, NASA is providing assistance both to longtime computer users and newcomers to automated operations. Through a special technology utilization service, NASA saves industry time and money by making available already developed computer programs which have secondary utility. A computer program is essentially a set of instructions which tells the computer how to produce desired information or effect by drawing upon its stored input. Developing a new program from scratch can be costly and time-consuming. Very often, however, a program developed for one purpose can readily be adapted to a totally different application. To help industry take advantage of existing computer technology, NASA operates the Computer Software Management and Information Center (COSMIC)(registered TradeMark),located at the University of Georgia. COSMIC maintains a large library of computer programs developed for NASA, the Department of Defense, the Department of Energy and other technology-generating agencies of the government. The Center gets a continual flow of software packages, screens them for adaptability to private sector usage, stores them and informs potential customers of their availability.

  6. From transistor to trapped-ion computers for quantum chemistry

    NASA Astrophysics Data System (ADS)

    Yung, M.-H.; Casanova, J.; Mezzacapo, A.; McClean, J.; Lamata, L.; Aspuru-Guzik, A.; Solano, E.

    2014-01-01

    Over the last few decades, quantum chemistry has progressed through the development of computational methods based on modern digital computers. However, these methods can hardly fulfill the exponentially-growing resource requirements when applied to large quantum systems. As pointed out by Feynman, this restriction is intrinsic to all computational models based on classical physics. Recently, the rapid advancement of trapped-ion technologies has opened new possibilities for quantum control and quantum simulations. Here, we present an efficient toolkit that exploits both the internal and motional degrees of freedom of trapped ions for solving problems in quantum chemistry, including molecular electronic structure, molecular dynamics, and vibronic coupling. We focus on applications that go beyond the capacity of classical computers, but may be realizable on state-of-the-art trapped-ion systems. These results allow us to envision a new paradigm of quantum chemistry that shifts from the current transistor to a near-future trapped-ion-based technology.

  7. Control aspects of quantum computing using pure and mixed states

    PubMed Central

    Schulte-Herbrggen, Thomas; Marx, Raimund; Fahmy, Amr; Kauffman, Louis; Lomonaco, Samuel; Khaneja, Navin; Glaser, Steffen J.

    2012-01-01

    Steering quantum dynamics such that the target states solve classically hard problems is paramount to quantum simulation and computation. And beyond, quantum control is also essential to pave the way to quantum technologies. Here, important control techniques are reviewed and presented in a unified frame covering quantum computational gate synthesis and spectroscopic state transfer alike. We emphasize that it does not matter whether the quantum states of interest are pure or not. While pure states underly the design of quantum circuits, ensemble mixtures of quantum states can be exploited in a more recent class of algorithms: it is illustrated by characterizing the Jones polynomial in order to distinguish between different (classes of) knots. Further applications include Josephson elements, cavity grids, ion traps and nitrogen vacancy centres in scenarios of closed as well as open quantum systems. PMID:22946034

  8. Computable measure of quantum correlation

    NASA Astrophysics Data System (ADS)

    Akhtarshenas, S. Javad; Mohammadi, Hamidreza; Karimi, Saman; Azmi, Zahra

    2015-01-01

    A general state of an system is a classical-quantum state if and only if its associated -correlation matrix (a matrix constructed from the coherence vector of the party , the correlation matrix of the state, and a function of the local coherence vector of the subsystem ), has rank no larger than . Using the general Schatten -norms, we quantify quantum correlation by measuring any violation of this condition. The required minimization can be carried out for the general -norms and any function of the local coherence vector of the unmeasured subsystem, leading to a class of computable quantities which can be used to capture the quantumness of correlations due to the subsystem . We introduce two special members of these quantifiers: The first one coincides with the tight lower bound on the geometric measure of discord, so that such lower bound fully captures the quantum correlation of a bipartite system. Accordingly, a vanishing tight lower bound on the geometric discord is a necessary and sufficient condition for a state to be zero-discord. The second quantifier has the property that it is invariant under a local and reversible operation performed on the unmeasured subsystem, so that it can be regarded as a computable well-defined measure of the quantum correlations. The approach presented in this paper provides a way to circumvent the problem with the geometric discord. We provide some examples to exemplify this measure.

  9. Quantum technologies with hybrid systems.

    PubMed

    Kurizki, Gershon; Bertet, Patrice; Kubo, Yuimaru; Mlmer, Klaus; Petrosyan, David; Rabl, Peter; Schmiedmayer, Jrg

    2015-03-31

    An extensively pursued current direction of research in physics aims at the development of practical technologies that exploit the effects of quantum mechanics. As part of this ongoing effort, devices for quantum information processing, secure communication, and high-precision sensing are being implemented with diverse systems, ranging from photons, atoms, and spins to mesoscopic superconducting and nanomechanical structures. Their physical properties make some of these systems better suited than others for specific tasks; thus, photons are well suited for transmitting quantum information, weakly interacting spins can serve as long-lived quantum memories, and superconducting elements can rapidly process information encoded in their quantum states. A central goal of the envisaged quantum technologies is to develop devices that can simultaneously perform several of these tasks, namely, reliably store, process, and transmit quantum information. Hybrid quantum systems composed of different physical components with complementary functionalities may provide precisely such multitasking capabilities. This article reviews some of the driving theoretical ideas and first experimental realizations of hybrid quantum systems and the opportunities and challenges they present and offers a glance at the near- and long-term perspectives of this fascinating and rapidly expanding field. PMID:25737558

  10. Quantum technologies with hybrid systems

    PubMed Central

    Kurizki, Gershon; Bertet, Patrice; Kubo, Yuimaru; Mølmer, Klaus; Petrosyan, David; Rabl, Peter; Schmiedmayer, Jörg

    2015-01-01

    An extensively pursued current direction of research in physics aims at the development of practical technologies that exploit the effects of quantum mechanics. As part of this ongoing effort, devices for quantum information processing, secure communication, and high-precision sensing are being implemented with diverse systems, ranging from photons, atoms, and spins to mesoscopic superconducting and nanomechanical structures. Their physical properties make some of these systems better suited than others for specific tasks; thus, photons are well suited for transmitting quantum information, weakly interacting spins can serve as long-lived quantum memories, and superconducting elements can rapidly process information encoded in their quantum states. A central goal of the envisaged quantum technologies is to develop devices that can simultaneously perform several of these tasks, namely, reliably store, process, and transmit quantum information. Hybrid quantum systems composed of different physical components with complementary functionalities may provide precisely such multitasking capabilities. This article reviews some of the driving theoretical ideas and first experimental realizations of hybrid quantum systems and the opportunities and challenges they present and offers a glance at the near- and long-term perspectives of this fascinating and rapidly expanding field. PMID:25737558

  11. Demonstration of measurement-only blind quantum computing

    NASA Astrophysics Data System (ADS)

    Greganti, Chiara; Roehsner, Marie-Christine; Barz, Stefanie; Morimae, Tomoyuki; Walther, Philip

    2016-01-01

    Blind quantum computing allows for secure cloud networks of quasi-classical clients and a fully fledged quantum server. Recently, a new protocol has been proposed, which requires a client to perform only measurements. We demonstrate a proof-of-principle implementation of this measurement-only blind quantum computing, exploiting a photonic setup to generate four-qubit cluster states for computation and verification. Feasible technological requirements for the client and the device-independent blindness make this scheme very applicable for future secure quantum networks.

  12. Quantum computing accelerator I/O : LDRD 52750 final report.

    SciTech Connect

    Schroeppel, Richard Crabtree; Modine, Normand Arthur; Ganti, Anand; Pierson, Lyndon George; Tigges, Christopher P.

    2003-12-01

    In a superposition of quantum states, a bit can be in both the states '0' and '1' at the same time. This feature of the quantum bit or qubit has no parallel in classical systems. Currently, quantum computers consisting of 4 to 7 qubits in a 'quantum computing register' have been built. Innovative algorithms suited to quantum computing are now beginning to emerge, applicable to sorting and cryptanalysis, and other applications. A framework for overcoming slightly inaccurate quantum gate interactions and for causing quantum states to survive interactions with surrounding environment is emerging, called quantum error correction. Thus there is the potential for rapid advances in this field. Although quantum information processing can be applied to secure communication links (quantum cryptography) and to crack conventional cryptosystems, the first few computing applications will likely involve a 'quantum computing accelerator' similar to a 'floating point arithmetic accelerator' interfaced to a conventional Von Neumann computer architecture. This research is to develop a roadmap for applying Sandia's capabilities to the solution of some of the problems associated with maintaining quantum information, and with getting data into and out of such a 'quantum computing accelerator'. We propose to focus this work on 'quantum I/O technologies' by applying quantum optics on semiconductor nanostructures to leverage Sandia's expertise in semiconductor microelectronic/photonic fabrication techniques, as well as its expertise in information theory, processing, and algorithms. The work will be guided by understanding of practical requirements of computing and communication architectures. This effort will incorporate ongoing collaboration between 9000, 6000 and 1000 and between junior and senior personnel. Follow-on work to fabricate and evaluate appropriate experimental nano/microstructures will be proposed as a result of this work.

  13. Quantum computing with parafermions

    NASA Astrophysics Data System (ADS)

    Hutter, Adrian; Loss, Daniel

    2016-03-01

    Zd parafermions are exotic non-Abelian quasiparticles generalizing Majorana fermions, which correspond to the case d =2 . In contrast to Majorana fermions, braiding of parafermions with d >2 allows one to perform an entangling gate. This has spurred interest in parafermions, and a variety of condensed matter systems have been proposed as potential hosts for them. In this work, we study the computational power of braiding parafermions more systematically. We make no assumptions on the underlying physical model but derive all our results from the algebraical relations that define parafermions. We find a family of 2 d representations of the braid group that are compatible with these relations. The braiding operators derived this way reproduce those derived previously from physical grounds as special cases. We show that if a d -level qudit is encoded in the fusion space of four parafermions, braiding of these four parafermions allows one to generate the entire single-qudit Clifford group (up to phases), for any d . If d is odd, then we show that in fact the entire many-qudit Clifford group can be generated.

  14. Brain Neurons as Quantum Computers:

    NASA Astrophysics Data System (ADS)

    Bershadskii, A.; Dremencov, E.; Bershadskii, J.; Yadid, G.

    The question: whether quantum coherent states can sustain decoherence, heating and dissipation over time scales comparable to the dynamical timescales of brain neurons, has been actively discussed in the last years. A positive answer on this question is crucial, in particular, for consideration of brain neurons as quantum computers. This discussion was mainly based on theoretical arguments. In the present paper nonlinear statistical properties of the Ventral Tegmental Area (VTA) of genetically depressive limbic brain are studied in vivo on the Flinders Sensitive Line of rats (FSL). VTA plays a key role in the generation of pleasure and in the development of psychological drug addiction. We found that the FSL VTA (dopaminergic) neuron signals exhibit multifractal properties for interspike frequencies on the scales where healthy VTA dopaminergic neurons exhibit bursting activity. For high moments the observed multifractal (generalized dimensions) spectrum coincides with the generalized dimensions spectrum calculated for a spectral measure of a quantum system (so-called kicked Harper model, actively used as a model of quantum chaos). This observation can be considered as a first experimental (in vivo) indication in the favor of the quantum (at least partially) nature of brain neurons activity.

  15. Geometry of quantum computation with qutrits.

    PubMed

    Li, Bin; Yu, Zu-Huan; Fei, Shao-Ming

    2013-01-01

    Determining the quantum circuit complexity of a unitary operation is an important problem in quantum computation. By using the mathematical techniques of Riemannian geometry, we investigate the efficient quantum circuits in quantum computation with n qutrits. We show that the optimal quantum circuits are essentially equivalent to the shortest path between two points in a certain curved geometry of SU(3(n)). As an example, three-qutrit systems are investigated in detail. PMID:24005379

  16. Quantum chemistry simulation on quantum computers: theories and experiments.

    PubMed

    Lu, Dawei; Xu, Boruo; Xu, Nanyang; Li, Zhaokai; Chen, Hongwei; Peng, Xinhua; Xu, Ruixue; Du, Jiangfeng

    2012-07-14

    It has been claimed that quantum computers can mimic quantum systems efficiently in the polynomial scale. Traditionally, those simulations are carried out numerically on classical computers, which are inevitably confronted with the exponential growth of required resources, with the increasing size of quantum systems. Quantum computers avoid this problem, and thus provide a possible solution for large quantum systems. In this paper, we first discuss the ideas of quantum simulation, the background of quantum simulators, their categories, and the development in both theories and experiments. We then present a brief introduction to quantum chemistry evaluated via classical computers followed by typical procedures of quantum simulation towards quantum chemistry. Reviewed are not only theoretical proposals but also proof-of-principle experimental implementations, via a small quantum computer, which include the evaluation of the static molecular eigenenergy and the simulation of chemical reaction dynamics. Although the experimental development is still behind the theory, we give prospects and suggestions for future experiments. We anticipate that in the near future quantum simulation will become a powerful tool for quantum chemistry over classical computations. PMID:22652702

  17. Innovative quantum technologies for microgravity fundamental physics and biological research

    NASA Technical Reports Server (NTRS)

    Kierk, I. K.

    2002-01-01

    This paper presents a new technology program, within the fundamental physics, focusing on four quantum technology areas: quantum atomics, quantum optics, space superconductivity and quantum sensor technology, and quantum field based sensor and modeling technology.

  18. Innovative quantum technologies for microgravity fundamental physics and biological research

    NASA Technical Reports Server (NTRS)

    Kierk, I.; Israelsson, U.; Lee, M.

    2001-01-01

    This paper presents a new technology program, within the fundamental physics research program, focusing on four quantum technology areas: quantum atomics, quantum optics, space superconductivity and quantum sensor technology, and quantum fluid based sensor and modeling technology.

  19. Exploiting Locality in Quantum Computation for Quantum Chemistry.

    PubMed

    McClean, Jarrod R; Babbush, Ryan; Love, Peter J; Aspuru-Guzik, Alán

    2014-12-18

    Accurate prediction of chemical and material properties from first-principles quantum chemistry is a challenging task on traditional computers. Recent developments in quantum computation offer a route toward highly accurate solutions with polynomial cost; however, this solution still carries a large overhead. In this Perspective, we aim to bring together known results about the locality of physical interactions from quantum chemistry with ideas from quantum computation. We show that the utilization of spatial locality combined with the Bravyi-Kitaev transformation offers an improvement in the scaling of known quantum algorithms for quantum chemistry and provides numerical examples to help illustrate this point. We combine these developments to improve the outlook for the future of quantum chemistry on quantum computers. PMID:26273989

  20. Computational multiqubit tunnelling in programmable quantum annealers.

    PubMed

    Boixo, Sergio; Smelyanskiy, Vadim N; Shabani, Alireza; Isakov, Sergei V; Dykman, Mark; Denchev, Vasil S; Amin, Mohammad H; Smirnov, Anatoly Yu; Mohseni, Masoud; Neven, Hartmut

    2016-01-01

    Quantum tunnelling is a phenomenon in which a quantum state traverses energy barriers higher than the energy of the state itself. Quantum tunnelling has been hypothesized as an advantageous physical resource for optimization in quantum annealing. However, computational multiqubit tunnelling has not yet been observed, and a theory of co-tunnelling under high- and low-frequency noises is lacking. Here we show that 8-qubit tunnelling plays a computational role in a currently available programmable quantum annealer. We devise a probe for tunnelling, a computational primitive where classical paths are trapped in a false minimum. In support of the design of quantum annealers we develop a nonperturbative theory of open quantum dynamics under realistic noise characteristics. This theory accurately predicts the rate of many-body dissipative quantum tunnelling subject to the polaron effect. Furthermore, we experimentally demonstrate that quantum tunnelling outperforms thermal hopping along classical paths for problems with up to 200 qubits containing the computational primitive. PMID:26739797

  1. Computational multiqubit tunnelling in programmable quantum annealers

    PubMed Central

    Boixo, Sergio; Smelyanskiy, Vadim N.; Shabani, Alireza; Isakov, Sergei V.; Dykman, Mark; Denchev, Vasil S.; Amin, Mohammad H.; Smirnov, Anatoly Yu; Mohseni, Masoud; Neven, Hartmut

    2016-01-01

    Quantum tunnelling is a phenomenon in which a quantum state traverses energy barriers higher than the energy of the state itself. Quantum tunnelling has been hypothesized as an advantageous physical resource for optimization in quantum annealing. However, computational multiqubit tunnelling has not yet been observed, and a theory of co-tunnelling under high- and low-frequency noises is lacking. Here we show that 8-qubit tunnelling plays a computational role in a currently available programmable quantum annealer. We devise a probe for tunnelling, a computational primitive where classical paths are trapped in a false minimum. In support of the design of quantum annealers we develop a nonperturbative theory of open quantum dynamics under realistic noise characteristics. This theory accurately predicts the rate of many-body dissipative quantum tunnelling subject to the polaron effect. Furthermore, we experimentally demonstrate that quantum tunnelling outperforms thermal hopping along classical paths for problems with up to 200 qubits containing the computational primitive. PMID:26739797

  2. Computational multiqubit tunnelling in programmable quantum annealers

    NASA Astrophysics Data System (ADS)

    Boixo, Sergio; Smelyanskiy, Vadim N.; Shabani, Alireza; Isakov, Sergei V.; Dykman, Mark; Denchev, Vasil S.; Amin, Mohammad H.; Smirnov, Anatoly Yu; Mohseni, Masoud; Neven, Hartmut

    2016-01-01

    Quantum tunnelling is a phenomenon in which a quantum state traverses energy barriers higher than the energy of the state itself. Quantum tunnelling has been hypothesized as an advantageous physical resource for optimization in quantum annealing. However, computational multiqubit tunnelling has not yet been observed, and a theory of co-tunnelling under high- and low-frequency noises is lacking. Here we show that 8-qubit tunnelling plays a computational role in a currently available programmable quantum annealer. We devise a probe for tunnelling, a computational primitive where classical paths are trapped in a false minimum. In support of the design of quantum annealers we develop a nonperturbative theory of open quantum dynamics under realistic noise characteristics. This theory accurately predicts the rate of many-body dissipative quantum tunnelling subject to the polaron effect. Furthermore, we experimentally demonstrate that quantum tunnelling outperforms thermal hopping along classical paths for problems with up to 200 qubits containing the computational primitive.

  3. The Quantum Human Computer (QHC) Hypothesis

    ERIC Educational Resources Information Center

    Salmani-Nodoushan, Mohammad Ali

    2008-01-01

    This article attempts to suggest the existence of a human computer called Quantum Human Computer (QHC) on the basis of an analogy between human beings and computers. To date, there are two types of computers: Binary and Quantum. The former operates on the basis of binary logic where an object is said to exist in either of the two states of 1 and…

  4. Nanophotonic quantum computer based on atomic quantum transistor

    NASA Astrophysics Data System (ADS)

    Andrianov, S. N.; Moiseev, S. A.

    2015-10-01

    We propose a scheme of a quantum computer based on nanophotonic elements: two buses in the form of nanowaveguide resonators, two nanosized units of multiatom multiqubit quantum memory and a set of nanoprocessors in the form of photonic quantum transistors, each containing a pair of nanowaveguide ring resonators coupled via a quantum dot. The operation modes of nanoprocessor photonic quantum transistors are theoretically studied and the execution of main logical operations by means of them is demonstrated. We also discuss the prospects of the proposed nanophotonic quantum computer for operating in high-speed optical fibre networks.

  5. Universal quantum computation using the discrete-time quantum walk

    SciTech Connect

    Lovett, Neil B.; Cooper, Sally; Everitt, Matthew; Trevers, Matthew; Kendon, Viv

    2010-04-15

    A proof that continuous-time quantum walks are universal for quantum computation, using unweighted graphs of low degree, has recently been presented by A. M. Childs [Phys. Rev. Lett. 102, 180501 (2009)]. We present a version based instead on the discrete-time quantum walk. We show that the discrete-time quantum walk is able to implement the same universal gate set and thus both discrete and continuous-time quantum walks are computational primitives. Additionally, we give a set of components on which the discrete-time quantum walk provides perfect state transfer.

  6. Gate-count estimates for performing quantum chemistry on small quantum computers

    NASA Astrophysics Data System (ADS)

    Wecker, Dave; Bauer, Bela; Clark, Bryan K.; Hastings, Matthew B.; Troyer, Matthias

    2014-08-01

    As quantum computing technology improves and quantum computers with a small but nontrivial number of N ≥100 qubits appear feasible in the near future the question of possible applications of small quantum computers gains importance. One frequently mentioned application is Feynman's original proposal of simulating quantum systems and, in particular, the electronic structure of molecules and materials. In this paper, we analyze the computational requirements for one of the standard algorithms to perform quantum chemistry on a quantum computer. We focus on the quantum resources required to find the ground state of a molecule twice as large as what current classical computers can solve exactly. We find that while such a problem requires about a 10-fold increase in the number of qubits over current technology, the required increase in the number of gates that can be coherently executed is many orders of magnitude larger. This suggests that for quantum computation to become useful for quantum chemistry problems, drastic algorithmic improvements will be needed.

  7. Non-unitary probabilistic quantum computing

    NASA Technical Reports Server (NTRS)

    Gingrich, Robert M.; Williams, Colin P.

    2004-01-01

    We present a method for designing quantum circuits that perform non-unitary quantum computations on n-qubit states probabilistically, and give analytic expressions for the success probability and fidelity.

  8. Contextuality supplies the 'magic' for quantum computation.

    PubMed

    Howard, Mark; Wallman, Joel; Veitch, Victor; Emerson, Joseph

    2014-06-19

    Quantum computers promise dramatic advantages over their classical counterparts, but the source of the power in quantum computing has remained elusive. Here we prove a remarkable equivalence between the onset of contextuality and the possibility of universal quantum computation via 'magic state' distillation, which is the leading model for experimentally realizing a fault-tolerant quantum computer. This is a conceptually satisfying link, because contextuality, which precludes a simple 'hidden variable' model of quantum mechanics, provides one of the fundamental characterizations of uniquely quantum phenomena. Furthermore, this connection suggests a unifying paradigm for the resources of quantum information: the non-locality of quantum theory is a particular kind of contextuality, and non-locality is already known to be a critical resource for achieving advantages with quantum communication. In addition to clarifying these fundamental issues, this work advances the resource framework for quantum computation, which has a number of practical applications, such as characterizing the efficiency and trade-offs between distinct theoretical and experimental schemes for achieving robust quantum computation, and putting bounds on the overhead cost for the classical simulation of quantum algorithms. PMID:24919152

  9. Quantum computing with steady state spin currents

    NASA Astrophysics Data System (ADS)

    Sutton, Brian M.

    Many approaches to quantum computing use spatially confined qubits in the presence of dynamic fields to perform computation. These approaches are contrasted with proposals using mobile qubits in the presence of static fields. In this thesis, steady state quantum computing using mobile electrons is explored using numerical modeling. Firstly, a foundational introduction to the case of spatially confined qubits embodied via quantum dots is provided. A collection of universal gates implemented with dynamic fields is described using simulations. These gates are combined to implement a five-qubit Grover search to provide further insight on the time-dependent field approach. Secondly, the quantum dot description is contrasted with quantum computing using steady state spin currents. Leveraging the Non-Equilibrium Greens Function formalism to perform numerical simulations, the quantum aspects of steady state spin currents are explored by revisiting the Stern-Gerlach experiment using spin-polarized contacts on a one-dimensional channel. After demonstrating the quantum nature of mobile electrons at steady state, arbitrary single qubit operations using static fields are explored. The model is further extended to incorporate two-qubit interactions to realize the square root of SWAP gate. The two-qubit CNOT gate is used to prepare a Bell state, which is read via quantum state tomography. Finally, Grover's search is revisited to explore the performance benefits of steady state quantum computing. The described multi-particle model is applicable to mobile qubit quantum computing proposals leveraging synchronized electron transport in static fields to perform quantum computing.

  10. Assumptions for fault tolerant quantum computing

    SciTech Connect

    Knill, E.; Laflamme, R.

    1996-06-01

    Assumptions useful for fault tolerant quantum computing are stated and briefly discussed. We focus on assumptions related to properties of the computational system. The strongest form of the assumptions seems to be sufficient for achieving highly fault tolerant quantum computation. We discuss weakenings which are also likely to suffice.

  11. Quantum computation speedup limits from quantum metrological precision bounds

    NASA Astrophysics Data System (ADS)

    Demkowicz-Dobrzański, Rafał; Markiewicz, Marcin

    2015-06-01

    We propose a scheme for translating metrological precision bounds into lower bounds on query complexity of quantum search algorithms. Within the scheme the link between quadratic performance enhancement in idealized quantum metrological and quantum computing schemes becomes clear. More importantly, we utilize results from the field of quantum metrology on a generic loss of quadratic quantum precision enhancement in the presence of decoherence to infer an analogous generic loss of quadratic speedup in oracle based quantum computing. While most of our reasoning is rigorous, at one of the final steps, we need to make use of an unproven technical conjecture. We hope that we will be able to amend this deficiency in the near future, but we are convinced that even without the conjecture proven our results provide a deep insight into the relationship between quantum algorithms and quantum metrology protocols.

  12. Disciplines, models, and computers: the path to computational quantum chemistry.

    PubMed

    Lenhard, Johannes

    2014-12-01

    Many disciplines and scientific fields have undergone a computational turn in the past several decades. This paper analyzes this sort of turn by investigating the case of computational quantum chemistry. The main claim is that the transformation from quantum to computational quantum chemistry involved changes in three dimensions. First, on the side of instrumentation, small computers and a networked infrastructure took over the lead from centralized mainframe architecture. Second, a new conception of computational modeling became feasible and assumed a crucial role. And third, the field of computa- tional quantum chemistry became organized in a market-like fashion and this market is much bigger than the number of quantum theory experts. These claims will be substantiated by an investigation of the so-called density functional theory (DFT), the arguably pivotal theory in the turn to computational quantum chemistry around 1990. PMID:25571750

  13. Quantum Computational Logics and Possible Applications

    NASA Astrophysics Data System (ADS)

    Chiara, Maria Luisa Dalla; Giuntini, Roberto; Leporini, Roberto; di Francia, Giuliano Toraldo

    2008-01-01

    In quantum computational logics meanings of formulas are identified with quantum information quantities: systems of qubits or, more generally, mixtures of systems of qubits. We consider two kinds of quantum computational semantics: (1) a compositional semantics, where the meaning of a compound formula is determined by the meanings of its parts; (2) a holistic semantics, which makes essential use of the characteristic “holistic” features of the quantum-theoretic formalism. The compositional and the holistic semantics turn out to characterize the same logic. In this framework, one can introduce the notion of quantum-classical truth table, which corresponds to the most natural way for a quantum computer to calculate classical tautologies. Quantum computational logics can be applied to investigate different kinds of semantic phenomena where holistic, contextual and gestaltic patterns play an essential role (from natural languages to musical compositions).

  14. Prospects for quantum computation with trapped ions

    SciTech Connect

    Hughes, R.J.; James, D.F.V.

    1997-12-31

    Over the past decade information theory has been generalized to allow binary data to be represented by two-state quantum mechanical systems. (A single two-level system has come to be known as a qubit in this context.) The additional freedom introduced into information physics with quantum systems has opened up a variety of capabilities that go well beyond those of conventional information. For example, quantum cryptography allows two parties to generate a secret key even in the presence of eavesdropping. But perhaps the most remarkable capabilities have been predicted in the field of quantum computation. Here, a brief survey of the requirements for quantum computational hardware, and an overview of the in trap quantum computation project at Los Alamos are presented. The physical limitations to quantum computation with trapped ions are discussed.

  15. Experimental realization of quantum games on a quantum computer.

    PubMed

    Du, Jiangfeng; Li, Hui; Xu, Xiaodong; Shi, Mingjun; Wu, Jihui; Zhou, Xianyi; Han, Rongdian

    2002-04-01

    We generalize the quantum prisoner's dilemma to the case where the players share a nonmaximally entangled states. We show that the game exhibits an intriguing structure as a function of the amount of entanglement with two thresholds which separate a classical region, an intermediate region, and a fully quantum region. Furthermore this quantum game is experimentally realized on our nuclear magnetic resonance quantum computer. PMID:11955126

  16. Quantum computing. Defining and detecting quantum speedup.

    PubMed

    Rnnow, Troels F; Wang, Zhihui; Job, Joshua; Boixo, Sergio; Isakov, Sergei V; Wecker, David; Martinis, John M; Lidar, Daniel A; Troyer, Matthias

    2014-07-25

    The development of small-scale quantum devices raises the question of how to fairly assess and detect quantum speedup. Here, we show how to define and measure quantum speedup and how to avoid pitfalls that might mask or fake such a speedup. We illustrate our discussion with data from tests run on a D-Wave Two device with up to 503 qubits. By using random spin glass instances as a benchmark, we found no evidence of quantum speedup when the entire data set is considered and obtained inconclusive results when comparing subsets of instances on an instance-by-instance basis. Our results do not rule out the possibility of speedup for other classes of problems and illustrate the subtle nature of the quantum speedup question. PMID:25061205

  17. The Heisenberg representation of quantum computers

    SciTech Connect

    Gottesman, D.

    1998-06-24

    Since Shor`s discovery of an algorithm to factor numbers on a quantum computer in polynomial time, quantum computation has become a subject of immense interest. Unfortunately, one of the key features of quantum computers--the difficulty of describing them on classical computers--also makes it difficult to describe and understand precisely what can be done with them. A formalism describing the evolution of operators rather than states has proven extremely fruitful in understanding an important class of quantum operations. States used in error correction and certain communication protocols can be described by their stabilizer, a group of tensor products of Pauli matrices. Even this simple group structure is sufficient to allow a rich range of quantum effects, although it falls short of the full power of quantum computation.

  18. Experimental realization of nonadiabatic holonomic quantum computation.

    PubMed

    Feng, Guanru; Xu, Guofu; Long, Guilu

    2013-05-10

    Because of its geometric nature, holonomic quantum computation is fault tolerant against certain types of control errors. Although proposed more than a decade ago, the experimental realization of holonomic quantum computation is still an open challenge. In this Letter, we report the first experimental demonstration of nonadiabatic holonomic quantum computation in a liquid NMR quantum information processor. Two noncommuting one-qubit holonomic gates, rotations about x and z axes, and the two-qubit holonomic CNOT gate are realized by evolving the work qubits and an ancillary qubit nonadiabatically. The successful realizations of these universal elementary gates in nonadiabatic holonomic quantum computation demonstrates the experimental feasibility of this quantum computing paradigm. PMID:23705695

  19. Quantum Computer Games: Schrodinger Cat and Hounds

    ERIC Educational Resources Information Center

    Gordon, Michal; Gordon, Goren

    2012-01-01

    The quantum computer game "Schrodinger cat and hounds" is the quantum extension of the well-known classical game fox and hounds. Its main objective is to teach the unique concepts of quantum mechanics in a fun way. "Schrodinger cat and hounds" demonstrates the effects of superposition, destructive and constructive interference, measurements and

  20. Pseudospin quantum computation in semiconductor nanostructures.

    PubMed

    Scarola, V W; Park, K; Sarma, S Das

    2003-10-17

    We theoretically show that spontaneously interlayer-coherent bilayer quantum Hall droplets should allow robust and fault-tolerant pseudospin quantum computation in semiconductor nanostructures with voltage-tuned external gates providing qubit control and a quantum Ising Hamiltonian providing qubit entanglement. Using a spin-boson model, we estimate decoherence to be small (approximately 10(-5)). PMID:14611443

  1. Quantum Computer Games: Schrodinger Cat and Hounds

    ERIC Educational Resources Information Center

    Gordon, Michal; Gordon, Goren

    2012-01-01

    The quantum computer game "Schrodinger cat and hounds" is the quantum extension of the well-known classical game fox and hounds. Its main objective is to teach the unique concepts of quantum mechanics in a fun way. "Schrodinger cat and hounds" demonstrates the effects of superposition, destructive and constructive interference, measurements and…

  2. How to test the ``quantumness'' of a quantum computer?

    NASA Astrophysics Data System (ADS)

    Zagoskin, Alexandre; Il'ichev, Evgeni; Grajcar, Miroslav; Betouras, Joseph; Nori, Franco

    2014-05-01

    Recent devices, using hundreds of superconducting quantum bits, claim to perform quantum computing. However, it is not an easy task to determine and quantify the degree of quantum coherence and control used by these devices. Namely, it is a difficult task to know with certainty whether or not a given device (e.g., the D-Wave One or D-Wave Two) is a quantum computer. Such a verification of quantum computing would be more accessible if we already had some kind of working quantum computer, to be able to compare the outputs of these various computing devices. Moreover, the verification process itself could strongly depend on whether the tested device is a standard (gate-based) or, e.g., an adiabatic quantum computer. Here we do not propose a technical solution to this quantum-computing verification problem, but rather outline the problem in a way which would help both specialists and non-experts to see the scale of this difficult task, and indicate some possible paths towards its solution.

  3. PREFACE: Quantum Information, Communication, Computation and Cryptography

    NASA Astrophysics Data System (ADS)

    Benatti, F.; Fannes, M.; Floreanini, R.; Petritis, D.

    2007-07-01

    The application of quantum mechanics to information related fields such as communication, computation and cryptography is a fast growing line of research that has been witnessing an outburst of theoretical and experimental results, with possible practical applications. On the one hand, quantum cryptography with its impact on secrecy of transmission is having its first important actual implementations; on the other hand, the recent advances in quantum optics, ion trapping, BEC manipulation, spin and quantum dot technologies allow us to put to direct test a great deal of theoretical ideas and results. These achievements have stimulated a reborn interest in various aspects of quantum mechanics, creating a unique interplay between physics, both theoretical and experimental, mathematics, information theory and computer science. In view of all these developments, it appeared timely to organize a meeting where graduate students and young researchers could be exposed to the fundamentals of the theory, while senior experts could exchange their latest results. The activity was structured as a school followed by a workshop, and took place at The Abdus Salam International Center for Theoretical Physics (ICTP) and The International School for Advanced Studies (SISSA) in Trieste, Italy, from 12-23 June 2006. The meeting was part of the activity of the Joint European Master Curriculum Development Programme in Quantum Information, Communication, Cryptography and Computation, involving the Universities of Cergy-Pontoise (France), Chania (Greece), Leuven (Belgium), Rennes1 (France) and Trieste (Italy). This special issue of Journal of Physics A: Mathematical and Theoretical collects 22 contributions from well known experts who took part in the workshop. They summarize the present day status of the research in the manifold aspects of quantum information. The issue is opened by two review articles, the first by G Adesso and F Illuminati discussing entanglement in continuous variable systems, the second by T Prosen, discussing chaos and complexity in quantum systems. Both topics have theoretical as well as experimental relevance and are likely to witness a fast growing development in the near future. The remaining contributions present more specific and very recent results. They involve the study of the structure of quantum states and their estimation (B Baumgartner et al, C King et al, S Olivares et al, D Petz et al and W van Dam et al), of entanglement generation and its quantification (G Brida et al, F Ciccarello et al, G Costantini et al, O Romero-Isart et al, D Rossini et al, A Serafini et al and D Vitali et al), of randomness related effects on entanglement behaviour (I Akhalwaya et al, O Dahlsten et al and L Viola et al), and of abstract and applied aspects of quantum computation and communication (K Audenart, G M D'Ariano et al, N Datta et al, L C Kwek et al and M Nathanson et al). We would like to express our gratitude to the European Commission, the Abdus Salam ICTP, SISSA and Eurotech SpA (Amaro, Udine, Italy) for financial and/or logistic support. Special thanks also go to the workshop secretary Marina De Comelli, and the secretaries of the Department of Theoretical Physics, University of Trieste, Sabrina Gaspardis and Rosita Glavina for their precious help and assistance.

  4. Quantum and classical dynamics in adiabatic computation

    NASA Astrophysics Data System (ADS)

    Crowley, P. J. D.; Äńurić, T.; Vinci, W.; Warburton, P. A.; Green, A. G.

    2014-10-01

    Adiabatic transport provides a powerful way to manipulate quantum states. By preparing a system in a readily initialized state and then slowly changing its Hamiltonian, one may achieve quantum states that would otherwise be inaccessible. Moreover, a judicious choice of final Hamiltonian whose ground state encodes the solution to a problem allows adiabatic transport to be used for universal quantum computation. However, the dephasing effects of the environment limit the quantum correlations that an open system can support and degrade the power of such adiabatic computation. We quantify this effect by allowing the system to evolve over a restricted set of quantum states, providing a link between physically inspired classical optimization algorithms and quantum adiabatic optimization. This perspective allows us to develop benchmarks to bound the quantum correlations harnessed by an adiabatic computation. We apply these to the D-Wave Vesuvius machine with revealing—though inconclusive—results.

  5. Application of superconducting quantum interferometer in quantum computer development

    NASA Astrophysics Data System (ADS)

    Golovashkin, A. I.; Karuzskiy, A. L.; Orlikovskiy, A. A.; Privezentsev, V. V.; Tshovrebov, A. M.

    2008-03-01

    Various variants of use high-sensitivity superconducting quantum interferometers (SQUID) in problems closely connected with development of a quantum computer are considered. 1.Hardware realization of a method of definition of midget concentration of the paramagnetic centers, based on measurement of their magnetization SQUID in a mode of modulation microwave saturation of magnetic sublevels is offered. The method will allow make testing of semi-conductor materials necessary for creation of a spin solid-state quantum computer. 2.The opportunity of application SQUID for reading a condition of the quantum register, based on the quantum-statistical mechanism, allowing registered a state of single spin, is considered. 3.The circuit super low noise the quantum electrometer, based on use SQUID is offered as a measuring instrument of magnetization of spin system in which exchange interaction is adjusted by potential on in parallel connected managing electrodes (on type a spin ensemble computer).

  6. Geometry of Quantum Computation with Qudits

    PubMed Central

    Luo, Ming-Xing; Chen, Xiu-Bo; Yang, Yi-Xian; Wang, Xiaojun

    2014-01-01

    The circuit complexity of quantum qubit system evolution as a primitive problem in quantum computation has been discussed widely. We investigate this problem in terms of qudit system. Using the Riemannian geometry the optimal quantum circuits are equivalent to the geodetic evolutions in specially curved parametrization of SU(dn). And the quantum circuit complexity is explicitly dependent of controllable approximation error bound. PMID:24509710

  7. Geometry of quantum computation with qudits.

    PubMed

    Luo, Ming-Xing; Chen, Xiu-Bo; Yang, Yi-Xian; Wang, Xiaojun

    2014-01-01

    The circuit complexity of quantum qubit system evolution as a primitive problem in quantum computation has been discussed widely. We investigate this problem in terms of qudit system. Using the Riemannian geometry the optimal quantum circuits are equivalent to the geodetic evolutions in specially curved parametrization of SU(d(n)). And the quantum circuit complexity is explicitly dependent of controllable approximation error bound. PMID:24509710

  8. Determining Ramsey numbers on a quantum computer

    NASA Astrophysics Data System (ADS)

    Wang, Hefeng

    2016-03-01

    We present a quantum algorithm for computing the Ramsey numbers whose computational complexity grows superexponentially with the number of vertices of a graph on a classical computer. The problem is mapped to a decision problem on a quantum computer, and a probe qubit is coupled to a register that represents the problem and detects the energy levels of the problem Hamiltonian. The decision problem is solved by detecting the decay dynamics of the probe qubit.

  9. Foundations of Quantum Mechanics and Quantum Computation

    NASA Astrophysics Data System (ADS)

    Aspect, Alain; Leggett, Anthony; Preskill, John; Durt, Thomas; Pironio, Stefano

    2013-03-01

    I ask the question: What can we infer about the nature and structure of the physical world (a) from experiments already done to test the predictions of quantum mechanics (b) from the assumption that all future experiments will agree with those predictions? I discuss existing and projected experiments related to the two classic paradoxes of quantum mechanics, named respectively for EPR and Schrdinger's Cat, and show in particular that one natural conclusion from both types of experiment implies the abandonment of the concept of macroscopic counterfactual definiteness.

  10. Protecting software agents from malicious hosts using quantum computing

    NASA Astrophysics Data System (ADS)

    Reisner, John; Donkor, Eric

    2000-07-01

    We evaluate how quantum computing can be applied to security problems for software agents. Agent-based computing, which merges technological advances in artificial intelligence and mobile computing, is a rapidly growing domain, especially in applications such as electronic commerce, network management, information retrieval, and mission planning. System security is one of the more eminent research areas in agent-based computing, and the specific problem of protecting a mobile agent from a potentially hostile host is one of the most difficult of these challenges. In this work, we describe our agent model, and discuss the capabilities and limitations of classical solutions to the malicious host problem. Quantum computing may be extremely helpful in addressing the limitations of classical solutions to this problem. This paper highlights some of the areas where quantum computing could be applied to agent security.

  11. Experimental demonstration of deterministic one-way quantum computation on a NMR quantum computer

    SciTech Connect

    Ju, Chenyong; Zhu Jing; Peng Xinhua; Chong Bo; Zhou Xianyi; Du Jiangfeng

    2010-01-15

    One-way quantum computing is an important and novel approach to quantum computation. By exploiting the existing particle-particle interactions, we report an experimental realization of the complete process of deterministic one-way quantum Deutsch-Josza algorithm in NMR, including graph state preparation, single-qubit measurements, and feed-forward corrections. The findings in our experiment may shed light on the future scalable one-way quantum computation.

  12. Computing technology in the 1980's. [computers

    NASA Technical Reports Server (NTRS)

    Stone, H. S.

    1978-01-01

    Advances in computing technology have been led by consistently improving semiconductor technology. The semiconductor industry has turned out ever faster, smaller, and less expensive devices since transistorized computers were first introduced 20 years ago. For the next decade, there appear to be new advances possible, with the rate of introduction of improved devices at least equal to the historic trends. The implication of these projections is that computers will enter new markets and will truly be pervasive in business, home, and factory as their cost diminishes and their computational power expands to new levels. The computer industry as we know it today will be greatly altered in the next decade, primarily because the raw computer system will give way to computer-based turn-key information and control systems.

  13. Computer Technology in Massachusetts Schools.

    ERIC Educational Resources Information Center

    Hess, John; Sanders, Jean E., Ed.

    This report focuses on the status and future of computer technology in Massachusetts schools. The report is organized into four major sections. Introductory information is provided in section 1, followed by a framework (section 2) for viewing computer technology. This framework provides information on computer hardware components, computer…

  14. Quantum computing and the entanglement frontier

    NASA Astrophysics Data System (ADS)

    Preskill, John

    2013-04-01

    Quantum information science explores the frontier of highly complex quantum states, the ``entanglement frontier.'' This study is motivated by the observation (widely believed but unproven) that classical systems cannot simulate highly entangled quantum systems efficiently, and we hope to hasten the day when well controlled quantum systems can perform tasks surpassing what can be done in the classical world. One way to achieve such ``quantum supremacy'' would be to run an algorithm on a quantum computer which solves a problem with a super-polynomial speedup relative to classical computers, but there may be other ways that can be achieved sooner, such as simulating exotic quantum states of strongly correlated matter. To operate a large scale quantum computer reliably we will need to overcome the debilitating effects of decoherence, which might be done using ``standard'' quantum hardware protected by quantum error-correcting codes, or by exploiting the nonabelian quantum statistics of anyons realized in solid state systems, or by combining both methods. Only by challenging the entanglement frontier will we learn whether Nature provides extravagant resources far beyond what the classical world would allow.

  15. The case for biological quantum computer elements

    NASA Astrophysics Data System (ADS)

    Baer, Wolfgang; Pizzi, Rita

    2009-05-01

    An extension to vonNeumann's analysis of quantum theory suggests self-measurement is a fundamental process of Nature. By mapping the quantum computer to the brain architecture we will argue that the cognitive experience results from a measurement of a quantum memory maintained by biological entities. The insight provided by this mapping suggests quantum effects are not restricted to small atomic and nuclear phenomena but are an integral part of our own cognitive experience and further that the architecture of a quantum computer system parallels that of a conscious brain. We will then review the suggestions for biological quantum elements in basic neural structures and address the de-coherence objection by arguing for a self- measurement event model of Nature. We will argue that to first order approximation the universe is composed of isolated self-measurement events which guaranties coherence. Controlled de-coherence is treated as the input/output interactions between quantum elements of a quantum computer and the quantum memory maintained by biological entities cognizant of the quantum calculation results. Lastly we will present stem-cell based neuron experiments conducted by one of us with the aim of demonstrating the occurrence of quantum effects in living neural networks and discuss future research projects intended to reach this objective.

  16. Relativistic quantum metrology: exploiting relativity to improve quantum measurement technologies.

    PubMed

    Ahmadi, Mehdi; Bruschi, David Edward; Sabn, Carlos; Adesso, Gerardo; Fuentes, Ivette

    2014-01-01

    We present a framework for relativistic quantum metrology that is useful for both Earth-based and space-based technologies. Quantum metrology has been so far successfully applied to design precision instruments such as clocks and sensors which outperform classical devices by exploiting quantum properties. There are advanced plans to implement these and other quantum technologies in space, for instance Space-QUEST and Space Optical Clock projects intend to implement quantum communications and quantum clocks at regimes where relativity starts to kick in. However, typical setups do not take into account the effects of relativity on quantum properties. To include and exploit these effects, we introduce techniques for the application of metrology to quantum field theory. Quantum field theory properly incorporates quantum theory and relativity, in particular, at regimes where space-based experiments take place. This framework allows for high precision estimation of parameters that appear in quantum field theory including proper times and accelerations. Indeed, the techniques can be applied to develop a novel generation of relativistic quantum technologies for gravimeters, clocks and sensors. As an example, we present a high precision device which in principle improves the state-of-the-art in quantum accelerometers by exploiting relativistic effects. PMID:24851858

  17. Relativistic Quantum Metrology: Exploiting relativity to improve quantum measurement technologies

    PubMed Central

    Ahmadi, Mehdi; Bruschi, David Edward; Sabn, Carlos; Adesso, Gerardo; Fuentes, Ivette

    2014-01-01

    We present a framework for relativistic quantum metrology that is useful for both Earth-based and space-based technologies. Quantum metrology has been so far successfully applied to design precision instruments such as clocks and sensors which outperform classical devices by exploiting quantum properties. There are advanced plans to implement these and other quantum technologies in space, for instance Space-QUEST and Space Optical Clock projects intend to implement quantum communications and quantum clocks at regimes where relativity starts to kick in. However, typical setups do not take into account the effects of relativity on quantum properties. To include and exploit these effects, we introduce techniques for the application of metrology to quantum field theory. Quantum field theory properly incorporates quantum theory and relativity, in particular, at regimes where space-based experiments take place. This framework allows for high precision estimation of parameters that appear in quantum field theory including proper times and accelerations. Indeed, the techniques can be applied to develop a novel generation of relativistic quantum technologies for gravimeters, clocks and sensors. As an example, we present a high precision device which in principle improves the state-of-the-art in quantum accelerometers by exploiting relativistic effects. PMID:24851858

  18. Computer Viruses. Technology Update.

    ERIC Educational Resources Information Center

    Ponder, Tim, Comp.; Ropog, Marty, Comp.; Keating, Joseph, Comp.

    This document provides general information on computer viruses, how to help protect a computer network from them, measures to take if a computer becomes infected. Highlights include the origins of computer viruses; virus contraction; a description of some common virus types (File Virus, Boot Sector/Partition Table Viruses, Trojan Horses, and…

  19. Grating chips for quantum technologies

    NASA Astrophysics Data System (ADS)

    McGilligan, James Patrick; Ingleby, Stuart; Griffin, Paul Francis; Riis, Erling; Arnold, Aidan

    2015-05-01

    Laser cooled atomic samples have resulted in profound advances in frequency metrology, however the technology is typically complex and bulky. In the cover story of the May 2013 issue of Nature Nanotechnology we describe a micro-fabricated optical element that greatly facilitates miniaturisation of ultra-cold atom technology. Portable devices should be feasible with accuracy vastly exceeding that of equivalent room-temperature technology, with a minimal footprint. Laser cooled samples will be ideal for measurement devices e.g. portable atomic clocks and magnetometers and, moreover, they hold great potential for longer-term breakthroughs exploiting e.g. optical lattices for all-optical clocks and Bose-Einstein condensates for atom interferometry. Here we will discuss next generation diffractive optical elements (DOE) and demonstrate quantum based measurements on samples of ultra-cold atoms created using our miniaturised optical setup.

  20. Video Encryption and Decryption on Quantum Computers

    NASA Astrophysics Data System (ADS)

    Yan, Fei; Iliyasu, Abdullah M.; Venegas-Andraca, Salvador E.; Yang, Huamin

    2015-08-01

    A method for video encryption and decryption on quantum computers is proposed based on color information transformations on each frame encoding the content of the encoding the content of the video. The proposed method provides a flexible operation to encrypt quantum video by means of the quantum measurement in order to enhance the security of the video. To validate the proposed approach, a tetris tile-matching puzzle game video is utilized in the experimental simulations. The results obtained suggest that the proposed method enhances the security and speed of quantum video encryption and decryption, both properties required for secure transmission and sharing of video content in quantum communication.

  1. Computer Technology and Nursing Education.

    ERIC Educational Resources Information Center

    Southern Council on Collegiate Education for Nursing, Atlanta, GA.

    The influences of computer technology on college nursing education programs and health care delivery systems are discussed in eight papers. The use of computers is considered, with attention to clinical care, nursing education and continuing education, administration, and research. Attention is also directed to basic computer terminology, computer

  2. Exponential rise of dynamical complexity in quantum computing through projections

    NASA Astrophysics Data System (ADS)

    Burgarth, Daniel Klaus; Facchi, Paolo; Giovannetti, Vittorio; Nakazato, Hiromichi; Pascazio, Saverio; Yuasa, Kazuya

    2014-10-01

    The ability of quantum systems to host exponentially complex dynamics has the potential to revolutionize science and technology. Therefore, much effort has been devoted to developing of protocols for computation, communication and metrology, which exploit this scaling, despite formidable technical difficulties. Here we show that the mere frequent observation of a small part of a quantum system can turn its dynamics from a very simple one into an exponentially complex one, capable of universal quantum computation. After discussing examples, we go on to show that this effect is generally to be expected: almost any quantum dynamics becomes universal once ‘observed’ as outlined above. Conversely, we show that any complex quantum dynamics can be ‘purified’ into a simpler one in larger dimensions. We conclude by demonstrating that even local noise can lead to an exponentially complex dynamics.

  3. Exponential rise of dynamical complexity in quantum computing through projections.

    PubMed

    Burgarth, Daniel Klaus; Facchi, Paolo; Giovannetti, Vittorio; Nakazato, Hiromichi; Pascazio, Saverio; Yuasa, Kazuya

    2014-01-01

    The ability of quantum systems to host exponentially complex dynamics has the potential to revolutionize science and technology. Therefore, much effort has been devoted to developing of protocols for computation, communication and metrology, which exploit this scaling, despite formidable technical difficulties. Here we show that the mere frequent observation of a small part of a quantum system can turn its dynamics from a very simple one into an exponentially complex one, capable of universal quantum computation. After discussing examples, we go on to show that this effect is generally to be expected: almost any quantum dynamics becomes universal once 'observed' as outlined above. Conversely, we show that any complex quantum dynamics can be 'purified' into a simpler one in larger dimensions. We conclude by demonstrating that even local noise can lead to an exponentially complex dynamics. PMID:25300692

  4. Exponential rise of dynamical complexity in quantum computing through projections

    PubMed Central

    Burgarth, Daniel Klaus; Facchi, Paolo; Giovannetti, Vittorio; Nakazato, Hiromichi; Pascazio, Saverio; Yuasa, Kazuya

    2014-01-01

    The ability of quantum systems to host exponentially complex dynamics has the potential to revolutionize science and technology. Therefore, much effort has been devoted to developing of protocols for computation, communication and metrology, which exploit this scaling, despite formidable technical difficulties. Here we show that the mere frequent observation of a small part of a quantum system can turn its dynamics from a very simple one into an exponentially complex one, capable of universal quantum computation. After discussing examples, we go on to show that this effect is generally to be expected: almost any quantum dynamics becomes universal once observed as outlined above. Conversely, we show that any complex quantum dynamics can be purified into a simpler one in larger dimensions. We conclude by demonstrating that even local noise can lead to an exponentially complex dynamics. PMID:25300692

  5. Magnetic resonance force microscopy quantum computer with tellurium donors in silicon.

    PubMed

    Berman, G P; Doolen, G D; Hammel, P C; Tsifrinovich, V I

    2001-03-26

    We propose a magnetic resonance force microscopy (MRFM)-based nuclear spin quantum computer using tellurium impurities in silicon. This approach to quantum computing combines well-developed silicon technology and expected advances in MRFM. Our proposal does not use electrostatic gates to realize quantum logic operations. PMID:11290066

  6. Blind quantum computation protocol in which Alice only makes measurements

    NASA Astrophysics Data System (ADS)

    Morimae, Tomoyuki; Fujii, Keisuke

    2013-05-01

    Blind quantum computation is a new secure quantum computing protocol which enables Alice (who does not have sufficient quantum technology) to delegate her quantum computation to Bob (who has a full-fledged quantum computer) in such a way that Bob cannot learn anything about Alice's input, output, and algorithm. In previous protocols, Alice needs to have a device which generates quantum states, such as single-photon states. Here we propose another type of blind computing protocol where Alice does only measurements, such as the polarization measurements with a threshold detector. In several experimental setups, such as optical systems, the measurement of a state is much easier than the generation of a single-qubit state. Therefore our protocols ease Alice's burden. Furthermore, the security of our protocol is based on the no-signaling principle, which is more fundamental than quantum physics. Finally, our protocols are device independent in the sense that Alice does not need to trust her measurement device in order to guarantee the security.

  7. Effective pure states for bulk quantum computation

    SciTech Connect

    Knill, E.; Chuang, I.; Laflamme, R.

    1997-11-01

    In bulk quantum computation one can manipulate a large number of indistinguishable quantum computers by parallel unitary operations and measure expectation values of certain observables with limited sensitivity. The initial state of each computer in the ensemble is known but not pure. Methods for obtaining effective pure input states by a series of manipulations have been described by Gershenfeld and Chuang (logical labeling) and Corey et al. (spatial averaging) for the case of quantum computation with nuclear magnetic resonance. We give a different technique called temporal averaging. This method is based on classical randomization, requires no ancilla qubits and can be implemented in nuclear magnetic resonance without using gradient fields. We introduce several temporal averaging algorithms suitable for both high temperature and low temperature bulk quantum computing and analyze the signal to noise behavior of each.

  8. Concatenated codes for fault tolerant quantum computing

    SciTech Connect

    Knill, E.; Laflamme, R.; Zurek, W.

    1995-05-01

    The application of concatenated codes to fault tolerant quantum computing is discussed. We have previously shown that for quantum memories and quantum communication, a state can be transmitted with error {epsilon} provided each gate has error at most c{epsilon}. We show how this can be used with Shor`s fault tolerant operations to reduce the accuracy requirements when maintaining states not currently participating in the computation. Viewing Shor`s fault tolerant operations as a method for reducing the error of operations, we give a concatenated implementation which promises to propagate the reduction hierarchically. This has the potential of reducing the accuracy requirements in long computations.

  9. Analysis of an Atom-Optical Architecture for Quantum Computation

    NASA Astrophysics Data System (ADS)

    Devitt, Simon J.; Stephens, Ashley M.; Munro, William J.; Nemoto, Kae

    Quantum technology based on photons has emerged as one of the most promising platforms for quantum information processing, having already been used in proof-of-principle demonstrations of quantum communication and quantum computation. However, the scalability of this technology depends on the successful integration of experimentally feasible devices in an architecture that tolerates realistic errors and imperfections. Here, we analyse an atom-optical architecture for quantum computation designed to meet the requirements of scalability. The architecture is based on a modular atom-cavity device that provides an effective photon-photon interaction, allowing for the rapid, deterministic preparation of a large class of entangled states. We begin our analysis at the physical level, where we outline the experimental cavity quantum electrodynamics requirements of the basic device. Then, we describe how a scalable network of these devices can be used to prepare a three-dimensional topological cluster state, sufficient for universal fault-tolerant quantum computation. We conclude at the application level, where we estimate the system-level requirements of the architecture executing an algorithm compiled for compatibility with the topological cluster state.

  10. Hyper-parallel photonic quantum computation with coupled quantum dots.

    PubMed

    Ren, Bao-Cang; Deng, Fu-Guo

    2014-01-01

    It is well known that a parallel quantum computer is more powerful than a classical one. So far, there are some important works about the construction of universal quantum logic gates, the key elements in quantum computation. However, they are focused on operating on one degree of freedom (DOF) of quantum systems. Here, we investigate the possibility of achieving scalable hyper-parallel quantum computation based on two DOFs of photon systems. We construct a deterministic hyper-controlled-not (hyper-CNOT) gate operating on both the spatial-mode and the polarization DOFs of a two-photon system simultaneously, by exploiting the giant optical circular birefringence induced by quantum-dot spins in double-sided optical microcavities as a result of cavity quantum electrodynamics (QED). This hyper-CNOT gate is implemented by manipulating the four qubits in the two DOFs of a two-photon system without auxiliary spatial modes or polarization modes. It reduces the operation time and the resources consumed in quantum information processing, and it is more robust against the photonic dissipation noise, compared with the integration of several cascaded CNOT gates in one DOF. PMID:24721781

  11. Hyper-parallel photonic quantum computation with coupled quantum dots

    PubMed Central

    Ren, Bao-Cang; Deng, Fu-Guo

    2014-01-01

    It is well known that a parallel quantum computer is more powerful than a classical one. So far, there are some important works about the construction of universal quantum logic gates, the key elements in quantum computation. However, they are focused on operating on one degree of freedom (DOF) of quantum systems. Here, we investigate the possibility of achieving scalable hyper-parallel quantum computation based on two DOFs of photon systems. We construct a deterministic hyper-controlled-not (hyper-CNOT) gate operating on both the spatial-mode and the polarization DOFs of a two-photon system simultaneously, by exploiting the giant optical circular birefringence induced by quantum-dot spins in double-sided optical microcavities as a result of cavity quantum electrodynamics (QED). This hyper-CNOT gate is implemented by manipulating the four qubits in the two DOFs of a two-photon system without auxiliary spatial modes or polarization modes. It reduces the operation time and the resources consumed in quantum information processing, and it is more robust against the photonic dissipation noise, compared with the integration of several cascaded CNOT gates in one DOF. PMID:24721781

  12. Quantum computers on multiatomic ensembles in quantum electrodynamic cavity

    NASA Astrophysics Data System (ADS)

    Andrianov, S. N.; Moiseev, S. A.

    2012-03-01

    Schemes for the construction of quantum computers on multiatomic ensembles in quantum electrodynamic cavity are considered. With that, both encoding of physical qubits on each separate multiatomic ensemble and logical encoding of qubits on the pairs of ensembles are introduced. Possible constructions of swapping ( SWAP, sqrt {SWAP} ) and controlled swapping gates ( CSWAP) are analyzed. Mechanism of collective blockade and dynamical elimination procedure are proposed for realization of these gates. The comparison of the scheme solutions is carried out for the construction of quantum computer at using of physical and logical qubits.

  13. One-way quantum computation with circuit quantum electrodynamics

    SciTech Connect

    Wu Chunwang; Han Yang; Chen Pingxing; Li Chengzu; Zhong Xiaojun

    2010-03-15

    In this Brief Report, we propose a potential scheme to implement one-way quantum computation with circuit quantum electrodynamics (QED). Large cluster states of charge qubits can be generated in just one step with a superconducting transmission line resonator (TLR) playing the role of a dispersive coupler. A single-qubit measurement in the arbitrary basis can be implemented using a single electron transistor with the help of one-qubit gates. By examining the main decoherence sources, we show that circuit QED is a promising architecture for one-way quantum computation.

  14. Hamiltonian models of quantum computers which evolve quantum ballistically

    SciTech Connect

    Benioff, P.

    1996-12-31

    Quantum computation is a subject of much recent interest. In much of the work in the literature quantum computers are described as built up from a sequence of unitary operators where each unitary operator carries out a stage of the overall quantum computation. The sequence and connection of the different unitary operators is provided presumably by some external agent which governs the overall process. However there is no description of a an overall Hamiltonian needed to give the actual quantum dynamics of the computation process. In this talk, earlier work by the author is followed in that simple, time independent Hamiltonians are used to describe quantum computation, and the Schroedinger evolution of the computation system is considered to be quantum ballistic. However, the definition of quantum ballistic evolution used here is more general than that used in the earlier work. In particular, the requirement that the step operator {ital T} associated with a process be a partial isometry, used in, is relaxed to require that {ital T} be a contraction operator. (An operator {ital T} is a partial isometry if the self-adjoint operators T{sup {dagger}}T and TT{sup {dagger}} are also projection operators.{ital T} is a contraction operator if {vert_bar}{vert_bar} {ital T} {vert_bar}{vert_bar} {<=} 1.) The main purpose of this talk is to investigate some consequences for quantum computation under this weaker requirement. It will be seen that system motion along discrete paths in a basis still occurs. However the motion occurs in ,the presence of potentials whose height and distribution along the path depends on {ital T} and the path states.

  15. Materials Frontiers to Empower Quantum Computing

    SciTech Connect

    Taylor, Antoinette Jane; Sarrao, John Louis; Richardson, Christopher

    2015-06-11

    This is an exciting time at the nexus of quantum computing and materials research. The materials frontiers described in this report represent a significant advance in electronic materials and our understanding of the interactions between the local material and a manufactured quantum state. Simultaneously, directed efforts to solve materials issues related to quantum computing provide an opportunity to control and probe the fundamental arrangement of matter that will impact all electronic materials. An opportunity exists to extend our understanding of materials functionality from electronic-grade to quantum-grade by achieving a predictive understanding of noise and decoherence in qubits and their origins in materials defects and environmental coupling. Realizing this vision systematically and predictively will be transformative for quantum computing and will represent a qualitative step forward in materials prediction and control.

  16. Faster quantum chemistry simulation on fault-tolerant quantum computers

    NASA Astrophysics Data System (ADS)

    Cody Jones, N.; Whitfield, James D.; McMahon, Peter L.; Yung, Man-Hong; Van Meter, Rodney; Aspuru-Guzik, Aln; Yamamoto, Yoshihisa

    2012-11-01

    Quantum computers can in principle simulate quantum physics exponentially faster than their classical counterparts, but some technical hurdles remain. We propose methods which substantially improve the performance of a particular form of simulation, ab initio quantum chemistry, on fault-tolerant quantum computers; these methods generalize readily to other quantum simulation problems. Quantum teleportation plays a key role in these improvements and is used extensively as a computing resource. To improve execution time, we examine techniques for constructing arbitrary gates which perform substantially faster than circuits based on the conventional Solovay-Kitaev algorithm (Dawson and Nielsen 2006 Quantum Inform. Comput. 6 81). For a given approximation error ?, arbitrary single-qubit gates can be produced fault-tolerantly and using a restricted set of gates in time which is O(log??) or O(log?log??) with sufficient parallel preparation of ancillas, constant average depth is possible using a method we call programmable ancilla rotations. Moreover, we construct and analyze efficient implementations of first- and second-quantized simulation algorithms using the fault-tolerant arbitrary gates and other techniques, such as implementing various subroutines in constant time. A specific example we analyze is the ground-state energy calculation for lithium hydride.

  17. Superadiabatic Controlled Evolutions and Universal Quantum Computation

    NASA Astrophysics Data System (ADS)

    Santos, Alan C.; Sarandy, Marcelo S.

    2015-10-01

    Adiabatic state engineering is a powerful technique in quantum information and quantum control. However, its performance is limited by the adiabatic theorem of quantum mechanics. In this scenario, shortcuts to adiabaticity, such as provided by the superadiabatic theory, constitute a valuable tool to speed up the adiabatic quantum behavior. Here, we propose a superadiabatic route to implement universal quantum computation. Our method is based on the realization of piecewise controlled superadiabatic evolutions. Remarkably, they can be obtained by simple time-independent counter-diabatic Hamiltonians. In particular, we discuss the implementation of fast rotation gates and arbitrary n-qubit controlled gates, which can be used to design different sets of universal quantum gates. Concerning the energy cost of the superadiabatic implementation, we show that it is dictated by the quantum speed limit, providing an upper bound for the corresponding adiabatic counterparts.

  18. Image segmentation on a quantum computer

    NASA Astrophysics Data System (ADS)

    Caraiman, Simona; Manta, Vasile I.

    2015-05-01

    In this paper, we address the field of quantum information processing and analyze the prospects of applying quantum computation concepts to image processing tasks. Specifically, we discuss the development of a quantum version for the image segmentation operation. This is an important technique that comes up in many image processing applications. We consider the threshold-based segmentation and show that a quantum circuit to achieve this operation can be built using a quantum oracle that implements the thresholding function. We discuss the circuit implementation of the oracle operator and provide examples of segmenting synthetic and real images. The main advantage of the quantum version for image segmentation over the classical approach is its speedup and is provided by the special properties of quantum information processing: superposition of states and inherent parallelism.

  19. Superadiabatic Controlled Evolutions and Universal Quantum Computation

    PubMed Central

    Santos, Alan C.; Sarandy, Marcelo S.

    2015-01-01

    Adiabatic state engineering is a powerful technique in quantum information and quantum control. However, its performance is limited by the adiabatic theorem of quantum mechanics. In this scenario, shortcuts to adiabaticity, such as provided by the superadiabatic theory, constitute a valuable tool to speed up the adiabatic quantum behavior. Here, we propose a superadiabatic route to implement universal quantum computation. Our method is based on the realization of piecewise controlled superadiabatic evolutions. Remarkably, they can be obtained by simple time-independent counter-diabatic Hamiltonians. In particular, we discuss the implementation of fast rotation gates and arbitrary n-qubit controlled gates, which can be used to design different sets of universal quantum gates. Concerning the energy cost of the superadiabatic implementation, we show that it is dictated by the quantum speed limit, providing an upper bound for the corresponding adiabatic counterparts. PMID:26511064

  20. Superadiabatic Controlled Evolutions and Universal Quantum Computation.

    PubMed

    Santos, Alan C; Sarandy, Marcelo S

    2015-01-01

    Adiabatic state engineering is a powerful technique in quantum information and quantum control. However, its performance is limited by the adiabatic theorem of quantum mechanics. In this scenario, shortcuts to adiabaticity, such as provided by the superadiabatic theory, constitute a valuable tool to speed up the adiabatic quantum behavior. Here, we propose a superadiabatic route to implement universal quantum computation. Our method is based on the realization of piecewise controlled superadiabatic evolutions. Remarkably, they can be obtained by simple time-independent counter-diabatic Hamiltonians. In particular, we discuss the implementation of fast rotation gates and arbitrary n-qubit controlled gates, which can be used to design different sets of universal quantum gates. Concerning the energy cost of the superadiabatic implementation, we show that it is dictated by the quantum speed limit, providing an upper bound for the corresponding adiabatic counterparts. PMID:26511064

  1. From transistor to trapped-ion computers for quantum chemistry.

    PubMed

    Yung, M-H; Casanova, J; Mezzacapo, A; McClean, J; Lamata, L; Aspuru-Guzik, A; Solano, E

    2014-01-01

    Over the last few decades, quantum chemistry has progressed through the development of computational methods based on modern digital computers. However, these methods can hardly fulfill the exponentially-growing resource requirements when applied to large quantum systems. As pointed out by Feynman, this restriction is intrinsic to all computational models based on classical physics. Recently, the rapid advancement of trapped-ion technologies has opened new possibilities for quantum control and quantum simulations. Here, we present an efficient toolkit that exploits both the internal and motional degrees of freedom of trapped ions for solving problems in quantum chemistry, including molecular electronic structure, molecular dynamics, and vibronic coupling. We focus on applications that go beyond the capacity of classical computers, but may be realizable on state-of-the-art trapped-ion systems. These results allow us to envision a new paradigm of quantum chemistry that shifts from the current transistor to a near-future trapped-ion-based technology. PMID:24395054

  2. [Earth Science Technology Office's Computational Technologies Project

    NASA Technical Reports Server (NTRS)

    Fischer, James (Technical Monitor); Merkey, Phillip

    2005-01-01

    This grant supported the effort to characterize the problem domain of the Earth Science Technology Office's Computational Technologies Project, to engage the Beowulf Cluster Computing Community as well as the High Performance Computing Research Community so that we can predict the applicability of said technologies to the scientific community represented by the CT project and formulate long term strategies to provide the computational resources necessary to attain the anticipated scientific objectives of the CT project. Specifically, the goal of the evaluation effort is to use the information gathered over the course of the Round-3 investigations to quantify the trends in scientific expectations, the algorithmic requirements and capabilities of high-performance computers to satisfy this anticipated need.

  3. Reducing computational complexity of quantum correlations

    NASA Astrophysics Data System (ADS)

    Chanda, Titas; Das, Tamoghna; Sadhukhan, Debasis; Pal, Amit Kumar; SenDe, Aditi; Sen, Ujjwal

    2015-12-01

    We address the issue of reducing the resource required to compute information-theoretic quantum correlation measures such as quantum discord and quantum work deficit in two qubits and higher-dimensional systems. We show that determination of the quantum correlation measure is possible even if we utilize a restricted set of local measurements. We find that the determination allows us to obtain a closed form of quantum discord and quantum work deficit for several classes of states, with a low error. We show that the computational error caused by the constraint over the complete set of local measurements reduces fast with an increase in the size of the restricted set, implying usefulness of constrained optimization, especially with the increase of dimensions. We perform quantitative analysis to investigate how the error scales with the system size, taking into account a set of plausible constructions of the constrained set. Carrying out a comparative study, we show that the resource required to optimize quantum work deficit is usually higher than that required for quantum discord. We also demonstrate that minimization of quantum discord and quantum work deficit is easier in the case of two-qubit mixed states of fixed ranks and with positive partial transpose in comparison to the corresponding states having nonpositive partial transpose. Applying the methodology to quantum spin models, we show that the constrained optimization can be used with advantage in analyzing such systems in quantum information-theoretic language. For bound entangled states, we show that the error is significantly low when the measurements correspond to the spin observables along the three Cartesian coordinates, and thereby we obtain expressions of quantum discord and quantum work deficit for these bound entangled states.

  4. Is the Brain a Quantum Computer?

    ERIC Educational Resources Information Center

    Litt, Abninder; Eliasmith, Chris; Kroon, Frederick W.; Weinstein, Steven; Thagard, Paul

    2006-01-01

    We argue that computation via quantum mechanical processes is irrelevant to explaining how brains produce thought, contrary to the ongoing speculations of many theorists. First, quantum effects do not have the temporal properties required for neural information processing. Second, there are substantial physical obstacles to any organic

  5. Is the Brain a Quantum Computer?

    ERIC Educational Resources Information Center

    Litt, Abninder; Eliasmith, Chris; Kroon, Frederick W.; Weinstein, Steven; Thagard, Paul

    2006-01-01

    We argue that computation via quantum mechanical processes is irrelevant to explaining how brains produce thought, contrary to the ongoing speculations of many theorists. First, quantum effects do not have the temporal properties required for neural information processing. Second, there are substantial physical obstacles to any organic…

  6. Algorithms Bridging Quantum Computation and Chemistry

    NASA Astrophysics Data System (ADS)

    McClean, Jarrod Ryan

    The design of new materials and chemicals derived entirely from computation has long been a goal of computational chemistry, and the governing equation whose solution would permit this dream is known. Unfortunately, the exact solution to this equation has been far too expensive and clever approximations fail in critical situations. Quantum computers offer a novel solution to this problem. In this work, we develop not only new algorithms to use quantum computers to study hard problems in chemistry, but also explore how such algorithms can help us to better understand and improve our traditional approaches. In particular, we first introduce a new method, the variational quantum eigensolver, which is designed to maximally utilize the quantum resources available in a device to solve chemical problems. We apply this method in a real quantum photonic device in the lab to study the dissociation of the helium hydride (HeH+) molecule. We also enhance this methodology with architecture specific optimizations on ion trap computers and show how linear-scaling techniques from traditional quantum chemistry can be used to improve the outlook of similar algorithms on quantum computers. We then show how studying quantum algorithms such as these can be used to understand and enhance the development of classical algorithms. In particular we use a tool from adiabatic quantum computation, Feynman's Clock, to develop a new discrete time variational principle and further establish a connection between real-time quantum dynamics and ground state eigenvalue problems. We use these tools to develop two novel parallel-in-time quantum algorithms that outperform competitive algorithms as well as offer new insights into the connection between the fermion sign problem of ground states and the dynamical sign problem of quantum dynamics. Finally we use insights gained in the study of quantum circuits to explore a general notion of sparsity in many-body quantum systems. In particular we use developments from the field of compressed sensing to find compact representations of ground states. As an application we study electronic systems and find solutions dramatically more compact than traditional configuration interaction expansions, offering hope to extend this methodology to challenging systems in chemical and material design.

  7. Iterated Gate Teleportation and Blind Quantum Computation

    NASA Astrophysics Data System (ADS)

    Prez-Delgado, Carlos A.; Fitzsimons, Joseph F.

    2015-06-01

    Blind quantum computation allows a user to delegate a computation to an untrusted server while keeping the computation hidden. A number of recent works have sought to establish bounds on the communication requirements necessary to implement blind computation, and a bound based on the no-programming theorem of Nielsen and Chuang has emerged as a natural limiting factor. Here we show that this constraint only holds in limited scenarios, and show how to overcome it using a novel method of iterated gate teleportations. This technique enables drastic reductions in the communication required for distributed quantum protocols, extending beyond the blind computation setting. Applied to blind quantum computation, this technique offers significant efficiency improvements, and in some scenarios offers an exponential reduction in communication requirements.

  8. Iterated Gate Teleportation and Blind Quantum Computation.

    PubMed

    Prez-Delgado, Carlos A; Fitzsimons, Joseph F

    2015-06-01

    Blind quantum computation allows a user to delegate a computation to an untrusted server while keeping the computation hidden. A number of recent works have sought to establish bounds on the communication requirements necessary to implement blind computation, and a bound based on the no-programming theorem of Nielsen and Chuang has emerged as a natural limiting factor. Here we show that this constraint only holds in limited scenarios, and show how to overcome it using a novel method of iterated gate teleportations. This technique enables drastic reductions in the communication required for distributed quantum protocols, extending beyond the blind computation setting. Applied to blind quantum computation, this technique offers significant efficiency improvements, and in some scenarios offers an exponential reduction in communication requirements. PMID:26196609

  9. LDRD final report on quantum computing using interacting semiconductor quantum wires.

    SciTech Connect

    Lyo, Sungkwun Kenneth; Dunn, Roberto G.; Lilly, Michael Patrick; Tibbetts, Denise R. ); Stephenson, Larry L.; Seamons, John Andrew; Reno, John Louis; Bielejec, Edward Salvador; Simmons, Jerry Alvon

    2006-01-01

    For several years now quantum computing has been viewed as a new paradigm for certain computing applications. Of particular importance to this burgeoning field is the development of an algorithm for factoring large numbers which obviously has deep implications for cryptography and national security. Implementation of these theoretical ideas faces extraordinary challenges in preparing and manipulating quantum states. The quantum transport group at Sandia has demonstrated world-leading, unique double quantum wires devices where we have unprecedented control over the coupling strength, number of 1 D channels, overlap and interaction strength in this nanoelectronic system. In this project, we study 1D-1D tunneling with the ultimate aim of preparing and detecting quantum states of the coupled wires. In a region of strong tunneling, electrons can coherently oscillate from one wire to the other. By controlling the velocity of the electrons, length of the coupling region and tunneling strength we will attempt to observe tunneling oscillations. This first step is critical for further development double quantum wires into the basic building block for a quantum computer, and indeed for other coupled nanoelectronic devices that will rely on coherent transport. If successful, this project will have important implications for nanoelectronics, quantum computing and information technology.

  10. Noise thresholds for optical quantum computers.

    PubMed

    Dawson, Christopher M; Haselgrove, Henry L; Nielsen, Michael A

    2006-01-20

    In this Letter we numerically investigate the fault-tolerant threshold for optical cluster-state quantum computing. We allow both photon loss noise and depolarizing noise (as a general proxy for all local noise), and obtain a threshold region of allowed pairs of values for the two types of noise. Roughly speaking, our results show that scalable optical quantum computing is possible for photon loss probabilities <3 x 10(-3), and for depolarization probabilities <10(-4). PMID:16486553

  11. Braid group representation on quantum computation

    NASA Astrophysics Data System (ADS)

    Aziz, Ryan Kasyfil; Muchtadi-Alamsyah, Intan

    2015-09-01

    There are many studies about topological representation of quantum computation recently. One of diagram representation of quantum computation is by using ZX-Calculus. In this paper we will make a diagrammatical scheme of Dense Coding. We also proved that ZX-Calculus diagram of maximally entangle state satisfies Yang-Baxter Equation and therefore, we can construct a Braid Group representation of set of maximally entangle state.

  12. Computer Technology for Industry.

    ERIC Educational Resources Information Center

    Aviation/Space, 1982

    1982-01-01

    A special National Aeronautics and Space Administration (NASA) service is contributing to national productivity by providing industry with reusable, low-cost, government-developed computer programs. Located at the University of Georgia, NASA's Computer Software Management and Information Center (COSMIC) has developed programs for equipment

  13. Quantum Computation by Optically Coupled Steady Atoms/Quantum-Dots Inside a Quantum Cavity

    NASA Technical Reports Server (NTRS)

    Pradhan, P.; Wang, K. L.; Roychowdhury, V. P.; Anantram, M. P.; Mor, T.; Saini, Subhash (Technical Monitor)

    1999-01-01

    We present a model for quantum computation using $n$ steady 3-level atoms kept inside a quantum cavity, or using $n$ quantum-dots (QDs) kept inside a quantum cavity. In this model one external laser is pointed towards all the atoms/QDs, and $n$ pairs of electrodes are addressing the atoms/QDs, so that each atom is addressed by one pair. The energy levels of each atom/QD are controlled by an external Stark field given to the atom/QD by its external pair of electrodes. Transition between two energy levels of an individual atom/ QD are controlled by the voltage on its electrodes, and by the external laser. Interactions between two atoms/ QDs are performed with the additional help of the cavity mode (using on-resonance condition). Laser frequency, cavity frequency, and energy levels are far off-resonance most of the time, and they are brought to the resonance (using the Stark effect) only at the time of operations. Steps for a controlled-NOT gate between any two atoms/QDs have been described for this model. Our model demands some challenging technological efforts, such as manufacturing single-electron QDs inside a cavity. However, it promises big advantages over other existing models which are currently implemented, and might enable a much easier scale-up, to compute with many more qubits.

  14. Acausal measurement-based quantum computing

    NASA Astrophysics Data System (ADS)

    Morimae, Tomoyuki

    2014-07-01

    In measurement-based quantum computing, there is a natural "causal cone" among qubits of the resource state, since the measurement angle on a qubit has to depend on previous measurement results in order to correct the effect of by-product operators. If we respect the no-signaling principle, by-product operators cannot be avoided. Here we study the possibility of acausal measurement-based quantum computing by using the process matrix framework [Oreshkov, Costa, and Brukner, Nat. Commun. 3, 1092 (2012), 10.1038/ncomms2076]. We construct a resource process matrix for acausal measurement-based quantum computing restricting local operations to projective measurements. The resource process matrix is an analog of the resource state of the standard causal measurement-based quantum computing. We find that if we restrict local operations to projective measurements the resource process matrix is (up to a normalization factor and trivial ancilla qubits) equivalent to the decorated graph state created from the graph state of the corresponding causal measurement-based quantum computing. We also show that it is possible to consider a causal game whose causal inequality is violated by acausal measurement-based quantum computing.

  15. EDITORIAL: Quantum Computing and the Feynman Festival

    NASA Astrophysics Data System (ADS)

    Brandt, Howard E.; Kim, Young S.; Man'ko, Margarita A.

    2003-12-01

    The Feynman Festival is a new interdisciplinary conference developed for studying Richard Feynman and his physics. The first meeting of this new conference series was held at the University of Maryland on 23--28 August 2002 (http://www.physics.umd.edu/robot/feynman.html) and the second meeting is scheduled for August 2004 at the same venue. According to Feynman, the different aspects of nature are different aspects of the same thing. Therefore, the ultimate purpose of the conference is to find Feynman's same thing from all different theories. For this reason, the first meeting of the Festival did not begin with a fixed formula, but composed its scientific programme based on responses from the entire physics community. The conference drew the most enthusiastic response from the community of quantum computing, the field initiated by Feynman. Encouraged by the response, we decided to edit a special issue of Journal of Optics B: Quantum and Semiclassical Optics on quantum computing in connection with the first Feynman Festival. The authorship is not restricted to the participants of the Feynman Festival, and all interested parties were encouraged to submit their papers on this subject. Needless to say, all the papers were peer reviewed according to the well-established standards of the journal. The subject of quantum computing is not restricted to building and operating computers. It requires a deeper understanding of how quantum mechanics works in materials as well as in our minds. Indeed, it covers the basic foundations of quantum mechanics, measurement theory, information theory, quantum optics, atomic physics and condensed matter physics. It may be necessary to develop new mathematical tools to accommodate the language that nature speaks. It is gratifying to note that this special issue contains papers covering all these aspects of quantum computing. As Feynman noted, we could be discussing these diversified issues to study one problem. In our case, this `one problem' is to build quantum computers.

  16. Computers, Technology, and Disability. [Update.

    ERIC Educational Resources Information Center

    American Council on Education, Washington, DC. HEATH Resource Center.

    This paper describes programs and resources that focus on access of postsecondary students with disabilities to computers and other forms of technology. Increased access to technological devices and services is provided to students with disabilities under the Technology-Related Assistance for Individuals with Disabilities Act (Tech Act). Section…

  17. Waveguide-QED-based photonic quantum computation.

    PubMed

    Zheng, Huaixiu; Gauthier, Daniel J; Baranger, Harold U

    2013-08-30

    We propose a new scheme for quantum computation using flying qubits--propagating photons in a one-dimensional waveguide interacting with matter qubits. Photon-photon interactions are mediated by the coupling to a four-level system, based on which photon-photon ?-phase gates (CONTROLLED-NOT) can be implemented for universal quantum computation. We show that high gate fidelity is possible, given recent dramatic experimental progress in superconducting circuits and photonic-crystal waveguides. The proposed system can be an important building block for future on-chip quantum networks. PMID:24033010

  18. Hamiltonian quantum computer in one dimension

    NASA Astrophysics Data System (ADS)

    Wei, Tzu-Chieh; Liang, John C.

    2015-12-01

    Quantum computation can be achieved by preparing an appropriate initial product state of qudits and then letting it evolve under a fixed Hamiltonian. The readout is made by measurement on individual qudits at some later time. This approach is called the Hamiltonian quantum computation and it includes, for example, the continuous-time quantum cellular automata and the universal quantum walk. We consider one spatial dimension and study the compromise between the locality k and the local Hilbert space dimension d . For geometrically 2-local (i.e., k =2 ), it is known that d =8 is already sufficient for universal quantum computation but the Hamiltonian is not translationally invariant. As the locality k increases, it is expected that the minimum required d should decrease. We provide a construction of a Hamiltonian quantum computer for k =3 with d =5 . One implication is that simulating one-dimensional chains of spin-2 particles is BQP-complete (BQP denotes "bounded error, quantum polynomial time"). Imposing translation invariance will increase the required d . For this we also construct another 3-local (k =3 ) Hamiltonian that is invariant under translation of a unit cell of two sites but that requires d to be 8.

  19. Simulating physical phenomena with a quantum computer

    NASA Astrophysics Data System (ADS)

    Ortiz, Gerardo

    2003-03-01

    In a keynote speech at MIT in 1981 Richard Feynman raised some provocative questions in connection to the exact simulation of physical systems using a special device named a ``quantum computer'' (QC). At the time it was known that deterministic simulations of quantum phenomena in classical computers required a number of resources that scaled exponentially with the number of degrees of freedom, and also that the probabilistic simulation of certain quantum problems were limited by the so-called sign or phase problem, a problem believed to be of exponential complexity. Such a QC was intended to mimick physical processes exactly the same as Nature. Certainly, remarks coming from such an influential figure generated widespread interest in these ideas, and today after 21 years there are still some open questions. What kind of physical phenomena can be simulated with a QC?, How?, and What are its limitations? Addressing and attempting to answer these questions is what this talk is about. Definitively, the goal of physics simulation using controllable quantum systems (``physics imitation'') is to exploit quantum laws to advantage, and thus accomplish efficient imitation. Fundamental is the connection between a quantum computational model and a physical system by transformations of operator algebras. This concept is a necessary one because in Quantum Mechanics each physical system is naturally associated with a language of operators and thus can be considered as a possible model of quantum computation. The remarkable result is that an arbitrary physical system is naturally simulatable by another physical system (or QC) whenever a ``dictionary'' between the two operator algebras exists. I will explain these concepts and address some of Feynman's concerns regarding the simulation of fermionic systems. Finally, I will illustrate the main ideas by imitating simple physical phenomena borrowed from condensed matter physics using quantum algorithms, and present experimental quantum simulations performed in a liquid NMR QC.

  20. Simulating fermions on a quantum computer

    NASA Astrophysics Data System (ADS)

    Ortiz, G.; Gubernatis, J. E.; Knill, E.; Laflamme, R.

    2002-07-01

    The real-time probabilistic simulation of quantum systems in classical computers is known to be limited by the so-called dynamical sign problem, a problem leading to exponential complexity. In 1981 Richard Feynman raised some provocative questions in connection to the "exact imitation" of such systems using a special device named a "quantum computer". Feynman hesitated about the possibility of imitating fermion systems using such a device. Here we address some of his concerns and, in particular, investigate the simulation of fermionic systems. We show how quantum computers avoid the sign problem in some cases by reducing the complexity from exponential to polynomial. Our demonstration is based upon the use of isomorphisms of algebras. We present specific quantum algorithms that illustrate the main points of our algebraic approach.

  1. Prospects for quantum computing: Extremely doubtful

    NASA Astrophysics Data System (ADS)

    Dyakonov, M. I.

    2014-09-01

    The quantum computer is supposed to process information by applying unitary transformations to 2N complex amplitudes defining the state of N qubits. A useful machine needing N 103 or more, the number of continuous parameters describing the state of a quantum computer at any given moment is at least 21000 10300 which is much greater than the number of protons in the Universe. However, the theorists believe that the feasibility of large-scale quantum computing has been proved via the threshold theorem. Like for any theorem, the proof is based on a number of assumptions considered as axioms. However, in the physical world none of these assumptions can be fulfilled exactly. Any assumption can be only approached with some limited precision. So, the rather meaningless error per qubit per gate threshold must be supplemented by a list of the precisions with which all assumptions behind the threshold theorem should hold. Such a list still does not exist. The theory also seems to ignore the undesired free evolution of the quantum computer caused by the energy differences of quantum states entering any given superposition. Another important point is that the hypothetical quantum computer will be a system of 103 -106 qubits PLUS an extremely complex and monstrously sophisticated classical apparatus. This huge and strongly nonlinear system will generally exhibit instabilities and chaotic behavior.

  2. Photonic quantum information: science and technology.

    PubMed

    Takeuchi, Shigeki

    2016-01-01

    Recent technological progress in the generation, manipulation and detection of individual single photons has opened a new scientific field of photonic quantum information. This progress includes the realization of single photon switches, photonic quantum circuits with specific functions, and the application of novel photonic states to novel optical metrology beyond the limits of standard optics. In this review article, the recent developments and current status of photonic quantum information technology are overviewed based on the author's past and recent works. PMID:26755398

  3. Quantum state transition diagram: a bridge from classical computing to quantum computing

    NASA Astrophysics Data System (ADS)

    Hook, Loyd R., IV; Lee, Samuel C.

    2010-04-01

    Very few papers have been written on the topic of a quantum version of the finite state machine, (or finite state automata). Furthermore, these papers only serve to define what a quantum finite state machine might be in the mathematical sense using the early languages of Turing machines. This paper seeks to further develop the notion of a quantum finite state machine (FSM) using constructs developed for the classical FSM and utilized for classical FSM design. In particular the quantum state transition diagram (QSTD) is constructed to further the understanding and realization of quantum finite state machines and quantum computers.

  4. Computer Technology for Industry

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Shell Oil Company used a COSMIC program, called VISCEL to insure the accuracy of the company's new computer code for analyzing polymers, and chemical compounds. Shell reported that there were no other programs available that could provide the necessary calculations. Shell produces chemicals for plastic products used in the manufacture of automobiles, housewares, appliances, film, textiles, electronic equipment and furniture.

  5. Construction of a universal quantum computer

    NASA Astrophysics Data System (ADS)

    Lagana, Antonio A.; Lohe, M. A.; von Smekal, Lorenz

    2009-05-01

    We construct a universal quantum computer following Deutschs original proposal of a universal quantum Turing machine (UQTM). Like Deutschs UQTM, our machine can emulate any classical Turing machine and can execute any algorithm that can be implemented in the quantum gate array framework but under the control of a quantum program, and hence is universal. We present the architecture of the machine, which consists of a memory tape and a processor and describe the observables that comprise the registers of the processor and the instruction set, which includes a set of operations that can approximate any unitary operation to any desired accuracy and hence is quantum computationally universal. We present the unitary evolution operators that act on the machine to achieve universal computation and discuss each of them in detail and specify and discuss explicit program halting and concatenation schemes. We define and describe a set of primitive programs in order to demonstrate the universal nature of the machine. These primitive programs facilitate the implementation of more complex algorithms and we demonstrate their use by presenting a program that computes the NAND function, thereby also showing that the machine can compute any classically computable function.

  6. Qubus ancilla-driven quantum computation

    SciTech Connect

    Brown, Katherine Louise; De, Suvabrata; Kendon, Viv; Munro, Bill

    2014-12-04

    Hybrid matter-optical systems offer a robust, scalable path to quantum computation. Such systems have an ancilla which acts as a bus connecting the qubits. We demonstrate how using a continuous variable qubus as the ancilla provides savings in the total number of operations required when computing with many qubits.

  7. Biologically inspired path to quantum computer

    NASA Astrophysics Data System (ADS)

    Ogryzko, Vasily; Ozhigov, Yuri

    2014-12-01

    We describe an approach to quantum computer inspired by the information processing at the molecular level in living cells. It is based on the separation of a small ensemble of qubits inside the living system (e.g., a bacterial cell), such that coherent quantum states of this ensemble remain practically unchanged for a long time. We use the notion of a quantum kernel to describe such an ensemble. Quantum kernel is not strictly connected with certain particles; it permanently exchanges atoms and molecules with the environment, which makes quantum kernel a virtual notion. There are many reasons to expect that the state of quantum kernel of a living system can be treated as the stationary state of some Hamiltonian. While the quantum kernel is responsible for the stability of dynamics at the time scale of cellular life, at the longer inter-generation time scale it can change, varying smoothly in the course of biological evolution. To the first level of approximation, quantum kernel can be described in the framework of qubit modification of Jaynes-Cummings-Hubbard model, in which the relaxation corresponds to the exchange of matter between quantum kernel and the rest of the cell and is represented as Lindblad super-operators.

  8. Technology Trends: Buying a Computer.

    ERIC Educational Resources Information Center

    Strot, Melody; Benno, Mark

    1997-01-01

    Provides guidelines for buying computers for parents of gifted children. Steps for making decisions include deciding who will use the computer, deciding its purposes and what software packages will be used, determining current and future needs, setting a budget, and reviewing needs with salespersons and school-based technology specialists. (CR)

  9. Quantum computation with ``hot`` trapped ions

    SciTech Connect

    James, D.F.V.; Schneider, S. |; Milburn, G.J.

    1998-12-31

    The authors describe two methods that have been proposed to circumvent the problem of heating by external electromagnetic fields in ion trap quantum computers. Firstly the higher order modes of ion oscillation (i.e., modes other than the center-of-mass mode) have much slower heating rates, and can therefore be employed as a reliable quantum information bus. Secondly they discuss a recently proposed method combining adiabatic passage and a number-state dependent phase shift which allows quantum gates to be performed using the center-of-mass mode as the information bus, regardless of its initial state.

  10. Quantum learning for a quantum lattice gas computer

    NASA Astrophysics Data System (ADS)

    Behrman, Elizabeth; Steck, James

    2015-03-01

    Quantum lattice gas is the logical generalization of quantum cellular automata. In low energy the dynamics are well described by the Gross-Pitaevskii equation in the mean field limit, which is an effective nonlinear interaction model of a Bose-Einstein condensate. In previous work, we have shown in simulation that both spatial and temporal models of quantum learning computers can be used to ``design'' non-trivial quantum algorithms. The advantages of quantum learning over the usual practice of using quantum gate building blocks are, first, the rapidity with which the problem can be solved, without having to decompose the problem; second, the fact that our technique can be used readily even when the problem, or the operator, is not well understood; and, third, that because the interactions are a natural part of the physical system, connectivity is automatic. The advantage to quantum learning obviously grows with the size and the complexity of the problem. We develop and present our learning algorithm as applied to the mean field lattice gas equation, and present a few preliminary results.

  11. Quantum learning in a quantum lattice gas computer

    NASA Astrophysics Data System (ADS)

    Behrman, Elizabeth; Steck, James

    2015-04-01

    Quantum lattice gas is the logical generalization of quantum cellular automata. At low energy the dynamics are well described by the Gross-Pitaevskii equation in the mean field limit, which is an effective nonlinear interaction model of a Bose-Einstein condensate. In previous work, we have shown in simulation that both spatial and temporal models of quantum learning computers can be used to ``design'' non-trivial quantum algorithms. The advantages of quantum learning over the usual practice of using quantum gate building blocks are, first, the rapidity with which the problem can be solved, without having to decompose the problem; second, the fact that our technique can be used readily even when the problem, or the operator, is not well understood; and, third, that because the interactions are a natural part of the physical system, connectivity is automatic. The advantage to quantum learning obviously grows with the size and the complexity of the problem. We develop and present our learning algorithm as applied to the mean field lattice gas equation, and present a few preliminary results.

  12. Neuromorphic quantum computation with energy dissipation

    SciTech Connect

    Kinjo, Mitsunaga; Sato, Shigeo; Nakamiya, Yuuki; Nakajima, Koji

    2005-11-15

    Real parallel computing with a quantum computer attracts vast interest due to its extreme high potential. We propose a neuromorphic quantum computation algorithm based on an adiabatic Hamiltonian evolution with energy dissipation. This algorithm can be applied to problems if a cost function can be expressed in a quadratic form. This requirement results from the fact that our Hamiltonian is designed by following a method similar to an artificial neural network (ANN). The state of an ANN is often trapped at local minima, and the network outputs an error. Since the state of a quantum system with the proposed algorithm is always in the ground state according to the adiabatic theorem, it is not necessary to be concerned that the quantum state is trapped at local minima. However, there is no guarantee that a quantum algorithm based on an adiabatic Hamiltonian evolution with degeneration or level crossing is successfully executed. We show successful numerical simulation results with the proposed algorithm by introducing energy dissipation to keep the quantum state staying in the ground state, and then we show an application to the n-queen problem, which is one of the combinatorial optimization problems.

  13. Scalable quantum computing based on stationary spin qubits in coupled quantum dots inside double-sided optical microcavities.

    PubMed

    Wei, Hai-Rui; Deng, Fu-Guo

    2014-01-01

    Quantum logic gates are the key elements in quantum computing. Here we investigate the possibility of achieving a scalable and compact quantum computing based on stationary electron-spin qubits, by using the giant optical circular birefringence induced by quantum-dot spins in double-sided optical microcavities as a result of cavity quantum electrodynamics. We design the compact quantum circuits for implementing universal and deterministic quantum gates for electron-spin systems, including the two-qubit CNOT gate and the three-qubit Toffoli gate. They are compact and economic, and they do not require additional electron-spin qubits. Moreover, our devices have good scalability and are attractive as they both are based on solid-state quantum systems and the qubits are stationary. They are feasible with the current experimental technology, and both high fidelity and high efficiency can be achieved when the ratio of the side leakage to the cavity decay is low. PMID:25518899

  14. Scalable quantum computing based on stationary spin qubits in coupled quantum dots inside double-sided optical microcavities

    PubMed Central

    Wei, Hai-Rui; Deng, Fu-Guo

    2014-01-01

    Quantum logic gates are the key elements in quantum computing. Here we investigate the possibility of achieving a scalable and compact quantum computing based on stationary electron-spin qubits, by using the giant optical circular birefringence induced by quantum-dot spins in double-sided optical microcavities as a result of cavity quantum electrodynamics. We design the compact quantum circuits for implementing universal and deterministic quantum gates for electron-spin systems, including the two-qubit CNOT gate and the three-qubit Toffoli gate. They are compact and economic, and they do not require additional electron-spin qubits. Moreover, our devices have good scalability and are attractive as they both are based on solid-state quantum systems and the qubits are stationary. They are feasible with the current experimental technology, and both high fidelity and high efficiency can be achieved when the ratio of the side leakage to the cavity decay is low. PMID:25518899

  15. Random Numbers and Quantum Computers

    ERIC Educational Resources Information Center

    McCartney, Mark; Glass, David

    2002-01-01

    The topic of random numbers is investigated in such a way as to illustrate links between mathematics, physics and computer science. First, the generation of random numbers by a classical computer using the linear congruential generator and logistic map is considered. It is noted that these procedures yield only pseudo-random numbers since

  16. Random Numbers and Quantum Computers

    ERIC Educational Resources Information Center

    McCartney, Mark; Glass, David

    2002-01-01

    The topic of random numbers is investigated in such a way as to illustrate links between mathematics, physics and computer science. First, the generation of random numbers by a classical computer using the linear congruential generator and logistic map is considered. It is noted that these procedures yield only pseudo-random numbers since…

  17. Towards universal quantum computation through relativistic motion

    PubMed Central

    Bruschi, David Edward; Sabín, Carlos; Kok, Pieter; Johansson, Göran; Delsing, Per; Fuentes, Ivette

    2016-01-01

    We show how to use relativistic motion to generate continuous variable Gaussian cluster states within cavity modes. Our results can be demonstrated experimentally using superconducting circuits where tuneable boundary conditions correspond to mirrors moving with velocities close to the speed of light. In particular, we propose the generation of a quadripartite square cluster state as a first example that can be readily implemented in the laboratory. Since cluster states are universal resources for universal one-way quantum computation, our results pave the way for relativistic quantum computation schemes. PMID:26860584

  18. Towards universal quantum computation through relativistic motion.

    PubMed

    Bruschi, David Edward; Sabn, Carlos; Kok, Pieter; Johansson, Gran; Delsing, Per; Fuentes, Ivette

    2016-01-01

    We show how to use relativistic motion to generate continuous variable Gaussian cluster states within cavity modes. Our results can be demonstrated experimentally using superconducting circuits where tuneable boundary conditions correspond to mirrors moving with velocities close to the speed of light. In particular, we propose the generation of a quadripartite square cluster state as a first example that can be readily implemented in the laboratory. Since cluster states are universal resources for universal one-way quantum computation, our results pave the way for relativistic quantum computation schemes. PMID:26860584

  19. Trusted Computing Technologies, Intel Trusted Execution Technology.

    SciTech Connect

    Guise, Max Joseph; Wendt, Jeremy Daniel

    2011-01-01

    We describe the current state-of-the-art in Trusted Computing Technologies - focusing mainly on Intel's Trusted Execution Technology (TXT). This document is based on existing documentation and tests of two existing TXT-based systems: Intel's Trusted Boot and Invisible Things Lab's Qubes OS. We describe what features are lacking in current implementations, describe what a mature system could provide, and present a list of developments to watch. Critical systems perform operation-critical computations on high importance data. In such systems, the inputs, computation steps, and outputs may be highly sensitive. Sensitive components must be protected from both unauthorized release, and unauthorized alteration: Unauthorized users should not access the sensitive input and sensitive output data, nor be able to alter them; the computation contains intermediate data with the same requirements, and executes algorithms that the unauthorized should not be able to know or alter. Due to various system requirements, such critical systems are frequently built from commercial hardware, employ commercial software, and require network access. These hardware, software, and network system components increase the risk that sensitive input data, computation, and output data may be compromised.

  20. Adiabatic graph-state quantum computation

    NASA Astrophysics Data System (ADS)

    Antonio, B.; Markham, D.; Anders, J.

    2014-11-01

    Measurement-based quantum computation (MBQC) and holonomic quantum computation (HQC) are two very different computational methods. The computation in MBQC is driven by adaptive measurements executed in a particular order on a large entangled state. In contrast in HQC the system starts in the ground subspace of a Hamiltonian which is slowly changed such that a transformation occurs within the subspace. Following the approach of Bacon and Flammia, we show that any MBQC on a graph state with generalized flow (gflow) can be converted into an adiabatically driven holonomic computation, which we call adiabatic graph-state quantum computation (AGQC). We then investigate how properties of AGQC relate to the properties of MBQC, such as computational depth. We identify a trade-off that can be made between the number of adiabatic steps in AGQC and the norm of \\dot{H} as well as the degree of H, in analogy to the trade-off between the number of measurements and classical post-processing seen in MBQC. Finally the effects of performing AGQC with orderings that differ from standard MBQC are investigated.

  1. Mimicking time evolution within a quantum ground state: Ground-state quantum computation, cloning, and teleportation

    SciTech Connect

    Mizel, Ari

    2004-07-01

    Ground-state quantum computers mimic quantum-mechanical time evolution within the amplitudes of a time-independent quantum state. We explore the principles that constrain this mimicking. A no-cloning argument is found to impose strong restrictions. It is shown, however, that there is flexibility that can be exploited using quantum teleportation methods to improve ground-state quantum computer design.

  2. Quantum game simulator, using the circuit model of quantum computation

    NASA Astrophysics Data System (ADS)

    Vlachos, Panagiotis; Karafyllidis, Ioannis G.

    2009-10-01

    We present a general two-player quantum game simulator that can simulate any two-player quantum game described by a 2×2 payoff matrix (two strategy games).The user can determine the payoff matrices for both players, their strategies and the amount of entanglement between their initial strategies. The outputs of the simulator are the expected payoffs of each player as a function of the other player's strategy parameters and the amount of entanglement. The simulator also produces contour plots that divide the strategy spaces of the game in regions in which players can get larger payoffs if they choose to use a quantum strategy against any classical one. We also apply the simulator to two well-known quantum games, the Battle of Sexes and the Chicken game. Program summaryProgram title: Quantum Game Simulator (QGS) Catalogue identifier: AEED_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEED_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 3416 No. of bytes in distributed program, including test data, etc.: 583 553 Distribution format: tar.gz Programming language: Matlab R2008a (C) Computer: Any computer that can sufficiently run Matlab R2008a Operating system: Any system that can sufficiently run Matlab R2008a Classification: 4.15 Nature of problem: Simulation of two player quantum games described by a payoff matrix. Solution method: The program calculates the matrices that comprise the Eisert setup for quantum games based on the quantum circuit model. There are 5 parameters that can be altered. We define 3 of them as constant. We play the quantum game for all possible values for the other 2 parameters and store the results in a matrix. Unusual features: The software provides an easy way of simulating any two-player quantum games. Running time: Approximately 0.4 sec (Region Feature) and 0.3 sec (Payoff Feature) on a Intel Core 2 Duo GHz with 2 GB of memory under Windows XP.

  3. Quantum computer games: Schrdinger cat and hounds

    NASA Astrophysics Data System (ADS)

    Gordon, Michal; Gordon, Goren

    2012-05-01

    The quantum computer game 'Schrdinger cat and hounds' is the quantum extension of the well-known classical game fox and hounds. Its main objective is to teach the unique concepts of quantum mechanics in a fun way. 'Schrdinger cat and hounds' demonstrates the effects of superposition, destructive and constructive interference, measurements and entanglement. More advanced concepts, like particle-wave duality and decoherence, can also be taught using the game as a model. The game that has an optimal solution in the classical version, can have many different solutions and a new balance of powers in the quantum world. Game-aided lectures were given to high-school students which showed that it is a valid and entertaining teaching platform.

  4. A surface code quantum computer in silicon

    PubMed Central

    Hill, Charles D.; Peretz, Eldad; Hile, Samuel J.; House, Matthew G.; Fuechsle, Martin; Rogge, Sven; Simmons, Michelle Y.; Hollenberg, Lloyd C. L.

    2015-01-01

    The exceptionally long quantum coherence times of phosphorus donor nuclear spin qubits in silicon, coupled with the proven scalability of silicon-based nano-electronics, make them attractive candidates for large-scale quantum computing. However, the high threshold of topological quantum error correction can only be captured in a two-dimensional array of qubits operating synchronously and in parallelposing formidable fabrication and control challenges. We present an architecture that addresses these problems through a novel shared-control paradigm that is particularly suited to the natural uniformity of the phosphorus donor nuclear spin qubit states and electronic confinement. The architecture comprises a two-dimensional lattice of donor qubits sandwiched between two vertically separated control layers forming a mutually perpendicular crisscross gate array. Shared-control lines facilitate loading/unloading of single electrons to specific donors, thereby activating multiple qubits in parallel across the array on which the required operations for surface code quantum error correction are carried out by global spin control. The complexities of independent qubit control, wave function engineering, and ad hoc quantum interconnects are explicitly avoided. With many of the basic elements of fabrication and control based on demonstrated techniques and with simulated quantum operation below the surface code error threshold, the architecture represents a new pathway for large-scale quantum information processing in silicon and potentially in other qubit systems where uniformity can be exploited. PMID:26601310

  5. A surface code quantum computer in silicon.

    PubMed

    Hill, Charles D; Peretz, Eldad; Hile, Samuel J; House, Matthew G; Fuechsle, Martin; Rogge, Sven; Simmons, Michelle Y; Hollenberg, Lloyd C L

    2015-10-01

    The exceptionally long quantum coherence times of phosphorus donor nuclear spin qubits in silicon, coupled with the proven scalability of silicon-based nano-electronics, make them attractive candidates for large-scale quantum computing. However, the high threshold of topological quantum error correction can only be captured in a two-dimensional array of qubits operating synchronously and in parallel-posing formidable fabrication and control challenges. We present an architecture that addresses these problems through a novel shared-control paradigm that is particularly suited to the natural uniformity of the phosphorus donor nuclear spin qubit states and electronic confinement. The architecture comprises a two-dimensional lattice of donor qubits sandwiched between two vertically separated control layers forming a mutually perpendicular crisscross gate array. Shared-control lines facilitate loading/unloading of single electrons to specific donors, thereby activating multiple qubits in parallel across the array on which the required operations for surface code quantum error correction are carried out by global spin control. The complexities of independent qubit control, wave function engineering, and ad hoc quantum interconnects are explicitly avoided. With many of the basic elements of fabrication and control based on demonstrated techniques and with simulated quantum operation below the surface code error threshold, the architecture represents a new pathway for large-scale quantum information processing in silicon and potentially in other qubit systems where uniformity can be exploited. PMID:26601310

  6. Quantum optics: Science and technology in a new light

    NASA Astrophysics Data System (ADS)

    Walmsley, I. A.

    2015-05-01

    Light facilitates exploration of quantum phenomena that illuminate the basic properties of nature and also enables radical new technologies based on these phenomena. The critical features of quantum light that underpin the opportunities for discovery and application are exceptionally low noise and strong correlations. Rapid progress in both science and technology has been stimulated by adopting components developed for optical telecommunications and networking, such as highly efficient detectors, integrated photonic circuits, and waveguide- or nanostructure-based nonlinear optical devices. These provide the means to generate new quantum states of light and matter of unprecedented scale, containing many photons with quantum correlations across space and time. Notably, networks with only several tens of photons are already beyond what can be efficiently analyzed by current computers.

  7. Quantum optics: science and technology in a new light.

    PubMed

    Walmsley, I A

    2015-05-01

    Light facilitates exploration of quantum phenomena that illuminate the basic properties of nature and also enables radical new technologies based on these phenomena. The critical features of quantum light that underpin the opportunities for discovery and application are exceptionally low noise and strong correlations. Rapid progress in both science and technology has been stimulated by adopting components developed for optical telecommunications and networking, such as highly efficient detectors, integrated photonic circuits, and waveguide- or nanostructure-based nonlinear optical devices. These provide the means to generate new quantum states of light and matter of unprecedented scale, containing many photons with quantum correlations across space and time. Notably, networks with only several tens of photons are already beyond what can be efficiently analyzed by current computers. PMID:25931550

  8. Quantum information processing : science & technology.

    SciTech Connect

    Horton, Rebecca; Carroll, Malcolm S.; Tarman, Thomas David

    2010-09-01

    Qubits demonstrated using GaAs double quantum dots (DQD). The qubit basis states are the (1) singlet and (2) triplet stationary states. Long spin decoherence times in silicon spurs translation of GaAs qubit in to silicon. In the near term the goals are: (1) Develop surface gate enhancement mode double quantum dots (MOS & strained-Si/SiGe) to demonstrate few electrons and spin read-out and to examine impurity doped quantum-dots as an alternative architecture; (2) Use mobility, C-V, ESR, quantum dot performance & modeling to feedback and improve upon processing, this includes development of atomic precision fabrication at SNL; (3) Examine integrated electronics approaches to RF-SET; (4) Use combinations of numerical packages for multi-scale simulation of quantum dot systems (NEMO3D, EMT, TCAD, SPICE); and (5) Continue micro-architecture evaluation for different device and transport architectures.

  9. Industrial Superconducting Quantum Computer Development in Canada

    NASA Astrophysics Data System (ADS)

    Rose, Geordie

    2002-05-01

    Quantum computation is one of the most active areas of research in academia. Nearly every university in the world that has a science department has researchers who are working on either trying to build hardware or develop algorithms for these machines. In this talk I will describe D-Wave's goals and achievements in assembling a global research network, centered in Canada, whose purpose is the development of superconducting quantum computer hardware. In addition I will describe the technical approach that we are concentrating on, involving cuprate-based flux qubits and niobium RSFQ control circuitry. Finally I will introduce a very important application of these machines, namely their use as simulators of other quantum systems, in the context of human pharmaceutical drug and vaccine design.

  10. Simulations of Probabilities for Quantum Computing

    NASA Technical Reports Server (NTRS)

    Zak, M.

    1996-01-01

    It has been demonstrated that classical probabilities, and in particular, probabilistic Turing machine, can be simulated by combining chaos and non-LIpschitz dynamics, without utilization of any man-made devices (such as random number generators). Self-organizing properties of systems coupling simulated and calculated probabilities and their link to quantum computations are discussed.

  11. Towards fault tolerant adiabatic quantum computation.

    PubMed

    Lidar, Daniel A

    2008-04-25

    I show how to protect adiabatic quantum computation (AQC) against decoherence and certain control errors, using a hybrid methodology involving dynamical decoupling, subsystem and stabilizer codes, and energy gaps. Corresponding error bounds are derived. As an example, I show how to perform decoherence-protected AQC against local noise using at most two-body interactions. PMID:18518178

  12. Blind Quantum Computing with Weak Coherent Pulses

    NASA Astrophysics Data System (ADS)

    Dunjko, Vedran; Kashefi, Elham; Leverrier, Anthony

    2012-05-01

    The universal blind quantum computation (UBQC) protocol [A. Broadbent, J. Fitzsimons, and E. Kashefi, in Proceedings of the 50th Annual IEEE Symposiumon Foundations of Computer Science (IEEE Computer Society, Los Alamitos, CA, USA, 2009), pp. 517-526.] allows a client to perform quantum computation on a remote server. In an ideal setting, perfect privacy is guaranteed if the client is capable of producing specific, randomly chosen single qubit states. While from a theoretical point of view, this may constitute the lowest possible quantum requirement, from a pragmatic point of view, generation of such states to be sent along long distances can never be achieved perfectly. We introduce the concept of ɛ blindness for UBQC, in analogy to the concept of ɛ security developed for other cryptographic protocols, allowing us to characterize the robustness and security properties of the protocol under possible imperfections. We also present a remote blind single qubit preparation protocol with weak coherent pulses for the client to prepare, in a delegated fashion, quantum states arbitrarily close to perfect random single qubit states. This allows us to efficiently achieve ɛ-blind UBQC for any ɛ>0, even if the channel between the client and the server is arbitrarily lossy.

  13. The quantum computer game: citizen science

    NASA Astrophysics Data System (ADS)

    Damgaard, Sidse; Mlmer, Klaus; Sherson, Jacob

    2013-05-01

    Progress in the field of quantum computation is hampered by daunting technical challenges. Here we present an alternative approach to solving these by enlisting the aid of computer players around the world. We have previously examined a quantum computation architecture involving ultracold atoms in optical lattices and strongly focused tweezers of light. In The Quantum Computer Game (see http://www.scienceathome.org/), we have encapsulated the time-dependent Schrdinger equation for the problem in a graphical user interface allowing for easy user input. Players can then search the parameter space with real-time graphical feedback in a game context with a global high-score that rewards short gate times and robustness to experimental errors. The game which is still in a demo version has so far been tried by several hundred players. Extensions of the approach to other models such as Gross-Pitaevskii and Bose-Hubbard are currently under development. The game has also been incorporated into science education at high-school and university level as an alternative method for teaching quantum mechanics. Initial quantitative evaluation results are very positive. AU Ideas Center for Community Driven Research, CODER.

  14. Quantum computation with Turaev-Viro codes

    SciTech Connect

    Koenig, Robert; Kuperberg, Greg; Reichardt, Ben W.

    2010-12-15

    For a 3-manifold with triangulated boundary, the Turaev-Viro topological invariant can be interpreted as a quantum error-correcting code. The code has local stabilizers, identified by Levin and Wen, on a qudit lattice. Kitaev's toric code arises as a special case. The toric code corresponds to an abelian anyon model, and therefore requires out-of-code operations to obtain universal quantum computation. In contrast, for many categories, such as the Fibonacci category, the Turaev-Viro code realizes a non-abelian anyon model. A universal set of fault-tolerant operations can be implemented by deforming the code with local gates, in order to implement anyon braiding. We identify the anyons in the code space, and present schemes for initialization, computation and measurement. This provides a family of constructions for fault-tolerant quantum computation that are closely related to topological quantum computation, but for which the fault tolerance is implemented in software rather than coming from a physical medium.

  15. Holonomic quantum computation with electron spins in quantum dots

    SciTech Connect

    Golovach, Vitaly N.; Borhani, Massoud; Loss, Daniel

    2010-02-15

    With the help of the spin-orbit interaction, we propose a scheme to perform holonomic single-qubit gates on the electron spin confined to a quantum dot. The manipulation is done in the absence (or presence) of an applied magnetic field. By adiabatic changing the position of the confinement potential, one can rotate the spin state of the electron around the Bloch sphere in semiconductor heterostructures. The dynamics of the system is equivalent to employing an effective non-Abelian gauge potential whose structure depends on the type of the spin-orbit interaction. As an example, we find an analytic expression for the electron spin dynamics when the dot is moved around a circular path (with radius R) on the two dimensional electron gas (2DEG) and show that all single-qubit gates can be realized by tuning the radius and orientation of the circular paths. Moreover, using the Heisenberg exchange interaction, we demonstrate how one can generate two-qubit gates by bringing two quantum dots near each other, yielding a scalable scheme to perform quantum computing on arbitrary N qubits. This proposal shows a way of realizing holonomic quantum computers in solid-state systems.

  16. Error correction for adiabatic quantum computing

    NASA Astrophysics Data System (ADS)

    Young, Kevin

    2014-03-01

    Adiabatic quantum computing (AQC) is an alternative to the standard circuit model of quantum computation, wherein a quasistatic Hamiltonian, whose ground state at time T = 0 is simple and easily prepared, evolves slowly so that by the final time T = 1 the ground state encodes the answer to a problem. This procedure admits a novel set of natural algorithms for optimization problems, and is computationally equivalent to the circuit model in the absence of noise. But noise, and its effect on computational power, cannot be ignored. In light of this, AQC is particularly intriguing, possessing an intrinsic resilience to certain kinds of errors, including flawed time-dependent control Hamiltonians, dephasing in the energy basis, and energy relaxation. But these are far from the only errors afflicting quantum information processors, and any practical model of computation must be fault-tolerant to all expected forms of noise and error. With respect to this broader class of errors, true fault tolerance for AQC has remained elusive. In this talk we will discuss our progress towards this goal: (1) we identified and solved a variety of challenges on the road to error correction and fault tolerance in AQC; and (2) we identified a couple of major roadblocks, which appear insurmountable, and make us ultimately pessimistic that fault-tolerant AQC will ever be achieved.

  17. Optical Computers and Space Technology

    NASA Technical Reports Server (NTRS)

    Abdeldayem, Hossin A.; Frazier, Donald O.; Penn, Benjamin; Paley, Mark S.; Witherow, William K.; Banks, Curtis; Hicks, Rosilen; Shields, Angela

    1995-01-01

    The rapidly increasing demand for greater speed and efficiency on the information superhighway requires significant improvements over conventional electronic logic circuits. Optical interconnections and optical integrated circuits are strong candidates to provide the way out of the extreme limitations imposed on the growth of speed and complexity of nowadays computations by the conventional electronic logic circuits. The new optical technology has increased the demand for high quality optical materials. NASA's recent involvement in processing optical materials in space has demonstrated that a new and unique class of high quality optical materials are processible in a microgravity environment. Microgravity processing can induce improved orders in these materials and could have a significant impact on the development of optical computers. We will discuss NASA's role in processing these materials and report on some of the associated nonlinear optical properties which are quite useful for optical computers technology.

  18. Deterministic quantum computation with one photonic qubit

    NASA Astrophysics Data System (ADS)

    Hor-Meyll, M.; Tasca, D. S.; Walborn, S. P.; Ribeiro, P. H. Souto; Santos, M. M.; Duzzioni, E. I.

    2015-07-01

    We show that deterministic quantum computing with one qubit (DQC1) can be experimentally implemented with a spatial light modulator, using the polarization and the transverse spatial degrees of freedom of light. The scheme allows the computation of the trace of a high-dimension matrix, being limited by the resolution of the modulator panel and the technical imperfections. In order to illustrate the method, we compute the normalized trace of unitary matrices and implement the Deutsch-Jozsa algorithm. The largest matrix that can be manipulated with our setup is 1080 ×1920 , which is able to represent a system with approximately 21 qubits.

  19. Regge Calculus and the Quantum Computational Universe

    NASA Astrophysics Data System (ADS)

    Miller, Warner; McDonald, Jonathan

    2007-04-01

    This talk examines the use of Regge Calculus as a tool to embed a quantum computational network into a spacetime manifold. After briefly describing Seth Lloyd's recent model Computational Universe model for spacetime histories, and introducing some basic features of Regge Calculus, we will explore the use null edges in Regge Calculus. Special attention will be focused on the coupling of the Regge equations to the computational network. In particular, we examine the right-hand side of the Regge equations and the coupling of the source in a lattice spacetime.

  20. Linear Optical Quantum Computing in a Single Spatial Mode

    NASA Astrophysics Data System (ADS)

    Walmsley, Ian

    2014-05-01

    We present a scheme for linear optical quantum computing using time-bin encoded qubits in a single spatial mode. This scheme allows arbitrary numbers of qubits to be encoded in the same mode, circumventing the requirement for many spatial modes that challenges the scalability of other schemes, and exploiting the inherent stability and robustness of time-frequency optical modes. This approach leverages the architecture of modern telecommunications systems, and opens a door to very high dimensional Hilbert spaces while maintaining compact device designs. Further, temporal encodings benefit from intrinsic robustness to inhomogeneities in transmission mediums. These advantages have been recognized in works exploring the preparation of time-frequency entangled states both for tests of fundamental quantum phenomena, and for quantum communications technologies including key distribution and teleportation. Here we extend this idea to computation. In particular, we present methods for single-qubit operations and heralded controlled phase (CPhase) gates, providing a sufficient set of operations for universal quantum computing with the Knill-Laflamme-Milburn scheme. As a test of our scheme, we demonstrate the first entirely single spatial mode implementation of a two-qubit quantum gate and show its operation with an average fidelity of 0.84 /pm 0.07. An analysis of the performance of current technologies suggests that our scheme offers a promising route for the construction of quantum circuits beyond the few-qubit level. In addition, we foresee that our investigation may motivate further development of the approaches presented into a regime in which time bins are temporally overlapped and frequency based manipulations become necessary, opening up encodings of even higher densities. This work was supported by the Engineering and Physical Sciences Research Council (EP/H03031X/1), the European Commission project Q-ESSENCE (248095) and the Air Force Office of Scientific Research (European Office of Aerospace Research and Development).

  1. Scheme for Quantum Computing Immune to Decoherence

    NASA Technical Reports Server (NTRS)

    Williams, Colin; Vatan, Farrokh

    2008-01-01

    A constructive scheme has been devised to enable mapping of any quantum computation into a spintronic circuit in which the computation is encoded in a basis that is, in principle, immune to quantum decoherence. The scheme is implemented by an algorithm that utilizes multiple physical spins to encode each logical bit in such a way that collective errors affecting all the physical spins do not disturb the logical bit. The scheme is expected to be of use to experimenters working on spintronic implementations of quantum logic. Spintronic computing devices use quantum-mechanical spins (typically, electron spins) to encode logical bits. Bits thus encoded (denoted qubits) are potentially susceptible to errors caused by noise and decoherence. The traditional model of quantum computation is based partly on the assumption that each qubit is implemented by use of a single two-state quantum system, such as an electron or other spin-1.2 particle. It can be surprisingly difficult to achieve certain gate operations . most notably, those of arbitrary 1-qubit gates . in spintronic hardware according to this model. However, ironically, certain 2-qubit interactions (in particular, spin-spin exchange interactions) can be achieved relatively easily in spintronic hardware. Therefore, it would be fortunate if it were possible to implement any 1-qubit gate by use of a spin-spin exchange interaction. While such a direct representation is not possible, it is possible to achieve an arbitrary 1-qubit gate indirectly by means of a sequence of four spin-spin exchange interactions, which could be implemented by use of four exchange gates. Accordingly, the present scheme provides for mapping any 1-qubit gate in the logical basis into an equivalent sequence of at most four spin-spin exchange interactions in the physical (encoded) basis. The complexity of the mathematical derivation of the scheme from basic quantum principles precludes a description within this article; it must suffice to report that the derivation provides explicit constructions for finding the exchange couplings in the physical basis needed to implement any arbitrary 1-qubit gate. These constructions lead to spintronic encodings of quantum logic that are more efficient than those of a previously published scheme that utilizes a universal but fixed set of gates.

  2. Discrete Wigner functions and quantum computational speedup

    SciTech Connect

    Galvao, Ernesto F.

    2005-04-01

    Gibbons et al. [Phys. Rev. A 70, 062101 (2004)] have recently defined a class of discrete Wigner functions W to represent quantum states in a finite Hilbert space dimension d. I characterize the set C{sub d} of states having non-negative W simultaneously in all definitions of W in this class. For d{<=}5 I show C{sub d} is the convex hull of stabilizer states. This supports the conjecture that negativity of W is necessary for exponential speedup in pure-state quantum computation.

  3. Quantum computing gates via optimal control

    NASA Astrophysics Data System (ADS)

    Atia, Yosi; Elias, Yuval; Mor, Tal; Weinstein, Yossi

    2014-10-01

    We demonstrate the use of optimal control to design two entropy-manipulating quantum gates which are more complex than the corresponding, commonly used, gates, such as CNOT and Toffoli (CCNOT): A two-qubit gate called polarization exchange (PE) and a three-qubit gate called polarization compression (COMP) were designed using GRAPE, an optimal control algorithm. Both gates were designed for a three-spin system. Our design provided efficient and robust nuclear magnetic resonance (NMR) radio frequency (RF) pulses for 13C2-trichloroethylene (TCE), our chosen three-spin system. We then experimentally applied these two quantum gates onto TCE at the NMR lab. Such design of these gates and others could be relevant for near-future applications of quantum computing devices.

  4. Center for Advanced Computational Technology

    NASA Technical Reports Server (NTRS)

    Noor, Ahmed K.

    2000-01-01

    The Center for Advanced Computational Technology (ACT) was established to serve as a focal point for diverse research activities pertaining to application of advanced computational technology to future aerospace systems. These activities include the use of numerical simulations, artificial intelligence methods, multimedia and synthetic environments, and computational intelligence, in the modeling, analysis, sensitivity studies, optimization, design and operation of future aerospace systems. The Center is located at NASA Langley and is an integral part of the School of Engineering and Applied Science of the University of Virginia. The Center has four specific objectives: 1) conduct innovative research on applications of advanced computational technology to aerospace systems; 2) act as pathfinder by demonstrating to the research community what can be done (high-potential, high-risk research); 3) help in identifying future directions of research in support of the aeronautical and space missions of the twenty-first century; and 4) help in the rapid transfer of research results to industry and in broadening awareness among researchers and engineers of the state-of-the-art in applications of advanced computational technology to the analysis, design prototyping and operations of aerospace and other high-performance engineering systems. In addition to research, Center activities include helping in the planning and coordination of the activities of a multi-center team of NASA and JPL researchers who are developing an intelligent synthesis environment for future aerospace systems; organizing workshops and national symposia; as well as writing state-of-the-art monographs and NASA special publications on timely topics.

  5. EDITORIAL: Quantum science and technology at the nanoscale Quantum science and technology at the nanoscale

    NASA Astrophysics Data System (ADS)

    Demming, Anna

    2010-07-01

    The development of quantum theory was an archetypal scientific revolution in early twentieth-century physics. In many ways, the probabilities and uncertainties that replaced the ubiquitous application of classical mechanics may have seemed a violent assault on logic and reason. 'Something unknown is doing we don't know what-that is what our theory amounts to,' Sir Arthur Eddington famously remarked, adding, 'It does not sound a particularly illuminating theory. I have read something like it elsewhere: the slithy toves, did gyre and gimble in the wabe' [1]. Today, quantum mechanics no longer seems a dark art best confined to the boundaries of physics and philosophy. Scanning probe micrographs have captured actual images of quantum-mechanical interference patterns [2], and familiarity has made the claims of quantum theory more palatable. An understanding of quantum effects is essential for nanoscale science and technology research. This special issue on quantum science and technology at the nanoscale collates some of the latest research that is extending the boundaries of our knowledge and understanding in the field. Quantum phenomena have become particularly significant in attempts to further reduce the size of electronic devices, the trend widely referred to as Moore's law. In this issue, researchers in Switzerland report results from transport studies on graphene. The researchers investigate the conductance variance in systems with superconducting contacts [3]. Also in this issue, researchers in Germany calculate the effects of spin-orbit coupling in a molecular dimer and predict nonlinear transport. They also explain how ferromagnetic electrodes can be used to probe these interactions [4]. Our understanding of spin and the ability to manipulate it has advanced greatly since the notion of spin was first proposed. However, it remains the case that little is known about local coherent fluctuations of spin polarizations, the scale on which they occur, how they are correlated, and how they influence spin currents and their fluctuations, as well as the mechanisms behind current-induced spin polarizations in chaotic ballistic systems. In a theoretical report on current-induced spin polarization from the University of Arizona, progress is made in filling in some of these gaps, and a 'spin-probe' model is proposed [5]. Spin is also an important element in quantum information research. With electron spin coherence lifetimes exceeding 1 ms at room temperature, as well as the added benefit of being optically addressable, nitrogen-vacancy defects in diamond have been identified as having considerable potential for quantum information applications. Now researchers in the US describe the fabrication and low-temperature characterization of silica microdisk cavities coupled to diamond nanoparticles, and present theoretical and experimental studies of gallium phosphide structures coupled to nitrogen-vacancy centers in bulk diamond [6]. Double quantum dots have been considered as prospective candidates for charge qubits for quantum information processors. The application of a bias voltage can be used to control tunnelling between the double quantum dots, allowing the energy states to be tuned. Researchers in Switzerland investigate experimentally the effect of ohmic heating of the phonon bath on decoherence, and find that the system can be considered as a thermoelectric generator [7]. This progress has only been made possible by advances in our understanding of the fundamental science behind quantum mechanics, and work exploring this territory is still a hotbed of activity and progress. Increasingly sophisticated tools, both numerical and experimental, have facilitated engagement with quantum phenomena in nanoscale systems. Molecular spin clusters represent an ideal setting within solid-state systems to test concepts in quantum mechanics, as highlighted in this issue by researchers in Italy, who report their work on controlling entanglement between molecular spins [8]. Nanofabrication techniques have seen tremendous advances that have enabled scientists to realise new experimental electronics architectures. Using photolithography, chemical etching and electrodeposition, a collaboration of researchers in China, France and the US has fabricated mechanically controllable break junctions with finely adjustable nanogaps between two gold electrodes on solid state chips [9]. The structures can be used to characterize the electron transport properties of single molecules. In many ways, experimental realization of quantum phenomena has invigorated theoretical endeavours; experiments on the Kondo effect, for example, have renewed interest in finding new approximate solutions for the single impurity Anderson model. Researchers in Brazil present work on finding solutions to the Anderson Hamiltonian based on the atomic approach, which is simple to implement and has a low computational cost [10]. Theoretical descriptions have developed into powerful and sophisticated tools for explaining, understanding and even predicting the behaviour of quantum systems. Recent progress in the theoretical description of correlation and quantum fluctuation phenomena in charge transport through single molecules, quantum dots, and quantum wires is provided in a topical review by researchers in Germany [11]. While a claim to a complete understanding of quantum phenomena may be premature, certainly vast progress has been made in learning how to navigate new territory in the quantum world. And what is more, in exploring novel systems and the continued efforts to develop devices with capabilities enhanced due to quantum effects, we are learning to exploit it. References [1] Eddington A S 1929 The Nature of the Physical World (New York: The University Press) [2] Crommie M F, Lutz C P and Eigler D M 1993 Science 262 218-20 [3] Trbovic J, Minder N, Freitag F and Schönenberger C 2010 Superconductivity-enhanced conductance fluctuations in few-layer graphene Nanotechnology 21 274005 [4] Herzog S and Wegewijs M R 2010 Dzyaloshinskii-Moriya interaction in transport through single-molecule transistors Nanotechnology 21 274010 [5] Jacquod Ph 2010 Scattering theory of current-induced spin polarization Nanotechnology 21 274006 [6] Santori C, Barclay P E, Fu K-M C, Beausoleil R G, Spillane S and Fisch M 2010 Nanophotonics for quantum optics using nitrogen-vacancy centers in diamond Nanotechnology 21 274008 [7] Gasser U, Gustavsson S, Küng B, Ensslin K and Ihn T 2010 Phonon-mediated back-action of a charge readout on a double quantum dot Nanotechnology 21 274003 [8] Troiani F, Bellini V, Candini A, Lorusso G and Affronte M 2010 Spin entanglement in supramolecular structures Nanotechnology 21 274009 [9] Tian J-H et al 2010 The fabrication and characterization of adjustable nanogaps between gold electrodes on chip for electrical measurement of single molecules Nanotechnology 21 274012 [10] Tian J-H et al Lobo T, Figueira M S and Foglio M E 2010 The atomic approach of the Anderson model for the U finite case: application to a quantum dot Nanotechnology 21 274007 [11] Andergassen S, Meden V, Schoeller H, Splettstoesser J and Wegewijs M R 2010 Charge transport through single molecules, quantum dots and quantum wires Nanotechnology 21 272001

  6. Non-abelian fractional quantum hall effect for fault-resistant topological quantum computation.

    SciTech Connect

    Pan, Wei; Thalakulam, Madhu; Shi, Xiaoyan; Crawford, Matthew; Nielsen, Erik; Cederberg, Jeffrey George

    2013-10-01

    Topological quantum computation (TQC) has emerged as one of the most promising approaches to quantum computation. Under this approach, the topological properties of a non-Abelian quantum system, which are insensitive to local perturbations, are utilized to process and transport quantum information. The encoded information can be protected and rendered immune from nearly all environmental decoherence processes without additional error-correction. It is believed that the low energy excitations of the so-called =5/2 fractional quantum Hall (FQH) state may obey non-Abelian statistics. Our goal is to explore this novel FQH state and to understand and create a scientific foundation of this quantum matter state for the emerging TQC technology. We present in this report the results from a coherent study that focused on obtaining a knowledge base of the physics that underpins TQC. We first present the results of bulk transport properties, including the nature of disorder on the 5/2 state and spin transitions in the second Landau level. We then describe the development and application of edge tunneling techniques to quantify and understand the quasiparticle physics of the 5/2 state.

  7. Measurement and Information Extraction in Complex Dynamics Quantum Computation

    NASA Astrophysics Data System (ADS)

    Casati, Giulio; Montangero, Simone

    Quantum Information processing has several di.erent applications: some of them can be performed controlling only few qubits simultaneously (e.g. quantum teleportation or quantum cryptography) [1]. Usually, the transmission of large amount of information is performed repeating several times the scheme implemented for few qubits. However, to exploit the advantages of quantum computation, the simultaneous control of many qubits is unavoidable [2]. This situation increases the experimental di.culties of quantum computing: maintaining quantum coherence in a large quantum system is a di.cult task. Indeed a quantum computer is a many-body complex system and decoherence, due to the interaction with the external world, will eventually corrupt any quantum computation. Moreover, internal static imperfections can lead to quantum chaos in the quantum register thus destroying computer operability [3]. Indeed, as it has been shown in [4], a critical imperfection strength exists above which the quantum register thermalizes and quantum computation becomes impossible. We showed such e.ects on a quantum computer performing an e.cient algorithm to simulate complex quantum dynamics [5,6].

  8. Quantum computation: algorithms and implementation in quantum dot devices

    NASA Astrophysics Data System (ADS)

    Gamble, John King

    In this thesis, we explore several aspects of both the software and hardware of quantum computation. First, we examine the computational power of multi-particle quantum random walks in terms of distinguishing mathematical graphs. We study both interacting and non-interacting multi-particle walks on strongly regular graphs, proving some limitations on distinguishing powers and presenting extensive numerical evidence indicative of interactions providing more distinguishing power. We then study the recently proposed adiabatic quantum algorithm for Google PageRank, and show that it exhibits power-law scaling for realistic WWW-like graphs. Turning to hardware, we next analyze the thermal physics of two nearby 2D electron gas (2DEG), and show that an analogue of the Coulomb drag effect exists for heat transfer. In some distance and temperature, this heat transfer is more significant than phonon dissipation channels. After that, we study the dephasing of two-electron states in a single silicon quantum dot. Specifically, we consider dephasing due to the electron-phonon coupling and charge noise, separately treating orbital and valley excitations. In an ideal system, dephasing due to charge noise is strongly suppressed due to a vanishing dipole moment. However, introduction of disorder or anharmonicity leads to large effective dipole moments, and hence possibly strong dephasing. Building on this work, we next consider more realistic systems, including structural disorder systems. We present experiment and theory, which demonstrate energy levels that vary with quantum dot translation, implying a structurally disordered system. Finally, we turn to the issues of valley mixing and valley-orbit hybridization, which occurs due to atomic-scale disorder at quantum well interfaces. We develop a new theoretical approach to study these effects, which we name the disorder-expansion technique. We demonstrate that this method successfully reproduces atomistic tight-binding techniques, while using a fraction of the computational resources and providing considerably more physical insight. Using this technique, we demonstrate that large dipole moments can exist between valley states in disordered systems, and calculate corrections to intervalley tunnel rates..

  9. Dual-code quantum computation model

    NASA Astrophysics Data System (ADS)

    Choi, Byung-Soo

    2015-08-01

    In this work, we propose the dual-code quantum computation modela fault-tolerant quantum computation scheme which alternates between two different quantum error-correction codes. Since the chosen two codes have different sets of transversal gates, we can implement a universal set of gates transversally, thereby reducing the overall cost. We use code teleportation to convert between quantum states in different codes. The overall cost is decreased if code teleportation requires fewer resources than the fault-tolerant implementation of the non-transversal gate in a specific code. To analyze the cost reduction, we investigate two cases with different base codes, namely the Steane and Bacon-Shor codes. For the Steane code, neither the proposed dual-code model nor another variation of it achieves any cost reduction since the conventional approach is simple. For the Bacon-Shor code, the three proposed variations of the dual-code model reduce the overall cost. However, as the encoding level increases, the cost reduction decreases and becomes negative. Therefore, the proposed dual-code model is advantageous only when the encoding level is low and the cost of the non-transversal gate is relatively high.

  10. Quantum computation architecture using optical tweezers

    SciTech Connect

    Weitenberg, Christof; Kuhr, Stefan; Moelmer, Klaus; Sherson, Jacob F.

    2011-09-15

    We present a complete architecture for scalable quantum computation with ultracold atoms in optical lattices using optical tweezers focused to the size of a lattice spacing. We discuss three different two-qubit gates based on local collisional interactions. The gates between arbitrary qubits require the transport of atoms to neighboring sites. We numerically optimize the nonadiabatic transport of the atoms through the lattice and the intensity ramps of the optical tweezer in order to maximize the gate fidelities. We find overall gate times of a few 100 {mu}s, while keeping the error probability due to vibrational excitations and spontaneous scattering below 10{sup -3}. The requirements on the positioning error and intensity noise of the optical tweezer and the magnetic field stability are analyzed and we show that atoms in optical lattices could meet the requirements for fault-tolerant scalable quantum computing.

  11. Non-unitary probabilistic quantum computing circuit and method

    NASA Technical Reports Server (NTRS)

    Williams, Colin P. (Inventor); Gingrich, Robert M. (Inventor)

    2009-01-01

    A quantum circuit performing quantum computation in a quantum computer. A chosen transformation of an initial n-qubit state is probabilistically obtained. The circuit comprises a unitary quantum operator obtained from a non-unitary quantum operator, operating on an n-qubit state and an ancilla state. When operation on the ancilla state provides a success condition, computation is stopped. When operation on the ancilla state provides a failure condition, computation is performed again on the ancilla state and the n-qubit state obtained in the previous computation, until a success condition is obtained.

  12. Ultralow Threshold Quantum Well Lasers For Computer Interconnects

    NASA Astrophysics Data System (ADS)

    Mittelstein, Michael; Ury, Israel; Bar-Chaim, Nadav; Lau, Kam Y.; Ungar, Jeffrey E.; Yariv, Amnon

    1990-01-01

    Optical computer interconnects appear very attractive when integration of state of the art technology of quantum well GaAs/GaA1As lasers is considered. These ultralow threshold lasers provide the very high transmission rates and the inherent simplicity required for such systems. A detailed design is presented for a 5 Gbit s-1 transmission rate, suppression of pattern effects, and a system power supply of approximately 25 mW per laser. Existing experimental data show that little extrapolation is required to reach that kind of performance from state of the art technology.

  13. Quantum computing with quantum dots using the Heisenberg exchange interaction

    NASA Astrophysics Data System (ADS)

    Dewaele, Nick J.

    One of the most promising systems for creating a working quantum computer is the triple quantum dots in a linear semiconductor. One of the biggest advantages is that we are able to perform Heisenberg exchange gates on the physical qubits. These exchanges are both fast and relatively low energy. Which means that they would be excellent for producing fast and accurate operations. In order to prevent leakage errors we use a 3 qubit DFS to encode a logical qubit. Here we determine the theoretical time dependent affects of applying the Heisenberg exchange gates in the DFS basis as well as the effect of applying multiple exchange gates at the same time. we also find that applying two heisenberg exchange gates at the same time is an effective way of implementing a leakage elimination operator.

  14. Universal quantum computation with metaplectic anyons

    SciTech Connect

    Cui, Shawn X.; Wang, Zhenghan E-mail: zhenghwa@microsoft.com

    2015-03-15

    We show that braidings of the metaplectic anyons X{sub ϵ} in SO(3){sub 2} = SU(2){sub 4} with their total charge equal to the metaplectic mode Y supplemented with projective measurements of the total charge of two metaplectic anyons are universal for quantum computation. We conjecture that similar universal anyonic computing models can be constructed for all metaplectic anyon systems SO(p){sub 2} for any odd prime p ≥ 5. In order to prove universality, we find new conceptually appealing universal gate sets for qutrits and qupits.

  15. Universal quantum gates for Single Cooper Pair Box based quantum computing

    NASA Technical Reports Server (NTRS)

    Echternach, P.; Williams, C. P.; Dultz, S. C.; Braunstein, S.; Dowling, J. P.

    2000-01-01

    We describe a method for achieving arbitrary 1-qubit gates and controlled-NOT gates within the context of the Single Cooper Pair Box (SCB) approach to quantum computing. Such gates are sufficient to support universal quantum computation.

  16. Scalable quantum computer architecture with coupled donor-quantum dot qubits

    DOEpatents

    Schenkel, Thomas; Lo, Cheuk Chi; Weis, Christoph; Lyon, Stephen; Tyryshkin, Alexei; Bokor, Jeffrey

    2014-08-26

    A quantum bit computing architecture includes a plurality of single spin memory donor atoms embedded in a semiconductor layer, a plurality of quantum dots arranged with the semiconductor layer and aligned with the donor atoms, wherein a first voltage applied across at least one pair of the aligned quantum dot and donor atom controls a donor-quantum dot coupling. A method of performing quantum computing in a scalable architecture quantum computing apparatus includes arranging a pattern of single spin memory donor atoms in a semiconductor layer, forming a plurality of quantum dots arranged with the semiconductor layer and aligned with the donor atoms, applying a first voltage across at least one aligned pair of a quantum dot and donor atom to control a donor-quantum dot coupling, and applying a second voltage between one or more quantum dots to control a Heisenberg exchange J coupling between quantum dots and to cause transport of a single spin polarized electron between quantum dots.

  17. Infinite possibilities: Computational structures technology

    NASA Astrophysics Data System (ADS)

    Beam, Sherilee F.

    1994-12-01

    Computational Fluid Dynamics (or CFD) methods are very familiar to the research community. Even the general public has had some exposure to CFD images, primarily through the news media. However, very little attention has been paid to CST--Computational Structures Technology. Yet, no important design can be completed without it. During the first half of this century, researchers only dreamed of designing and building structures on a computer. Today their dreams have become practical realities as computational methods are used in all phases of design, fabrication and testing of engineering systems. Increasingly complex structures can now be built in even shorter periods of time. Over the past four decades, computer technology has been developing, and early finite element methods have grown from small in-house programs to numerous commercial software programs. When coupled with advanced computing systems, they help engineers make dramatic leaps in designing and testing concepts. The goals of CST include: predicting how a structure will behave under actual operating conditions; designing and complementing other experiments conducted on a structure; investigating microstructural damage or chaotic, unpredictable behavior; helping material developers in improving material systems; and being a useful tool in design systems optimization and sensitivity techniques. Applying CST to a structure problem requires five steps: (1) observe the specific problem; (2) develop a computational model for numerical simulation; (3) develop and assemble software and hardware for running the codes; (4) post-process and interpret the results; and (5) use the model to analyze and design the actual structure. Researchers in both industry and academia continue to make significant contributions to advance this technology with improvements in software, collaborative computing environments and supercomputing systems. As these environments and systems evolve, computational structures technology will evolve. By using CST in the design and operation of future structures systems, engineers will have a better understanding of how a system responds and lasts, more cost-effective methods of designing and testing models, and improved productivity. For informational and educational purposes, a videotape is being produced using both static and dynamic images from research institutions, software and hardware companies, private individuals, and historical photographs and drawings. The extensive number of CST resources indicates its widespread use. Applications run the gamut from simpler university-simulated problems to those requiring solutions on supercomputers. In some cases, an image or an animation will be mapped onto the actual structure to show the relevance of the computer model to the structure. computer image using traditional composition theories or video production requirements, often the image loses some of its original digital quality and impact when transferred to videotape. Although many CST images are currently available, those that are edited into the final project must meet two important criteria: they must complement the narration, and they must be broadcast quality when recorded on videotape.

  18. Infinite possibilities: Computational structures technology

    NASA Technical Reports Server (NTRS)

    Beam, Sherilee F.

    1994-01-01

    Computational Fluid Dynamics (or CFD) methods are very familiar to the research community. Even the general public has had some exposure to CFD images, primarily through the news media. However, very little attention has been paid to CST--Computational Structures Technology. Yet, no important design can be completed without it. During the first half of this century, researchers only dreamed of designing and building structures on a computer. Today their dreams have become practical realities as computational methods are used in all phases of design, fabrication and testing of engineering systems. Increasingly complex structures can now be built in even shorter periods of time. Over the past four decades, computer technology has been developing, and early finite element methods have grown from small in-house programs to numerous commercial software programs. When coupled with advanced computing systems, they help engineers make dramatic leaps in designing and testing concepts. The goals of CST include: predicting how a structure will behave under actual operating conditions; designing and complementing other experiments conducted on a structure; investigating microstructural damage or chaotic, unpredictable behavior; helping material developers in improving material systems; and being a useful tool in design systems optimization and sensitivity techniques. Applying CST to a structure problem requires five steps: (1) observe the specific problem; (2) develop a computational model for numerical simulation; (3) develop and assemble software and hardware for running the codes; (4) post-process and interpret the results; and (5) use the model to analyze and design the actual structure. Researchers in both industry and academia continue to make significant contributions to advance this technology with improvements in software, collaborative computing environments and supercomputing systems. As these environments and systems evolve, computational structures technology will evolve. By using CST in the design and operation of future structures systems, engineers will have a better understanding of how a system responds and lasts, more cost-effective methods of designing and testing models, and improved productivity. For informational and educational purposes, a videotape is being produced using both static and dynamic images from research institutions, software and hardware companies, private individuals, and historical photographs and drawings. The extensive number of CST resources indicates its widespread use. Applications run the gamut from simpler university-simulated problems to those requiring solutions on supercomputers. In some cases, an image or an animation will be mapped onto the actual structure to show the relevance of the computer model to the structure. Transferring the digital files to videotape presents a number of problems related to maintaining the quality of the original image, while still producing a broadcast quality videotape. Since researchers normally do not create a computer image using traditional composition theories or video production requirements, often the image loses some of its original digital quality and impact when transferred to videotape. Although many CST images are currently available, those that are edited into the final project must meet two important criteria: they must complement the narration, and they must be broadcast quality when recorded on videotape.

  19. Hard chaos, quantum billiards, and quantum dot computers

    SciTech Connect

    Mainieri, R.; Cvitanovic, P.; Hasslacher, B.

    1996-07-01

    This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Research was performed in analytic and computational techniques for dealing with hard chaos, especially the powerful tool of cycle expansions. This work has direct application to the understanding of electrons in nanodevices, such as junctions of quantum wires, or in arrays of dots or antidots. We developed a series of techniques for computing the properties of quantum systems with hard chaos, in particular the flow of electrons through nanodevices. These techniques are providing the insight and tools to design computers with nanoscale components. Recent efforts concentrated on understanding the effects of noise and orbit pruning in chaotic dynamical systems. We showed that most complicated chaotic systems (not just those equivalent to a finite shift) will develop branch points in their cycle expansion. Once the singularity is known to exist, it can be removed with a dramatic increase in the speed of convergence of quantities of physical interest.

  20. Quantum computational capability of a 2D valence bond solid phase

    SciTech Connect

    Miyake, Akimasa

    2011-07-15

    Highlights: > Our model is the 2D valence bond solid phase of a quantum antiferromagnet. > Universal quantum computation is processed by measurements of quantum correlations. > An intrinsic complexity of strongly-correlated quantum systems could be a resource. - Abstract: Quantum phases of naturally-occurring systems exhibit distinctive collective phenomena as manifestation of their many-body correlations, in contrast to our persistent technological challenge to engineer at will such strong correlations artificially. Here we show theoretically that quantum correlations exhibited in the 2D valence bond solid phase of a quantum antiferromagnet, modeled by Affleck, Kennedy, Lieb, and Tasaki (AKLT) as a precursor of spin liquids and topological orders, are sufficiently complex yet structured enough to simulate universal quantum computation when every single spin can be measured individually. This unveils that an intrinsic complexity of naturally-occurring 2D quantum systems-which has been a long-standing challenge for traditional computers-could be tamed as a computationally valuable resource, even if we are limited not to create newly entanglement during computation. Our constructive protocol leverages a novel way to herald the correlations suitable for deterministic quantum computation through a random sampling, and may be extensible to other ground states of various 2D valence bond phases beyond the AKLT state.

  1. Quantum computation over the butterfly network

    SciTech Connect

    Soeda, Akihito; Kinjo, Yoshiyuki; Turner, Peter S.; Murao, Mio

    2011-07-15

    In order to investigate distributed quantum computation under restricted network resources, we introduce a quantum computation task over the butterfly network where both quantum and classical communications are limited. We consider deterministically performing a two-qubit global unitary operation on two unknown inputs given at different nodes, with outputs at two distinct nodes. By using a particular resource setting introduced by M. Hayashi [Phys. Rev. A 76, 040301(R) (2007)], which is capable of performing a swap operation by adding two maximally entangled qubits (ebits) between the two input nodes, we show that unitary operations can be performed without adding any entanglement resource, if and only if the unitary operations are locally unitary equivalent to controlled unitary operations. Our protocol is optimal in the sense that the unitary operations cannot be implemented if we relax the specifications of any of the channels. We also construct protocols for performing controlled traceless unitary operations with a 1-ebit resource and for performing global Clifford operations with a 2-ebit resource.

  2. Hybrid architecture for encoded measurement-based quantum computation.

    PubMed

    Zwerger, M; Briegel, H J; Dr, W

    2014-01-01

    We present a hybrid scheme for quantum computation that combines the modular structure of elementary building blocks used in the circuit model with the advantages of a measurement-based approach to quantum computation. We show how to construct optimal resource states of minimal size to implement elementary building blocks for encoded quantum computation in a measurement-based way, including states for error correction and encoded gates. The performance of the scheme is determined by the quality of the resource states, where within the considered error model a threshold of the order of 10% local noise per particle for fault-tolerant quantum computation and quantum communication. PMID:24946906

  3. Hybrid architecture for encoded measurement-based quantum computation

    PubMed Central

    Zwerger, M.; Briegel, H. J.; Dr, W.

    2014-01-01

    We present a hybrid scheme for quantum computation that combines the modular structure of elementary building blocks used in the circuit model with the advantages of a measurement-based approach to quantum computation. We show how to construct optimal resource states of minimal size to implement elementary building blocks for encoded quantum computation in a measurement-based way, including states for error correction and encoded gates. The performance of the scheme is determined by the quality of the resource states, where within the considered error model a threshold of the order of 10% local noise per particle for fault-tolerant quantum computation and quantum communication. PMID:24946906

  4. Multiple-server Flexible Blind Quantum Computation in Networks

    NASA Astrophysics Data System (ADS)

    Kong, Xiaoqin; Li, Qin; Wu, Chunhui; Yu, Fang; He, Jinjun; Sun, Zhiyuan

    2016-02-01

    Blind quantum computation (BQC) can allow a client with limited quantum power to delegate his quantum computation to a powerful server and still keep his own data private. In this paper, we present a multiple-server flexible BQC protocol, where a client who only needs the ability of accessing qua ntum channels can delegate the computational task to a number of servers. Especially, the client's quantum computation also can be achieved even when one or more delegated quantum servers break down in networks. In other words, when connections to certain quantum servers are lost, clients can adjust flexibly and delegate their quantum computation to other servers. Obviously it is trivial that the computation will be unsuccessful if all servers are interrupted.

  5. Nonlocality as a benchmark for universal quantum computation in Ising anyon topological quantum computers

    NASA Astrophysics Data System (ADS)

    Howard, Mark; Vala, Jiri

    2012-02-01

    An obstacle affecting any proposal for a topological quantum computer based on Ising anyons is that quasiparticle braiding can only implement a finite (nonuniversal) set of quantum operations. The computational power of this restricted set of operations (often called stabilizer operations) has been studied in quantum information theory, and it is known that no quantum-computational advantage can be obtained without the help of an additional nonstabilizer operation. Similarly, a bipartite two-qubit system based on Ising anyons can not exhibit nonlocality (in the sense of violating a Bell inequality) when only topologically protected stabilizer operations are performed. To produce correlations that can not be described by a local hidden variable model again requires the use of a nonstabilizer operation. Using geometric techniques, we relate the sets of operations that enable universal quantum computing (UQC) with those that enable violation of a Bell inequality. Motivated by the fact that nonstabilizer operations are expected to be highly imperfect, our aim is to provide a benchmark for identifying UQC-enabling operations that is both experimentally practical and conceptually simple. We show that any (noisy) single-qubit nonstabilizer operation that, together with perfect stabilizer operations, enables violation of the simplest two-qubit Bell inequality, can also be used to enable UQC. This benchmarking requires finding the expectation values of two distinct Pauli measurements on each qubit of a bipartite system.

  6. Computer Access. Tech Use Guide: Using Computer Technology.

    ERIC Educational Resources Information Center

    Council for Exceptional Children, Reston, VA. Center for Special Education Technology.

    One of nine brief guides for special educators on using computer technology, this guide focuses on access including adaptations in input devices, output devices, and computer interfaces. Low technology devices include "no-technology" devices (usually modifications to existing devices), simple switches, and multiple switches. High technology input

  7. Computer technologies and institutional memory

    NASA Technical Reports Server (NTRS)

    Bell, Christopher; Lachman, Roy

    1989-01-01

    NASA programs for manned space flight are in their 27th year. Scientists and engineers who worked continuously on the development of aerospace technology during that period are approaching retirement. The resulting loss to the organization will be considerable. Although this problem is general to the NASA community, the problem was explored in terms of the institutional memory and technical expertise of a single individual in the Man-Systems division. The main domain of the expert was spacecraft lighting, which became the subject area for analysis in these studies. The report starts with an analysis of the cumulative expertise and institutional memory of technical employees of organizations such as NASA. A set of solutions to this problem are examined and found inadequate. Two solutions were investigated at length: hypertext and expert systems. Illustrative examples were provided of hypertext and expert system representation of spacecraft lighting. These computer technologies can be used to ameliorate the problem of the loss of invaluable personnel.

  8. Military engine computational structures technology

    NASA Technical Reports Server (NTRS)

    Thomson, Daniel E.

    1992-01-01

    Integrated High Performance Turbine Engine Technology Initiative (IHPTET) goals require a strong analytical base. Effective analysis of composite materials is critical to life analysis and structural optimization. Accurate life prediction for all material systems is critical. User friendly systems are also desirable. Post processing of results is very important. The IHPTET goal is to double turbine engine propulsion capability by the year 2003. Fifty percent of the goal will come from advanced materials and structures, the other 50 percent will come from increasing performance. Computer programs are listed.

  9. Minimal computational-space implementation of multiround quantum protocols

    SciTech Connect

    Bisio, Alessandro; D'Ariano, Giacomo Mauro; Perinotti, Paolo; Chiribella, Giulio

    2011-02-15

    A single-party strategy in a multiround quantum protocol can be implemented by sequential networks of quantum operations connected by internal memories. Here, we provide an efficient realization in terms of computational-space resources.

  10. QCWAVE - A Mathematica quantum computer simulation update

    NASA Astrophysics Data System (ADS)

    Tabakin, Frank; Juliá-Díaz, Bruno

    2011-08-01

    This Mathematica 7.0/8.0 package upgrades and extends the quantum computer simulation code called QDENSITY. Use of the density matrix was emphasized in QDENSITY, although that code was also applicable to a quantum state description. In the present version, the quantum state version is stressed and made amenable to future extensions to parallel computer simulations. The add-on QCWAVE extends QDENSITY in several ways. The first way is to describe the action of one, two and three-qubit quantum gates as a set of small (2×2, 4×4 or 8×8) matrices acting on the 2 amplitudes for a system of nq qubits. This procedure was described in our parallel computer simulation QCMPI and is reviewed here. The advantage is that smaller storage demands are made, without loss of speed, and that the procedure can take advantage of message passing interface (MPI) techniques, which will hopefully be generally available in future Mathematica versions. Another extension of QDENSITY provided here is a multiverse approach, as described in our QCMPI paper. This multiverse approach involves using the present slave-master parallel processing capabilities of Mathematica 7.0/8.0 to simulate errors and error correction. The basic idea is that parallel versions of QCWAVE run simultaneously with random errors introduced on some of the processors, with an ensemble average used to represent the real world situation. Within this approach, error correction steps can be simulated and their efficacy tested. This capability allows one to examine the detrimental effects of errors and the benefits of error correction on particular quantum algorithms. Other upgrades provided in this version include circuit-diagram drawing commands, better Dirac form and amplitude display features. These are included in the add-ons QCWave.m and Circuits.m, and are illustrated in tutorial notebooks. In separate notebooks, QCWAVE is applied to sample algorithms in which the parallel multiverse setup is illustrated and error correction is simulated. These extensions and upgrades will hopefully help in both instruction and in application to QC dynamics and error correction studies.

  11. Leadership Training in Computer Technology. [Resource Materials.

    ERIC Educational Resources Information Center

    American Speech-Language-Hearing Association, Rockville, MD.

    This manual contains papers written as part of a project to develop faculty leadership in the infusion of computer technology into graduate-level curricula in communication disorders. Titles and authors are (1) "Computer Technology in the Practice of Special Education: A General Introduction" (M. Budoff); (2)"Computer Technology in the Practice of

  12. Fast graph operations in quantum computation

    NASA Astrophysics Data System (ADS)

    Zhao, Liming; Pérez-Delgado, Carlos A.; Fitzsimons, Joseph F.

    2016-03-01

    The connection between certain entangled states and graphs has been heavily studied in the context of measurement-based quantum computation as a tool for understanding entanglement. Here we show that this correspondence can be harnessed in the reverse direction to yield a graph data structure, which allows for more efficient manipulation and comparison of graphs than any possible classical structure. We introduce efficient algorithms for many transformation and comparison operations on graphs represented as graph states, and prove that no classical data structure can have similar performance for the full set of operations studied.

  13. Computing with quantum knots: Marjorana modes, non-Abelian anyons, and topological quantum computation

    SciTech Connect

    Das Sarma, Sankar

    2012-10-03

    I will discuss the revolutionary new concept of topological quantum computation, which is fault-tolerant at the hardware level with no need, in principle, of any quantum error correction protocols. Errors simply do not occur since the physical qubits and the computation steps are protected against decoherence by non-local topological correlations in the underlying physical system. The key idea is non-Abelian statistics of the quasiparticles (called 'anyons' as opposed to fermions or bosons), where the space-time braiding of the anyons around each other, i.e. quantum 'knots', form topologically protected quantum gate operations. I will describe in detail the theoretical principles guiding the experimental search for the appropriate topological phases of matter where such non-Abelian anyons, which are low-dimensional solid state versions of the elusive and exotic Majorana fermions hypothesized seventy-five years ago, may exist. I will critically discuss the recent experimental claims of observing the Majorana modes in semiconductor nanowire structures following earlier theoretical proposals, outlining the future developments which would be necessary to eventually build a topological quantum computer.

  14. Modeling of quantum noise and the quality of hardware components of quantum computers

    NASA Astrophysics Data System (ADS)

    Bogdanov, Yu. I.; Chernyavskiy, A. Yu.; Holevo, Alexander; Lukichev, V. F.; Orlikovsky, A. A.

    2013-01-01

    In the present paper methods and algorithms of modeling quantum operations for quantum computer integrated circuits design are developed. The results of modeling of practically important quantum gates: controlled-NOT (CNOT), and controlled Z-transform (CZ) subject to different decoherence mechanisms are presented. These mechanisms include analysis of depolarizing quantum noise and processes of amplitude and phase relaxation.

  15. QDENSITY—A Mathematica Quantum Computer simulation

    NASA Astrophysics Data System (ADS)

    Juliá-Díaz, Bruno; Burdis, Joseph M.; Tabakin, Frank

    2006-06-01

    This Mathematica 5.2 package is a simulation of a Quantum Computer. The program provides a modular, instructive approach for generating the basic elements that make up a quantum circuit. The main emphasis is on using the density matrix, although an approach using state vectors is also implemented in the package. The package commands are defined in Qdensity.m which contains the tools needed in quantum circuits, e.g., multiqubit kets, projectors, gates, etc. Selected examples of the basic commands are presented here and a tutorial notebook, Tutorial.nb is provided with the package (available on our website) that serves as a full guide to the package. Finally, application is made to a variety of relevant cases, including Teleportation, Quantum Fourier transform, Grover's search and Shor's algorithm, in separate notebooks: QFT.nb, Teleportation.nb, Grover.nb and Shor.nb where each algorithm is explained in detail. Finally, two examples of the construction and manipulation of cluster states, which are part of "one way computing" ideas, are included as an additional tool in the notebook Cluster.nb. A Mathematica palette containing most commands in QDENSITY is also included: QDENSpalette.nb. Program summaryTitle of program: QDENSITY Catalogue identifier: ADXH_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADXH_v1_0 Program available from: CPC Program Library, Queen's University of Belfast, N. Ireland Operating systems: Any which supports Mathematica; tested under Microsoft Windows XP, Macintosh OS X, and Linux FC4 Programming language used: Mathematica 5.2 No. of bytes in distributed program, including test data, etc.: 180 581 No. of lines in distributed program, including test data, etc.: 19 382 Distribution format: tar.gz Method of solution: A Mathematica package is provided which contains commands to create and analyze quantum circuits. Several Mathematica notebooks containing relevant examples: Teleportation, Shor's Algorithm and Grover's search are explained in detail. A tutorial, Tutorial.nb is also enclosed. QDENSITY is available at http://www.pitt.edu/~tabakin/QDENSITY.

  16. Entertainment Computing, Social Transformation and the Quantum Field

    NASA Astrophysics Data System (ADS)

    Rauterberg, Matthias

    The abstract should summaritinment computing is on its way getting an established academic discipline. The scope of entertainment computing is quite broad (see the scope of the international journal Entertainment Computing). One unifying idea in this diverse community of entertainment researchers and developers might be a normative position to enhance human living through social transformation. One possible option in this direction is a shared ‘conscious’ field. Several ideas about a new kind of field based on quantum effects are presented and discussed. Assuming that social transformation is based on a shared collective unconscious I propose designing entertainment technology for a new kind of user experience that can transform in a positive manner the individual unconscious and therefore the collective unconscious as well. Our ALICE project can be seen as a first attempt in this direction.

  17. Algorithmic cooling and scalable NMR quantum computers

    PubMed Central

    Boykin, P. Oscar; Mor, Tal; Roychowdhury, Vwani; Vatan, Farrokh; Vrijen, Rutger

    2002-01-01

    We present here algorithmic cooling (via polarization heat bath)a powerful method for obtaining a large number of highly polarized spins in liquid nuclear-spin systems at finite temperature. Given that spin-half states represent (quantum) bits, algorithmic cooling cleans dirty bits beyond the Shannon's bound on data compression, by using a set of rapidly thermal-relaxing bits. Such auxiliary bits could be implemented by using spins that rapidly get into thermal equilibrium with the environment, e.g., electron spins. Interestingly, the interaction with the environment, usually a most undesired interaction, is used here to our benefit, allowing a cooling mechanism. Cooling spins to a very low temperature without cooling the environment could lead to a breakthrough in NMR experiments, and our spin-refrigerating method suggests that this is possible. The scaling of NMR ensemble computers is currently one of the main obstacles to building larger-scale quantum computing devices, and our spin-refrigerating method suggests that this problem can be resolved. PMID:11904402

  18. Algorithmic cooling and scalable NMR quantum computers.

    PubMed

    Boykin, P Oscar; Mor, Tal; Roychowdhury, Vwani; Vatan, Farrokh; Vrijen, Rutger

    2002-03-19

    We present here algorithmic cooling (via polarization heat bath)-a powerful method for obtaining a large number of highly polarized spins in liquid nuclear-spin systems at finite temperature. Given that spin-half states represent (quantum) bits, algorithmic cooling cleans dirty bits beyond the Shannon's bound on data compression, by using a set of rapidly thermal-relaxing bits. Such auxiliary bits could be implemented by using spins that rapidly get into thermal equilibrium with the environment, e.g., electron spins. Interestingly, the interaction with the environment, usually a most undesired interaction, is used here to our benefit, allowing a cooling mechanism. Cooling spins to a very low temperature without cooling the environment could lead to a breakthrough in NMR experiments, and our "spin-refrigerating" method suggests that this is possible. The scaling of NMR ensemble computers is currently one of the main obstacles to building larger-scale quantum computing devices, and our spin-refrigerating method suggests that this problem can be resolved. PMID:11904402

  19. Multiple network alignment on quantum computers

    NASA Astrophysics Data System (ADS)

    Daskin, Anmer; Grama, Ananth; Kais, Sabre

    2014-09-01

    Comparative analyses of graph structured datasets underly diverse problems. Examples of these problems include identification of conserved functional components (biochemical interactions) across species, structural similarity of large biomolecules, and recurring patterns of interactions in social networks. A large class of such analyses methods quantify the topological similarity of nodes across networks. The resulting correspondence of nodes across networks, also called node alignment, can be used to identify invariant subgraphs across the input graphs. Given $k$ graphs as input, alignment algorithms use topological information to assign a similarity score to each $k$-tuple of nodes, with elements (nodes) drawn from each of the input graphs. Nodes are considered similar if their neighbors are also similar. An alternate, equivalent view of these network alignment algorithms is to consider the Kronecker product of the input graphs, and to identify high-ranked nodes in the Kronecker product graph. Conventional methods such as PageRank and HITS (Hypertext Induced Topic Selection) can be used for this purpose. These methods typically require computation of the principal eigenvector of a suitably modified Kronecker product matrix of the input graphs. We adopt this alternate view of the problem to address the problem of multiple network alignment. Using the phase estimation algorithm, we show that the multiple network alignment problem can be efficiently solved on quantum computers. We characterize the accuracy and performance of our method, and show that it can deliver exponential speedups over conventional (non-quantum) methods.

  20. Multiple network alignment on quantum computers

    NASA Astrophysics Data System (ADS)

    Daskin, Anmer; Grama, Ananth; Kais, Sabre

    2014-12-01

    Comparative analyses of graph-structured datasets underly diverse problems. Examples of these problems include identification of conserved functional components (biochemical interactions) across species, structural similarity of large biomolecules, and recurring patterns of interactions in social networks. A large class of such analyses methods quantify the topological similarity of nodes across networks. The resulting correspondence of nodes across networks, also called node alignment, can be used to identify invariant subgraphs across the input graphs. Given graphs as input, alignment algorithms use topological information to assign a similarity score to each -tuple of nodes, with elements (nodes) drawn from each of the input graphs. Nodes are considered similar if their neighbors are also similar. An alternate, equivalent view of these network alignment algorithms is to consider the Kronecker product of the input graphs and to identify high-ranked nodes in the Kronecker product graph. Conventional methods such as PageRank and HITS (Hypertext-Induced Topic Selection) can be used for this purpose. These methods typically require computation of the principal eigenvector of a suitably modified Kronecker product matrix of the input graphs. We adopt this alternate view of the problem to address the problem of multiple network alignment. Using the phase estimation algorithm, we show that the multiple network alignment problem can be efficiently solved on quantum computers. We characterize the accuracy and performance of our method and show that it can deliver exponential speedups over conventional (non-quantum) methods.

  1. Center for Computational Structures Technology

    NASA Technical Reports Server (NTRS)

    Noor, Ahmed K.; Perry, Ferman W.

    1995-01-01

    The Center for Computational Structures Technology (CST) is intended to serve as a focal point for the diverse CST research activities. The CST activities include the use of numerical simulation and artificial intelligence methods in modeling, analysis, sensitivity studies, and optimization of flight-vehicle structures. The Center is located at NASA Langley and is an integral part of the School of Engineering and Applied Science of the University of Virginia. The key elements of the Center are: (1) conducting innovative research on advanced topics of CST; (2) acting as pathfinder by demonstrating to the research community what can be done (high-potential, high-risk research); (3) strong collaboration with NASA scientists and researchers from universities and other government laboratories; and (4) rapid dissemination of CST to industry, through integration of industrial personnel into the ongoing research efforts.

  2. Measurement-only topological quantum computation via anyonic interferometry

    SciTech Connect

    Bonderson, Parsa Freedman, Michael Nayak, Chetan

    2009-04-15

    We describe measurement-only topological quantum computation using both projective and interferometrical measurement of topological charge. We demonstrate how anyonic teleportation can be achieved using 'forced measurement' protocols for both types of measurement. Using this, it is shown how topological charge measurements can be used to generate the braiding transformations used in topological quantum computation, and hence that the physical transportation of computational anyons is unnecessary. We give a detailed discussion of the anyonics for implementation of topological quantum computation (particularly, using the measurement-only approach) in fractional quantum Hall systems.

  3. Quantum optics: Cool computation, hot bits

    NASA Astrophysics Data System (ADS)

    Lloyd, Seth

    2014-02-01

    Quantum information processing provides novel methods for pumping heat and refrigerating photons. Devices that obtain and manipulate information at the quantum level can function as quantum 'Maxwell's demons' to cool systems in ways that liquid helium cannot.

  4. Cryogenic Control Architecture for Large-Scale Quantum Computing

    NASA Astrophysics Data System (ADS)

    Hornibrook, J. M.; Colless, J. I.; Conway Lamb, I. D.; Pauka, S. J.; Lu, H.; Gossard, A. C.; Watson, J. D.; Gardner, G. C.; Fallahi, S.; Manfra, M. J.; Reilly, D. J.

    2015-02-01

    Solid-state qubits have recently advanced to the level that enables them, in principle, to be scaled up into fault-tolerant quantum computers. As these physical qubits continue to advance, meeting the challenge of realizing a quantum machine will also require the development of new supporting devices and control architectures with complexity far beyond the systems used in today's few-qubit experiments. Here, we report a microarchitecture for controlling and reading out qubits during the execution of a quantum algorithm such as an error-correcting code. We demonstrate the basic principles of this architecture using a cryogenic switch matrix implemented via high-electron-mobility transistors and a new kind of semiconductor device based on gate-switchable capacitance. The switch matrix is used to route microwave waveforms to qubits under the control of a field-programmable gate array, also operating at cryogenic temperatures. Taken together, these results suggest a viable approach for controlling large-scale quantum systems using semiconductor technology.

  5. Quantum computation of multifractal exponents through the quantum wavelet transform

    SciTech Connect

    Garcia-Mata, Ignacio; Giraud, Olivier; Georgeot, Bertrand

    2009-05-15

    We study the use of the quantum wavelet transform to extract efficiently information about the multifractal exponents for multifractal quantum states. We show that, combined with quantum simulation algorithms, it enables to build quantum algorithms for multifractal exponents with a polynomial gain compared to classical simulations. Numerical results indicate that a rough estimate of fractality could be obtained exponentially fast. Our findings are relevant, e.g., for quantum simulations of multifractal quantum maps and of the Anderson model at the metal-insulator transition.

  6. Preparing Projected Entangled Pair States on a Quantum Computer

    NASA Astrophysics Data System (ADS)

    Schwarz, Martin; Temme, Kristan; Verstraete, Frank

    2012-03-01

    We present a quantum algorithm to prepare injective projected entangled pair states (PEPS) on a quantum computer, a class of open tensor networks representing quantum states. The run time of our algorithm scales polynomially with the inverse of the minimum condition number of the PEPS projectors and, essentially, with the inverse of the spectral gap of the PEPSs parent Hamiltonian.

  7. Art and Technology: Computers in the Studio?

    ERIC Educational Resources Information Center

    Ruby-Baird, Janet

    1997-01-01

    Because the graphic industry demands graduates with computer skills, art students want college programs that include complex computer technologies. However, students can produce good computer art only if they have mastered traditional drawing and design skills. Discusses designing an art curriculum including both technology and traditional course

  8. Advanced laptop and small personal computer technology

    NASA Technical Reports Server (NTRS)

    Johnson, Roger L.

    1991-01-01

    Advanced laptop and small personal computer technology is presented in the form of the viewgraphs. The following areas of hand carried computers and mobile workstation technology are covered: background, applications, high end products, technology trends, requirements for the Control Center application, and recommendations for the future.

  9. QCMPI: A parallel environment for quantum computing

    NASA Astrophysics Data System (ADS)

    Tabakin, Frank; Juli-Daz, Bruno

    2009-06-01

    QCMPI is a quantum computer (QC) simulation package written in Fortran 90 with parallel processing capabilities. It is an accessible research tool that permits rapid evaluation of quantum algorithms for a large number of qubits and for various "noise" scenarios. The prime motivation for developing QCMPI is to facilitate numerical examination of not only how QC algorithms work, but also to include noise, decoherence, and attenuation effects and to evaluate the efficacy of error correction schemes. The present work builds on an earlier Mathematica code QDENSITY, which is mainly a pedagogic tool. In that earlier work, although the density matrix formulation was featured, the description using state vectors was also provided. In QCMPI, the stress is on state vectors, in order to employ a large number of qubits. The parallel processing feature is implemented by using the Message-Passing Interface (MPI) protocol. A description of how to spread the wave function components over many processors is provided, along with how to efficiently describe the action of general one- and two-qubit operators on these state vectors. These operators include the standard Pauli, Hadamard, CNOT and CPHASE gates and also Quantum Fourier transformation. These operators make up the actions needed in QC. Codes for Grover's search and Shor's factoring algorithms are provided as examples. A major feature of this work is that concurrent versions of the algorithms can be evaluated with each version subject to alternate noise effects, which corresponds to the idea of solving a stochastic Schrdinger equation. The density matrix for the ensemble of such noise cases is constructed using parallel distribution methods to evaluate its eigenvalues and associated entropy. Potential applications of this powerful tool include studies of the stability and correction of QC processes using Hamiltonian based dynamics. Program summaryProgram title: QCMPI Catalogue identifier: AECS_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AECS_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 4866 No. of bytes in distributed program, including test data, etc.: 42 114 Distribution format: tar.gz Programming language: Fortran 90 and MPI Computer: Any system that supports Fortran 90 and MPI Operating system: developed and tested at the Pittsburgh Supercomputer Center, at the Barcelona Supercomputer (BSC/CNS) and on multi-processor Macs and PCs. For cases where distributed density matrix evaluation is invoked, the BLACS and SCALAPACK packages are needed. Has the code been vectorized or parallelized?: Yes Classification: 4.15 External routines: LAPACK, SCALAPACK, BLACS Nature of problem: Analysis of quantum computation algorithms and the effects of noise. Solution method: A Fortran 90/MPI package is provided that contains modular commands to create and analyze quantum circuits. Shor's factorization and Grover's search algorithms are explained in detail. Procedures for distributing state vector amplitudes over processors and for solving concurrent (multiverse) cases with noise effects are implemented. Density matrix and entropy evaluations are provided in both single and parallel versions. Running time: Test run takes less than 1 minute using 2 processors.

  10. Heterotic quantum and classical computing on convergence spaces

    NASA Astrophysics Data System (ADS)

    Patten, D. R.; Jakel, D. W.; Irwin, R. J.; Blair, H. A.

    2015-05-01

    Category-theoretic characterizations of heterotic models of computation, introduced by Stepney et al., combine computational models such as classical/quantum, digital/analog, synchronous/asynchronous, etc. to obtain increased computational power. A highly informative classical/quantum heterotic model of computation is represented by Abramsky's simple sequential imperative quantum programming language which extends the classical simple imperative programming language to encompass quantum computation. The mathematical (denotational) semantics of this classical language serves as a basic foundation upon which formal verification methods can be developed. We present a more comprehensive heterotic classical/quantum model of computation based on heterotic dynamical systems on convergence spaces. Convergence spaces subsume topological spaces but admit finer structure from which, in prior work, we obtained differential calculi in the cartesian closed category of convergence spaces allowing us to define heterotic dynamical systems, given by coupled systems of first order differential equations whose variables are functions from the reals to convergence spaces.

  11. Quantum computing with magnetically interacting atoms

    SciTech Connect

    Derevianko, Andrei; Cannon, Caleb C.

    2004-12-01

    We propose a scalable quantum-computing architecture based on cold atoms confined to sites of a tight optical lattice. The lattice is placed in a nonuniform magnetic field and the resulting Zeeman sublevels define qubit states. Microwave pulses tuned to space-dependent resonant frequencies are used for individual addressing. The atoms interact via magnetic-dipole interactions allowing implementation of a universal controlled-NOT gate. The resulting gate operation times for alkalis-metals are on the order of milliseconds, much faster then the anticipated decoherence times. Single qubit operations take about 10 {mu}s. Analysis of motional decoherence due to NOT operations is given. We also comment on the improved feasibility of the proposed architecture with complex open-shell atoms, such as Cr, Eu, and metastable alkaline-earth atoms with larger magnetic moments.

  12. Trapped Ion Quantum Computation by Adiabatic Passage

    SciTech Connect

    Feng Xuni; Wu Chunfeng; Lai, C. H.; Oh, C. H.

    2008-11-07

    We propose a new universal quantum computation scheme for trapped ions in thermal motion via the technique of adiabatic passage, which incorporates the advantages of both the adiabatic passage and the model of trapped ions in thermal motion. Our scheme is immune from the decoherence due to spontaneous emission from excited states as the system in our scheme evolves along a dark state. In our scheme the vibrational degrees of freedom are not required to be cooled to their ground states because they are only virtually excited. It is shown that the fidelity of the resultant gate operation is still high even when the magnitude of the effective Rabi frequency moderately deviates from the desired value.

  13. Optical quantum computation with perpetually coupled spins

    SciTech Connect

    Benjamin, Simon C.; Reina, John H.; Lovett, Brendon W.

    2004-12-01

    The possibility of using strongly and continuously interacting spins for quantum computation has recently been discussed. Here we present a simple optical scheme that achieves this goal while avoiding the drawbacks of earlier proposals. We employ a third state, accessed by a classical laser field, to create an effective barrier to information transfer. The mechanism proves to be highly efficient both for continuous and pulsed laser modes; moreover, it is very robust, tolerating high decay rates for the excited states. The approach is applicable to a broad range of systems, in particular, dense structures such as solid-state self-assembled (e.g., molecular) devices. Importantly, there are existing structures upon which 'first-step' experiments could be immediately performed.

  14. Applications of superconducting circuits to quantum computing

    NASA Astrophysics Data System (ADS)

    Wilhelm, Frank

    2014-03-01

    Superconducting circuits containing Josephson junctions are strong contenders for the implementation of a quantum computer. At its 15 year mark, the field has seen tremendous progress with an increase of coherence by six orders of magnitude and it is now taking off from the few- to the multi-qubit level. I will present highlights of research on the level of single devices, in particular the strong increase of coherence that counter-intuitively comes with a growth in device size, as well as readout. I will cover challenges related to multi-qubit systems focusing on precise multi-qubit control and calibration, and present an outlook on future architectures dictated by the requirements of fault tolerance.

  15. Number Partitioning via Quantum Adiabatic Computation

    NASA Technical Reports Server (NTRS)

    Smelyanskiy, Vadim N.; Toussaint, Udo; Clancy, Daniel (Technical Monitor)

    2002-01-01

    We study both analytically and numerically the complexity of the adiabatic quantum evolution algorithm applied to random instances of combinatorial optimization problems. We use as an example the NP-complete set partition problem and obtain an asymptotic expression for the minimal gap separating the ground and exited states of a system during the execution of the algorithm. We show that for computationally hard problem instances the size of the minimal gap scales exponentially with the problem size. This result is in qualitative agreement with the direct numerical simulation of the algorithm for small instances of the set partition problem. We describe the statistical properties of the optimization problem that are responsible for the exponential behavior of the algorithm.

  16. Analog quantum computing (AQC) by revisiting the underlying physics

    NASA Astrophysics Data System (ADS)

    Werbos, Paul J.

    2015-05-01

    It has been proven that universal quantum computers based on qubits and classical analog networks both have superTuring capabilities. It is a grand challenge to computer science to prove that the combination of the two, in analog (continuous variable) quantum computing, offers supersuperTuring capability, the best we can achieve. Computing with continuous spins is now the most promising path AQC. Two papers at SPIE2014 described unbreakable quantum codes using continuous spins beyond what traditional qubits allow. To make this real, we must first develop a realistic ability to model and predict the behavior of networks of spin gates which act in part as polarizers. Last year I proposed a triphoton experiment, where three entangled photons go to linear polarizers set to angles θa, θb and θc. Assuming a "collapse of the wave function" yields predictions for the coincidence detection rate, R3/R0(θa, θb, θc) significantly different from the prediction of a new family of models based on classical Markov Random Fields (MRF) across space time, even though both yield the same correct prediction in the two-photon case. We cannot expect to predict systems of 100 entangled photons correctly if we cannot even predict three yet. Yanhua Shih is currently performing this experiment, as a first step to demonstrating a new technology to produce 100 entangled photons (collaborating with Scully) and understanding larger systems. I have also developed continuous-time versions of the MRF models and of "collapse of the wave function", so as to eliminate the need to assume metaphysical observers in general.

  17. Gate sequence for continuous variable one-way quantum computation

    PubMed Central

    Su, Xiaolong; Hao, Shuhong; Deng, Xiaowei; Ma, Lingyu; Wang, Meihong; Jia, Xiaojun; Xie, Changde; Peng, Kunchi

    2013-01-01

    Measurement-based one-way quantum computation using cluster states as resources provides an efficient model to perform computation and information processing of quantum codes. Arbitrary Gaussian quantum computation can be implemented sufficiently by long single-mode and two-mode gate sequences. However, continuous variable gate sequences have not been realized so far due to an absence of cluster states larger than four submodes. Here we present the first continuous variable gate sequence consisting of a single-mode squeezing gate and a two-mode controlled-phase gate based on a six-mode cluster state. The quantum property of this gate sequence is confirmed by the fidelities and the quantum entanglement of two output modes, which depend on both the squeezing and controlled-phase gates. The experiment demonstrates the feasibility of implementing Gaussian quantum computation by means of accessible gate sequences.

  18. Quantum computational tensor network on string-net condensate

    NASA Astrophysics Data System (ADS)

    Morimae, Tomoyuki

    2012-06-01

    String-net condensate is a new class of materials which exhibits quantum topological order. Here we study the measurement-based quantum computation on the simplest example of string-net condensate, namely the Z2 gauge string-net condensate on the two-dimensional hexagonal lattice, by using the framework of quantum computational tensor network. We show that universal measurement-based quantum computation is possible by coupling two correlation space wires with a physical two-body interaction. We also show that universal measurement-based quantum computation is possible solely with single-qubit measurements if the sign of the coefficient of each closed-loop configuration in the state is tuned. These results suggest that even the simplest example of string-net condensate is equipped with the correlation space that has the capacity for the application to quantum information processing.

  19. Preparing ground states of quantum many-body systems on a quantum computer

    NASA Astrophysics Data System (ADS)

    Poulin, David

    2009-03-01

    The simulation of quantum many-body systems is a notoriously hard problem in condensed matter physics, but it could easily be handled by a quantum computer [4,1]. There is however one catch: while a quantum computer can naturally implement the dynamics of a quantum system --- i.e. solve Schr"odinger's equation --- there was until now no general method to initialize the computer in a low-energy state of the simulated system. We present a quantum algorithm [5] that can prepare the ground state and thermal states of a quantum many-body system in a time proportional to the square-root of its Hilbert space dimension. This is the same scaling as required by the best known algorithm to prepare the ground state of a classical many-body system on a quantum computer [3,2]. This provides strong evidence that for a quantum computer, preparing the ground state of a quantum system is in the worst case no more difficult than preparing the ground state of a classical system. 1 D. Aharonov and A. Ta-Shma, Adiabatic quantum state generation and statistical zero knowledge, Proc. 35th Annual ACM Symp. on Theo. Comp., (2003), p. 20. F. Barahona, On the computational complexity of ising spin glass models, J. Phys. A. Math. Gen., 15 (1982), p. 3241. C. H. Bennett, E. Bernstein, G. Brassard, and U. Vazirani, Strengths and weaknessess of quantum computing, SIAM J. Comput., 26 (1997), pp. 1510--1523, quant-ph/9701001. S. Lloyd, Universal quantum simulators, Science, 273 (1996), pp. 1073--1078. D. Poulin and P. Wocjan, Preparing ground states of quantum many-body systems on a quantum computer, 2008, arXiv:0809.2705.

  20. The Brain Is both Neurocomputer and Quantum Computer

    ERIC Educational Resources Information Center

    Hameroff, Stuart R.

    2007-01-01

    In their article, "Is the Brain a Quantum Computer,?" Litt, Eliasmith, Kroon, Weinstein, and Thagard (2006) criticize the Penrose-Hameroff "Orch OR" quantum computational model of consciousness, arguing instead for neurocomputation as an explanation for mental phenomena. Here I clarify and defend Orch OR, show how Orch OR and neurocomputation are

  1. The Brain Is both Neurocomputer and Quantum Computer

    ERIC Educational Resources Information Center

    Hameroff, Stuart R.

    2007-01-01

    In their article, "Is the Brain a Quantum Computer,?" Litt, Eliasmith, Kroon, Weinstein, and Thagard (2006) criticize the Penrose-Hameroff "Orch OR" quantum computational model of consciousness, arguing instead for neurocomputation as an explanation for mental phenomena. Here I clarify and defend Orch OR, show how Orch OR and neurocomputation are…

  2. Computer Technology: State of the Art.

    ERIC Educational Resources Information Center

    Withington, Frederic G.

    1981-01-01

    Describes the nature of modern general-purpose computer systems, including hardware, semiconductor electronics, microprocessors, computer architecture, input output technology, and system control programs. Seven suggested readings are cited. (FM)

  3. Fault-tolerant quantum computation via exchange interactions.

    PubMed

    Mohseni, Masoud; Lidar, Daniel A

    2005-02-01

    Quantum computation can be performed by encoding logical qubits into the states of two or more physical qubits, and control of effective exchange interactions and possibly a global magnetic field. This "encoded universality" paradigm offers potential simplifications in quantum computer design since it does away with the need to control physical qubits individually. Here we show how encoded universality schemes can be combined with fault-tolerant quantum error correction, thus establishing the scalability of such schemes. PMID:15783544

  4. Dynamically error-corrected gates for universal quantum computation.

    PubMed

    Khodjasteh, Kaveh; Viola, Lorenza

    2009-02-27

    Scalable quantum computation in realistic devices requires that precise control can be implemented efficiently in the presence of decoherence and operational errors. We propose a general constructive procedure for designing robust unitary gates on an open quantum system without encoding or measurement overhead. Our results allow for a low-level error correction strategy solely based on Hamiltonian engineering using realistic bounded-strength controls and may substantially reduce implementation requirements for fault-tolerant quantum computing architectures. PMID:19257727

  5. Effective Fault-Tolerant Quantum Computation with Slow Measurements

    SciTech Connect

    DiVincenzo, David P.; Aliferis, Panos

    2007-01-12

    How important is fast measurement for fault-tolerant quantum computation? Using a combination of existing and new ideas, we argue that measurement times as long as even 1000 gate times or more have a very minimal effect on the quantum accuracy threshold. This shows that slow measurement, which appears to be unavoidable in many implementations of quantum computing, poses no essential obstacle to scalability.

  6. Scalable quantum computation via local control of only two qubits

    SciTech Connect

    Burgarth, Daniel; Maruyama, Koji; Murphy, Michael; Montangero, Simone; Calarco, Tommaso; Nori, Franco; Plenio, Martin B.

    2010-04-15

    We apply quantum control techniques to a long spin chain by acting only on two qubits at one of its ends, thereby implementing universal quantum computation by a combination of quantum gates on these qubits and indirect swap operations across the chain. It is shown that the control sequences can be computed and implemented efficiently. We discuss the application of these ideas to physical systems such as superconducting qubits in which full control of long chains is challenging.

  7. Non-Abelian anyons and topological quantum computation

    NASA Astrophysics Data System (ADS)

    Nayak, Chetan; Simon, Steven H.; Stern, Ady; Freedman, Michael; Das Sarma, Sankar

    2008-07-01

    Topological quantum computation has emerged as one of the most exciting approaches to constructing a fault-tolerant quantum computer. The proposal relies on the existence of topological states of matter whose quasiparticle excitations are neither bosons nor fermions, but are particles known as non-Abelian anyons, meaning that they obey non-Abelian braiding statistics. Quantum information is stored in states with multiple quasiparticles, which have a topological degeneracy. The unitary gate operations that are necessary for quantum computation are carried out by braiding quasiparticles and then measuring the multiquasiparticle states. The fault tolerance of a topological quantum computer arises from the nonlocal encoding of the quasiparticle states, which makes them immune to errors caused by local perturbations. To date, the only such topological states thought to have been found in nature are fractional quantum Hall states, most prominently the ?=5/2 state, although several other prospective candidates have been proposed in systems as disparate as ultracold atoms in optical lattices and thin-film superconductors. In this review article, current research in this field is described, focusing on the general theoretical concepts of non-Abelian statistics as it relates to topological quantum computation, on understanding non-Abelian quantum Hall states, on proposed experiments to detect non-Abelian anyons, and on proposed architectures for a topological quantum computer. Both the mathematical underpinnings of topological quantum computation and the physics of the subject are addressed, using the ?=5/2 fractional quantum Hall state as the archetype of a non-Abelian topological state enabling fault-tolerant quantum computation.

  8. Parallel Photonic Quantum Computation Assisted by Quantum Dots in One-Side Optical Microcavities

    PubMed Central

    Luo, Ming-Xing; Wang, Xiaojun

    2014-01-01

    Universal quantum logic gates are important elements for a quantum computer. In contrast to previous constructions on one degree of freedom (DOF) of quantum systems, we investigate the possibility of parallel quantum computations dependent on two DOFs of photon systems. We construct deterministic hyper-controlled-not (hyper-CNOT) gates operating on the spatial-mode and the polarization DOFs of two-photon or one-photon systems by exploring the giant optical circular birefringence induced by quantum-dot spins in one-sided optical microcavities. These hyper-CNOT gates show that the quantum states of two DOFs can be viewed as independent qubits without requiring auxiliary DOFs in theory. This result can reduce the quantum resources by half for quantum applications with large qubit systems, such as the quantum Shor algorithm. PMID:25030424

  9. Parallel photonic quantum computation assisted by quantum dots in one-side optical microcavities.

    PubMed

    Luo, Ming-Xing; Wang, Xiaojun

    2014-01-01

    Universal quantum logic gates are important elements for a quantum computer. In contrast to previous constructions on one degree of freedom (DOF) of quantum systems, we investigate the possibility of parallel quantum computations dependent on two DOFs of photon systems. We construct deterministic hyper-controlled-not (hyper-CNOT) gates operating on the spatial-mode and the polarization DOFs of two-photon or one-photon systems by exploring the giant optical circular birefringence induced by quantum-dot spins in one-sided optical microcavities. These hyper-CNOT gates show that the quantum states of two DOFs can be viewed as independent qubits without requiring auxiliary DOFs in theory. This result can reduce the quantum resources by half for quantum applications with large qubit systems, such as the quantum Shor algorithm. PMID:25030424

  10. On the way to creation of materials for quantum computers

    NASA Astrophysics Data System (ADS)

    Aldoshin, Sergei M.; Zenchuk, A. I.; Fel'dman, Eduard B.; Yurishchev, M. A.

    2012-02-01

    General requirements for the materials for systems and devices whose operation is based on quantum correlations are discussed. The fluctuation theory of quantum entanglement is outlined. This theory allows one to estimate the size of the region of weak fluctuations of quantum entanglement for spin dimers in various materials. The concept of quantum discord as a measure of pure quantum correlations is outlined. Quantum correlations in polycrystalline samples of binuclear nitrosyl iron complexes were estimated from the temperature dependences of the magnetic susceptibilities. Particular attention is paid to calculations of the temperature corresponding to the emergence of quantum entanglement. Methods for increasing this temperature are discussed. The problem of the quantum information transmission as well as the future development of quantum technology is considered. The bibliography includes 120 references.

  11. An Atomic Abacus: Trapped ion quantum computing experiments at NIST

    NASA Astrophysics Data System (ADS)

    Demarco, Brian

    2003-03-01

    Trapped atomic ions are an ideal system for exploring quantum information science because deterministic state preparation and efficient state detection are possible and coherent manipulation of atomic systems is relatively advanced. In our experiment, a few singly charged Be ions are confined by static and radio-frequency electric fields in a micro-machined linear Paul trap. The internal and motional states of the ions are coherently manipulated using applied laser light. Our current work focuses on demonstrating the necessary ingredients to produce a scalable quantum computing scheme and on simplifying and improving quantum logic gates. I will speak about a new set of experiments that was made possible by recent improvements in trap technology. A novel trap with multiple trapping regions was used to demonstrate the first steps towards a fully scalable quantum computing scheme. Single ions were ``shuttled" between trapping regions without disturbing the ion's motional and internal state, and two ions were separated from a single to two different trapping zones. Improvements in the trap manufacturing process has led to a reduction of nearly two orders of magnitude in the ion's motional heating rate, making possible two new improved logic gates. The first gate utilizes the wave-packet nature of the ions to tune the laser-atom interaction and achieve a controlled-NOT gate between a single ion's spin and motional states. The second, a two-ion phase gate, uses phase-space dynamics to produce a state-sensitive geometric phase. I will end with a quick look at experiments using a Mg ion to sympathetically cool a simultaneously trapped Be ion and a glimpse of the next generation of ions traps currently under construction.

  12. Nanoscale phosphorus atom arrays created using STM for the fabrication of a silicon based quantum computer.

    SciTech Connect

    O'Brien, J. L.; Schofield, S. R.; Simmons, M. Y.; Clark, R. G.; Dzurak, A. S.; Curson, N. J.; Kane, B. E.; McAlpine, N. S.; Hawley, M. E.; Brown, G. W.

    2001-01-01

    Quantum computers offer the promise of formidable computational power for certain tasks. Of the various possible physical implementations of such a device, silicon based architectures are attractive for their scalability and ease of integration with existing silicon technology. These designs use either the electron or nuclear spin state of single donor atoms to store quantum information. Here we describe a strategy to fabricate an array of single phosphorus atoms in silicon for the construction of such a silicon based quantum computer. We demonstrate the controlled placement of single phosphorus bearing molecules on a silicon surface. This has been achieved by patterning a hydrogen mono-layer 'resist' with a scanning tunneling microscope (STM) tip and exposing the patterned surface to phosphine (PH3) molecules. We also describe preliminary studies into a process to incorporate these surface phosphorus atoms into the silicon crystal at the array sites. Keywords: Quantum computing, nanotechriology scanning turincling microscopy, hydrogen lithography

  13. Quantum Monte Carlo Endstation for Petascale Computing

    SciTech Connect

    Lubos Mitas

    2011-01-26

    NCSU research group has been focused on accomplising the key goals of this initiative: establishing new generation of quantum Monte Carlo (QMC) computational tools as a part of Endstation petaflop initiative for use at the DOE ORNL computational facilities and for use by computational electronic structure community at large; carrying out high accuracy quantum Monte Carlo demonstration projects in application of these tools to the forefront electronic structure problems in molecular and solid systems; expanding the impact of QMC methods and approaches; explaining and enhancing the impact of these advanced computational approaches. In particular, we have developed quantum Monte Carlo code (QWalk, www.qwalk.org) which was significantly expanded and optimized using funds from this support and at present became an actively used tool in the petascale regime by ORNL researchers and beyond. These developments have been built upon efforts undertaken by the PI's group and collaborators over the period of the last decade. The code was optimized and tested extensively on a number of parallel architectures including petaflop ORNL Jaguar machine. We have developed and redesigned a number of code modules such as evaluation of wave functions and orbitals, calculations of pfaffians and introduction of backflow coordinates together with overall organization of the code and random walker distribution over multicore architectures. We have addressed several bottlenecks such as load balancing and verified efficiency and accuracy of the calculations with the other groups of the Endstation team. The QWalk package contains about 50,000 lines of high quality object-oriented C++ and includes also interfaces to data files from other conventional electronic structure codes such as Gamess, Gaussian, Crystal and others. This grant supported PI for one month during summers, a full-time postdoc and partially three graduate students over the period of the grant duration, it has resulted in 13 published papers, 15 invited talks and lectures nationally and internationally. My former graduate student and postdoc Dr. Michal Bajdich, who was supported byt this grant, is currently a postdoc with ORNL in the group of Dr. F. Reboredo and Dr. P. Kent and is using the developed tools in a number of DOE projects. The QWalk package has become a truly important research tool used by the electronic structure community and has attracted several new developers in other research groups. Our tools use several types of correlated wavefunction approaches, variational, diffusion and reptation methods, large-scale optimization methods for wavefunctions and enables to calculate energy differences such as cohesion, electronic gaps, but also densities and other properties, using multiple runs one can obtain equations of state for given structures and beyond. Our codes use efficient numerical and Monte Carlo strategies (high accuracy numerical orbitals, multi-reference wave functions, highly accurate correlation factors, pairing orbitals, force biased and correlated sampling Monte Carlo), are robustly parallelized and enable to run on tens of thousands cores very efficiently. Our demonstration applications were focused on the challenging research problems in several fields of materials science such as transition metal solids. We note that our study of FeO solid was the first QMC calculation of transition metal oxides at high pressures.

  14. Moral Responsibility and Computer Technology.

    ERIC Educational Resources Information Center

    Friedman, Batya

    Noting a recent increase in the number of cases of computer crime and computer piracy, this paper takes up the question, "How can understanding the social context of computing help us--as parents, educators, and members of government and industry--to educate young people to become morally responsible members of an electronic information…

  15. Secure Multiparty Quantum Computation for Summation and Multiplication.

    PubMed

    Shi, Run-Hua; Mu, Yi; Zhong, Hong; Cui, Jie; Zhang, Shun

    2016-01-01

    As a fundamental primitive, Secure Multiparty Summation and Multiplication can be used to build complex secure protocols for other multiparty computations, specially, numerical computations. However, there is still lack of systematical and efficient quantum methods to compute Secure Multiparty Summation and Multiplication. In this paper, we present a novel and efficient quantum approach to securely compute the summation and multiplication of multiparty private inputs, respectively. Compared to classical solutions, our proposed approach can ensure the unconditional security and the perfect privacy protection based on the physical principle of quantum mechanics. PMID:26792197

  16. Secure Multiparty Quantum Computation for Summation and Multiplication

    NASA Astrophysics Data System (ADS)

    Shi, Run-Hua; Mu, Yi; Zhong, Hong; Cui, Jie; Zhang, Shun

    2016-01-01

    As a fundamental primitive, Secure Multiparty Summation and Multiplication can be used to build complex secure protocols for other multiparty computations, specially, numerical computations. However, there is still lack of systematical and efficient quantum methods to compute Secure Multiparty Summation and Multiplication. In this paper, we present a novel and efficient quantum approach to securely compute the summation and multiplication of multiparty private inputs, respectively. Compared to classical solutions, our proposed approach can ensure the unconditional security and the perfect privacy protection based on the physical principle of quantum mechanics.

  17. Secure Multiparty Quantum Computation for Summation and Multiplication

    PubMed Central

    Shi, Run-hua; Mu, Yi; Zhong, Hong; Cui, Jie; Zhang, Shun

    2016-01-01

    As a fundamental primitive, Secure Multiparty Summation and Multiplication can be used to build complex secure protocols for other multiparty computations, specially, numerical computations. However, there is still lack of systematical and efficient quantum methods to compute Secure Multiparty Summation and Multiplication. In this paper, we present a novel and efficient quantum approach to securely compute the summation and multiplication of multiparty private inputs, respectively. Compared to classical solutions, our proposed approach can ensure the unconditional security and the perfect privacy protection based on the physical principle of quantum mechanics. PMID:26792197

  18. Experimental magic state distillation for fault-tolerant quantum computing.

    PubMed

    Souza, Alexandre M; Zhang, Jingfu; Ryan, Colm A; Laflamme, Raymond

    2011-01-25

    Any physical quantum device for quantum information processing (QIP) is subject to errors in implementation. In order to be reliable and efficient, quantum computers will need error-correcting or error-avoiding methods. Fault-tolerance achieved through quantum error correction will be an integral part of quantum computers. Of the many methods that have been discovered to implement it, a highly successful approach has been to use transversal gates and specific initial states. A critical element for its implementation is the availability of high-fidelity initial states, such as |0? and the 'magic state'. Here, we report an experiment, performed in a nuclear magnetic resonance (NMR) quantum processor, showing sufficient quantum control to improve the fidelity of imperfect initial magic states by distilling five of them into one with higher fidelity. PMID:21266968

  19. Synthesizing Logic in Fault-Tolerant Quantum Computers

    NASA Astrophysics Data System (ADS)

    Jones, Cody

    2014-03-01

    Quantum computers hold the promise of solving problems believed to be intractable using conventional computation, but this potential is impeded by the apparent difficulty in engineering reliable quantum hardware. One solution is quantum error correction (QEC), which enables fault-tolerant computation at the expense of a sizable overhead in qubits and gates. In this talk, I discuss several recent advancements in QEC to reduce the resource overhead in contemporary error-correction schemes like the surface code. Quantum logic can be encoded into so-called ``magic states,'' and the burden of error correction is shifted to verifying a well-characterized state, instead of protecting an arbitrary quantum process from errors. I discuss some of the recent work in magic-state distillation and its extensions to multi-qubit gates like Toffoli, which are ubiquitous in quantum algorithms. For operations in the surface code, resource overheads are improved by as much as two orders of magnitude.

  20. Symmetry-protected topologically ordered states for universal quantum computation

    NASA Astrophysics Data System (ADS)

    Nautrup, Hendrik Poulsen; Wei, Tzu-Chieh

    2015-11-01

    Measurement-based quantum computation is a model for quantum information processing utilizing local measurements on suitably entangled resource states for the implementation of quantum gates. A complete characterization for universal resource states is still missing. It has been shown that symmetry-protected topological order in one dimension can be exploited for the protection of certain quantum gates in measurement-based quantum computation. In this paper we show that the two-dimensional (2D) plaquette states on arbitrary lattices exhibit nontrivial symmetry-protected topological order in terms of symmetry fractionalization and that they are universal resource states for quantum computation. Our results of the nontrivial symmetry-protected topological order on arbitrary 2D lattices are based on an extension of the recent construction by Chen et al. [Phys. Rev. B 87, 155114 (2013), 10.1103/PhysRevB.87.155114] on the square lattice.

  1. Computable measure of total quantum correlations of multipartite systems

    NASA Astrophysics Data System (ADS)

    Behdani, Javad; Akhtarshenas, Seyed Javad; Sarbishaei, Mohsen

    2016-01-01

    Quantum discord as a measure of the quantum correlations cannot be easily computed for most of density operators. In this paper, we present a measure of the total quantum correlations that is operationally simple and can be computed effectively for an arbitrary mixed state of a multipartite system. The measure is based on the coherence vector of the party whose quantumness is investigated as well as the correlation matrix of this part with the remainder of the system. Being able to detect the quantumness of multipartite systems, such as detecting the quantum critical points in spin chains, alongside with the computability characteristic of the measure, makes it a useful indicator to be exploited in the cases which are out of the scope of the other known measures.

  2. Statistical Mechanics of Classical and Quantum Computational Complexity

    NASA Astrophysics Data System (ADS)

    Laumann, C. R.; Moessner, R.; Scardicchio, A.; Sondhi, S. L.

    The quest for quantum computers is motivated by their potential for solving problems that defy existing, classical, computers. The theory of computational complexity, one of the crown jewels of computer science, provides a rigorous framework for classifying the hardness of problems according to the computational resources, most notably time, needed to solve them. Its extension to quantum computers allows the relative power of quantum computers to be analyzed. This framework identifies families of problems which are likely hard for classical computers ("NP-complete") and those which are likely hard for quantum computers ("QMA-complete") by indirect methods. That is, they identify problems of comparable worst-case difficulty without directly determining the individual hardness of any given instance. Statistical mechanical methods can be used to complement this classification by directly extracting information about particular families of instances—typically those that involve optimization—by studying random ensembles of them. These pose unusual and interesting (quantum) statistical mechanical questions and the results shed light on the difficulty of problems for large classes of algorithms as well as providing a window on the contrast between typical and worst case complexity. In these lecture notes we present an introduction to this set of ideas with older work on classical satisfiability and recent work on quantum satisfiability as primary examples. We also touch on the connection of computational hardness with the physical notion of glassiness.

  3. Theory-Guided Technology in Computer Science.

    ERIC Educational Resources Information Center

    Ben-Ari, Mordechai

    2001-01-01

    Examines the history of major achievements in computer science as portrayed by winners of the prestigious Turing award and identifies a possibly unique activity called Theory-Guided Technology (TGT). Researchers develop TGT by using theoretical results to create practical technology. Discusses reasons why TGT is practical in computer science and

  4. College Students' Attitude towards Computer Technology

    ERIC Educational Resources Information Center

    Njagi, K. O.; Havice, W. L.

    2011-01-01

    Recent advances in the contemporary world, especially in the area of computer technology, have heralded the development and implementation of new and innovative teaching strategies and particularly with the Internet revolution. This study assessed students' attitude towards computer technology. Specifically, the study assessed differences in

  5. Computer Technology-Infused Learning Enhancement

    ERIC Educational Resources Information Center

    Keengwe, Jared; Anyanwu, Longy O.

    2007-01-01

    The purpose of the study was to determine students' perception of instructional integration of computer technology to improve learning. Two key questions were investigated in this study: (a) What is the students' perception of faculty integration of computer technology into classroom instruction? (b) To what extent does the students' perception of

  6. Prior Computer Experience and Technology Acceptance

    ERIC Educational Resources Information Center

    Varma, Sonali

    2010-01-01

    Prior computer experience with information technology has been identified as a key variable (Lee, Kozar, & Larsen, 2003) that can influence an individual's future use of newer computer technology. The lack of a theory driven approach to measuring prior experience has however led to conceptually different factors being used interchangeably in

  7. Computer Technology and Education: A Policy Delphi.

    ERIC Educational Resources Information Center

    Steier, Lloyd P.

    Realizing the educational potential of computer technology largely depends on developing appropriate policies related to the technology. A Policy Delphi method was used to identify changes in education that are both probable and possible on account of the introduction of computers, and to explore potential patterns for arriving at a desired

  8. Technologies for Visualization in Computational Aerosciences

    NASA Technical Reports Server (NTRS)

    Miceli, Kristina D.; Cooper, D. M. (Technical Monitor)

    1993-01-01

    State-of-the-art research in computational aerosciences produces' complex, time-dependent datasets. Simulations can also be multidisciplinary in nature, coupling two or more physical disciplines such as fluid dynamics, structural dynamics, thermodynamics, and acoustics. Many diverse technologies are necessary for visualizing computational aerosciences simulations. This paper describes these technologies and how they contribute to building effective tools for use by domain scientists. These technologies include data management, distributed environments, advanced user interfaces, rapid prototyping environments, parallel computation, and methods to visualize the scalar and vector fields associated with computational aerosciences datasets.

  9. Recent development of technologies for quantum communication

    NASA Astrophysics Data System (ADS)

    Tomita, Akihisa

    2005-01-01

    One of our major target is quantum key distribution (QKD,) which is closest to the practical use. Though QKD can be performed only with current technology, there still remain many thing to be improved. One of the most important devices that determine the system performance is photon detectors. It limits the transmission distance in optical fiber communication wavelength. A photon detector combining the two avalanche photon diodes (APD) has been demonstrated for qubit discrimination in 1550 nm. Spikes accompanied with the signals in gated-mode were canceled by balanced output from the two APDs. The balanced APD photon detector shows very low dark count rate (2x10-7) counts/pulse) with 10 % detection efficiency. We have also developed a highly stable interferometer on a planer-lightwave-circuit (PLC.) We have achieved single-photon interference over 150 km using time-division interferometers for quantum cryptography, which were composed of the two integrated-optic asymmetric Mach-Zehnder interferometers, and the balanced gated-mode photon detectors. The observed visibility was more than 80 % after 150-km transmission, which refers to a quantum bit error rate of less than 10 %. We will also describe temperature insensible QKD system and high speed (100 bps) key transmission over 40 km fiber.

  10. Center for Computer Sciences and Technology.

    ERIC Educational Resources Information Center

    National Bureau of Standards (DOC), Washington, DC.

    Functions of the Center for Computer Sciences and Technology (CCST), a national center for computer research and development for the United States government, are described. CCST provides computer and related services to the National Bureau of Standards of which it is a part and to other government agencies on a cost-reimbursable basis. The Office…

  11. Computer Technology Resources for Literacy Projects.

    ERIC Educational Resources Information Center

    Florida State Council on Aging, Tallahassee.

    This resource booklet was prepared to assist literacy projects and community adult education programs in determining the technology they need to serve more older persons. Section 1 contains the following reprinted articles: "The Human Touch in the Computer Age: Seniors Learn Computer Skills from Schoolkids" (Suzanne Kashuba); "Computer Instruction

  12. Applications of Computer Technology in Intercollegiate Debate.

    ERIC Educational Resources Information Center

    Kay, Jack, Ed.

    1986-01-01

    Focusing on how computers can and should be used in intercollegiate forensics, this journal issue offers the perspectives of a number of forensics instructors. The lead article, "Applications of Computer Technology in Intercollegiate Debate" by Theodore F. Sheckels, Jr., discusses five areas in which forensics educators might use computer

  13. Quantum Optical Technologies for Metrology, Sensing, and Imaging

    NASA Astrophysics Data System (ADS)

    Dowling, Jonathan P.; Seshadreesan, Kaushik P.

    2015-06-01

    Over the past 20 years, bright sources of entangled photons have led to a renaissance in quantum optical interferometry. Optical interferometry has been used to test the foundations of quantum mechanics and implement some of the novel ideas associated with quantum entanglement such as quantum teleportation, quantum cryptography, quantum lithography, quantum computing logic gates, and quantum metrology. In this paper, we focus on the new ways that have been developed to exploit quantum optical entanglement in quantum metrology to beat the shot-noise limit, which can be used, e.g., in fiber optical gyroscopes and in sensors for biological or chemical targets. We also discuss how this entanglement can be used to beat the Rayleigh diffraction limit in imaging systems such as in LIDAR and optical lithography.

  14. Trapped Ion Quantum Computing with Microwaves

    NASA Astrophysics Data System (ADS)

    Randall, Joe; Weidt, Sebastian; Standing, Eamon; Webster, Simon; Lake, Kim; Murgia, David; Navickas, Tomas; Lekitsch, Bjoern; Hughes, Marcus; Sterling, Robin; de Motte, Darren; Giri, Gouri; Rodriguez, Andrea; Webb, Anna; Rattanasonti, Hwanjit; Srinivasan, Prasanna; Kraft, Michael; Maclean, Jessica; Mellor, Chris; Hensinger, Winfried

    2015-03-01

    To this point, entanglement operations in trapped ion qubits have been predominantly performed with lasers. However, this becomes problematic when scaling to large numbers of qubits due to the challenging engineering required. The use of stable and easily controllable microwaves to drive entanglement gates can overcome this problem. We will present our work towards implementing multi-qubit entanglement gates using microwaves in an experimental setup that produces a static magnetic field gradient of 24 T/m over an ion string. We will first present a scheme for preparing and manipulating dressed-state qubits and qutrits that are highly robust to decoherence from magnetic field fluctuations. We will also present our work experimentally demonstrating motional sideband transitions and Schrdinger cat states using microwaves in conjunction with the magnetic field gradient, as well as sideband cooling to the ground state of motion using dressed-states. Furthermore, we will show our latest results in creating microfabricated ion trap chips towards large scale quantum computing and simulation.

  15. Symbolic Quantum Computation Simulation in SymPy

    NASA Astrophysics Data System (ADS)

    Cugini, Addison; Curry, Matt; Granger, Brian

    2010-10-01

    Quantum computing is an emerging field which aims to use quantum mechanics to solve difficult computational problems with greater efficiency than on a classical computer. There is a need to create software that i) helps newcomers to learn the field, ii) enables practitioners to design and simulate quantum circuits and iii) provides an open foundation for further research in the field. Towards these ends we have created a package, in the open-source symbolic computation library SymPy, that simulates the quantum circuit model of quantum computation using Dirac notation. This framework builds on the extant powerful symbolic capabilities of SymPy to preform its simulations in a fully symbolic manner. We use object oriented design to abstract circuits as ordered collections of quantum gate and qbit objects. The gate objects can either be applied directly to the qbit objects or be represented as matrices in different bases. The package is also capable of performing the quantum Fourier transform and Shor's algorithm. A notion of measurement is made possible through the use of a non-commutative gate object. In this talk, we describe the software and show examples of quantum circuits on single and multi qbit states that involve common algorithms, gates and measurements.

  16. From Computer Lab to Technology Class.

    ERIC Educational Resources Information Center

    Sherwood, Sandra

    1999-01-01

    Discussion of integrating technology into elementary school classrooms focuses on teacher training that is based on a three-year plan developed at an elementary school in Marathon, New York. Describes the role of a technology teacher who facilitates technology integration by running the computer lab, offering workshops, and developing inservice…

  17. Education & Technology: Reflections on Computing in Classrooms.

    ERIC Educational Resources Information Center

    Fisher, Charles, Ed.; Dwyer, David C., Ed.; Yocam, Keith, Ed.

    This volume examines learning in the age of technology, describes changing practices in technology-rich classrooms, and proposes new ways to support teachers as they incorporate technology into their work. It commemorates the eleventh anniversary of the Apple Classrooms of Tomorrow (ACOT) Project, when Apple Computer, Inc., in partnership with a…

  18. Consciousness and Logic in a Quantum-Computing Universe

    NASA Astrophysics Data System (ADS)

    Zizzi, Paola

    The early inflationary universe can be described in terms of quantum information. More specifically, the inflationary universe can be viewed as a superposed state of quantum registers. Actually, during inflation, one can speak of a quantum superposition of universes. At the end of inflation, only one universe is selected, by a mechanism called self-reduction, which is consistent with Penrose's objective reduction (OR) model. The quantum gravity threshold of (OR) is reached at the end of inflation, and corresponds to a superposed state of 109 quantum registers. This is also the number of superposed tubulins qubits in our brain, which undergo the Penrose-Hameroff orchestrated objective reduction, (Orch OR), leading to a conscious event. Then, an analogy naturally arises between the very early quantum-computing universe, and our mind. In fact, we argue that at the end of in- flation, the universe underwent a cosmic conscious event, the so-called "Big Wow", which acted as an imprinting for the future minds to come, with future modes of computation, consciousness and logic. The postinflationary universe organized itself as a cellular automaton (CA) with two computational modes: quantum and classical, like the two conformations assumed by the cellular automaton of tubulins in our brain, as in Hameroff's model. In the quantum configuration, the universe quantum-evaluates recursive functions, which are the laws of physics in their most abstract form. To do so in a very efficient way, the universe uses, as subroutines, black holes - quantum computers and quantum minds, which operate in parallel. The outcomes of the overall quantum computation are the universals, the attributes of things in themselves. These universals are partially obtained also by the quantum minds, and are endowed with subjective meaning. The units of the subjective universals are qualia, which are strictly related to the (virtual) existence of Planckian black holes. Further, we consider two aspects of the quantum mind, which are not algorithmic in the usual sense: the self, and mathematical intuition. The self is due to a reversible self-measurement of a quantum state of superposed tubulins. Mathematical intuition is due to the paraconsistent logic of the internal observer in a quantum-computing universe.

  19. Stability of Quantum Computing in the Presence of Imperfections

    NASA Astrophysics Data System (ADS)

    Benenti, G.; Casati, G.; Montangero, S.

    We model an isolated quantum computer as a two-dimensional lattice of qubits (spin halves) with fluctuations in individual qubit energies and residual short-range inter-qubit couplings. We show that above a critical inter-qubit coupling strength, quantum chaos sets in and this results in the interaction induced dynamical thermalization and occupation numbers well described by the Fermi Dirac distribution. This thermalization destroys the noninteracting qubit structure and sets serious requirements for the quantum computer operability. We then construct a quantum algorithm which uses qubits in an optimal way and efficiently simulates a physical model with rich and complex dynamics. The numerical study of the effect of static imperfections in the quantum computer hardware shows that the main elements of the phase space structures are accurately reproduced up to a time scale which is polynomial in the number of qubits. The errors generated by these imperfections are more significant than the errors of random noise in gate operations.

  20. The QUANTGRID Project (RO)Quantum Security in GRID Computing Applications

    NASA Astrophysics Data System (ADS)

    Dima, M.; Dulea, M.; Petre, M.; Petre, C.; Mitrica, B.; Stoica, M.; Udrea, M.; Sterian, R.; Sterian, P.

    2010-01-01

    The QUANTGRID Project, financed through the National Center for Programme Management (CNMP-Romania), is the first attempt at using Quantum Crypted Communications (QCC) in large scale operations, such as GRID Computing, and conceivably in the years ahead in the banking sector and other security tight communications. In relation with the GRID activities of the Center for Computing & Communications (Nat.'l Inst. Nucl. Phys.IFIN-HH), the Quantum Optics Lab. (Nat.'l Inst. Plasma and LasersINFLPR) and the Physics Dept. (University PolytechnicaUPB) the project will build a demonstrator infrastructure for this technology. The status of the project in its incipient phase is reported, featuring tests for communications in classical security mode: socket level communications under AES (Advanced Encryption Std.), both proprietary code in C++ technology. An outline of the planned undertaking of the project is communicated, highlighting its impact in quantum physics, coherent optics and information technology.

  1. Quantum computing with photons: introduction to the circuit model, the one-way quantum computer, and the fundamental principles of photonic experiments

    NASA Astrophysics Data System (ADS)

    Barz, Stefanie

    2015-04-01

    Quantum physics has revolutionized our understanding of information processing and enables computational speed-ups that are unattainable using classical computers. This tutorial reviews the fundamental tools of photonic quantum information processing. The basics of theoretical quantum computing are presented and the quantum circuit model as well as measurement-based models of quantum computing are introduced. Furthermore, it is shown how these concepts can be implemented experimentally using photonic qubits, where information is encoded in the photons polarization.

  2. Minimum heat dissipation in measurement-based quantum computation

    NASA Astrophysics Data System (ADS)

    Morimae, Tomoyuki

    2015-04-01

    We show that at least 2 k T ln2 of heat dissipation per qubit (in the register of a simulated circuit) occurs in measurement-based quantum computation according to Landauer's principle. This result is derived by using only the fundamental fact that quantum physics respects the no-signaling principle.

  3. Quantum-dot cluster-state computing with encoded qubits

    NASA Astrophysics Data System (ADS)

    Weinstein, Yaakov S.; Hellberg, C. Stephen; Levy, Jeremy

    2005-08-01

    A class of architectures is advanced for cluster-state quantum computation using quantum dots. These architectures include using single and multiple dots as logical qubits. Special attention is given to supercoherent qubits introduced by Bacon [Phys. Rev. Lett. 87, 247902 (2001)] for which we discuss the effects of various errors and present a means of error protection.

  4. Quantum computation with classical light: The Deutsch Algorithm

    NASA Astrophysics Data System (ADS)

    Perez-Garcia, Benjamin; Francis, Jason; McLaren, Melanie; Hernandez-Aranda, Raul I.; Forbes, Andrew; Konrad, Thomas

    2015-08-01

    We present an implementation of the Deutsch Algorithm using linear optical elements and laser light. We encoded two quantum bits in form of superpositions of electromagnetic fields in two degrees of freedom of the beam: its polarisation and orbital angular momentum. Our approach, based on a Sagnac interferometer, offers outstanding stability and demonstrates that optical quantum computation is possible using classical states of light.

  5. Computing, Information and Communications Technology (CICT) Website

    NASA Technical Reports Server (NTRS)

    Hardman, John; Tu, Eugene (Technical Monitor)

    2002-01-01

    The Computing, Information and Communications Technology Program (CICT) was established in 2001 to ensure NASA's Continuing leadership in emerging technologies. It is a coordinated, Agency-wide effort to develop and deploy key enabling technologies for a broad range of mission-critical tasks. The NASA CICT program is designed to address Agency-specific computing, information, and communications technology requirements beyond the projected capabilities of commercially available solutions. The areas of technical focus have been chosen for their impact on NASA's missions, their national importance, and the technical challenge they provide to the Program. In order to meet its objectives, the CICT Program is organized into the following four technology focused projects: 1) Computing, Networking and Information Systems (CNIS); 2) Intelligent Systems (IS); 3) Space Communications (SC); 4) Information Technology Strategic Research (ITSR).

  6. Computers and Writing. Tech Use Guide: Using Computer Technology.

    ERIC Educational Resources Information Center

    Dalton, Bridget

    One of nine brief guides for special educators on using computer technology, this guide focuses on the use of computers to improve skills and attitudes in writing instruction. Pre-writing tools such as group brainstorming, story webs, free-writing, journal entries, and prewriting guides help generate ideas and can be carried out either on or off

  7. Silicon in the quantum limit: Quantum computing and decoherence in silicon architectures

    NASA Astrophysics Data System (ADS)

    Tahan, Charles George

    The pursuit of spin and quantum entanglement-based devices in solid-state systems has become a global endeavor. The approach of the quantum size limit in computer electronics, the many recent advances in nanofabrication, and the rediscovery that information is physical (and thus based on quantum physics) have started a worldwide race to understand and control quantum systems in a coherent and useful way. Semiconductor architectures hold promise for quantum information processing (QIP) applications due to their large industrial base and perceived scalability potential. Electron spins in silicon in particular may be an excellent architecture for QIP and also for spin electronics (spintronics) applications. While charged gates easily manipulate the charge of an electron, the spin degree of freedom is well isolated from charge fluctuations. This leads to very good spin quantum bit (qubit) stability or quantum coherence properties. Inherently small spin-orbit coupling and the existence of a spin-zero Si isotope also facilitate long single spin coherence times. Here we consider the relaxation properties of localized electronic states in silicon due to donors, quantum wells, and quantum dots. Our analysis is impeded by the complicated, many-valley band structure of silicon and previously unaddressed physics in silicon quantum wells. We find that electron spins in silicon and especially strained silicon have excellent decoherence properties. Where possible we compare with experiment to test our theories. We go beyond issues of coherence in a quantum computer to problems of control and measurement. Precisely what makes spin relaxation so long in semiconductor architectures makes spin measurement so difficult. To address this, we propose a new scheme for spin readout, which has the added benefit of automatic spin initialization, a vital component to quantum computing and quantum error correction. Our results represent important practical milestones on the way to the design and construction of a silicon-based quantum computer.

  8. Simulating Bell violations without quantum computers

    NASA Astrophysics Data System (ADS)

    Drummond, P. D.; Opanchuk, B.; Rosales-Zrate, L.; Reid, M. D.

    2014-04-01

    We demonstrate that it is possible to simulate Bell violations using probabilistic methods. A quantum state corresponding to optical experiments that violate a Bell inequality is randomly sampled, demonstrating Bell's quantum paradox. This provides an explicit counter-example to Feynman's claim that such classical simulations could not be carried out.

  9. Bounds for the adiabatic approximation with applications to quantum computation

    SciTech Connect

    Jansen, Sabine; Ruskai, Mary-Beth; Seiler, Ruedi

    2007-10-15

    We present straightforward proofs of estimates used in the adiabatic approximation. The gap dependence is analyzed explicitly. We apply the result to interpolating Hamiltonians of interest in quantum computing.

  10. Superradiance as a source of collective decoherence in quantum computers

    NASA Astrophysics Data System (ADS)

    Yavuz, D. D.

    2014-11-01

    We argue that superradiance (collective emission) due to radiative coupling of qubit states results in non-local noise, and thus introduces an error source that cannot be corrected using current models of fault-tolerant quantum computation.

  11. (CICT) Computing, Information, and Communications Technology Overview

    NASA Technical Reports Server (NTRS)

    VanDalsem, William R.

    2003-01-01

    The goal of the Computing, Information, and Communications Technology (CICT) program is to enable NASA's Scientific Research, Space Exploration, and Aerospace Technology Missions with greater mission assurance, for less cost, with increased science return through the development and use of advanced computing, information and communications technologies. This viewgraph presentation includes diagrams of how the political guidance behind CICT is structured. The presentation profiles each part of the NASA Mission in detail, and relates the Mission to the activities of CICT. CICT's Integrated Capability Goal is illustrated, and hypothetical missions which could be enabled by CICT are profiled. CICT technology development is profiled.

  12. Nonlocality as a Benchmark for Universal Quantum Computation in Ising Anyon Topological Quantum Computers

    NASA Astrophysics Data System (ADS)

    Howard, Mark; Vala, Jiri

    2012-02-01

    An obstacle affecting any proposal for a topological quantum computer based on Ising anyons is that quasiparticle braiding can only implement a finite (non-universal) set of quantum operations. The computational power of this restricted set of operations (often called stabilizer operations) is far weaker than a universal QC, unless supplemented with an additional non-stabilizer operation. Similarly, a bipartite two-qubit system based on Ising anyons cannot exhibit non-locality (in the sense of violating a Bell inequality) when only topologically protected stabilizer operations are performed. To produce correlations that cannot be described by an LHV model again requires the use of a non-stabilizer operation. Using geometric techniques, we relate the sets of operations that enable universal QC with those that enable violation of a Bell inequality. Motivated by the fact that non-stabilizer operations are expected to be highly imperfect, our aim is to provide a benchmark for identifying UQC-enabling operations that is both experimentally practical and conceptually simple. We show that any (noisy) single-qubit non-stabilizer operation that, together with perfect stabilizer operations, enables violation of the simplest two-qubit Bell inequality can also be used to enable UQC.

  13. ONSET OF CHAOS IN A MODEL OF QUANTUM COMPUTATION

    SciTech Connect

    G. BERMAN; ET AL

    2001-02-01

    Recently, the question of a relevance of the so-called quantum chaos has been raised in applications to quantum computation [2,3]. Indeed, according to the general approach to closed systems of finite number of interacting Fermi-particles (see, e.g. [4,5]), with an increase of an interaction between qubits a kind of chaos is expected to emerge in the energy spectra and structure of many-body states. Specifically, the fluctuations of energy levels and components of the eigenstates turn out to be very strong and described by the Random Matrix Theory. Clearly, if this happens in a quantum computer, it may lead to a destruction of the coherence of quantum computations due to internal decoherence inside many-body states. It is important to stress that quantum chaos occurs not only in the systems with random interaction, but also for purely dynamical interaction. In the latter case, the mechanism of chaos is due to a complex (non-linear) form of a two-body interaction represented in the basis of non-interacting particles. Numerical analysis [2] of a simplest model of quantum computer (2D model of 1/2-spins with a random interqubit interaction J) shows that with an increase of the number L of qubits, the chaos threshold J{sub cr} decreases as J{sub cr} {infinity} 1/L. On this ground, it was claimed that the onset of quantum chaos could be dangerous for quantum computers, since their effectiveness requires L >> 1. On the other hand, in [3] it was argued that in order to treat this problem properly, one needs to distinguish between chaotic properties of stationary states, and the dynamical process of quantum computation.

  14. Thermalization in Nature and on a Quantum Computer

    NASA Astrophysics Data System (ADS)

    Riera, Arnau; Gogolin, Christian; Eisert, Jens

    2012-02-01

    In this work, we show how Gibbs or thermal states appear dynamically in closed quantum many-body systems, building on the program of dynamical typicality. We introduce a novel perturbation theorem for physically relevant weak system-bath couplings that is applicable even in the thermodynamic limit. We identify conditions under which thermalization happens and discuss the underlying physics. Based on these results, we also present a fully general quantum algorithm for preparing Gibbs states on a quantum computer with a certified runtime and error bound. This complements quantum Metropolis algorithms, which are expected to be efficient but have no known runtime estimates and only work for local Hamiltonians.

  15. Universal linear Bogoliubov transformations through one-way quantum computation

    SciTech Connect

    Ukai, Ryuji; Yoshikawa, Jun-ichi; Iwata, Noriaki; Furusawa, Akira; Loock, Peter van

    2010-03-15

    We show explicitly how to realize an arbitrary linear unitary Bogoliubov (LUBO) transformation on a multimode quantum state through homodyne-based one-way quantum computation. Any LUBO transformation can be approximated by means of a fixed, finite-sized, sufficiently squeezed Gaussian cluster state that allows for the implementation of beam splitters (in form of three-mode connection gates) and general one-mode LUBO transformations. In particular, we demonstrate that a linear four-mode cluster state is a sufficient resource for an arbitrary one-mode LUBO transformation. Arbitrary-input quantum states including non-Gaussian states could be efficiently attached to the cluster through quantum teleportation.

  16. Ultimate computing. Biomolecular consciousness and nano Technology

    SciTech Connect

    Hameroff, S.R.

    1987-01-01

    The book advances the premise that the cytoskeleton is the cell's nervous system, the biological controller/computer. If indeed cytoskeletal dynamics in the nanoscale (billionth meter, billionth second) are the texture of intracellular information processing, emerging ''NanoTechnologies'' (scanning tunneling microscopy, Feynman machines, von Neumann replicators, etc.) should enable direct monitoring, decoding and interfacing between biological and technological information devices. This in turn could result in important biomedical applications and perhaps a merger of mind and machine: Ultimate Computing.

  17. Scalable digital hardware for a trapped ion quantum computer

    NASA Astrophysics Data System (ADS)

    Mount, Emily; Gaultney, Daniel; Vrijsen, Geert; Adams, Michael; Baek, So-Young; Hudek, Kai; Isabella, Louis; Crain, Stephen; van Rynbach, Andre; Maunz, Peter; Kim, Jungsang

    2015-09-01

    Many of the challenges of scaling quantum computer hardware lie at the interface between the qubits and the classical control signals used to manipulate them. Modular ion trap quantum computer architectures address scalability by constructing individual quantum processors interconnected via a network of quantum communication channels. Successful operation of such quantum hardware requires a fully programmable classical control system capable of frequency stabilizing the continuous wave lasers necessary for loading, cooling, initialization, and detection of the ion qubits, stabilizing the optical frequency combs used to drive logic gate operations on the ion qubits, providing a large number of analog voltage sources to drive the trap electrodes, and a scheme for maintaining phase coherence among all the controllers that manipulate the qubits. In this work, we describe scalable solutions to these hardware development challenges.

  18. Computer technology forecast study for general aviation

    NASA Technical Reports Server (NTRS)

    Seacord, C. L.; Vaughn, D.

    1976-01-01

    A multi-year, multi-faceted program is underway to investigate and develop potential improvements in airframes, engines, and avionics for general aviation aircraft. The objective of this study was to assemble information that will allow the government to assess the trends in computer and computer/operator interface technology that may have application to general aviation in the 1980's and beyond. The current state of the art of computer hardware is assessed, technical developments in computer hardware are predicted, and nonaviation large volume users of computer hardware are identified.

  19. Unitary R-matrices for topological quantum computing

    NASA Astrophysics Data System (ADS)

    Burton, P. J.; Gould, M. D.

    2006-02-01

    The main problem with current approaches to quantum computing is the difficulty of establishing and maintaining entanglement. A Topological Quantum Computer (TQC) aims to overcome this by using different physical processes that are topological in nature and which are less susceptible to disturbance by the environment. In a (2+1)-dimensional system, pseudoparticles called anyons have statistics that fall somewhere between bosons and fermions. The exchange of two anyons, an effect called braiding from knot theory, can occur in two different ways. The quantum states corresponding to the two elementary braids constitute a two-state system allowing the definition of a computational basis. Quantum gates can be built up from patterns of braids and for quantum computing it is essential that the operator describing the braidingthe R-matrixbe described by a unitary operator. The physics of anyonic systems is governed by quantum groups, in particular the quasi-triangular Hopf algebras obtained from finite groups by the application of the Drinfeld quantum double construction. Their representation theory has been described in detail by Gould and Tsohantjis, and in this review article we relate the work of Gould to TQC schemes, particularly that of Kauffman.

  20. Environmentally decoupled sds -wave Josephson junctions for quantum computing

    NASA Astrophysics Data System (ADS)

    Ioffe, Lev B.; Geshkenbein, Vadim B.; Feigel'Man, Mikhail V.; Fauchre, Alban L.; Blatter, Gianni

    1999-04-01

    Quantum computers have the potential to outperform their classical counterparts in a qualitative manner, as demonstrated by algorithms which exploit the parallelism inherent in the time evolution of a quantum state. In quantum computers, the information is stored in arrays of quantum two-level systems (qubits), proposals for which include utilizing trapped atoms and photons, magnetic moments in molecules and various solid-state implementations. But the physical realization of qubits is challenging because useful quantum computers must overcome two conflicting difficulties: the computer must be scalable and controllable, yet remain almost completely detached from the environment during operation, in order to maximize the phase coherence time. Here we report a concept for a solid-state `quiet' qubit that can be efficiently decoupled from the environment. It is based on macroscopic quantum coherent states in a superconducting quantum interference loop. Our two-level system is naturally bistable, requiring no external bias: the two basis states are characterized by different macroscopic phase drops across a Josephson junction, which may be switched with minimal external contact.

  1. Assessing claims of quantum annealing: Does D-Wave have a quantum computer?

    NASA Astrophysics Data System (ADS)

    Smolin, John; Smith, Graeme

    2014-03-01

    There has recently been much publicity surrounding D-Wave's so-called quantum computing machines. Though there is little reason to expect that their highly decoherent devices actually perform quantum computation, they have persisted in making strong claims about the performance of their system in the scientific literature and to the press. Here we focus on showing that the evidence of quantumness given in the literature is extremely weak and is consistant with an effective classical description. We further show by comparing to the performance of classical simulated annealing that the idea that their current machines outperform a classical computers is unfounded.

  2. Fault-tolerant linear optics quantum computation by error-detecting quantum state transfer

    SciTech Connect

    Cho, Jaeyoon

    2007-10-15

    A scheme for linear optical implementation of fault-tolerant quantum computation is proposed, which is based on an error-detecting code. Each computational step is mediated by transfer of quantum information into an ancilla system embedding error-detection capability. Photons are assumed to be subjected to both photon loss and depolarization, and the threshold region of their strengths for scalable quantum computation is obtained, together with the amount of physical resources consumed. Compared to currently known results, the present scheme reduces the resource requirement, while yielding a comparable threshold region.

  3. Generalized duality quantum computers acting on mixed states

    NASA Astrophysics Data System (ADS)

    Chen, Liang; Cao, Huai-Xin; Meng, Hui-Xian

    2015-11-01

    A generalized duality quantum computer acting on mixed states (GDQC-MS) is established, which is a device consisting of a generalized quantum wave divider, a finite number of generalized quantum operations, and a generalized quantum wave combiner. Some of the interesting properties of a GDQC are explored. For example, it is proved that the divider and the combiner of a GDQC-MS are mutually dual contractions, and when the generalized quantum operations used in a GDQC-MS are contractions, the GDQC-MS is also a contraction. In that case, the loss of an input state passing through a GDQC-MS is measured and the corresponding operator of a GDQC-MS is a generalized quantum operation.

  4. Computer Technology and the Social Studies.

    ERIC Educational Resources Information Center

    Glenn, Allen D.; Klassen, Daniel L.

    1983-01-01

    The citizen of tomorrow needs to understand the role of information in political systems; computer technology and information storage, retrieval, and use; the implications of information systems for individual rights; and the impact of computer crime, databanks, and systems analysis on the social, economic, and political spheres. (QKR)

  5. Quantum Computing: Selected Internet Resources for Librarians, Researchers, and the Casually Curious

    ERIC Educational Resources Information Center

    Cirasella, Jill

    2009-01-01

    This article presents an annotated selection of the most important and informative Internet resources for learning about quantum computing, finding quantum computing literature, and tracking quantum computing news. All of the quantum computing resources described in this article are freely available, English-language web sites that fall into one

  6. Quantum Computing: Selected Internet Resources for Librarians, Researchers, and the Casually Curious

    ERIC Educational Resources Information Center

    Cirasella, Jill

    2009-01-01

    This article presents an annotated selection of the most important and informative Internet resources for learning about quantum computing, finding quantum computing literature, and tracking quantum computing news. All of the quantum computing resources described in this article are freely available, English-language web sites that fall into one…

  7. Quantum toys for quantum computing: persistent currents controlled by the spin Josephson effect.

    PubMed

    Tatara, Gen; Garcia, N

    2003-08-15

    Quantum devices and computers will need operational units in different architectural configurations for their functioning. The unit should be a simple "quantum toy," an easy to handle superposition state. Here such a novel unit of quantum mechanical flux state (or persistent current) in a conducting ring with three ferromagnetic quantum dots is presented. The state is labeled by the two directions of the persistent current, which is driven by the spin chirality of the dots, and is controlled by the spin (the spin Josephson effect). It is demonstrated that by the use of two connected rings, one can carry out unitary transformations on the input flux state by controlling one spin in one of the rings, enabling us to prepare superposition states. The flux is shown to be a quantum operation gate, and may be useful in quantum computing. PMID:12935044

  8. Quantum perceptron over a field and neural network architecture selection in a quantum computer.

    PubMed

    da Silva, Adenilton José; Ludermir, Teresa Bernarda; de Oliveira, Wilson Rosa

    2016-04-01

    In this work, we propose a quantum neural network named quantum perceptron over a field (QPF). Quantum computers are not yet a reality and the models and algorithms proposed in this work cannot be simulated in actual (or classical) computers. QPF is a direct generalization of a classical perceptron and solves some drawbacks found in previous models of quantum perceptrons. We also present a learning algorithm named Superposition based Architecture Learning algorithm (SAL) that optimizes the neural network weights and architectures. SAL searches for the best architecture in a finite set of neural network architectures with linear time over the number of patterns in the training set. SAL is the first learning algorithm to determine neural network architectures in polynomial time. This speedup is obtained by the use of quantum parallelism and a non-linear quantum operator. PMID:26878722

  9. Quantum Monte Carlo Endstation for Petascale Computing

    SciTech Connect

    David Ceperley

    2011-03-02

    The major achievements enabled by QMC Endstation grant include * Performance improvement on clusters of x86 multi-core systems, especially on Cray XT systems * New and improved methods for the wavefunction optimizations * New forms of trial wavefunctions * Implementation of the full application on NVIDIA GPUs using CUDA The scaling studies of QMCPACK on large-scale systems show excellent parallel efficiency up to 216K cores on Jaguarpf (Cray XT5). The GPU implementation shows speedups of 10-15x over the CPU implementation on older generation of x86. We have implemented hybrid OpenMP/MPI scheme in QMC to take advantage of multi-core shared memory processors of petascale systems. Our hybrid scheme has several advantages over the standard MPI-only scheme. * Memory optimized: large read-only data to store one-body orbitals and other shared properties to represent the trial wave function and many-body Hamiltonian can be shared among threads, which reduces the memory footprint of a large-scale problem. * Cache optimized: the data associated with an active Walker are in cache during the compute-intensive drift-diffusion process and the operations on an Walker are optimized for cache reuse. Thread-local objects are used to ensure the data affinity to a thread. * Load balanced: Walkers in an ensemble are evenly distributed among threads and MPI tasks. The two-level parallelism reduces the population imbalance among MPI tasks and reduces the number of point-to-point communications of large messages (serialized objects) for the Walker exchange. * Communication optimized: the communication overhead, especially for the collective operations necessary to determine ET and measure the properties of an ensemble, is significantly lowered by using less MPI tasks. The multiple forms of parallelism afforded by QMC algorithms make them ideal candidates for acceleration in the many-core paradigm. We presented the results of our effort to port the QMCPACK simulation code to the NVIDIA CUDA GPU platform. We restructured the CPU algorithms to express additional parallelism, minimize GPU-CPU communication, and efficiently utilize the GPU memory hierarchy. Using mixed precision on GT200 GPUs and MPI for intercommunication and load balancing, we observe typical full-application speedups of approximately 10x to 15x relative to quad-core Xeon CPUs alone, while reproducing the double-precision CPU results within statistical error. We developed an all-electron quantum Monte Carlo (QMC) method for solids that does not rely on pseudopotentials, and used it to construct a primary ultra-high-pressure calibration based on the equation of state of cubic boron nitride. We computed the static contribution to the free energy with the QMC method and obtained the phonon contribution from density functional theory, yielding a high-accuracy calibration up to 900 GPa usable directly in experiment. We computed the anharmonic Raman frequency shift with QMC simulations as a function of pressure and temperature, allowing optical pressure calibration. In contrast to present experimental approaches, small systematic errors in the theoretical EOS do not increase with pressure, and no extrapolation is needed. This all-electron method is applicable to first-row solids, providing a new reference for ab initio calculations of solids and benchmarks for pseudopotential accuracy. We compared experimental and theoretical results on the momentum distribution and the quasiparticle renormalization factor in sodium. From an x-ray Compton-profile measurement of the valence-electron momentum density, we derived its discontinuity at the Fermi wavevector finding an accurate measure of the renormalization factor that we compared with quantum-Monte-Carlo and G0W0 calculations performed both on crystalline sodium and on the homogeneous electron gas. Our calculated results are in good agreement with the experiment. We have been studying the heat of formation for various Kubas complexes of molecular hydrogen on Ti(1,2)ethylene-nH2 using Diffusion Monte Carlo. This work has been started and is ongoing. We are studying systems involving 1 and 2 Ti bonding sites with up to 10 hydrogen molecules in numerous configurations. This work will establish a benchmark that will test the accuracy of density functional calculations and establish the feasibility of our methods for similar systems.

  10. Are materials good enough for a superconducting quantum computer?

    NASA Astrophysics Data System (ADS)

    Martinis, John

    2013-03-01

    Recent developments of surface codes now place superconducting quantum computing at an important crossroad, where ``proof of concept'' experiments involving small numbers of qubits can be transitioned to more challenging and systematic approaches that could actually lead to building a quantum computer. Although the integrated circuit nature of these qubits helps with the design of a complex architecture and control system, it also presents a serious challenge for coherence since the quantum wavefunctions are in contact with a variety of materials defects. I will review both logic gate design and recent developments in coherence in superconducting qubits, and argue that state-of-the-art devices are now near the fault tolerant threshold. Future progress looks promising for fidelity ten times better than threshold, as needed for scalable quantum error correction and computation.

  11. Analyzing Many-Body Localization with a Quantum Computer

    NASA Astrophysics Data System (ADS)

    Bauer, Bela; Nayak, Chetan

    2014-10-01

    Many-body localization, the persistence against electron-electron interactions of the localization of states with nonzero excitation energy density, poses a challenge to current methods of theoretical and numerical analyses. Numerical simulations have so far been limited to a small number of sites, making it difficult to obtain reliable statements about the thermodynamic limit. In this paper, we explore the ways in which a relatively small quantum computer could be leveraged to study many-body localization. We show that, in addition to studying time evolution, a quantum computer can, in polynomial time, obtain eigenstates at arbitrary energies to sufficient accuracy that localization can be observed. The limitations of quantum measurement, which preclude the possibility of directly obtaining the entanglement entropy, make it difficult to apply some of the definitions of many-body localization used in the recent literature. We discuss alternative tests of localization that can be implemented on a quantum computer.

  12. EDITORIAL: Progress in quantum technology: one photon at a time Progress in quantum technology: one photon at a time

    NASA Astrophysics Data System (ADS)

    Demming, Anna

    2012-07-01

    Technological developments sparked by quantum mechanics and wave-particle duality are still gaining ground over a hundred years after the theories were devised. While the impact of the theories in fundamental research, philosophy and even art and literature is widely appreciated, the implications in device innovations continue to breed potential. Applications inspired by these concepts include quantum computation and quantum cryptography protocols based on single photons, among many others. In this issue, researchers in Germany and the US report a step towards precisely triggered single-photon sources driven by surface acoustic waves (SAWs) [1]. The work brings technology based on quantum mechanics yet another step closer to practical device reality. Generation of single 'antibunched' photons has been one of the key challenges to progress in quantum information processing and communication. Researchers from Toshiba and Cambridge University in the UK recently reported what they described as 'the first electrically driven single-photon source capable of emitting indistinguishable photons' [2]. Single-photon sources have been reported previously [3]. However the approach demonstrated by Shields and colleagues allows electrical control, which is particularly useful for implementing in compact devices. The researchers used a layer of InAs quantum dots embedded in the intrinsic region of a p-i-n diode to demonstrate interference between single photons. They also present a complete theory based on the interference of photons with a Lorentzian spectrum, which they compare with both continuous-wave and pulsed experiments. The application of SAWs in achieving precisely triggered single-photon sources develops the work of researchers in Germany in the late 1990s [4]. Surface acoustic waves travel like sound waves, but are characterized by an amplitude that typically decays exponentially with depth into the substrate. As Rocke and colleagues demonstrated, they can be used to dissociate an optically excited exciton and spatially separate the electron and hole, thereby increasing the radiative lifetime by orders of magnitude. The interesting behaviour of SAWs has led to studies towards a number of other applications including sensing [5-7], synthesis and nanoassembly [8]. For applications in single-photon sources, the electron-hole pairs are transported by the SAW to a quantum dot where they recombine emitting a single photon. However, so far various limiting factors in the system, such as the low quality of the quantum dots used leading to multiple-exciton recombinations, have hindered potential applications of the system as a single-photon source. Control over high-quality quantum-dot self-assembly is constantly improving. Researchers at the University of California at Berkeley and Harvard University in the US report the ability to successfully position a small number of colloidal quantum dots to within less than 100 nm accuracy on metallic surfaces [9]. They use single-stranded DNA both to act as an anchor to the gold or silver substrates and to selectively bind to the quantum dots, allowing programmed assembly of quantum dots on plasmonic structures. More recently still, researchers in Germany have reported how they can controllably reduce the density of self-assembled InP quantum dots by cyclic deposition with growth interruptions [10]. The impressive control has great potential for quantum emitter use. In this issue, Völk, Krenner and colleagues use an alternative approach to demonstrate how they can improve the performance of single-photon sources using SAWs. They use an optimized system of isolated self-assembled quantum posts in a quantum-well structure and inject the carriers at a distance from the posts where recombination and emission take place [3]. The SAW dissociates the electron-hole pairs and transports them to the quantum posts, so the two carrier types arrive at the quantum post with a set time delay. Other approaches, such as Coulomb blockade ones, have struggled to achieve the sequential injection of the carriers that results from this approach. As the authors explain, the result is a highly efficient process with greater stability at high acoustic powers compared with direct optical pumping at the position of the post: 'Our findings demonstrate that quantum posts with their surrounding wide matrix quantum well are an ideal system for the realization of a precisely triggered SAW-controlled single-photon source'. The work of Völk, Krenner and their co-authors draws on a vast range of developments in fundamental physics and nanotechnology. As is so often the case, how developments in one direction facilitate work in another is only really apparent in hindsight. In his Nobel Prize acceptance speech, Max Planck remarked: 'The whole strenuous intellectual work of an industrious research worker would appear, after all, in vain and hopeless, if he were not occasionally through some striking facts to find that he had, at the end of all his criss-cross journeys, at last accomplished at least one step which was conclusively nearer the truth' [11]. Whether the cumulative efforts of all the researchers in theoretical physics and technology mentioned here bring us closer to the truth, time will tell. But it seems quite likely that they will bring us closer to turning the quantum capabilities of science-fiction to reality. References [1] Völk S, Knall F, Schülein J R, Truong T A, Kim J, Petroff P M, Wixforth A and Krenner H J 2012 Surface acoustic wave mediated into individual quantum post nano emitters Nanotechnology 23 285201 [2] Patel R B, Bennett A J, Cooper K, Atkinson P, Nicoll A A, Ritchie D A and Shields A J 2010 Quantum interference of electrically generated single photons from a quantum dot Nanotechnology 21 274011 [3] Kim J, Benson O, Kan H and Yamamoto Y 1999 A single-photon turnstile device Nature 397 500-3 [4] Rocke C, Zimmermann S, Wixforth A, Kotthaus J P, Böhm G and Weimann G 1997 Acoustically driven storage of light in a quantum well Phys. Rev. Lett. 78 4099-102 [5] Sadek A Z, Wlodarski W, Shin K, Kaner R B and Kalantar-Zadeh K 2006 A layered surface acoustic wave gas sensor based on a polyaniline/In2O3 nanofibre composite Nanotechnology 17 4488-92 [6] Huang F-C, Chen Y-Y and Wu T-T 2009 A room temperature surface acoustic wave hydrogen sensor with Pt coated ZnO nanorods Nanotechnology 20 065501 [7] Sheng L, Dajing C and Yuquan C 2011 A surface acoustic wave humidity sensor with high sensitivity based on electrospun MWCNT/Nafion nanofiber films Nanotechnology 22 265504 [8] Friend J R, Yeo L Y, Arifin D R and Mechler A 2008 Evaporative self-assembly assisted synthesis of polymeric nanoparticles by surface acoustic wave atomization Nanotechnology 19 45301 [9] Kramer R K, Pholchai N, Sorger V J, Yim T J, Oulton R and Zhang X 2010 Positioning of quantum dots on metallic nanostructures Nanotechnology 21 145307 [10] Rödel R, Bauer A, Kremling S, Reitzenstein S, Höfling S, Kamp M, Worschech L and Forchel A 2012 Density and size control of InP/GaInP quantum dots on GaAs substrate grown by gas source molecular beam epitaxy Nanotechnology 23 015605 [11] The Official Website of the Nobel Prize http://www.nobelprize.org/nobel_prizes/physics/laureates/1918/planck-lecture.html

  13. Implementing Computer Technologies: Teachers' Perceptions and Practices

    ERIC Educational Resources Information Center

    Wozney, Lori; Venkatesh, Vivek; Abrami, Philip

    2006-01-01

    This study investigates personal and setting characteristics, teacher attitudes, and current computer technology practices among 764 elementary and secondary teachers from both private and public school sectors in Quebec. Using expectancy-value theory, the Technology Implementation Questionnaire (TIQ) was developed; it consists of 33 belief items

  14. Cloud Computing Technologies and Applications

    NASA Astrophysics Data System (ADS)

    Zhu, Jinzy

    In a nutshell, the existing Internet provides to us content in the forms of videos, emails and information served up in web pages. With Cloud Computing, the next generation of Internet will allow us to "buy" IT services from a web portal, drastic expanding the types of merchandise available beyond those on e-commerce sites such as eBay and Taobao. We would be able to rent from a virtual storefront the basic necessities to build a virtual data center: such as CPU, memory, storage, and add on top of that the middleware necessary: web application servers, databases, enterprise server bus, etc. as the platform(s) to support the applications we would like to either rent from an Independent Software Vendor (ISV) or develop ourselves. Together this is what we call as "IT as a Service," or ITaaS, bundled to us the end users as a virtual data center.

  15. Quantum computer aided design simulation and optimization of semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Gao, X.; Nielsen, E.; Muller, R. P.; Young, R. W.; Salinger, A. G.; Bishop, N. C.; Lilly, M. P.; Carroll, M. S.

    2013-10-01

    We present the Quantum Computer Aided Design (QCAD) simulator that targets modeling multi-dimensional quantum devices, particularly silicon multi-quantum dots (QDs) developed for quantum bits (qubits). This finite-element simulator has three differentiating features: (i) its core contains nonlinear Poisson, effective mass Schrodinger, and Configuration Interaction solvers that have massively parallel capability for high simulation throughput and can be run individually or combined self-consistently for 1D/2D/3D quantum devices; (ii) the core solvers show superior convergence even at near-zero-Kelvin temperatures, which is critical for modeling quantum computing devices; and (iii) it interfaces directly with the full-featured optimization engine Dakota. In this work, we describe the capabilities and implementation of the QCAD simulation tool and show how it can be used to both analyze existing experimental QD devices through capacitance calculations and aid in the design of few-electron multi-QDs. In particular, we observe that computed capacitances are in rough agreement with experiment, and that quantum confinement increases capacitance when the number of electrons is fixed in a quantum dot. Coupling of QCAD with the optimizer Dakota allows for rapid identification and improvement of device layouts that are likely to exhibit few-electron quantum dot characteristics.

  16. Research on Key Technologies of Cloud Computing

    NASA Astrophysics Data System (ADS)

    Zhang, Shufen; Yan, Hongcan; Chen, Xuebin

    With the development of multi-core processors, virtualization, distributed storage, broadband Internet and automatic management, a new type of computing mode named cloud computing is produced. It distributes computation task on the resource pool which consists of massive computers, so the application systems can obtain the computing power, the storage space and software service according to its demand. It can concentrate all the computing resources and manage them automatically by the software without intervene. This makes application offers not to annoy for tedious details and more absorbed in his business. It will be advantageous to innovation and reduce cost. It's the ultimate goal of cloud computing to provide calculation, services and applications as a public facility for the public, So that people can use the computer resources just like using water, electricity, gas and telephone. Currently, the understanding of cloud computing is developing and changing constantly, cloud computing still has no unanimous definition. This paper describes three main service forms of cloud computing: SAAS, PAAS, IAAS, compared the definition of cloud computing which is given by Google, Amazon, IBM and other companies, summarized the basic characteristics of cloud computing, and emphasized on the key technologies such as data storage, data management, virtualization and programming model.

  17. Culture Computing: Interactive Technology to Explore Culture

    NASA Astrophysics Data System (ADS)

    Cheok, Adrian David

    The present day rapid development of media science and digital technology is offering the modern generation more opportunities as well as challenges as the new fundamental literacy. Therefore, to reach the modern generation on issues such as an appreciation of cultures, we have to find common grounds based on digital media technology. In an increasingly hybrid cultural environment, interaction and fusion of cultural factors with the computer technology will be an investigation into the possibilities of providing an experience into the cultures of the world, operating in the environments the modern generation inhabits. Research has created novel merging of traditional cultures and literature with recent media literacy. Three cultural computing systems, Media Me, BlogWall and Confucius Computer, are presented in this chapter. Studies showed that users gave positive feedback to their experience of interacting with cultural computing systems.

  18. A quantum computer in the scheme of an atomic quantum transistor with logical encoding of qubits

    NASA Astrophysics Data System (ADS)

    Moiseev, S. A.; Andrianov, S. N.; Moiseev, E. S.

    2013-09-01

    A scheme of a multiqubit quantum computer on atomic ensembles using a quantum transistor implementing two qubit gates is proposed. We demonstrate how multiatomic ensembles permit one to work with a large number of qubits that are represented in a logical encoding in which each qubit is recorded on a superposition of single-particle states of two atomic ensembles. The access to qubits is implemented by appropriate phasing of quantum states of each of atomic ensembles. An atomic quantum transistor is proposed for use when executing two qubit operations. The quantum transistor effect appears when an excitation quantum is exchanged between two multiatomic ensembles located in two closely positioned QED cavities connected with each other by a gate atom. The dynamics of quantum transfer between atomic ensembles can be different depending on one of two states of the gate atom. Using the possibilities of control for of state of the gate atom, we show the possibility of quantum control for the state of atomic ensembles and, based on this, implementation of basic single and two qubit gates. Possible implementation schemes for a quantum computer on an atomic quantum transistor and their advantages in practical implementation are discussed.

  19. Solving strongly correlated electron models on a quantum computer

    NASA Astrophysics Data System (ADS)

    Wecker, Dave; Hastings, Matthew B.; Wiebe, Nathan; Clark, Bryan K.; Nayak, Chetan; Troyer, Matthias

    2015-12-01

    One of the main applications of future quantum computers will be the simulation of quantum models. While the evolution of a quantum state under a Hamiltonian is straightforward (if sometimes expensive), using quantum computers to determine the ground-state phase diagram of a quantum model and the properties of its phases is more involved. Using the Hubbard model as a prototypical example, we here show all the steps necessary to determine its phase diagram and ground-state properties on a quantum computer. In particular, we discuss strategies for efficiently determining and preparing the ground state of the Hubbard model starting from various mean-field states with broken symmetry. We present an efficient procedure to prepare arbitrary Slater determinants as initial states and present the complete set of quantum circuits needed to evolve from these to the ground state of the Hubbard model. We show that, using efficient nesting of the various terms, each time step in the evolution can be performed with just O (N ) gates and O (logN ) circuit depth. We give explicit circuits to measure arbitrary local observables and static and dynamic correlation functions, in both the time and the frequency domains. We further present efficient nondestructive approaches to measurement that avoid the need to reprepare the ground state after each measurement and that quadratically reduce the measurement error.

  20. Robustness and device independence of verifiable blind quantum computing

    NASA Astrophysics Data System (ADS)

    Gheorghiu, Alexandru; Kashefi, Elham; Wallden, Petros

    2015-08-01

    Recent advances in theoretical and experimental quantum computing bring us closer to scalable quantum computing devices. This makes the need for protocols that verify the correct functionality of quantum operations timely and has led to the field of quantum verification. In this paper we address key challenges to make quantum verification protocols applicable to experimental implementations. We prove the robustness of the single server verifiable universal blind quantum computing protocol of Fitzsimons and Kashefi (2012 arXiv:1203.5217) in the most general scenario. This includes the case where the purification of the deviated input state is in the hands of an adversarial server. The proved robustness property allows the composition of this protocol with a device-independent state tomography protocol that we give, which is based on the rigidity of CHSH games as proposed by Reichardt et al (2013 Nature 496 456-60). The resulting composite protocol has lower round complexity for the verification of entangled quantum servers with a classical verifier and, as we show, can be made fault tolerant.

  1. Quantum computing on lattices using global two-qubit gates

    SciTech Connect

    Ivanyos, G.; Massar, S.; Nagy, A. B.

    2005-08-15

    We study the computation power of lattices composed of two-dimensional systems (qubits) on which translationally invariant global two-qubit gates can be performed. We show that if a specific set of six global two qubit gates can be performed and if the initial state of the lattice can be suitably chosen, then a quantum computer can be efficiently simulated.

  2. Dominant strategies in two-qubit quantum computations

    NASA Astrophysics Data System (ADS)

    Khan, Faisal Shah

    2015-06-01

    Nash equilibrium is a solution concept in non-strictly competitive, noncooperative game theory that finds applications in various scientific and engineering disciplines. A non-strictly competitive, noncooperative game model is presented here for two-qubit quantum computations that allows for the characterization of Nash equilibrium in these computations via the inner product of their state space. Nash equilibrium outcomes are optimal under given constraints and therefore offer a game-theoretic measure of constrained optimization of two-qubit quantum computations.

  3. Entanglement-based machine learning on a quantum computer.

    PubMed

    Cai, X-D; Wu, D; Su, Z-E; Chen, M-C; Wang, X-L; Li, Li; Liu, N-L; Lu, C-Y; Pan, J-W

    2015-03-20

    Machine learning, a branch of artificial intelligence, learns from previous experience to optimize performance, which is ubiquitous in various fields such as computer sciences, financial analysis, robotics, and bioinformatics. A challenge is that machine learning with the rapidly growing "big data" could become intractable for classical computers. Recently, quantum machine learning algorithms [Lloyd, Mohseni, and Rebentrost, arXiv.1307.0411] were proposed which could offer an exponential speedup over classical algorithms. Here, we report the first experimental entanglement-based classification of two-, four-, and eight-dimensional vectors to different clusters using a small-scale photonic quantum computer, which are then used to implement supervised and unsupervised machine learning. The results demonstrate the working principle of using quantum computers to manipulate and classify high-dimensional vectors, the core mathematical routine in machine learning. The method can, in principle, be scaled to larger numbers of qubits, and may provide a new route to accelerate machine learning. PMID:25839250

  4. Entanglement-Based Machine Learning on a Quantum Computer

    NASA Astrophysics Data System (ADS)

    Cai, X.-D.; Wu, D.; Su, Z.-E.; Chen, M.-C.; Wang, X.-L.; Li, Li; Liu, N.-L.; Lu, C.-Y.; Pan, J.-W.

    2015-03-01

    Machine learning, a branch of artificial intelligence, learns from previous experience to optimize performance, which is ubiquitous in various fields such as computer sciences, financial analysis, robotics, and bioinformatics. A challenge is that machine learning with the rapidly growing "big data" could become intractable for classical computers. Recently, quantum machine learning algorithms [Lloyd, Mohseni, and Rebentrost, arXiv.1307.0411] were proposed which could offer an exponential speedup over classical algorithms. Here, we report the first experimental entanglement-based classification of two-, four-, and eight-dimensional vectors to different clusters using a small-scale photonic quantum computer, which are then used to implement supervised and unsupervised machine learning. The results demonstrate the working principle of using quantum computers to manipulate and classify high-dimensional vectors, the core mathematical routine in machine learning. The method can, in principle, be scaled to larger numbers of qubits, and may provide a new route to accelerate machine learning.

  5. Requirements for fault-tolerant factoring on an atom-optics quantum computer

    NASA Astrophysics Data System (ADS)

    Devitt, Simon J.; Stephens, Ashley M.; Munro, William J.; Nemoto, Kae

    2013-10-01

    Quantum information processing and its associated technologies have reached a pivotal stage in their development, with many experiments having established the basic building blocks. Moving forward, the challenge is to scale up to larger machines capable of performing computational tasks not possible today. This raises questions that need to be urgently addressed, such as what resources these machines will consume and how large will they be. Here we estimate the resources required to execute Shors factoring algorithm on an atom-optics quantum computer architecture. We determine the runtime and size of the computer as a function of the problem size and physical error rate. Our results suggest that once the physical error rate is low enough to allow quantum error correction, optimization to reduce resources and increase performance will come mostly from integrating algorithms and circuits within the error correction environment, rather than from improving the physical hardware.

  6. Bifurcation-based adiabatic quantum computation with a nonlinear oscillator network

    NASA Astrophysics Data System (ADS)

    Goto, Hayato

    2016-02-01

    The dynamics of nonlinear systems qualitatively change depending on their parameters, which is called bifurcation. A quantum-mechanical nonlinear oscillator can yield a quantum superposition of two oscillation states, known as a Schrödinger cat state, via quantum adiabatic evolution through its bifurcation point. Here we propose a quantum computer comprising such quantum nonlinear oscillators, instead of quantum bits, to solve hard combinatorial optimization problems. The nonlinear oscillator network finds optimal solutions via quantum adiabatic evolution, where nonlinear terms are increased slowly, in contrast to conventional adiabatic quantum computation or quantum annealing, where quantum fluctuation terms are decreased slowly. As a result of numerical simulations, it is concluded that quantum superposition and quantum fluctuation work effectively to find optimal solutions. It is also notable that the present computer is analogous to neural computers, which are also networks of nonlinear components. Thus, the present scheme will open new possibilities for quantum computation, nonlinear science, and artificial intelligence.

  7. Bifurcation-based adiabatic quantum computation with a nonlinear oscillator network.

    PubMed

    Goto, Hayato

    2016-01-01

    The dynamics of nonlinear systems qualitatively change depending on their parameters, which is called bifurcation. A quantum-mechanical nonlinear oscillator can yield a quantum superposition of two oscillation states, known as a Schrödinger cat state, via quantum adiabatic evolution through its bifurcation point. Here we propose a quantum computer comprising such quantum nonlinear oscillators, instead of quantum bits, to solve hard combinatorial optimization problems. The nonlinear oscillator network finds optimal solutions via quantum adiabatic evolution, where nonlinear terms are increased slowly, in contrast to conventional adiabatic quantum computation or quantum annealing, where quantum fluctuation terms are decreased slowly. As a result of numerical simulations, it is concluded that quantum superposition and quantum fluctuation work effectively to find optimal solutions. It is also notable that the present computer is analogous to neural computers, which are also networks of nonlinear components. Thus, the present scheme will open new possibilities for quantum computation, nonlinear science, and artificial intelligence. PMID:26899997

  8. Bifurcation-based adiabatic quantum computation with a nonlinear oscillator network

    PubMed Central

    Goto, Hayato

    2016-01-01

    The dynamics of nonlinear systems qualitatively change depending on their parameters, which is called bifurcation. A quantum-mechanical nonlinear oscillator can yield a quantum superposition of two oscillation states, known as a Schrödinger cat state, via quantum adiabatic evolution through its bifurcation point. Here we propose a quantum computer comprising such quantum nonlinear oscillators, instead of quantum bits, to solve hard combinatorial optimization problems. The nonlinear oscillator network finds optimal solutions via quantum adiabatic evolution, where nonlinear terms are increased slowly, in contrast to conventional adiabatic quantum computation or quantum annealing, where quantum fluctuation terms are decreased slowly. As a result of numerical simulations, it is concluded that quantum superposition and quantum fluctuation work effectively to find optimal solutions. It is also notable that the present computer is analogous to neural computers, which are also networks of nonlinear components. Thus, the present scheme will open new possibilities for quantum computation, nonlinear science, and artificial intelligence. PMID:26899997

  9. On the 'principle of the quantumness', the quantumness of Relativity, and the computational grand-unification

    SciTech Connect

    D'Ariano, Giacomo Mauro

    2010-05-04

    I will argue that the proposal of establishing operational foundations of Quantum Theory should have top-priority, and that the Lucien Hardy's program on Quantum Gravity should be paralleled by an analogous program on Quantum Field Theory (QFT), which needs to be reformulated, notwithstanding its experimental success. In this paper, after reviewing recently suggested operational 'principles of the quantumness', I address the problem on whether Quantum Theory and Special Relativity are unrelated theories, or instead, if the one implies the other. I show how Special Relativity can be indeed derived from causality of Quantum Theory, within the computational paradigm 'the universe is a huge quantum computer', reformulating QFT as a Quantum-Computational Field Theory (QCFT). In QCFT Special Relativity emerges from the fabric of the computational network, which also naturally embeds gauge invariance. In this scheme even the quantization rule and the Planck constant can in principle be derived as emergent from the underlying causal tapestry of space-time. In this way Quantum Theory remains the only theory operating the huge computer of the universe.Is the computational paradigm only a speculative tautology (theory as simulation of reality), or does it have a scientific value? The answer will come from Occam's razor, depending on the mathematical simplicity of QCFT. Here I will just start scratching the surface of QCFT, analyzing simple field theories, including Dirac's. The number of problems and unmotivated recipes that plague QFT strongly motivates us to undertake the QCFT project, since QCFT makes all such problems manifest, and forces a re-foundation of QFT.

  10. On the ``principle of the quantumness,'' the quantumness of Relativity, and the computational grand-unification

    NASA Astrophysics Data System (ADS)

    D'Ariano, Giacomo Mauro

    2010-05-01

    I will argue that the proposal of establishing operational foundations of Quantum Theory should have top-priority, and that the Lucien Hardy's program on Quantum Gravity should be paralleled by an analogous program on Quantum Field Theory (QFT), which needs to be reformulated, notwithstanding its experimental success. In this paper, after reviewing recently suggested operational "principles of the quantumness," I address the problem on whether Quantum Theory and Special Relativity are unrelated theories, or instead, if the one implies the other. I show how Special Relativity can be indeed derived from causality of Quantum Theory, within the computational paradigm "the universe is a huge quantum computer," reformulating QFT as a Quantum-Computational Field Theory (QCFT). In QCFT Special Relativity emerges from the fabric of the computational network, which also naturally embeds gauge invariance. In this scheme even the quantization rule and the Planck constant can in principle be derived as emergent from the underlying causal tapestry of space-time. In this way Quantum Theory remains the only theory operating the huge computer of the universe. Is the computational paradigm only a speculative tautology (theory as simulation of reality), or does it have a scientific value? The answer will come from Occam's razor, depending on the mathematical simplicity of QCFT. Here I will just start scratching the surface of QCFT, analyzing simple field theories, including Dirac's. The number of problems and unmotivated recipes that plague QFT strongly motivates us to undertake the QCFT project, since QCFT makes all such problems manifest, and forces a re-foundation of QFT.

  11. Combining dynamical decoupling with fault-tolerant quantum computation

    SciTech Connect

    Ng, Hui Khoon; Preskill, John; Lidar, Daniel A.

    2011-07-15

    We study how dynamical decoupling (DD) pulse sequences can improve the reliability of quantum computers. We prove upper bounds on the accuracy of DD-protected quantum gates and derive sufficient conditions for DD-protected gates to outperform unprotected gates. Under suitable conditions, fault-tolerant quantum circuits constructed from DD-protected gates can tolerate stronger noise and have a lower overhead cost than fault-tolerant circuits constructed from unprotected gates. Our accuracy estimates depend on the dynamics of the bath that couples to the quantum computer and can be expressed either in terms of the operator norm of the bath's Hamiltonian or in terms of the power spectrum of bath correlations; we explain in particular how the performance of recursively generated concatenated pulse sequences can be analyzed from either viewpoint. Our results apply to Hamiltonian noise models with limited spatial correlations.

  12. Scheme for Entering Binary Data Into a Quantum Computer

    NASA Technical Reports Server (NTRS)

    Williams, Colin

    2005-01-01

    A quantum algorithm provides for the encoding of an exponentially large number of classical data bits by use of a smaller (polynomially large) number of quantum bits (qubits). The development of this algorithm was prompted by the need, heretofore not satisfied, for a means of entering real-world binary data into a quantum computer. The data format provided by this algorithm is suitable for subsequent ultrafast quantum processing of the entered data. Potential applications lie in disciplines (e.g., genomics) in which one needs to search for matches between parts of very long sequences of data. For example, the algorithm could be used to encode the N-bit-long human genome in only log2N qubits. The resulting log2N-qubit state could then be used for subsequent quantum data processing - for example, to perform rapid comparisons of sequences.

  13. Photon echo quantum random access memory integration in a quantum computer

    NASA Astrophysics Data System (ADS)

    Moiseev, Sergey A.; Andrianov, Sergey N.

    2012-06-01

    We have analysed an efficient integration of multi-qubit echo quantum memory (QM) into the quantum computer scheme based on squids, quantum dots or atomic resonant ensembles in a quantum electrodynamics cavity. Here, one atomic ensemble with controllable inhomogeneous broadening is used for the QM node and other nodes characterized by the homogeneously broadened resonant line are used for processing. We have found the optimal conditions for the efficient integration of the multi-qubit QM modified for the analysed scheme, and we have determined the self-temporal modes providing a perfect reversible transfer of the photon qubits between the QM node and arbitrary processing nodes. The obtained results open the way for realization of a full-scale solid state quantum computing based on the efficient multi-qubit QM.

  14. Preparing topological projected entangled pair states on a quantum computer

    NASA Astrophysics Data System (ADS)

    Schwarz, Martin; Temme, Kristan; Verstraete, Frank; Perez-Garcia, David; Cubitt, Toby S.

    2013-09-01

    Simulating exotic phases of matter that are not amenable to classical techniques is one of the most important potential applications of quantum information processing. We present an efficient algorithm for preparing a large class of topological quantum states, the G-injective projected entangled pair states (PEPS), on a quantum computer. Important examples include the resonant valence bond states, conjectured to be topological spin liquids. The runtime of the algorithm scales polynomially with the condition number of the PEPS projectors and inverse polynomially in the spectral gap of the PEPS parent Hamiltonian.

  15. Computer studies of multiple-quantum spin dynamics

    SciTech Connect

    Murdoch, J.B.

    1982-11-01

    The excitation and detection of multiple-quantum (MQ) transitions in Fourier transform NMR spectroscopy is an interesting problem in the quantum mechanical dynamics of spin systems as well as an important new technique for investigation of molecular structure. In particular, multiple-quantum spectroscopy can be used to simplify overly complex spectra or to separate the various interactions between a nucleus and its environment. The emphasis of this work is on computer simulation of spin-system evolution to better relate theory and experiment.

  16. Individual addressing in quantum computation through spatial refocusing

    NASA Astrophysics Data System (ADS)

    Shen, C.; Gong, Z.-X.; Duan, L.-M.

    2013-11-01

    Separate addressing of individual qubits is a challenging requirement for scalable quantum computation, and crosstalk between operations on neighboring qubits remains a significant source of error for current experimental implementations of multiqubit platforms. We propose a scheme based on spatial refocusing from interference of several coherent laser beams to significantly reduce the crosstalk error for any type of quantum gate. A general framework is developed for the spatial refocusing technique, in particular with practical Gaussian beams, and we show that the crosstalk-induced infidelity of quantum gates can be reduced by several orders of magnitude with a moderate cost of a few correction laser beams under typical experimental conditions.

  17. Concatenated logical cluster state for measurement-based quantum computation

    NASA Astrophysics Data System (ADS)

    Joo, Jaewoo

    2010-03-01

    The highly entangled quantum states known as cluster states constitute a universal resource for measurement-based quantum computing (MBQC). How to construct a fault-tolerant protocol for MBQC is still an open question, however. We show how to build concatenated cluster states for MBQC using the five-qubit quantum error-correcting code. These states can be built by a series of single-qubit Hadamard and two-qubit controlled-phase gates. The number of operations is significantly reduced through the use of local complementation graph operations. Error thresholds are investigated and compared with current experimental capabilities.

  18. Exploiting geometric degrees of freedom in topological quantum computing

    SciTech Connect

    Xu Haitan; Wan Xin

    2009-07-15

    In a topological quantum computer, braids of non-Abelian anyons in a (2+1)-dimensional space time form quantum gates, whose fault tolerance relies on the topological, rather than geometric, properties of the braids. Here we propose to create and exploit redundant geometric degrees of freedom to improve the theoretical accuracy of topological single- and two-qubit quantum gates. We demonstrate the power of the idea using explicit constructions in the Fibonacci model. We compare its efficiency with that of the Solovay-Kitaev algorithm and explain its connection to the leakage errors reduction in an earlier construction [H. Xu and X. Wan, Phys. Rev. A 78, 042325 (2008)].

  19. Limitations of quantum computing with Gaussian cluster states

    SciTech Connect

    Ohliger, M.; Kieling, K.; Eisert, J.

    2010-10-15

    We discuss the potential and limitations of Gaussian cluster states for measurement-based quantum computing. Using a framework of Gaussian-projected entangled pair states, we show that no matter what Gaussian local measurements are performed on systems distributed on a general graph, transport and processing of quantum information are not possible beyond a certain influence region, except for exponentially suppressed corrections. We also demonstrate that even under arbitrary non-Gaussian local measurements, slabs of Gaussian cluster states of a finite width cannot carry logical quantum information, even if sophisticated encodings of qubits in continuous-variable systems are allowed for. This is proven by suitably contracting tensor networks representing infinite-dimensional quantum systems. The result can be seen as sharpening the requirements for quantum error correction and fault tolerance for Gaussian cluster states and points toward the necessity of non-Gaussian resource states for measurement-based quantum computing. The results can equally be viewed as referring to Gaussian quantum repeater networks.

  20. How to teach an old dog new tricks: Quantum information, quantum computation, and the philosophy of physics

    NASA Astrophysics Data System (ADS)

    Duwell, Armond

    My dissertation consists of two independent parts. Part one of my dissertation examines concepts of quantum information. I clarify three very different concepts of information and assess their implications for understanding quantum mechanics. First I clarify the concept of information due to Shannon, and its relation to physical theories. Using the Shannon concept, I examine two purportedly new concepts of quantum information. I argue that a fundamental philosophical mistake is made regarding these concepts. Advocates of these new concepts do not properly distinguish between the properties of information due to the physical medium it is stored in from the properties of information per se. This distinction is crucial for developing a new concept to help us understand quantum mechanics and evaluating its merits. Part two of my dissertation examines explanations of the efficiency that quantum computers enjoy over classical computers for some computational tasks, and the relationship between explanations of efficiency and interpretations of quantum mechanics. I examine the so-called quantum parallelism thesis, that quantum computers can perform many computations in a single step, a feat thought not to be possible on classical computers. The truth of this thesis is not obvious, and contested by some. I develop a set of general criteria for computation that any computing device must satisfy. I use these criteria to demonstrate that the quantum parallelism thesis is true. As an application of these general criteria for computation I articulate three distinct concepts of parallelism and demonstrate that classical computers can compute in parallel as well. This demonstrates that the truth of the quantum parallelism thesis alone does not provide a complete explanation of the efficiency of quantum computers. I supplement the quantum parallelism thesis to provide a complete explanation. Finally, I address the claim that only the many-worlds interpretation of quantum mechanics can underwrite the truth of the quantum parallelism thesis. The general criteria for computation provide support for the quantum parallelism thesis independent of any interpretation of quantum mechanics.

  1. Universal Matchgate Quantum Computing With Cold Polar Molecules

    NASA Astrophysics Data System (ADS)

    Herrera, Felipe

    2015-03-01

    Polar molecules in optical lattices are attractive for quantum simulation and computation due to the ability to implement a variety of spin-lattice models using static, microwave and optical fields to engineer the long-range dipolar interaction between molecular qubits. Quantum simulation of spin models requires global control over the molecular ensemble, while quantum computation requires control of individual molecules with sub-wavelength resolution. In this talk, we describe the implementation of a matchgate quantum processor with an ensemble of polar molecules in an optical lattice. The scheme uses few-body qubit encoding and sequential control of two-body dipolar interactions over small plaquetes on a square lattice to perform universal quantum computing without single-site addressing. Effective spin-spin interactions with matchgate symmetry between open-shell polar molecules (e.g., SrF, OH) are driven by two infrared control pulses in the absence of static electric fields. The resulting matchgates are robust with respect to realistic imperfections in the driving fields and lattice trapping. Applications of the architecture for the simulation of interacting fermions in quantum chemistry are discussed, considering an imperfect lattice filling.

  2. Computational Bottlenecks of Quantum Adiabatic Annealing

    NASA Astrophysics Data System (ADS)

    Knysh, Sergey

    2015-03-01

    Quantum annealing in a transverse field with rate d? / dt inversely proportional to the system size N suppresses non-adiabatic transitions for fully connected spin glass such as the Sherrington-Kirpatrick (SK) model at the quantum critical point. This alone is not sufficient to ensure that the problem is solvable in polynomial time. I conjecture the appearance of small gaps associated with macroscopic tunneling events deep in the spin glass phase. This effect is demonstrated rigorously for the annealing of a toy model that shares a set of crtical exponents with SK model: Hopfield network with two Gaussian patterns. It presents with 0 . 15 lnN additional bottlenecks with gaps that scale as a stretched exponential exp[-c (N?) 3 / 4]. Further, I extend the analysis to the ?-landscapes model (random energy model with correlations) which more faithfully represents real spin glasses.

  3. Degree of quantum correlation required to speed up a computation

    NASA Astrophysics Data System (ADS)

    Kay, Alastair

    2015-12-01

    The one-clean-qubit model of quantum computation (DQC1) efficiently implements a computational task that is not known to have a classical alternative. During the computation, there is never more than a small but finite amount of entanglement present, and it is typically vanishingly small in the system size. In this paper, we demonstrate that there is nothing unexpected hidden within the DQC1 model—Grover's search, when acting on a mixed state, provably exhibits a speedup over classical, with guarantees as to the presence of only vanishingly small amounts of quantum correlations (entanglement and quantum discord)—while arguing that this is not an artifact of the oracle-based construction. We also present some important refinements in the evaluation of how much entanglement may be present in the DQC1 and how the typical entanglement of the system must be evaluated.

  4. Ground-state geometric quantum computing in superconducting systems

    SciTech Connect

    Solinas, P.; Moettoenen, M.

    2010-11-15

    We present a theoretical proposal for the implementation of geometric quantum computing based on a Hamiltonian which has a doubly degenerate ground state. Thus the system which is steered adiabatically, remains in the ground-state. The proposed physical implementation relies on a superconducting circuit composed of three SQUIDs and two superconducting islands with the charge states encoding the logical states. We obtain a universal set of single-qubit gates and implement a nontrivial two-qubit gate exploiting the mutual inductance between two neighboring circuits, allowing us to realize a fully geometric ground-state quantum computing. The introduced paradigm for the implementation of geometric quantum computing is expected to be robust against environmental effects.

  5. Dynamical localization simulated on a few-qubit quantum computer

    SciTech Connect

    Benenti, Giuliano; Montangero, Simone; Casati, Giulio; Shepelyansky, Dima L.

    2003-05-01

    We show that a quantum computer operating with a small number of qubits can simulate the dynamical localization of classical chaos in a system described by the quantum sawtooth map model. The dynamics of the system is computed efficiently up to a time t{>=}l, and then the localization length l can be obtained with accuracy {nu} by means of order 1/{nu}{sup 2} computer runs, followed by coarse-grained projective measurements on the computational basis. We also show that in the presence of static imperfections, a reliable computation of the localization length is possible without error correction up to an imperfection threshold which drops polynomially with the number of qubits.

  6. Nano-Bio Quantum Technology for Device-Specific Materials

    NASA Technical Reports Server (NTRS)

    Choi, Sang H.

    2009-01-01

    The areas discussed are still under development: I. Nano structured materials for TE applications a) SiGe and Be.Te; b) Nano particles and nanoshells. II. Quantum technology for optical devices: a) Quantum apertures; b) Smart optical materials; c) Micro spectrometer. III. Bio-template oriented materials: a) Bionanobattery; b) Bio-fuel cells; c) Energetic materials.

  7. Quantum Computation under Micromotion in a Planar Ion Crystal

    PubMed Central

    Wang, S.-T.; Shen, C.; Duan, L.-M.

    2015-01-01

    We propose a scheme to realize scalable quantum computation in a planar ion crystal confined by a Paul trap. We show that the inevitable in-plane micromotion affects the gate design via three separate effects: renormalization of the equilibrium positions, coupling to the transverse motional modes, and amplitude modulation in the addressing beam. We demonstrate that all of these effects can be taken into account and high-fidelity gates are possible in the presence of micromotion. This proposal opens the prospect to realize large-scale fault-tolerant quantum computation within a single Paul trap. PMID:25711774

  8. Quantum computation under micromotion in a planar ion crystal.

    PubMed

    Wang, S-T; Shen, C; Duan, L-M

    2015-01-01

    We propose a scheme to realize scalable quantum computation in a planar ion crystal confined by a Paul trap. We show that the inevitable in-plane micromotion affects the gate design via three separate effects: renormalization of the equilibrium positions, coupling to the transverse motional modes, and amplitude modulation in the addressing beam. We demonstrate that all of these effects can be taken into account and high-fidelity gates are possible in the presence of micromotion. This proposal opens the prospect to realize large-scale fault-tolerant quantum computation within a single Paul trap. PMID:25711774

  9. Magnetic resonance force microscopy and a solid state quantum computer.

    SciTech Connect

    Pelekhov, D. V.; Martin, I.; Suter, A.; Reagor, D. W.; Hammel, P. C.

    2001-01-01

    A Quantum Computer (QC) is a device that utilizes the principles of Quantum Mechanics to perform computations. Such a machine would be capable of accomplishing tasks not achievable by means of any conventional digital computer, for instance factoring large numbers. Currently it appears that the QC architecture based on an array of spin quantum bits (qubits) embedded in a solid-state matrix is one of the most promising approaches to fabrication of a scalable QC. However, the fabrication and operation of a Solid State Quantum Computer (SSQC) presents very formidable challenges; primary amongst these are: (1) the characterization and control of the fabrication process of the device during its construction and (2) the readout of the computational result. Magnetic Resonance Force Microscopy (MRFM)--a novel scanning probe technique based on mechanical detection of magnetic resonance-provides an attractive means of addressing these requirements. The sensitivity of the MRFM significantly exceeds that of conventional magnetic resonance measurement methods, and it has the potential for single electron spin detection. Moreover, the MRFM is capable of true 3D subsurface imaging. These features will make MRFM an invaluable tool for the implementation of a spin-based QC. Here we present the general principles of MRFM operation, the current status of its development and indicate future directions for its improvement.

  10. Publishing a School Newspaper Using Computer Technology.

    ERIC Educational Resources Information Center

    Whitney, Jeanne; And Others

    By publishing a quarterly school and community newspaper, sixth, seventh, and eighth graders get involved in the writing of many types of articles, proofreading, communication skills, interviewing skills, investigative reporting, photography, artistic and graphic design, and computer technology. As the students work together on each issue of the

  11. Computer Science & Technology: Local Area Networking.

    ERIC Educational Resources Information Center

    Cotton, Ira W., Ed.

    The different technologies applicable to computer networks serving limited geographic areas, e.g., a single campus, factory, or office complex, are discussed in a number of short presentations made by active researchers and implementers in this field. Intensive discussion by participants in working sessions is reported for six topics: subnet

  12. Computer Servicing Technology. Florida Vocational Program Guide.

    ERIC Educational Resources Information Center

    University of South Florida, Tampa. Dept. of Adult and Vocational Education.

    This program guide identifies primary concerns in the organization, operation, and evaluation of a computer servicing technology program. It is designed for local school district and community college administrators, instructors, program advisory committees, and regional coordinating councils. The guide begins with the Dictionary of Occupational…

  13. Women Workers as Users of Computer Technology.

    ERIC Educational Resources Information Center

    Larwood, Laurie

    1992-01-01

    Discussion of expectations, trends, and implications of growth of computer technology and its effect on women workers argues that the experience of women is different from that of men in the nature of jobs in which women are found, their training and education, home-family conflict, and discrimination. The impact on women of increasing

  14. Computing the Real Costs of School Technology.

    ERIC Educational Resources Information Center

    Beaudin, James A.; Sells, Jeffrey A.

    1999-01-01

    Computers and other new technologies are changing how school buildings must be designed. Introduces full range of building designs that high-tech learning necessitates. Tables present unit costs for many infrastructural and network electronics components of advanced telecommunication systems now being installed in schools. A hypothetical case

  15. Competency Index. [Business/Computer Technologies Cluster.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center on Education and Training for Employment.

    This index allows the user to scan the competencies under each title for the 28 subjects appropriate for use in a competency list for the 12 occupations within the business/computer technologies cluster. Titles of the 28 units are as follows: employability skills; professionalism; teamwork; professional and ethical standards; economic and business

  16. Business/Computer Technologies. State Competency Profile.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center on Education and Training for Employment.

    This document contains 272 competencies, grouped into 36 units, for tech prep programs in the business/computer technology cluster. The competencies were developed through collaboration of Ohio business, industry, and labor representatives and secondary and associate degree educators. The competencies are rated either "essential" (necessary to

  17. Quantum annealing: The fastest route to quantum computation?

    NASA Astrophysics Data System (ADS)

    Smorra, C.; Blaum, K.; Bojtar, L.; Borchert, M.; Franke, K. A.; Higuchi, T.; Leefer, N.; Nagahama, H.; Matsuda, Y.; Mooser, A.; Niemann, M.; Ospelkaus, C.; Quint, W.; Schneider, G.; Sellner, S.; Tanaka, T.; Van Gorp, S.; Walz, J.; Yamazaki, Y.; Ulmer, S.

    2015-11-01

    The Baryon Antibaryon Symmetry Experiment (BASE) aims at performing a stringent test of the combined charge parity and time reversal (CPT) symmetry by comparing the magnetic moments of the proton and the antiproton with high precision. Using single particles in a Penning trap, the proton/antiproton g-factors, i.e. the magnetic moment in units of the nuclear magneton, are determined by measuring the respective ratio of the spin-precession frequency to the cyclotron frequency. The spin precession frequency is measured by non-destructive detection of spin quantum transitions using the continuous Stern-Gerlach effect, and the cyclotron frequency is determined from the particle*s motional eigenfrequencies in the Penning trap using the invariance theorem. By application of the double Penning-trap method we expect that in our measurements a fractional precision of ? g/ g 10-9 can be achieved. The successful application of this method to the antiproton will consist a factor 1000 improvement in the fractional precision of its magnetic moment. The BASE collaboration has constructed and commissioned a new experiment at the Antiproton Decelerator (AD) of CERN. This article describes and summarizes the physical and technical aspects of this new experiment.

  18. Evaluation of Advanced Computing Techniques and Technologies: Reconfigurable Computing

    NASA Technical Reports Server (NTRS)

    Wells, B. Earl

    2003-01-01

    The focus of this project was to survey the technology of reconfigurable computing determine its level of maturity and suitability for NASA applications. To better understand and assess the effectiveness of the reconfigurable design paradigm that is utilized within the HAL-15 reconfigurable computer system. This system was made available to NASA MSFC for this purpose, from Star Bridge Systems, Inc. To implement on at least one application that would benefit from the performance levels that are possible with reconfigurable hardware. It was originally proposed that experiments in fault tolerance and dynamically reconfigurability would be perform but time constraints mandated that these be pursued as future research.

  19. Deterministic entanglement distillation for secure double-server blind quantum computation.

    PubMed

    Sheng, Yu-Bo; Zhou, Lan

    2015-01-01

    Blind quantum computation (BQC) provides an efficient method for the client who does not have enough sophisticated technology and knowledge to perform universal quantum computation. The single-server BQC protocol requires the client to have some minimum quantum ability, while the double-server BQC protocol makes the client's device completely classical, resorting to the pure and clean Bell state shared by two servers. Here, we provide a deterministic entanglement distillation protocol in a practical noisy environment for the double-server BQC protocol. This protocol can get the pure maximally entangled Bell state. The success probability can reach 100% in principle. The distilled maximally entangled states can be remaind to perform the BQC protocol subsequently. The parties who perform the distillation protocol do not need to exchange the classical information and they learn nothing from the client. It makes this protocol unconditionally secure and suitable for the future BQC protocol. PMID:25588565

  20. Deterministic entanglement distillation for secure double-server blind quantum computation

    PubMed Central

    Sheng, Yu-Bo; Zhou, Lan

    2015-01-01

    Blind quantum computation (BQC) provides an efficient method for the client who does not have enough sophisticated technology and knowledge to perform universal quantum computation. The single-server BQC protocol requires the client to have some minimum quantum ability, while the double-server BQC protocol makes the client's device completely classical, resorting to the pure and clean Bell state shared by two servers. Here, we provide a deterministic entanglement distillation protocol in a practical noisy environment for the double-server BQC protocol. This protocol can get the pure maximally entangled Bell state. The success probability can reach 100% in principle. The distilled maximally entangled states can be remaind to perform the BQC protocol subsequently. The parties who perform the distillation protocol do not need to exchange the classical information and they learn nothing from the client. It makes this protocol unconditionally secure and suitable for the future BQC protocol. PMID:25588565

  1. Computational nuclear quantum many-body problem: The UNEDF project

    SciTech Connect

    Fann, George I

    2013-01-01

    The UNEDF project was a large-scale collaborative effort that applied high-performance computing to the nuclear quantum many-body problem. The primary focus of the project was on constructing, validating, and applying an optimized nuclear energy density functional, which entailed a wide range of pioneering developments in microscopic nuclear structure and reactions, algorithms, high-performance computing, and uncertainty quantification. UNEDF demonstrated that close associations among nuclear physicists, mathematicians, and computer scientists can lead to novel physics outcomes built on algorithmic innovations and computational developments. This review showcases a wide range of UNEDF science results to illustrate this interplay.

  2. Phonons and solid-state qubits for quantum technology

    NASA Astrophysics Data System (ADS)

    Soykal, . O.; Ruskov, Rusko; Tahan, Charles

    2011-03-01

    Phonons in the context of quantum information processing are traditionally negatives. They induce relaxation or decoherence of or between qubit states. Learning to control phonons for positive purposes, both as supporting technology for quantum information processing, and for other quantum devices is of great possible interest. Already, acoustic waves are used as a supporting technology in microelectronics and optoelectronics (e.g. their slow speed can be useful in certain contexts). Here we consider some methods for making phonons useful and describe the physics of such systems in several potential solid-state systems including silicon. Our results may also be of interest to the optomechanics community.

  3. Verifiable Measurement-Only Blind Quantum Computing with Stabilizer Testing

    NASA Astrophysics Data System (ADS)

    Hayashi, Masahito; Morimae, Tomoyuki

    2015-11-01

    We introduce a simple protocol for verifiable measurement-only blind quantum computing. Alice, a client, can perform only single-qubit measurements, whereas Bob, a server, can generate and store entangled many-qubit states. Bob generates copies of a graph state, which is a universal resource state for measurement-based quantum computing, and sends Alice each qubit of them one by one. Alice adaptively measures each qubit according to her program. If Bob is honest, he generates the correct graph state, and, therefore, Alice can obtain the correct computation result. Regarding the security, whatever Bob does, Bob cannot get any information about Alice's computation because of the no-signaling principle. Furthermore, malicious Bob does not necessarily send the copies of the correct graph state, but Alice can check the correctness of Bob's state by directly verifying the stabilizers of some copies.

  4. Are Random Pure States Useful for Quantum Computation?

    NASA Astrophysics Data System (ADS)

    Bremner, Michael J.; Mora, Caterina; Winter, Andreas

    2009-05-01

    We show the following: a randomly chosen pure state as a resource for measurement-based quantum computation iswith overwhelming probabilityof no greater help to a polynomially bounded classical control computer, than a string of random bits. Thus, unlike the familiar cluster states, the computing power of a classical control device is not increased from P to BQP (bounded-error, quantum polynomial time), but only to BPP (bounded-error, probabilistic polynomial time). The same holds if the task is to sample from a distribution rather than to perform a bounded-error computation. Furthermore, we show that our results can be extended to states with significantly less entanglement than random states.

  5. Preparing Malaysian Vocational and Technology Teachers To Integrate Computer Technology in Teaching Vocational and Technology Subjects.

    ERIC Educational Resources Information Center

    Bakar, Ab. Rahim bin; Mohamed, Shamsiah

    1998-01-01

    A Malaysian study investigating the preparedness of vocational and technology teachers to integrate computer technology found that teachers were not knowledgeable about computers or computer software and thought they were not skillful in using spreadsheets, word processing, desktop publishing, database management, and programming software. Most

  6. Bound on quantum computation time: Quantum error correction in a critical environment

    SciTech Connect

    Novais, E.; Mucciolo, Eduardo R.; Baranger, Harold U.

    2010-08-15

    We obtain an upper bound on the time available for quantum computation for a given quantum computer and decohering environment with quantum error correction implemented. First, we derive an explicit quantum evolution operator for the logical qubits and show that it has the same form as that for the physical qubits but with a reduced coupling strength to the environment. Using this evolution operator, we find the trace distance between the real and ideal states of the logical qubits in two cases. For a super-Ohmic bath, the trace distance saturates, while for Ohmic or sub-Ohmic baths, there is a finite time before the trace distance exceeds a value set by the user.

  7. Architecture Framework for Trapped-Ion Quantum Computer based on Performance Simulation Tool

    NASA Astrophysics Data System (ADS)

    Ahsan, Muhammad

    The challenge of building scalable quantum computer lies in striking appropriate balance between designing a reliable system architecture from large number of faulty computational resources and improving the physical quality of system components. The detailed investigation of performance variation with physics of the components and the system architecture requires adequate performance simulation tool. In this thesis we demonstrate a software tool capable of (1) mapping and scheduling the quantum circuit on a realistic quantum hardware architecture with physical resource constraints, (2) evaluating the performance metrics such as the execution time and the success probability of the algorithm execution, and (3) analyzing the constituents of these metrics and visualizing resource utilization to identify system components which crucially define the overall performance. Using this versatile tool, we explore vast design space for modular quantum computer architecture based on trapped ions. We find that while success probability is uniformly determined by the fidelity of physical quantum operation, the execution time is a function of system resources invested at various layers of design hierarchy. At physical level, the number of lasers performing quantum gates, impact the latency of the fault-tolerant circuit blocks execution. When these blocks are used to construct meaningful arithmetic circuit such as quantum adders, the number of ancilla qubits for complicated non-clifford gates and entanglement resources to establish long-distance communication channels, become major performance limiting factors. Next, in order to factorize large integers, these adders are assembled into modular exponentiation circuit comprising bulk of Shor's algorithm. At this stage, the overall scaling of resource-constraint performance with the size of problem, describes the effectiveness of chosen design. By matching the resource investment with the pace of advancement in hardware technology, we find optimal designs for different types of quantum adders. Conclusively, we show that 2,048-bit Shor's algorithm can be reliably executed within the resource budget of 1.5 million qubits.

  8. High threshold distributed quantum computing with three-qubit nodes

    NASA Astrophysics Data System (ADS)

    Li, Ying; Benjamin, Simon C.

    2012-09-01

    In the distributed quantum computing paradigm, well-controlled few-qubit nodes are networked together by connections which are relatively noisy and failure prone. A practical scheme must offer high tolerance to errors while requiring only simple (i.e. few-qubit) nodes. Here we show that relatively modest, three-qubit nodes can support advanced purification techniques and so offer robust scalability: the infidelity in the entanglement channel may be permitted to approach 10% if the infidelity in local operations is of order 0.1%. Our tolerance of network noise is therefore an order of magnitude beyond prior schemes, and our architecture remains robust even in the presence of considerable decoherence rates (memory errors). We compare the performance with that of schemes involving nodes of lower and higher complexity. Ion traps, and NV-centres in diamond, are two highly relevant emerging technologies: they possess the requisite properties of good local control, rapid and reliable readout, and methods for entanglement-at-a-distance.

  9. CALL FOR PAPERS: Optical implementation of quantum computers

    NASA Astrophysics Data System (ADS)

    Rarity, John; Weinfurter, Harald

    2004-09-01

    A topical issue of Journal of Optics B: Quantum and Semiclassical Optics will be devoted to recent advances in optical implementation of quantum computers. The topics to be covered will include, but are not limited to: bullet Linear optics quantum gates bullet Progress towards nonlinear optics quantum gates bullet Interface between optical qubits and atomic/solid state qubits bullet Novel architectures bullet Single-photon sources and detectors bullet Photonic quantum networks bullet Few-qubit applications The DEADLINE for submission of contributions is 15 January 2005 to allow the topical issue to be published in about October 2005. All contributions will be peer-reviewed in accordance with the normal refereeing procedures and standards of Journal of Optics B: Quantum and Semiclassical Optics. Submissions should preferably be in either standard LaTeX form or Microsoft Word. Advice on publishing your work in the journal may be found at www.iop.org/journals/authors/jopb. There are no page charges for publication. The corresponding author of each paper published will receive a complimentary copy of the topical issue. Contributions to the topical issue should preferably be submitted electronically at www.iop.org/journals/authors/jopb or by e-mail to jopb@iop.org. Authors unable to submit online or by e-mail may send hard copy contributions (enclosing the electronic code) to: Dr Claire Bedrock (Publisher), Journal of Optics B: Quantum and Semiclassical Optics, Institute of Physics Publishing, Dirac House, Temple Back, Bristol BS1 6BE, UK. All contributions should be accompanied by a readme file or covering letter, quoting `JOPB Topical Issue - Optical implementation of quantum computers', giving the postal and e-mail addresses for correspondence. Any subsequent change of address should be notified to the publishing office. We look forward to receiving your contribution to this topical issue.

  10. Optical quantum computation with cavities in the intermediate coupling region

    NASA Astrophysics Data System (ADS)

    Mei, F.; Yu, Y. F.; Feng, X. L.; Zhu, S. L.; Zhang, Z. M.

    2010-07-01

    Large-scale quantum computation is currently a hot area of research. The scalable quantum computation scheme with cavities originally proposed by Duan and Kimble (Phys. Rev. Lett., 92 (2004) 127902) is further developed here to operate in the intermediate coupling region, which not only greatly relaxes experimental demands on the Purcell factor, but also eliminates the need to consider internal trade-off between cavity quality and efficiency. In our scheme, by controlling the reflectivity of the input single-photon pulse in the cavity, we can realize local atom-photon and nonlocal atom-atom controlled phase-flip (CPF) gates. We also introduce a theoretical model to analyze the performance of our scheme under practical noise. Furthermore, we show that the nonlocal CPF gate can be used to realize a quantum repeater.

  11. Signal-based classical emulation of a universal quantum computer

    NASA Astrophysics Data System (ADS)

    La Cour, Brian R.; Ott, Granville E.

    2015-05-01

    In this paper we present a novel approach to emulating a universal quantum computer with a classical system, one that uses a signal of bounded duration and amplitude to represent an arbitrary quantum state. The signal may be of any modality (e.g., acoustic, electromagnetic, etc), but we focus our discussion here on electronic signals. Unitary gate operations are performed using analog electronic circuit devices, such as four-quadrant multipliers, operational amplifiers, and analog filters, although non-unitary operations may be performed as well. In this manner, the Hilbert space structure of the quantum state, as well as a universal set of gate operations, may be fully emulated classically. The required bandwidth scales exponentially with the number of qubits, however, thereby limiting the scalability of the approach, but the intrinsic parallelism, ease of construction, and classical robustness to decoherence may nevertheless lead to capabilities and efficiencies rivaling that of current high performance computers.

  12. Reducing the overhead for quantum computation when noise is biased

    NASA Astrophysics Data System (ADS)

    Webster, Paul; Bartlett, Stephen D.; Poulin, David

    2015-12-01

    We analyze a model for fault-tolerant quantum computation with low overhead suitable for situations where the noise is biased. The basis for this scheme is a gadget for the fault-tolerant preparation of magic states that enable universal fault-tolerant quantum computation using only Clifford gates that preserve the noise bias. We analyze the distillation of |T > -type magic states using this gadget at the physical level, followed by concatenation with the 15-qubit quantum Reed-Muller code, and comparing our results with standard constructions. In the regime where the noise bias (rate of Pauli Z errors relative to other single-qubit errors) is greater than a factor of 10, our scheme has lower overhead across a broad range of relevant noise rates.

  13. Indications for quantum computation requirements from comparative brain analysis

    NASA Astrophysics Data System (ADS)

    Bernroider, Gustav; Baer, Wolfgang

    2010-04-01

    Whether or not neuronal signal properties can engage 'non-trivial', i.e. functionally significant, quantum properties, is the subject of an ongoing debate. Here we provide evidence that quantum coherence dynamics can play a functional role in ion conduction mechanism with consequences on the shape and associative character of classical membrane signals. In particular, these new perspectives predict that a specific neuronal topology (e.g. the connectivity pattern of cortical columns in the primate brain) is less important and not really required to explain abilities in perception and sensory-motor integration. Instead, this evidence is suggestive for a decisive role of the number and functional segregation of ion channel proteins that can be engaged in a particular neuronal constellation. We provide evidence from comparative brain studies and estimates of computational capacity behind visual flight functions suggestive for a possible role of quantum computation in biological systems.

  14. Multiqubit Decoherence in Ion-trap Quantum Computation

    NASA Astrophysics Data System (ADS)

    Monz, Thomas; Schindler, Philipp; Barreiro, Julio T.; Chwalla, Michael; Coish, Bill; Hennrich, Markus T.; Blatt, Rainer

    2010-03-01

    We will report on the realisation of high-fidelity Schroedinger- Cat states with more than six qubits in a string of ^40Ca^ + ions stored in a linear ion trap. We achieved fidelities with the target states exceeding 95% for up to four ions and 88% for six ions. These high fidelities allow to investigate decoherence of highly entangled quantum states in the presence of collective dephasing, the predominant source of decoherence in ion-trap based and other physical realizations of quantum computation. Assuming the noise to be Gaussian and stationary, we derive and experimentally confirm a model that predicts an exponential decay of the state fidelity that scales as N^2 where N is the number of qubits. Such a scaling behaviour has severe effects on quantum computation and related fields, such as metrology.

  15. Quantum-Computation for Perceptual Control Architecture

    NASA Astrophysics Data System (ADS)

    Ivancevic, Vladimir G.; Reid, Darryn J.

    2015-11-01

    In this Chapter, we propose a quantum-dynamical modeling approach to Perceptual Control Architecture, using large networks of Josephson Junctions and their category-theoretic generalizations with fuzzy associative functors Our approach provides the basis for composing modular multi-layered perceptual control architectures using Josephson Junction Networks, employing intuitively appealing category-theoretic abstractions to hide the algebraic details from the designer while nonetheless being able to rigorously ensure functional composition correctness. That is, our approach ensures that Josephson Junction Networks, as a modeling primitive, can be composed into formally correct multi-layered perceptual control architectures, while hiding the underlying algebraic systems of equations from the designer under a blanket of category-theoretic abstraction.

  16. Adapting the traveling salesman problem to an adiabatic quantum computer

    NASA Astrophysics Data System (ADS)

    Warren, Richard H.

    2013-04-01

    We show how to guide a quantum computer to select an optimal tour for the traveling salesman. This is significant because it opens a rapid solution method for the wide range of applications of the traveling salesman problem, which include vehicle routing, job sequencing and data clustering.

  17. QNIX: A Linear Optical Architecture for Quantum Computing

    NASA Astrophysics Data System (ADS)

    Gimeno-Segovia, Mercedes; Shadbolt, Peter J.; Rudolph, Terry G.; Browne, Dan E.; Mendoza, Gabriel; Russell, Nicholas J.; Silverstone, Joshua W.; Santamato, Alberto; Carolan, Jacques; O'Brien, Jeremy

    2015-03-01

    There is currently a great deal of effort to develop a large-scale quantum computer, and one of the most promising platforms to do so is integrated linear optics. We present a proposal for a dynamical scheme for an integrated linear optics implementation of a one-way quantum computer. We go beyond the purely theoretical work and address practical issues in order to create a physically realistic design. We describe every step of cluster state construction and processing, showing the outstanding issues left to be addressed and our contributions to the different stages of the dynamical process. These include optimised interferometers for the generation of GHZ states, a universal and scalable architecture which requires entangled sources of no more than 3 photons with no active feed-forward, and loss-tolerant and fault-tolerant strategies specifically tailored to our proposed architecture. Our work demonstrates that building a linear optical quantum computer need be less challenging than previously thought, and brings large-scale switch-free linear optical architectures for quantum computing much closer to experimental realisation.

  18. Implementation scheme of controlled SWAP gates for quantum fingerprinting and photonic quantum computation

    SciTech Connect

    Wang, B.; Duan, L.-M.

    2007-05-15

    We propose a scheme to implement quantum controlled SWAP gates by directing single-photon pulses to a two-sided cavity with a single trapped atom. The resultant gates can be used to realize quantum fingerprinting and universal photonic quantum computation. We present a theoretical model for our scheme and analyze its performance under practical noise, including spontaneous emission and randomness of atom-cavity coupling strength. It is shown that our scheme should be robust against practical imperfections in current cavity QED experiment setup.

  19. Two-Qubit Gate Operation on Selected Nearest Neighboring Qubits in a Neutral Atom Quantum Computer

    NASA Astrophysics Data System (ADS)

    Lapasar, Elham Hosseini; Kasamatsu, Kenichi; Chormaic, Sle Nic; Takui, Takeji; Kondo, Yasushi; Nakahara, Mikio; Ohmi, Tetsuo

    2014-03-01

    Quantum information science has rapidly grown with the promise to build up a quantum computer to solve many classically intractable problems by making use of properties of quantum particles, such as superposition and entanglement. Systems of trapped neutral atoms is one of the promising candidates for implementing a scalable quantum computer, since neutral atoms have an advantage of an intrinsically weaker interaction with the environment. We have discussed a design of a neutral atom quantum computer with a selective two-qubit gate operation. In this contribution, we propose a feasible experiment towards the selective two-qubit gate operation that is less demanding than our original proposal, although the gate operation is limited between neighboring atoms. We evaluate the process of a two-qubit gate operation that is applied on nearest neighboring trapped atoms and estimate the upper bound of the gate operation time and corresponding gate fidelity. This proposal can be demonstrated using current technology, which would be a starting point toward the realization of a fully controlled selective two-qubit gate operation using neutral atoms. Note from Publisher: This article contains only abstract.

  20. Computational and Mathematical Modeling of Coupled Superconducting Quantum Interference Devices

    NASA Astrophysics Data System (ADS)

    Berggren, Susan Anne Elizabeth

    This research focuses on conducting an extensive computational investigation and mathematical analysis into the average voltage response of arrays of Superconducting Quantum Interference Devices (SQUIDs). These arrays will serve as the basis for the development of a sensitive, low noise, significantly lower Size, Weight and Power (SWaP) antenna integrated with Low-Noise Amplifier (LNA) using the SQUID technology. The goal for this antenna is to be capable of meeting all requirements for Guided Missile Destroyers (DDG) 1000 class ships for Information Operations/Signals Intelligence (IO/SIGINT) applications in Very High Frequency/Ultra High Frequency (V/UHF) bands. The device will increase the listening capability of receivers by moving technology into a new regime of energy detection allowing wider band, smaller size, more sensitive, stealthier systems. The smaller size and greater sensitivity will allow for ships to be de-cluttered of their current large dishes and devices, replacing everything with fewer and smaller SQUID antenna devices. The fewer devices present on the deck of a ship, the more invisible the ship will be to enemy forces. We invent new arrays of SQUIDs, optimized for signal detection with very high dynamic range and excellent spur-free dynamic range, while maintaining extreme small size (and low radar cross section), wide bandwidth, and environmentally noise limited sensitivity, effectively shifting the bottle neck of receiver systems forever away from the antenna itself deeper into the receiver chain. To accomplish these goals we develop and validate mathematical models for different designs of SQUID arrays and use them to invent a new device and systems design. This design is capable of significantly exceeding, per size weight and power, state-of-the-art receiver system measures of performance, such as bandwidth, sensitivity, dynamic range, and spurious-free dynamic range.

  1. Technologies for Achieving Field Ubiquitous Computing

    NASA Astrophysics Data System (ADS)

    Nagashima, Akira

    Although the term ubiquitous may sound like jargon used in information appliances, ubiquitous computing is an emerging concept in industrial automation. This paper presents the author's visions of field ubiquitous computing, which is based on the novel Internet Protocol IPv6. IPv6-based instrumentation will realize the next generation manufacturing excellence. This paper focuses on the following five key issues: 1. IPv6 standardization; 2. IPv6 interfaces embedded in field devices; 3. Compatibility with FOUNDATION fieldbus; 4. Network securities for field applications; and 5. Wireless technologies to complement IP instrumentation. Furthermore, the principles of digital plant operations and ubiquitous production to support the above key technologies to achieve field ubiquitous systems are discussed.

  2. Quantum computation mediated by ancillary qudits and spin coherent states

    NASA Astrophysics Data System (ADS)

    Proctor, Timothy J.; Dooley, Shane; Kendon, Viv

    2015-01-01

    Models of universal quantum computation in which the required interactions between register (computational) qubits are mediated by some ancillary system are highly relevant to experimental realizations of a quantum computer. We introduce such a universal model that employs a d -dimensional ancillary qudit. The ancilla-register interactions take the form of controlled displacements operators, with a displacement operator defined on the periodic and discrete lattice phase space of a qudit. We show that these interactions can implement controlled phase gates on the register by utilizing geometric phases that are created when closed loops are traversed in this phase space. The extra degrees of freedom of the ancilla can be harnessed to reduce the number of operations required for certain gate sequences. In particular, we see that the computational advantages of the quantum bus (qubus) architecture, which employs a field-mode ancilla, are also applicable to this model. We then explore an alternative ancilla-mediated model which employs a spin ensemble as the ancillary system and again the interactions with the register qubits are via controlled displacement operators, with a displacement operator defined on the Bloch sphere phase space of the spin coherent states of the ensemble. We discuss the computational advantages of this model and its relationship with the qubus architecture.

  3. Interplay between computable measures of entanglement and other quantum correlations

    SciTech Connect

    Girolami, Davide; Adesso, Gerardo

    2011-11-15

    Composite quantum systems can be in generic states characterized not only by entanglement but also by more general quantum correlations. The interplay between these two signatures of nonclassicality is still not completely understood. In this work we investigate this issue, focusing on computable and observable measures of such correlations: entanglement is quantified by the negativity N, while general quantum correlations are measured by the (normalized) geometric quantum discord D{sub G}. For two-qubit systems, we find that the geometric discord reduces to the squared negativity on pure states, while the relationship D{sub G}{>=}N{sup 2} holds for arbitrary mixed states. The latter result is rigorously extended to pure, Werner, and isotropic states of two-qudit systems for arbitrary d, and numerical evidence of its validity for arbitrary states of a qubit and a qutrit is provided as well. Our results establish an interesting hierarchy, which we conjecture to be universal, between two relevant and experimentally friendly nonclassicality indicators. This ties in with the intuition that general quantum correlations should at least contain and in general exceed entanglement on mixed states of composite quantum systems.

  4. Computational complexity of nonequilibrium steady states of quantum spin chains

    NASA Astrophysics Data System (ADS)

    Marzolino, Ugo; Prosen, Tomaž

    2016-03-01

    We study nonequilibrium steady states (NESS) of spin chains with boundary Markovian dissipation from the computational complexity point of view. We focus on X X chains whose NESS are matrix product operators, i.e., with coefficients of a tensor operator basis described by transition amplitudes in an auxiliary space. Encoding quantum algorithms in the auxiliary space, we show that estimating expectations of operators, being local in the sense that each acts on disjoint sets of few spins covering all the system, provides the answers of problems at least as hard as, and believed by many computer scientists to be much harder than, those solved by quantum computers. We draw conclusions on the hardness of the above estimations.

  5. Optimizing Quantum Simulation for Heterogeneous Computing: a Hadamard Transformation Study

    NASA Astrophysics Data System (ADS)

    de Avila, Anderson B.; Schumalfuss, Murilo F.; Reiser, Renata H. S.; Pilla, Mauricio L.; Maron, Adriano K.

    2015-10-01

    The D-GM execution environment improves distributed simulation of quantum algorithms in heterogeneous computing environments comprising both multi-core CPUs and GPUs. The main contribution of this work consists in the optimization of the environment VirD-GM, conceived in three steps: (i) the theoretical studies and implementation of the abstractions of the Mixed Partial Process defined in the qGM model, focusing on the reduction of the memory consumption regarding multidimensional QTs; (ii) the distributed/parallel implementation of such abstractions allowing its execution on clusters of GPUs; (iii) and optimizations that predict multiplications by zero-value of the quantum states/transformations, implying reduction in the number of computations. The results obtained in this work embrace the distribute/parallel simulation of Hadamard gates up to 21 qubits, showing scalability with the increase in the number of computing nodes.

  6. Reviews of computing technology: Client-server technology

    SciTech Connect

    Johnson, S.M.

    1990-09-01

    One of the most frequently heard terms in the computer industry these days is ``client-server.`` There is much misinformation available on the topic, and competitive pressures on software vendors have led to a great deal of hype with little in the way of supporting products. The purpose of this document is to explain what is meant by client-server applications, why the Advanced Technology and Architecture (ATA) section of the Information Resources Management (IRM) Department sees this emerging technology as key for computer applications during the next ten years, and what ATA sees as the existing standards and products available today. Because of the relative immaturity of existing client-server products, IRM is not yet guidelining any specific client-server products, except those that are components of guidelined data communications products or database management systems.

  7. Reviews of computing technology: Client-server technology

    SciTech Connect

    Johnson, S.M.

    1990-09-01

    One of the most frequently heard terms in the computer industry these days is client-server.'' There is much misinformation available on the topic, and competitive pressures on software vendors have led to a great deal of hype with little in the way of supporting products. The purpose of this document is to explain what is meant by client-server applications, why the Advanced Technology and Architecture (ATA) section of the Information Resources Management (IRM) Department sees this emerging technology as key for computer applications during the next ten years, and what ATA sees as the existing standards and products available today. Because of the relative immaturity of existing client-server products, IRM is not yet guidelining any specific client-server products, except those that are components of guidelined data communications products or database management systems.

  8. Computer Education and Instructional Technology Teacher Trainees' Opinions about Cloud Computing Technology

    ERIC Educational Resources Information Center

    Karamete, Aysen

    2015-01-01

    This study aims to show the present conditions about the usage of cloud computing in the department of Computer Education and Instructional Technology (CEIT) amongst teacher trainees in School of Necatibey Education, Balikesir University, Turkey. In this study, a questionnaire with open-ended questions was used. 17 CEIT teacher trainees…

  9. Computer Education and Instructional Technology Teacher Trainees' Opinions about Cloud Computing Technology

    ERIC Educational Resources Information Center

    Karamete, Aysen

    2015-01-01

    This study aims to show the present conditions about the usage of cloud computing in the department of Computer Education and Instructional Technology (CEIT) amongst teacher trainees in School of Necatibey Education, Balikesir University, Turkey. In this study, a questionnaire with open-ended questions was used. 17 CEIT teacher trainees

  10. All-electrical quantum computation with mobile spin qubits

    NASA Astrophysics Data System (ADS)

    Popescu, A. E.; Ionicioiu, R.

    2004-06-01

    We describe and discuss a solid state proposal for quantum computation with mobile spin qubits in one-dimensional systems, based on recent advances in spintronics. Static electric fields are used to implement a universal set of quantum gates, via the spin-orbit and exchange couplings. Initialization and measurement can be performed either by spin injection from/to ferromagnets, or by using spin filters and mesoscopic spin polarizing beam-splitters. The vulnerability of this proposal to various sources of error is estimated by numerical simulations. We also assess the suitability of various materials currently used in nanotechnology for an actual implementation of our model.

  11. Large nonadiabatic quantum molecular dynamics simulations on parallel computers

    NASA Astrophysics Data System (ADS)

    Shimojo, Fuyuki; Ohmura, Satoshi; Mou, Weiwei; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya

    2013-01-01

    We have implemented a quantum molecular dynamics simulation incorporating nonadiabatic electronic transitions on massively parallel computers to study photoexcitation dynamics of electrons and ions. The nonadiabatic quantum molecular dynamics (NAQMD) simulation is based on Casida's linear response time-dependent density functional theory to describe electronic excited states and Tully's fewest-switches surface hopping approach to describe nonadiabatic electron-ion dynamics. To enable large NAQMD simulations, a series of techniques are employed for efficiently calculating long-range exact exchange correction and excited-state forces. The simulation program is parallelized using hybrid spatial and band decomposition, and is tested for various materials.

  12. Reviews of computing technology: Object-oriented technology

    SciTech Connect

    Skeen, D.C.

    1993-03-01

    A useful metaphor in introducing object-oriented concepts is the idea of a computer hardware manufacturer assembling products from an existing stock of electronic parts. In this analogy, think of the parts as pieces of computer software and of the finished products as computer applications. Like its counterpart, the object is capable of performing its specific function in a wide variety of different applications. The advantages to assembling hardware using a set of prebuilt parts are obvious. The design process is greatly simplified in this scenario, since the designer needs only to carry the design down to the chip level, rather than to the transistor level. As a result, the designer is free to develop a more reliable and feature rich product. Also, since the component parts are reused in several different products, the parts can be made more robust and subjected to more rigorous testing than would be economically feasible for a part used in only one piece of equipment. Additionally, maintenance on the resulting systems is simplified because of the part-level consistency from one type of equipment to another. The remainder of this document introduces the techniques used to develop objects, the benefits of the technology, outstanding issues that remain with the technology, industry direction for the technology, and the impact that object-oriented technology is likely to have on the organization. While going through this material, the reader will find it useful to remember the parts analogy and to keep in mind that the overall purpose of object-oriented technology is to create software parts and to construct applications using those parts.

  13. Grid computing technology for hydrological applications

    NASA Astrophysics Data System (ADS)

    Lecca, G.; Petitdidier, M.; Hluchy, L.; Ivanovic, M.; Kussul, N.; Ray, N.; Thieron, V.

    2011-06-01

    SummaryAdvances in e-Infrastructure promise to revolutionize sensing systems and the way in which data are collected and assimilated, and complex water systems are simulated and visualized. According to the EU Infrastructure 2010 work-programme, data and compute infrastructures and their underlying technologies, either oriented to tackle scientific challenges or complex problem solving in engineering, are expected to converge together into the so-called knowledge infrastructures, leading to a more effective research, education and innovation in the next decade and beyond. Grid technology is recognized as a fundamental component of e-Infrastructures. Nevertheless, this emerging paradigm highlights several topics, including data management, algorithm optimization, security, performance (speed, throughput, bandwidth, etc.), and scientific cooperation and collaboration issues that require further examination to fully exploit it and to better inform future research policies. The paper illustrates the results of six different surface and subsurface hydrology applications that have been deployed on the Grid. All the applications aim to answer to strong requirements from the Civil Society at large, relatively to natural and anthropogenic risks. Grid technology has been successfully tested to improve flood prediction, groundwater resources management and Black Sea hydrological survey, by providing large computing resources. It is also shown that Grid technology facilitates e-cooperation among partners by means of services for authentication and authorization, seamless access to distributed data sources, data protection and access right, and standardization.

  14. Computational Support for Technology- Investment Decisions

    NASA Technical Reports Server (NTRS)

    Adumitroaie, Virgil; Hua, Hook; Lincoln, William; Block, Gary; Mrozinski, Joseph; Shelton, Kacie; Weisbin, Charles; Elfes, Alberto; Smith, Jeffrey

    2007-01-01

    Strategic Assessment of Risk and Technology (START) is a user-friendly computer program that assists human managers in making decisions regarding research-and-development investment portfolios in the presence of uncertainties and of non-technological constraints that include budgetary and time limits, restrictions related to infrastructure, and programmatic and institutional priorities. START facilitates quantitative analysis of technologies, capabilities, missions, scenarios and programs, and thereby enables the selection and scheduling of value-optimal development efforts. START incorporates features that, variously, perform or support a unique combination of functions, most of which are not systematically performed or supported by prior decision- support software. These functions include the following: Optimal portfolio selection using an expected-utility-based assessment of capabilities and technologies; Temporal investment recommendations; Distinctions between enhancing and enabling capabilities; Analysis of partial funding for enhancing capabilities; and Sensitivity and uncertainty analysis. START can run on almost any computing hardware, within Linux and related operating systems that include Mac OS X versions 10.3 and later, and can run in Windows under the Cygwin environment. START can be distributed in binary code form. START calls, as external libraries, several open-source software packages. Output is in Excel (.xls) file format.

  15. Quantum and classical parallelism in parity algorithms for ensemble quantum computers

    SciTech Connect

    Stadelhofer, Ralf; Suter, Dieter; Banzhaf, Wolfgang

    2005-03-01

    The determination of the parity of a string of N binary digits is a well-known problem in classical as well as quantum information processing, which can be formulated as an oracle problem. It has been established that quantum algorithms require at least N/2 oracle calls. We present an algorithm that reaches this lower bound and is also optimal in terms of additional gate operations required. We discuss its application to pure and mixed states. Since it can be applied directly to thermal states, it does not suffer from signal loss associated with pseudo-pure-state preparation. For ensemble quantum computers, the number of oracle calls can be further reduced by a factor 2{sup k}, with k is a member of {l_brace}{l_brace}1,2,...,log{sub 2}(N/2{r_brace}{r_brace}, provided the signal-to-noise ratio is sufficiently high. This additional speed-up is linked to (classical) parallelism of the ensemble quantum computer. Experimental realizations are demonstrated on a liquid-state NMR quantum computer.

  16. Los Alamos Quantum Dots for Solar, Display Technology

    SciTech Connect

    Klimov, Victor

    2015-04-13

    Quantum dots are ultra-small bits of semiconductor matter that can be synthesized with nearly atomic precision via modern methods of colloidal chemistry. Their emission color can be tuned by simply varying their dimensions. Color tunability is combined with high emission efficiencies approaching 100 percent. These properties have recently become the basis of a new technologyquantum dot displays – employed, for example, in the newest generation of e-readers and video monitors.

  17. Adaptive quantum computation in changing environments using projective simulation

    NASA Astrophysics Data System (ADS)

    Tiersch, M.; Ganahl, E. J.; Briegel, H. J.

    2015-08-01

    Quantum information processing devices need to be robust and stable against external noise and internal imperfections to ensure correct operation. In a setting of measurement-based quantum computation, we explore how an intelligent agent endowed with a projective simulator can act as controller to adapt measurement directions to an external stray field of unknown magnitude in a fixed direction. We assess the agent’s learning behavior in static and time-varying fields and explore composition strategies in the projective simulator to improve the agent’s performance. We demonstrate the applicability by correcting for stray fields in a measurement-based algorithm for Grover’s search. Thereby, we lay out a path for adaptive controllers based on intelligent agents for quantum information tasks.

  18. Semiconductor-inspired design principles for superconducting quantum computing.

    PubMed

    Shim, Yun-Pil; Tahan, Charles

    2016-01-01

    Superconducting circuits offer tremendous design flexibility in the quantum regime culminating most recently in the demonstration of few qubit systems supposedly approaching the threshold for fault-tolerant quantum information processing. Competition in the solid-state comes from semiconductor qubits, where nature has bestowed some very useful properties which can be utilized for spin qubit-based quantum computing. Here we begin to explore how selective design principles deduced from spin-based systems could be used to advance superconducting qubit science. We take an initial step along this path proposing an encoded qubit approach realizable with state-of-the-art tunable Josephson junction qubits. Our results show that this design philosophy holds promise, enables microwave-free control, and offers a pathway to future qubit designs with new capabilities such as with higher fidelity or, perhaps, operation at higher temperature. The approach is also especially suited to qubits on the basis of variable super-semi junctions. PMID:26983379

  19. Complex duality quantum computers acting on pure and mixed states

    NASA Astrophysics Data System (ADS)

    Cao, HuaiXin; Chen, ZhengLi; Guo, ZhiHua; Ren, FangGuo

    2012-12-01

    The aim of this paper is to establish a mathematical fundamental of complex duality quantum computers (CDQCs) acting on vector-states (pure states) and operator-states (mixed states), respectively. A CDQC consists of a complex divider, a group of quantum gates represented by unitary operators, or quantum operations represented by completely positive and trace-preserving mappings, and a complex combiner. It is proved that the divider and the combiner of a CDQC are an isometry and a contraction, respectively. It is proved that the divider and the combiner of a CDQC acting on vector-states are dual, and in the finite dimensional case, it is proved that the divider and the combiner of a CDQC acting on operator-states (matrix-states) are also dual. Lastly, the loss of an input state passing through a CDQC is measured.

  20. Is the brain a Clifford algebra quantum computer?

    NASA Astrophysics Data System (ADS)

    Labunets, Valeri G.; Labunets-Rundblad, Ekaterina V.; Astola, Jaakko T.

    2001-11-01

    We propose a novel method to calculate invariants of colour and multicolour images. It employs an idea of classical and quantum hypercomplex numbers and combines it with the idea of classical and quantum number theoretical transforms over hypercomplex algebras, which reduce the computational complexity of the global recognition algorithm for nD k-multispectral images from O(knNn+1)to O(kNn log N) and to O(kn log N), respectively. Our hypotheses are 1) the brain of primates calculates hypercomplex-valued invariants of an image during recognizing, 2) visual systems of animals with different evolutionary history use different hypercomplex algebras. The main goal of the paper is to show that quantum Clifford algebras can be used to solve pattern recognition in multispectral environment in a natural and effective manner.

  1. Semiconductor-inspired design principles for superconducting quantum computing

    PubMed Central

    Shim, Yun-Pil; Tahan, Charles

    2016-01-01

    Superconducting circuits offer tremendous design flexibility in the quantum regime culminating most recently in the demonstration of few qubit systems supposedly approaching the threshold for fault-tolerant quantum information processing. Competition in the solid-state comes from semiconductor qubits, where nature has bestowed some very useful properties which can be utilized for spin qubit-based quantum computing. Here we begin to explore how selective design principles deduced from spin-based systems could be used to advance superconducting qubit science. We take an initial step along this path proposing an encoded qubit approach realizable with state-of-the-art tunable Josephson junction qubits. Our results show that this design philosophy holds promise, enables microwave-free control, and offers a pathway to future qubit designs with new capabilities such as with higher fidelity or, perhaps, operation at higher temperature. The approach is also especially suited to qubits on the basis of variable super-semi junctions. PMID:26983379

  2. Adaptive quantum computation in changing environments using projective simulation

    PubMed Central

    Tiersch, M.; Ganahl, E. J.; Briegel, H. J.

    2015-01-01

    Quantum information processing devices need to be robust and stable against external noise and internal imperfections to ensure correct operation. In a setting of measurement-based quantum computation, we explore how an intelligent agent endowed with a projective simulator can act as controller to adapt measurement directions to an external stray field of unknown magnitude in a fixed direction. We assess the agent’s learning behavior in static and time-varying fields and explore composition strategies in the projective simulator to improve the agent’s performance. We demonstrate the applicability by correcting for stray fields in a measurement-based algorithm for Grover’s search. Thereby, we lay out a path for adaptive controllers based on intelligent agents for quantum information tasks. PMID:26260263

  3. Scheduling error correction operations for a quantum computer.

    SciTech Connect

    Landahl, Andrew J.; Carr, Robert D.; Phillips, Cynthia Ann; Ganti, Anand

    2010-09-01

    In a (future) quantum computer a single logical quantum bit (qubit) will be made of multiple physical qubits. These extra physical qubits implement mandatory extensive error checking. The efficiency of error correction will fundamentally influence the performance of a future quantum computer, both in latency/speed and in error threshold (the worst error tolerated for an individual gate). Executing this quantum error correction requires scheduling the individual operations subject to architectural constraints. Since our last talk on this subject, a team of researchers at Sandia National Labortories has designed a logical qubit architecture that considers all relevant architectural issues including layout, the effects of supporting classical electronics, and the types of gates that the underlying physical qubit implementation supports most naturally. This is a two-dimensional system where 2-qubit operations occur locally, so there is no need to calculate more complex qubit/information transportation. Using integer programming, we found a schedule of qubit operations that obeys the hardware constraints, implements the local-check code in the native gate set, and minimizes qubit idle periods. Even with an optimal schedule, however, parallel Monte Carlo simulation shows that there is no finite error probability for the native gates such that the error-correction system would be benecial. However, by adding dynamic decoupling, a series of timed pulses that can reverse some errors, we found that there may be a threshold. Thus finding optimal schedules for increasingly-refined scheduling problems has proven critical for the overall design of the logical qubit system. We describe the evolving scheduling problems and the ideas behind the integer programming-based solution methods. This talk assumes no prior knowledge of quantum computing.

  4. Mixed Species Ion Chains for Scalable Quantum Computation

    NASA Astrophysics Data System (ADS)

    Wright, John Albert

    Mixed species chains of barium and ytterbium ions are investigated as a tool for building scalable quantum computation devices. Ytterbium ions provide a stable, environmentally-insensitive qubit that is easily initialized and manipulated, while barium ions are easily entangled with photons that can allow quantum information to be transmitted between systems in modular quantum computation units. Barium and ytterbium are trapped together in a linear chain in a linear rf trap and their normal mode structure and the thermal occupation numbers of these modes are measured with a narrow band laser addressing an electric quadrupole transition in barium ions. Before these measurements, barium ions are directly cooled using Doppler cooling, while the ytterbium ions are sympathetically cooled by the barium. For radial modes strongly coupled to ytterbium ions the average thermal occupation numbers vary between 400 and 12,000 depending on ion species configuration and trap parameters. Ion chain temperatures are also measured using a technique based on ion species reordering. Surface traps with many dc electrodes provide the ability to controllably reorder the chain to optimize normal mode cooling, and initial work towards realizing this capability are discussed. Quantum information can be transferred between ions in a linear chain using an optical system that is well coupled to the motional degrees of freedom of the chain. For this reason, a 532 nm Raman system is developed and its expected performance is evaluated.

  5. On computational power of classical and quantum branching programs

    NASA Astrophysics Data System (ADS)

    Ablayev, Farid

    2006-05-01

    We present a classical stochastic simulation technique of quantum Branching programs. This technique allows to prove the following relations among complexity classes: PrQP-BP \\subuline PP-BP and BQP-BP \\subuline PP-BP. Here BPP-BP and PP-BP stands for the classes of functions computable with bounded error and unbounded error respectively by stochastic branching program of polynomial size. BQP-BP and PrQP-BP stands the classes of functions computable with bounded error and unbounded error respectively by quantum branching program of polynomial size. Second. We present two different types, of complexity lower bounds for quantum nonuniform automata (OBDDs). We call them "metric" and "entropic" lower bounds in according to proof technique used. We present explicit Boolean functions that show that these lower bounds are tight enough. We show that when considering "almost all Boolean functions" on n variables our entropic lower bounds gives exponential (2 c(?)(n-log n) ) lower bound for the width of quantum OBDDs depending on the error ? allowed.

  6. Phonon-based scalable quantum computing and sensing (Presentation Video)

    NASA Astrophysics Data System (ADS)

    El-Kady, Ihab

    2015-04-01

    Quantum computing fundamentally depends on the ability to concurrently entangle and individually address/control a large number of qubits. In general, the primary inhibitors of large scale entanglement are qubit dependent; for example inhomogeneity in quantum dots, spectral crowding brought about by proximity-based entanglement in ions, weak interactions of neutral atoms, and the fabrication tolerances in the case of Si-vacancies or SQUIDs. We propose an inherently scalable solid-state qubit system with individually addressable qubits based on the coupling of a phonon with an acceptor impurity in a high-Q Phononic Crystal resonant cavity. Due to their unique nonlinear properties, phonons enable new opportunities for quantum devices and physics. We present a phononic crystal-based platform for observing the phonon analogy of cavity quantum electrodynamics, called phonodynamics, in a solid-state system. Practical schemes involve selective placement of a single acceptor atom in the peak of the strain field in a high-Q phononic crystal cavity that enables strong coupling of the phonon modes to the energy levels of the atom. A qubit is then created by entangling a phonon at the resonance frequency of the cavity with the atomic acceptor states. We show theoretical optimization of the cavity design and excitation waveguides, along with estimated performance figures of the phoniton system. Qubits based on this half-sound, half-matter quasi-particle, may outcompete other quantum architectures in terms of combined emission rate, coherence lifetime, and fabrication demands.

  7. Computational approach to quantum encoder design for purity optimization

    SciTech Connect

    Yamamoto, Naoki; Fazel, Maryam

    2007-07-15

    In this paper, we address the problem of designing a quantum encoder that maximizes the minimum output purity of a given decohering channel, where the minimum is taken over all possible pure inputs. This problem is cast as a max-min optimization problem with a rank constraint on an appropriately defined matrix variable. The problem is computationally very hard because it is nonconvex with respect to both the objective function (output purity) and the rank constraint. Despite this difficulty, we provide a tractable computational algorithm that produces the exact optimal solution for codespace of dimension 2. Moreover, this algorithm is easily extended to cover the general class of codespaces, in which case the solution is suboptimal in the sense that the suboptimized output purity serves as a lower bound of the exact optimal purity. The algorithm consists of a sequence of semidefinite programmings and can be performed easily. Two typical quantum error channels are investigated to illustrate the effectiveness of our method.

  8. Quantum Computation under Micromotion in a Planar Ion Crystal

    NASA Astrophysics Data System (ADS)

    Wang, Sheng-Tao; Shen, Chao; Duan, Luming

    2015-05-01

    We propose a scheme to realize scalable quantum computation in a planar ion crystal confined by a Paul trap. We show that the inevitable in-plane micromotion affects the gate design via three separate effects: renormalization of the equilibrium positions, coupling to the transverse motional modes, and amplitude modulation in the addressing beam. We demonstrate that all of these effects can be taken into account and high-fidelity gates are possible in the presence of micromotion. This proposal opens the prospect to realize large-scale fault-tolerant quantum computation within a single Paul trap. We would like to thank T. Choi and Z.-X. Gong for useful discussions. This work was supported by the NBRPC (973 Program) No. 2011CBA00300 (No. 2011CBA00302), the IARPA MUSIQC program, the ARO, and the AFOSR MURI program.

  9. A fault-tolerant one-way quantum computer

    SciTech Connect

    Raussendorf, R. . E-mail: rraussendorf@perimeterinstitute.ca; Harrington, J.; Goyal, K.

    2006-09-15

    We describe a fault-tolerant one-way quantum computer on cluster states in three dimensions. The presented scheme uses methods of topological error correction resulting from a link between cluster states and surface codes. The error threshold is 1.4% for local depolarizing error and 0.11% for each source in an error model with preparation-, gate-, storage-, and measurement errors.

  10. Two-dimensional color-code quantum computation

    SciTech Connect

    Fowler, Austin G.

    2011-04-15

    We describe in detail how to perform universal fault-tolerant quantum computation on a two-dimensional color code, making use of only nearest neighbor interactions. Three defects (holes) in the code are used to represent logical qubits. Triple-defect logical qubits are deformed into isolated triangular sections of color code to enable transversal implementation of all single logical qubit Clifford group gates. Controlled-NOT (CNOT) is implemented between pairs of triple-defect logical qubits via braiding.

  11. SYMBMAT: Symbolic computation of quantum transition matrix elements

    NASA Astrophysics Data System (ADS)

    Ciappina, M. F.; Kirchner, T.

    2012-08-01

    We have developed a set of Mathematica notebooks to compute symbolically quantum transition matrices relevant for atomic ionization processes. The utilization of a symbolic language allows us to obtain analytical expressions for the transition matrix elements required in charged-particle and laser induced ionization of atoms. Additionally, by using a few simple commands, it is possible to export these symbolic expressions to standard programming languages, such as Fortran or C, for the subsequent computation of differential cross sections or other observables. One of the main drawbacks in the calculation of transition matrices is the tedious algebraic work required when initial states other than the simple hydrogenic 1s state need to be considered. Using these notebooks the work is dramatically reduced and it is possible to generate exact expressions for a large set of bound states. We present explicit examples of atomic collisions (in First Born Approximation and Distorted Wave Theory) and laser-matter interactions (within the Dipole and Strong Field Approximations and different gauges) using both hydrogenic wavefunctions and Slater-Type Orbitals with arbitrary nlm quantum numbers as initial states. Catalogue identifier: AEMI_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEMI_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC license, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 71 628 No. of bytes in distributed program, including test data, etc.: 444 195 Distribution format: tar.gz Programming language: Mathematica Computer: Single machines using Linux or Windows (with cores with any clock speed, cache memory and bits in a word) Operating system: Any OS that supports Mathematica. The notebooks have been tested under Windows and Linux and with versions 6.x, 7.x and 8.x Classification: 2.6 Nature of problem: The notebooks generate analytical expressions for quantum transition matrix elements required in diverse atomic processes: ionization by ion, electron, or photon impact and ionization within the framework of strong field physics. In charged-particle collisions approaches based on perturbation theory enjoy widespread utilization. Accordingly, we have chosen the First Born Approximation and Distorted Wave theories as examples. In light-matter interactions, the main ingredient for many types of calculations is the dipole transition matrix in its different formulations, i.e. length, velocity, and acceleration gauges. In all these cases the transitions of interest occur between a bound state and a continuum state which can be described in different ways. With the notebooks developed in the present work it is possible to calculate transition matrix elements analytically for any set of quantum numbers nlm of initial hydrogenic states or Slater-Type Orbitals and for plane waves or Coulomb waves as final continuum states. Solution method: The notebooks employ symbolic computation to generate analytical expressions for transition matrix elements used in both collision and light-matter interaction physics. fba_hyd.nb - This notebook computes analytical expressions for the transition matrix of collision-induced ionization in the First Born Approximation (FBA). The transitions considered are from a bound hydrogenic state with arbitrary quantum numbers nlm to a continuum state represented by a plane wave (PW) or a Coulomb wave (CW). distorted_hyd.nb - This notebook computes analytical expressions for the transition matrix of collision-induced ionization in Distorted Wave (DW) theories. The transitions considered are from a (distorted) bound hydrogenic state with arbitrary quantum numbers nlm to a distorted-wave continuum state. The computations are based on scalar and vectorial integrals (see the text for details). dipoleLength_hyd.nb - This notebook computes analytical expressions for the dipole transition matrix in length gauge. The transitions considered are from a bound hydrogenic state with arbitrary quantum numbers nlm to a continuum state represented by a PW (the Strong Field Approximation (SFA)) or a CW (the Coulomb-Volkov Approximation (CVA)). dipoleVelocity_hyd.nb - This notebook computes analytical expressions for the dipole transition matrix in velocity gauge. The transitions considered are from a bound hydrogenic state with arbitrary quantum numbers nlm to a continuum state represented by a PW (the SFA) or a CW (the CVA). dipoleAcceleration_hyd.nb - This notebook computes analytical expressions for the dipole transition matrix in acceleration gauge. The transitions considered are from a bound hydrogenic state with arbitrary quantum numbers nlm to a continuum state represented by a PW (the SFA). For the case of the CVA we only include the transition from the 1s state to a continuum state represented by a CW. fba_STO.nb - This notebook computes analytical expressions for the transition matrix of collision-induced ionization in the FBA. The transitions considered are from a Slater-Type Orbital (STO) with arbitrary quantum numbers nlm to a continuum state represented by a PW or a CW. distorted_STO.nb - This notebook computes analytical expressions for the transition matrix of collision-induced ionization in DW theories. The transitions considered are from a (distorted) STO with arbitrary quantum numbers nlm to a distorted-wave continuum state. The computations are based on scalar and vectorial integrals (see the text for details). dipoleLength_STO.nb - This notebook computes analytical expressions for the dipole transition matrix in length gauge. The transitions considered are from an STO with arbitrary quantum numbers nlm to a continuum state represented by a PW (the SFA) or a CW (the CVA). dipoleVelocity_STO.nb - This notebook computes analytical expressions for the dipole transition matrix in velocity gauge. The transitions considered are from an STO with arbitrary quantum numbers nlm to a continuum state represented by a PW (the SFA) or a CW (the CVA). dipoleAcceleration_STO.nb - This notebook computes analytical expressions for the dipole transition matrix in acceleration gauge. The transitions considered are from an STO with arbitrary quantum numbers nlm to a continuum state represented by a PW (the SFA). The symbolic expressions obtained within each notebook can be exported to standard programming languages such as Fortran or C using the Format.m package (see the text and Ref. Sofroniou (1993) [16] for details). Running time: Computational times vary according to the transition matrix selected and quantum numbers nlm of the initial state used. The typical running time is several minutes, but it will take longer for large values of nlm.

  12. Fault-tolerant holonomic quantum computation in surface codes

    NASA Astrophysics Data System (ADS)

    Zheng, Yi-Cong; Brun, Todd A.

    2015-02-01

    We show that universal holonomic quantum computation can be achieved fault tolerantly by adiabatically deforming the gapped stabilizer Hamiltonian of the surface code, where quantum information is encoded in the degenerate ground space of the system Hamiltonian. We explicitly propose procedures to perform each logical operation, including logical state initialization, logical state measurement, logical controlled-not (cnot), state injection, distillation, etc. In particular, adiabatic braiding of different types of holes on the surface leads to a topologically protected, non-Abelian geometric logical cnot. Throughout the computation, quantum information is protected from both small perturbations and low-weight thermal excitations by a constant energy gap and is independent of the system size. Also, the Hamiltonian terms have weight at most four during the whole process. The effect of thermal error propagation is considered during the adiabatic code deformation. With the help of active error correction, this scheme is fault tolerant, in the sense that the computation time can be arbitrarily long for large-enough lattice size. It is shown that the frequency of error correction and the physical resources needed can be greatly reduced by the constant energy gap.

  13. Numerical simulation of NQR/NMR: Applications in quantum computing.

    PubMed

    Possa, Denimar; Gaudio, Anderson C; Freitas, Jair C C

    2011-04-01

    A numerical simulation program able to simulate nuclear quadrupole resonance (NQR) as well as nuclear magnetic resonance (NMR) experiments is presented, written using the Mathematica package, aiming especially applications in quantum computing. The program makes use of the interaction picture to compute the effect of the relevant nuclear spin interactions, without any assumption about the relative size of each interaction. This makes the program flexible and versatile, being useful in a wide range of experimental situations, going from NQR (at zero or under small applied magnetic field) to high-field NMR experiments. Some conditions specifically required for quantum computing applications are implemented in the program, such as the possibility of use of elliptically polarized radiofrequency and the inclusion of first- and second-order terms in the average Hamiltonian expansion. A number of examples dealing with simple NQR and quadrupole-perturbed NMR experiments are presented, along with the proposal of experiments to create quantum pseudopure states and logic gates using NQR. The program and the various application examples are freely available through the link http://www.profanderson.net/files/nmr_nqr.php. PMID:21324720

  14. Improving student retention in computer engineering technology

    NASA Astrophysics Data System (ADS)

    Pierozinski, Russell Ivan

    The purpose of this research project was to improve student retention in the Computer Engineering Technology program at the Northern Alberta Institute of Technology by reducing the number of dropouts and increasing the graduation rate. This action research project utilized a mixed methods approach of a survey and face-to-face interviews. The participants were male and female, with a large majority ranging from 18 to 21 years of age. The research found that participants recognized their skills and capability, but their capacity to remain in the program was dependent on understanding and meeting the demanding pace and rigour of the program. The participants recognized that curriculum delivery along with instructor-student interaction had an impact on student retention. To be successful in the program, students required support in four domains: academic, learning management, career, and social.

  15. Gaussian quantum computation with oracle-decision problems

    NASA Astrophysics Data System (ADS)

    Adcock, Mark R. A.; Høyer, Peter; Sanders, Barry C.

    2013-04-01

    We study a simple-harmonic-oscillator quantum computer solving oracle decision problems. We show that such computers can perform better by using nonorthogonal Gaussian wave functions rather than orthogonal top-hat wave functions as input to the information encoding process. Using the Deutsch-Jozsa problem as an example, we demonstrate that Gaussian modulation with optimized width parameter results in a lower error rate than for the top-hat encoding. We conclude that Gaussian modulation can allow for an improved trade-off between encoding, processing and measurement of the information.

  16. Wigner Function Negativity and Contextuality in Quantum Computation on Rebits

    NASA Astrophysics Data System (ADS)

    Delfosse, Nicolas; Allard Guerin, Philippe; Bian, Jacob; Raussendorf, Robert

    2015-04-01

    We describe a universal scheme of quantum computation by state injection on rebits (states with real density matrices). For this scheme, we establish contextuality and Wigner function negativity as computational resources, extending results of M. Howard et al. [Nature (London) 510, 351 (2014), 10.1038/nature13460] to two-level systems. For this purpose, we define a Wigner function suited to systems of n rebits and prove a corresponding discrete Hudson's theorem. We introduce contextuality witnesses for rebit states and discuss the compatibility of our result with state-independent contextuality.

  17. Cluster-state quantum computing in optical fibers

    NASA Astrophysics Data System (ADS)

    Soudagar, Yasaman; Bussires, Flix; Berln, Guido; Lacroix, Suzanne; Fernandez, Jos M.; Godbout, Nicolas

    2007-02-01

    A scheme for the implementation of the cluster-state model of quantum computing in optical fibers, which enables the feed-forward feature, is proposed. This scheme uses the time-bin encoding of qubits. Following previously suggested methods of applying arbitrary one-qubit gates in optical fibers, two different ways for the realization of fusion gate types I and II for cluster production are proposed: a fully time-bin-based encoding scheme and a combination of time-bin and polarization-based encoding. Also, the methods of measurement in any desired bases for the purpose of processing of cluster-state computing for both these encodings are explained.

  18. Scalable quantum computation architecture using always-on Ising interactions via quantum feedforward

    NASA Astrophysics Data System (ADS)

    Satoh, Takahiko; Matsuzaki, Yuichiro; Kakuyanagi, Kosuke; Munro, William J.; Semba, Koichi; Yamaguchi, Hiroshi; Saito, Shiro

    2015-05-01

    Here, we propose a way to control the interaction between qubits with always-on Ising interaction. Unlike the standard method to change the interaction strength with unitary operations, we fully make use of nonunitary properties of projective measurements so that we can effectively turn the interaction on or off via feedforward. Our scheme is useful for generating two- or three-dimensional cluster states that are universal resources for fault-tolerant quantum computation with this scheme, and it provides an alternative way to realize a scalable quantum processor.

  19. Spinor with spatial extension and quantum computer feasibility

    NASA Astrophysics Data System (ADS)

    Gondran, Michel; Gondran, Alexandre

    2012-06-01

    In quantum information, the qubit is not represented by a full spinor in space and in time as the z spinor below: ?0(z) = (2??02)-1/2e-z2/4?02(cos?0/2e-i?0/2sin?0/2ei?0/2) but by a simplified spinor without spatial extension ? = (cos?0/2e-i?0/2sin?0/2ei?0/2) This simplification is the basis of our first criticism of the quantum computer concept. Indeed, the demonstrations explaining the interest of the Deutsch, Glover and Shor algorithms are based on calculations using the factorization of entangled qubits. These factorizations are accurate for spinors without spatial extensions, but only approximate for real spinors with spatial extensions. Through the spatial extension question, we also revisit the Stern and Gerlach experiment, to explain the decoherence, the individual impacts and the quantization. We conclude in two other criticism what this spin interpretation implies for the feasibility of quantum computers. A second, more fundamental criticism concerns the existence of the (single) spin-based qubit itself. Indeed, we show that the variables of space and spin are not factorizable duringmeasurement. It seems that the qubit, which is a simplified spinor, does not exist as individual object, at least during the measurement. A third criticism deals with the completness of quantum mechanics. Our analysis explains very simply the negative results of the NMR technique, developed by Chuang et al, which does not use quantum objects individually. The spinor spatial extension takes into account the initial position z0 of the particle.

  20. Robustness and performance scaling of a quantum computer with respect to a class of static defects

    NASA Astrophysics Data System (ADS)

    Nam, Y. S.; Blmel, R.

    2013-12-01

    Competing computationally with experimental groups for the construction of scaling quantum computers, we simulate a complete quantum-gate by quantum-gate implementation of Shor's algorithm on a classical 128-core cluster computer. The resulting virtual quantum computer serves as a convenient quantum laboratory for the investigation of the effect of defects in the quantum circuitry. The class of defects studied here is the removal of all rotation gates with rotation angles ?quantum computer still operates with acceptable performance (success probability of factoring) down to b=2. This is surprising since the deletion of rotation gates results in large errors in the arithmetic circuitry of the quantum computer. Extrapolating on the basis of these results we conclude that for quantum computers of practical interest more than 99% of rotation gates may be discarded with acceptable consequences in quantum computer performance. This result may be of interest to experimental physicists and quantum engineers currently embarked on designing efficient circuitry for scaling quantum computers.

  1. Practical aspects of security certification for commercial quantum technologies

    NASA Astrophysics Data System (ADS)

    Walenta, Nino; Soucarros, Mathilde; Stucki, Damien; Caselunghe, Dario; Domergue, Mathias; Hagerman, Michael; Hart, Randall; Hayford, Don; Houlmann, Raphaël.; Legré, Matthieu; McCandlish, Todd; Page, Jean-Benoît; Tourville, Maurice; Wolterman, Richard

    2015-10-01

    Quantum random number generation (QRNG) and quantum key distribution (QKD) are the first applications of quantum physics at the level of individual quanta that have matured into commercial products. Both have been commercially available for over 10 years and increasingly adopted in information security systems. Current efforts focus on standardization and certification of QRNG and QKD devices and their components in order to validate the technology and enable more widespread adoption. Since no official certification scheme specific to quantum devices has been devised so far, alternative options must be investigated. This paper describes our approaches and efforts to enable compliance of commercial QRNG and QKD network devices with security standards such as AIS 20/311 and FIPS 140-2.2

  2. Teaching with Technology: The Classroom Manager. Cost-Conscious Computing.

    ERIC Educational Resources Information Center

    Smith, Rhea; And Others

    1992-01-01

    Teachers discuss how to make the most of technology in the classroom during a tight economy. Ideas include recycling computer printer ribbons, buying replacement batteries for computer power supply packs, upgrading via software, and soliciting donated computer equipment. (SM)

  3. Evaluating Computer Technology Integration in a Centralized School System

    ERIC Educational Resources Information Center

    Eteokleous, N.

    2008-01-01

    The study evaluated the current situation in Cyprus elementary classrooms regarding computer technology integration in an attempt to identify ways of expanding teachers' and students' experiences with computer technology. It examined how Cypriot elementary teachers use computers, and the factors that influence computer integration in their

  4. Evaluating Computer Technology Integration in a Centralized School System

    ERIC Educational Resources Information Center

    Eteokleous, N.

    2008-01-01

    The study evaluated the current situation in Cyprus elementary classrooms regarding computer technology integration in an attempt to identify ways of expanding teachers' and students' experiences with computer technology. It examined how Cypriot elementary teachers use computers, and the factors that influence computer integration in their…

  5. Quantum computation in brain microtubules: Decoherence and biological feasibility

    NASA Astrophysics Data System (ADS)

    Hagan, S.; Hameroff, S. R.; Tuszyński, J. A.

    2002-06-01

    The Penrose-Hameroff orchestrated objective reduction (orch. OR) model assigns a cognitive role to quantum computations in microtubules within the neurons of the brain. Despite an apparently ``warm, wet, and noisy'' intracellular milieu, the proposal suggests that microtubules avoid environmental decoherence long enough to reach threshold for ``self-collapse'' (objective reduction) by a quantum gravity mechanism put forth by Penrose. The model has been criticized as regards the issue of environmental decoherence, and a recent report by Tegmark finds that microtubules can maintain quantum coherence for only 10-13 s, far too short to be neurophysiologically relevant. Here, we critically examine the decoherence mechanisms likely to dominate in a biological setting and find that (1) Tegmark's commentary is not aimed at an existing model in the literature but rather at a hybrid that replaces the superposed protein conformations of the orch. OR theory with a soliton in superposition along the microtubule; (2) recalculation after correcting for differences between the model on which Tegmark bases his calculations and the orch. OR model (superposition separation, charge vs dipole, dielectric constant) lengthens the decoherence time to 10-5-10-4 s (3) decoherence times on this order invalidate the assumptions of the derivation and determine the approximation regime considered by Tegmark to be inappropriate to the orch. OR superposition; (4) Tegmark's formulation yields decoherence times that increase with temperature contrary to well-established physical intuitions and the observed behavior of quantum coherent states; (5) incoherent metabolic energy supplied to the collective dynamics ordering water in the vicinity of microtubules at a rate exceeding that of decoherence can counter decoherence effects (in the same way that lasers avoid decoherence at room temperature); (6) microtubules are surrounded by a Debye layer of counterions, which can screen thermal fluctuations, and by an actin gel that might enhance the ordering of water in bundles of microtubules, further increasing the decoherence-free zone by an order of magnitude and, if the dependence on the distance between environmental ion and superposed state is accurately reflected in Tegmark's calculation, extending decoherence times by three orders of magnitude; (7) topological quantum computation in microtubules may be error correcting, resistant to decoherence; and (8) the decohering effect of radiative scatterers on microtubule quantum states is negligible. These considerations bring microtubule decoherence into a regime in which quantum gravity could interact with neurophysiology.

  6. Flux-controlled quantum computation with Majorana zero modes

    NASA Astrophysics Data System (ADS)

    Hyart, Timo; van Heck, Bernard; Fulga, Ion Cosma; Burrello, Michele; Akhmerov, Anton R.; Beenakker, Carlo W. J.

    2014-03-01

    Majorana zero modes, exotic quasiparticles which are their own antiparticles, can be constructed out of electron and hole excitations in topological superconductors. Because widely separated Majorana zero modes can store quantum information nonlocally and their non-Abelian braiding statistics allows accurate quantum gates, Majorana zero modes offer a promise for topological quantum computation. The coupling of Majorana zero modes to superconducting transmon qubits permits braiding of Majoranas and readout operations by external variation of magnetic fluxes. We identify the minimal circuit for the demonstration of the non-Abelian Majorana statistics and discuss the possible limitations which might hinder the braiding operation. A key benefit of our approach is that the whole operation is performed at the electrical circuit level, without requiring local control of microscopic parameters. Finally, we take a longer term perspective and introduce the Random Access Majorana Memory, a scalable circuit that can perform a joint parity measurement on Majoranas belonging to a selection of topological qubits. Such multi-qubit measurements allow for the efficient creation of highly entangled states and simplify quantum error correction protocols by avoiding the need for ancilla qubits.

  7. Quantum computing with cold atoms and Rydberg blockade

    NASA Astrophysics Data System (ADS)

    Saffman, Mark

    2015-05-01

    Optically trapped neutral atoms are one of several leading approaches to scalable quantum information processing. When prepared in electronic ground states in deep optical lattices atomic qubits are weakly interacting with long coherence times. Excitation to Rydberg states turns on strong interactions which enable fast gates and entanglement generation through either coherent evolution or dissipative dynamics. Rydberg interactions can be applied in a variety of ways enabling control of single atom qubits, multi-atom ensemble qubits, and hybrid entanglement between different types of atoms, between atoms and photons, or between atoms and solid state qubits. I will present advances that leverage strong Rydberg interactions for implementation of a small scale quantum computing device. We trap 30 or more atomic qubits in a 2D array of 49 sites. Single qubit gates are performed with fidelities better than 0.999 as characterized by random benchmarking. Two-qubit gates and entanglement are demonstrated between qubit pairs. Experimental gate fidelities are not yet sufficient for reliable error correction and scalable quantum computation. I will describe prospects for reaching the fault tolerance threshold based on new gate protocols with the potential for fast generation of entanglement at fidelities better than 0.9999. Work supported by the NSF, IARPA MQCO program, ARO, and AFOSR.

  8. Multilevel distillation of magic states for quantum computing

    NASA Astrophysics Data System (ADS)

    Jones, Cody

    2013-03-01

    We develop a procedure for distilling magic states used in universal quantum computing which requires substantially fewer resources than prior schemes. Our distillation circuit is based on a family of concatenated quantum codes with a transversal Hadamard operation which can distill the eigenstate of the Hadamard operator. A crucial result of this design is that low-fidelity magic states can be consumed to purify high-fidelity magic states to even higher fidelity, which we call ``multilevel distillation.'' We show numerically that there exist multilevel protocols such that the average number of magic states consumed to distill from error rate ?in = 0 . 01 to ?out in the range 10-5 to 10-40 is about 14log10 (1 /?out) - 40 ; the efficiency of multilevel distillation dominates all other reported protocols when distilling Hadamard magic states from initial infidelity 0.01 to any final infidelity below 10-7. These methods are an important advance for magic-state distillation circuits in high-performance quantum computing.

  9. Quantum computer networks with the orbital angular momentum of light

    NASA Astrophysics Data System (ADS)

    Garcia-Escartin, Juan Carlos; Chamorro-Posada, Pedro

    2012-09-01

    Inside computer networks, different information processing tasks are necessary to deliver the user data efficiently. This processing can also be done in the quantum domain. We present simple optical quantum networks where the orbital angular momentum (OAM) of a single photon is used as an ancillary degree of freedom which controls decisions at the network level. Linear optical elements are enough to provide important network primitives such as multiplexing and routing. First we show how to build a simple multiplexer and demultiplexer which combine photonic qubits and separate them again at the receiver. We also give two different self-routing networks where the OAM of an input photon is enough to make it find its desired destination.

  10. Spin-based quantum computing using electrons on liquid helium

    SciTech Connect

    Lyon, S. A.

    2006-11-15

    Numerous physical systems have been proposed for constructing quantum computers, but formidable obstacles stand in the way of making even modest systems with a few hundred quantum bits (qubits). Several approaches utilize the spin of an electron as the qubit. Here it is suggested that the spin of electrons floating on the surface of liquid helium will make excellent qubits. These electrons can be electrostatically held and manipulated much like electrons in semiconductor heterostructures, but being in a vacuum the spins on helium suffer much less decoherence. In particular, the spin-orbit interaction is reduced so that moving the qubits with voltages applied to gates has little effect on their coherence. Remaining sources of decoherence are considered, and it is found that coherence times for electron spins on helium can be expected to exceed 100 s. It is shown how to obtain a controlled-NOT operation between two qubits using the magnetic dipole-dipole interaction.

  11. Fast and robust quantum computation with ionic Wigner crystals

    SciTech Connect

    Baltrusch, J. D.; Negretti, A.; Taylor, J. M.; Calarco, T.

    2011-04-15

    We present a detailed analysis of the modulated-carrier quantum phase gate implemented with Wigner crystals of ions confined in Penning traps. We elaborate on a recent scheme, proposed by two of the authors, to engineer two-body interactions between ions in such crystals. We analyze the situation in which the cyclotron ({omega}{sub c}) and the crystal rotation ({omega}{sub r}) frequencies do not fulfill the condition {omega}{sub c}=2{omega}{sub r}. It is shown that even in the presence of the magnetic field in the rotating frame the many-body (classical) Hamiltonian describing small oscillations from the ion equilibrium positions can be recast in canonical form. As a consequence, we are able to demonstrate that fast and robust two-qubit gates are achievable within the current experimental limitations. Moreover, we describe a realization of the state-dependent sign-changing dipole forces needed to realize the investigated quantum computing scheme.

  12. Universal quantum computation with ordered spin-chain networks

    SciTech Connect

    Tserkovnyak, Yaroslav; Loss, Daniel

    2011-09-15

    It is shown that anisotropic spin chains with gapped bulk excitations and magnetically ordered ground states offer a promising platform for quantum computation, which bridges the conventional single-spin-based qubit concept with recently developed topological Majorana-based proposals. We show how to realize the single-qubit Hadamard, phase, and {pi}/8 gates as well as the two-qubit controlled-not (cnot) gate, which together form a fault-tolerant universal set of quantum gates. The gates are implemented by judiciously controlling Ising exchange and magnetic fields along a network of spin chains, with each individual qubit furnished by a spin-chain segment. A subset of single-qubit operations is geometric in nature, relying on control of anisotropy of spin interactions rather than their strength. We contrast topological aspects of the anisotropic spin-chain networks to those of p-wave superconducting wires discussed in the literature.

  13. Majorana Fermion Surface Code for Universal Quantum Computation

    NASA Astrophysics Data System (ADS)

    Vijay, Sagar; Hsieh, Timothy H.; Fu, Liang

    2015-10-01

    We introduce an exactly solvable model of interacting Majorana fermions realizing Z2 topological order with a Z2 fermion parity grading and lattice symmetries permuting the three fundamental anyon types. We propose a concrete physical realization by utilizing quantum phase slips in an array of Josephson-coupled mesoscopic topological superconductors, which can be implemented in a wide range of solid-state systems, including topological insulators, nanowires, or two-dimensional electron gases, proximitized by s -wave superconductors. Our model finds a natural application as a Majorana fermion surface code for universal quantum computation, with a single-step stabilizer measurement requiring no physical ancilla qubits, increased error tolerance, and simpler logical gates than a surface code with bosonic physical qubits. We thoroughly discuss protocols for stabilizer measurements, encoding and manipulating logical qubits, and gate implementations.

  14. Quantum simulators.

    PubMed

    Buluta, Iulia; Nori, Franco

    2009-10-01

    Quantum simulators are controllable quantum systems that can be used to simulate other quantum systems. Being able to tackle problems that are intractable on classical computers, quantum simulators would provide a means of exploring new physical phenomena. We present an overview of how quantum simulators may become a reality in the near future as the required technologies are now within reach. Quantum simulators, relying on the coherent control of neutral atoms, ions, photons, or electrons, would allow studying problems in various fields including condensed-matter physics, high-energy physics, cosmology, atomic physics, and quantum chemistry. PMID:19797653

  15. Computer-aided design and computer science technology

    NASA Technical Reports Server (NTRS)

    Fulton, R. E.; Voigt, S. J.

    1976-01-01

    A description is presented of computer-aided design requirements and the resulting computer science advances needed to support aerospace design. The aerospace design environment is examined, taking into account problems of data handling and aspects of computer hardware and software. The interactive terminal is normally the primary interface between the computer system and the engineering designer. Attention is given to user aids, interactive design, interactive computations, the characteristics of design information, data management requirements, hardware advancements, and computer science developments.

  16. Multilevel distillation of magic states for quantum computing

    NASA Astrophysics Data System (ADS)

    Jones, Cody

    2013-04-01

    We develop a procedure for distilling magic states used in universal quantum computing that requires substantially fewer initial resources than prior schemes. Our distillation circuit is based on a family of concatenated quantum codes that possess a transversal Hadamard operation, enabling each of these codes to distill the eigenstate of the Hadamard operator. A crucial result of this design is that low-fidelity magic states can be consumed to purify other high-fidelity magic states to even higher fidelity, which we call multilevel distillation. When distilling in the asymptotic regime of infidelity ??0 for each input magic state, the number of input magic states consumed on average to yield an output state with infidelity O(?2r) approaches 2r+1, which comes close to saturating the conjectured bound in another investigation [Bravyi and Haah, Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.86.052329 86, 052329 (2012)]. We show numerically that there exist multilevel protocols such that the average number of magic states consumed to distill from error rate ?in=0.01 to ?out in the range 10-5-10-40 is about 14log10(1/?out)-40; the efficiency of multilevel distillation dominates all other reported protocols when distilling Hadamard magic states from initial infidelity 0.01 to any final infidelity below 10-7. These methods are an important advance for magic-state distillation circuits in high-performance quantum computing and provide insight into the limitations of nearly resource-optimal quantum error correction.

  17. Radix-independent, efficient arrays for multi-level n-qudit quantum and reversible computation

    NASA Astrophysics Data System (ADS)

    Mohammadi, Majid

    2015-08-01

    Multiple-valued quantum logic allows the designers to reduce the number of cells while obtaining more functionality in the quantum circuits. Large r-valued reversible or quantum gates ( r stands for radix and is more than 2) cannot be directly realized in the current quantum technology. Therefore, we are interested in designing the large reversible and quantum controlled gates using the arrays of one-quantum digit (qudit) or two-qudit gates. In our previous work, we proposed quantum arrays to implement the r-valued quantum circuits. In this paper, we propose novel efficient structures and arrays, for r-valued quantum logic gates. The quantum costs of the developed quantum arrays are independent of the radix of calculations in the quantum circuit.

  18. Technology of multiple quantum well infrared detectors

    NASA Astrophysics Data System (ADS)

    Bois, Philippe F.; Costard, Eric M.; Duboz, Jean-Yves; Nagle, Julien

    1997-08-01

    During the last decade, the QWIPs technology has improved from start to an undeniable maturity level. High performance focal plane arrays have already been realized (ATT, Lockheed-Martin, JPL, . . .) with a spectacular format increase ranging from 128 by 128 up to 640 by 480, and images from bicolor 256 by 256 arrays have been shown last year. All these devices illustrate the high potential of the QWIP technology. In the same time, the modeling of detection mechanism has advanced to permit the present design of specific detectors and their optimization in given operating environments (near 77 K detector temperature for instance). In this communication, we summarize our recent technological studies leading to the next generation of very large infrared detector arrays. We present the QWIP ultimate performances allowed by the standard dual III - V technological processes developed at THOMSON CSF, in terms of pixel size, array filling factor or connectics. The influence of the pixel size for the grating optical coupling is analyzed. We finally include in this analysis our results for more complex devices like multispectral infrared detectors.

  19. Computer vision research with new imaging technology

    NASA Astrophysics Data System (ADS)

    Hou, Guangqi; Liu, Fei; Sun, Zhenan

    2015-12-01

    Light field imaging is capable of capturing dense multi-view 2D images in one snapshot, which record both intensity values and directions of rays simultaneously. As an emerging 3D device, the light field camera has been widely used in digital refocusing, depth estimation, stereoscopic display, etc. Traditional multi-view stereo (MVS) methods only perform well on strongly texture surfaces, but the depth map contains numerous holes and large ambiguities on textureless or low-textured regions. In this paper, we exploit the light field imaging technology on 3D face modeling in computer vision. Based on a 3D morphable model, we estimate the pose parameters from facial feature points. Then the depth map is estimated through the epipolar plane images (EPIs) method. At last, the high quality 3D face model is exactly recovered via the fusing strategy. We evaluate the effectiveness and robustness on face images captured by a light field camera with different poses.

  20. Two results in topology, motivated by quantum computation

    NASA Astrophysics Data System (ADS)

    Alagic, Gorjan

    2015-03-01

    The field of quantum computation is built on the foundation of physics, mathematics, and computer science. While it has taken much from these fields, there are also interesting examples where it has given back. I will discuss two new results of this kind. In both cases, we use very basic ideas from quantum computation to prove an interesting fact about low-dimensional topology. First, we use the Solovay-Kitaev universality theorem with exponential precision to give a simple proof of the #P-hardness of certain 3-manifold invariants. We then apply this result to show the existence of rather exotic 3-manifold diagrams. Second, we show a relationship between the distinguishing power of a link invariant, and the entangling power of the linear operator associated to braiding. More precisely, we show that link invariants derived from non-entangling solutions to the Yang-Baxter equation are trivial. The former is joint work with Catharine Lo (Caltech), and the latter is joint work with Stephen Jordan and Michael Jarett (UMD).

  1. Development of a solid-state quantum computer: Single electron transistors and highly charged ion implantation

    NASA Astrophysics Data System (ADS)

    Park, Sang Joon

    2004-12-01

    A proposal to manipulate phosphorous quantum bits in silicon has been studied as a new concept of the next generation computing. Quantum information systems in a silicon structure have a lot of advantages in terms of the scalability and the usage of advanced silicon technology. We studied solid-state quantum bit (qubit) schemes of dual phosphorous atom interactions in the crystalline silicon matrix. In this thesis, the developmental processes and the results from this study will be shown. This experimental approach includes a single ion implantation scheme into a registered position using highly charged ion sources and a single electron transistor read-out scheme using nanowires based on silicon fabrication technology. Firstly, the single ion implantation scheme is based on slow (slower than the Bohr velocity: v < vBohr = 2.2 x 106 m/s) highly charged ions (SHCIs) extracted from the Electron Beam Ion Trap (EBIT) at the Lawrence Berkeley National Lab (LBNL). HCIs lose their electrons in an ion trap coupled with a high current density electron beam. An ion with few electrons can have a potential energy in a range of 10 to 100 keV The ion releases its potential energy in a time scale of 10 femto seconds (ultra-fast interaction) on a solid surface. This effect leads to electron emissions from the surface, which is proportional to the released potential energy. Hence, the efficiency of detecting single ions is higher than for singly-charged ions. Secondly, we have formed 10--30 nm wires on a silicon wafer as a sensor to detect the phosphorous atom interactions inside the silicon solid matrix. Electron beam lithography (EBL) technology can pattern the wire size down to 10 nm scale. In this device, the sensitivity of a nanowire plays an important role in implementing the solid-state quantum computer.

  2. Diamond as a Solid State Quantum Computer with a Linear Chain of Nuclear Spins System

    NASA Astrophysics Data System (ADS)

    Lpez, G. V.; Lpez, G. V.

    By removing a $^{12}C$ atom from the tetrahedral configuration of the diamond, replace it by a $^{13}C$ atom, and repeating this in a linear direction, it is possible to have a linear chain of nuclear spins one half and to build a solid state quantum computer. One qubit rotation and controlled-not (CNOT) quantum gates are obtained immediately from this configuration, and CNOT quantum gate is used to determined the design parameters of this quantum computer.

  3. Toward fault-tolerant quantum computation without concatenation

    NASA Astrophysics Data System (ADS)

    Dennis, Eric

    2001-05-01

    It is known that quantum error correction via concatenated codes can be done with exponentially small failure rate if the error rate for physical qubits is below a certain accuracy threshold. Other, unconcatenated codes with their own attractive features such as improved accuracy threshold, local operations, have also been studied. By iteratively distilling a certain two-qubit entangled state it is shown how to perform an encoded Toffoli gate, important for universal computation, on codes whose C-NOT operation is bitwise. For certain codes, over a very large range of block sizes, this technique requires at most one concatenation.

  4. Large-scale modular quantum-computer architecture with atomic memory and photonic interconnects

    NASA Astrophysics Data System (ADS)

    Monroe, C.; Raussendorf, R.; Ruthven, A.; Brown, K. R.; Maunz, P.; Duan, L.-M.; Kim, J.

    2014-02-01

    The practical construction of scalable quantum-computer hardware capable of executing nontrivial quantum algorithms will require the juxtaposition of different types of quantum systems. We analyze a modular ion trap quantum-computer architecture with a hierarchy of interactions that can scale to very large numbers of qubits. Local entangling quantum gates between qubit memories within a single register are accomplished using natural interactions between the qubits, and entanglement between separate registers is completed via a probabilistic photonic interface between qubits in different registers, even over large distances. We show that this architecture can be made fault tolerant, and demonstrate its viability for fault-tolerant execution of modest size quantum circuits.

  5. Computer Graphics. Curriculum Guide for Technology Education.

    ERIC Educational Resources Information Center

    Craft, Clyde O.

    This curriculum guide for a 1-quarter or 1-semester course in computer graphics is designed to be used with Apple II computers. Some of the topics covered include the following: computer graphics terminology and applications, operating Apple computers, graphics programming in BASIC using various programs and commands, computer graphics painting,

  6. Quantum Mechanics for Everyone: Can it be done with Technology?

    NASA Astrophysics Data System (ADS)

    Zollman, Dean

    2004-10-01

    The Visual Quantum Mechanics project has created a series of teaching/learning units to introduce quantum physics to a variety of audiences ranging from high school students who normally would not study these topics to undergraduate physics majors. Most recently we have been developing materials relating modern medical procedures and contemporary physics. In all of these materials interactive computer visualizations are coupled with hands-on experiences to create a series of activities which help students learn about some aspects of quantum mechanics. Our goal is to enable students to obtain a qualitative and, where appropriate, a quantitative understanding of contemporary ideas in physics. Included in the instructional materials are student-centered activities that address a variety of concepts in quantum physics and applications to devices such as the light emitting diode, the electron microscope, an inexpensive infrared detection card, and the Star Trek Transporter. Whenever possible the students begin the study of a new concept with an experiment using inexpensive equipment. They, then, build models of the physical phenomenon using interactive computer visualization and conclude by applying those models to new situations. For physics students these visualizations are usually followed by a mathematical approach. For others the visualizations provide a framework for understanding the concepts. Thus, Visual Quantum Mechanics allows a wide range of students to begin to understand the basic concepts, implications and interpretations of quantum physics. At present we are building on this foundation to create materials which show the connection between contemporary physics and modern medical diagnosis. Additional information is available at http://web.phys.ksu.edu/.

  7. Attitudes to Technology, Perceived Computer Self-Efficacy and Computer Anxiety as Predictors of Computer Supported Education

    ERIC Educational Resources Information Center

    Celik, Vehbi; Yesilyurt, Etem

    2013-01-01

    There is a large body of research regarding computer supported education, perceptions of computer self-efficacy, computer anxiety and the technological attitudes of teachers and teacher candidates. However, no study has been conducted on the correlation between and effect of computer supported education, perceived computer self-efficacy, computer

  8. Ion traps, quantum computing, and the measurement problem^

    NASA Astrophysics Data System (ADS)

    Wineland, D. J.

    2006-05-01

    The basic requirements for quantum computing and quantum simulation (single- and multi-qubit gates, long memory times, etc.) have been demonstrated in separate experiments on trapped ions. Construction of a useful information processor will require synthesis of these elements and implementation of high- fidelity operations on a very large number of qubits. NIST and other groups are addressing this scaling issue by trying to fabricate multi-zone arrays of traps that would allow highly- parallel processing. As the number of qubits increases, the measurement problem in quantum mechanics becomes more glaring; with luck, trapped ion systems might be able to shed light on this fundamental issue. Recent NIST work in collaboration with D. Leibfried, J. C. Bergquist, R. B. Blakestad, J. J. Bollinger, J. Britton, J. Chiaverini, R. E. Drullinger, R. Epstein, D. Hume, W. M. Itano, J. D. Jost, J. Koelemeij, E. Knill, C. Langer, R. Ozeri, R. Reichle, T. Rosenband, P. O. Schmidt, S. Seidelin, N. Shiga, and J. Wesenberg, and supported by DTO, ONR, and NIST.

  9. Computing the rates of measurement-induced quantum jumps

    NASA Astrophysics Data System (ADS)

    Bauer, Michel; Bernard, Denis; Tilloy, Antoine

    2015-06-01

    Small quantum systems can now be continuously monitored experimentally which allows for the reconstruction of quantum trajectories. A peculiar feature of these trajectories is the emergence of jumps between the eigenstates of the observable which is measured. Using the stochastic master equation (SME) formalism for continuous quantum measurements, we show that the density matrix of a system indeed shows a jumpy behaviour when it is subjected to a tight measurement (even if the noise in the SME is Gaussian). We are able to compute the jump rates analytically for any system evolution, i.e. any Lindbladian, and we illustrate how our general recipe can be applied to two simple examples. We then discuss the mathematical, foundational and practical applications of our results. The analysis we present is based on a study of the strong noise limit of a class of stochastic differential equations (the SME) and as such the method may be applicable to other physical situations in which a strong noise limit plays a role.

  10. Computer Science and Technology Publications. NBS Publications List 84.

    ERIC Educational Resources Information Center

    National Bureau of Standards (DOC), Washington, DC. Inst. for Computer Sciences and Technology.

    This bibliography lists publications of the Institute for Computer Sciences and Technology of the National Bureau of Standards. Publications are listed by subject in the areas of computer security, computer networking, and automation technology. Sections list publications of: (1) current Federal Information Processing Standards; (2) computer…

  11. Mobile Computing and Ubiquitous Networking: Concepts, Technologies and Challenges.

    ERIC Educational Resources Information Center

    Pierre, Samuel

    2001-01-01

    Analyzes concepts, technologies and challenges related to mobile computing and networking. Defines basic concepts of cellular systems. Describes the evolution of wireless technologies that constitute the foundations of mobile computing and ubiquitous networking. Presents characterization and issues of mobile computing. Analyzes economical and

  12. Computer Utilization in Industrial Arts/Technology Education. Curriculum Guide.

    ERIC Educational Resources Information Center

    Connecticut Industrial Arts Association.

    This guide is intended to assist industrial arts/technology education teachers in helping students in grades K-12 understand the impact of computers and computer technology in the world. Discussed in the introductory sections are the ways in which computers have changed the face of business, industry, and education and training; the scope and…

  13. Computer Utilization in Industrial Arts/Technology Education. Curriculum Guide.

    ERIC Educational Resources Information Center

    Connecticut Industrial Arts Association.

    This guide is intended to assist industrial arts/technology education teachers in helping students in grades K-12 understand the impact of computers and computer technology in the world. Discussed in the introductory sections are the ways in which computers have changed the face of business, industry, and education and training; the scope and

  14. Computation Directorate and Science& Technology Review Computational Science and Research Featured in 2002

    SciTech Connect

    Alchorn, A L

    2003-04-04

    Thank you for your interest in the activities of the Lawrence Livermore National Laboratory Computation Directorate. This collection of articles from the Laboratory's Science & Technology Review highlights the most significant computational projects, achievements, and contributions during 2002. In 2002, LLNL marked the 50th anniversary of its founding. Scientific advancement in support of our national security mission has always been the core of the Laboratory. So that researchers could better under and predict complex physical phenomena, the Laboratory has pushed the limits of the largest, fastest, most powerful computers in the world. In the late 1950's, Edward Teller--one of the LLNL founders--proposed that the Laboratory commission a Livermore Advanced Research Computer (LARC) built to Livermore's specifications. He tells the story of being in Washington, DC, when John Von Neumann asked to talk about the LARC. He thought Teller wanted too much memory in the machine. (The specifications called for 20-30,000 words.) Teller was too smart to argue with him. Later Teller invited Von Neumann to the Laboratory and showed him one of the design codes being prepared for the LARC. He asked Von Neumann for suggestions on fitting the code into 10,000 words of memory, and flattered him about ''Labbies'' not being smart enough to figure it out. Von Neumann dropped his objections, and the LARC arrived with 30,000 words of memory. Memory, and how close memory is to the processor, is still of interest to us today. Livermore's first supercomputer was the Remington-Rand Univac-1. It had 5600 vacuum tubes and was 2 meters wide by 4 meters long. This machine was commonly referred to as a 1 KFlop machine [E+3]. Skip ahead 50 years. The ASCI White machine at the Laboratory today, produced by IBM, is rated at a peak performance of 12.3 TFlops or E+13. We've improved computer processing power by 10 orders of magnitude in 50 years, and I do not believe there's any reason to think we won't improve another 10 orders of magnitude in the next 50 years. For years I have heard talk of hitting the physical limits of Moore's Law, but new technologies will take us into the next phase of computer processing power such as 3-D chips, molecular computing, quantum computing, and more. Big computers are icons or symbols of the culture and larger infrastructure that exists at LLNL to guide scientific discovery and engineering development. We have dealt with balance issues for 50 years and will continue to do so in our quest for a digital proxy of the properties of matter at extremely high temperatures and pressures. I believe that the next big computational win will be the merger of high-performance computing with information management. We already create terabytes--soon to be petabytes--of data. Efficiently storing, finding, visualizing and extracting data and turning that into knowledge which aids decision-making and scientific discovery is an exciting challenge. In the meantime, please enjoy this retrospective on computational physics, computer science, advanced software technologies, and applied mathematics performed by programs and researchers at LLNL during 2002. It offers a glimpse into the stimulating world of computational science in support of the national missions and homeland defense.

  15. P/NP, and the quantum field computer.

    PubMed

    Freedman, M H

    1998-01-01

    The central problem in computer science is the conjecture that two complexity classes, P (polynomial time) and NP (nondeterministic polynomial time-roughly those decision problems for which a proposed solution can be checked in polynomial time), are distinct in the standard Turing model of computation: P not equal NP. As a generality, we propose that each physical theory supports computational models whose power is limited by the physical theory. It is well known that classical physics supports a multitude of implementation of the Turing machine. Non-Abelian topological quantum field theories exhibit the mathematical features necessary to support a model capable of solving all #P problems, a computationally intractable class, in polynomial time. Specifically, Witten [Witten, E. (1989) Commun. Math. Phys. 121, 351-391] has identified expectation values in a certain SU(2)-field theory with values of the Jones polynomial [Jones, V. (1985) Bull. Am. Math. Soc. 12, 103-111] that are #P-hard [Jaeger, F., Vertigen, D. & Welsh, D. (1990) Math. Proc. Comb. Philos. Soc. 108, 35-53]. This suggests that some physical system whose effective Lagrangian contains a non-Abelian topological term might be manipulated to serve as an analog computer capable of solving NP or even #P-hard problems in polynomial time. Defining such a system and addressing the accuracy issues inherent in preparation and measurement is a major unsolved problem. PMID:9419335

  16. Computing, Information, and Communications Technology (CICT) Program Overview

    NASA Technical Reports Server (NTRS)

    VanDalsem, William R.

    2003-01-01

    The Computing, Information and Communications Technology (CICT) Program's goal is to enable NASA's Scientific Research, Space Exploration, and Aerospace Technology Missions with greater mission assurance, for less cost, with increased science return through the development and use of advanced computing, information and communication technologies

  17. Approximating ground and excited state energies on a quantum computer

    NASA Astrophysics Data System (ADS)

    Hadfield, Stuart; Papageorgiou, Anargyros

    2015-04-01

    Approximating ground and a fixed number of excited state energies, or equivalently low-order Hamiltonian eigenvalues, is an important but computationally hard problem. Typically, the cost of classical deterministic algorithms grows exponentially with the number of degrees of freedom. Under general conditions, and using a perturbation approach, we provide a quantum algorithm that produces estimates of a constant number of different low-order eigenvalues. The algorithm relies on a set of trial eigenvectors, whose construction depends on the particular Hamiltonian properties. We illustrate our results by considering a special case of the time-independent Schrödinger equation with degrees of freedom. Our algorithm computes estimates of a constant number of different low-order eigenvalues with error and success probability at least , with cost polynomial in and . This extends our earlier results on algorithms for estimating the ground state energy. The technique we present is sufficiently general to apply to problems beyond the application studied in this paper.

  18. Dynamics of entanglement in quantum computers with imperfections.

    PubMed

    Montangero, Simone; Benenti, Giuliano; Fazio, Rosario

    2003-10-31

    The dynamics of the pairwise entanglement in a qubit lattice in the presence of static imperfections exhibits different regimes. We show that there is a transition from a perturbative region, where the entanglement is stable against imperfections, to the ergodic regime, in which a pair of qubits becomes entangled with the rest of the lattice and the pairwise entanglement drops to zero. The transition is almost independent of the size of the quantum computer. We consider both the case of an initial maximally entangled and separable state. In this last case there is a broad crossover region in which the computer imperfections can be used to create a significant amount of pairwise entanglement. PMID:14611314

  19. Reducing the quantum-computing overhead with complex gate distillation

    NASA Astrophysics Data System (ADS)

    Duclos-Cianci, Guillaume; Poulin, David

    2015-04-01

    In leading fault-tolerant quantum-computing schemes, accurate transformations are obtained by a two-stage process. In a first stage, a discrete universal set of fault-tolerant operations is obtained by error-correcting noisy transformations and distilling resource states. In a second stage, arbitrary transformations are synthesized to desired accuracy by combining elements of this set into a circuit. Here we present a scheme that merges these two stages into a single one, directly distilling complex transformations. We find that our scheme can reduce the total overhead to realize certain gates by up to a few orders of magnitude. In contrast to other schemes, this efficient gate synthesis does not require computationally intensive compilation algorithms and a straightforward generalization of our scheme circumvents compilation and synthesis altogether.

  20. Shortcuts to adiabatic holonomic quantum computation in decoherence-free subspace with transitionless quantum driving algorithm

    NASA Astrophysics Data System (ADS)

    Song, Xue-Ke; Zhang, Hao; Ai, Qing; Qiu, Jing; Deng, Fu-Guo

    2016-02-01

    By using transitionless quantum driving algorithm (TQDA), we present an efficient scheme for the shortcuts to the holonomic quantum computation (HQC). It works in decoherence-free subspace (DFS) and the adiabatic process can be speeded up in the shortest possible time. More interestingly, we give a physical implementation for our shortcuts to HQC with nitrogen-vacancy centers in diamonds dispersively coupled to a whispering-gallery mode microsphere cavity. It can be efficiently realized by controlling appropriately the frequencies of the external laser pulses. Also, our scheme has good scalability with more qubits. Different from previous works, we first use TQDA to realize a universal HQC in DFS, including not only two noncommuting accelerated single-qubit holonomic gates but also a accelerated two-qubit holonomic controlled-phase gate, which provides the necessary shortcuts for the complete set of gates required for universal quantum computation. Moreover, our experimentally realizable shortcuts require only two-body interactions, not four-body ones, and they work in the dispersive regime, which relax greatly the difficulty of their physical implementation in experiment. Our numerical calculations show that the present scheme is robust against decoherence with current experimental parameters.