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1

Quantum computing  

PubMed Central

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.

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

2001-01-01

2

Quantum computing  

Microsoft Academic Search

The subject of quantum computing brings together ideas from classical information theory, computer science, and quantum physics. This review aims to summarise not just quantum computing, but the whole subject of quantum information theory. It turns out that information theory and quantum mechanics fit together very well. In order to explain their relationship, the review begins with an introduction to

Andrew Steane

1998-01-01

3

Technology Development for Linear Optics Quantum Computing Program.  

National Technical Information Service (NTIS)

This is the final report for an augmentation grant to investigate a linear optics approach to quantum computing. The main results of the study include a demonstration of a CNOT logic gate, a source of single photons on demand, a quantum memory device for ...

J. D. Franson

2005-01-01

4

Quantum Computing  

NASA Astrophysics Data System (ADS)

Quantum mechanics plays a crucial role in many day-to-day products, and has been successfully used to explain a wide variety of observations in Physics. While some quantum effects such as tunneling limit the degree to which modern CMOS devices can be scaled to ever reducing dimensions, others may potentially be exploited to build an entirely new computing architecture: The quantum computer. In this talk I will review several basic concepts of a quantum computer. Why quantum computing and how do we do it? What is the status of several (but not all) approaches towards building a quantum computer, including IBM's approach using superconducting qubits? And what will it take to build a functional machine? The promise is that a quantum computer could solve certain interesting computational problems such as factoring using exponentially fewer computational steps than classical systems. Although the most sophisticated modern quantum computing experiments to date do not outperform simple classical computations, it is increasingly becoming clear that small scale demonstrations with as many as 100 qubits are beginning to be within reach over the next several years. Such a demonstration would undoubtedly be a thrilling feat, and usher in a new era of controllably testing quantum mechanics or quantum computing aspects. At the minimum, future demonstrations will shed much light on what lies ahead.

Steffen, Matthias

2013-03-01

5

Quantum Computation.  

National Technical Information Service (NTIS)

Two seemingly unrelated scientific disciplines, information processing and quantum mechanics, were separately developed, until physicist Richard Feynman proposed their combination. Today, quantum computation is at the forefront of research in theoretical ...

D. Giannakopoulos

1999-01-01

6

Quantum Computing  

Microsoft Academic Search

Given its placement at the end of this book, the reader will surmise that this chapter on quantum computing represents the\\u000a farthest destination out from planar silicon CMOS along the road to the nano era. This would be a mistaken impression. Quantum\\u000a computing is not a topic in nanotechnology, although it may eventually benefit from some avenues in nano research.

D. P. DiVincenzo

7

Quantum leap for quantum computing  

Microsoft Academic Search

This paper reports on a promising technology for constructing an ultrapowerful quantum computer, called the ion trap. Researchers have found a way to build ion traps from semiconductors in much the same way as computer chips. By linking several of these ion trap chips, researchers are able to manipulate much larger numbers of ions and demonstrate rudimentary components of a

J. R. Minkel

2006-01-01

8

Quantum Computing Graduate Fellowship.  

National Technical Information Service (NTIS)

A variety of projects are carried out by 2 graduate students under the Quantum Computing and Graduate Research Fellowship' program. The students are United States citizens, with undergraduate degrees from the California Institute of Technology. The graawa...

I. H. Deutsch C. M. Caves

2005-01-01

9

Quantum computers? … Coherent computers!  

NASA Astrophysics Data System (ADS)

Attention is drawn to the fact that the computer that employs a superposition of states as the basis for its operation can be implemented by not only quantum but also classical elements, whose dynamics obey classical laws of motion. It is shown that the term "coherent computer" better reflects the physical principle of the computational devices based on the superposition of states.

Oraevsky, A. N.

2001-09-01

10

Quantum Information Technology  

NSDL National Science Digital Library

From the research laboratories of Hewlett Packard, Quantum Information Technology provides an informative look at current work in quantum information processing and communication (QIPC). The report, published in November 2002, recognizes the potential applications of QIPC and how it could revolutionize conventional information technology. It cites cryptography, quantum computers, and quantum teleportation as motivational factors for development of this technology, offering a basic introduction to each discipline. The paper concludes with an analysis of the direction current research is taking and what the future may hold. Several links to further sources of information are also included.

Spiller, Timothy.

2002-01-01

11

Quantum computation for quantum chemistry  

NASA Astrophysics Data System (ADS)

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.

Aspuru-Guzik, Alan

2010-03-01

12

Quantum robots and quantum computers.  

National Technical Information Service (NTIS)

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 acti...

P. Benioff

1998-01-01

13

Computer Technology  

NSDL National Science Digital Library

Students will learn the history of computers as well as how computers work. COMPUTER TECHNOLOGY (9-12) - 52.0417 Computer Technology is an introduction to computer application software that includes word processing, spreadsheet, database, and telecommunications. An awareness of career opportunities, business ethics, and trends is included. Everything is done with computers. Your job will most likely have a computer to save files, write ...

Thackeray, Mrs.

2007-10-14

14

Quantum Computing's Classical Problem, Classical Computing's Quantum Problem  

NASA Astrophysics Data System (ADS)

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 10^{30} logic gates per month? This article will discuss the interplay in these competing and cooperating technological trends.

Van Meter, Rodney

2014-06-01

15

Quantum Computational Logic  

Microsoft Academic Search

A quantum computational logic is constructed by employing density operators on spaces of qubits and quantum gates represented by unitary operators. It is shown that this quantum computational logic is isomorphic to the basic sequential effect algebra [0, 1].

S. Gudder

2003-01-01

16

Quantum robots and quantum computers  

SciTech Connect

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.

Benioff, P.

1998-07-01

17

Ion Trap Quantum Computing.  

National Technical Information Service (NTIS)

Richard Feynman first proposed the idea of quantum computers thirty years ago. Since then, efforts have been undertaken to realize large-scale, fault-tolerant quantum computers that can factor large numbers much more quickly than classical computers, whic...

C. Tsampardoukas

2011-01-01

18

Quantum computation with quantum dots  

Microsoft Academic Search

We propose an implementation of a universal set of one- and two-quantum-bit gates for quantum computation using the spin states of coupled single-electron quantum dots. Desired operations are effected by the gating of the tunneling barrier between neighboring dots. Several measures of the gate quality are computed within a recently derived spin master equation incorporating decoherence caused by a prototypical

Daniel Loss; David P. Divincenzo

1998-01-01

19

Quantum computation and Shor's factoring algorithm  

Microsoft Academic Search

Current technology is beginning to allow us to manipulate rather than just observe individual quantum phenomena. This opens up the possibility of exploiting quantum effects to perform computations beyond the scope of any classical computer. Recently Peter Shor discovered an efficient algorithm for factoring whole numbers, which uses characteristically quantum effects. The algorithm illustrates the potential power of quantum computation,

Artur Ekert; Richard Jozsa

1996-01-01

20

Visualizing a silicon quantum computer  

NASA Astrophysics Data System (ADS)

Quantum computation is a fast-growing, multi-disciplinary research field. The purpose of a quantum computer is to execute quantum algorithms that efficiently solve computational problems intractable within the existing paradigm of 'classical' computing built on bits and Boolean gates. While collaboration between computer scientists, physicists, chemists, engineers, mathematicians and others is essential to the project's success, traditional disciplinary boundaries can hinder progress and make communicating the aims of quantum computing and future technologies difficult. We have developed a four minute animation as a tool for representing, understanding and communicating a silicon-based solid-state quantum computer to a variety of audiences, either as a stand-alone animation to be used by expert presenters or embedded into a longer movie as short animated sequences. The paper includes a generally applicable recipe for successful scientific animation production.

Sanders, Barry C.; Hollenberg, Lloyd C. L.; Edmundson, Darran; Edmundson, Andrew

2008-12-01

21

Towards quantum chemistry on a quantum computer.  

PubMed

Exact first-principles calculations of molecular properties are currently intractable because their computational cost grows exponentially with both the number of atoms and basis set size. A solution is to move to a radically different model of computing by building a quantum computer, which is a device that uses quantum systems themselves to store and process data. Here we report the application of the latest photonic quantum computer technology to calculate properties of the smallest molecular system: the hydrogen molecule in a minimal basis. We calculate the complete energy spectrum to 20 bits of precision and discuss how the technique can be expanded to solve large-scale chemical problems that lie beyond the reach of modern supercomputers. These results represent an early practical step toward a powerful tool with a broad range of quantum-chemical applications. PMID:21124400

Lanyon, B P; Whitfield, J D; Gillett, G G; Goggin, M E; Almeida, M P; Kassal, I; Biamonte, J D; Mohseni, M; Powell, B J; Barbieri, M; Aspuru-Guzik, A; White, A G

2010-02-01

22

Quantum Computing for Quantum Chemistry.  

National Technical Information Service (NTIS)

This three-year project consisted on the development and application of quantum computer algorithms for chemical applications. In particular, we developed algorithms for chemical reaction dynamics, electronic structure and protein folding. The first quant...

A. Aspuru-Guzik

2010-01-01

23

QUANTUM COMPUTATION WITH SCATTERING  

Microsoft Academic Search

We discuss possible applications of the 1-D direct and inverse scattering problem to design of universal quantum gates for quantum computation. The potentials generating some universal gates are described. In this article we propose a theory of quantum scattering and notion of unitary scattering matrix to formulate quantum input-output rela- tions. This differs from standard approach to this subject in

G. GIORGADZE; R. TEVZADZE

24

Focus on topological quantum computation  

NASA Astrophysics Data System (ADS)

Topological quantum computation started as a niche area of research aimed at employing particles with exotic statistics, called anyons, for performing quantum computation. Soon it evolved to include a wide variety of disciplines. Advances in the understanding of anyon properties inspired new quantum algorithms and helped in the characterization of topological phases of matter and their experimental realization. The conceptual appeal of topological systems as well as their promise for building fault-tolerant quantum technologies fuelled the fascination in this field. This ‘focus on’ collection brings together several of the latest developments in the field and facilitates the synergy between different approaches.

Pachos, Jiannis K.; Simon, Steven H.

2014-06-01

25

Quantum computer games: quantum minesweeper  

NASA Astrophysics Data System (ADS)

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.

Gordon, Michal; Gordon, Goren

2010-07-01

26

Rabi Quantum Computer.  

National Technical Information Service (NTIS)

This paper sets about to examine how a quantum computer might eventually be exploited. (A quantum computer uses strange but real effects in Quantum Mechanics to explore many possibilities at the same time with the same hardware.) There are currently just ...

R. A. Krutar

2001-01-01

27

Simple quantum computer  

Microsoft Academic Search

We propose an implementation of a quantum computer to solve Deutsch's problem, which requires exponential time on a classical computer but only linear time with quantum parallelism. By using a dual-rail quantum-bit representation as a simple form of error correction, our machine can tolerate some amount of decoherence and still give the correct result with high probability. The design that

Isaac L. Chuang; Yoshihisa Yamamoto

1995-01-01

28

Physics 219: Quantum Computation  

NSDL National Science Digital Library

This is the course web page for an undergraduate Quantum Computation course at Caltech. A course outline, extensive lecture notes, and homework sets, some with solutions, are provided. Links to recent versions of the course are included. There are also links to important references and other web resources in quantum information theory and quantum computation.

Preskill, John

2005-04-16

29

Quantum information and computation  

Microsoft Academic Search

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}.

Charles H. Bennett

1995-01-01

30

Quantum information and computation  

SciTech Connect

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}.

Bennett, C.H. [Thomas J. Watson Research Center, Yorktown Heights, New York (United States)

1995-10-01

31

Quantum Computers and Dissipation  

Microsoft Academic Search

We analyse dissipation in quantum computation and its destructive impact on\\u000aefficiency of quantum algorithms. Using a general model of decoherence, we\\u000astudy the time evolution of a quantum register of arbitrary length coupled with\\u000aan environment of arbitrary coherence length. We discuss relations between\\u000adecoherence and computational complexity and show that the quantum\\u000afactorization algorithm must be modified in

G. Massimo Palma; Kalle-Antti Suominen; Artur K. Ekert

1997-01-01

32

Resilient Quantum Computation  

Microsoft Academic Search

Practical realization of quantum computers will require overcoming decoherence and operational errors, which lead to problems that are more severe than in classical computation. It is shown that arbitrarily accurate quantum computation is possible provided that the error per operation is below a threshold value. 36 refs., 1 fig.

Emanuel Knill; Raymond Laflamme; Wojciech H. Zurek

1998-01-01

33

Type-II Quantum Computers  

Microsoft Academic Search

This paper discusses a computing architecture that uses both classical parallelism and quantum parallelism. We consider a large parallel array of small quantum computers, connected together by classical communication channels. This kind of computer is called a type-II quantum computer, to differentiate it from a globally phase-coherent quantum computer, which is the first type of quantum computer that has received

Jeffrey Yepez

2001-01-01

34

Universal quantum computing with nanowire double quantum dots  

NASA Astrophysics Data System (ADS)

We present a method for implementing universal quantum computing using a singlet and triplets of nanowire double quantum dots coupled to a one-dimensional transmission line resonator. This method is suitable and of interest for both quantum computing and quantum control with inhibition of spontaneous emission, enhanced spin qubit lifetime, strong coupling and quantum nondemolition measurements of spin qubits. We analyze the performance and stability of all the required operations and emphasize that all techniques are feasible with current experimental technology.

Xue, Peng

2011-10-01

35

Experimental quantum computing without entanglement.  

PubMed

Deterministic quantum computation with one pure qubit (DQC1) is an efficient model of computation that uses highly mixed states. Unlike pure-state models, its power is not derived from the generation of a large amount of entanglement. Instead it has been proposed that other nonclassical correlations are responsible for the computational speedup, and that these can be captured by the quantum discord. In this Letter we implement DQC1 in an all-optical architecture, and experimentally observe the generated correlations. We find no entanglement, but large amounts of quantum discord-except in three cases where an efficient classical simulation is always possible. Our results show that even fully separable, highly mixed, states can contain intrinsically quantum mechanical correlations and that these could offer a valuable resource for quantum information technologies. PMID:19113321

Lanyon, B P; Barbieri, M; Almeida, M P; White, A G

2008-11-14

36

Universality in Quantum Computation  

Microsoft Academic Search

We show that in quantum computation almost every gate that operates on two or more bits is a universal gate. We discuss various physical considerations bearing on the proper definition of universality for computational components such as logic gates.

David Deutsch; Adriano Barenco; Artur Ekert

1995-01-01

37

Center for Quantum Computation  

NSDL National Science Digital Library

Researchers at the Center for Quantum Computation (CQC) at Oxford University study "all aspects of quantum information processing" and "the implications of the quantum theory of computation for physics itself." The Center's homepage provides information on each of their four areas of research (Fundamentals, Architecture, Ion Trap, and Nuclear Magnetic Resonance), although content depth varies with subject. Also included at the site are: contact information, email addresses, and homepage links to most CQC members and associates; links to other research centers around the world; and a calendar of events related to quantum computation.

38

Computational quantum field theory  

NASA Astrophysics Data System (ADS)

The computational quantum field theory (CQFT) is considered as part of computational physics. The main mathematical structures of the CQFT are described in the case of quantum chromodynamics. As examples of the application of the CQFT methods, the calculation of the topological susceptibility and the gluon condensates are considered.

Makhaldiani, N. V.

39

Computational Quantum Field Theory.  

National Technical Information Service (NTIS)

The computational quantum field theory (CQFT) is considered as a part of the computational physics. The main mathematical structures of the CQFT are described in the case of quantum chromodynamics. As examples of the application of the CQFT methods the ca...

N. V. Makhaldiani

1986-01-01

40

Quantum physics and computers  

Microsoft Academic Search

Recent theoretical results confirm that quantum theory provides the possibility of new ways of performing efficient calculations. The most striking example is the factoring problem. It has recently been shown that computers that exploit quantum features could factor large composite integers. This task is believed to be out of reach of classical computers as soon as the number of digits

Adriano Barenco

1996-01-01

41

Ancilla-driven universal blind quantum computation  

NASA Astrophysics Data System (ADS)

Blind quantum computation is a new quantum secure protocol, which enables Alice who does not have enough quantum technology to delegate her computation to Bob who has a fully fledged quantum power without revealing her input, output, and algorithm. So far, blind quantum computation has been considered only for the circuit model and the measurement-based model. Here we consider the possibility and the limitation of blind quantum computation in the ancilla-driven model, which is a hybrid of the circuit and the measurement-based models.

Sueki, Takahiro; Koshiba, Takeshi; Morimae, Tomoyuki

2013-06-01

42

IOP: Quantum Computing  

NSDL National Science Digital Library

The publishers of Journal of Physics A: Mathematical and General are offering free access to articles on Classical and Quantum Field Theory from January 2005 until April 2005. The Classical and Quantum Field Theory section of the journal includes articles on "high quality, innovative and significant new results on mathematical physics in areas including: topological objects (such as vortices, solitons, instantons and monopoles), gauge and conformal field theory, quantum electrodynamics and quantum chromodynamics, integrable models, mathematical and computational methods in quantum field theory, and classical field theory." After April 2005, the articles will only be available to paid subscribers.

43

Quantum Information, Computation and Communication  

NASA Astrophysics Data System (ADS)

Part I. Quantum Information: 1. Quantum bits and quantum gates; 2. An atom in a laser field; 3. Spins in magnetic fields; 4. Photon techniques; 5. Two qubits and beyond; 6. Measurement and entanglement; Part II. Quantum Computation: 7. Principles of quantum computing; 8. Elementary quantum algorithms; 9. More advanced quantum algorithms; 10. Trapped atoms and ions; 11. Nuclear magnetic resonance; 12. Large scale quantum computers; Part III. Quantum Communication: 13. Basics of information theory; 14. Quantum information; 15. Quantum communication; 16. Testing EPR; 17. Quantum cryptography; Appendixes; References; Index.

Jones, Jonathan A.; Jaksch, Dieter

2012-07-01

44

Quantum computation: Honesty test  

NASA Astrophysics Data System (ADS)

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.

Morimae, Tomoyuki

2013-11-01

45

Science and Technology Review, May 2007. Simulating Quantum Technologies.  

National Technical Information Service (NTIS)

Contents: Laboratory Science Entwined with Rise in Computing; 'A Quantum Contribution to Technology'.- Quantum mechanics simulations are making the leap from basic to applied nanoscale science. 'U.S. Weapons Plutonium Aging Gracefully' - Advances in pluto...

2007-01-01

46

Lectures on Quantum Computation  

NSDL National Science Digital Library

This series of video lectures is designed to be used either as an introduction to the quantum theory of computation or as an introduction to quantum physics itself. The level of mathematics used is relatively low, requiring only that the viewer understand the concepts of eigenvalues and vector spaces. The lectures are accompanied by problem and solutions sets.

Deutsch, David

2008-03-15

47

Cluster State Quantum Computation.  

National Technical Information Service (NTIS)

This is the final report for the AFRL/RI in-house project Cluster State Quantum Computation. Under this project investigations were conducted which included: (i) the development and characterization of a new multipli- entangled photon source that increase...

G. Lott M. Fanto P. Alsing

2014-01-01

48

Introduction to Quantum Computing  

NSDL National Science Digital Library

This is a short online course in quantum computation. The stated purpose of the course is to communicate the importance of quantum computing, how it works, and the ability to assess the value of new research results. The class features video lectures with slides. The user may either view the slides as an image, or view the video taped lecture in parallel with the slides using RealAudio.

Van Meter, Rod

2005-11-30

49

Towards Quantum Computational Logics  

NASA Astrophysics Data System (ADS)

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.

Ledda, Antonio; Sergioli, Giuseppe

2010-12-01

50

Using Quantum Computers for Quantum Simulation  

NASA Astrophysics Data System (ADS)

Numerical simulation of quantum systems is crucial to further our understanding of natural phenomena. Many systems of key interest and importance, in areas such as superconducting materials and quantum chemistry, are thought to be described by models which we cannot solve with sufficient accuracy, neither analytically nor numerically with classical computers. Using a quantum computer to simulate such quantum systems has been viewed as a key application of quantum computation from the very beginning of the field in the 1980s. Moreover, useful results beyond the reach of classical computation are expected to be accessible with fewer than a hundred qubits, making quantum simulation potentially one of the earliest practical applications of quantum computers. In this paper we survey the theoretical and experimental development of quantum simulation using quantum computers, from the first ideas to the intense research efforts currently underway.

Brown, Katherine L.; Munro, William J.; Kendon, Vivien M.

2010-11-01

51

Quantum computational webs  

SciTech Connect

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.

Gross, D. [Institute for Theoretical Physics, Leibniz University Hannover, D-30167 Hannover (Germany); Eisert, J. [Institute for Physics and Astronomy, University of Potsdam, D-14476 Potsdam (Germany); Institute for Advanced Study Berlin, D-14193 Berlin (Germany)

2010-10-15

52

Quantum Computation and Spin Electronics  

Microsoft Academic Search

In this chapter we explore the connection between mesoscopic physics and quantum computing. After giving a bibliography providing a general introduction to the subject of quantum information processing, we review the various approaches that are being considered for the experimental implementation of quantum computing and quantum communication in atomic physics, quantum optics, nuclear magnetic resonance, superconductivity, and, especially, normal-electron solid

D. P. DiVincenzo; G. Burkard; D. Loss; E. V. Sukhorukov

1999-01-01

53

Short Introduction to Quantum Computation.  

National Technical Information Service (NTIS)

This paper presents a quantum lattice gas method useful for nano- scale computing and quantum computing. There are several important issues that arise when one considers fabricating nano-scale computing devices, and these issues are different depending on...

J. Yepez

1996-01-01

54

Fault-Tolerant Quantum Computation  

Microsoft Academic Search

It has recently been realized that use of the properties of quantum mechanics might speed up certain compu- tations dramatically. Interest in quantum computation has since been growing. One of the main difficulties in realizing quantum computation is that decoherence tends to destroy the information in a superposition of states in a quantum computer, making long compu- tations impossible. A

Peter W. Shor

1996-01-01

55

Quantum discord in quantum computation  

Microsoft Academic Search

Quantum discord is a measure of the quantumness of correlations. After reviewing its different versions and properties, we apply it to the questions of quantum information processing. First we show that changes in discord in the processed unentangled states indicate the need for entanglement in the distributed implementation of quantum gates. On the other hand, it was shown that zero

Aharon Brodutch; Alexei Gilchrist; Daniel R. Terno; Christopher J. Wood

2011-01-01

56

Photonic quantum technologies  

NASA Astrophysics Data System (ADS)

Of the approaches to quantum computing [1], photons are appealing for their low-noise properties and ease of manipulation [2], and relevance to other quantum technologies [3], including communication, metrology [4] and measurement [5]. 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 [11], demonstrating Shor's algorithm with consecutive CNOT gates [12] and the iterative phase estimation algorithm [13]. We have shown how quantum circuits can be reconfigured, using thermo-optic phase shifters to realise a highly reconfigurable quantum circuit [14], and electro-optic phase shifters in lithium niobate to rapidly manipulate the path and polarisation of telecomm wavelength single photons [15]. We have addressed miniaturisation using multimode interference architectures to directly implement NxN Hadamard operations [16], and by using high refractive index contrast materials such as SiOxNy, in which we have implemented quantum walks of correlated photons [17], and Si, in which we have demonstrated generation of orbital angular momentum states of light [18]. We have incorporated microfluidic channels for the delivery of samples to measure the concentration of a blood protein with entangled states of light [19]. We have begun to address the integration of superconducting single photon detectors [20] and diamond [21,22] and non-linear [23,24] 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 [25].[4pt] [1] TD Ladd, et al Nature 464, 45 (2010) [2] JL O'Brien, Science 318, 1567 (2007) [3] JL O'Brien, A Furusawa, J Vuckovic Nature Photon. 3, 687 (2009 [4] T Nagata, et al Science 316, 726 (2007) [5] R Okamoto, et al Science 323, 483 (2009) [6] A Politi, et al Science 320, 646 (2008). [7] A Laing, et al Appl. Phys. Lett. 97, 211109 (2010) [8] JCF Matthews, et al Nature Photon. 3, 346 (2009) [9] A Politi, et al Science 325, 1221 (2009) [10] JCF Matthews, et al Phys. Rev. Lett. 107, 163602 (2011) [11] X-Q Zhou, et al Nature Comm. 2 413 2011 [12] E Mart'in-López, et al Nature Photon. 6, 773 (2012) [13] X-Q Zhou, et al arXiv:1110.4276 [14] PJ Shadbolt, et al Nature Photon. 6, 45 (2012). [15] D. Bonneau, et al. Phys. Rev. Lett., 108, 053601 (2012) [16] A Peruzzo, et al Nature Comm. 2, 224 (2011) [17] A Peruzzo, et al Science 329, 1500 (2010) [18] X Cai, et al Science 338, 363 (2012) [19] A Crespi, et al Appl. Phys. Lett. 100, 233704 (2012) [20] CM Natarajan, et al Appl. Phys. Lett. 96, 211101 (2010) [21] JP Hadden, et al Appl. Phys. Lett. 97, 241901 (2010) [22] L Marseglia, et al Appl. Phys. Lett. 98, 133107 (2011) [23] C. Xiong, et al. Appl. Phys. Lett. 98, 051101 (2011) [24] M. Lobino, et al, Appl. Phys. Lett. 99, 081110 (2011) [25] E. Engin, et al. arXiv:1204.4922 [25] A. Peruzzo, et al Science 338, 634 (2012)

O'Brien, Jeremy

2013-03-01

57

Blind topological measurement-based quantum computation.  

PubMed

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

Morimae, Tomoyuki; Fujii, Keisuke

2012-01-01

58

Oracle Quantum Computing  

Microsoft Academic Search

Building on the work of Deutsch and Jozsa, we construct oracles relative to which (1) there is a decision problem that can be solved with certainty in worst-case polynomial time on the quantum computer, yet it cannot be solved classically in probabilistic expected polynomial time if errors are not tolerated, nor even in nondeterministic polynomial time, and (2) there is

André Berthiaume; Gilles Brassard

1994-01-01

59

On Quantum Neural Computing  

Microsoft Academic Search

This paper examines the notion of quantum neural computing in thecontext of several new directions in neural network research. In particular,we consider new neuron and network models that lead to rapidtraining; chaotic dynamics in neuron assemblies; models of attention andawareness; cytoskeletal microtubule information processing; and quantummodels. Recent discoveries in neuroscience that cannot be placed in the reductionistmodels of biological information

Subhash C. Kak

1995-01-01

60

Secure Quantum Technologies  

NASA Astrophysics Data System (ADS)

Over the past three decades, quantum mechanics has allowed the development of technologies that provide unconditionally secure communication. In parallel, the quantum nature of the transverse electromagnetic field has spawned the field of quantum imaging that encompasses technologies such as quantum lithography, quantum ghost imaging, and high-dimensional quantum key distribution (QKD). The emergence of such quantum technologies also highlights the need for the development of accurate and efficient methods of measuring and characterizing the elusive quantum state itself. In this thesis, I present new technologies that use the quantum properties of light for security. The first of these is a technique that extends the principles behind QKD to the field of imaging and optical ranging. By applying the polarization-based BB84 protocol to individual photons in an active imaging system, we obtained images that were secure against any intercept-resend jamming attacks. The second technology presented in this thesis is based on an extension of quantum ghost imaging, a technique that uses position-momentum entangled photons to create an image of an object without directly gaining any spatial information from it. We used a holographic filtering technique to build a quantum ghost image identification system that uses a few pairs of photons to identify an object from a set of known objects. The third technology addressed in this thesis is a high-dimensional QKD system that uses orbital-angular-momentum (OAM) modes of light for encoding. Moving to a high-dimensional state space in QKD allows one to impress more information on each photon, as well as introduce higher levels of security. I discuss the development of two OAM-QKD protocols based on the BB84 and Ekert protocols of QKD. In addition, I present a study characterizing the effects of turbulence on a communication system using OAM modes for encoding. The fourth and final technology presented in this thesis is a relatively new technique called direct measurement that uses sequential weak and strong measurements to characterize a quantum state. I use this technique to characterize the quantum state of a photon with a dimensionality of d = 27, and visualize its rotation in the natural basis of OAM.

Malik, Mehul

61

Adiabatic Quantum Computation is Equivalent to Standard Quantum Computation  

Microsoft Academic Search

Adiabatic quantum computation has recently attracted attention in the physics and computer science communities, but its computational power has been unknown. We settle this question and describe an efficient adiabatic simulation of any given quantum algorit hm, which implies that the adiabatic com- putation model and the conventional quantum circuit model are polynomially equivalent. Our result can be extended to

Dorit Aharonov; Wim Van Dam; Julia Kempe; Zeph Landau; Seth Lloyd; Oded Regev

2004-01-01

62

Helping Students Learn Quantum Mechanics for Quantum Computing  

NASA Astrophysics Data System (ADS)

Quantum information science and technology is a rapidly growing interdisciplinary field drawing researchers from science and engineering fields. Traditional instruction in quantum mechanics is insufficient to prepare students for research in quantum computing because there is a lack of emphasis in the current curriculum on quantum formalism and dynamics. We are investigating the difficulties students have with quantum mechanics and are developing and evaluating quantum interactive learning tutorials (QuILTs) to reduce the difficulties. Our investigation includes interviews with individual students and the development and administration of free-response and multiple-choice tests. We discuss the implications of our research and development project on helping students learn quantum mechanics relevant for quantum computing.

Singh, Chandralekha

2007-01-01

63

Quantum discord in quantum computation  

Microsoft Academic Search

Quantum discord is a measure of the quantumness of correlations. After\\u000areviewing its different versions and properties, we apply it to the questions\\u000aof quantum information processing. First we show that changes in discord in the\\u000aprocessed unentangled states indicate the need for entanglement in the\\u000adistributed implementation of quantum gates. On the other hand, it was shown\\u000athat zero

Aharon Brodutch; Alexei Gilchrist; Daniel R. Terno; Christopher J. Wood

2010-01-01

64

Hybrid quantum computation  

NASA Astrophysics Data System (ADS)

We present a hybrid model of the unitary-evolution-based quantum computation model and the measurement-based quantum computation model. In the hybrid model, part of a quantum circuit is simulated by unitary evolution and the rest by measurements on star graph states, thereby combining the advantages of the two standard quantum computation models. In the hybrid model, a complicated unitary gate under simulation is decomposed in terms of a sequence of single-qubit operations, the controlled-z gates, and multiqubit rotations around the z axis. Every single-qubit and the controlled-z gate are realized by a respective unitary evolution, and every multiqubit rotation is executed by a single measurement on a required star graph state. The classical information processing in our model requires only an information flow vector and propagation matrices. We provide the implementation of multicontrol gates in the hybrid model. They are very useful for implementing Grover’s search algorithm, which is studied as an illustrative example.

Sehrawat, Arun; Zemann, Daniel; Englert, Berthold-Georg

2011-02-01

65

Hybrid quantum computation  

SciTech Connect

We present a hybrid model of the unitary-evolution-based quantum computation model and the measurement-based quantum computation model. In the hybrid model, part of a quantum circuit is simulated by unitary evolution and the rest by measurements on star graph states, thereby combining the advantages of the two standard quantum computation models. In the hybrid model, a complicated unitary gate under simulation is decomposed in terms of a sequence of single-qubit operations, the controlled-z gates, and multiqubit rotations around the z axis. Every single-qubit and the controlled-z gate are realized by a respective unitary evolution, and every multiqubit rotation is executed by a single measurement on a required star graph state. The classical information processing in our model requires only an information flow vector and propagation matrices. We provide the implementation of multicontrol gates in the hybrid model. They are very useful for implementing Grover's search algorithm, which is studied as an illustrative example.

Sehrawat, Arun; Englert, Berthold-Georg [Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543 Singapore (Singapore); Department of Physics, National University of Singapore, 2 Science Drive 3, 117542 Singapore (Singapore); Zemann, Daniel [Institut fuer Quantenoptik und Quanteninformation, Technikerstrasse 21a, A-6020 Innsbruck (Austria)

2011-02-15

66

Quantum computers: Definition and implementations  

SciTech Connect

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.

Perez-Delgado, Carlos A.; Kok, Pieter [Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield, S3 7RH (United Kingdom)

2011-01-15

67

Quantum computers: Definition and implementations  

NASA Astrophysics Data System (ADS)

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.

Pérez-Delgado, Carlos A.; Kok, Pieter

2011-01-01

68

Relativistic quantum chemistry on quantum computers  

NASA Astrophysics Data System (ADS)

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 Schrödinger 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.

Veis, Libor; Viš?ák, Jakub; Fleig, Timo; Knecht, Stefan; Saue, Trond; Visscher, Lucas; Pittner, Ji?í

2012-03-01

69

Quantum cellular automaton for universal quantum computation  

SciTech Connect

This paper describes a quantum cellular automaton capable of performing universal quantum computation. The automaton has an elementary transition function that acts on Margolus cells of 2x2 qubits, and both the 'quantum input' and the program are encoded in the initial state of the system.

Raussendorf, Robert [Institute for Quantum Information, California Institute of Technology, Pasadena, California 91125 (United States)

2005-08-15

70

Quantum computation vs. firewalls  

NASA Astrophysics Data System (ADS)

In this paper we discuss quantum computational restrictions on the types of thought experiments recently used by Almheiri, Marolf, Polchinski, and Sully to argue against the smoothness of black hole horizons. We argue that the quantum computations required to do these experiments would take a time which is exponential in the entropy of the black hole under study, and we show that for a wide variety of black holes this prevents the experiments from being done. We interpret our results as motivating a broader type of nonlocality than is usually considered in the context of black hole thought experiments, and claim that once this type of nonlocality is allowed there may be no need for firewalls. Our results do not threaten the unitarity of black hole evaporation or the ability of advanced civilizations to test it.

Harlow, Daniel; Hayden, Patrick

2013-06-01

71

Topological quantum computation  

Microsoft Academic Search

The theory of quantum computation can be constructed from the abstract study\\u000aof anyonic systems. In mathematical terms, these are unitary topological\\u000amodular functors. They underlie the Jones polynomial and arise in\\u000aWitten-Chern-Simons theory. The braiding and fusion of anyonic excitations in\\u000aquantum Hall electron liquids and 2D-magnets are modeled by modular functors,\\u000aopening a new possibility for the realization

Michael H. Freedman; Alexei Kitaev; Michael J. Larsen; Zhenghan Wang; L. D. Landau; Michael H. Freedman

2002-01-01

72

Quantum Gravity on a Quantum Computer?  

NASA Astrophysics Data System (ADS)

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.

Kempf, Achim

2014-05-01

73

Quantum walks, quantum gates, and quantum computers  

SciTech Connect

The physics of quantum walks on graphs is formulated in Hamiltonian language, both for simple quantum walks and for composite walks, where extra discrete degrees of freedom live at each node of the graph. It is shown how to map between quantum walk Hamiltonians and Hamiltonians for qubit systems and quantum circuits; this is done for both single-excitation and multiexcitation encodings. Specific examples of spin chains, as well as static and dynamic systems of qubits, are mapped to quantum walks, and walks on hyperlattices and hypercubes are mapped to various gate systems. We also show how to map a quantum circuit performing the quantum Fourier transform, the key element of Shor's algorithm, to a quantum walk system doing the same. The results herein are an essential preliminary to a Hamiltonian formulation of quantum walks in which coupling to a dynamic quantum environment is included.

Hines, Andrew P. [Pacific Institute of Theoretical Physics and Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, British Columbia, V6T 1Z1 (Canada); Pacific Institute for the Mathematical Sciences, 1933 West Mall, University of British Columbia, Vancouver, British Columbia, V6T 1Z2 (Canada); Stamp, P. C. E. [Pacific Institute of Theoretical Physics and Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, British Columbia, V6T 1Z1 (Canada)

2007-06-15

74

Triple-server blind quantum computation using entanglement swapping  

NASA Astrophysics Data System (ADS)

Blind quantum computation allows a client who does not have enough quantum resources or technologies to achieve quantum computation on a remote quantum server such that the client's input, output, and algorithm remain unknown to the server. Up to now, single- and double-server blind quantum computation have been considered. In this work, we propose a triple-server blind computation protocol where the client can delegate quantum computation to three quantum servers by the use of entanglement swapping. Furthermore, the three quantum servers can communicate with each other and the client is almost classical since one does not require any quantum computational power, quantum memory, and the ability to prepare any quantum states and only needs to be capable of getting access to quantum channels.

Li, Qin; Chan, Wai Hong; Wu, Chunhui; Wen, Zhonghua

2014-04-01

75

Quantum computing on encrypted data.  

PubMed

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

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

2014-01-01

76

Fast Quantum Computing with Buckyballs  

Microsoft Academic Search

We have found that encapsulated atoms in fullerene molecules, which carry a spin, can be used for fast quantum computing. We describe the scheme for performing quantum computations, going through the preparation of the qubit state and the realization of a two-qubit quantum gate. When we apply a static magnetic field to each encased spin, we find out the ideal

Maria Silvia Garelli; Feodor V Kusmartsev

2005-01-01

77

Quantum computing with defects  

PubMed Central

Identifying and designing physical systems for use as qubits, the basic units of quantum information, are critical steps in the development of a quantum computer. Among the possibilities in the solid state, a defect in diamond known as the nitrogen-vacancy (NV-1) center stands out for its robustness—its quantum state can be initialized, manipulated, and measured with high fidelity at room temperature. Here we describe how to systematically identify other deep center defects with similar quantum-mechanical properties. We present a list of physical criteria that these centers and their hosts should meet and explain how these requirements can be used in conjunction with electronic structure theory to intelligently sort through candidate defect systems. To illustrate these points in detail, we compare electronic structure calculations of the NV-1 center in diamond with those of several deep centers in 4H silicon carbide (SiC). We then discuss the proposed criteria for similar defects in other tetrahedrally coordinated semiconductors.

Weber, J. R.; Koehl, W. F.; Varley, J. B.; Janotti, A.; Buckley, B. B.; Van de Walle, C. G.; Awschalom, D. D.

2010-01-01

78

Quantum Information and Computation (QUIC).  

National Technical Information Service (NTIS)

A broad, multidisciplinary program has been pursued in the area of quantum computation and information. Principal accomplishments include an experiment to localize atoms within a high quality factor optical cavity for the implementation of quantum logic a...

H. J. Kimble J. Preskill S. Lloyd A. Despain

2001-01-01

79

Quantum computations on a topologically encoded qubit.  

PubMed

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

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

2014-07-18

80

Quantum Computation of Fluid Dynamics  

Microsoft Academic Search

Presented is a quantum lattice gas for Navier-Stokes fluid dynamicssimulation. The quantum lattice-gas transport equation at the microscopicscale is presented as a generalization of the classical lattice-gastransport equation. A special type of quantum computer network is proposedthat is suitable for implementing the quantum lattice gas. Thequantum computer network undergoes a partial collapse of the wavefunctionat every time step of the

Jeffrey Yepez

1998-01-01

81

Conservative quantum computing.  

PubMed

The Wigner-Araki-Yanase theorem shows that conservation laws limit the accuracy of measurement. Here, we generalize the argument to show that conservation laws limit the accuracy of quantum logic operations. A rigorous lower bound is obtained of the error probability of any physical realization of the controlled-NOT gate under the constraint that the computational basis is represented by a component of spin, and that physical implementations obey the angular momentum conservation law. The lower bound is shown to be inversely proportional to the number of ancilla qubits or the strength of the external control field. PMID:12144465

Ozawa, Masanao

2002-07-29

82

Quantum Computation Using Optically Coupled Quantum Dot Arrays  

NASA Technical Reports Server (NTRS)

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.

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

1998-01-01

83

A potentially realizable quantum computer.  

PubMed

Arrays of weakly coupled quantum systems might compute if subjected to a sequence of electromagnetic pulses of well-defined frequency and length. Such pulsed arrays are true quantum computers: Bits can be placed in superpositionsof 0 and 1, logical operations take place coherently, and dissipation is required only for error correction. Operated with frequent error correction, such a system functions as a parallel digital computer. Operated in a quantum-mechanically coherent manner, such a device functions as a generalpurpose quantum-mechanical micromanipulator, capable of both creating any desired quantum state of the array and transforming that state in any desired way. PMID:17798117

Lloyd, S

1993-09-17

84

Interfacing External Quantum Devices to a Universal Quantum Computer  

PubMed Central

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.

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

2011-01-01

85

Interfacing external quantum devices to a universal quantum computer.  

PubMed

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

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

2011-01-01

86

Universal quantum computation by discontinuous quantum walk  

SciTech Connect

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.

Underwood, Michael S.; Feder, David L. [Institute for Quantum Information Science, University of Calgary, Calgary, Alberta T2N 1N4 (Canada)

2010-10-15

87

Universal quantum computer from a quantum magnet  

NASA Astrophysics Data System (ADS)

We show that a local Hamiltonian of spin-(3)/(2) particles with only two-body nearest-neighbor Affleck-Kennedy-Lieb-Tasaki and exchange-type interactions has a unique ground state, which can be used to implement universal quantum computation merely with single-spin measurements. We prove that the Hamiltonian is gapped, independent of the system size. Our result provides a further step toward utilizing systems with condensed-matter-type interactions for measurement-based quantum computation.

Cai, Jianming; Miyake, Akimasa; Dür, Wolfgang; Briegel, Hans J.

2010-11-01

88

Simulating Chemistry Using Quantum Computers  

NASA Astrophysics Data System (ADS)

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.

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

2011-05-01

89

OPTIMIZING COMPUTER TECHNOLOGY INTEGRATION  

Microsoft Academic Search

The purpose of this study was to better utiderstatid what optimal computer techtiol- ogy ititegration looks like in adult basic skills education (ABSE). One question guided the research: How is computer technology integration best conceptualized and measured? The study used the Delphi method to map the cotistruct of computer technology integratioti and required qualitative analysis of expert opinion, gathered in

Elizabeth Dillon-Marable; Thomas Valentine

2006-01-01

90

Quantum Computational Logics. A Survey  

Microsoft Academic Search

Quantum computation has suggested new forms of quantum logic, called quantum\\u000acomputational logics. The basic semantic idea is the following: the meaning of\\u000aa sentence is identified with a quregister, a system of qubits, representing a\\u000apossible pure state of a compound quantum system. The generalization to mixed\\u000astates, which might be useful to analyse entanglement-phenomena, is due to\\u000aGudder.

MARIA LUISA DALLA CHIARA; ROBERTO GIUNTINI

2003-01-01

91

A potentially realizable quantum computer  

Microsoft Academic Search

Arrays of weakly coupled quantum systems might compute if subjected to a sequence of electromagnetic pulses of well-defined frequency and length. Such pulsed arrays are true quantum computers: bits can be placed in superpositions of 0 and 1, logical operations take place coherently, and dissipation is required only for error correction. Operated with frequent error correction, such a system functions

Seth Lloyd

1993-01-01

92

Semiconductor Spintronics for Quantum Computation  

Microsoft Academic Search

Encoding quantum information in spins embedded in semiconductors (electronic, ionic, or nuclear) offers several potential\\u000a approaches towards solid-state quantum computation. Electronic spin transport, persistence and manipulation in nonmagnetic\\u000a semiconductor materials, as well as the interaction of electronic spins with optics, are the fundamental properties reviewed\\u000a here. The presentation focuses on the material properties important for implementing quantum computation, and on

M. Flatté

93

Quantum Computing and High Performance Computing.  

National Technical Information Service (NTIS)

GE Global Research has enhanced a previously developed general- purpose quantum computer simulator, improving its efficiency and increasing its functionality. Matrix multiplication operations in the simulator were optimized by taking advantage of the part...

K. S. Aggour R. M. Mattheyses J. Shultz B. H. Allen M. Lapinski

2006-01-01

94

Programmable architecture for quantum computing  

NASA Astrophysics Data System (ADS)

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.

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

2013-08-01

95

Braid topologies for quantum computation.  

PubMed

In topological quantum computation, quantum information is stored in states which are intrinsically protected from decoherence, and quantum gates are carried out by dragging particlelike excitations (quasiparticles) around one another in two space dimensions. The resulting quasiparticle trajectories define world lines in three-dimensional space-time, and the corresponding quantum gates depend only on the topology of the braids formed by these world lines. We show how to find braids that yield a universal set of quantum gates for qubits encoded using a specific kind of quasiparticle which is particularly promising for experimental realization. PMID:16241636

Bonesteel, N E; Hormozi, L; Zikos, G; Simon, S H

2005-09-30

96

Insecurity of quantum secure computations  

NASA Astrophysics Data System (ADS)

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.

Lo, Hoi-Kwong

1997-08-01

97

Computational Power of Quantum Machines, Quantum Grammars and Feasible Computation  

NASA Astrophysics Data System (ADS)

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.

Krishnamurthy, E. V.

98

Simulation of electronic structure Hamiltonians using quantum computers  

NASA Astrophysics Data System (ADS)

Over the last century, a large number of physical and mathematical developments paired with rapidly advancing technology have allowed the field of quantum chemistry to advance dramatically. However, the lack of computationally efficient methods for the exact simulation of quantum systems on classical computers presents a limitation of current computational approaches. We report, in detail, how a set of pre-computed molecular integrals can be used to explicitly create a quantum circuit, i.e. a sequence of elementary quantum operations, that, when run on a quantum computer, to obtain the energy of a molecular system with fixed nuclear geometry using the quantum phase estimation algorithm. We extend several known results related to this idea and discuss the adiabatic state preparation procedure for preparing the input states used in the algorithm. With current and near future quantum devices in mind, we provide a complete example using the hydrogen molecule, of how a chemical Hamiltonian can be simulated using a quantum computer.

Whitfield, James; Biamonte, Jacob; Aspuru-Guzik, Alan

2011-03-01

99

Lattice-Gas Quantum Computation  

Microsoft Academic Search

We present a quantum lattice-gas model for a quantum computer operating with continual wavefunction collapse; entanglement of the wavefunction occurs locally over small spatial regions between nearby qubits for only a short time period. The quantum lattice-gas is a noiseless method that directly models the lattice-gas particle dynamics at the mesoscopic scale. The system behaves like a viscous Navier-Stokes fluid.

Jeffrey Yepez

1998-01-01

100

Surfing Electrons in Quantum Computers?  

NASA Astrophysics Data System (ADS)

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.

Pomeau, Y.

101

Using computer algebra in quantum computation and quantum games  

NASA Astrophysics Data System (ADS)

Research in contemporary physics is emphasizing the development and evolution of computer systems to facilitate the calculations. Quantum computing is a branch of modern physics is believed promising results for the future, Thanks to the ability of qubits to store more information than a bit. The work of this paper focuses on the simulation of certain quantum algorithms such as the prisoner's dilemma in its quantum version using the MATHEMATICA® software and implementing stochastic version of the software MAPLE ® and the Grover search algorithm that simulates finding a needle in a haystack.

Bolívar, David A.

2011-05-01

102

Quantum Computation for Physical Modeling.  

National Technical Information Service (NTIS)

One of the most famous American physicists of the twentieth century, Richard Feynman, in 1982 was the first to propose using a quantum mechanical computing device to efficiently simulate quantum mechanical many-body dynamics 1, 2, 3, a task that is expone...

J. Yepez

2002-01-01

103

Complexity limitations on quantum computation  

Microsoft Academic Search

We use the powerful tools of counting complexity and generic oracles to help understand the lim- itations of the complexity of quantum computation. We show several results for the probabilistic quantum class BQP. BQP is low for PP, i.e., PPBQP = PP. There exists a relativized world where P = BQP and the polynomial-time hierarchy is innite. There exists a

Lance Fortnow; J. Rogers

1997-01-01

104

Experimental one-way quantum computing  

Microsoft Academic Search

Standard quantum computation is based on sequences of unitary quantum logic gates that process qubits. The one-way quantum computer proposed by Raussendorf and Briegel is entirely different. It has changed our understanding of the requirements for quantum computation and more generally how we think about quantum physics. This new model requires qubits to be initialized in a highly entangled cluster

P. Walther; K. J. Resch; T. Rudolph; E. Schenck; H. Weinfurter; V. Vedral; M. Aspelmeyer; A. Zeilinger

2005-01-01

105

The quantum field as a quantum computer  

NASA Astrophysics Data System (ADS)

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 2 a 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.

D'Ariano, Giacomo Mauro

2012-01-01

106

Challenges for Quantum Computing with Solid-State Devices  

Microsoft Academic Search

Quantum computing has attracted considerable interest in the past decade as a possible way to deal with certain intractable problems of conventional digital computing. Quantum computers built using the versatile methods of solid-state technology are attractive because the many thousands of devices needed for such a computer could be fabricated with well-established technologies. However, the imperfections of solid-state devices constructed

Robert W. Keyes

2005-01-01

107

Accelerating commutation circuits in quantum computer networks  

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

108

Electron spins in quantum dots for spintronics and quantum computation  

Microsoft Academic Search

Coherent manipulation, filtering, and measurement of electronic spin in quantum dots and other nanostructures have promising applications in conventional and in quantum information processing and transmission. We present an overview of our theoretical proposal to implement a quantum computer using electron spins in quantum dots as qubits. We discuss all necessary requirements towards a scalable quantum computer including one- and

Hans-Andreas Engel; Patrik Recher; Daniel Loss

2001-01-01

109

Quantum computing with quantum-dot cellular automata  

Microsoft Academic Search

Quantum-dot cellular automata (QCA), arrays of coupled quantum-dot devices, are proposed for quantum computing. The notion of coherent QCA (CQCA) is introduced in order to distinguish QCA applied to quantum computing from classical digital QCA. Information is encoded in the spatial state of the electrons in the multidot system. A line of CQCA cells can work as a quantum register.

Géza Tóth; Craig S. Lent

2001-01-01

110

Biophysics: Green quantum computers  

NASA Astrophysics Data System (ADS)

In photosynthesis, the Sun's energy is harvested and converted into biomass, greening the planet. Evidence is growing that quantum mechanics plays a part in that process. But exactly how, and why, remains to be explored.

Scholes, Gregory D.

2010-06-01

111

Reversible logic and quantum computers  

Microsoft Academic Search

This article is concerned with the construction of a quantum-mechanical Hamiltonian describing a computer. This Hamiltonian generates a dynamical evolution which mimics a sequence of elementary logical steps. This can be achieved if each logical step is locally reversible (global reversibility is insufficient). Computational errors due to noise can be corrected by means of redundancy. In particular, reversible error-correcting codes

Asher Peres

1985-01-01

112

Quantum Computers, Factoring and Decoherence  

Microsoft Academic Search

In a quantum computer any superposition of inputs evolves unitarily into the correspond- ing superposition of outputs. It has been recently demonstrated that such computers can dramatically speed up the task of finding factors of large numbers - a problem of great practical significance because of its cryptographic applications. Instead of the nearly ex- ponential (? exp L1\\/3, for a

I. L. Chuang; R. Laflamme; P. Shor; W. H. Zurek

1995-01-01

113

A Quantum Jump in Computer Science  

Microsoft Academic Search

Classical and quantum information are very different. Together they can perform feats that neither could achieve alone. These include quantum computing, quantum cryptography and quantum teleportation. This paper surveys some of the most striking new applications of quantum mechanics to computer science. Some of these applications are still theoretical but others have been implemented.

Gilles Brassard

1995-01-01

114

Pfaffian States: Quantum Computation  

NASA Astrophysics Data System (ADS)

The Pfaffian determinant is sometimes used to multiply the Laughlin's wave function at the half filled Landau level. The square of the Pfaffian gives the ordinary determinant. We find that the Pfaffian wave function leads to four times larger energies and two times faster time. By the same logic, the Pfaffian breaks the supersymmetry of the Dirac equation. By using the spin properties and the Landau levels, we correctly interpret the state with 5/2 filling. The quantum numbers which represent the state vectors are now products of n (Landau level quantum number), l(orbital angular momentum quantum number and the spin, s |n, l, s>. In a circuit, the noise measures the resistivity and hence the charge. The Pfaffian velocity is different from that of the single-particle states and hence it has important consequences in the measurement of the charge of the quasiparticles.

Shrivastava, Keshav N.

2009-09-01

115

Rapid Solution of Problems by Quantum Computation  

Microsoft Academic Search

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

David Deutsch; Richard Jozsa

1992-01-01

116

Quantum technology and its applications  

SciTech Connect

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.

Boshier, Malcolm [Los Alamos National Laboratory; Berkeland, Dana [USG; Govindan, Tr [ARO; Abo - Shaeer, Jamil [DARPA

2010-12-10

117

Strengths and Weaknesses of Quantum Computing  

Microsoft Academic Search

Recently a great deal of attention has focused on quantum computation following a sequence of results suggesting that quantum computers are more powerful than classical probabilistic computers. Following Shor's result that factoring and the extraction of discrete logarithms are both solvable in quantum polynomial time, it is natural to ask whether all of NP can be efficiently solved in quantum

Charles H. Bennett; Ethan Bernstein; Gilles Brassard; Umesh V. Vazirani

1997-01-01

118

Estimating the efficiency of ensemble quantum computing  

NASA Astrophysics Data System (ADS)

A straightforward method to estimate the efficiency of ensemble quantum computing using nuclear magnetic resonance spectroscopy is presented by defining a quantum computing efficiency factor (QC ?). This method allows critical evaluation of the performance of quantum gates and algorithms and provides a way to design efficient quantum computer.

Krishnan, V. V.

2001-11-01

119

Computer Technology for Industry  

NASA Technical Reports Server (NTRS)

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.

1979-01-01

120

Maintaining coherence in quantum computers  

Microsoft Academic Search

The effect of the inevitable coupling to external degrees of freedom of a\\u000aquantum computer are examined. It is found that for quantum calculations (in\\u000awhich the maintenance of coherence over a large number of states is important),\\u000anot only must the coupling be small but the time taken in the quantum\\u000acalculation must be less than the thermal time

W. G. Unruh

1995-01-01

121

Raman-Controlled Quantum Dots for Quantum Computing.  

National Technical Information Service (NTIS)

Optical control is fundamental to our project objective of demonstration of key quantum operations for quantum computation with spin qubits of electrons in semiconductor quantum dots. Sophia Economou, the graduate student supported by this fellowship, wor...

L. J. Sham

2005-01-01

122

Verification for measurement-only blind quantum computing  

NASA Astrophysics Data System (ADS)

Blind quantum computing is a new secure quantum computing protocol where a client who does not have any sophisticated quantum technology can delegate her quantum computing to a server without leaking any privacy. It is known that a client who has only a measurement device can perform blind quantum computing [T. Morimae and K. Fujii, Phys. Rev. A 87, 050301(R) (2013), 10.1103/PhysRevA.87.050301]. It has been an open problem whether the protocol can enjoy the verification, i.e., the ability of the client to check the correctness of the computing. In this paper, we propose a protocol of verification for the measurement-only blind quantum computing.

Morimae, Tomoyuki

2014-06-01

123

The scalable quantum computation based on quantum dot systems  

Microsoft Academic Search

We propose a scheme for realizing the scalable quantum computation based on nonidentical quantum dots trapped in a single-mode waveguide. In this system, the quantum dots simultaneously interact with a large detuned waveguide and classical light fields. During the process, neither the waveguide mode nor the quantum dots are excited, while the sub-system composed of any two quantum dots can

Jian-Qi Zhang; Ya-Fei Yu; Xun-Li Feng; Zhi-Ming Zhang

2011-01-01

124

Models of quantum computation and quantum programming languages  

Microsoft Academic Search

The goal of the presented paper is to provide an introduction to the basic computational models used in quantum information theory. We review various models of quantum Turing machine, quantum circuits and quantum random access machine (QRAM) along with their classical counterparts. We also provide an introduction to quantum programming languages, which are developed using the QRAM model. We review

J. A. Miszczak

2010-01-01

125

Solid State Quantum Computing Using Spin Qubits in Silicon Quantum Dots (QCCM).  

National Technical Information Service (NTIS)

The project goals are to fabricate qubits in quantum dots in Si/SiGe modulation-doped heterostructures, to characterize and understand those structures, and to develop the technology necessary for a Si/SiGe quantum dot quantum computer. The physical qubit...

M. Eriksson M. Friesen M. Lagally R. Joynt S. Coppersmith

2009-01-01

126

From transistor to trapped-ion computers for quantum chemistry  

NASA Astrophysics Data System (ADS)

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.

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

2014-01-01

127

Realizable Hamiltonians for universal adiabatic quantum computers  

NASA Astrophysics Data System (ADS)

It has been established that local lattice spin Hamiltonians can be used for universal adiabatic quantum computation. However, the two-local model Hamiltonians used in these proofs are general and hence do not limit the types of interactions required between spins. To address this concern, the present paper provides two simple model Hamiltonians that are of practical interest to experimentalists working toward the realization of a universal adiabatic quantum computer. The model Hamiltonians presented are the simplest known quantum-Merlin-Arthur-complete (QMA-complete) two-local Hamiltonians. The two-local Ising model with one-local transverse field which has been realized using an array of technologies, is perhaps the simplest quantum spin model but is unlikely to be universal for adiabatic quantum computation. We demonstrate that this model can be rendered universal and QMA-complete by adding a tunable two-local transverse ?x?x coupling. We also show the universality and QMA-completeness of spin models with only one-local ?z and ?x fields and two-local ?z?x interactions.

Biamonte, Jacob D.; Love, Peter J.

2008-07-01

128

Self-correcting quantum computers  

NASA Astrophysics Data System (ADS)

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.

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

2013-05-01

129

Photonic implementation for the topological cluster-state quantum computer  

NASA Astrophysics Data System (ADS)

An implementation of the topological cluster-state quantum computer is suggested, in which the basic elements are linear optics, measurements, and a two-dimensional array of quantum dots. This overcomes the need for nonlinear devices to create a lattice of entangled photons. Whereas the thresholds found for computational errors are quite satisfactory (above 10-3), the estimates of the minimum efficiencies needed for the detectors and quantum dots are beyond current technology’s reach. This is because we rely heavily on probabilistic entangling gates, which introduces loss into the scheme irrespective of detector and quantum-dot efficiencies.

Herrera-Martí, David A.; Fowler, Austin G.; Jennings, David; Rudolph, Terry

2010-09-01

130

Quantum computation and decision trees  

Microsoft Academic Search

Many interesting computational problems can be reformulated in terms of decision trees. A natural classical algorithm is to then run a random walk on the tree, starting at the root, to see if the tree contains a node n level from the root. We devise a quantum-mechanical algorithm that evolves a state, initially localized at the root, through the tree.

Edward Farhi; Sam Gutmann

1998-01-01

131

Barium Ions for Quantum Computation  

SciTech Connect

Individually trapped {sup 137}Ba{sup +} in an RF Paul trap is proposed as a qubit candidate, and its various benefits are compared to other ionic qubits. We report the current experimental status of using this ion for quantum computation. Future plans and prospects are discussed.

Dietrich, M. R.; Avril, A.; Bowler, R.; Kurz, N.; Salacka, J. S.; Shu, G.; Blinov, B. B. [University of Washington Department of Physics, Seattle, Washington, 98195 (United States)

2009-03-30

132

Computer Science and Technology Publications.  

National Technical Information Service (NTIS)

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 ...

1977-01-01

133

Quantum computation and spin physics (invited)  

SciTech Connect

A brief review is given of the physical implementation of quantum computation within spin systems or other two-state quantum systems. The importance of the controlled-NOT or quantum XOR gate as the fundamental primitive operation of quantum logic is emphasized. Recent developments in the use of quantum entanglement to build error-robust quantum states, and the simplest protocol for quantum error correction, are discussed. {copyright} {ital 1997 American Institute of Physics.}

DiVincenzo, D.P. [IBM Research Division, Thomas J. Watson Research Center, P.O. Box 218, Yorktown Heights, New York 10598 (United States)] [IBM Research Division, Thomas J. Watson Research Center, P.O. Box 218, Yorktown Heights, New York 10598 (United States)

1997-04-01

134

A Quantum Logic Array Microarchitecture: Scalable Quantum Data Movement and Computation  

Microsoft Academic Search

Recent experimental advances have demonstrated technologies capable of supporting scalable quantum computation. A critical next step is how to put those technologies together into a scalable, fault-tolerant system that is also feasible. We propose a Quantum Logic Array (QLA) microarchitecture that forms the foundation of such a system. The QLA focuses on the communication resources necessary to efficiently support fault-tolerant

Tzvetan S. Metodi; Darshan D. Thaker; Andrew W. Cross; Frederic T. Chong; Isaac L. Chuang

2005-01-01

135

Simulating quantum dynamics on a quantum computer  

NASA Astrophysics Data System (ADS)

We explicitly show how to simulate time-dependent sparse Hamiltonian evolution on a quantum computer, with complexity that is close to linear in the evolution time. The complexity also depends on the magnitude of the derivatives of the Hamiltonian. We propose a range of techniques to simulate Hamiltonians with badly behaved derivatives. These include using adaptive time steps, adapting the order of the integrators, and omitting regions about discontinuities. The complexity of the algorithm is quantified by calls to an oracle, which yields information about the Hamiltonian, and accounts for all computational resources. We explicitly determine the number of bits of output that this oracle needs to provide, and show how to efficiently perform the required 1-sparse unitary operations using these bits. We also account for discretization error in the time, as well as accounting for Hamiltonians that are a sum of terms that are sparse in different bases.

Wiebe, Nathan; Berry, Dominic W.; Hřyer, Peter; Sanders, Barry C.

2011-11-01

136

Quantum Physics and the Nature of Computation  

Microsoft Academic Search

\\u000a Quantum physics is a fascinating area from a computational viewpoint. The features that make quantum systems prohibitively\\u000a hard to simulate classically are precisely the aspects exploited by quantum computation to obtain exponential speedups over\\u000a classical computers. In this talk I will survey our current understanding of the power of quantum computers and prospects\\u000a for experimentally realizing them in the near

Umesh V. Vazirani

2005-01-01

137

Innovative quantum technologies for microgravity fundamental physics and biological research  

NASA Technical Reports Server (NTRS)

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.

Kierk, I. K.

2002-01-01

138

Innovative quantum technologies for microgravity fundamental physics and biological research  

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

139

Simulating Quantum Dynamics On A Quantum Computer  

NASA Astrophysics Data System (ADS)

We develop an efficient quantum algorithm for simulating time-dependent Hamiltonian evolution of general input states on a quantum computer. Given conditions on the smoothness of the Hamiltonian, the complexity of the algorithm is close to linear in the evolution time, and therefore is comparable to algorithms for time-independent Hamiltonians. In addition, we show how the complexity can be reduced by optimizing the time steps. The complexity of the algorithm is quantified by calls to an oracle, which yields information about the Hamiltonian, and accounts for all computational resources. In contrast to previous work, which allowed an oracle query to yield an arbitrary number of bits or qubits, we assign a cost for each bit or qubit accessed. This per-bit or per-qubit costing of oracle calls reveals hitherto unnoticed simulation costs. We also account for discretization errors in the time and the representation of the Hamiltonian. We generalize the requirement of sparse Hamiltonians to being a sum of sparse Hamiltonians in various bases for which the transformation to a sparse Hamiltonian may be performed efficiently.

Wiebe, Nathan; Berry, Dominic; Hoyer, Peter; Sanders, Barry

2011-03-01

140

Computational quantum field theory  

NASA Astrophysics Data System (ADS)

I will give an overview on recent attempts to solve the time-dependent Dirac equation for the electron-positron field operator. These numerical solutions permit a first temporally and spatially resolved insight into the mechanisms of how an electron-positron pair can be created from vacuum in a very strong force field. This approach has helped to illuminate a wide range of controversial questions. Some of these questions arise for complicated physical situations such as how an electron scatters off a supercritical potential barrier (Klein paradox). This requires the application of quantum field theory to study the combined effect of the pair-production due to the supercriticality of the potential together with the scattering at the barrier involving the Pauli-principle. Other phenomena include Schr"odinger's Zitterbewegung and the localization problem for a relativistic particle. This work has been supported by the NSF and Research Corporation. P. Krekora, K. Cooley, Q. Su and R. Grobe, Phys. Rev. Lett. 95, 070403 (2005). P. Krekora, Q. Su and R. Grobe, Phys. Rev. Lett. 93, 043004 (2004). P. Krekora, Q. Su and R. Grobe, Phys. Rev. Lett. 92, 040406 (2004).

Grobe, Rainer

2006-05-01

141

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

SciTech Connect

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.

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

2003-12-01

142

Geometry of Quantum Computation with Qutrits  

PubMed Central

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(3n). As an example, three-qutrit systems are investigated in detail.

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

2013-01-01

143

Ensemble quantum computing by NMR spectroscopy  

PubMed Central

A quantum computer (QC) can operate in parallel on all its possible inputs at once, but the amount of information that can be extracted from the result is limited by the phenomenon of wave function collapse. We present a new computational model, which differs from a QC only in that the result of a measurement is the expectation value of the observable, rather than a random eigenvalue thereof. Such an expectation value QC can solve nondeterministic polynomial-time complete problems in polynomial time. This observation is significant precisely because the computational model can be realized, to a certain extent, by NMR spectroscopy on macroscopic ensembles of quantum spins, namely molecules in a test tube. This is made possible by identifying a manifold of statistical spin states, called pseudo-pure states, the mathematical description of which is isomorphic to that of an isolated spin system. The result is a novel NMR computer that can be programmed much like a QC, but in other respects more closely resembles a DNA computer. Most notably, when applied to intractable combinatorial problems, an NMR computer can use an amount of sample, rather than time, which grows exponentially with the size of the problem. Although NMR computers will be limited by current technology to exhaustive searches over only 15 to 20 bits, searches over as much as 50 bits are in principle possible, and more advanced algorithms could greatly extend the range of applicability of such machines.

Cory, David G.; Fahmy, Amr F.; Havel, Timothy F.

1997-01-01

144

Geometry of discrete quantum computing  

NASA Astrophysics Data System (ADS)

Conventional quantum computing entails a geometry based on the description of an n-qubit state using 2n infinite precision complex numbers denoting a vector in a Hilbert space. Such numbers are in general uncomputable using any real-world resources, and, if we have the idea of physical law as some kind of computational algorithm of the universe, we would be compelled to alter our descriptions of physics to be consistent with computable numbers. Our purpose here is to examine the geometric implications of using finite fields Fp and finite complexified fields \\mathbf {F}_{p^2} (based on primes p congruent to 3 (mod4)) as the basis for computations in a theory of discrete quantum computing, which would therefore become a computable theory. Because the states of a discrete n-qubit system are in principle enumerable, we are able to determine the proportions of entangled and unentangled states. In particular, we extend the Hopf fibration that defines the irreducible state space of conventional continuous n-qubit theories (which is the complex projective space \\mathbf {CP}^{2^{n}-1}) to an analogous discrete geometry in which the Hopf circle for any n is found to be a discrete set of p + 1 points. The tally of unit-length n-qubit states is given, and reduced via the generalized Hopf fibration to \\mathbf {DCP}^{2^{n}-1}, the discrete analogue of the complex projective space, which has p^{2^{n}-1} (p-1)\\,\\prod _{k=1}^{n-1} ( p^{2^{k}}+1) irreducible states. Using a measure of entanglement, the purity, we explore the entanglement features of discrete quantum states and find that the n-qubit states based on the complexified field \\mathbf {F}_{p^2} have pn(p - 1)n unentangled states (the product of the tally for a single qubit) with purity 1, and they have pn + 1(p - 1)(p + 1)n - 1 maximally entangled states with purity zero.

Hanson, Andrew J.; Ortiz, Gerardo; Sabry, Amr; Tai, Yu-Tsung

2013-05-01

145

Multibit gates for quantum computing.  

PubMed

We present a general technique to implement products of many qubit operators communicating via a joint harmonic oscillator degree of freedom in a quantum computer. By conditional displacements and rotations we can implement Hamiltonians which are trigonometric functions of qubit operators. With such operators we can effectively implement higher order gates such as Toffoli gates and C(n)-NOT gates, and we show that the entire Grover search algorithm can be implemented in a direct way. PMID:11329354

Wang, X; Sřrensen, A; Mřlmer, K

2001-04-23

146

All-silicon quantum computer.  

PubMed

A solid-state implementation of a quantum computer composed entirely of silicon is proposed. Qubits are 29Si nuclear spins arranged as chains in a 28Si (spin-0) matrix with Larmor frequencies separated by a large magnetic field gradient. No impurity dopants or electrical contacts are needed. Initialization is accomplished by optical pumping, algorithmic cooling, and pseudo-pure state techniques. Magnetic resonance force microscopy is used for ensemble measurement. PMID:12097071

Ladd, T D; Goldman, J R; Yamaguchi, F; Yamamoto, Y; Abe, E; Itoh, K M

2002-07-01

147

Experimental one-way quantum computing.  

PubMed

Standard quantum computation is based on sequences of unitary quantum logic gates that process qubits. The one-way quantum computer proposed by Raussendorf and Briegel is entirely different. It has changed our understanding of the requirements for quantum computation and more generally how we think about quantum physics. This new model requires qubits to be initialized in a highly entangled cluster state. From this point, the quantum computation proceeds by a sequence of single-qubit measurements with classical feedforward of their outcomes. Because of the essential role of measurement, a one-way quantum computer is irreversible. In the one-way quantum computer, the order and choices of measurements determine the algorithm computed. We have experimentally realized four-qubit cluster states encoded into the polarization state of four photons. We characterize the quantum state fully by implementing experimental four-qubit quantum state tomography. Using this cluster state, we demonstrate the feasibility of one-way quantum computing through a universal set of one- and two-qubit operations. Finally, our implementation of Grover's search algorithm demonstrates that one-way quantum computation is ideally suited for such tasks. PMID:15758991

Walther, P; Resch, K J; Rudolph, T; Schenck, E; Weinfurter, H; Vedral, V; Aspelmeyer, M; Zeilinger, A

2005-03-10

148

Measurement-only topological quantum computation.  

PubMed

We remove the need to physically transport computational anyons around each other from the implementation of computational gates in topological quantum computing. By using an anyonic analog of quantum state teleportation, we show how the braiding transformations used to generate computational gates may be produced through a series of topological charge measurements. PMID:18764095

Bonderson, Parsa; Freedman, Michael; Nayak, Chetan

2008-07-01

149

The Quantum Human Computer (QHC) Hypothesis  

ERIC Educational Resources Information Center

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…

Salmani-Nodoushan, Mohammad Ali

2008-01-01

150

Suppression of quantum chaos in a quantum computer hardware.  

PubMed

We present numerical and analytical studies of a quantum computer proposed by the Yamamoto group in Phys. Rev. Lett. 89, 017901 (2002). The stable and quantum chaos regimes in the quantum computer hardware are identified as a function of magnetic field gradient and dipole-dipole couplings between qubits on a square lattice. It is shown that a strong magnetic field gradient leads to suppression of quantum chaos. PMID:17025526

Lages, J; Shepelyansky, D L

2006-08-01

151

Quantum Computing with Trapped Charged Particles  

Microsoft Academic Search

The concept of quantum computing has no clear cut origin. It emerged from combinations of information theory and quantum mechanical\\u000a concepts. A decisive step was taken by Feynman [414, 415] who considered the possibility of universal simulation, a quantum system which could simulate the physical behavior of any other. Feynman gave arguments which suggested that quantum evolution could be used

Günther Werth; Viorica N. Gheorghe; Fouad G. Major

152

Oxide-semiconductor materials for quantum computing  

Microsoft Academic Search

A scheme for quantum computing is proposed with ferroelectrically coupled Ge\\/Si quantum dots. Ge dots are grown on a Si substrate. A ferroelectric film (STO) is grown to cover the dots. Qubits are electron spins confined in quantum dots. Quantum gating is achieved by manipulating electron interactions across adjacent dots with ferroelectric materials. A low temperature AFM\\/ANSOM microscope is built

Jeremy Levy; N. G. Patil

2002-01-01

153

The case for biological quantum computer elements  

Microsoft Academic Search

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

Wolfgang Baer; Rita Pizzi

2009-01-01

154

Geometry of Quantum Computation with Qudits  

NASA Astrophysics Data System (ADS)

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.

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

2014-02-01

155

Photonic implementation for the topological cluster-state quantum computer  

SciTech Connect

An implementation of the topological cluster-state quantum computer is suggested, in which the basic elements are linear optics, measurements, and a two-dimensional array of quantum dots. This overcomes the need for nonlinear devices to create a lattice of entangled photons. Whereas the thresholds found for computational errors are quite satisfactory (above 10{sup -3}), the estimates of the minimum efficiencies needed for the detectors and quantum dots are beyond current technology's reach. This is because we rely heavily on probabilistic entangling gates, which introduces loss into the scheme irrespective of detector and quantum-dot efficiencies.

Herrera-Marti, David A.; Jennings, David; Rudolph, Terry [Institute for Mathematical Sciences, Imperial College London, London SW7 2BW (United Kingdom); Fowler, Austin G. [Centre for Quantum Computer Technology, University of Melbourne, Victoria (Australia)

2010-09-15

156

Experimental Demonstration of Quantum Lattice Gas Computation  

Microsoft Academic Search

We report an ensemble nuclear magnetic resonance (NMR) implementation of a quantum lattice gas algorithm for the diffusion equation. The algorithm employs an array of quantum information processors sharing classical information, a novel architecture referred to as a type-II quantum computer. This concrete implementa-tion provides a test example from which to probe the strengths and limitations of this new computation

Marco A. Pravia; Zhiying Chen; Jeffrey Yepez; David G. Cory

2003-01-01

157

Experimental Demonstration of Quantum Lattice Gas Computation  

Microsoft Academic Search

We report an ensemble nuclear magnetic resonance (NMR) implementation of a quantum lattice gas algorithm for the diffusion equation. The algorithm employs an array of quantum information processors sharing classical information, a novel architecture referred to as a type-II quantum computer. This concrete implementation provides a test example from which to probe the strengths and limitations of this new computation

Marco A. Pravia; Zhiying Chen; Jeffrey Yepez; David G. Cory

2003-01-01

158

Quantum Computational Logics and Possible Applications  

Microsoft Academic Search

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

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

2008-01-01

159

A One-Way Quantum Computer  

Microsoft Academic Search

We present a scheme of quantum computation that consists entirely of one-qubit measurements on a particular class of entangled states, the cluster states. The measurements are used to imprint a quantum logic circuit on the state, thereby destroying its entanglement at the same time. Cluster states are thus one-way quantum computers and the measurements form the program.

Robert Raussendorf; Hans J. Briegel

2001-01-01

160

Quantum Field Theory and Computational Paradigms  

Microsoft Academic Search

We introduce the basic theory of quantization of radiation field in quantum physics and explain how it relates to the theory of recursive functions in computer science. We outline the basic differences between quantum mechanics (QM) and quantum field theory (QFT) and explain why QFT is better suited for a computational paradigm - based on algorithmic requirement, countably infinite degrees

E. V. Krishnamurthy; Vikram Krishnamurthy

2001-01-01

161

Making weirdness work: quantum information and computation  

Microsoft Academic Search

Information is something that can be encoded in the state of a physical system, and a computation is a task that can be performed with a physically realizable device. Therefore, since the physical world is fundamentally quantum mechanical, the foundations of information theory and computer science should be sought in quantum physics. In fact, quantum information has weird properties that

John Preskill

1998-01-01

162

Making Weirdness Work: Quantum Information and Computation  

Microsoft Academic Search

Information is something that can be encoded in the state of a physical system, and a computation is a task that can be performed with a physically realizable device. Therefore, since the physical world is fundamentally quantum mechanical, the foundations of information theory and computer science should be sought in quantum physics. In fact, quantum information has weird properties that

John Preskill

1988-01-01

163

Geometry, optimal control and quantum computing  

Microsoft Academic Search

Quantum computation promises solution to problems that are hard to solve by classical computers. The efficient construction of quantum circuits that can solve interesting tasks is a fundamental challenge in the field. Such efficient construction also reduces decoherence losses in physical implementations of quantum algorithms by reducing interaction time with the environment. Therefore, finding time-optimal ways to synthesize unitary transformations

Haidong Yuan

2006-01-01

164

A one-way quantum computer.  

PubMed

We present a scheme of quantum computation that consists entirely of one-qubit measurements on a particular class of entangled states, the cluster states. The measurements are used to imprint a quantum logic circuit on the state, thereby destroying its entanglement at the same time. Cluster states are thus one-way quantum computers and the measurements form the program. PMID:11384453

Raussendorf, R; Briegel, H J

2001-05-28

165

Embracing the quantum limit in silicon computing.  

PubMed

Quantum computers hold the promise of massive performance enhancements across a range of applications, from cryptography and databases to revolutionary scientific simulation tools. Such computers would make use of the same quantum mechanical phenomena that pose limitations on the continued shrinking of conventional information processing devices. Many of the key requirements for quantum computing differ markedly from those of conventional computers. However, silicon, which plays a central part in conventional information processing, has many properties that make it a superb platform around which to build a quantum computer. PMID:22094695

Morton, John J L; McCamey, Dane R; Eriksson, Mark A; Lyon, Stephen A

2011-11-17

166

Multivalued logic gates for quantum computation  

Microsoft Academic Search

We develop a multivalued logic for quantum computing for use in multi-level quantum systems, and discuss the practical advantages of this approach for scaling up a quantum computer. Generalizing the methods of binary quantum logic, we establish that arbitrary unitary operations on any number of d-level systems (d>2) can be decomposed into logic gates that operate on only two systems

Ashok Muthukrishnan; C. R. Stroud Jr.; Jr

2000-01-01

167

Robust Ising gates for practical quantum computation  

SciTech Connect

I describe the use of techniques based on composite rotations to combat systematic errors in controlled phase gates, which form the basis of two-qubit quantum logic gates. Although developed and described within the context of nuclear magnetic resonanace quantum computing these sequences should be applicable to any implementation of quantum computation based on Ising couplings. In combination with existing single-qubit gates this provides a universal set of robust quantum logic gates.

Jones, Jonathan A. [Centre for Quantum Computation, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom)

2003-01-01

168

Scalable Quantum Computers: Paving the Way to Realization  

NASA Astrophysics Data System (ADS)

Quantum computers hold the promise of solving problems that would otherwise be intractable with conventional computers. Some prototypes of the simplest elements needed to build a quantum computer have already been implemented in the laboratory. The efforts now concentrate on combining these elements into scalable systems. In addition, alternative routes to creating large scale quantum computers are continuously being developed. This volume gives a cross-section of recent achievements in both the theory and the practical realization of quantum computing devices. Samuel L. Braunstein (Reader, University of Wales, Bangor, and editor of the book "Quantum Computing - Where do we want to go tomorrow") and Hoi-Kwong Lo (Chief Scientist, MagiQ Technologies, Inc., NY) invited experts across many disciplines involved in the development of quantum computers to review their proposals in a manner accessible to the non-expert. Breaking with tradition, this book not only contains proposals, but a set of independent expert evaluations of these ideas as well. As a by-product this volume facilitates a comparison between the widely varying disciplines covered, including: ion traps, cavity quantum electrodynamics, nuclear magnetic resonance, optical lattices, quantum dots, silicon systems, superconductivity and electrons on helium.

Braunstein, Samuel L.; Lo, Hoi-Kwong

2001-02-01

169

Quantum-dot cellular automata: computing by field polarization  

Microsoft Academic Search

As CMOS technology continues its monotonic shrink, computing with quantum dots remains a goal in nanotechnology research. Quantum-dot cellular automata (QCA) is a paradigm for low-power, high-speed, highly dense computing that could be realized in a variety of materials systems. Discussed here are the basic paradigm of QCA, materials systems in which QCA might be constructed, a series of experiments

Gary H. Bernstein

2003-01-01

170

Solid-state quantum computer based on scanning tunneling microscopy.  

PubMed

We propose a solid-state nuclear-spin quantum computer based on application of scanning tunneling microscopy (STM) and well-developed silicon technology. It requires the measurement of tunneling-current modulation caused by the Larmor precession of a single electron spin. Our envisioned STM quantum computer would operate at the high magnetic field (approximately 10 T) and at low temperature approximately 1 K. PMID:11531599

Berman, G P; Brown, G W; Hawley, M E; Tsifrinovich, V I

2001-08-27

171

Contextuality supplies the `magic' for quantum computation  

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

172

Contextuality supplies the 'magic' for quantum computation.  

PubMed

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

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

2014-06-19

173

Is the brain a quantum computer?  

PubMed

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 instantiation of quantum computation. Third, there is no psychological evidence that such mental phenomena as consciousness and mathematical thinking require explanation via quantum theory. We conclude that understanding brain function is unlikely to require quantum computation or similar mechanisms. PMID:21702826

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

2006-05-01

174

Resilient Quantum Computation: Error Models and Thresholds  

Microsoft Academic Search

Recent research has demonstrated that quantum comput- ers can solve certain types of problems substantially faster than the known classical algorithms. These problems include factoring integers and certain physics simulations. Practical quantum computation requires overcoming the problems of environmental noise and operational errors, problems which appear to be much more severe than in classical computation due to the inherent fragility

Emanuel Knill; Raymond Laflamme; Wojciech H. Zurek

175

Computer Technology in Adult Education.  

ERIC Educational Resources Information Center

This publication provides materials to help adult educators use computer technology in their teaching. Section 1, Computer Basics, contains activities and materials on these topics: increasing computer literacy, computer glossary, parts of a computer, keyboard, disk care, highlighting text, scrolling and wrap-around text, setting up text,…

Slider, Patty; Hodges, Kathy; Carter, Cea; White, Barbara

176

Thermally assisted adiabatic quantum computation.  

PubMed

We study the effect of a thermal environment on adiabatic quantum computation using the Bloch-Redfield formalism. We show that in certain cases the environment can enhance the performance in two different ways: (i) by introducing a time scale for thermal mixing near the anticrossing that is smaller than the adiabatic time scale, and (ii) by relaxation after the anticrossing. The former can enhance the scaling of computation when the environment is super-Ohmic, while the latter can only provide a prefactor enhancement. We apply our method to the case of adiabatic Grover search and show that performance better than classical is possible with a super-Ohmic environment, with no a priori knowledge of the energy spectrum. PMID:18352448

Amin, M H S; Love, Peter J; Truncik, C J S

2008-02-15

177

Thermally Assisted Adiabatic Quantum Computation  

NASA Astrophysics Data System (ADS)

We study the effect of a thermal environment on adiabatic quantum computation using the Bloch-Redfield formalism. We show that in certain cases the environment can enhance the performance in two different ways: (i) by introducing a time scale for thermal mixing near the anticrossing that is smaller than the adiabatic time scale, and (ii) by relaxation after the anticrossing. The former can enhance the scaling of computation when the environment is super-Ohmic, while the latter can only provide a prefactor enhancement. We apply our method to the case of adiabatic Grover search and show that performance better than classical is possible with a super-Ohmic environment, with no a priori knowledge of the energy spectrum.

Amin, M. H. S.; Love, Peter J.; Truncik, C. J. S.

2008-02-01

178

Quantum Random Networks for Type 2 Quantum Computers.  

National Technical Information Service (NTIS)

Random boolean networks (RBNs) have been studied theoretically and computationally in order to be able to use their remarkable self-healing and large basins of altercation properties as quantum computing architectures, especially focused on problems of ph...

B. Hasslacher, D. L. Allara

2006-01-01

179

Quantum Computational Logics and Possible Applications  

NASA Astrophysics Data System (ADS)

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).

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

2008-01-01

180

Computational Depth Complexity of Measurement-Based Quantum Computation  

Microsoft Academic Search

We prove that one-way quantum computations have the same computational power\\u000aas quantum circuits with unbounded fan-out. It demonstrates that the one-way\\u000amodel is not only one of the most promising models of physical realisation, but\\u000aalso a very powerful model of quantum computation. It confirms and completes\\u000aprevious results which have pointed out, for some specific problems, a depth

Dan E. Browne; Elham Kashefi; Simon Perdrix

2010-01-01

181

Computational depth complexity of measurement-based quantum computation  

Microsoft Academic Search

We prove that one-way quantum computations have the same computational power as quantum circuits with unbounded fan-out. It demonstrates that the one-way model is not only one of the most promising models of physical realisation, but also a very powerful model of quantum computation. It confirms and completes previous results which have pointed out, for some specific problems, a depth

Dan E. Browne; Elham Kashefi; Simon Perdrix

2009-01-01

182

Experimental realization of quantum games on a quantum computer.  

PubMed

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

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

2002-04-01

183

Computer Technology: Bridging the Gap.  

ERIC Educational Resources Information Center

The role of computer technology in China is examined in this paper, with a focus on the current status of school administration, educational technology, educational television, and computer education. A review of current research indicates that computer use in Chinese schools is sparse and haphazard. The recommendation is made that the USA/China…

Richardson, M. D.; And Others

184

Computing quantum discord is NP-complete  

NASA Astrophysics Data System (ADS)

We study the computational complexity of quantum discord (a measure of quantum correlation beyond entanglement), and prove that computing quantum discord is NP-complete. Therefore, quantum discord is computationally intractable: the running time of any algorithm for computing quantum discord is believed to grow exponentially with the dimension of the Hilbert space so that computing quantum discord in a quantum system of moderate size is not possible in practice. As by-products, some entanglement measures (namely entanglement cost, entanglement of formation, relative entropy of entanglement, squashed entanglement, classical squashed entanglement, conditional entanglement of mutual information, and broadcast regularization of mutual information) and constrained Holevo capacity are NP-hard/NP-complete to compute. These complexity-theoretic results are directly applicable in common randomness distillation, quantum state merging, entanglement distillation, superdense coding, and quantum teleportation; they may offer significant insights into quantum information processing. Moreover, we prove the NP-completeness of two typical problems: linear optimization over classical states and detecting classical states in a convex set, providing evidence that working with classical states is generically computationally intractable.

Huang, Yichen

2014-03-01

185

Riemannian Curvature in Quantum Computational Geometry  

NASA Astrophysics Data System (ADS)

In the Riemannian geometry of quantum computation [1]-[3], the quantum evolution is described in terms of the special unitary group of n-qubit unitary operators with unit determinant. To elaborate on one aspect of the methodology, the Riemannian curvature on the group manifold is explicitly derived using the associated Lie algebra. This is important for investigations of the global characteristics of geodesic paths in the group manifold. [1] M. R. Dowling and M. A. Nielsen, ``The Geometry of Quantum Computation,'' Quantum Information and Computation 8, 0861-0899 (2008). [2] H. E. Brandt, ``Riemannian Geometry of Quantum Computation,'' to appear in Nonlinear Analysis (2008). [3] H. E. Brandt, ``Riemannian Geometry of Quantum Computation,'' AMS Short Course Lecture, to appear in Proc. Symposia in Applied Mathematics., American Mathematical Society (2009).

Brandt, Howard

2009-03-01

186

Quantum computing. Defining and detecting quantum speedup.  

PubMed

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

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

2014-07-25

187

Can quantum mechanics help distributed computing?  

Microsoft Academic Search

We present a brief survey of results where quantum information processing is useful to solve distributed computation tasks. We describe problems that are impossible to solve using classical resources but that become feasible with the help of quantum mechanics. We also give examples where the use of quantum information significantly reduces the need for communication. The main focus of the

Anne Broadbent; Alain Tapp

2008-01-01

188

Pattern recognition on a quantum computer  

SciTech Connect

By means of a simple example, it is demonstrated that the task of finding and identifying certain patterns in an otherwise (macroscopically) unstructured picture (dataset) can be accomplished efficiently by a quantum computer. Employing the powerful tool of the quantum Fourier transform, the proposed quantum algorithm exhibits an exponential speedup in comparison with its classical counterpart.

Schuetzhold, Ralf [Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, V6T 1Z1 (Canada)

2003-06-01

189

Multilinear formulas and skepticism of quantum computing  

Microsoft Academic Search

Several researchers, including Leonid Levin, Gerard 't Hooft, and Stephen Wolfram, have argued that quantum mechanics will break down before the factoring of large numbers becomes possible. If this is true, then there should be a natural set of quantum states that can account for all quantum computing experiments performed to date, but not for Shor's factoring algorithm. We investigate

Scott Aaronson

2004-01-01

190

Multilinear Formulas and Skepticism of Quantum Computing  

Microsoft Academic Search

Several researchers, including Leonid Levin, Gerard 't Hooft, and Stephen Wolfram, have argued that quantum mechanics will break down before the factoring of large numbers becomes possible. If this is true, then there should be a natural set of quantum states that can account for all quantum computing experiments performed to date, but not for Shor's factoring algorithm. We investigate

Scott Aaronson

2003-01-01

191

Pseudospin quantum computation in semiconductor nanostructures.  

PubMed

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

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

2003-10-17

192

PREFACE: Quantum Information, Communication, Computation and Cryptography  

NASA Astrophysics Data System (ADS)

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.

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

2007-07-01

193

Nonlinear Optics Quantum Computing with Circuit QED  

NASA Astrophysics Data System (ADS)

One approach to quantum information processing is to use photons as quantum bits and rely on linear optical elements for most operations. However, some optical nonlinearity is necessary to enable universal quantum computing. Here, we suggest a circuit-QED approach to nonlinear optics quantum computing in the microwave regime, including a deterministic two-photon phase gate. Our specific example uses a hybrid quantum system comprising a LC resonator coupled to a superconducting flux qubit to implement a nonlinear coupling. Compared to the self-Kerr nonlinearity, we find that our approach has improved tolerance to noise in the qubit while maintaining fast operation.

Adhikari, Prabin; Hafezi, Mohammad; Taylor, J. M.

2013-02-01

194

Nonlinear optics quantum computing with circuit QED.  

PubMed

One approach to quantum information processing is to use photons as quantum bits and rely on linear optical elements for most operations. However, some optical nonlinearity is necessary to enable universal quantum computing. Here, we suggest a circuit-QED approach to nonlinear optics quantum computing in the microwave regime, including a deterministic two-photon phase gate. Our specific example uses a hybrid quantum system comprising a LC resonator coupled to a superconducting flux qubit to implement a nonlinear coupling. Compared to the self-Kerr nonlinearity, we find that our approach has improved tolerance to noise in the qubit while maintaining fast operation. PMID:23432228

Adhikari, Prabin; Hafezi, Mohammad; Taylor, J M

2013-02-01

195

Review of Computer Networking Technology.  

National Technical Information Service (NTIS)

The report gives a descriptive summary of the technical characteristics of existing computer networks, including data communication technology and configuration related to support of resource sharing services for a computer network. Included are discussio...

R. P. Blanc

1974-01-01

196

The Universe and the Quantum Computer  

NASA Astrophysics Data System (ADS)

It is first pointed out that there is a common mathematical model for the universe and the quantum computer. The former is called the histories approach to quantum mechanics and the latter is called measurement-based quantum computation. Although a rigorous concrete model for the universe has not been completed, a quantum measure and integration theory has been developed which may be useful for future progress. In this work we show that the quantum integral is the unique functional satisfying certain basic physical and mathematical principles. Since the set of paths (or trajectories) for a quantum computer is finite, this theory is easier to treat and more developed. We observe that the sum of the quantum measures of the paths is unity and the total interference vanishes. Thus, constructive interference is always balanced by an equal amount of destructive interference. As an example we consider a simplified two-slit experiment.

Gudder, Stan

2011-12-01

197

Computer Technology and Nursing Education.  

ERIC Educational Resources Information Center

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

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

198

Quantum Computation Based on Electron Spin Qubits Without Spin-Spin Interaction  

NASA Astrophysics Data System (ADS)

Using electron spin states in a unit cell of three semiconductor quantum dots as qubit states, a scalable quantum computation scheme is advocated without invoking qubit-qubit interactions. Single electron tunneling technology and coherent quantum-dot cellular automata architecture are used to generate an ancillary charge entangled state which is then converted into spin entangled state. Without using charge measurement and ancillary qubits, we demonstrate universal quantum computation based on free electron spin and coherent quantum-dot cellular automata.

Wu, Yin-Zhong; Zhang, Wei-Min; Soo, Chopin

2005-10-01

199

Mathematical Aspects of Quantum Computing 2007  

NASA Astrophysics Data System (ADS)

Quantum computing: an overview / M. Nakahara -- Braid group and topological quantum computing / T. Ootsuka, K. Sakuma -- An introduction to entanglement theory / D. J. H. Markham -- Holonomic quantum computing and its optimization / S. Tanimura -- Playing games in quantum mechanical settings: features of quantum games / S. K. Özdemir, J. Shimamura, N. Imoto -- Quantum error-correcting codes / M. Hagiwara -- Poster summaries. Controled teleportation of an arbitrary unknown two-qubit entangled state / V. Ebrahimi, R. Rahimi, M. Nakahara. Notes on the Dür-Cirac classification / Y. Ota, M. Yoshida, I. Ohba. Bang-bang control of entanglement in Spin-Bus-Boson model / R. Rahimi, A. SaiToh, M. Nakahara. Numerical computation of time-dependent multipartite nonclassical correlation / A. SaiToh ... [et al.]. On classical no-cloning theorem under Liouville dynamics and distances / T. Yamano, O. Iguchi.

Nakahara, Mikio; Rahimi, Robabeh; SaiToh, Akira

2008-04-01

200

Adiabatic Quantum Computation: Coherent Control Back Action  

PubMed Central

Though attractive from scalability aspects, optical approaches to quantum computing are highly prone to decoherence and rapid population loss due to nonradiative processes such as vibrational redistribution. We show that such effects can be reduced by adiabatic coherent control, in which quantum interference between multiple excitation pathways is used to cancel coupling to the unwanted, non-radiative channels. We focus on experimentally demonstrated adiabatic controlled population transfer experiments wherein the details on the coherence aspects are yet to be explored theoretically but are important for quantum computation. Such quantum computing schemes also form a back-action connection to coherent control developments.

Goswami, Debabrata

2013-01-01

201

Geometry of quantum computation with qudits.  

PubMed

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

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

2014-01-01

202

Parallel Environment for Quantum Computing  

NASA Astrophysics Data System (ADS)

To facilitate numerical study of noise and decoherence in QC algorithms,and of the efficacy of error correction schemes, we have developed a Fortran 90 quantum computer simulator with parallel processing capabilities. It permits rapid evaluation of quantum algorithms for a large number of qubits and for various ``noise'' scenarios. State vectors are distributed over many processors, to employ a large number of qubits. Parallel processing is implemented by the Message-Passing Interface protocol. A description of how to spread the wave function components over many processors, along with how to efficiently describe the action of general one- and two-qubit operators on these state vectors will be delineated.Grover's search and Shor's factoring algorithms with noise will be discussed as examples. A major feature of this work is that concurrent versions of the algorithms can be evaluated with each version subject to diverse noise effects, corresponding to solving a stochastic Schrodinger equation. The density matrix for the ensemble of such noise cases is constructed using parallel distribution methods to evaluate its associated entropy. Applications of this powerful tool is made to delineate the stability and correction of QC processes using Hamiltonian based dynamics.

Tabakin, Frank; Diaz, Bruno Julia

2009-03-01

203

Universal Quantum Computation with the Exchange Interaction  

Microsoft Academic Search

Experimental implementations of quantum computer architectures are now being investigated in many different physical settings. The full set of require- ments that must be met to make quantum computing a reality in the laboratory (1) is daunting, involving capabilities well beyond the present state of the art. In this report we develop a significant simplification of these requirements that can

D. P. DiVincenzo; D. Bacon; J. Kempe; G. Burkard; K. B. Whaley

204

Decoherence-Free Subspaces for Quantum Computation  

Microsoft Academic Search

Decoherence in quantum computers is formulated within the semigroup approach. The error genera- tors are identified with the generators of a Lie algebra. This allows for a comprehensive description which includes as a special case the frequently assumed spin-boson model. A generic condition is presented for errorless quantum computation: decoherence-free subspaces are spanned by those states which are annihilated by

D. A. Lidar; I. L. Chuang; K. B. Whaley

1998-01-01

205

Fault-tolerant quantum computation by anyons  

Microsoft Academic Search

A two-dimensional quantum system with anyonic excitations can be considered as a quantum computer. Unitary transformations can be performed by moving the excitations around each other. Measurements can be performed by joining excitations in pairs and observing the result of fusion. Such computation is fault-tolerant by its physical nature.

A. Yu. Kitaev; L. D. Landau

2003-01-01

206

A Quantum Computer Architecture for Nonlocal Interactions  

Microsoft Academic Search

Several authors [see for e.g. D.P. DiVincenzo, Fortschr. Phys. 48, 771 (2000) and J. Preskill, Proc. R. Soc. London Ser. A 454 385 (1998).] have described the basic requirements essential to build a scalable quantum computer. Because many physical implementation schemes for quantum computing rely on nearest neighbor interactions, there is a hidden quantum communication overhead to connect distant nodes

Carl Williams; Gavin Brennen; Song Daegene

2003-01-01

207

Toward a superconducting quantum computer. Harnessing macroscopic quantum coherence.  

PubMed

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

Tsai, Jaw-Shen

2010-01-01

208

Embedding quantum simulators for quantum computation of entanglement.  

PubMed

We introduce the concept of embedding quantum simulators, a paradigm allowing the efficient quantum computation of a class of bipartite and multipartite entanglement monotones. It consists in the suitable encoding of a simulated quantum dynamics in the enlarged Hilbert space of an embedding quantum simulator. In this manner, entanglement monotones are conveniently mapped onto physical observables, overcoming the necessity of full tomography and reducing drastically the experimental requirements. Furthermore, this method is directly applicable to pure states and, assisted by classical algorithms, to the mixed-state case. Finally, we expect that the proposed embedding framework paves the way for a general theory of enhanced one-to-one quantum simulators. PMID:24483635

Di Candia, R; Mejia, B; Castillo, H; Pedernales, J S; Casanova, J; Solano, E

2013-12-13

209

A Symbolic Classical Computer Language for Simulation of Quantum Algorithms  

Microsoft Academic Search

Quantum computing is an extremely promising research combining theoretical and experimental quantum physics, mathematics,\\u000a quantum information theory and computer science. Classical simulation of quantum computations will cover part of the gap between\\u000a the theoretical mathematical formulation of quantum mechanics and the realization of quantum computers. One of the most important\\u000a problems in “quantum computer science” is the development of new

Peter Nyman

2009-01-01

210

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

PubMed

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

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

2001-03-26

211

Magnetic Resonance Force Microscopy Quantum Computer with Tellurium Donors in Silicon  

SciTech Connect

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.

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

2001-03-26

212

Relativistic Quantum Metrology: Exploiting relativity to improve quantum measurement technologies  

PubMed Central

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.

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

2014-01-01

213

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

PubMed

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

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

2014-01-01

214

The case for biological quantum computer elements  

NASA Astrophysics Data System (ADS)

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.

Baer, Wolfgang; Pizzi, Rita

2009-05-01

215

Blind quantum computation protocol in which Alice only makes measurements  

NASA Astrophysics Data System (ADS)

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.

Morimae, Tomoyuki; Fujii, Keisuke

2013-05-01

216

Secure Entanglement Distillation for Double-Server Blind Quantum Computation  

NASA Astrophysics Data System (ADS)

Blind quantum computation is a new secure quantum computing protocol where a client, who does not have enough quantum technologies at her disposal, can delegate her quantum computation to a server, who has a fully fledged quantum computer, in such a way that the server cannot learn anything about the client’s input, output, and program. If the client interacts with only a single server, the client has to have some minimum quantum power, such as the ability of emitting randomly rotated single-qubit states or the ability of measuring states. If the client interacts with two servers who share Bell pairs but cannot communicate with each other, the client can be completely classical. For such a double-server scheme, two servers have to share clean Bell pairs, and therefore the entanglement distillation is necessary in a realistic noisy environment. In this Letter, we show that it is possible to perform entanglement distillation in the double-server scheme without degrading the security of blind quantum computing.

Morimae, Tomoyuki; Fujii, Keisuke

2013-07-01

217

Racing a quantum computer through Minkowski spacetime  

NASA Astrophysics Data System (ADS)

The Lorentzian length of a timelike curve connecting both endpoints of a computation in Minkowski spacetime is smaller than the Lorentzian length of the corresponding geodesic. In this talk, I will point out some properties of spacetime that allow an inertial classical computer to outperform a quantum one, at the completion of a long journey. We will focus on a comparison between the optimal quadratic Grover speed up from quantum computing and an n=2 speedup using classical computers and relativistic effects. These results are not practical as a new model of computation, but allow us to probe the ultimate limits physics places on computers.

Biamonte, Jacob D.

2010-05-01

218

Graph isomorphism and adiabatic quantum computing  

NASA Astrophysics Data System (ADS)

In the graph isomorphism (GI) problem two N-vertex graphs G and G' are given and the task is to determine whether there exists a permutation of the vertices of G that preserves adjacency and transforms G ?G'. If yes, then G and G' are said to be isomorphic; otherwise they are nonisomorphic. The GI problem is an important problem in computer science and is thought to be of comparable difficulty to integer factorization. In this paper we present a quantum algorithm that solves arbitrary instances of GI and which also provides an approach to determining all automorphisms of a given graph. We show how the GI problem can be converted to a combinatorial optimization problem that can be solved using adiabatic quantum evolution. We numerically simulate the algorithm's quantum dynamics and show that it correctly (i) distinguishes nonisomorphic graphs; (ii) recognizes isomorphic graphs and determines the permutation(s) that connect them; and (iii) finds the automorphism group of a given graph G. We then discuss the GI quantum algorithm's experimental implementation, and close by showing how it can be leveraged to give a quantum algorithm that solves arbitrary instances of the NP-complete subgraph isomorphism problem. The computational complexity of an adiabatic quantum algorithm is largely determined by the minimum energy gap ? (N) separating the ground and first-excited states in the limit of large problem size N ?1. Calculating ? (N) in this limit is a fundamental open problem in adiabatic quantum computing, and so it is not possible to determine the computational complexity of adiabatic quantum algorithms in general, nor consequently, of the specific adiabatic quantum algorithms presented here. Adiabatic quantum computing has been shown to be equivalent to the circuit model of quantum computing, and so development of adiabatic quantum algorithms continues to be of great interest.

Gaitan, Frank; Clark, Lane

2014-02-01

219

Quantum Computer for Shor's Algorithm.  

National Technical Information Service (NTIS)

We employ learning algorithms, optical and terahertz pulse shaping and ultrafast laser techniques to control quantum coherence in Rydberg atom wave packet quantum data registers. Our goals are to discover efficient ways to limit decoherence in these syste...

P. H. Bucksbaum

2004-01-01

220

Quantum Computation of Fluid Dynamics.  

National Technical Information Service (NTIS)

Presented is a quantum lattice gas for Navier-Stokes fluid dynamics simulation. The quantum lattice-gas transport equation at the microscopic scale is presented as a generalization of the classical lattice-gas transport equation. A special type of quantum...

J. Yepez

1998-01-01

221

From transistor to trapped-ion computers for quantum chemistry.  

PubMed

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

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

2014-01-01

222

Quantum computations: algorithms and error correction  

Microsoft Academic Search

Contents §0. Introduction §1. Abelian problem on the stabilizer §2. Classical models of computations2.1. Boolean schemes and sequences of operations2.2. Reversible computations §3. Quantum formalism3.1. Basic notions and notation3.2. Transformations of mixed states3.3. Accuracy §4. Quantum models of computations4.1. Definitions and basic properties4.2. Construction of various operators from the elements of a basis4.3. Generalized quantum control and universal schemes §5.

A Yu Kitaev

1997-01-01

223

Concatenated codes for fault tolerant quantum computing  

SciTech Connect

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.

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

1995-05-01

224

Conduction pathways in microtubules, biological quantum computation, and consciousness.  

PubMed

Technological computation is entering the quantum realm, focusing attention on biomolecular information processing systems such as proteins, as presaged by the work of Michael Conrad. Protein conformational dynamics and pharmacological evidence suggest that protein conformational states-fundamental information units ('bits') in biological systems-are governed by quantum events, and are thus perhaps akin to quantum bits ('qubits') as utilized in quantum computation. 'Real time' dynamic activities within cells are regulated by the cell cytoskeleton, particularly microtubules (MTs) which are cylindrical lattice polymers of the protein tubulin. Recent evidence shows signaling, communication and conductivity in MTs, and theoretical models have predicted both classical and quantum information processing in MTs. In this paper we show conduction pathways for electron mobility and possible quantum tunneling and superconductivity among aromatic amino acids in tubulins. The pathways within tubulin match helical patterns in the microtubule lattice structure, which lend themselves to topological quantum effects resistant to decoherence. The Penrose-Hameroff 'Orch OR' model of consciousness is reviewed as an example of the possible utility of quantum computation in MTs. PMID:11755497

Hameroff, Stuart; Nip, Alex; Porter, Mitchell; Tuszynski, Jack

2002-01-01

225

Computer Technology in Industry.  

National Technical Information Service (NTIS)

Contents: An automated work site for designers and technologists; Package of applied programs for organizing multipurpose-structure data banks for the unified computer system--the International Exhibition 'Interorgtekhnika-75,' Soviet Section; Package of ...

1975-01-01

226

Quantum computers on multiatomic ensembles in quantum electrodynamic cavity  

NASA Astrophysics Data System (ADS)

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.

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

2012-03-01

227

Ramsey Numbers and Adiabatic Quantum Computing  

NASA Astrophysics Data System (ADS)

The graph-theoretic Ramsey numbers are notoriously difficult to calculate. In fact, for the two-color Ramsey numbers R(m,n) with m, n?3, only nine are currently known. We present a quantum algorithm for the computation of the Ramsey numbers R(m,n). We show how the computation of R(m,n) can be mapped to a combinatorial optimization problem whose solution can be found using adiabatic quantum evolution. We numerically simulate this adiabatic quantum algorithm and show that it correctly determines the Ramsey numbers R(3,3) and R(2,s) for 5?s?7. We then discuss the algorithm’s experimental implementation, and close by showing that Ramsey number computation belongs to the quantum complexity class quantum Merlin Arthur.

Gaitan, Frank; Clark, Lane

2012-01-01

228

The Physical Implementation of Quantum Computation  

Microsoft Academic Search

After a brief introduction to the principles and promise of quantum\\u000ainformation processing, the requirements for the physical implementation of\\u000aquantum computation are discussed. These five requirements, plus two relating\\u000ato the communication of quantum information, are extensively explored and\\u000arelated to the many schemes in atomic physics, quantum optics, nuclear and\\u000aelectron magnetic resonance spectroscopy, superconducting electronics, and\\u000aquantum-dot

David P. DiVincenzo

2000-01-01

229

Statistical Analysis for Quantum Adiabatic Computations: Quantum Monte Carlo Annealing  

NASA Astrophysics Data System (ADS)

Quantum adiabatic computations are designed to determine the ground state configurations of an classical problem Hamiltonian H3SAT within quantum theory and at imaginary time allow statistical mechanics studies for the computational e_ciency of the ground state search. We mention a recent determination of the quantum complexity, i.e. the mass-gap _mGAP for a specific ensemble of three-satisfiability (3SAT) problems with a unique satisfiability assignment, which shows an exponential increase of the gap correlation length _GAP with _GAP = 1=_mGAP. In 3SAT we present numerical data for the behavior of quantum Monte Carlo annealing cycles in search for the ground state. The findings show, that for the specific set of realizations quantum Monte Carlo searches in 3SAT fail above a sharp cut-o_ Kcut in the complexity K, which exemplifies the intractable nature of 3SAT.

Neuhaus, T.

230

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

SciTech Connect

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.

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

231

Is the Brain a Quantum Computer?  

ERIC Educational Resources Information Center

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…

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

2006-01-01

232

Quantum Computational Complexity of Spin Glasses.  

National Technical Information Service (NTIS)

While it is in some sense natural that quantum systems are efficient at simulating one another, a less natural question is the efficient simulation of classical systems on quantum computers (QCs). This question was first raised, and partly answered by the...

D. Lidar

2011-01-01

233

Analog analogue of a digital quantum computation  

Microsoft Academic Search

We solve a problem, which while not fitting into the usual paradigm, can be viewed as a quantum computation. Suppose we are given a quantum system with a Hamiltonian of the form E\\\\|w> is an unknown (normalized) state. The problem is to produce \\\\|w> by adding a Hamiltonian (independent of \\\\|w>) and evolving the system. If \\\\|w> is chosen uniformly

Edward Farhi; Sam Gutmann

1998-01-01

234

Decoherence and a simple quantum computer  

SciTech Connect

The authors analyze the effect of decoherence on the operation of part of a simple quantum computer. The results indicate that quantum bit coding techniques may be used to mitigate the effects of two sources of decoherence - amplitude damping and phase randomization.

Chuang, I.L.; Yamamoto, Y. [Stanford Univ., CA (United States); Laflamme, R. [Los Alamos National Lab., NM (United States)

1995-10-01

235

Information Technology: Computer Systems Engineer  

NSDL National Science Digital Library

Watch how a community college education took one person from being a computer know-nothing to having a career as a successful information technologist, in this video adapted from Pathways to Technology.

Foundation, Wgbh E.

2012-05-18

236

Trusted Computing Technologies, Intel Trusted Execution Technology  

Microsoft Academic Search

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

Max Joseph Guise; Jeremy Daniel Wendt

2011-01-01

237

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

NASA Technical Reports Server (NTRS)

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.

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

1999-01-01

238

Experimental Demonstration of Quantum Lattice Gas Computation  

Microsoft Academic Search

We report an ensemble nuclear magnetic resonance (NMR) implementation of a\\u000aquantum lattice gas algorithm for the diffusion equation. The algorithm employs\\u000aan array of quantum information processors sharing classical information, a\\u000anovel architecture referred to as a type-II quantum computer. This concrete\\u000aimplementation provides a test example from which to probe the strengths and\\u000alimitations of this new computation

Marco A. Pravia; Zhiying Chen; David G. Cory; Jeffrey Yepez

2003-01-01

239

Ancilla-driven universal quantum computation  

Microsoft Academic Search

We introduce a model of quantum computation intermediate between the gate-based and measurement-based models. A quantum register is manipulated remotely with the help of a single ancilla that ''drives'' the evolution of the register. The fully controlled ancilla qubit is coupled to the computational register only via a fixed unitary two-qubit interaction and then measured in suitable bases, driving both

Janet Anders; Dan E. Browne; Daniel K. L. Oi; Elham Kashefi; Erika Andersson

2010-01-01

240

Delayed commutation in quantum computer networks.  

PubMed

In the same way that classical computer networks connect and enhance the capabilities of classical computers, quantum networks can combine the advantages of quantum information and communication. We propose a nonclassical network element, a delayed commutation switch, that can solve the problem of switching time in packet switching networks. With the help of some local ancillary qubits and superdense codes, we can route a qubit packet after part of it has left the network node. PMID:17025870

García-Escartín, Juan Carlos; Chamorro-Posada, Pedro

2006-09-15

241

Quantum Computation by Adiabatic Evolution  

Microsoft Academic Search

We give a quantum algorithm for solving instances of the satisfiability problem, based on adiabatic evolution. The evolution of the quantum state is governed by a time-dependent Hamiltonian that interpolates between an initial Hamiltonian, whose ground state is easy to construct, and a final Hamiltonian, whose ground state encodes the satisfying assignment. To ensure that the system evolves to the

Edward Farhi; Jeffrey Goldstone; Sam Gutmann; Michael Sipser

2000-01-01

242

Quantum Field Theory and Computational Paradigms  

NASA Astrophysics Data System (ADS)

We introduce the basic theory of quantization of radiation field in quantum physics and explain how it relates to the theory of recursive functions in computer science. We outline the basic differences between quantum mechanics (QM) and quantum field theory (QFT) and explain why QFT is better suited for a computational paradigm - based on algorithmic requirement, countably infinite degrees of freedom and the creation of macroscopic output objects. The quanta of the radiation field correspond to the non-negative integers and the harmonic oscillator spectra correspond to the recursive computation - with the creation and annihilation operators, respectively, playing the same role as the successor and predecessor in computability theory. Accordingly, this approach relates the classical computational model and the quantum physical model more directly than the Turing machine approach used earlier. Also, the application of Lambda calculus formalism and the associated denotational semantics (that is widely used in the classical computational paradigm involving recursive functions) for applications to computational paradigm based on quantum field theory is described. Finally, we explain where QFT and conventional paradigm depart from each other, and examine the concept of fixed points, phase transitions, programmability, emergent computation and related open problems.

Krishnamurthy, E. V.; Krishnamurthy, Vikram

243

Building an organization that can build a quantum computer  

NASA Astrophysics Data System (ADS)

Quantum computation is based on a very compelling idea: that physics, and physics alone, ultimately determines what can be computed, and how efficiently. Changing the laws of physics relevant for a computing device can open up new possibilities for manipulating information, allowing better algorithms that could transform the way we live. Quantum computation has, up until very recently, been the province of basic research. It is clear that the extreme difficulty and complexity of converting this basic science into useful technology cannot occur within a basic research environment. Here I will describe the conceptual framework behind D-Wave's organization and technology development model, and compare and contrast this approach to other possible models.

Rose, Geordie

2009-05-01

244

EDITORIAL: Quantum Computing and the Feynman Festival  

NASA Astrophysics Data System (ADS)

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.

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

2003-12-01

245

Computer Animation in Future Technologies  

Microsoft Academic Search

In this introductory chapter, we try to situate the role of Computer Animation in the new technologies: digital television, virtual reality, multimedia, cooperative work. We also overview the main techniques which will be further discussed throughout this book by international experts. 1 The high-tech role of computer animation The term \\

Nadia Magnenat Thalmann; Daniel Thalmann

1998-01-01

246

Keynote Speech: Quantum Physics and the Nature of Computation  

Microsoft Academic Search

Quantum physics is a fascinating area from a computational viewpoint. The features that make quantum systems prohibitively hard to simulate classically are precisely the aspects exploited by quantum computation to obtain exponential speedups over classical computers. In this talk I will survey our current understanding of the power (and limits) of quantum computers, and prospects for experimentally realizing them in

Umesh V. Vazirani

2007-01-01

247

Measurement-based quantum computation on cluster states  

Microsoft Academic Search

We give a detailed account of the one-way quantum computer, a scheme of quantum computation that consists entirely of one-qubit measurements on a particular class of entangled states, the cluster states. We prove its universality, describe why its underlying computational model is different from the network model of quantum computation, and relate quantum algorithms to mathematical graphs. Further we investigate

Robert Raussendorf; Daniel E. Browne; Hans J. Briegel

2003-01-01

248

A Quantum Computer Architecture for Nonlocal Interactions  

NASA Astrophysics Data System (ADS)

Several authors [see for e.g. D.P. DiVincenzo, Fortschr. Phys. 48, 771 (2000) and J. Preskill, Proc. R. Soc. London Ser. A 454 385 (1998).] have described the basic requirements essential to build a scalable quantum computer. Because many physical implementation schemes for quantum computing rely on nearest neighbor interactions, there is a hidden quantum communication overhead to connect distant nodes of the computer. Here we propose a physical solution to this problem which, together with the key building blocks, provides a pathway to a scalable quantum architecture using nonlocal interactions. Our solution involves the concept of a quantum bus that acts as a refreshable entanglement resource to connect distant memory nodes providing a broad architectural concept for quantum computers with potential applications to some solid state proposals and neutral atom schemes [G.K. Brennen, D. Song, and C.J. Williams, quant-ph 0301012, Phys. Rev. Lett. (submitted)]. The approach is found to be robust with respect to various error models applied to the quantum bus. [We would like to acknowledge Mark Heiligman for suggesting this problem and DARPA-QuIST and ARDA/NSA for partial support.

Williams, Carl; Brennen, Gavin; Daegene, Song

2003-05-01

249

Simulating physical phenomena with a quantum computer  

NASA Astrophysics Data System (ADS)

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.

Ortiz, Gerardo

2003-03-01

250

Revisiting the hopes for scalable quantum computation  

NASA Astrophysics Data System (ADS)

The hopes for scalable quantum computing rely on the "threshold theorem": once the error per qubit per gate is below a certain value, the methods of quantum error correction allow indefinitely long quantum computations. The proof is based on a number of assumptions, which are supposed to be satisfied exactly, like axioms, e.g., zero undesired interactions between qubits, etc. However, in the physical world no continuous quantity can be exactly zero, it can only be more or less small. Thus the "error per qubit per gate" threshold must be complemented by the required precision with which each assumption should be fulfilled. In the absence of this crucial information, the prospects of scalable quantum computing remain uncertain.

Dyakonov, M. I.

2013-12-01

251

Simulating fermions on a quantum computer  

NASA Astrophysics Data System (ADS)

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.

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

2002-07-01

252

Quantum 1/f effect in spin decoherence rates and quantum computing  

NASA Astrophysics Data System (ADS)

The quantum 1/f effect is a fundamental new aspect of quantum mechanics, quantum electrodynamics, and quantum field theory in general, with practical importance in most high-technology applications. It is based on the reaction of material currents to their spontaneous emission of infra-quanta such as photons, gravitons, transversal phonons, spin waves, etc. It is the result of decoherence of entangled states of particles and their spontaneous bremsstrahlung, a consequence of infrared-divergent interactions between particles and their field. It is the quantum manifestation of classical turbulence and it represents the most fundamental form of quantum chaos. It is described by the simple universal formula of conventional and coherent quantum 1/f noise, important in engineering, science and technology. It provides a new physical meaning to the notion of ``constant current,'' in time and space, similar to the 1937 definition of elastic processes by Bloch and Nordsieck. Finally, it is an interesting aspect of the concrete way in which matter generates its forms of existence, for instance time and space. Quantum 1/f spin decoherence rates, known to severely limit the performance of quantum computers, are shown here to be also affected by the quantum 1/f effect. Indeed, the elementary spin-flip process has a bremsstrahlung amplitude, leading to a non-stationary state with 1/f quantum fluctuations, and a disentangled system of non-localized low-frequency photons with negative conditional entropy. Thus, decoherence is due to the entangled system's interaction with the rest of the world, as is its quantum 1/f fluctuation which can be expressed in qubits. Increasing the spin-excess n is one way to reduce these fluctuations. In general, we find that both decoherence and its quantum 1/f noise could be controlled by better insulating the system in a new way. .

Handel, Peter H.

2001-06-01

253

Quantum algorithms in one-way quantum computation  

NASA Astrophysics Data System (ADS)

Cluster states are the fundamental resource for the one-way model of quantum computation. In this paper we show the realization of a two-photon four-qubit cluster state. The qubits are encoded in the polarization and the linear momentum of the particles. By using this state we realized two important quantum algorithms, namely the Grover’s search and the Deutsch’s algorithm.

Vallone, G.; de Martini, F.; Mataloni, P.

2010-02-01

254

Universal quantum computation in a semiconductor quantum wire network  

SciTech Connect

Universal quantum computation (UQC) using Majorana fermions on a two-dimensional topological superconducting (TS) medium remains an outstanding open problem. This is because the quantum gate set that can be generated by braiding of the Majorana fermions does not include any two-qubit gate and also no single-qubit {pi}/8 phase gate. In principle, it is possible to create these crucial extra gates using quantum interference of Majorana fermion currents. However, it is not clear if the motion of the various order parameter defects (vortices, domain walls, etc.), to which the Majorana fermions are bound in a TS medium, can be quantum coherent. We show that these obstacles can be overcome using a semiconductor quantum wire network in the vicinity of an s-wave superconductor, by constructing topologically protected two-qubit gates and any arbitrary single-qubit phase gate in a topologically unprotected manner, which can be error corrected using magic-state distillation. Thus our strategy, using a judicious combination of topologically protected and unprotected gate operations, realizes UQC on a quantum wire network with a remarkably high error threshold of 0.14 as compared to 10{sup -3} to 10{sup -4} in ordinary unprotected quantum computation.

Sau, Jay D.; Das Sarma, S. [Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742-4111 (United States); Tewari, Sumanta [Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742-4111 (United States); Department of Physics and Astronomy, Clemson University, Clemson, South Carolina 29634 (United States)

2010-11-15

255

Quantum computing in control and optimization  

NASA Astrophysics Data System (ADS)

This paper deals with the progress made in applications of quantum computing in control and optimization. It concentrates on applying the geometric technique in order to investigate a finite control problem of a two-level quantum system, resonance control of a three-level system, simulation of bilinear quantum control systems, and optimal control using the Bellman principle. We show that a quantum object described by a Schroedinger equation can be controlled in an optimal way by electromagnetic modes. We also demonstrate an application of these techniques and an algebra-geometric approach to the study of dynamic processes in nonlinear systems. The information processing by means of controlled quantum lattices is discussed: we present new mathematical models of classical (CL) and quantum-mechanical lattices (QML) and their application to information processing. system-theoretical results on the observability, controllability and minimal realizability theorems are formulated for cl. The cellular dynamaton (CD) based on quantum oscillators is presented. Cellular's quantum computational search procedure can provide the basis for implementing adaptive global optimization algorithms. A brief overview of the procedure is given and a framework called lattice adaptive search is set up. A method of Yatsenko and one introduced by the authors fit into this framework and are compared.

Yatsenko, Vitaliy; Boyko, Nikita; Xanthopoulos, Petros; Pardalos, Panos

2007-05-01

256

A Quantum Lattice-Gas Model for Computational Fluid Dynamics  

Microsoft Academic Search

Quantum-computing ideas are applied to the practical and ubiquitous problem of fluid dynamics simulation. Presented in this talk is a quantum computing algorithm called a quantum lattice gas. An analytical treatment of the microscopic quantum lattice-gas system is summarized and the predicted effective field theory of the quantum system, at the mesoscopic and macroscopic scales, is given. At the mesoscopic

Jeffrey Yepez

2000-01-01

257

Quantum lattice-gas model for computational fluid dynamics  

Microsoft Academic Search

Quantum-computing ideas are applied to the practical and ubiquitous problem of fluid dynamics simulation. Hence, this paper addresses two separate areas of physics: quantum mechanics and fluid dynamics (or specifically, the computational simulation of fluid dynamics). The quantum algorithm is called a quantum lattice gas. An analytical treatment of the microscopic quantum lattice-gas system is carried out to predict its

Jeffrey Yepez

2001-01-01

258

Efficient Quantum Circuits for One-Way Quantum Computing  

NASA Astrophysics Data System (ADS)

While Ising-type interactions are ideal for implementing controlled phase flip gates in one-way quantum computing, natural interactions between solid-state qubits are most often described by either the XY or the Heisenberg models. We show an efficient way of generating cluster states directly using either the imaginary SWAP (iSWAP) gate for the XY model, or the SWAP gate for the Heisenberg model. Our approach thus makes one-way quantum computing more feasible for solid-state devices.

Tanamoto, Tetsufumi; Liu, Yu-Xi; Hu, Xuedong; Nori, Franco

2009-03-01

259

Helsinki University of Technology: Computational Information Technology  

NSDL National Science Digital Library

Computational Information Technology is a research group of the Laboratory of Computational Engineering at the Helsinki University of Technology in Finland. This section of the website introduces visitors to the group's work on modelling and analyzing complex physical, technical and economic processes and systems. Researchers "carry out method development and application oriented research on advanced probabilistic and information theoretic methods." Some applications include statistical modelling of financial markets, pattern recognition in neural networks, machine vision for microscope image processing, data mining, and intelligent human-machine interfaces. The Research Projects section describes the group's work in these areas and highlights the mathematical and statistical methods used, such as Bayesian methods, vision geometry, Turing's reaction-diffusion systems, and time-frequency analysis. Each research area has its own website, where the overall project and theoretical framework is described along with images and diagrams. Publications, such as theses and journal articles are listed and some conference proceedings and articles are available to download.

260

Universal quantum computation with unlabelled qubits  

NASA Astrophysics Data System (ADS)

We show that an nth root of the Walsh-Hadamard transform (obtained from the Hadamard gate and a cyclic permutation of the qubits), together with two diagonal matrices, namely a local qubit-flip (for a fixed but arbitrary qubit) and a non-local phase-flip (for a fixed but arbitrary coefficient), can do universal quantum computation on n qubits. A quantum computation, making use of n qubits and based on these operations, is then a word of variable length, but whose letters are always taken from an alphabet of cardinality three. Therefore, in contrast with other universal sets, no choice of qubit lines is needed for the application of the operations described here. A quantum algorithm based on this set can be interpreted as a discrete diffusion of a quantum particle on a de Bruijn graph, corrected on-the-fly by auxiliary modifications of the phases associated with the arcs.

Severini, Simone

2006-06-01

261

Modeling fluid dynamics on type II quantum computers  

Microsoft Academic Search

A quantum algorithm is presented for modeling the time evolution of density and flow fields governed by classical equations, such as the diffusion equation, the nonlinear Burgers equation, and the damped wave equation. The algorithm is intended to run on a type-II quantum computer, a parallel quantum computer consisting of a lattice of small type I quantum computers undergoing unitary

James Scoville; Jeffrey Yepez

2006-01-01

262

A scheme for efficient quantum computation with linear optics  

Microsoft Academic Search

Quantum computers promise to increase greatly the efficiency of solving problems such as factoring large integers, combinatorial optimization and quantum physics simulation. One of the greatest challenges now is to implement the basic quantum-computational elements in a physical system and to demonstrate that they can be reliably and scalably controlled. One of the earliest proposals for quantum computation is based

E. Knill; R. Laflamme; G. J. Milburn

2001-01-01

263

Accuracy Threshold for Quantum Computation  

Microsoft Academic Search

We have previously [11] shown that for quantum memories andquantum communication, a state can be transmitted over arbitrarydistances with error ffl provided each gate has error at most cffl. Wediscuss a similar concatenation technique which can be used with faulttolerant networks to achieve any desired accuracy when computingwith classical initial states, provided a minimum gate accuracy can beachieved. The technique

Emanuel Knill; Raymond Laflamme; Wojciech Zurek

1996-01-01

264

Molecular quantum computer of neuron.  

PubMed

Living cells are controlled by quantum regulators in which the price of action of elementary operations approaches Planck's constant. The description of such systems is based on four principles: (1) minimal price of action principle for control; (2) principle of optimality; (3) minimum irreversibility principle; and (4) the principle of causality. PMID:7488717

Liberman, E A; Minina, S V

1995-01-01

265

Theory of fault-tolerant quantum computation  

Microsoft Academic Search

In order to use quantum error-correcting codes to improve the performance of a quantum computer, it is necessary to be able to perform operations fault-tolerantly on encoded states. I present a theory of fault-tolerant operations on stabilizer codes based on symmetries of the code stabilizer. This allows a straightforward determination of which operations can be performed fault-tolerantly on a given

Daniel Gottesman

1998-01-01

266

New Mathematical Tools for Quantum Technology  

Microsoft Academic Search

Progress in manufacturing technology has allowed us to probe the behavior of devices on a smaller and faster scale than ever before. With increasing miniaturization, quantum effects come to dominate the transport properties of these devices, between collisions, carriers undergo ballistic motion under the influence of local electric and magnetic fields. The often surprising propertiesof quantum ballistic transport are currently

Christian Bracher; Manfred Kleber; Tobias Kramer

2007-01-01

267

Quantum computation with ``hot`` trapped ions  

SciTech Connect

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.

James, D.F.V. [Los Alamos National Lab., NM (United States); Schneider, S. [Los Alamos National Lab., NM (United States)]|[Univ. of Queensland, St. Lucia, Queensland (Australia); Milburn, G.J. [Univ. of Queensland, St. Lucia, Queensland (Australia)

1998-12-31

268

Quantum computation with vibrationally excited molecules.  

PubMed

A new physical implementation for quantum computation is proposed. The vibrational modes of molecules are used to encode qubit systems. Global quantum logic gates are realized using shaped femtosecond laser pulses which are calculated applying optimal control theory. The scaling of the system is favorable; sources for decoherence can be eliminated. A complete set of one- and two-quantum gates is presented for a specific molecule. Detailed analysis regarding experimental realization shows that the structural resolution of today's pulse shapers is easily sufficient for pulse formation. PMID:12366025

Tesch, Carmen M; De Vivie-Riedle, Regina

2002-10-01

269

Neuromorphic quantum computation with energy dissipation  

NASA Astrophysics Data System (ADS)

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.

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

2005-11-01

270

Captology: Computers as Persuasive Technologies  

NSDL National Science Digital Library

"The Stanford Persuasive Technology Lab creates insight into how computing products -- from websites to mobile phone software -- can be designed to change what people believe and what they do." This unusual field of study is called captology, and the subject is explored in detail on the lab's homepage. The Key Concepts section provides a brief overview of captology and links to another page with nine topic papers published by researchers at the lab. In a series of examples demonstrating how computers can be used to influence a person, the site's creators separate instances into macrosuasion and microsuasion. Specific websites and computer programs are highlighted to reveal these interesting marketing or motivational tactics.

271

Ancilla-driven universal quantum computation  

SciTech Connect

We introduce a model of quantum computation intermediate between the gate-based and measurement-based models. A quantum register is manipulated remotely with the help of a single ancilla that ''drives'' the evolution of the register. The fully controlled ancilla qubit is coupled to the computational register only via a fixed unitary two-qubit interaction and then measured in suitable bases, driving both single- and two-qubit operations on the register. Arbitrary single-qubit operations directly on register qubits are not needed. We characterize all interactions E that induce a unitary, stepwise deterministic measurement back-action on the register sufficient to implement any quantum channel. Our scheme offers experimental advantages for computation, state preparation, and generalized measurements, since no tunable control of the register is required.

Anders, Janet; Browne, Dan E. [Department of Physics and Astronomy, University College London, London WC1E 6BT (United Kingdom); Oi, Daniel K. L. [SUPA, Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Kashefi, Elham [School of Informatics, University of Edinburgh, Edinburgh EH8 9AB (United Kingdom); Andersson, Erika [SUPA, Department of Physics, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom)

2010-08-15

272

Quantum Computation and Quantum Measurements with Mesoscopic Superconducting Structures  

NASA Astrophysics Data System (ADS)

Systems of mesoscopic Josephson junctions are at present among the leading candidates for development of practical qubits for quantum information devices. Although different qubit structures have been realized with Josephson junctions, their common feature is the design that is optimized to overcome the problem of decoherence by the low-frequency noise that exists in all solid-state structures. In the presented dissertation research, we propose and study an alternative approach of direct suppression of noise by a feedback loop based on the low-frequency quantum measurements. The minimal noise induced in the qubit by such a feedback loop is calculated under the conditions of continuous quantum-limited measurements. Another obstacle facing the quantum Josephson junction circuits is the information transfer between the circuit elements. Here we study the quantum dynamics of dual-rail arrays of nSQUIDs characterized by a negative inductance between its arms, which hold promise for quantum information transfer. The scaling and decoherence properties of these arrays are analyzed. Information transfer along nSQUID arrays can also be used to implement adiabatic quantum computation (AQC), an alternative to the gate-model approach to quantum computation that is expected to be more stable against the decoherence. Here we suggest fidelity of the ground state as the quantitative measure of the ultimate effect of decoherence on AQC. We show that decoherence-induced deformation of the ground state of an AQC algorithm is characterized by the same noise correlators as those that determine the decoherence time in the gate-model approach. Results for fidelity of a 16-qubit array at finite temperatures are obtained numerically.

Deng, Qiang

273

Oxide-semiconductor materials for quantum computing.  

NASA Astrophysics Data System (ADS)

A scheme for quantum computing is proposed with ferroelectrically coupled Ge/Si quantum dots. Ge dots are grown on a Si substrate. A ferroelectric film (STO) is grown to cover the dots. Qubits are electron spins confined in quantum dots. Quantum gating is achieved by manipulating electron interactions across adjacent dots with ferroelectric materials. A low temperature AFM/ANSOM microscope is built with a tuning-fork type tip to investigate the electrical and optical properties of both ferroelectric materials and quantum dots. Tip-sample distance is maintained by a phase-lock loop. In AFM mode topographic images are taken on Ge/Si quantum dots and ferroelectric thin films. DC bias applied on a ferroelectric film controls the polarization of the film in order to form patterns. Patterns are later imaged. Optical properties of quantum dots can be obtained in ANSOM mode of the microscope. An AFM tip scatters light onto single quantum dots to achieve subwavelength resolution of optical images of the sample and spectral information of single dots.

Zhu, H.; Patil, N. G.; Levy, Jeremy

2002-03-01

274

Silicon enhancement mode nanostructures for quantum computing.  

SciTech Connect

Development of silicon, enhancement mode nanostructures for solid-state quantum computing will be described. A primary motivation of this research is the recent unprecedented manipulation of single electron spins in GaAs quantum dots, which has been used to demonstrate a quantum bit. Long spin decoherence times are predicted possible in silicon qubits. This talk will focus on silicon enhancement mode quantum dot structures that emulate the GaAs lateral quantum dot qubit but use an enhancement mode field effect transistor (FET) structure. One critical concern for silicon quantum dots that use oxides as insulators in the FET structure is that defects in the metal oxide semiconductor (MOS) stack can produce both detrimental electrostatic and paramagnetic effects on the qubit. Understanding the implications of defects in the Si MOS system is also relevant for other qubit architectures that have nearby dielectric passivated surfaces. Stable, lithographically defined, single-period Coulomb-blockade and single-electron charge sensing in a quantum dot nanostructure using a MOS stack will be presented. A combination of characterization of defects, modeling and consideration of modified approaches that incorporate SiGe or donors provides guidance about the enhancement mode MOS approach for future qubits and quantum circuit micro-architecture.

Carroll, Malcolm S.

2010-03-01

275

Elementary gates for quantum computation  

Microsoft Academic Search

We show that a set of gates that consists of all one-bit quantum gates [U(2)] and the two-bit exclusive-OR gate [that maps Boolean values (x,y) to (x,x?y)] is universal in the sense that all unitary operations on arbitrarily many bits n [U(2n)] can be expressed as compositions of these gates. We investigate the number of the above gates required to

Adriano Barenco; Charles H. Bennett; Richard Cleve; David P. Divincenzo; Norman Margolus; Peter Shor; Tycho Sleator; John A. Smolin; Harald Weinfurter

1995-01-01

276

Computer Technology. Career Education Guide.  

ERIC Educational Resources Information Center

The curriculum guide is designed to provide students with realistic training in computer technology theory and practice within the secondary educational framework and to prepare them for entry into an occupation or continuing postsecondary education. Each unit plan consists of a description of the area under consideration, estimated hours of…

Dependents Schools (DOD), Washington, DC. European Area.

277

Random Numbers and Quantum Computers  

ERIC Educational Resources Information Center

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…

McCartney, Mark; Glass, David

2002-01-01

278

New World Vistas: New Models of Computation Lattice Based Quantum Computation.  

National Technical Information Service (NTIS)

I propose to consider the feasibility of implementing a quantum lattice-gas dynamics based on quantum computing ideas and to explore the practicality of building a quantum computer, a question first posed by Richard Feynman over a decade ago.

J. Yepez

1996-01-01

279

Optical Computers and Space Technology  

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

280

Quantum Optical Implementation of Quantum Computing and Quantum Informatics Protocols.  

National Technical Information Service (NTIS)

An enumeration of several research efforts funded by the above award is attached. Key aspects reported on include: (a) Optically controlled delays for broadband pulses and all-optic steering; (b) Sub-wavelength atom localization: (c)Quantum microscopy; (d...

M. O. Scully M. S. Zubairy

2006-01-01

281

Quantum information processing : science & technology.  

SciTech Connect

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.

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

2010-09-01

282

Adiabatic quantum computation with Rydberg-dressed atoms  

NASA Astrophysics Data System (ADS)

We study an architecture for implementing adiabatic quantum computation with trapped neutral atoms. Ground-state atoms are dressed by laser fields in a manner conditional on the Rydberg blockade mechanism, thereby providing the requisite entangling interactions. As a benchmark, we study the performance of quantum annealing to the ground state of an Ising spin lattice. We model a proof-of-principle experiment in a realistic architecture, including details of the atomic implementation, with qubits encoded in the clock states of 133Cs. Numerical simulation yields fidelities >0.98 for up to four qubits, and implementations of 10-20 qubits are within the range of current technology.

Keating, Tyler; Goyal, Krittika; Jau, Yuan-Yu; Biedermann, Grant W.; Landahl, Andrew J.; Deutsch, Ivan H.

2013-05-01

283

Quantum computer games: Schrödinger cat and hounds  

NASA Astrophysics Data System (ADS)

The quantum computer game 'Schrödinger 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. 'Schrödinger 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.

Gordon, Michal; Gordon, Goren

2012-05-01

284

Quantum game simulator, using the circuit model of quantum computation  

NASA Astrophysics Data System (ADS)

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.

Vlachos, Panagiotis; Karafyllidis, Ioannis G.

2009-10-01

285

Center for Advanced Computational Technology  

NASA Technical Reports Server (NTRS)

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.

Noor, Ahmed K.

2000-01-01

286

The resource theory of stabilizer quantum computation  

NASA Astrophysics Data System (ADS)

Recent results on the non-universality of fault-tolerant gate sets underline the critical role of resource states, such as magic states, to power scalable, universal quantum computation. Here we develop a resource theory, analogous to the theory of entanglement, that is relevant for fault-tolerant stabilizer computation. We introduce two quantitative measures—monotones—for the amount of non-stabilizer resource. As an application we give absolute bounds on the efficiency of magic state distillation. One of these monotones is the sum of the negative entries of the discrete Wigner representation of a quantum state, thereby resolving a long-standing open question of whether the degree of negativity in a quasi-probability representation is an operationally meaningful indicator of quantum behavior.

Veitch, Victor; Hamed Mousavian, S. A.; Gottesman, Daniel; Emerson, Joseph

2014-01-01

287

Adiabatic quantum computing for random satisfiability problems  

SciTech Connect

The discrete formulation of adiabatic quantum computing is compared with other search methods, classical and quantum, for random satisfiability (SAT) problems. With the number of steps growing only as the cube of the number of variables, the adiabatic method gives solution probabilities close to 1 for problem sizes feasible to evaluate via simulation on current computers. However, for these sizes the minimum energy gaps of most instances are fairly large, so the good performance scaling seen for small problems may not reflect asymptotic behavior where costs are dominated by tiny gaps. Moreover, the resulting search costs are much higher than for other methods. Variants of the quantum algorithm that do not match the adiabatic limit give lower costs, on average, and slower growth than the conventional GSAT heuristic method.

Hogg, Tad [HP Labs, Palo Alto, California 94304 (United States)

2003-02-01

288

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

Microsoft Academic Search

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

C. S. Lent; P. D. Tougaw; W. Porod

1994-01-01

289

Towards a fullerene-based quantum computer  

NASA Astrophysics Data System (ADS)

Molecular structures appear to be natural candidates for a quantum technology: individual atoms can support quantum superpositions for long periods, and such atoms can in principle be embedded in a permanent molecular scaffolding to form an array. This would be true nanotechnology, with dimensions of order of a nanometre. However, the challenges of realizing such a vision are immense. One must identify a suitable elementary unit and demonstrate its merits for qubit storage and manipulation, including input/output. These units must then be formed into large arrays corresponding to an functional quantum architecture, including a mechanism for gate operations. Here we report our efforts, both experimental and theoretical, to create such a technology based on endohedral fullerenes or 'buckyballs'. We describe our successes with respect to these criteria, along with the obstacles we are currently facing and the questions that remain to be addressed.

Benjamin, Simon C.; Ardavan, Arzhang; Briggs, G. Andrew D.; Britz, David A.; Gunlycke, Daniel; Jefferson, John; Jones, Mark A. G.; Leigh, David F.; Lovett, Brendon W.; Khlobystov, Andrei N.; Lyon, S. A.; Morton, John J. L.; Porfyrakis, Kyriakos; Sambrook, Mark R.; Tyryshkin, Alexei M.

2006-05-01

290

Quantum computation with Turaev-Viro codes  

SciTech Connect

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.

Koenig, Robert, E-mail: rkoenig@caltech.ed [Institute for Quantum Information, California Institute of Technology, Pasadena, CA 91125 (United States); Kuperberg, Greg [Department of Mathematics, University of California, Davis, CA 95616 (United States); Reichardt, Ben W. [School of Computer Science, Institute for Quantum Computing, University of Waterloo, Waterloo, ON, N2L 3G1 (Canada)

2010-12-15

291

Semiclassical Fourier Transform for Quantum Computation  

Microsoft Academic Search

It is shown that the Fourier transform preceding the final measurement in Shor's algorithm for factorization on a quantum computer can be carried out in a semiclassical way by using the ``classical'' (macroscopic) signal resulting from measuring one bit to determine the type of measurement carried out on the next bit, and so forth. In this way all the two-bit

Robert B. Griffiths; Chi-Sheng Niu

1996-01-01

292

Bulk Spin-Resonance Quantum Computation  

Microsoft Academic Search

This article presents a new approach to quantum computing based on using bulk samples rather than isolated degrees of freedom. The problem, of course, is that such samples microscopically are in a thermal distribution of states, and it is impractical to hope to cool macroscopic materials to their ground state; furthermore, bulk samples are macroscopic ensembles whose members cannot be

Neil A. Gershenfeld; Isaac L. Chuang

1997-01-01

293

Simulations of Probabilities for Quantum Computing  

NASA Technical Reports Server (NTRS)

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.

Zak, M.

1996-01-01

294

Blind quantum computing with weak coherent pulses.  

PubMed

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 ? blindness for UBQC, in analogy to the concept of ? 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 ?-blind UBQC for any ?>0, even if the channel between the client and the server is arbitrarily lossy. PMID:23003133

Dunjko, Vedran; Kashefi, Elham; Leverrier, Anthony

2012-05-18

295

Blind Quantum Computing with Weak Coherent Pulses  

NASA Astrophysics Data System (ADS)

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 ? blindness for UBQC, in analogy to the concept of ? 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 ?-blind UBQC for any ?>0, even if the channel between the client and the server is arbitrarily lossy.

Dunjko, Vedran; Kashefi, Elham; Leverrier, Anthony

2012-05-01

296

Uncertainty associated with virtual measurements from computational quantum chemistry models  

NASA Astrophysics Data System (ADS)

A value for the measurand determined from a computational model is frequently referred to as a virtual measurement to distinguish it from a physical measurement, which is determined from a laboratory experiment. Any measurement, physical or virtual, is incomplete without a quantitative statement of its associated uncertainty. The science and technology of making physical measurements and quantifying their uncertainties has evolved over many decades. In contrast, the science and technology of making virtual measurements is evolving. We propose an approach for quantifying the uncertainty associated with a virtual measurement of a molecular property determined from a computational quantum chemistry model. The proposed approach is based on the Guide to the Expression of Uncertainty in Measurement, published by the International Organization for Standardization, and it uses the Computational Chemistry Comparison and Benchmark Database maintained by the National Institute of Standards and Technology.

Irikura, Karl K.; Johnson, Russell D., III; Kacker, Raghu N.

2004-12-01

297

Control and Dynamic Approach to Robust Quantum Computing.  

National Technical Information Service (NTIS)

During the entire performance period, from 12 May 2003 through 31 December 2006, we have conducted theoretical and computational research on quantum control problems central to quantum computation. In particular we completed a thorough and rigorous analys...

H. Mabuchi

2006-01-01

298

Quantum computing at the Air Force Research Laboratory Information Directorate (Plenary Paper)  

NASA Astrophysics Data System (ADS)

The Air Force Research Laboratory leads the discovery, development, and integration of affordable war fighting technologies for our air and space forces. In particular, the Information Directorate"s mission is to advance and apply Information Systems Science and Technology to provide Information Dominance. This paper discusses why the Air Force Research Laboratory Information Directorate is concerned with researching prospective computing architectures for Command, Control, Communications, Computers, Intelligence, Surveillance and Reconnaissance applications. Projects addressing quantum information science and quantum computing will be discussed, highlighting where these technologies offer potential disruptive technology solutions for the Air Force.

Drager, Steven L.; Walsh, Lois D.

2005-05-01

299

Scheme for Quantum Computing Immune to Decoherence  

NASA Technical Reports Server (NTRS)

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.

Williams, Colin; Vatan, Farrokh

2008-01-01

300

Infinite possibilities: Computational structures technology  

NASA Technical Reports Server (NTRS)

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.

Beam, Sherilee F.

1994-01-01

301

Measurement-Based and Universal Blind Quantum Computation  

NASA Astrophysics Data System (ADS)

Measurement-based quantum computation (MBQC) is a novel approach to quantum computation where the notion of measurement is the main driving force of computation. This is in contrast with the more traditional circuit model which is based on unitary operation. We review here the mathematical model underlying MBQC and the first quantum cryptographic protocol designed using the unique features of MBQC.

Broadbent, Anne; Fitzsimons, Joseph; Kashefi, Elham

302

A new software-based architecture for quantum computer  

NASA Astrophysics Data System (ADS)

In this paper, we study a reliable architecture of a quantum computer and a new instruction set and machine language for the architecture, which can improve the performance and reduce the cost of the quantum computing. We also try to address some key issues in detail in the software-driven universal quantum computers.

Wu, Nan; Song, Fangmin; Li, Xiangdong

2010-04-01

303

Is quantum computing with solid state devices possible?  

Microsoft Academic Search

Experiments with a few qubits, the basic elements of a quantum computer, using the methods of nuclear magnetic resonance (NMR) have demonstrated that quantum computing is possible. A useful quantum computer would need to use many qubits, while it appears that NMR with molecules is limited to about ten qubits. The easiest way to assemble a large number of qubits

R. W. Keyes

2003-01-01

304

Novel photonic bandgap based architectures for quantum computers and networks  

NASA Astrophysics Data System (ADS)

All of the approaches for quantum information processing have their own advantages, but unfortunately also their own drawbacks. Ideally, one would merge the most attractive features of those different approaches in a single technology. We envision that large-scale photonic crystal (PC) integrated circuits and fibers could be the basis for robust and compact quantum circuits and processors of the next generation quantum computers and networking devices. Cavity QED, solid-state, and (non)linear optical models for computing, and optical fiber approach for communications are the most promising candidates to be improved through this novel technology. In our work, we consider both digital and analog quantum computing. In the digital domain, we first perform gate-level analysis. To achieve this task, we solve the Jaynes-Cummings Hamiltonian with time-dependent coupling parameters under the dipole and rotating-wave approximations for a 3D PC single-mode cavity with a sufficiently high Q-factor. We then exploit the results to show how to create a maximally entangled state of two atoms and how to implement several quantum logic gates: a dual-rail Hadamard gate, a dual-rail NOT gate, and a SWAP gate. In all of these operations, we synchronize atoms, as opposed to previous studies with PCs. The method has the potential for extension to N-atom entanglement, universal quantum logic operations, and the implementation of other useful, cavity QED-based quantum information processing tasks. In the next part of the digital domain, we study circuit-level implementations. We design and simulate an integrated teleportation and readout circuit on a single PC chip. The readout part of our device can not only be used on its own but can also be integrated with other compatible optical circuits to achieve atomic state detection. Further improvement of the device in terms of compactness and robustness is possible by integrating with sources and detectors in the optical regime. In the analog domain, we consider a quantum simulation problem. We show that the Klein paradox for the Klein-Gordon equation of a spin-zero particle manifests exactly the same kind of wave propagation and negative refraction phenomenon as the scattering of a transverse-electric-polarized electromagnetic wave incident on a negative index medium. Using this peculiar feature of negative index materials, we show that real time control and processing of some quantum experiments related with Klein paradox can be achieved by an optoelectronic simulator designed according to certain transformations and approximations.

Guney, Durdu

305

Modular Universal Scalable Ion-trap Quantum Computer (MUSIQC)  

NASA Astrophysics Data System (ADS)

We describe a scalable architecture for general-purpose quantum computation based on trapped ions and photonic interconnect network. The quantum computer is made up of several elementary logic units (ELUs) each containing a modest number of trapped ions representing physical qubits. Each ELU is provided with an optical communication port through which a photon entangled with a communication ion is extracted. Quantum entanglement is distributed between an arbitrary pair of ELUs through a reconfigurable photonic network, which can be utilized to perform two-qubit quantum logic operation between any pair of physical qubits in the entire quantum computer. We show that this architecture can support universal, fault-tolerant quantum computation.

Kim, Jungsang; Maunz, Peter; Kim, Taehyun; Hussman, Jeffrey; Noek, Rachel; Mehta, Abhijit; Monroe, Christopher

2011-10-01

306

Computer Access. Tech Use Guide: Using Computer Technology.  

ERIC Educational Resources Information Center

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…

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

307

QDENSITY—A Mathematica quantum computer simulation  

NASA Astrophysics Data System (ADS)

This Mathematica 6.0 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. New version program summaryProgram title: QDENSITY 2.0 Catalogue identifier: ADXH_v2_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADXH_v2_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.: 26 055 No. of bytes in distributed program, including test data, etc.: 227 540 Distribution format: tar.gz Programming language: Mathematica 6.0 Operating system: Any which supports Mathematica; tested under Microsoft Windows XP, Macintosh OS X, and Linux FC4 Catalogue identifier of previous version: ADXH_v1_0 Journal reference of previous version: Comput. Phys. Comm. 174 (2006) 914 Classification: 4.15 Does the new version supersede the previous version?: Offers an alternative, more up to date, implementation Nature of problem: Analysis and design of quantum circuits, quantum algorithms and quantum clusters. Solution method: 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. Reasons for new version: The package has been updated to make it fully compatible with Mathematica 6.0 Summary of revisions: The package has been updated to make it fully compatible with Mathematica 6.0 Running time: Most examples included in the package, e.g., the tutorial, Shor's examples, Teleportation examples and Grover's search, run in less than a minute on a Pentium 4 processor (2.6 GHz). The running time for a quantum computation depends crucially on the number of qubits employed.

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

2009-03-01

308

Applications of computational quantum mechanics  

NASA Astrophysics Data System (ADS)

This original research dissertation is composed of a new numerical technique based on Chebyshev polynomials that is applied on scattering problems, a phenomenological kinetics study for CO oxidation on RuO2 surface, and an experimental study on methanol coupling with doped metal oxide catalysts. Minimum Error Method (MEM), a least-squares minimization method, provides an efficient and accurate alternative to solve systems of ordinary differential equations. Existing methods usually utilize matrix methods which are computationally costful. MEM, which is based on the Chebyshev polynomials as a basis set, uses the recursion relationships and fast Chebyshev transforms which scale as O(N). For large basis set calculations this provides an enormous computational efficiency in the calculations. Chebyshev polynomials are also able to represent non-periodic problems very accurately. We applied MEM on elastic and inelastic scattering problems: it is more efficient and accurate than traditionally used Kohn variational principle, and it also provides the wave function in the interaction region. Phenomenological kinetics (PK) is widely used in industry to predict the optimum conditions for a chemical reaction. PK neglects the fluctuations, assumes no lateral interactions, and considers an ideal mix of reactants. The rate equations are tested by fitting the rate constants to the results of the experiments. Unfortunately, there are numerous examples where a fitted mechanism was later shown to be erroneous. We have undertaken a thorough comparison between the phenomenological equations and the results of kinetic Monte Carlo (KMC) simulations performed on the same system. The PK equations are qualitatively consistent with the KMC results but are quantitatively erroneous as a result of interplays between the adsorption and desorption events. The experimental study on methanol coupling with doped metal oxide catalysts demonstrates the doped metal oxides as a new class of catalysts with novel properties. Doping a metal oxide may alter its intrinsic properties drastically. A catalytically non-active material can be activated by doping. In this study, we showed that pure zirconia (ZrO2) has almost no activity in methanol coupling reaction, whereas when it is doped with aluminum, the doped catalyst produces dimethyl ether (DME), which is valuable as an alternative future energy source.

Temel, Burcin

309

Fermionic measurement-based quantum computation  

NASA Astrophysics Data System (ADS)

Fermions, as a major class of quantum particles, provide platforms for quantum information processing beyond the possibilities of spins or bosons, which have been studied more extensively. One particularly interesting model to study, in view of recent progress in manipulating ultracold fermion gases, is the fermionic version of measurement-based quantum computation (MBQC), which implements full quantum computation with only single-site measurements on a proper fermionic many-body resource state. However, it is not known which fermionic states can be used as the resource states for MBQC and how to find them. In this paper, we generalize the framework of spin MBQC to fermions. In particular, we provide a general formalism to construct many-body entangled fermion resource states for MBQC based on the fermionic projected entangled pair state representation. We give a specific fermionic state which enables universal MBQC and demonstrate that the nonlocality inherent in fermion systems can be properly taken care of with suitable measurement schemes. Such a framework opens up possibilities of finding MBQC resource states which can be more readily realized in the laboratory.

Chiu, Yu-Ju; Chen, Xie; Chuang, Isaac L.

2013-01-01

310

Geometry, optimal control and quantum computing  

NASA Astrophysics Data System (ADS)

Quantum computation promises solution to problems that are hard to solve by classical computers. The efficient construction of quantum circuits that can solve interesting tasks is a fundamental challenge in the field. Such efficient construction also reduces decoherence losses in physical implementations of quantum algorithms by reducing interaction time with the environment. Therefore, finding time-optimal ways to synthesize unitary transformations from available physical resources is a problem of both fundamental and practical interest in quantum information processing. In this thesis, we study these problems in general mathematical frame as well as in some concrete real physical settings. We give a complete characterization of all the unitary transformations that can be synthesized in a given time for a two-qubit system in presence of general time varying coupling tensor, assuming that the local unitary transformation on two qubits can be performed arbitrarily fast (on a time scale governed by the strength of couplings). A generalization of this result on general Lie group is also presented. We then give the time optimal ways for coherence transfer on three linearly coupled spin chain, and an efficient way of constructing a CNOT gate between two indirectly coupled spins.

Yuan, Haidong

311

Quantum computation: algorithms and implementation in quantum dot devices  

NASA Astrophysics Data System (ADS)

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..

Gamble, John King

312

Non-unitary probabilistic quantum computing circuit and method  

NASA Technical Reports Server (NTRS)

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.

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

2009-01-01

313

Period finding with adiabatic quantum computation  

NASA Astrophysics Data System (ADS)

We outline an efficient quantum-adiabatic algorithm that solves Simon's problem, in which one has to determine the “period”, or xor mask, of a given black-box function. We show that the proposed algorithm is exponentially faster than its classical counterpart and has the same complexity as the corresponding circuit-based algorithm. Together with other related studies, this result supports a conjecture that the complexity of adiabatic quantum computation is equivalent to the circuit-based computational model in a stronger sense than the well-known, proven polynomial equivalence between the two paradigms. We also discuss the importance of the algorithm and its theoretical and experimental implications for the existence of an adiabatic version of Shor's integer factorization algorithm that would have the same complexity as the original algorithm.

Hen, I.

2014-03-01

314

Quantum computation architecture using optical tweezers  

SciTech Connect

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.

Weitenberg, Christof [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748 Garching (Germany); Kuhr, Stefan [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748 Garching (Germany); University of Strathclyde, Department of Physics, SUPA, Glasgow G4 0NG (United Kingdom); Moelmer, Klaus; Sherson, Jacob F. [Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C (Denmark)

2011-09-15

315

Computer technologies and institutional memory  

NASA Technical Reports Server (NTRS)

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.

Bell, Christopher; Lachman, Roy

1989-01-01

316

Integrating computer technology in teacher education  

Microsoft Academic Search

The paper highlights some of the concerns among developing countries to introduce computer technology in teacher education and the nations' classrooms in particular. The arguments in favour hinge on improving quality of education through improvement in quality of teaching and learning processes through the use of computer technology. The paper discusses the use of computer technology in exploring the constructivist

P. Moorgawa

317

Universal quantum gates for Single Cooper Pair Box based quantum computing  

NASA Technical Reports Server (NTRS)

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.

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

2000-01-01

318

The Role of Classical Computation in Measurement-Based Quantum Computation  

Microsoft Academic Search

Measurement-based quantum computation (MBQC) is an important model of quantum computation, which has delivered both new insights\\u000a and practical advantages. In measurement-based quantum computation, more specifically the “one-way model” of computation,\\u000a the computation proceeds in the following way. A large number of quantum bits (qubits) are prepared in a special entangled\\u000a state called a cluster state. The qubits are then

Dan Browne; Janet Anders

2008-01-01

319

Computer Technology and Architecture: An Evolving Interaction  

Microsoft Academic Search

The interaction between computer architecture and IC technology is examined. To evaluate the attractiveness of particular technologies, computer designs are assessed primarily on the basis of performance and cost. The focus is mainly on CPU performance, both because it is easier to measure and because the impact of technology is most easily seen in the CPU. The technology trends discussed

John L. Hennessy; Norman P. Jouppi

1991-01-01

320

Quantum Cellular Automata: Computing with Quantum Dot Molecules  

NASA Astrophysics Data System (ADS)

A new quantum computing architecture, quantum cellular automata, is studied. Quantum cellular automata (QCA's) are composed of interacting quantum dot molecules, each of which contains two electrons. Repulsion between these two electrons causes these molecules to exhibit bistable behavior, which allows the encoding of binary information directly in the quantum state of each cell. QCA's take advantage of "computing with the ground state", in which dissipation acts to drive the system to the ground state corresponding to the applied boundary conditions. By carefully designing the geometric layout of arrays of these quantum dot molecules, it is possible to perform useful calculations with these ground state alignments. The logic primitive of such a system is a majority logic gate, which can be reduced to act as either an AND gate or an OR gate. Due to the local nature of the Coulombic interaction between cells, it is possible to use hierarchical design rules to combine these elements into more complicated logic devices. Since the interactions between cells are purely Coulombic, no direct interconnections are necessary between QCA cells. In addition, energy is only supplied at the edge of the system when an input cell is switched, so QCA's can be said to be truly edge-driven. Such an edge-driven system will eliminate many of the fabrication challenges present in systems with complicated interconnection requirements. Although the results of a ground-state calculation do not rely on the exact nature of the system dynamics, these dynamics do provide an estimate of the switching speed of QCA devices. We have developed several approximate techniques for the modeling of this very complicated system and have obtained estimates on the intrinsic switching speed of both semiconductor-based cells and macro-molecular cells. As expected, the macro-molecular cells exhibit greatly improved performance over the larger semiconductor cells. An alternative to abrupt switching of QCA arrays takes advantage of the adiabatic theorem to guarantee that the system will always remain in its instantaneous ground state. Such adiabatic switching has several advantages over abrupt switching, the most important of which is avoidance of metastable states.

Tougaw, Paul Douglas

321

Hard chaos, quantum billiards, and quantum dot computers  

SciTech Connect

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.

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

1996-07-01

322

Effect of Coulomb Interaction on GaAs Quantum Computer Performance.  

National Technical Information Service (NTIS)

Interaction between the quantum bits strongly limits quantum computer performance while using large quantum registers. We investigated influence of such interaction for recently proposed quantum computer based on GaAs quantum dots with built-in barrier. O...

L. Fedichkin, M. Yanchenko

2001-01-01

323

A device architecture for computing with quantum dots  

Microsoft Academic Search

We describe a paradigm for computing with interacting quantum dots, quantum-dot cellular automata (QCA). We show how arrays of quantum-dot cells could be used to perform useful computations. A new adiabatic switching paradigm is developed which permits clocked control, eliminates metastability problems, and enables a pipelined architecture

CRAIG S. LENT; P. DOUGLAS TOUGAW

1997-01-01

324

Computing with Quantum-dot Cellular Automata: Adiabatic Switching  

Microsoft Academic Search

We describe a paradigm for computing with interacting quantum dots, quantum-dot cellular automata (QCA). We show how arrays of quantum-dot cells could be used to perform useful computations. A new adiabatic switching scheme is developed which permits clocked control, eliminates metastability problems, and enables a pipelined architecture. We discuss implementation in semiconductor and metallic tunnel-junction systems.

Craig S. Lent; P. Douglas Tougaw; Weiwen Weng; Yuriy Brazhnik

1997-01-01

325

Fault-tolerant quantum computation with constant error  

Microsoft Academic Search

In the past year many developments had taken place in the area of quantum error corrections. Recently Shor showed how to perform fault tolerant quantum computation when, ?, the probability for a fault in one time step per qubit or per gate, is logarithmically small. This paper improves this bound and shows how to perform fault tolerant quantum computation when

Dorit Aharonov; Michael Ben-Or

1997-01-01

326

Orthologic and quantum logic: models and computational elements  

Microsoft Academic Search

Motivated by a growing need to understand the computational potential of quantum devices we suggest an approach to the relevant issues via quantum logic and its model theory. By isolating such notions as quantum parallelism and interference within a model-theoretic setting, quite divorced from their customary physical trappings, we seek to lay bare their logical underpinnings and possible computational ramifications.In

J. P. Rawling; S. A. Selesnick

2000-01-01

327

Hybrid architecture for encoded measurement-based quantum computation  

PubMed Central

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.

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

2014-01-01

328

Hybrid architecture for encoded measurement-based quantum computation.  

PubMed

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

Zwerger, M; Briegel, H J; Dür, W

2014-01-01

329

Computer Technology-infused Learning Enhancement  

Microsoft Academic Search

The purpose of the study was to determine students’ perception of instructional integration of computer technology to improve\\u000a learning. Two key questions were investigated in this study: (a) What is the students’ perception of faculty integration of\\u000a computer technology into classroom instruction? (b) To what extent does the students’ perception of faculty integration of\\u000a computer technology, students’ computer proficiency levels

Jared Keengwe; Longy O. Anyanwu

2007-01-01

330

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

NASA Astrophysics Data System (ADS)

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.

Howard, Mark; Vala, Jiri

2012-02-01

331

Quantum computing with atomic Josephson junction arrays  

SciTech Connect

We present a quantum computing scheme with atomic Josephson junction arrays. The system consists of a small number of atoms with three internal states and trapped in a far-off-resonant optical lattice. Raman lasers provide the 'Josephson' tunneling, and the collision interaction between atoms represent the 'capacitive' couplings between the modes. The qubit states are collective states of the atoms with opposite persistent currents. This system is closely analogous to the superconducting flux qubit. Single-qubit quantum logic gates are performed by modulating the Raman couplings, while two-qubit gates result from a tunnel coupling between neighboring wells. Readout is achieved by tuning the Raman coupling adiabatically between the Josephson regime to the Rabi regime, followed by a detection of atoms in internal electronic states. Decoherence mechanisms are studied in detail promising a high ratio between the decoherence time and the gate operation time.

Tian Lin; Zoller, P. [Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck (Austria)

2003-10-01

332

Robust logic gates and realistic quantum computation  

SciTech Connect

The composite rotation approach has been used to develop a range of robust quantum logic gates, including single qubit gates and two qubit gates, which are resistant to systematic errors in their implementation. Single qubit gates based on the BB1 family of composite rotations have been experimentally demonstrated in a variety of systems, but little study has been made of their application in extended computations, and there has been no experimental study of the corresponding robust two qubit gates to date. Here we describe an application of robust gates to nuclear magnetic resonance studies of approximate quantum counting. We find that the BB1 family of robust gates is indeed useful, but that the related NB1, PB1, B4, and P4 families of tailored logic gates are less useful than initially expected.

Xiao Li; Jones, Jonathan A. [Centre for Quantum Computation, Clarendon Laboratory, University of Oxford, Parks Road, OX1 3PU (United Kingdom)

2006-03-15

333

Center for Computational Structures Technology  

NASA Technical Reports Server (NTRS)

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.

Noor, Ahmed K.; Perry, Ferman W.

1995-01-01

334

Minimal computational-space implementation of multiround quantum protocols  

SciTech Connect

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.

Bisio, Alessandro; D'Ariano, Giacomo Mauro; Perinotti, Paolo; Chiribella, Giulio [QUIT group, Dipartimento di Fisica ''A. Volta'', and INFN Sezione di Pavia, via Bassi 6, IT-27100 Pavia (Italy); Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Waterloo, Ontario N2L 2Y5 (Canada)

2011-02-15

335

Experimental one-way quantum computation using linear optics  

NASA Astrophysics Data System (ADS)

Standard quantum computation is based on a universal set of unitary quantum logic gates which process qubits. In contrast to the standard quantum model, Raussendorf and Briegel proposed the one-way quantum computer, based on a highly-entangled cluster state, which is entirely different. We have experimentally realized four-qubit cluster states encoded into the polarization state of four photons. We fully characterize the quantum state by implementing the first experimental four-qubit quantum state tomography. Using this cluster state we demonstrate the feasibility of one-way quantum computing through a universal set of one- and two-qubit operations. Finally, our implementation of Grover's search algorithm demonstrates that one-way quantum computation is ideally suited for such tasks.

Walther, Philip; Resch, Kevin; Rudolph, Terry; Schenck, Emmanuel; Weinfurter, Harald; Vedral, Vlatko; Aspelmeyer, Markus; Zeilinger, Anton

2006-03-01

336

Quantum Computers Can Search Rapidly by Using Almost Any Transformation  

Microsoft Academic Search

A quantum computer has a clear advantage over a classical computer for\\u000aexhaustive search. The quantum mechanical algorithm for exhaustive search was\\u000aoriginally derived by using subtle properties of a particular quantum\\u000amechanical operation called the Walsh-Hadamard (W-H) transform. This paper\\u000ashows that this algorithm can be implemented by replacing the W-H transform by\\u000aalmost any quantum mechanical operation. This

Lov K. Grover

1998-01-01

337

Measurement-based quantum computation with trapped ions.  

PubMed

Measurement-based quantum computation represents a powerful and flexible framework for quantum information processing, based on the notion of entangled quantum states as computational resources. The most prominent application is the one-way quantum computer, with the cluster state as its universal resource. Here we demonstrate the principles of measurement-based quantum computation using deterministically generated cluster states, in a system of trapped calcium ions. First we implement a universal set of operations for quantum computing. Second we demonstrate a family of measurement-based quantum error correction codes and show their improved performance as the code length is increased. The methods presented can be directly scaled up to generate graph states of several tens of qubits. PMID:24313469

Lanyon, B P; Jurcevic, P; Zwerger, M; Hempel, C; Martinez, E A; Dür, W; Briegel, H J; Blatt, R; Roos, C F

2013-11-22

338

Computer Technology Program (REACT). Technical Report.  

ERIC Educational Resources Information Center

Development work of the Computer Technology Program (or REACT-Relevant Educational Applications of Computer Technology) during the period of July 1, 1971 to August 31, 1972 is summarized here. Work during this period included writing and developmental testing of a course in computer careers for high school pupils. This phase took the course…

Otte, Richard

339

Advanced laptop and small personal computer technology  

NASA Technical Reports Server (NTRS)

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.

Johnson, Roger L.

1991-01-01

340

From Cbits to Qbits: Teaching computer scientists quantum mechanics  

NASA Astrophysics Data System (ADS)

A strategy is suggested for teaching mathematically literate students, with no background in physics, just enough quantum mechanics for them to understand and develop algorithms in quantum computation and quantum information theory. Although the article as a whole addresses teachers of physics well versed in quantum mechanics, the central pedagogical development is addressed directly to computer scientists and mathematicians, with only occasional asides to their teacher. Physicists uninterested in quantum pedagogy may be amused (or irritated) by some of the views of standard quantum mechanics that arise naturally from this unorthodox perspective.

Mermin, N. David

2003-01-01

341

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

ScienceCinema

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.

342

Methods for scalable optical quantum computation  

NASA Astrophysics Data System (ADS)

We propose a scalable method for implementing linear optics quantum computation using the "linked-state" approach. Our method avoids the two-dimensional spread of errors occurring in the preparation of the linked-state. Consequently, a proof is given for the scalability of this modified linked-state model, and an exact expression for the efficiency of the method is obtained. Moreover, a considerable improvement in the efficiency is achieved. The proposed method is applicable to the "cluster-state" approach as well.

Mor, Tal; Yoran, Nadav

2005-05-01

343

Methods for Scalable Optical Quantum Computation  

NASA Astrophysics Data System (ADS)

We propose a scalable method for implementing linear optics quantum computation using the “linked-state” approach. Our method avoids the two-dimensional spread of errors occurring in the preparation of the linked state. Consequently, a proof is given for the scalability of this modified linked-state model, and an exact expression for the efficiency of the method is obtained. Moreover, a considerable improvement in the efficiency, relative to the original linked-state method, is achieved. The proposed method is applicable to Nielsen’s optical “cluster-state” approach as well.

Mor, Tal; Yoran, Nadav

2006-09-01

344

QCWAVE - A Mathematica quantum computer simulation update  

NASA Astrophysics Data System (ADS)

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 n 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. Program summaryProgram title: QCWAVE Catalogue identifier: ADXH_v3_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADXH_v3_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.: 94 159 No. of bytes in distributed program, including test data, etc.: 734 158 Distribution format: tar.gz Programming language: Mathematica 7.0 and 8.0. Computer: Any supporting Mathematica. Operating system: Any operating system that supports Mathematica; tested under Microsoft Windows XP, Macintosh OSX, and Linux FC4. Has the code been vectorised or parallelized?: Utilises Mathematica's (7.0 and 8.0) parallel computing features. Classification: 4.15. Catalogue identifier of previous version: ADXH_v2_0 Journal reference of previous version: Comput. Phys. Comm. 180 (2009) 474. Does the new version supersede the previous version?: Yes. This version supersedes all prior versions of QDENSITY. Nature of problem: Simulation of quantum circuits, quantum algorithms, noise and quantum error correction. Solution method: A Mathematica package containing commands to create and analyze quantum circuits is upgraded and extended, with emphasis on state amplitudes. Several Mathematica notebooks containing relevant examples are explained in detail. The parallel computing feature of Mathematica is used to develop a multiverse approach for including noise and forming suitable ensemble averaged density matrix evolution. Error correction is simulated. Reasons for new version: The new version updates QDENSITY to run on Mathematica 7.0 and 8.0 and makes it compatible with our extension QCWAVE. QCWAVE emphasizes wavefunctions with efficient gate operations and also extends the code to use the parallel computing features of Mathematica 7.0-8.0. Circuit diagram an

Tabakin, Frank; Juliá-Díaz, Bruno

2011-08-01

345

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

NASA Astrophysics Data System (ADS)

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.

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

2013-01-01

346

Coherent ultrafast optical manipulations of semi-conductor quantum dots for quantum computation  

Microsoft Academic Search

Coherent optically driven semiconductor quantum dot systems are proposed for the implementation of quantum information processing devices. Fundamental quantum computation units, the quantum bits (qubits), are realized and optically manipulated in the exciton and spin bases. In this thesis, consecutive phase-sensitive rotations of a single qubit and their importance in the measurement of the full physical density matrix have been

Yanwen Wu

2008-01-01

347

Adiabatic Quantum Computation with Neutral Atoms  

NASA Astrophysics Data System (ADS)

We are implementing a new platform for adiabatic quantum computation (AQC)footnotetext E. Farhi, et al. Science 292, 472 (2000) based on trapped neutral atoms whose coupling is mediated by the dipole-dipole interactions of Rydberg states. Ground state cesium atoms are dressed by laser fields in a manner conditional on the Rydberg blockade mechanism,footnotetextS. Rolston, et al. Phys. Rev. A, 82, 033412 (2010)^,footnotetextT. Keating, et al. arXiv:1209.4112 (2012) thereby providing the requisite entangling interactions. As a benchmark we study a Quadratic Unconstrained Binary Optimization (QUBO) problem whose solution is found in the ground state spin configuration of an Ising-like model.[4pt] In collaboration with Lambert Parazzoli, Sandia National Laboratories; Aaron Hankin, Center for Quantum Information and Control (CQuIC), University of New Mexico; James Chin-Wen Chou, Yuan-Yu Jau, Peter Schwindt, Cort Johnson, and George Burns, Sandia National Laboratories; Tyler Keating, Krittika Goyal, and Ivan Deutsch, Center for Quantum Information and Control (CQuIC), University of New Mexico; and Andrew Landahl, Sandia National Laboratories.

Biedermann, Grant

2013-03-01

348

QDENSITY—A Mathematica Quantum Computer simulation  

NASA Astrophysics Data System (ADS)

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.

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

2006-06-01

349

Topological quantum computing with only one mobile quasiparticle.  

PubMed

In a topological quantum computer, universal quantum computation is performed by dragging quasiparticle excitations of certain two dimensional systems around each other to form braids of their world lines in 2 + 1 dimensional space-time. In this Letter we show that any such quantum computation that can be done by braiding n identical quasiparticles can also be done by moving a single quasiparticle around n - 1 other identical quasiparticles whose positions remain fixed. PMID:16606068

Simon, S H; Bonesteel, N E; Freedman, M H; Petrovic, N; Hormozi, L

2006-02-24

350

Is quantum computing with solid state devices possible?  

Microsoft Academic Search

.   Experiments with a few qubits, the basic elements of a quantum computer, using the methods of nuclear magnetic resonance (NMR)\\u000a have demonstrated that quantum computing is possible. A useful quantum computer would need to use many qubits, while it appears\\u000a that NMR with molecules is limited to about ten qubits. The easiest way to assemble a large number of

R. W. Keyes

2003-01-01

351

Computer Technology: State of the Art.  

ERIC Educational Resources Information Center

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)

Withington, Frederic G.

1981-01-01

352

Measurement-only topological quantum computation via anyonic interferometry  

SciTech Connect

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.

Bonderson, Parsa [Microsoft Research, Station Q, Elings Hall, University of California, Santa Barbara, CA 93106 (United States)], E-mail: parsab@microsoft.com; Freedman, Michael [Microsoft Research, Station Q, Elings Hall, University of California, Santa Barbara, CA 93106 (United States)], E-mail: michaelf@microsoft.com; Nayak, Chetan [Microsoft Research, Station Q, Elings Hall, University of California, Santa Barbara, CA 93106 (United States); Department of Physics, University of California, Santa Barbara, CA 93106 (United States)], E-mail: nayak@kitp.ucsb.edu

2009-04-15

353

Stable Isotopes, Quantum Computing and Consciousness  

NASA Astrophysics Data System (ADS)

Recent proposals of quantum computing/computers (QC) based on nuclear spins suggest that consciousness (CON) activity may be related (assisted) to subset of C13 atoms incorporated randomly, or quasirandomly, in neural structures. Consider two DNA chains. Even if they are completely identical chemically (same sequence of codons), patterns of 12C and 13C isotopes in them are different (possible origin of personal individuality). Perhaps it is subsystem of nuclear spins of 13C "sublattice" which forms dynamical system capable of QC and on which CON is "spanned". Some issues related to this hypothesis are: (1) existence of CON-driven positional correlations among C13 atoms, (2) motion (hopping) of C13 via enhanced neutron tunneling, cf. quantum "anti Zeno-effect", (3) possible optimization of concentration of QC-active C13 atoms above their standard isotopic abundance, (4) characteristic time-scales for operation of C13-based QC (perrhaps, broad range of scales), (5) reflection of QC dynamics of C13 on CON, (6) possibility that C13-based QC operates "above" level of "regular" CON (perhaps, Jungian sub/super-CON), (7) isotopicity as connector to universal Library of Patterns ("Platonic World"), (8) self-stabilization of coherence in C13 (sub)system. Some of this questions are, in principle, experimentally addressable through shifting of isotopic abundances.

Berezin, Alexander A.

2000-10-01

354

Algorithmic cooling and scalable NMR quantum computers  

PubMed Central

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.

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

2002-01-01

355

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

NASA Astrophysics Data System (ADS)

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

Demming, Anna

2012-07-01

356

Quantum computing with Josephson junction circuits  

NASA Astrophysics Data System (ADS)

This work concerns the study of Josephson junction circuits in the context of their usability for quantum computing. The zero-voltage state of a current-biased Josephson junction has a set of metastable quantum energy levels. If a junction is well isolated from its environment, it will be possible to use the two lowest states as a qubit in a quantum computer. I first examine the meaning of isolation theoretically. Using a master equation, I analyzed the effect of dissipation on escape rates and suggested a simple method, population depletion technique, to measure the relaxation time (T1). Using a stochastic Bloch equation to analyze the dependence of microwave resonance peak width on current noise, I found decoherence due to current noise depends on the noise spectrum. For high frequency noise with a cutoff frequency fc much larger than 1/T1, I found decoherence due to noise can be described by a dephasing rate that is proportional to the noise spectral density. However, for low frequency noise such that its cutoff frequency fc is much smaller than 1/T 1, decoherence due to noise depends on the total rms current noise. I then analyze and test a few qubit isolation schemes, including resistive isolation, inductor-capacitor (LC) isolation, half-wavelength resonant isolation and inductor-junction (LJ) isolation. I found the resistive isolation scheme has a severe heating problem. Macroscopic quantum tunneling and energy level quantization were observed in the LC isolated Nb/AlOx/Nb and AL/ALOx/Al junction qubits at 25 mK. Relaxation times of 4--12 ns and spectroscopic coherence times of 1--3 ns were obtained for these LC isolated qubits. I found the half-wavelength isolated junction qubit has a relaxation time of about 20 ns measured by the population-depletion techniques, but no energy levels were observed in this qubit. Experimental results suggest the LJ isolated qubit has a longer relaxation and coherence times than all my previously examined samples. Using a microwave pulse technique, a relaxation time of 50 ns was measured on this sample, the spectroscopic coherence time obtained using continuous microwave pumping is about 5--8 ns. Coherent quantum oscillations (Rabi oscillations) were also observed on this sample with a decay time of around 10 ns for a |0 >? |1 > level spacing of 7.6 GHz. The relaxation times are much smaller than what I would expect from my designs for all isolation schemes. Possible reasons for this inconsistency were discussed. Using microwave spectroscopy techniques, I probed quantum phenomena in a coupled macroscopic three-qubit system that is comprised of two Nb/AlOx/Nb Josephson junctions and an LC resonator. The measured spectrum at 25 mK in the frequency range 4--15 GHz agrees well with quantum mechanical calculations, consistent with the existence of entangled states between the three degrees of freedom. These entangled states and a first-order strong coupling between two junction qubits open the possibility of using a resonator as a data bus for information storage and manipulation in a multi-qubit system. The measurements also demonstrate spectroscopy is a powerful tool and can be used to study a composite system with many qubits.

Xu, Huizhong

357

Introduction to models of quantum computation and quantum programming languages  

Microsoft Academic Search

The goal of this report is to provide an introduction to the basic\\u000acomputational models used in quantum information theory. We various review\\u000amodels of quantum Turing machine, quantum circuits and quantum random access\\u000amachine (QRAM) along with their classical counterparts. We also provide an\\u000aintroduction to quantum programming languages, which are developed using the\\u000aQRAM model. We review the

Jaroslaw Adam Miszczak

2010-01-01

358

Quantum Computing in Condensed Matter Systems.  

National Technical Information Service (NTIS)

Specific theoretical calculations of Hamiltonians corresponding to several quantum logic gates, including the NOT gate, quantum signal splitting, and quantum copying, were obtained and prepared for publication. Directions for future work have been identif...

V. Privman

1997-01-01

359

Preparing Projected Entangled Pair States on a Quantum Computer  

NASA Astrophysics Data System (ADS)

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 PEPS’s parent Hamiltonian.

Schwarz, Martin; Temme, Kristan; Verstraete, Frank

2012-03-01

360

Preparing projected entangled pair states on a quantum computer.  

PubMed

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 PEPS's parent Hamiltonian. PMID:22540445

Schwarz, Martin; Temme, Kristan; Verstraete, Frank

2012-03-16

361

A theory of computation based on quantum logic (I)  

Microsoft Academic Search

Summary form only given. The (meta) logic underlying classical theory of computation is Boolean (two-valued) logic. Quantum logic was proposed by Birkhoff and von Neumann as a logic of quantum mechanics. It is currently understood as a logic whose truth values are taken from an orthomodular lattice. The major difference between Boolean logic and quantum logic is that the latter

Mingsheng Ying

2005-01-01

362

Quantum computation in semiconductor quantum dots of electron-spin asymmetric anisotropic exchange  

SciTech Connect

The universal quantum computation is obtained when there exists asymmetric anisotropic exchange between electron spins in coupled semiconductor quantum dots. The asymmetric Heisenberg model can be transformed into the isotropic model through the control of two local unitary rotations for the realization of essential quantum gates. The rotations on each qubit are symmetrical and depend on the strength and orientation of asymmetric exchange. The implementation of the axially symmetric local magnetic fields can assist the construction of quantum logic gates in anisotropic coupled quantum dots. This proposal can efficiently use each physical electron spin as a logical qubit in the universal quantum computation.

Hao Xiang; Zhu Shiqun [School of Physical Science and Technology, Suzhou University, Suzhou, Jiangsu 215006 (China)

2007-10-15

363

Moral Responsibility and Computer Technology.  

ERIC Educational Resources Information Center

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…

Friedman, Batya

364

Prior Computer Experience and Technology Acceptance  

ERIC Educational Resources Information Center

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…

Varma, Sonali

2010-01-01

365

Computer Technology and Education: A Policy Delphi.  

ERIC Educational Resources Information Center

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…

Steier, Lloyd P.

366

Quantum lattice-gas model for computational fluid dynamics.  

PubMed

Quantum-computing ideas are applied to the practical and ubiquitous problem of fluid dynamics simulation. Hence, this paper addresses two separate areas of physics: quantum mechanics and fluid dynamics (or specifically, the computational simulation of fluid dynamics). The quantum algorithm is called a quantum lattice gas. An analytical treatment of the microscopic quantum lattice-gas system is carried out to predict its behavior at the mesoscopic scale. At the mesoscopic scale, a lattice Boltzmann equation with a nonlocal collision term that depends on the entire system wave function, governs the dynamical system. Numerical results obtained from an exact simulation of a one-dimensional quantum lattice model are included to illustrate the formalism. A symbolic mathematical method is used to implement the quantum mechanical model on a conventional workstation. The numerical simulation indicates that classical viscous damping is not present in the one-dimensional quantum lattice-gas system. PMID:11308976

Yepez, J

2001-04-01

367

QCMPI: A parallel environment for quantum computing  

NASA Astrophysics Data System (ADS)

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 Schrödinger 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.

Tabakin, Frank; Juliá-Díaz, Bruno

2009-06-01

368

Fault-Tolerant Quantum Computation with Higher-Dimensional Systems  

Microsoft Academic Search

Instead of a quantum computer where the fundamental units are 2-dimensional qubits, we can consider a quantum computer made up of d-dimensional systems. There is a straightforward generalization of the class of stabilizer codes to d-dimensional systems, and I will discuss the theory of fault-tolerant computation using such codes. I prove that uni- versal fault-tolerant computation is possible with any

Daniel Gottesman

1998-01-01

369

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

SciTech Connect

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

O'Brien, J. L. (Jeremy L.); Schofield, S. R. (Steven R.); Simmons, M. Y. (Michelle Y.); Clark, R. G. (Robert G.); Dzurak, A. S. (Andrew S.); Curson, N. J. (Neil J.); Kane, B. E. (Bruce E.); McAlpine, N. S. (Neal S.); Hawley, M. E. (Marilyn E.); Brown, G. W. (Geoffrey W.)

2001-01-01

370

Algorithms for Quantum Computation: Discrete Log and Factoring (Extended Abstract)  

Microsoft Academic Search

Peter W. ShorAT&T Bell LabsRoom 2D-149600 Mountain Ave.Murray Hill, NJ 07974 USAemail: shor@research.att.comAbstractThis paper gives algorithms for the discrete log and the factoring problems thattake random polynomial time on a quantum computer (thus giving the first examplesof quantum cryptanalysis).1 IntroductionSince the discovery of quantum mechanics, people have found the behavior of the laws ofprobability in quantum mechanics counterintuitive. Because of

Peter W. Shor

1994-01-01

371

Quantum computing and a unified approach to fast unitary transforms  

Microsoft Academic Search

A quantum computer directly manipulates information stored in the state of quantum mechanical systems. The available operations have many attractive features but also underly severe restrictions, which complicate the design of quantum algorithms. We present a divide-and-conquer approach to the design of various quantum algorithms. The class of algorithm includes many transforms which are well-known in classical signal processing applications.

Sos S. Agaian; Andreas Klappenecker

2002-01-01

372

Anharmonic properties of the vibrational quantum computer.  

PubMed

We developed an efficient approach to study the coherent control of vibrational state-to-state transitions. The approximations employed in our model are valid in the regime of the low vibrational excitation specific to the vibrational quantum computer. Using this approach we explored how the vibrational properties of a two-qubit system affect the accuracy of subpicosecond quantum gates. The optimal control theory and numerical propagation of laser-driven vibrational wave packets were employed. The focus was on understanding the effect of the three anharmonicity parameters of the system. In the three-dimensional anharmonicity parameter space we identified several spots of high fidelity separated by low fidelity planar regions. The seemingly complicated picture is explained in terms of interferences between different state-to-state transitions. Very general analytic relationships between the anharmonicity parameters and the frequencies are derived to describe the observed features. Geometrically, these expressions represent planes in the three-dimensional anharmonicity parameter space. Results of this work should help to choose a suitable candidate molecule for the practical implementation of the vibrational two-qubit system. PMID:17552749

Zhao, Meiyu; Babikov, Dmitri

2007-05-28

373

Number Partitioning via Quantum Adiabatic Computation  

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

374

Optically Controlled Quantum Dot Spins for Scaleable Quantum Computing.  

National Technical Information Service (NTIS)

The objective of this program has been to work towards development of spin based quantum dots for optically driven quantum information processing. Using a combination of ultrahigh resolution laser spectroscopy to study the physics of the dots and ultrafas...

D. G. Steel

2005-01-01

375

Adiabatic Quantum Computing and Quantum Walks: Algorithms and Architectures.  

National Technical Information Service (NTIS)

During the period of this grant, there were a many significant results on quantum adiabatic algorithms and quantum walks. On the adiabatic front, there were papers showing how to design error correcting codes specifically for these Hamiltonian based algor...

E. Farhi

2011-01-01

376

Algorithms for Quantum Computation: Discrete Logarithms and Factoring  

Microsoft Academic Search

A computer is generally considered to be a universalcomputational device; i.e., it is believed able to simulateany physical computational device with a increase in computationtime of at most a polynomial factor. It is notclear whether this is still true when quantum mechanics istaken into consideration. Several researchers, starting withDavid Deutsch, have developed models for quantum mechanicalcomputers and have investigated their

Peter W. Shor

1994-01-01

377

The Brain Is both Neurocomputer and Quantum Computer  

ERIC Educational Resources Information Center

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…

Hameroff, Stuart R.

2007-01-01

378

Bulk Quantum Computation with Nuclear Magnetic Resonance: Theory and Experiment  

Microsoft Academic Search

We show that quantum computation is possible with mixed states instead of pure states as inputs. This is performed by embedding within the mixed state a subspace that transforms like a pure state and that can be identi ed by labeling it based on logical (spin), temporal, or spatial degrees of freedom. This permits quantum computation to be realized with

Isaac L. Chuang; Neil Gershenfeld; Mark G. Kubinec; Debbie W. Leung

1969-01-01

379

An introduction to quantum computing for non-physicists  

Microsoft Academic Search

integers. In quantum systems, the computational space increases exponentially with the size of the system, which enables exponential parallelism. This parallelism could lead to exponentially faster quantum algorithms than possible classically. The catch is that accessing the results, which requires measurement, proves tricky and requires new nontraditional programming techniques. The aim of this paper is to guide computer scientists through

Eleanor G. Rieffel; Wolfgang Polak

2000-01-01

380

Scalable quantum computation via local control of only two qubits  

SciTech Connect

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.

Burgarth, Daniel [IMS and QOLS, Imperial College, London SW7 2PG (United Kingdom); Advanced Science Institute, Institute of Physical and Chemical Research (RIKEN), Wako-shi, Saitama 351-0198 (Japan); Maruyama, Koji [Advanced Science Institute, Institute of Physical and Chemical Research (RIKEN), Wako-shi, Saitama 351-0198 (Japan); Murphy, Michael; Montangero, Simone [Institut fuer Quanteninformationsverarbeitung, Universitaet Ulm, D-89069 Ulm (Germany); Calarco, Tommaso [Institut fuer Quanteninformationsverarbeitung, Universitaet Ulm, D-89069 Ulm (Germany); European Centre for Theoretical Studies in Nuclear Physics and Related Areas, I-38050 Villazzano (Italy); Nori, Franco [Advanced Science Institute, Institute of Physical and Chemical Research (RIKEN), Wako-shi, Saitama 351-0198 (Japan); Physics Department, University of Michigan, Ann Arbor, Michigan 48109 (United States); Plenio, Martin B. [IMS and QOLS, Imperial College, London SW7 2PG (United Kingdom); Institut fuer Theoretische Physik, Universitaet Ulm, D-89069 Ulm (Germany)

2010-04-15

381

Non-Abelian anyons and topological quantum computation  

NASA Astrophysics Data System (ADS)

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.

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

2008-07-01

382

3D Measurement Technologies for Computer Animation  

Microsoft Academic Search

This paper surveys 3D measurement technologies for computer animation and considers unsolved problems on this subject. 3D measurement technologies are actually very important for converting various 3D objects in the real world to 3D models in the virtual world for computer animation. Current 3D measurement technologies have been developed mainly for measuring objects in industrial or scientific fields, such as

Yasuhito Suenaga

1996-01-01

383

Evaluating Campus Computing Services: Taming the Technology.  

ERIC Educational Resources Information Center

Evaluation of campus computer services has been limited by the ability of higher education administrators to relate their experience in evaluating other, more traditional services to the technical complexity of computing services. The explosive growth of computer technologies requires development of a common framework for their evaluation. (MSE)

Gillespie, Robert G.

1987-01-01

384

On the way to creation of materials for quantum computers  

NASA Astrophysics Data System (ADS)

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.

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

2012-02-01

385

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

PubMed

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

Luo, Ming-Xing; Wang, Xiaojun

2014-01-01

386

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

PubMed Central

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.

Luo, Ming-Xing; Wang, Xiaojun

2014-01-01

387

Cluster State Quantum Computation and the Repeat-Until Scheme  

NASA Astrophysics Data System (ADS)

Cluster state computation or the one way quantum computation (1WQC) relies on an initially highly entangled state (called a cluster state) and an appropriate sequence of single qubit measurements along different directions, together with feed-forward based on the measurement results, to realize a quantum computation process. The final result of the computation is obtained by measuring the last remaining qubits in the computational basis. In this short tutorial on cluster state quantum computation, we will also describe the basic ideas of a cluster state and proceed to describe how a single qubit operation can be done on a cluster state. Recently, we proposed a repeat-until-success (RUS) scheme that could effectively be used to realize one-way quantum computer on a hybrid system of photons and atoms. We will briefly describe this RUS scheme and show how it can be used to entangled two distant stationary qubits.

Kwek, L. C.

388

Education & Technology: Reflections on Computing in Classrooms.  

ERIC Educational Resources Information Center

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…

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

389

From Computer Lab to Technology Class.  

ERIC Educational Resources Information Center

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…

Sherwood, Sandra

1999-01-01

390

When Computer Technologies Meet the Learning Sciences  

Microsoft Academic Search

This article explores how insights from the learning sciences can guide the effective use of computer technologies to promote learning and how these technologies make new types of learning opportunities possible. The discussion is organized to provide three illustrations of how the introduction of new technologies can have “ripple effects” that influence many different aspects of the teaching and learning

John Bransford; Sean Brophy; Susan Williams

2000-01-01

391

Emergence of quantum chaos in the quantum computer core and how to manage it  

PubMed

We study the standard generic quantum computer model, which describes a realistic isolated quantum computer with fluctuations in individual qubit energies and residual short-range interqubit couplings. It is shown that in the limit where the fluctuations and couplings are small compared to the one-qubit energy spacing, the spectrum has a band structure, and a renormalized Hamiltonian is obtained which describes the eigenstate properties inside one band. Studies are concentrated on the central band of the computer ("core") with the highest density of states. We show that above a critical interqubit coupling strength, quantum chaos sets in, leading to a quantum ergodicity of the computer eigenstates. In this regime the ideal qubit structure disappears, the eigenstates become complex, and the operability of the computer is quickly destroyed. We confirm that the quantum chaos border decreases only linearly with the number of qubits n, although the spacing between multiqubit states drops exponentially with n. The investigation of time evolution in the quantum computer shows that in the quantum chaos regime, an ideal (noninteracting) state quickly disappears, and exponentially many states become mixed after a short chaotic time scale for which the dependence on system parameters is determined. Below the quantum chaos border an ideal state can survive for long times, and an be used for computation. The results show that a broad parameter region does exist where the efficient operation of a quantum computer is possible. PMID:11101971

Georgeot; Shepelyansky

2000-11-01

392

Quantum Monte Carlo Endstation for Petascale Computing  

SciTech Connect

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.

Lubos Mitas

2011-01-26

393

Computing, Information and Communications Technology (CICT) Website  

NASA Technical Reports Server (NTRS)

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).

Hardman, John; Tu, Eugene (Technical Monitor)

2002-01-01

394

Technologic advances in computed tomography.  

PubMed

Technologic improvements in CT continue. As always, emphasis in the past year has been on reducing scan times. Units employing slip-ring technology are now available. This technology makes possible spiral scanning, which promises to further reduce the effects of image-degrading patient motion, as well as opening new possibilities for quantitative and dynamic CT studies. These applications are discussed here and an update on the advances on cine-CT and the Dynamic Spatial Reconstructor unit is provided. Three-dimensional reconstructions obtained at very short scan times promise to be of particular benefit for scanning the bronchial tree. Finally, patient doses of radiation in CT are discussed. PMID:2049277

Villafana, T

1991-04-01

395

Solid state multi-ensemble quantum computer in cavity quantum electrodynamics model  

NASA Astrophysics Data System (ADS)

The first realization of solid state quantum computer was demonstrated recently by using artificial atoms — transmons in superconducting resonator. Here, we propose a novel quantum computer based on quantum electrodynamic cavity coupling many quantum nodes of controlled atomic ensembles. The quantum computer contains quantum memory and processing nodes. For the first time, we find the optimal practically attainable parameters of the atoms and optical scheme of the computer for realization of the multimode quantum memory for the photonic qubits with efficiency close to 100%. Then we reveal self modes for reversible transfer of the qubits between the quantum memory node and the processing nodes. Also, we find a realization of iSWAP gate via direct coupling of two processing nodes with an operation rate accelerated proportionally to the number of atoms in the nodes. Collective dynamic and static blockade mechanisms are proposed for realization of sqrt {iSWAP} quantum gate in multi atomic ensembles. A large number of the two-qubit gates can be simultaneously realized that opens a possibility for parallel quantum processing in the proposed quantum computer.

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

2011-08-01

396

Progress in Linear-Optics Quantum Computing.  

National Technical Information Service (NTIS)

Quantum logic operations can he performed using linear optical elements ancilla photons, and corrections based on the results of measurements made on the ancilla. We have recently demonstrated several basic quantum logic operations using single photons, a...

J. D. Franson M. M. Donegan M. J. Fitch B. C. Jacobs T. B. Pittman

2003-01-01

397

A modular functor which is universal for quantum computation  

Microsoft Academic Search

We show that the topological modular functor from Witten-Chern-Simons theory is universal for quantum computation in the sense a quantum circuit computation can be efficiently approximated by an intertwining action of a braid on the functor's state space. A computational model based on Chern-Simons theory at a fifth root of unity is defined and shown to be polynomially equivalent to

Michael Freedman; Michael Larsen; Zhenghan Wang; Michael H. Freedman

2000-01-01

398

LDRD Final Report on Quantum Computing using Interacting Semiconductor Quantum Wires.  

National Technical Information Service (NTIS)

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 implica...

E. Bielejec M. P. Lilly J. A. Seamons D. R. Tibbetts R. G. Dunn S. K. Lyo J. L. Reno

2006-01-01

399

Impact of rapidly changing computer technology on computer crime  

Microsoft Academic Search

This paper reviews the changes in computer technology that have already occurred over the past 25 years, indicates the direction of future developments and describes the potential impact of these developments on the extent and types of computer-related crime.

Marvin Sendrow

1982-01-01

400

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

ERIC Educational Resources Information Center

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…

Dalton, Bridget

401

(CICT) Computing, Information, and Communications Technology Overview  

NASA Technical Reports Server (NTRS)

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.

VanDalsem, William R.

2003-01-01

402

Quantum-dot cellular automata: computing with coupled quantum dots  

Microsoft Academic Search

We discuss novel nanoelectronic architecture paradigms based on cells composed of coupled quantum-dots. Boolean logic functions may be implemented in speci® c arrays of cells representing binary information, the so-called quantum-dot cellular automata (QCA). Cells may also be viewed as carrying analogue information and we outline a network-theoretic description of such quantum-dot nonlinear net- works (Q-CNN). In addition, we discuss

WOLFGANG POROD; CRAIG S. LENT; GARY H. BERNSTEIN; ALEXEI O. ORLOV; ISLAMSHAH AMLANI; GREGORY L. SNIDER; JAMES L. MERZ

1999-01-01

403

A Mathematica Package for Simulation of Quantum Computation  

NASA Astrophysics Data System (ADS)

In this paper we briefly describe a Mathematica package for simulation of quantum circuits and illustrate some of its features by simple examples. Unlike other Mathematica-based quantum simulators, our program provides a user-friendly graphical interface for generating quantum circuits and computing the circuit unitary matrices. It can be used for designing and testing different quantum algorithms. As an example we consider a quantum circuit implementing Grover’s search algorithm and show that it gives a quadratic speed-up in solving the search problem.

Gerdt, Vladimir P.; Kragler, Robert; Prokopenya, Alexander N.

404

Universal quantum computation with quantum-dot cellular automata in dephasing-free subspace  

Microsoft Academic Search

We investigate the possibility to have electron-pairs in dephasing-free subspace (DFS), by means of the quantum-dot cellular automata (QCA) and single-spin rotations, to carry out a high-fidelity and deterministic universal quantum computation. We show that our QCA device with electrons tunneling two dimensionally is very suitable for DFS encoding, and argue that our design favors a scalable quantum computation robust

Z. Y. Xu; M. Feng; W. M. Zhang

2008-01-01

405

Performing measurement based quantum computation on ground states  

NASA Astrophysics Data System (ADS)

One of the most exciting developments in quantum computing in recent years has been the realisation that there exist states of quantum many-body systems that can serve as a universal resource for quantum computing, where computation proceeds solely through single-qubit measurements. Although currently only a few isolated examples of such universal resource states are known, we discuss the possibility that there exist models of interacting spin systems in which an ordered phase is characterized by the ability to perform measurement-based quantum computation (MBQC). To identify such phases, we propose to use nonlocal correlation functions that quantify the fidelity of quantum gates performed between well separated qubits. The quantum computing phase is then characterized by set of order parameters corresponding to a universal set of quantum gates. We investigate a simple spin-lattice system based on the cluster-state model for MBQC by using a series of dualities with better studied models. We demonstrate that the model possesses a zero temperature phase transition between a disordered phase and an ordered ``cluster phase'' in which it is possible to perform a large class of one and two qubit quantum gates.

Doherty, Andrew; Bartlett, Stephen

2009-03-01

406

A Modular Functor Which is Universalfor Quantum Computation  

NASA Astrophysics Data System (ADS)

We show that the topological modular functor from Witten-Chern-Simons theory is universal for quantum computation in the sense that a quantum circuit computation can be efficiently approximated by an intertwining action of a braid on the functor's state space. A computational model based on Chern-Simons theory at a fifth root of unity is defined and shown to be polynomially equivalent to the quantum circuit model. The chief technical advance: the density of the irreducible sectors of the Jones representation has topological implications which will be considered elsewhere.

Freedman, Michael H.; Larsen, Michael; Wang, Zhenghan

407

Computer technology forecast study for general aviation  

NASA Technical Reports Server (NTRS)

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.

Seacord, C. L.; Vaughn, D.

1976-01-01

408

Protecting adiabatic quantum computation by dynamical decoupling  

NASA Astrophysics Data System (ADS)

Adiabatic quantum computation (AQC) relies heavily on a systems ability to remain in its ground state with high probability throughout the entirety of the adiabatic evolution. System-environment interactions present during the evolution manifest decoherence, thereby increases the probability of excitation. In this work, it is shown that the existence of such noise-producing terms can be dramatically reduced by Dynamical Decoupling (DD). In particular, we consider a multi-qubit system subjected to a classical bath modeled by random Gaussian-correlated noise. The performance of deterministic schemes such as Concatenated Dynamical Decoupling (CDD) and Nested Uhrig Dynamical Decoupling (NUDD) are analyzed for Grover's search algorithm and the two-qubit Satisfiability (2-SAT) problem. The CDD evolution substantially increases noise suppression with increasing concatenation level. In contrast, improvements in performance are only observed for specific sequence orders in the NUDD scheme. These results are verified for both adiabatic evolutions in terms of the total adiabatic run time and minimum pulse interval.

Quiroz, Gregory; Lidar, Daniel

2012-02-01

409

Implementing Computer Technologies: Teachers' Perceptions and Practices  

ERIC Educational Resources Information Center

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…

Wozney, Lori; Venkatesh, Vivek; Abrami, Philip

2006-01-01

410

Consciousness and Logic in a Quantum-Computing Universe  

NASA Astrophysics Data System (ADS)

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.

Zizzi, Paola

411

Scalable Neutral Atom Quantum Computer with Interaction on Demand  

NASA Astrophysics Data System (ADS)

We propose a scalable neutral atom quantum computer with an on- demand interaction. Artificial lattice of near field optical traps is employed to trap atom qubits. Interactions between atoms can be turned off if the atoms are separated by a high enough potential barrier so that the size of the atomic wave function is much less than the interatomic distance. One-qubit gate operation is implemented by a gate control laser beam which is attached to an individual atom. Two-qubit gate operation between a particular pair of atoms is introduced by leaving these atoms in an optical lattice and making them collide so that a particular two-qubit state acquires a dynamical phase. Our proposal is feasible within existing technology developed in cold atom gas, MEMS, nanolithography, and various areas in optics.

Nakahara, Mikio; Lapasar, Elham Hosseini; Kasamatsu, Kenichi; Ohmi, Tetsuo; Kondo, Yasushi

2011-03-01

412

Meridian: A Middle School Computer Technologies Journal  

NSDL National Science Digital Library

This new ejournal, edited and reviewed by graduate students at North Carolina State University, has a simple focus: to help demonstrate to middle school teachers the best ways of applying computer technologies to classroom teaching and learning. The inaugural issue contains articles about play designed learning, using technology to learn about technology, and gender and digital media. The second issue is slated for June 1998, and submissions are welcomed.

1998-01-01

413

BCD computing structures in quantum- dot cellular automata  

Microsoft Academic Search

This paper proposes a detailed design analysis of BCD computing circuit for quantum-dot cellular automata (QCA). QCA is attracting a lot of attentions due to its very small sizes and low power consumption. The primary device, a quantum-dot cell, can be used to make gates, wires, and memories as such it is the basic building block of nanotechnology circuits. Because

Maryam Taghizadeh; Mehdi Askari; Khossro Fardad

2008-01-01

414

Quantum computation of Fourier transforms over symmetric groups  

Microsoft Academic Search

Many algorithmic developments in quantum com- plexity theory, including Shor's celebrated algorithms for factoring and discrete logs, have made use of Fourier transforms over abelian groups. That is, at some point in the computation, the macline is in a superposition of states corresponding to elements of a finite abelian group G, and in quantum polynomial time (i.e., poly- nomial in

Robert Beals

1997-01-01

415

A theoretical model of multi-agent quantum computing  

NASA Astrophysics Data System (ADS)

The best design for practical quantum computing is one that emulates the multi-agent quantum logic function of natural biological systems. Such systems are theorized to be based upon a quantum gate formed by a nucleic acid Szilard engine (NASE) that converts Shannon entropy of encountered molecules into useful work of nucleic acid geometric reconfiguration. This theoretical mechanism is logically and thermodynamically reversible in this special case because it is literally constructed out of the (nucleic acid) information necessary for its function, thereby allowing the nucleic acid Szilard engine to function reversibly because, since the information by which it functions exists on both sides of the theoretical mechanism simultaneously, there would be no build-up of information within the theoretical mechanism, and therefore no irreversible thermodynamic energy cost would be necessary to erase information inside the mechanism. This symmetry breaking Szilard engine function is associated with emission and/or absorption of entangled photons that can provide quantum synchronization of other nucleic acid segments within and between cells. In this manner nucleic acids can be considered as a natural model of topological quantum computing in which the nonabelian interaction of genes can be represented within quantum knot/braid theory as anyon crosses determined by entropic loss or gain that leads to changes in nucleic acid covalent bond angles. This naturally occurring biological form of topological quantum computing can serve as a model for workable man-made multi-agent quantum computing systems.

Mihelic, F. Matthew

2011-05-01

416

Towards bulk based preconditioning for quantum dot computations  

Microsoft Academic Search

This article describes how to accelerate the con- vergence of Preconditioned Conjugate Gradient (PCG) type eigensolvers for the computation of several states around the band gap of colloidal quantum dots. Our new approach uses the Hamiltonian from the bulk materials constituent for the quantum dot to design an efficient preconditioner for the folded spectrum PCG method. The technique described shows

Jack Dongarra; Julien Langou; Stanimire Tomov; Christof V; Lin-Wang Wang

417

Quantum computing of quantum chaos in the kicked rotator model.  

PubMed

We investigate a quantum algorithm that simulates efficiently the quantum kicked rotator model, a system that displays rich physical properties and enables to study problems of quantum chaos, atomic physics, and localization of electrons in solids. The effects of errors in gate operations are tested on this algorithm in numerical simulations with up to 20 qubits. In this way various physical quantities are investigated. Some of them, such as second moment of probability distribution and tunneling transitions through invariant curves, are shown to be particularly sensitive to errors. However, investigations of the fidelity and the Wigner and Husimi distributions show that these physical quantities are robust in presence of imperfections. This implies that the algorithm can simulate the dynamics of quantum chaos in presence of a moderate amount of noise. PMID:12786473

Lévi, B; Georgeot, B; Shepelyansky, D L

2003-04-01

418

The brain is both neurocomputer and quantum computer.  

PubMed

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 compatible, and question whether neurocomputation alone can physiologically account for coherent gamma synchrony EEG, a candidate for the neural correlate of consciousness. Orch OR is based on quantum computation in microtubules within dendrites in cortex and other regions linked by dendritic-dendritic gap junctions ("dendritic webs") acting as laterally connected input layers of the brain's neurocomputational architecture. Within dendritic webs, consciousness is proposed to occur as gamma EEG-synchronized sequences of discrete quantum computational events acting in integration phases of neurocomputational "integrate-and-fire" cycles. Orch OR is a viable approach toward understanding how the brain produces consciousness. PMID:21635328

Hameroff, Stuart R

2007-11-12

419

Experimental demonstration of a programmable quantum computer by NMR.  

PubMed

A programmable quantum computer is experimentally demonstrated by nuclear magnetic resonance using one qubit for the program and two qubits for data. A non-separable two-qubit operation is performed in a programmable way to show the successful demonstration. Projective measurements required in the programmable quantum computer are simulated by averaging the results of experiments just like when producing an effective pure state. PMID:14675817

Kim, Jaehyun; Lee, Jae-Seung; Hwang, Taesoon; Lee, Soonchil

2004-01-01

420

Magnetic Resonance as AN Experimental Device for Quantum Computing Research  

NASA Astrophysics Data System (ADS)

The nuclear magnetic resonance (NMR) is one of the best candidates for an experiment of quantum computing. The spin state can be used as a qubit in the logic operation, because it is easily handled by the NMR technique. A low cost and low field NMR apparatus is planned to construct in order to serve as an easily manipulating experimental apparatus for the fundamental study of quantum computing. Here, as the first stage of the development the Earth's field NMR apparatus is discussed.

Chiba, Meiro; Kondo, Yasushi

2013-09-01

421

Selected Topics in Computational Quantum Field Theory.  

National Technical Information Service (NTIS)

The main mathematical structures of the quantum field theory on the lattice; fractal lattices; the problem of the continual limit and the method of finite element for a solution of the operator equations of the quantum theory are considered. 25 refs. (Ato...

1985-01-01

422

Simulating Bell violations without quantum computers  

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

423

Cloud Computing Technologies and Applications  

NASA Astrophysics Data System (ADS)

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.

Zhu, Jinzy

424

Preparing Ground States of Quantum Many-Body Systems on a Quantum Computer  

SciTech Connect

Preparing the ground state of a system of interacting classical particles is an NP-hard problem. Thus, there is in general no better algorithm to solve this problem than exhaustively going through all N configurations of the system to determine the one with lowest energy, requiring a running time proportional to N. A quantum computer, if it could be built, could solve this problem in time {radical}(N). Here, we present a powerful extension of this result to the case of interacting quantum particles, demonstrating that a quantum computer can prepare the ground state of a quantum system as efficiently as it does for classical systems.

Poulin, David [Departement de Physique, Universite de Sherbrooke, Sherbrooke, Quebec (Canada); Wocjan, Pawel [School of Electrical Engineering and Computer Science, University of Central Florida, Orlando, Florida (United States)

2009-04-03

425

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

PubMed

Preparing the ground state of a system of interacting classical particles is an NP-hard problem. Thus, there is in general no better algorithm to solve this problem than exhaustively going through all N configurations of the system to determine the one with lowest energy, requiring a running time proportional to N. A quantum computer, if it could be built, could solve this problem in time sqrt[N]. Here, we present a powerful extension of this result to the case of interacting quantum particles, demonstrating that a quantum computer can prepare the ground state of a quantum system as efficiently as it does for classical systems. PMID:19392338

Poulin, David; Wocjan, Pawel

2009-04-01

426

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

NASA Astrophysics Data System (ADS)

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.

Howard, Mark; Vala, Jiri

2012-02-01

427

Magnetic Resonance Realization of Decoherence-Free Quantum Computation  

NASA Astrophysics Data System (ADS)

We report the realization, using nuclear magnetic resonance techniques, of the first quantum computer that reliably executes a complete algorithm in the presence of strong decoherence. The computer is based on a quantum error avoidance code that protects against a class of multiple-qubit errors. The code stores two decoherence-free logical qubits in four noisy physical qubits. The computer successfully executes Grover's search algorithm in the presence of arbitrarily strong engineered decoherence. A control computer with no decoherence protection consistently fails under the same conditions.

Ollerenshaw, Jason E.; Lidar, Daniel A.; Kay, Lewis E.

2003-11-01

428

Noise resistance of adiabatic quantum computation using random matrix theory  

SciTech Connect

Besides the traditional circuit-based model of quantum computation, several quantum algorithms based on a continuous-time Hamiltonian evolution have recently been introduced, including for instance continuous-time quantum walk algorithms as well as adiabatic quantum algorithms. Unfortunately, very little is known today about the behavior of these Hamiltonian algorithms in the presence of noise. Here, we perform a fully analytical study of the resistance to noise of these algorithms using perturbation theory combined with a theoretical noise model based on random matrices drawn from the Gaussian orthogonal ensemble, whose elements vary in time and form a stationary random process.

Roland, Jeremie; Cerf, Nicolas J. [Quantum Information and Communication, Ecole Polytechnique, CP 165/59, Universite Libre de Bruxelles, 1050 Brussels (Belgium)

2005-03-01

429

Thermalization in nature and on a quantum computer.  

PubMed

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. PMID:22463502

Riera, Arnau; Gogolin, Christian; Eisert, Jens

2012-02-24

430

Thermalization in Nature and on a Quantum Computer  

NASA Astrophysics Data System (ADS)

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.

Riera, Arnau; Gogolin, Christian; Eisert, Jens

2012-02-01

431

Universal linear Bogoliubov transformations through one-way quantum computation  

SciTech Connect

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.

Ukai, Ryuji; Yoshikawa, Jun-ichi; Iwata, Noriaki; Furusawa, Akira [Department of Applied Physics and Quantum-Phase Electronics Center, School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Loock, Peter van [Optical Quantum Information Theory Group, Max Planck Institute for the Science of Light, Institute of Theoretical Physics I, Universitaet Erlangen-Nuernberg, Staudtstrasse 7/B2, D-91058 Erlangen (Germany)

2010-03-15

432

Continuous-Variable Quantum Computation of Oracle Decision Problems  

NASA Astrophysics Data System (ADS)

Quantum information processing is appealing due its ability to solve certain problems quantitatively faster than classical information processing. Most quantum algorithms have been studied in discretely parameterized systems, but many quantum systems are continuously parameterized. The field of quantum optics in particular has sophisticated techniques for manipulating continuously parameterized quantum states of light, but the lack of a code-state formalism has hindered the study of quantum algorithms in these systems. To address this situation, a code-state formalism for the solution of oracle decision problems in continuously-parameterized quantum systems is developed. Quantum information processing is appealing due its ability to solve certain problems quantitatively faster than classical information processing. Most quantum algorithms have been studied in discretely parameterized systems, but many quantum systems are continuously parameterized. The field of quantum optics in particular has sophisticated techniques for manipulating continuously parameterized quantum states of light, but the lack of a code-state formalism has hindered the study of quantum algorithms in these systems. To address this situation, a code-state formalism for the solution of oracle decision problems in continuously-parameterized quantum systems is developed. In the infinite-dimensional case, we study continuous-variable quantum algorithms for the solution of the Deutsch--Jozsa oracle decision problem implemented within a single harmonic-oscillator. Orthogonal states are used as the computational bases, and we show that, contrary to a previous claim in the literature, this implementation of quantum information processing has limitations due to a position-momentum trade-off of the Fourier transform. We further demonstrate that orthogonal encoding bases are not unique, and using the coherent states of the harmonic oscillator as the computational bases, our formalism enables quantifying the relative performances of different choices of the encoding bases. We extend our formalism to include quantum algorithms in the continuously parameterized yet finite-dimensional Hilbert space of a coherent spin system. We show that the highest-squeezed spin state possible can be approximated by a superposition of two states thus transcending the usual model of using a single basis state as algorithm input. As a particular example, we show that the close Hadamard oracle-decision problem, which is related to the Hadamard codewords of digital communications theory, can be solved quantitatively more efficiently using this computational model than by any known classical algorithm.

Adcock, Mark R. A.

433

New Approaches to Quantum Computing using Nuclear Magnetic Resonance Spectroscopy  

SciTech Connect

The power of a quantum computer (QC) relies on the fundamental concept of the superposition in quantum mechanics and thus allowing an inherent large-scale parallelization of computation. In a QC, binary information embodied in a quantum system, such as spin degrees of freedom of a spin-1/2 particle forms the qubits (quantum mechanical bits), over which appropriate logical gates perform the computation. In classical computers, the basic unit of information is the bit, which can take a value of either 0 or 1. Bits are connected together by logic gates to form logic circuits to implement complex logical operations. The expansion of modern computers has been driven by the developments of faster, smaller and cheaper logic gates. As the size of the logic gates become smaller toward the level of atomic dimensions, the performance of such a system is no longer considered classical but is rather governed by quantum mechanics. Quantum computers offer the potentially superior prospect of solving computational problems that are intractable to classical computers such as efficient database searches and cryptography. A variety of algorithms have been developed recently, most notably Shor's algorithm for factorizing long numbers into prime factors in polynomial time and Grover's quantum search algorithm. The algorithms that were of only theoretical interest as recently, until several methods were proposed to build an experimental QC. These methods include, trapped ions, cavity-QED, coupled quantum dots, Josephson junctions, spin resonance transistors, linear optics and nuclear magnetic resonance. Nuclear magnetic resonance (NMR) is uniquely capable of constructing small QCs and several algorithms have been implemented successfully. NMR-QC differs from other implementations in one important way that it is not a single QC, but a statistical ensemble of them. Thus, quantum computing based on NMR is considered as ensemble quantum computing. In NMR quantum computing, the spins with non-zero nuclear moments (spin 1/2 nuclei such as {sup 1}H or {sup 13}C) in an organic molecule dissolved in a solvent constitute the required qubits. The logic gates and algorithms correspond to set of instructions containing radio frequency (r.f) pulses and delays that manipulate the qubits and the final spectrum reflects the outcome of the algorithm. Three years ago, when we initiated proposal on NMR-QC, the foremost of the aim is to develop quantum computing as part of LLNL research programs and hence cultivate an interdisciplinary working group in the area of quantum computing. Our success in the proposal is in part responsible for the formation of the laboratory-wide exploratory group on ''quantum computing and information''. The PI's play an integral role in promoting the work performed using the LDRD funded project and hence acquire the attention within the lab as well outside. In specific goals of the project were to (a) develop experimental and sample based methods to improve the performance of NMR-QC, (b) define and estimate actual time cost or efficiency of a QCs, and (c) construct a comprehensive simulator of QC based on the principles of ensemble quantum computing. We were able to accomplish these goals and in particular we have reached some significant milestones in defining the QC efficiency and development of the QC-simulator. These developments have resulted to three publications.

Colvin, M; Krishnan, V V

2003-02-07

434

Quantum computation through entangling single photons in multipath interferometers  

PubMed

Single-photon interferometry has been used to simulate quantum computations. Its use has been limited to studying few-bit applications due to rapid growth in physical size with numbers of bits. We propose a hybrid approach that employs n photons, each having L degrees of freedom yielding L(n) basis states. The photons are entangled via a quantum nondemolition measurement. This approach introduces the essential element of quantum computing, that is, entanglement into the interferometry. Using these techniques, we demonstrate a controlled-NOT gate and a Grover's search circuit. These ideas are also applicable to the study of nonlocal correlations in many dimensions. PMID:10991193

Howell; Yeazell

2000-07-01

435

Reducing constraints on quantum computer design by encoded selective recoupling.  

PubMed

The requirement of performing both single-qubit and two-qubit operations in the implementation of universal quantum logic often leads to very demanding constraints on quantum computer design. We show here how to eliminate the need for single-qubit operations in a large subset of quantum computer proposals: those governed by isotropic and XXZ, XY-type anisotropic exchange interactions. Our method employs an encoding of one logical qubit into two physical qubits, while logic operations are performed using an analogue of the NMR selective recoupling method. PMID:11800990

Lidar, D A; Wu, L-A

2002-01-01

436

The optical quantum computer: how big and how fast?  

NASA Astrophysics Data System (ADS)

In this paper we provide a review of the perpetual optical topological quantum computer, a large scale quantum architecture utilising a single quantum component. We will examine the building block of this architecture, the photonic module, the original architecture design and a modified design which allows for the entire computer to be constructed solely from a single component. Given the extraordinary specificity of this design we can provide a pessimistic resource analysis, utilising deliberately bad circuit designs and arrangements to determine the size and speed of a large scale factoring engine.

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

2011-09-01

437

Are materials good enough for a superconducting quantum computer?  

NASA Astrophysics Data System (ADS)

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.

Martinis, John

2013-03-01

438

Quantum Monte Carlo Endstation for Petascale Computing  

SciTech Connect

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 o

David Ceperley

2011-03-02

439

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

PubMed

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 Shor's 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. PMID:24088785

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

2013-01-01

440

An improved architecture of a realizable quantum computer for quantum programming languages  

NASA Astrophysics Data System (ADS)

We study a new realizable architecture for a universal quantum computer based on different optimized components and computational models. Simulation demonstrates it has a higher computing efficiency compared with others. Error correction, fault tolerance and robustness are also discussed for this architecture.

Wu, Nan; Song, Fangmin; Li, Xiangdong

2009-05-01

441

Adiabatic pipelining: a key to ternary computing with quantum dots  

NASA Astrophysics Data System (ADS)

The quantum-dot cellular automaton (QCA), a processing platform based on interacting quantum dots, was introduced by Lent in the mid-1990s. What followed was an exhilarating period with the development of the line, the functionally complete set of logic functions, as well as more complex processing structures, however all in the realm of binary logic. Regardless of these achievements, it has to be acknowledged that the use of binary logic is in computing systems mainly the end result of the technological limitations, which the designers had to cope with in the early days of their design. The first advancement of QCAs to multi-valued (ternary) processing was performed by Lebar Bajec et al, with the argument that processing platforms of the future should not disregard the clear advantages of multi-valued logic. Some of the elementary ternary QCAs, necessary for the construction of more complex processing entities, however, lead to a remarkable increase in size when compared to their binary counterparts. This somewhat negates the advantages gained by entering the ternary computing domain. As it turned out, even the binary QCA had its initial hiccups, which have been solved by the introduction of adiabatic switching and the application of adiabatic pipeline approaches. We present here a study that introduces adiabatic switching into the ternary QCA and employs the adiabatic pipeline approach to successfully solve the issues of elementary ternary QCAs. What is more, the ternary QCAs presented here are sizewise comparable to binary QCAs. This in our view might serve towards their faster adoption.

Pe?ar, P.; Ramšak, A.; Zimic, N.; Mraz, M.; Lebar Bajec, I.

2008-12-01

442

Quantum computer aided design simulation and optimization of semiconductor quantum dots  

NASA Astrophysics Data System (ADS)

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.

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

443

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

NASA Astrophysics Data System (ADS)

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.

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

2013-09-01

444

A pseudo-spin surface-acoustic-wave quantum computer.  

PubMed

A modification to the surface-acoustic-wave quantum computer is described. The use of pseudo-spin qubits is introduced as a way to simplify the fabrication and programming of the computer. A form of optical readout that relies on the electrons in each surface-acoustic-wave minimum recombining with holes in a two-dimensional hole gas is suggested as a means to measure the output. The suggested modification would allow the quantum computer to be made smaller and to operate faster. PMID:12869323

Barnes, C H W

2003-07-15

445

Research on application of computer technology in teaching college mathematics  

Microsoft Academic Search

This paper discusses the applications of computer technology to the college mathematics' education. The computer technology education takes the computer as the main tool, merging audiovisual media (voice and image) and computer media (file, image and animation) as one teaching system, to carry out the educational activities. Computer technology represents the great advantage in teaching. The paper also analyzes the

Dong Chen; Jing Yang; Lingli Xia

2010-01-01

446

Buckyball quantum computer: realization of a quantum gate  

Microsoft Academic Search

We have studied a system composed by two endohedral fullerene\\u000amolecules. We have found that this system can be used as good candidate for the realization of quantum gates. Each of these molecules encapsules an atom carrying a\\u000aspin, therefore they interact through the spin dipole interaction.\\u000aWe show that a phase gate can be realized if we apply static

Maria Silvia Garelli; Feodor V Kusmartsev

2005-01-01

447

Locality, Weak or Strong Anticipation and Quantum Computing. I. Non-locality in Quantum Theory  

Microsoft Academic Search

The universal Turing machine is an anticipatory theory of computabil- ity by any digital or quantum machine. However the Church-Turing hypothesis only gives weak anticipation. The construction of the quantum computer (unlike classical computing) requires theory with strong anticipation. Category theory pro- vides the necessary coordinate-free mathematical language which is both construc- tive and non-local to subsume the various interpretations

M. A. Heather; B. N. Rossiter

448

National Challenge in Computer Science and Technology.  

National Technical Information Service (NTIS)

The report is aimed at people in government, industry, and academia who are concerned about the future of computing technology as a critical area of national strength, particularly at a time when America's position in other areas is in apparent decline. T...

1988-01-01

449

Assistive Computer Technology: Opening New Doorways.  

ERIC Educational Resources Information Center

Provides student services administrators and staff with information concerning the basic computer access needs of students with disabilities. Explores issues like training and support for students, faculty, and staff; funding; purchase and maintenance of equipment; technology integration; professional competence; legal considerations; and the…

Brown, Carl

1993-01-01

450

Women Workers as Users of Computer Technology.  

ERIC Educational Resources Information Center

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…

Larwood, Laurie

1992-01-01

451

Business/Computer Technologies. State Competency Profile.  

ERIC Educational Resources Information Center

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…

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

452

Instructional Technology in Computer Science Education  

ERIC Educational Resources Information Center

The Web, the Internet, the intranet and associated resources, campus computer labs, smart classrooms, course management systems, and a plethora of software packages all offer opportunities for every classroom instructor to enrich in-class and out-of-class activities. Why should an instructor consider the integration of technology into their…

Jenny, Frederick J.

2004-01-01