151,672 research outputs found
Instruction Set Architectures for Quantum Processing Units
Progress in quantum computing hardware raises questions about how these
devices can be controlled, programmed, and integrated with existing
computational workflows. We briefly describe several prominent quantum
computational models, their associated quantum processing units (QPUs), and the
adoption of these devices as accelerators within high-performance computing
systems. Emphasizing the interface to the QPU, we analyze instruction set
architectures based on reduced and complex instruction sets, i.e., RISC and
CISC architectures. We clarify the role of conventional constraints on memory
addressing and instruction widths within the quantum computing context.
Finally, we examine existing quantum computing platforms, including the D-Wave
2000Q and IBM Quantum Experience, within the context of future ISA development
and HPC needs.Comment: To be published in the proceedings in the International Super
Computing Conference 2017 publicatio
Visualization of unsteady computational fluid dynamics
The current computing environment that most researchers are using for the calculation of 3D unsteady Computational Fluid Dynamic (CFD) results is a super-computer class machine. The Massively Parallel Processors (MPP's) such as the 160 node IBM SP2 at NAS and clusters of workstations acting as a single MPP (like NAS's SGI Power-Challenge array) provide the required computation bandwidth for CFD calculations of transient problems. Work is in progress on a set of software tools designed specifically to address visualizing 3D unsteady CFD results in these super-computer-like environments. The visualization is concurrently executed with the CFD solver. The parallel version of Visual3, pV3 required splitting up the unsteady visualization task to allow execution across a network of workstation(s) and compute servers. In this computing model, the network is almost always the bottleneck so much of the effort involved techniques to reduce the size of the data transferred between machines
Moore's Law
Moore’s law originally was the observation that the number of transistors on integrated circuits doubles roughly every 18 months. However, many other areas of technology progress with a similar exponential growth. For instance, can one find an analogous law in the context of super-computing? The aim of this paper is to answer this question by showing how a variant of Moore’s law emerges from an analysis of the “Top 500” lists of super computers from 1993 to 2013
Lectures on Scattering Amplitudes via AdS/CFT
We review recent progress on computing scattering amplitudes of planar N=4
super Yang-Mills at strong coupling by using the AdS/CFT duality. We do
explicit computations by using both, dimensional regularization and a cut-off
in the radial direction. Up to an additive constant independent on the
kinematics, the finite piece of the amplitude is the same in both
regularizations. The later scheme is particularly appropriate for understanding
the conformal properties of the amplitudes.Comment: Harvmac, 23 pages, 6 figure
Propagation of gaseous detonation waves in a spatially inhomogeneous reactive medium
Detonation propagation in a compressible medium wherein the energy release
has been made spatially inhomogeneous is examined via numerical simulation. The
inhomogeneity is introduced via step functions in the reaction progress
variable, with the local value of energy release correspondingly increased so
as to maintain the same average energy density in the medium, and thus a
constant Chapman Jouguet (CJ) detonation velocity. A one-step Arrhenius rate
governs the rate of energy release in the reactive zones. The resulting
dynamics of a detonation propagating in such systems with one-dimensional
layers and two-dimensional squares are simulated using a Godunov-type
finite-volume scheme. The resulting wave dynamics are analyzed by computing the
average wave velocity and one-dimensional averaged wave structure. In the case
of sufficiently inhomogeneous media wherein the spacing between reactive zones
is greater than the inherent reaction zone length, average wave speeds
significantly greater than the corresponding CJ speed of the homogenized medium
are obtained. If the shock transit time between reactive zones is less than the
reaction time scale, then the classical CJ detonation velocity is recovered.
The spatio-temporal averaged structure of the waves in these systems is
analyzed via a Favre averaging technique, with terms associated with the
thermal and mechanical fluctuations being explicitly computed. The analysis of
the averaged wave structure identifies the super-CJ detonations as weak
detonations owing to the existence of mechanical non-equilibrium at the
effective sonic point embedded within the wave structure. The correspondence of
the super-CJ behavior identified in this study with real detonation phenomena
that may be observed in experiments is discussed
Foundations of quantum programming
Progress in the techniques of quantum devices has made people widely believe that large-scale and functional quantum computers will be eventually built. By then, super-powered quantum computer will solve many problems affecting economic and social life that cannot be addressed by classical computing. However, our experiences with classical computing suggest that once quantum computers become available in the future, quantum software will play a key role in exploiting their power, and quantum software market will even be much larger than quantum hardware market. Unfortunately, today's software development techniques are not suited to quantum computers due to the essential differences between the nature of the classical world and that of the quantum world. To lay a solid foundation for tomorrow's quantum software industry, it is critically essential to pursue systematic research into quantum programming methodology and techniques. © 2010 Springer-Verlag
Separating ABPs and Some Structured Formulas in the Non-Commutative Setting
The motivating question for this work is a long standing open problem, posed
by Nisan (1991), regarding the relative powers of algebraic branching programs
(ABPs) and formulas in the non-commutative setting. Even though the general
question continues to remain open, we make some progress towards its
resolution. To that effect, we generalise the notion of ordered polynomials in
the non-commutative setting (defined by \Hrubes, Wigderson and Yehudayoff
(2011)) to define abecedarian polynomials and models that naturally compute
them.
Our main contribution is a possible new approach towards separating formulas
and ABPs in the non-commutative setting, via lower bounds against abecedarian
formulas. In particular, we show the following.
There is an explicit n-variate degree d abecedarian polynomial
such that 1. can be computed by an abecedarian ABP of size O(nd);
2. any abecedarian formula computing must have size that is
super-polynomial in n.
We also show that a super-polynomial lower bound against abecedarian formulas
for would separate the powers of formulas and ABPs in the
non-commutative setting
4-point correlators in finite-temperature AdS/CFT: jet quenching correlations
There has been recent progress on computing real-time equilibrium 3-point
functions in finite-temperature strongly-coupled N=4 super Yang-Mills (SYM). In
this paper, we show an example of how to carry out a similar analysis for a
4-point function. We look at the stopping of high-energy "jets" in such
strongly-coupled plasmas and relate the question of whether, on an
event-by-event basis, each jet deposits its net charge over a narrow (~ 1/T) or
wide (>> 1/T) spatial region. We relate this question to the calculation of a
4-point equilibrium correlator.Comment: 41 pages, 20 figures [change from v2: just a handful of minor grammar
corrections
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