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Error-efficient computing systems
This survey explores the theory and practice of techniques to make computing systems faster or more energy-efficient by allowing them to make controlled errors. In the same way that systems which only use as much energy as necessary are referred to as being energy-efficient, you can think of the class of systems addressed by this survey as being error-efficient: They only prevent as many errors as they need to. The definition of what constitutes an error varies across the parts of a system. And the errors which are acceptable depend on the application at hand. In computing systems, making errors, when behaving correctly would be too expensive, can conserve resources. The resources conserved may be time: By making some errors, systems may be faster. The resource may also be energy: A system may use less power from its batteries or from the electrical grid by only avoiding certain errors while tolerating benign errors that are associated with reduced power consumption. The resource in question may be an even more abstract quantity such as consistency of ordering of the outputs of a system. This survey is for anyone interested in an end-to-end view of one set of techniques that address the theory and practice of making computing systems more efficient by trading errors for improved efficiency
Energy efficiency of error correction on wireless systems
Since high error rates are inevitable to the wireless environment, energy-efficient error-control is an important issue for mobile computing systems. We have studied the energy efficiency of two different error correction mechanisms and have measured the efficiency of an implementation in software. We show that it is not sufficient to concentrate on the energy efficiency of error control mechanisms only, but the required extra energy consumed by the wireless interface should be incorporated as well. A model is presented that can be used to determine an energy-efficient error correction scheme of a minimal system consisting of a general purpose processor and a wireless interface. As an example we have determined these error correction parameters on two systems with a WaveLAN interfac
Efficient measurement-based quantum computing with continuous-variable systems
We present strictly efficient schemes for scalable measurement-based quantum
computing using continuous-variable systems: These schemes are based on
suitable non-Gaussian resource states, ones that can be prepared using
interactions of light with matter systems or even purely optically. Merely
Gaussian measurements such as optical homodyning as well as photon counting
measurements are required, on individual sites. These schemes overcome
limitations posed by Gaussian cluster states, which are known not to be
universal for quantum computations of unbounded length, unless one is willing
to scale the degree of squeezing with the total system size. We establish a
framework derived from tensor networks and matrix product states with infinite
physical dimension and finite auxiliary dimension general enough to provide a
framework for such schemes. Since in the discussed schemes the logical encoding
is finite-dimensional, tools of error correction are applicable. We also
identify some further limitations for any continuous-variable computing scheme
from which one can argue that no substantially easier ways of
continuous-variable measurement-based computing than the presented one can
exist.Comment: 13 pages, 3 figures, published versio
Computing in the RAIN: a reliable array of independent nodes
The RAIN project is a research collaboration between Caltech and NASA-JPL on distributed computing and data-storage systems for future spaceborne missions. The goal of the project is to identify and develop key building blocks for reliable distributed systems built with inexpensive off-the-shelf components. The RAIN platform consists of a heterogeneous cluster of computing and/or storage nodes connected via multiple interfaces to networks configured in fault-tolerant topologies. The RAIN software components run in conjunction with operating system services and standard network protocols. Through software-implemented fault tolerance, the system tolerates multiple node, link, and switch failures, with no single point of failure. The RAIN-technology has been transferred to Rainfinity, a start-up company focusing on creating clustered solutions for improving the performance and availability of Internet data centers. In this paper, we describe the following contributions: 1) fault-tolerant interconnect topologies and communication protocols providing consistent error reporting of link failures, 2) fault management techniques based on group membership, and 3) data storage schemes based on computationally efficient error-control codes. We present several proof-of-concept applications: a highly-available video server, a highly-available Web server, and a distributed checkpointing system. Also, we describe a commercial product, Rainwall, built with the RAIN technology
Efficient algorithm for multi-qudit twirling for ensemble quantum computation
We present an efficient algorithm for twirling a multi-qudit quantum state.
The algorithm can be used for approximating the twirling operation in an
ensemble of physical systems in which the systems cannot be individually
accessed. It can also be used for computing the twirled density matrix on a
classical computer. The method is based on a simple non-unitary operation
involving a random unitary. When applying this basic building block
iteratively, the mean squared error of the approximation decays exponentially.
In contrast, when averaging over random unitary matrices the error decreases
only algebraically. We present evidence that the unitaries in our algorithm can
come from a very imperfect random source or can even be chosen
deterministically from a set of cyclically alternating matrices. Based on these
ideas we present a quantum circuit realizing twirling efficiently.Comment: 11 pages including 6 figures, revtex4; v2: presentation improved,
sections VI and VII added; v3: small changes before publicatio
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