55,838 research outputs found
The improvement of micro-electronic component production operations by the application of cranfield developed precision engineering techniques
From an examination of the Cranfield Universal Measuring Machine certain
features were selected. These features were linked together with some of the
manufacturing and assembly operations used to make dual-in-line integrated
circuits. The result was a group of design specifications for automatic
machines to effect substantial improvements in productivity in those manufacturing
operations.
The report describes the preliminary work which culminated in the
preparation of specifications, discussions with manufacturers and changes
which were made as a result of these discussions. The report concludes with
a number of proposals for continuing the main work and suggests certain
additional, separate, investigations which, it is thought, would produce
information of value to the semi-conductor industry
Random Quantum Circuits and Pseudo-Random Operators: Theory and Applications
Pseudo-random operators consist of sets of operators that exhibit many of the
important statistical features of uniformly distributed random operators. Such
pseudo-random sets of operators are most useful whey they may be parameterized
and generated on a quantum processor in a way that requires exponentially fewer
resources than direct implementation of the uniformly random set. Efficient
pseudo-random operators can overcome the exponential cost of random operators
required for quantum communication tasks such as super-dense coding of quantum
states and approximately secure quantum data-hiding, and enable efficient
stochastic methods for noise estimation on prototype quantum processors. This
paper summarizes some recently published work demonstrating a random circuit
method for the implementation of pseudo-random unitary operators on a quantum
processor [Emerson et al., Science 302:2098 (Dec.~19, 2003)], and further
elaborates the theory and applications of pseudo-random states and operators.Comment: This paper is a synopsis of Emerson et al., Science 302: 2098 (Dec
19, 2003) and some related unpublished work; it is based on a talk given at
QCMC04; 4 pages, 1 figure, aipproc.st
Comparing the Overhead of Topological and Concatenated Quantum Error Correction
This work compares the overhead of quantum error correction with concatenated
and topological quantum error-correcting codes. To perform a numerical
analysis, we use the Quantum Resource Estimator Toolbox (QuRE) that we recently
developed. We use QuRE to estimate the number of qubits, quantum gates, and
amount of time needed to factor a 1024-bit number on several candidate quantum
technologies that differ in their clock speed and reliability. We make several
interesting observations. First, topological quantum error correction requires
fewer resources when physical gate error rates are high, white concatenated
codes have smaller overhead for physical gate error rates below approximately
10E-7. Consequently, we show that different error-correcting codes should be
chosen for two of the studied physical quantum technologies - ion traps and
superconducting qubits. Second, we observe that the composition of the
elementary gate types occurring in a typical logical circuit, a fault-tolerant
circuit protected by the surface code, and a fault-tolerant circuit protected
by a concatenated code all differ. This also suggests that choosing the most
appropriate error correction technique depends on the ability of the future
technology to perform specific gates efficiently
Entropy flow in near-critical quantum circuits
Near-critical quantum circuits are ideal physical systems for asymptotically
large-scale quantum computers, because their low energy collective excitations
evolve reversibly, effectively isolated from the environment. The design of
reversible computers is constrained by the laws governing entropy flow within
the computer. In near-critical quantum circuits, entropy flows as a locally
conserved quantum current, obeying circuit laws analogous to the electric
circuit laws. The quantum entropy current is just the energy current divided by
the temperature. A quantum circuit made from a near-critical system (of
conventional type) is described by a relativistic 1+1 dimensional relativistic
quantum field theory on the circuit. The universal properties of the
energy-momentum tensor constrain the entropy flow characteristics of the
circuit components: the entropic conductivity of the quantum wires and the
entropic admittance of the quantum circuit junctions. For example,
near-critical quantum wires are always resistanceless inductors for entropy. A
universal formula is derived for the entropic conductivity:
\sigma_S(\omega)=iv^{2}S/\omega T, where \omega is the frequency, T the
temperature, S the equilibrium entropy density and v the velocity of `light'.
The thermal conductivity is Real(T\sigma_S(\omega))=\pi v^{2}S\delta(\omega).
The thermal Drude weight is, universally, v^{2}S. This gives a way to measure
the entropy density directly.Comment: 2005 paper published 2017 in Kadanoff memorial issue of J Stat Phys
with revisions for clarity following referee's suggestions, arguments and
results unchanged, cross-posting now to quant-ph, 27 page
Toward an architecture for quantum programming
It is becoming increasingly clear that, if a useful device for quantum
computation will ever be built, it will be embodied by a classical computing
machine with control over a truly quantum subsystem, this apparatus performing
a mixture of classical and quantum computation.
This paper investigates a possible approach to the problem of programming
such machines: a template high level quantum language is presented which
complements a generic general purpose classical language with a set of quantum
primitives. The underlying scheme involves a run-time environment which
calculates the byte-code for the quantum operations and pipes it to a quantum
device controller or to a simulator.
This language can compactly express existing quantum algorithms and reduce
them to sequences of elementary operations; it also easily lends itself to
automatic, hardware independent, circuit simplification. A publicly available
preliminary implementation of the proposed ideas has been realized using the
C++ language.Comment: 23 pages, 5 figures, A4paper. Final version accepted by EJPD ("swap"
replaced by "invert" for Qops). Preliminary implementation available at:
http://sra.itc.it/people/serafini/quantum-computing/qlang.htm
Unfinished Business: Are Today’s P2P Networks Liable for Copyright Infringement?
In June 2005, the U.S. Supreme Court issued the decision in Metro-Goldwyn-Mayer Studios v. Grokster Ltd., a case that asked whether peer-to-peer networks may be held liable for facilitating the illegal distribution of music over the internet. The music industry petitioned the Supreme Court to settle the disagreement between the circuit courts over the standard of liability for aiding in copyright infringement. The case was based on a clash between the protection of technological innovation and the protection of artistic works. This iBrief examines the circuit split and the Grokster opinion and discusses the questions of liability left unresolved by the Supreme Court. It argues that further clarification of the Sony rule is still needed in order to encourage the proliferation of legitimate peer-to-peer networks by protecting their services while discouraging illegitimate file-sharing activities
Design and development of a digital subsystem employing n and p-channel Mos Fet's in complementary circuits in an integrated circuit array Final report, 1 May 1967 - 30 Apr. 1968
Digital subsystem design and development employing n-channel and p-channel in MOS FET units in complimentary circuits in integrated circuit arra
The set of realizations of a max-plus linear sequence is semi-polyhedral
We show that the set of realizations of a given dimension of a max-plus
linear sequence is a finite union of polyhedral sets, which can be computed
from any realization of the sequence. This yields an (expensive) algorithm to
solve the max-plus minimal realization problem. These results are derived from
general facts on rational expressions over idempotent commutative semirings: we
show more generally that the set of values of the coefficients of a commutative
rational expression in one letter that yield a given max-plus linear sequence
is a semi-algebraic set in the max-plus sense. In particular, it is a finite
union of polyhedral sets
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