863 research outputs found
Maximum likelihood method for fitting a sum of exponentials to experimental data
Maximum likelihood method for fitting sum of expotentials to experimental dat
Scalability of Shor's algorithm with a limited set of rotation gates
Typical circuit implementations of Shor's algorithm involve controlled
rotation gates of magnitude where is the binary length of the
integer N to be factored. Such gates cannot be implemented exactly using
existing fault-tolerant techniques. Approximating a given controlled
rotation gate to within currently requires both
a number of qubits and number of fault-tolerant gates that grows polynomially
with . In this paper we show that this additional growth in space and time
complexity would severely limit the applicability of Shor's algorithm to large
integers. Consequently, we study in detail the effect of using only controlled
rotation gates with less than or equal to some . It is found
that integers up to length can be factored
without significant performance penalty implying that the cumbersome techniques
of fault-tolerant computation only need to be used to create controlled
rotation gates of magnitude if integers thousands of bits long are
desired factored. Explicit fault-tolerant constructions of such gates are also
discussed.Comment: Substantially revised version, twice as long as original. Two tables
converted into one 8-part figure, new section added on the construction of
arbitrary single-qubit rotations using only the fault-tolerant gate set.
Substantial additional discussion and explanatory figures added throughout.
(8 pages, 6 figures
Fast Quantum Modular Exponentiation
We present a detailed analysis of the impact on modular exponentiation of
architectural features and possible concurrent gate execution. Various
arithmetic algorithms are evaluated for execution time, potential concurrency,
and space tradeoffs. We find that, to exponentiate an n-bit number, for storage
space 100n (twenty times the minimum 5n), we can execute modular exponentiation
two hundred to seven hundred times faster than optimized versions of the basic
algorithms, depending on architecture, for n=128. Addition on a neighbor-only
architecture is limited to O(n) time when non-neighbor architectures can reach
O(log n), demonstrating that physical characteristics of a computing device
have an important impact on both real-world running time and asymptotic
behavior. Our results will help guide experimental implementations of quantum
algorithms and devices.Comment: to appear in PRA 71(5); RevTeX, 12 pages, 12 figures; v2 revision is
substantial, with new algorithmic variants, much shorter and clearer text,
and revised equation formattin
The impact of global economic crisis and austerity on quality of working life and work-life balance: A capabilities perspective
This paper draws on the capabilities approach as a framework for examining the impact of the global economic crisis and austerity on quality of working life and work-life balance. Our paper focuses on Greece, an extreme case of a country in economic crisis, characterised by a weak institutional basis. We build on the work of Barbara Hobson and colleagues who first applied the capabilities approach to explore work-life balance capabilities. Our study contributes to the development of theory by emphasising the sense of entitlement concept within the capabilities approach and by proposing a modified conceptual framework that encapsulates the link between capabilities, agency, and the sense of entitlement, where the latter acts as a cognitive ‘filter’ that enhances or weakens an individual’s perception of her/his agency to enact on her/his capabilities. Drawing on the accounts of twenty Greek professional and managerial workers, we illustrate how the crisis and austerity measures have eroded working conditions and thus the sense of entitlement, leading to the weakening of our participants’ agency and capabilities to achieve quality of working life and work-life balance.
This is the peer reviewed version of the article to be published in final form by Wiley at http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1740-4762. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving
Resource Requirements for Fault-Tolerant Quantum Simulation: The Transverse Ising Model Ground State
We estimate the resource requirements, the total number of physical qubits
and computational time, required to compute the ground state energy of a 1-D
quantum Transverse Ising Model (TIM) of N spin-1/2 particles, as a function of
the system size and the numerical precision. This estimate is based on
analyzing the impact of fault-tolerant quantum error correction in the context
of the Quantum Logic Array (QLA) architecture. Our results show that due to the
exponential scaling of the computational time with the desired precision of the
energy, significant amount of error correciton is required to implement the TIM
problem. Comparison of our results to the resource requirements for a
fault-tolerant implementation of Shor's quantum factoring algorithm reveals
that the required logical qubit reliability is similar for both the TIM problem
and the factoring problem.Comment: 19 pages, 8 figure
Implementing Shor's algorithm on Josephson Charge Qubits
We investigate the physical implementation of Shor's factorization algorithm
on a Josephson charge qubit register. While we pursue a universal method to
factor a composite integer of any size, the scheme is demonstrated for the
number 21. We consider both the physical and algorithmic requirements for an
optimal implementation when only a small number of qubits is available. These
aspects of quantum computation are usually the topics of separate research
communities; we present a unifying discussion of both of these fundamental
features bridging Shor's algorithm to its physical realization using Josephson
junction qubits. In order to meet the stringent requirements set by a short
decoherence time, we accelerate the algorithm by decomposing the quantum
circuit into tailored two- and three-qubit gates and we find their physical
realizations through numerical optimization.Comment: 12 pages, submitted to Phys. Rev.
Star Architecture as Socio-Material Assemblage
Taking inspiration from new materialism and assemblage, the chapter deals with star architects and iconic buildings as socio-material network effects that do not pre-exist action, but are enacted in practice, in the materiality of design crafting and city building. Star architects are here conceptualized as part of broader assemblages of actors and practices ‘making star architecture’ a reality, and the buildings they design are considered not just as unique and iconic objects, but dis-articulated as complex crafts mobilizing skills, technologies, materials, and forms of knowledge not necessarily ascribable to architecture. Overcoming narrow criticism focusing on the symbolic order of icons as unique creations and alienated repetitions of capitalist development, the chapter’s main aim is to widen the scope of critique by bridging culture and economy, symbolism and practicality, making star architecture available to a broad, fragmented arena of (potential) critics, unevenly equipped with critical tools and differentiated experiences
Full Counting Statistics of Non-Commuting Variables: the Case of Spin Counts
We discuss the Full Counting Statistics of non-commuting variables with the
measurement of successive spin counts in non-collinear directions taken as an
example. We show that owing to an irreducible detector back-action, the FCS in
this case may be sensitive to the dynamics of the detectors, and may differ
from the predictions obtained with using a naive version of the Projection
Postulate. We present here a general model of detector dynamics and
path-integral approach to the evaluation of FCS. We concentrate further on a
simple "diffusive" model of the detector dynamics where the FCS can be
evaluated with transfer-matrix method. The resulting probability distribution
of spin counts is characterized by anomalously large higher cumulants and
substantially deviates from Gaussian Statistics.Comment: 11 pages, 3 figure
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