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 $\pi/2^{2L}$ where $L$ 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 $\pi/2^{d}$ rotation gate to within $\delta=O(1/2^{d})$ currently requires both a number of qubits and number of fault-tolerant gates that grows polynomially with $d$. 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 $d$ less than or equal to some $d_{\rm max}$. It is found that integers up to length $L_{\rm max} = O(4^{d_{\rm max}})$ 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 $\pi/64$ 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

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

Assessing the climate change impacts of biogenic carbon in buildings: a critical review of two main dynamic approaches

Wood is increasingly perceived as a renewable, sustainable building material. The carbon it contains, biogenic carbon, comes from biological processes; it is characterized by a rapid turnover in the global carbon cycle. Increasing the use of harvested wood products (HWP) from sustainable forest management could provide highly needed mitigation efforts and carbon removals. However, the combined climate change benefits of sequestering biogenic carbon, storing it in harvested wood products and substituting more emission-intensive materials are hard to quantify. Although different methodological choices and assumptions can lead to opposite conclusions, there is no consensus on the assessment of biogenic carbon in life cycle assessment (LCA). Since LCA is increasingly relied upon for decision and policy making, incorrect biogenic carbon assessment could lead to inefficient or counterproductive strategies, as well as missed opportunities. This article presents a critical review of biogenic carbon impact assessment methods, it compares two main approaches to include time considerations in LCA, and suggests one that seems better suited to assess the impacts of biogenic carbon in buildings

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

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

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

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.