High Fidelity Single Qubit Operations using Pulsed EPR

Systematic errors in spin rotation operations using simple RF pulses place severe limitations on the usefulness of the pulsed magnetic resonance methods in quantum computing applications. In particular, the fidelity of quantum logic operations performed on electron spin qubits falls well below the threshold for the application of quantum algorithms. Using three independent techniques, we demonstrate the use of composite pulses to improve this fidelity by several orders of magnitude. The observed high-fidelity operations are limited by pulse phase errors, but nevertheless fall within the limits required for the application of quantum error correction.Comment: 4 pages, 3 figures To appear in Phys. Rev. Let

Measuring errors in single qubit rotations by pulsed electron paramagnetic resonance

The ability to measure and reduce systematic errors in single-qubit logic gates is crucial when evaluating quantum computing implementations. We describe pulsed electron paramagnetic resonance (EPR) sequences that can be used to measure precisely even small systematic errors in rotations of electron-spin-based qubits. Using these sequences we obtain values for errors in rotation angle and axis for single-qubit rotations using a commercial EPR spectrometer. We conclude that errors in qubit operations by pulsed EPR are not limiting factors in the implementation of electron-spin based quantum computers

Isolation of stable non cyclic 1,2-disulfoxides: revisiting the thermolysis of S-aryl sulfinimines

The thermolysis of S-aryl sulfinimines is shown to generate 1,2-disulfoxides and disulfides via initial Cope elimination, dimerisation of the produced sulfenic acid to a thiosulfinate, and subsequent disproportionation of the thiosulfinate

The polaroid image as photo-object

This article is part of a larger project on the cultural history of Polaroid photography and draws on research done at the Polaroid Corporate archive at Harvard and at the Polaroid company itself. It identifies two cultural practices engendered by Polaroid photography, which, at the point of its extinction, has briefly flared into visibility again. It argues that these practices are mistaken as novel but are in fact rediscoveries of practices that stretch back as many as five decades. The first section identifies Polaroid image-making as a photographic equivalent of what Tom Gunning calls the ‘cinema of attractions’. That is, the emphasis in its use is on the display of photographic technologies rather than the resultant image. Equally, the common practice, in both fine art and vernacular circles, of making composite pictures with Polaroid prints, draws attention from image content and redirects it to the photo as object

Corporate social responsibility: The disclosure-performance gap

As increased stakeholder pressure requires companies to be transparent about their CSR practices, it is essential to know how reliable corporate disclosure mechanisms are, testing the gap between corporate social responsibility claims and actual practice. This study benchmarks corporate social responsibility policies and practices of ten international hotel groups of particular importance to the European leisure market. We found that corporate systems are not necessarily reflective of actual operations, environmental performance is eco-savings driven, labour policies aim to comply with local legislation, socio-economic policies are inward looking with little acceptance of impacts on the destination, and customer engagement is limited. Generally larger hotel groups have more comprehensive policies but also greater gaps in implementation, while the smaller hotel groups focus only on environmental management and deliver what they promised. As the first survey of its kind in tourism, both the methodology and the findings have implications for further research. © 2012 Elsevier Ltd

Bang-bang control of fullerene qubits using ultra-fast phase gates

Quantum mechanics permits an entity, such as an atom, to exist in a superposition of multiple states simultaneously. Quantum information processing (QIP) harnesses this profound phenomenon to manipulate information in radically new ways. A fundamental challenge in all QIP technologies is the corruption of superposition in a quantum bit (qubit) through interaction with its environment. Quantum bang-bang control provides a solution by repeatedly applying `kicks' to a qubit, thus disrupting an environmental interaction. However, the speed and precision required for the kick operations has presented an obstacle to experimental realization. Here we demonstrate a phase gate of unprecedented speed on a nuclear spin qubit in a fullerene molecule (N@C60), and use it to bang-bang decouple the qubit from a strong environmental interaction. We can thus trap the qubit in closed cycles on the Bloch sphere, or lock it in a given state for an arbitrary period. Our procedure uses operations on a second qubit, an electron spin, in order to generate an arbitrary phase on the nuclear qubit. We anticipate the approach will be vital for QIP technologies, especially at the molecular scale where other strategies, such as electrode switching, are unfeasible

The uneven geographies of the Olympic carceral : from exceptionalism to normalisation

In recent years a vast academic literature has developed around the concept of ‘militarising’ or ‘securitising’ cities and in particular the policy responses to the occurrence of crime, fear of crime and the evaluation of cities as strategic sites for a spectrum of large-scale increasingly destructive perturbations in everyday urban life, such as riots, protest and acts of terrorism. Increasingly policy interventions in response to such threats have embodied characteristics of the ‘carceral archipelago’ where incarceration techniques and strategies are punitively deployed within public places of the city and embedded within the design of urban space. Such attempts at creating increasingly hyper-carceral spaces have often been supported by an array of legislation and regulation targeting the control of particular activities deemed unacceptable or inappropriate. This paper draws conceptually from the urban security literature noted above and emerging studies within the nascent sub-discipline of carceral geography, and examines their convergence on the issue of Olympic security planning. This highlights the various spatial strategies and imprints that emerge from new conceptualisations and practices of securitisation, and how these might be seen to characterise an increasingly punitive state. Here Agamben's studies of exceptionality are deployed to highlight how ‘lockdown’ security often becomes the ‘normal’ option for Olympic cities, seen as being on the frontline in the war on terror, and how a range of uneven geographies emerge and are sustained in such locations before, during and after the event. Empirically the paper uses data from ethnographic research focusing on the experiences of security preparation for, and post-event legacy of, the London 2012 Olympics. The paper also seeks to highlight how lessons from the military-carceral security strategies deployed in London have been transferred to subsequent host cities of Sochi (2014) and Rio de Janeiro (2016)

Think socially but act publicly: Refocusing CSR as corporate public responsibility

© 2016 John Wiley & Sons, Ltd. Current literature has identified many different definitions for the concept of corporate social responsibility (CSR). As a result, many organizations fail to implement and measure CSR strategically. This study reviews the different theories and concepts within CSR and suggests that the current scope of CSR activities is too large that organizations are unable to find a tangible link between CSR and their bottom line. Using two case examples, this study proposes refocusing the concept of CSR as corporate public responsibility (CPR) based on which organizations utilize the concept of publics to prioritize the groups to which they must fulfill their responsibilities before attending to society as a whole. Because organizations are constrained by limited resources, the concept of CPR allows them to invest their resources more strategically. The concept also addresses the limitations of existing theories. The practical implications of this concept will be discussed in detail

On Estimating Conditional Conservatism

The concept of conditional conservatism (asymmetric earnings timeliness) has provided new insight into financial reporting and stimulated considerable research since Basu (1997). Patatoukas and Thomas (2011) report bias in firm-level cross-sectional asymmetry estimates that they attribute to scale effects. We do not agree with their advice that researchers should avoid conditional conservatism estimates and inferences from research based on such estimates. Our theoretical and empirical analyses suggest the explanation is a correlated omitted variables problem that can be addressed in a straightforward fashion, including fixed-effects regression. Correlation between the expected components of earnings and returns biases estimates of how earnings incorporate the information contained in returns. Further, the correlation varies with returns, biasing asymmetric timeliness estimates. When firm-specific effects are taken into account, estimates do not exhibit the bias, are statistically and economically significant, are consistent with priors, and behave as a predictable function of book-to-market, size, and leverage