Maximal adaptive-decision speedups in quantum-state readout

The average time $T$ required for high-fidelity readout of quantum states can be significantly reduced via a real-time adaptive decision rule. An adaptive decision rule stops the readout as soon as a desired level of confidence has been achieved, as opposed to setting a fixed readout time $t_f$. The performance of the adaptive decision is characterized by the "adaptive-decision speedup," $t_f/T$. In this work, we reformulate this readout problem in terms of the first-passage time of a particle undergoing stochastic motion. This formalism allows us to theoretically establish the maximum achievable adaptive-decision speedups for several physical two-state readout implementations. We show that for two common readout schemes (the Gaussian latching readout and a readout relying on state-dependent decay), the speedup is bounded by $4$ and $2$, respectively, in the limit of high single-shot readout fidelity. We experimentally study the achievable speedup in a real-world scenario by applying the adaptive decision rule to a readout of the nitrogen-vacancy-center (NV-center) charge state. We find a speedup of $\approx 2$ with our experimental parameters. In addition, we propose a simple readout scheme for which the speedup can, in principle, be increased without bound as the fidelity is increased. Our results should lead to immediate improvements in nanoscale magnetometry based on spin-to-charge conversion of the NV-center spin, and provide a theoretical framework for further optimization of the bandwidth of quantum measurements.Comment: 18 pages, 11 figures. This version is close to the published versio

Anomalous exponents at the onset of an instability

Critical exponents are calculated exactly at the onset of an instability, using asymptotic expansiontechniques. When the unstable mode is subject to multiplicative noise whose spectrum at zero frequency vanishes, we show that the critical behavior can be anomalous, i.e. the mode amplitude X scales with departure from onset \mu as $~ \mu^\beta$ with an exponent $\beta$ different from its deterministic value. This behavior is observed in a direct numerical simulation of the dynamo instability and our results provide a possible explanation to recent experimental observations

The Toughest Apologetic: A Study on Christians who Deconvert

Christianity is distinct from any other world religion, philosophy, or ideology in how it explains universal origin, meaning, destiny, and morality. The Christian message is also unique in promise of a personal and life-changing relationship with the Creator God. One can hardly deny the influence of the Christian faith has had on humanity over the past two thousand years. However, a growing number of those believers who once claimed commitment to the transcendent message and transformative power of Jesus Christ eventually rescind belief in their faith and renounce their deeply held spiritual convictions. This paper explores why people with roots in the Christian worldview completely shift their ideology and radically transform their perspectives to the point where they now consider their previous system of belief as evil and destructive

Examination of decision-making processes for resource allocation at the college-level and school-level within an academic unit

The purpose of this study was to examine the quantitative and qualitative factors used when deciding how to allocate resources within a single academic unit and three subunits, and who was involved in those decision-making processes. It focused on the College of Engineering and three Schools of Engineering at Purdue University from 2000 – 2007, when Dr. Martin C. Jischke was president. The university underwent institution-wide strategic planning and increased use of metrics in decision-making under his leadership. Financial data from the college and three schools were collected and analyzed. An interview protocol was developed and piloted before implementation in interviews with nine administrators from three levels at the institution: university, college, and school. These participants all had some degree of involvement in the resource allocation processes affecting either the college or one of the three schools. The research was designed as an embedded case study and incorporated qualitative and quantitative data; systems theory provided the framework and grounded theory guided the analysis. ^ The results suggest that the role of strategic plan development and enactment served to address the issue of shared governance. The administrators\u27 efforts to involve stakeholders led to changes in perceived ownership in various places within the College of Engineering. The university\u27s increased focus on interdisciplinary research, furthermore, encouraged new research collaborations across school and college boundaries. Suggestions for implementation include establishing and communicating a decision-making framework to improve stakeholders\u27 understanding of this process, conducting regular reviews of existing programs to improve efficiency, and increasing interdisciplinary collaborations

Fault-tolerant Quantum Communication with Minimal Physical Requirements

We describe a novel protocol for a quantum repeater which enables long distance quantum communication through realistic, lossy photonic channels. Contrary to previous proposals, our protocol incorporates active purification of arbitrary errors at each step of the protocol using only two qubits at each repeater station. Because of these minimal physical requirements, the present protocol can be realized in simple physical systems such as solid-state single photon emitters. As an example, we show how nitrogen vacancy color centers in diamond can be used to implement the protocol, using the nuclear and electronic spin to form the two qubits.Comment: 4 pages, 3 figures. V2: Minor modifications. V3: Major changes in the presentation and new titl

Ferromagnetic resonance force microscopy on microscopic cobalt single layer films

We report mechanical detection of ferromagnetic resonance signals from microscopic Co single layer thin films using a magnetic resonance force microscope (MRFM). Variations in the magnetic anisotropy field and the inhomogeneity of were clearly observed in the FMR spectra of microscopic Co thin films 500 and 1000 angstrom thick and 40 X 200 micron^2 in lateral extent. This demonstrates the important potential that MRFM detection of FMR holds for microscopic characterization of spatial distribution of magnetic properties in magnetic layered materials and devices.Comment: 4 pages, 2 figures, RevTex. To be published in Applied Physics Letters, October 5, 199

Characteristics of ADHD symptom response/remission in a clinical trial of methylphenidate extended release

Clinical trials in attention-deficit/hyperactivity disorder (ADHD) have typically measured outcome using clinician ratings on the Attention-Deficit/Hyperactivity Disorder Rating Scale, Fourth Edition (ADHD-RS-IV) and the Clinical Global Impression-Improvement (CGI-I) scale. Remission has been defined as an endpoint score of less than or equal to 18 on the ADHD-RS-IV (or a mean score of 1). Responders have been defined as patients who achieve a CGI-I score of much or very much improved (1 or 2). There is a lack of agreement in the literature on what percent change in symptoms on the ADHD-RS-IV should be used to define improvement or remission. This study uses data from a clinical trial of a methylphenidate extended release (MPH-MLR; Aptensio XR®) phase III clinical trial to attempt to determine the percent change of symptoms that best corresponds with improvement and remission. Symptom remission at endpoint (ADHD-RS-IV total score ≤18) was most closely aligned with a ≥46% reduction in ADHD-RS-IV total score. Clinical improvement was most closely aligned with a ≥40% reduction in ADHD-RS-IV total score. The three different measures of outcome were strongly aligned during double blind and open label treatment, and were independent of subtype status. Our data suggest that at least 40% improvement in symptoms is needed to achieve a robust response at endpoint

Hydrodynamic orienting of asymmetric microobjects under gravity

It is shown that nonsymmetric microobjects orient while settling under gravity in a viscous fluid. To analyze this process, a simple shape is chosen: a non-deformable `chain'. The chain consists of two straight arms, made of touching solid spheres. In the absence of external torques, the spheres are free to spin along the arms. The motion of the chain is evaluated by solving the Stokes equations with the use of the multipole method. It is demonstrated that the spinning beads speed up sedimentation by a small amount, and increase the orientation rate significantly in comparison to the corresponding rigid chain. It is shown that chains orient towards the V-shaped stable stationary configuration. In contrast, rods and star-shaped microobjects do not rotate. The hydrodynamic orienting is relevant for efficient swimming of non-symmetric microobjects, and for sedimenting suspensions.Comment: 9 page