Classical Optimizers for Noisy Intermediate-Scale Quantum Devices

We present a collection of optimizers tuned for usage on Noisy Intermediate-Scale Quantum (NISQ) devices. Optimizers have a range of applications in quantum computing, including the Variational Quantum Eigensolver (VQE) and Quantum Approximate Optimization (QAOA) algorithms. They are also used for calibration tasks, hyperparameter tuning, in machine learning, etc. We analyze the efficiency and effectiveness of different optimizers in a VQE case study. VQE is a hybrid algorithm, with a classical minimizer step driving the next evaluation on the quantum processor. While most results to date concentrated on tuning the quantum VQE circuit, we show that, in the presence of quantum noise, the classical minimizer step needs to be carefully chosen to obtain correct results. We explore state-of-the-art gradient-free optimizers capable of handling noisy, black-box, cost functions and stress-test them using a quantum circuit simulation environment with noise injection capabilities on individual gates. Our results indicate that specifically tuned optimizers are crucial to obtaining valid science results on NISQ hardware, and will likely remain necessary even for future fault tolerant circuits

Hidden scars in depression? Implicit and explicit self-associations following recurrent depressive episodes

To help explain the recurrent nature of major depressive disorder, we tested the hypothesis that depressive episodes and/or the duration of depressive symptoms may give rise to persistent dysfunctional implicit and/or more explicit self-associations, which in turn may place people at risk for the recurrence of symptoms. We therefore examined, in the context of the Netherlands Study of Depression and Anxiety, whether the strength of self-depressed associations at baseline was related to the number of past episodes (retrospective analysis; n = 666), and whether the duration of symptoms between baseline and follow-up predicted self-depressed associations at 2-year follow-up (prospective analysis; n = 726). The lifetime Composite International Diagnostic Interviews and Life Chart Interview were used to index the number of depressive episodes; the Implicit Association Test and its explicit equivalent were used to index self-associations. Consistent with the hypothesis that self-depressed associations strengthen following prolonged activation of negative self-associations during depressive episodes, individuals' implicit and explicit self-depressed associations correlated positively both with the number of prior depressive episodes at baseline and with the duration of depressive symptoms between baseline and 2-year follow-up. There was evidence that these relationships held, particularly in the prospective study, even when controlling for neuroticism and current depressive symptoms, whereas the retrospective relationship between number of episodes and implicit self-associations fell just short of significance

A Morphological-type dependence in the mu_0-log(h) plane of Spiral galaxy disks

We present observational evidence for a galaxy `Type' dependence to the location of a spiral galaxy's disk parameters in the mu_0-log(h) (central disk surface-brightness - disk scale-length) plane. With a sample of ~40 Low Surface Brightness galaxies (both bulge- and disk-dominated) and ~80 High Surface Brightness galaxies, the early-type disk galaxies (<=Sc) tend to define a bright envelope in the mu_0-log(h) plane, while the late-type (>=Scd) spiral galaxies have, in general, smaller and fainter disks. Below the defining surface brightness threshold for a Low Surface Brightness galaxy (i.e. more than 1 mag fainter than the 21.65 B-mag arcsec^(-2) Freeman value), the early-type spiral galaxies have scale-lengths greater than 8-9 kpc, while the late-type spiral galaxies have smaller scale-lengths. All galaxies have been modelled with a seeing-convolved Sersic r^(1/n) bulge and exponential disk model. We show that the trend of decreasing bulge shape parameter (n) with increasing Hubble type and decreasing bulge-to-disk luminosity ratio, which has been observed amongst the High Surface Brightness galaxies, extends to the Low Surface Brightness galaxies, revealing a continuous range of structural parameters.Comment: To be published in ApJ. Inc. three two-part figure

A split-cavity design for the incorporation of a DC bias in a 3D microwave cavity

We report on a technique for applying a DC bias in a 3D microwave cavity. We achieve this by isolating the two halves of the cavity with a dielectric and directly using them as DC electrodes. As a proof of concept, we embed a variable capacitance diode in the cavity and tune the resonant frequency with a DC voltage, demonstrating the incorporation of a DC bias into the 3D cavity with no measurable change in its quality factor at room temperature. We also characterize the architecture at millikelvin temperatures and show that the split cavity design maintains a quality factor $Q_\text{i} \sim 8.8 \times 10^5$, making it promising for future quantum applications

Attentional avoidance of high-fat food in unsuccessful dieters

Using the exogenous cueing task, this study examined whether restrained and disinhibited eaters differ in their orientation of attention towards and their difficulty to disengage from high versus low-fat food pictures in a relatively short (500 ms) and a long presentation format (1500 ms). Overall, participants in the 500 ms condition showed a tendency to direct attention away from high-fat food pictures compared to neutral pictures. No differential pattern was evident for the 1500 ms condition. Correlational analysis revealed that reduced engagement with high-fat food was particularly pronounced for disinhibited eaters. Although in the short term this seems an adaptive strategy, it may eventually become counterproductive, as it could hinder habituation and learning to cope with seductive characteristics of high-fat food. (C) 2010 Elsevier Ltd. All rights reserved

Evolution in the Dust Lane Fraction of Edge-on L* Spiral Galaxies since z=0.8

The presence of a well-defined and narrow dust lane in an edge-on spiral galaxy is the observational signature of a thin and dense molecular disk, in which gravitational collapse has overcome turbulence. Using a sample of galaxies out to z~1 extracted from the COSMOS survey, we identify the fraction of massive disks that display a dust lane. Our goal is to explore the evolution in the stability of the molecular ISM disks in spiral galaxies over a cosmic timescale. We check the reliability of our morphological classifications against changes in restframe wavelength, resolution, and cosmic dimming with (artificially redshifted) images of local galaxies from SDSS. We find that the fraction of L* disks with dust lanes in COSMOS is consistent with the local fraction (~80%) out to z~0.7. At z=0.8, the dust lane fraction is only slightly lower. A somewhat lower dust lane fraction in starbursting galaxies tentatively supports the notion that a high specific star formation rate can efficiently destroy or inhibit a dense molecular disk. A small subsample of higher redshift COSMOS galaxies display low internal reddening (E[B-V]), as well as a low incidence of dust lanes. These may be disks in which the growth of the dusty ISM disk lags behind that of the stellar disk. We note that at z=0.8, the most massive galaxies display a lower dust lane fraction than lower mass galaxies. A small contribution of recent mergers or starbursts to this most massive population may be responsible. The fact that the fraction of galaxies with dust lanes in COSMOS is consistent with little or no evolution implies that models to explain the Spectral Energy Distribution or the host galaxy dust extinction of supernovae based on local galaxies are still applicable to higher redshift spirals. It also suggests that dust lanes are long lived phenomena or can be reformed over very short time-scales.Comment: 14 pages, 9 figures, 2 tables, accepted for publication by Ap

The discovery of two extremely low luminosity Milky Way globular clusters

We report the discovery of two extremely low luminosity globular clusters in the Milky Way Halo. These objects were detected in the Sloan Digital Sky Survey Data Release 5 and confirmed with deeper imaging at the Calar Alto Observatory. The clusters, Koposov 1 and Koposov 2, are located at $\sim 40-50$ kpc and appear to have old stellar populations and luminosities of only $M_V \sim -1$ mag. Their observed sizes of $\sim 3$ pc are well within the expected tidal limit of $\sim$10 pc at that distance. Together with Palomar 1, AM 4 and Whiting 1, these new clusters are the lowest luminosity globulars orbiting the Milky Way, with Koposov 2 the most extreme. Koposov 1 appears to lie close to distant branch of the Sagittarius stream. The half-mass relaxation times of Koposov 1 and 2 are only $\sim 70$ and $\sim 55$ Myr respectively (2 orders of magnitude shorter than the age of the stellar populations), so it would seem that they have undergone drastic mass segregation. Since they do not appear to be very concentrated, their evaporation timescales may be as low as $\sim 0.1 t_{\rm Hubble}$. These discoveries show that the structural parameter space of globular clusters in the Milky Way halo is not yet fully explored. They also add, through their short remaining survival times, significant direct evidence for a once much larger population of globular clusters.Comment: accepted for publication in ApJ, minor revision

Reflection of light from a disordered medium backed by a phase-conjugating mirror

This is a theoretical study of the interplay of optical phase-conjugation and multiple scattering. We calculate the intensity of light reflected by a phase-conjugating mirror when it is placed behind a disordered medium. We compare the results of a fully phase-coherent theory with those from the theory of radiative transfer. Both methods are equivalent if the dwell time \tau_{dwell} of a photon in the disordered medium is much larger than the inverse of the frequency shift 2\Delta\omega acquired at the phase-conjugating mirror. When \tau_{dwell} \Delta\omega < 1, in contrast, phase coherence drastically affects the reflected intensity. In particular, a minimum in the dependence of the reflectance on the disorder strength disappears when \Delta\omega is reduced below 1/\tau_{dwell}. The analogies and differences with Andreev reflection of electrons at the interface between a normal metal and a superconductor are discussed.Comment: 27 pages RevTeX with 11 figures included with psfi

Cone beam computed tomography for detecting residual stones in percutaneous nephrolithotomy, a randomized controlled trial (CAPTURE) protocol

Abstract Introduction Percutaneous nephrolithotomy (PCNL) is the standard surgical treatment method for large kidney stones. Its aim is to achieve a stone-free status, since any residual fragments (RFs) after PCNL are likely to cause additional morbidity or stone growth. Enhancing intraoperative detectability of RFs could lead to increased stone-free rates and decreased re-intervention rates. Cone beam computed tomography (CBCT) has recently been introduced in urology as a feasible method for intraoperatively imaging RFs. The aim of this trial is to determine the added value of CBCT in percutaneous nephrolithotomy, by measuring differences in stone-related morbidity for patients with procedures in which a CBCT is used versus patients with procedures without the use of CBCT. Methods The CAPTURE trial is an investigator-initiated single-center, randomized controlled trial (RCT) in adult patients who have an indication for percutaneous nephrolithotomy. A contemporary percutaneous nephrolithotomy is performed. Once the surgeon is convinced of a stone-free status by means of fluoroscopy and nephroscopy, randomization allocates patients to either the study group in whom an intraoperative CBCT scan is performed or to the control group in whom no intraoperative CBCT scan is performed. The main endpoint is the stone-free status as assessed four weeks postoperatively by low-dose non-contrast abdominal CT, as a standard follow-up procedure. Secondary endpoints include the number of PCNL procedures required and the number of stone-related events (SREs) registered. The total study population will consist of 320 patients that undergo PCNL and are eligible for randomization for an intraoperative CBCT scan. Discussion We deem a randomized controlled trial to be the most effective and reliable method to assess the efficacy of CBCT in PCNL. Though some bias may occur due to the impossibility of blinding the urologist at randomization, we estimate that the pragmatic nature of the study, standardized circumstances, and follow-up methods with pre-defined outcome measures will result in a high level of evidence. Trial registration Netherlands Trial Register (NTR) NL8168 , ABR NL70728.042.19. Registered on 15 October 2019. Prospectively registered