Glassy Chimeras could be blind to quantum speedup: Designing better benchmarks for quantum annealing machines

Recently, a programmable quantum annealing machine has been built that minimizes the cost function of hard optimization problems by adiabatically quenching quantum fluctuations. Tests performed by different research teams have shown that, indeed, the machine seems to exploit quantum effects. However experiments on a class of random-bond instances have not yet demonstrated an advantage over classical optimization algorithms on traditional computer hardware. Here we present evidence as to why this might be the case. These engineered quantum annealing machines effectively operate coupled to a decohering thermal bath. Therefore, we study the finite-temperature critical behavior of the standard benchmark problem used to assess the computational capabilities of these complex machines. We simulate both random-bond Ising models and spin glasses with bimodal and Gaussian disorder on the D-Wave Chimera topology. Our results show that while the worst-case complexity of finding a ground state of an Ising spin glass on the Chimera graph is not polynomial, the finite-temperature phase space is likely rather simple: Spin glasses on Chimera have only a zero-temperature transition. This means that benchmarking optimization methods using spin glasses on the Chimera graph might not be the best benchmark problems to test quantum speedup. We propose alternative benchmarks by embedding potentially harder problems on the Chimera topology. Finally, we also study the (reentrant) disorder-temperature phase diagram of the random-bond Ising model on the Chimera graph and show that a finite-temperature ferromagnetic phase is stable up to 19.85(15)% antiferromagnetic bonds. Beyond this threshold the system only displays a zero-temperature spin-glass phase. Our results therefore show that a careful design of the hardware architecture and benchmark problems is key when building quantum annealing machines.Comment: 8 pages, 5 figures, 1 tabl

Mathematical tools for identifying the fetal response to physical exercise during pregnancy

In the applied mathematics literature there exist a significant number of tools that can reveal the interaction between mother and fetus during rest and also during and after exercise. These tools are based on techniques from a number of areas such as signal processing, time series analysis, neural networks, heart rate variability as well as dynamical systems and chaos. We will briefly review here some of these methods, concentrating on a method of extracting the fetal heart rate from the mixed maternal-fetal heart rate signal, that is based on phase space reconstructio

Evidence of a glass transition in a 10-state non-mean-field Potts glass

Potts glasses are prototype models that have been used to understand the structural glass transition. However, in finite space dimensions a glass transition remains to be detected in the 10-state Potts glass. Using a one-dimensional model with long-range power-law interactions we present evidence that a glass transition below the upper critical dimension can exist for short-range systems at low enough temperatures. Gaining insights into the structural glass transition for short-range systems using spin models is thus potentially possible, yet difficult.Comment: 4 pages, 1 table, 2 figure

Retrospective analysis reveals significant association of hypoglycemia with tramadol and methadone in contrast to other opioids.

Tramadol is one of the most commonly used analgesics worldwide, classified as having a low abuse potential by U.S. Drug Enforcement Agency, and often recommended in pain management guidelines. Its pain-relieving mechanism of action is attributed to mild μ-opioid receptor agonism, serotonin and norepinephrine mediated nociception modulation, and N-methyl-D-aspartate receptor, NMDAR, antagonism. However, recent case reports and case-control studies have shown an association between tramadol use and hypoglycemia. The growing concern over increasing tramadol use and unexpected side effects warranted a further comparative and quantitative analysis of tramadol adverse reactions. In this study we analyzed over twelve million reports from United States Food and Drug Administration Adverse Event Reporting System and provided evidence of increased propensity for hypoglycemia in patients taking tramadol when compared to patients taking other opioids, serotonin-norepinephrine reuptake inhibitors, and drugs affecting NMDAR activity. Additionally, we identified that only methadone from the opioid cohort behaves similarly to tramadol and has an association with hypoglycemia

Acute maternal exercise during the third trimester of pregnancy, influence on foetal heart rate = Ejercicio físico durante el tercer trimestre de embarazo, influencia en la frecuencia cardiaca fetal

A substantial amount of research has investigated the influence of physical exercise during pregnancy on certain maternal and foetal parameters. Regarding the behaviour of the foetal heart rate (FHR) during the maternal exercise certain controversy exists; as several investigations have studied this parameter obtaining varied results. To test the hypotheses that the foetal heart rate (FHR) increases during maternal exercise, performed on a static bicycle during the third trimester. To know if the magnitude of the increase is related to gestational age or parity. This research involved a collaboration with the Gynaecology and Obstetrics Service of “Severo Ochoa” Hospital (Madrid) and Universidad Politécnica de Madrid (UPM). The approval of the Committee of Investigation as well as of the Ethical Commission of the Hospital was obtained. Twenty healthy pregnant women have been studied, in the last trimester. No women showed any medical complications in their pregnancy or contraindications for the practice of physical exercise. Informed consent was obtained. The exercise protocol consisted in the first part (rest), followed by a session of 20 minutes of moderate work (static bicycle exercise) and then rest until the FHR returned to the pre-exercise levels. Data for the evaluation of the FHR was obtained using an Electronic Foetal Monitor, Philips FM 20; and an Accurex Plus, Polar Electro OY was used for the control of the maternal heart rate. The clinical history of the pregnant women provided data about medical and personal factors. For the statistical analysis, Pearson correlation and Student’s t test for unpaired data were used. Our results show increases (11 - 36 beats/min, mean= 24 beats/min) of the FHR in all the studied cases. The gestational age shows no correlation with increments of FHR (Pearson 0.06) and there are larger increments of FHR in secundigravid (mean=152 ± 6.0 beats/min) than in primigravid (mean=147 ± 4.6 beats/min). Maternal aerobic and moderate exercise developing during last trimester increments FHR without harmful effects. These increments do not depend on the maternal age. Parity has influence on the level of increments of the FHR. Una cantidad importante de investigaciones han valorado la influencia del ejercicio físico durante el embarazo en ciertos parámetros fetales. En relación al comportamiento de la frecuencia cardiaca fetal (FCF) durante la realización del ejercicio existe cierta controversia, muchas investigaciones han estudiado este parámetro con resultados variados. El objetivo de este estudio fue comprobar la hipótesis de un aumento de la FCF durante la realización de ejercicio en bicicleta estática en el tercer trimestre de embarazo. También conocer si esos aumentos se relacionan con la edad gestacional o la paridad de la gestante. Este estudio se ha desarrollado mediante una colaboración entre el Servicio de Ginecología y Obstetricia del Hospital Severo Ochoa de Leganés y la Universidad Politécnica de Madrid. Se obtuvo la aprobación del Comité de Investigación así como de la Comisión Ética. Fueron estudiadas 20 gestantes en el último trimestre, sin complicaciones ni contraindicaciones médicas para el ejercicio, cada mujer firmó un consentimiento informado. El protocolo de ejercicio consistió en una primera parte de reposo, una sesión de 20 minutos de trabajo moderado en bicicleta estática y el reposo final con retorno a los niveles normales de FCF. Los datos correspondientes a la FCF se obtuvieron por medio de un Monitor Fetal Electrónico Philips FM 20, y un pulsómetro Accurex Plus, Polar Electro OY, fue usado para el control de la frecuencia cardiaca materna. La historia clínica de cada gestante aportó datos relativos a características médicas y personales. Para el análisis estadístico se utilizaron mecanismos descriptivos, el índice de correlación de Pearson y la t de Student para comparación de medias. Nuestros resultados muestran aumentos de la FCF de 11-36 lat/min (media de 24 lat/min). Los días de gestación no presentaron una correlación positiva con el nivel de los incrementos (Pearson 0.06). Hubo mayores aumentos en gestantes secundigrávidas (media=152 ± 6.0 lat/min) que en primigrávidas (media=147 ± 4.6 lat/min). El ejercicio aeróbico y moderado materno desarrollado durante el tercer trimestre de embarazo incrementa la FCF sin efectos perjudiciales. Los aumentos no dependen de la edad gestacional de la madre. La paridad de la gestante tiene influencia en el nivel de los incrementos

Proton-pump inhibitor use is associated with a broad spectrum of neurological adverse events including impaired hearing, vision, and memory.

Proton-pump inhibitors, PPIs, are considered effective therapy for stomach acid suppression due to their irreversible inhibition of the hydrogen/potassium pump in the gastric parietal cells. They are widely prescribed and are considered safe for over-the-counter use. Recent studies have shown an association between PPI use and Alzheimer dementia, while others have disputed that connection. We analyzed over ten million United States Food and Drug Administration Adverse Event Reporting System reports, including over forty thousand reports containing PPIs, and provided evidence of increased propensity for memory impairment among PPI reports when compared to histamine-2 receptor antagonist control group. Furthermore, we found significant associations of PPI use with a wide range of neurological adverse reactions including, migraine, several peripheral neuropathies, and visual and auditory neurosensory abnormalities

Topological color codes on Union Jack lattices: A stable implementation of the whole Clifford group

We study the error threshold of topological color codes on Union Jack lattices that allow for the full implementation of the whole Clifford group of quantum gates. After mapping the error-correction process onto a statistical mechanical random 3-body Ising model on a Union Jack lattice, we compute its phase diagram in the temperature-disorder plane using Monte Carlo simulations. Surprisingly, topological color codes on Union Jack lattices have similar error stability than color codes on triangular lattices, as well as the Kitaev toric code. The enhanced computational capabilities of the topological color codes on Union Jack lattices with respect to triangular lattices and the toric code demonstrate the inherent robustness of this implementation.Comment: 8 pages, 4 figures, 1 tabl