Enhanced thermal stability of the toric code through coupling to a bosonic bath

We propose and study a model of a quantum memory that features self-correcting properties and a lifetime growing arbitrarily with system size at non-zero temperature. This is achieved by locally coupling a 2D L x L toric code to a 3D bath of bosons hopping on a cubic lattice. When the stabilizer operators of the toric code are coupled to the displacement operator of the bosons, we solve the model exactly via a polaron transformation and show that the energy penalty to create anyons grows linearly with L. When the stabilizer operators of the toric code are coupled to the bosonic density operator, we use perturbation theory to show that the energy penalty for anyons scales with ln(L). For a given error model, these energy penalties lead to a lifetime of the stored quantum information growing respectively exponentially and polynomially with L. Furthermore, we show how to choose an appropriate coupling scheme in order to hinder the hopping of anyons (and not only their creation) with energy barriers that are of the same order as the anyon creation gaps. We argue that a toric code coupled to a 3D Heisenberg ferromagnet realizes our model in its low-energy sector. Finally, we discuss the delicate issue of the stability of topological order in the presence of perturbations. While we do not derive a rigorous proof of topological order, we present heuristic arguments suggesting that topological order remains intact when perturbative operators acting on the toric code spins are coupled to the bosonic environment.Comment: This manuscript has some overlap with arXiv:1209.5289. However, a different model is the focus of the current work. Since this model is exactly solvable, it allows a clearer demonstration of the principle behind our quantum memory proposal. v2: minor changes and additional referenc

Effective quantum memory Hamiltonian from local two-body interactions

In [Phys. Rev. A 88, 062313 (2013)] we proposed and studied a model for a self-correcting quantum memory in which the energetic cost for introducing a defect in the memory grows without bounds as a function of system size. This positive behavior is due to attractive long-range interactions mediated by a bosonic field to which the memory is coupled. The crucial ingredients for the implementation of such a memory are the physical realization of the bosonic field as well as local five-body interactions between the stabilizer operators of the memory and the bosonic field. Here, we show that both of these ingredients appear in a low-energy effective theory of a Hamiltonian that involves only two-body interactions between neighboring spins. In particular, we consider the low-energy, long-wavelength excitations of an ordered Heisenberg ferromagnet (magnons) as a realization of the bosonic field. Furthermore, we present perturbative gadgets for generating the required five-spin operators. Our Hamiltonian involving only local two-body interactions is thus expected to exhibit self-correcting properties as long as the noise affecting it is in the regime where the effective low-energy description remains valid.Comment: 14 pages, 3 figure

Internet-delivered cognitive-behaviour therapy (ICBT) for obsessive-compulsive disorder when delivered as routine clinical care: A phase IV clinical trial

Cognitive-behaviour therapy (CBT) is an effective treatment for obsessive-compulsive disorder (OCD), but many patients experience difficulty accessing this treatment. Internet-delivered CBT (ICBT) enhances access to CBT for individuals with OCD and has been shown to be efficacious in Phase I, II, and III clinical trials. However, there are fewer studies investigating ICBT for OCD in Phase IV clinical trials, which demonstrate the effectiveness of the intervention when provided as part of routine care. The aim of the present study was to report on the effectiveness of ICBT for OCD, using data from Australia’s MindSpot Clinic, a federally funded treatment service that provides free ICBT to Australian adults with anxiety, depression, and pain conditions. A total of 225 MindSpot users (68 % female; Mage = 34.82; SD = 11.02) were included in the study. Within-group effect sizes at post-treatment on the Yale-Brown Obsessive-Compulsive Scale, indicated medium effect sizes (g = 0.6; 95 % CI: 0.5−0.7), increasing to large effects at three-month follow up (g = 0.9; 95 % CI: 0.8–1.0). Effects on secondary outcome measures including measures of depression, generalized anxiety, and psychological distress ranged from (g = 0.5–0.6) at post-treatment and (g = 0.5–0.7) at three-month follow up. Results from benchmarking analyses indicated that the results from routine care were significantly smaller than those found in a recent clinical trial using the same treatment protocol. The results indicate that ICBT delivered in real world settings is associated with meaningful improvements in OCD symptoms, however future research may wish to examine which patients respond best to this treatment approach and how to enhance outcomes

The pain course: A randomised controlled trial examining an internet-delivered pain management program when provided with different levels of clinician support

© 2015 International Association for the Study of Pain. The present study evaluated an internet-delivered pain management program, the Pain Course, when provided with different levels of clinician support. Participants (n5490) were randomised to 1 of 4 groups: (1) Regular Contact (n5143), (2) Optional Contact (n5 141), (3) No Contact (n 5 131), and (4) a treatment-As-usual Waitlist Control Group (n 5 75). The treatment program was based on the principles of cognitive behaviour therapy and comprised 5 internet-delivered lessons provided over 8 weeks. The 3 Treatment Groups reported significant improvements (between-group Cohen's d; avg. reduction) in disability (ds ≤ 0.50; avg. reduction ≤ 18%), anxiety (ds≤0.44; avg. reduction≤32%), depression (ds≤0.73; avg. reduction≤36%), and average pain (ds≤0.30; avg. reduction ≤ 12%) immediately posttreatment, which were sustained at or further improved to 3-month follow-up. High treatment completion rates and levels of satisfaction were reported, and no marked or consistent differences were observed between the Treatment Groups. The mean clinician time per participant was 67.69 minutes (SD533.50), 12.85 minutes (SD524.61), and 5.44 minutes (SD 5 12.38) for those receiving regular contact, the option of contact, and no clinical contact, respectively. These results highlight the very significant public health potential of carefully designed and administered internet-delivered pain management programs and indicate that these programs can be successfully administered with several levels of clinical support

A survey of patient informational preferences when choosing between medical and surgical therapy for ulcerative colitis:a sub‐study from the DISCUSS project

Aim: People living with ulcerative colitis (UC) have two broad treatment avenues, namely medical or surgical therapy. The choice between these can depend on patient preference as well as the receipt of relevant information. The aim of this study was to define the informational needs of patients with UC.Method: A postal survey was designed to capture respondent demographics, treatment experienced within the previous 12 months and informational preferences by rating a long list of items. It was delivered through two hospitals that provide tertiary inflammatory bowel disease services. Descriptive analyses were performed to describe demographics and experiences. Principal component analysis was carried out using a varimax rotation to investigate informational needs.Results: A total of 101 responses were returned (20.1% response rate). The median age of respondents was 45 years and the median time since diagnosis was 10 years. Control preferences skewed towards shared (42.6%) or patient-led but clinician-informed (35.6%). Decision regret was low for the population (median 12.5/100, range 0–100). Key informational needs related to medical therapy were benefits and risks of long-term therapy, burden of hospital attendance, reproductive health, need for steroid treatment and impact on personal life. For surgery, these were stoma information, effect on daily life, effect on sexual and reproductive health, risks and benefits and disruption of life due to surgery.Conclusion: This study has identified key areas for discussion when counselling patients about treatment decisions around medical therapy and surgery for UC

The effect of body mass index on smoking behaviour and nicotine metabolism : a Mendelian randomization study

Given clear evidence that smoking lowers weight, it is possible that individuals with higher body mass index (BMI) smoke in order to lose or maintain their weight. We performed Mendelian randomization (MR) analyses of the effects of BMI on smoking behaviour in UK Biobank and the Tobacco and Genetics Consortium genome-wide association study (GWAS), on cotinine levels and nicotine metabolite ratio (NMR) in published GWAS and on DNA methylation in the Avon Longitudinal Study of Parents and Children. Our results indicate that higher BMI causally influences lifetime smoking, smoking initiation, smoking heaviness and also DNA methylation at the aryl-hydrocarbon receptor repressor (AHRR) locus, but we do not see evidence for an effect on smoking cessation. While there is no strong evidence that BMI causally influences cotinine levels, suggestive evidence for a negative causal influence on NMR may explain this. There is a causal effect of BMI on smoking, but the relationship is likely to be complex due to opposing effects on behaviour and metabolism.Peer reviewe

Perceived psychosocial impacts of legalized same-sex marriage: A scoping review of sexual minority adults’ experiences

A growing body of literature provides important insights into the meaning and impact of the right to marry a same-sex partner among sexual minority people. We conducted a scoping review to 1) identify and describe the psychosocial impacts of equal marriage rights among sexual minority adults, and 2) explore sexual minority women (SMW) perceptions of equal marriage rights and whether psychosocial impacts differ by sex. Using Arksey and O’Malley’s framework we reviewed peer-reviewed English-language publications from 2000 through 2019. We searched six databases (PubMed, PsycINFO, CINAHL, Web of Science, JSTOR, and Sociological Abstracts) to identify English language, peer-reviewed journal articles reporting findings from empirical studies with an explicit focus on the experiences and perceived impact of equal marriage rights among sexual minority adults. We found 59 studies that met our inclusion criteria. Studies identified positive psychosocial impacts of same-sex marriage (e.g., increased social acceptance, reduced stigma) across individual, interpersonal (dyad, family), community (sexual minority), and broader societal levels. Studies also found that, despite equal marriage rights, sexual minority stigma persists across these levels. Only a few studies examined differences by sex, and findings were mixed. Research to date has several limitations; for example, it disproportionately represents samples from the U.S. and White populations, and rarely examines differences by sexual or gender identity or other demographic characteristics. There is a need for additional research on the impact of equal marriage rights and same-sex marriage on the health and well-being of diverse sexual minorities across the globe

Exploring the Relationship Between Schizophrenia and Cardiovascular Disease:A Genetic Correlation and Multivariable Mendelian Randomization Study

Individuals with schizophrenia have a reduced life-expectancy compared to the general population, largely due to an increased risk of cardiovascular disease (CVD). Clinical and epidemiological studies have been unable to unravel the nature of this relationship. We obtained summary-data of genome-wide-association studies of schizophrenia (N = 130 644), heart failure (N = 977 323), coronary artery disease (N = 332 477), systolic and diastolic blood pressure (N = 757 601), heart rate variability (N = 46 952), QT interval (N = 103 331), early repolarization and dilated cardiomyopathy ECG patterns (N = 63 700). We computed genetic correlations and conducted bi-directional Mendelian randomization (MR) to assess causality. With multivariable MR, we investigated whether causal effects were mediated by smoking, body mass index, physical activity, lipid levels, or type 2 diabetes. Genetic correlations between schizophrenia and CVD were close to zero (−0.02–0.04). There was evidence that liability to schizophrenia causally increases heart failure risk. This effect remained consistent with multivariable MR. There was also evidence that liability to schizophrenia increases early repolarization pattern, largely mediated by BMI and lipids. Finally, there was evidence that liability to schizophrenia increases heart rate variability, a direction of effect contrasting clinical studies. There was weak evidence that higher systolic blood pressure increases schizophrenia risk. Our finding that liability to schizophrenia increases heart failure is consistent with the notion that schizophrenia involves a systemic dysregulation of the body with detrimental effects on the heart. To decrease cardiovascular mortality among individuals with schizophrenia, priority should lie with optimal treatment in early stages of psychosis