Estimation of correlations and non-separability in quantum channels via unitarity benchmarking

The ability to transfer quantum information between systems is a fundamental component of quantum technologies and leads to correlations within the global quantum process. However, correlation structures in quantum channels are less studied than those in quantum states. Motivated by recent techniques in randomized benchmarking, we develop a range of results for efficient estimation of correlations within a bipartite quantum channel. We introduce subunitarity measures that are invariant under local changes of basis, generalize the unitarity of a channel, and allow for the analysis of quantum information exchange within channels. Using these, we show that unitarity is monogamous, and we provide an information-disturbance relation. We then define a notion of correlated unitarity that quantifies the correlations within a given channel. Crucially, we show that this measure is strictly bounded on the set of separable channels and therefore provides a witness of nonseparability. Finally, we describe how such measures for effective noise channels can be efficiently estimated within different randomized benchmarking protocols. We find that the correlated unitarity can be estimated in a SPAM-robust manner for any separable quantum channel, and we show that a benchmarking/tomography protocol with mid-circuit resets can reliably witness nonseparability for sufficiently small reset errors. The tools we develop provide information beyond that obtained via simultaneous randomized benchmarking and so could find application in the analysis of cross-talk errors in quantum devices

Ocular toxoplasmosis: phenotype differences between toxoplasma IgM positive and IgM negative patients in a large cohort

Purpose: To investigate the differences in demographics and clinical characteristics of patients diagnosed with ocular toxoplasmosis according to their IgM status. Methods: Retrospective case note analysis was carried out on patients who tested positive for serum Toxoplasma gondii-specific IgM antibodies (IgM+) as well as a comparator group who tested negative for serum IgM (IgM-), but positive for serum IgG. Patient demographics and clinical features were compared between the two groups to evaluate for any significant differences. Results: One hundred and six patients were included in the study between March 2011 and June 2018, consisting of 37 in the IgM +group and 69 in the IgM- group. Patients in the IgM +group were significantly older (51.1 vs 34.1 years, p<0.0001), more likely to present with central macular lesions (32% vs 12%, p=0.012), and more likely to develop rhegmatogenous retinal detachment (11% vs 1%, p=0.049). In contrast, patients in the IgM- group were more likely present with pain (20% vs 3%, 0.017) and exhibit more severe inflammation of the anterior chamber and vitreous (p<0.05). Overall, retinal lesions were more likely to be superotemporal (55%) and superonasal (31%). Furthermore, age was associated with larger (p=0.003) and more peripheral lesions (p=0.007). Conclusions: This study demonstrated significant differences in clinical characteristics of ocular toxoplasmosis according to serum IgM status. IgM+ patients were older, less likely to report pain, had lower levels of intraocular inflammation, but were more likely to have macular involvement. We also found age to be correlated with larger and more peripheral lesions

The effect of carbohydrate dose and timing on timed effort and time to exhaustion within a simulated cycle race in male professional cyclists

A key performance limitation affecting professional endurance cycling is carbohydrate storage and utilisation (Pöchmüller, Schwingshack, Colombani & Hoffmann, 2016, Journal of the International Society of Sports Nutrition, 13). Muscle glycogen stores alone are inefficient at maintaining optimal blood glucose levels beyond two hours of exercise; consequently, exogenous CHO is commonly used to counteract this (Jeukendrup, 2011, Journal of Sports Sciences, 21, 91-99). High concentrations of CHO can cause drops in blood glucose, excessive glycogen utilisation and gastrointestinal discomfort (GID) (Jeukendrup, 2011). Therefore, the aim of this study was to determine if frequent, smaller CHO feedings would be preferable to large, bolus CHO feedings on time trial cycling performance. With institutional ethics approval, 5 professional cyclists completed a 4h simulated cycle ride with 3 timed efforts in a randomised, cross-over, double blind design study. Each timed effort occurred in the last 10 min of each hour (TE1, TE2, TE3); participants were asked to cycle with maximum effort for this time. There was also a final effort at the end of the 4th hour to replicate a sprint finish. This was measured as time to exhaustion (TTE). Two interventions were used; a frequent feed (F) where participants drank 20g maltodextrin in 300ml flavoured water solution 3 times per hour and a bolus feed (B) where participants drank 60g maltodextrin solution once per hour. Heart rate, power output, GID, perceived exertion (RPE), blood lactate and blood glucose were recorded before and after TE1, TE2, TE3 and TTE. Wilcoxen signed rank test and Cohen’s D was performed to study differences between interventions and effect sizes.In the F intervention, average watts were significantly higher at TE2 (P<0.05 d=0.75) and TE3 (P<0.05 d=1.21) and the RPE was lower TE1 (P≥0.05 d=1.12), TE2 (P<0.05, d=1.12) and TTE (P≥0.05 d=1.12) compared to B. There was no significant difference between any other variables. The results suggest that despite power output being higher, RPE was lower in the F intervention. Gut absorption of CHO is limited to 1g/h (Jeukendrup, 2011), which may help explain these findings. This is one of the first studies to look at concentration and timing of CHO consumption in endurance cycling. Regular feeds of 20g CHO may be more beneficial on power output and RPE in endurance cycling compared to hourly 60g feeds

Sample size calculations for cluster randomised controlled trials with a fixed number of clusters

Background\ud Cluster randomised controlled trials (CRCTs) are frequently used in health service evaluation. Assuming an average cluster size, required sample sizes are readily computed for both binary and continuous outcomes, by estimating a design effect or inflation factor. However, where the number of clusters are fixed in advance, but where it is possible to increase the number of individuals within each cluster, as is frequently the case in health service evaluation, sample size formulae have been less well studied. \ud \ud Methods\ud We systematically outline sample size formulae (including required number of randomisation units, detectable difference and power) for CRCTs with a fixed number of clusters, to provide a concise summary for both binary and continuous outcomes. Extensions to the case of unequal cluster sizes are provided. \ud \ud Results\ud For trials with a fixed number of equal sized clusters (k), the trial will be feasible provided the number of clusters is greater than the product of the number of individuals required under individual randomisation ($n_i$) and the estimated intra-cluster correlation ($\rho$). So, a simple rule is that the number of clusters ($\kappa$) will be sufficient provided: \ud \ud $\kappa$ > $n_i$ x $\rho$\ud \ud Where this is not the case, investigators can determine the maximum available power to detect the pre-specified difference, or the minimum detectable difference under the pre-specified value for power. \ud \ud Conclusions\ud Designing a CRCT with a fixed number of clusters might mean that the study will not be feasible, leading to the notion of a minimum detectable difference (or a maximum achievable power), irrespective of how many individuals are included within each cluster. \ud \u

Facets of clinicians' anxiety and the delivery of cognitive behavioral therapy.

Psychological therapists commonly fail to adhere to treatment protocols in everyday clinical practice. In part, this pattern of drift is attributable to anxious therapists being less likely to undertake some elements of evidence-based therapies - particularly the exposure-based elements. This study considers what facets of anxiety (cognitive, behavioral, physiological) are related to junior clinicians' reported use of cognitive-behavioral therapy techniques. Thirty-two clinicians (mean age = 28.9 years; mean length of CBT experience = 1.5 years; 23 female, nine male) who offered CBT were assessed for their cognitive, behavioral and physiological characteristics (Intolerance of Uncertainty scale; risk taking; skin conductance response and heart rate variability). While the three different facets of anxiety were relatively poorly associated with each other, as is usual in this literature, each facet was linked differently to the reported delivery of CBT techniques (P < .05). Overall, higher anxiety levels were associated with a poorer use of exposure methods or with a greater use of other behavioral or cognitive methods. Of the three facets of anxiety, only physiological reactivity showed an association with the clinicians' temporal characteristics, with more experienced therapists being more likely to have greater skin conductance responses to positive and negative outcomes. These findings suggest that clinicians who are more anxious are less likely to deliver the full evidence-based form of CBT and to focus instead on less challenging elements of the therapy. Potential ways of overcoming this limitation are discussed

Global trends in ultraprocessed food and drink product sales and their association with adult body mass index trajectories

This study evaluated global trends in ultraprocessed food and drink (UPFD) volume sales/capita and associations with adult body mass index (BMI) trajectories. Total food/drink volume sales/capita from Euromonitor for 80 countries (2002‐2016) were matched to mean adult BMI from the NCD Risk Factor Collaboration (2002‐2014). Products were classified as UPFD/non‐UPFD according to the NOVA classification system. Mixed models for repeated measures were used to analyse associations between UPFD volume sales/capita and adult BMI trajectories, controlling for confounding factors. The increase in UPF volume sales was highest for South and Southeast Asia (67.3%) and North Africa and the Middle East (57.6%), while for UPD, the increase was highest for South and Southeast Asia (120.0%) and Africa (70.7%). In 2016, baked goods were the biggest contributor to UPF volume sales (13.1%‐44.5%), while carbonated drinks were the biggest contributor to UPD volume sales (40.2%‐86.0%). For every standard deviation increase (51 kg/capita, 2002) in UPD volume sales, mean BMI increased by 0.195 kg/m2 for men (P < .001) and 0.072 kg/m2 for women (P = .003). For every standard deviation (40 kg/capita, 2002) increase in UPF volume sales, mean BMI increased by 0.316 kg/m2 for men (P < .001), while the association was not significant for women. Increases in UPFD volume sales/capita were positively associated with population‐level BMI trajectories

Implementing the use of objective medication adherence data in routine clinical practice via the digital CFHealthHub platform: situation analysis and strategy development using the theoretical domains framework

Background Preventative inhaled treatments preserve lung function and reduce exacerbations in Cystic Fibrosis (CF). Self-reported adherence to these treatments is over-estimated. An online platform (CFHealthHub) has been developed with patients and clinicians to display real-time objective adherence data from dose-counting nebulisers, so that clinical teams can offer informed treatment support. Methods In this paper, we identify pre-implementation barriers to healthcare practitioners performing two key behaviours: accessing objective adherence data through the website CFHealthHub and discussing medication adherence with patients. We aimed to understand barriers during the pre-implementation phase, so that appropriate strategy could be developed for the scale up of implementing objective adherence data in 19 CF centres. Thirteen semi-structured interviews were conducted with healthcare practitioners working in three UK CF centres. Qualitative data were coded using the Theoretical Domains Framework (TDF), which describes 14 validated domains to implementation behaviour change. Results Analysis indicated that an implementation strategy should address all 14 domains of the TDF to successfully support implementation. Participants did not report routines or habits for using objective adherence data in clinical care. Examples of salient barriers included skills, beliefs in consequences, and social influence and professional roles. The results also affirmed a requirement to address organisational barriers. Relevant behaviour change techniques were selected to develop implementation strategy modules using the behaviour change wheel approach to intervention development. Conclusions This paper demonstrates the value of applying the TDF at pre-implementation, to understand context and to support the development of a situationally relevant implementation strategy. Contribution to the literature · Research indicates that the implementation of healthcare innovations may be more likely to succeed when context and theory are taken into consideration. · In this study, healthcare professionals identified barriers to two behaviours that were key to the implementation of a national Cystic Fibrosis (CF) healthcare innovation. By coding barriers to the Theoretical Domains Framework (TDF), a contextually relevant implementation strategy was developed, with a focus on clinician behaviour change. · The study highlights the challenges CF teams face when implementing new remote monitoring of medication adherence, and provides an important opportunity to apply the TDF in the pre-implementation phase of a healthcare innovation