Readout-Induced Suppression and Enhancement of Superconducting Qubit Lifetimes.

It has long been known that the lifetimes of superconducting qubits suffer during readout, increasing readout errors. We show that this degradation is due to the anti-Zeno effect, as readout-induced dephasing broadens the qubit so that it overlaps "hot spots" of strong dissipation, likely due to two-level systems in the qubit's bath. Using a flux-tunable qubit to probe the qubit's frequency-dependent loss, we accurately predict the change in lifetime during readout with a new self-consistent master equation that incorporates the modification to qubit relaxation due to measurement-induced dephasing. Moreover, we controllably demonstrate both the Zeno and anti-Zeno effects, which can explain both suppression and the rarer enhancement of qubit lifetimes during readout.

Miniaturizing Transmon Qubits Using van der Waals Materials.

Quantum computers can potentially achieve an exponential speedup versus classical computers on certain computational tasks, recently demonstrated in superconducting qubit processors. However, the capacitor electrodes that comprise these qubits must be large in order to avoid lossy dielectrics. This tactic hinders scaling by increasing parasitic coupling among circuit components, degrading individual qubit addressability, and limiting the spatial density of qubits. Here, we take advantage of the unique properties of van der Waals (vdW) materials to reduce the qubit area by >1000 times while preserving the capacitance while maintaining quantum coherence. Our qubits combine conventional aluminum-based Josephson junctions with parallel-plate capacitors composed of crystalline layers of superconducting niobium diselenide and insulating hexagonal boron nitride. We measure a vdW transmon T1 relaxation time of 1.06 µs, demonstrating a path to achieve high-qubit-density quantum processors with long coherence times, and the broad utility of layered heterostructures in low-loss, high-coherence quantum devices.

Symmetry-aware reservoir computing.

We demonstrate that matching the symmetry properties of a reservoir computer (RC) to the data being processed dramatically increases its processing power. We apply our method to the parity task, a challenging benchmark problem that highlights inversion and permutation symmetries, and to a chaotic system inference task that presents an inversion symmetry rule. For the parity task, our symmetry-aware RC obtains zero error using an exponentially reduced neural network and training data, greatly speeding up the time to result and outperforming artificial neural networks. When both symmetries are respected, we find that the network size N necessary to obtain zero error for 50 different RC instances scales linearly with the parity-order n. Moreover, some symmetry-aware RC instances perform a zero error classification with only N=1 for n≤7. Furthermore, we show that a symmetry-aware RC only needs a training data set with size on the order of (n+n/2) to obtain such a performance, an exponential reduction in comparison to a regular RC which requires a training data set with size on the order of n2^{n} to contain all 2^{n} possible n-bit-long sequences. For the inference task, we show that a symmetry-aware RC presents a normalized root-mean-square error three orders-of-magnitude smaller than regular RCs. For both tasks, our RC approach respects the symmetries by adjusting only the input and the output layers, and not by problem-based modifications to the neural network. We anticipate that the generalizations of our procedure can be applied in information processing for problems with known symmetries.

Quantitative Tomography for Continuous Variable Quantum Systems.

We present a continuous variable tomography scheme that reconstructs the Husimi Q function (Wigner function) by Lagrange interpolation, using measurements of the Q function (Wigner function) at the Padua points, conjectured to be optimal sampling points for two dimensional reconstruction. Our approach drastically reduces the number of measurements required compared to using equidistant points on a regular grid, although reanalysis of such experiments is possible. The reconstruction algorithm produces a reconstructed function with exponentially decreasing error and quasilinear runtime in the number of Padua points. Moreover, using the interpolating polynomial of the Q function, we present a technique to directly estimate the density matrix elements of the continuous variable state, with only a linear propagation of input measurement error. Furthermore, we derive a state-independent analytical bound on this error, such that our estimate of the density matrix is accompanied by a measure of its uncertainty.

Risk of uterine rupture in Australian women attempting vaginal birth after one prior caesarean section: a retrospective population-based cohort study.

OBJECTIVE: Higher risks of uterine rupture have been reported among women attempting vaginal birth after caesarean (VBAC) particularly following induction with prostaglandins, compared with women who do not labour. This study aimed to estimate these risks as well as that associated with oxytocin use. DESIGN: Population-based retrospective cohort study involving all women who had their first births by caesarean. In their second birth, risks of uterine rupture among women without labour and women who had labour augmented or induced were compared with women who gave birth after spontaneous labour. SETTING: Four Australian states in 1998-2000. POPULATION: Women on pregnancy outcome databases with a second birth after a prior caesarean for their first birth. METHODS: From 29, 008 women identified from the databases, those with uterine rupture were identified and validated using hospital case records. MAIN OUTCOME MEASURE: Uterine rupture. RESULTS: The risk of complete uterine rupture among women without labour was 0.01%. The risk in spontaneous labour without augmentation was 0.15%, considerably higher when there was augmentation with oxytocin (1.91%). The risk with induction of labour was 0.54% for oxytocin alone, 0.68% for prostaglandin alone, 0.63% without either and 0.88% when they were combined. Compared with spontaneous labour, risks were increased three- to five-fold for any induction, six-fold for prostaglandin combined with oxytocin and 14-fold for augmentation with oxytocin. CONCLUSIONS: Careful consideration should be given to the use of oxytocin for augmentation of labour or induction by any method for women with a previous caesarean in view of increased risks of uterine rupture.

Clinical and pathological factors predictive of lymph node status in women with screen-detected breast cancer.

Two thousand one hundred and thirty five asymptomatic invasive breast cancers detected through screening mammography were analysed to identify predictors of lymph node involvement. Multivariable analysis indicated that predictors included larger tumour diameter, an infiltrating ductal or lobular histological type, multifocal disease, a palpable lesion, and a younger age at diagnosis. An association also was found between nodal involvement and the presence of an extensive in situ component (EIC). Grade was associated with nodal involvement as a univariate predictor. It would be more accurate for screening assessment clinics to use models for predicting nodal status that were customised to their own experience rather than generic models developed in other settings that related predominantly to symptomatic cancer. These models could assist clinical decision-making on axillary node dissection and give guidance to pathologists on numbers of tissue sections to examine.

Treatment and survival from colorectal cancer: the experience of patients at South Australian teaching hospitals between 1980 and 2002.

AIMS: To evaluate trends in colorectal cancer survival and treatment at South Australian teaching hospitals and degree of adherence to treatment guidelines which recommend adjuvant chemotherapy for Dukes' C colon cancers and combined chemotherapy and radiotherapy for high-risk rectal cancers. MATERIALS AND METHODS: Trends in disease specific survival and primary treatment were analysed, and comparisons drawn between diagnostic epochs, using cancer registry data from South Australian teaching hospitals. Statistical methods included univariate and multivariable disease specific survival analyses. RESULTS: Five-year survival increased from 48% in 1980-1986 to 56% in 1995-2002. Largest gains were for stage C, where survivals were higher when chemotherapy was part of the primary treatment. By comparison, gains in 1-year survival were largest for stage D. Chemotherapy was provided for 4% of patients with colorectal cancers in 1980-1986, increasing to 32% in 1995-2002. Among stage C cases below 70 years at diagnosis, the proportion having chemotherapy increased to 83% in 1995-2002. The most common chemotherapy was fluorouracil (5FU) as a single agent in 1980-1986 and 5FU with leucovorin in 1995-2002. As expected, radiotherapy was used more frequently for rectal than colon cancers, and particularly for stage C. Among stage C rectal cases below 70 years, the proportion having radiotherapy increased from 10% in 1980-1986 to 57% in 1995-2002. Approximately 93% of colorectal cancers were treated surgically. Patients not treated surgically tended to be aged 80 years or more and to present with distant metastases. CONCLUSIONS: Trends in chemotherapy and radiotherapy accord with evidence-based recommendations. There have been reassuring gains in survivals after adjusting for stage, grade and other prognostic indicators. The data show survival gains and treatment patterns that individual hospitals can use as benchmarks when evaluating their own experience.

Detection by screening mammography is a powerful independent predictor of survival in women diagnosed with breast cancer.

Four hundred and sixteen invasive breast cancers, detected initially by mammography, were compared with 929 presenting symptomatically, all treated at a South Australian teaching hospital. Predictable differences included lower stages and grades, less vascular invasion and proliferative activity, and more hormone-receptor expression among the mammographically detected. Unpredicted differences included significantly higher survivals for mammographically detected cases throughout the 9 year follow-up period after adjusting for stage and the Nottingham Prognostic Index. In a multivariable analysis, differences in stage, grade, and hormone receptor expression accounted for only about half the survival advantage of mammographically detected tumours. Accounting for additional person and tumour characteristics had only a marginal effect on this result. This suggests that detection by mammography has independent favourable prognostic significance beyond that explained by conventional indicators. If confirmed, this finding would have important implications for the prognostic advice given to women and may merit further investigation into its underlying biological mechanisms.

The coverage of cancer patients by designated palliative services: a population-based study, South Australia, 1999.

Our aims were to determine the extent of coverage by designated palliative care services of the population of terminally ill cancer patients in South Australia, and to identify the types of patients who receive these services and the types who do not. All designated hospice and palliative care services in South Australia notified to the State Cancer Registry the identifying details of all their patients who died in 1999. This information was cross-referenced with the data for all cancer deaths (n=3086) recorded on the registry for 1999. We found that the level of coverage by designated palliative services of patients who died with cancer in 1999 was 68.2%. This methodology was previously used to show that the level of coverage had increased from 55.8% for cancer deaths in 1990 to 63.1% for those in 1993. Patients who died at home had the largest coverage by palliative services (74.7%), whereas patients who died in nursing homes had the lowest coverage (48.4%). Patients who did not receive care from these palliative services tended to be 80 years of age or older at death, country residents, those with a survival time from diagnosis of three months or less, and those diagnosed with a prostate, breast, or haematological malignancy. Gender, socioeconomic status of residential area, and race were not related to coverage by a designated palliative service, whereas migrants to Australia from the UK, Ireland, and Southern Europe were relatively high users of these services. We conclude that the high level of palliative care coverage observed in this study reflects widespread support for the establishment of designated services. When planning future care, special consideration should be given to the types of patients who most miss out on these services.

An analysis of factors associated with interval as opposed to screen-detected breast cancers, including hormone therapy and mammographic density.

A comparison of 270 interval breast cancers in South Australian women aged 50 years and over with 628 age-matched screen-detected cases indicated that the former had more advanced stages (P<0.001), higher grades (P<0.001), and more frequently a history of past breast problems (P<0.027). After adjusting for these factors, and presence of a self-reported breast lump at the last screen, using conditional logistic regression, hormone replacement therapy (HRT) exposure in the 6 months prior to this screen had a raised relative odds (95% CL) of an interval cancer of 1.48 (1.02, 2.14). For 479 women where breast density was measured, high density showed an elevated relative odds of an interval cancer of 2.62 (1.71, 4.02). The relative odds of a high density was raised to 2.02 (1.33, 3.06) when the HRT history was positive. Screeners should be aware when there is a history of HRT or past breast problems, or a high breast density, that there is an increased probability of a subsequent interval cancer.

Tumour location and prognostic characteristics as determinants of survival of women with invasive breast cancer: South Australian hospital-based cancer registries, 1987-1998.

Survivals from breast cancer varied by location of lesion (P<0.001), with 10-year survivals of 61% applying for central (n=772), 73% for medial (n=350), and 72% for lateral (n=966) lesions. Univariate analyses of determinants of central locations indicated that the following were predictive: a more advanced TNM stage (P<0.001); a larger tumour diameter (P=0.002); a higher grade (P=0.032); a negative oestrogen receptor status (P=0.004); a negative progesterone receptor status (P=0.004); and histological type (P=0.011), with more of the lobular lesions being located centrally. Cox proportional hazards regression indicated that the relative risk (95% confidence limits) of case fatality for central, as opposed to other, lesions reduced from 1.46 (1.20, 1.78) to 1.16 (0.95, 1.41) when stage was added to the model, with no other factor having an additional conditioning effect. It is concluded that central lesions have worse outcomes, mostly due to their more advanced stages. Means of finding these tumours earlier should be investigated.

Subsequent birth outcomes after an unexplained stillbirth: preliminary population-based retrospective cohort study.

The objective of this study was to determine whether women who have experienced an unexplained stillbirth have a higher risk of adverse perinatal outcomes in subsequent births. We compared 316 subsequent births to women with a previous unexplained stillbirth, with 3160 births to women with no previous history of stillbirth, matched by year of birth, in the period 1987-1997, from the South Australian perinatal database, using logistic regression analysis. There was no increase in the rate of stillbirth and no statistically significant increase in the rate of perinatal death (OR 1.62 [95%CI 0.63-4.20]) or neonatal death, although larger studies are needed to confirm this. However, after adjusting for age, parity, and hospital category of birth, women who had a previous stillbirth had increased incidences in subsequent births of abnormal glucose tolerance or gestational diabetes (a fourfold increase); induction of labour and elective Caesarean section; fetal distress and postpartum haemorrhage; and forceps and emergency Caesarean delivery and preterm birth, which were independent of induction of labour. Gestational age at birth and birthweight were also significantly reduced, suggesting a need for close monitoring of their future pregnancies.

Where patients with cancer die in South Australia, 1990-1999: a population-based review.

OBJECTIVE: To determine the place of death of South Australians who die of cancer. DESIGN: A population-based, cross-sectional study of data from the South Australian Cancer Registry. PARTICIPANTS: 29,230 patients with cancer dying in 1990-1999. MAIN OUTCOME MEASURES: Place of death; patient demography; year of death; survival from diagnosis; and type of cancer. RESULTS: 25.0% of patients died in a metropolitan public hospital, 19.9% in a hospice, 16.9% in a country hospital, 15.8% at a private residence, 12.7% in a metropolitan private hospital, and 9.7% in a nursing home. Although the change in place of death was not marked, multivariate logistic regression showed a secular trend away from metropolitan public hospitals towards metropolitan private hospitals and, in 1998-1999, towards nursing homes. Patients dying of cancer in a metropolitan public hospital were more likely to be younger, males, born outside Australia, and residents of lower socioeconomic areas of Adelaide. They were also more likely to have died within three months of diagnosis, and to have a haematological malignancy or a cancer of the upper digestive tract, lung or female breast. In contrast, patients dying at a private residence tended to be under 70 years and comprise longer-term survivors. Country residents were less likely than Adelaide residents to die in a hospice. CONCLUSION: The proportion of patients dying in different settings have health service implications. The relatively low use of hospice facilities by country patients may reflect differences in access to hospice facilities.

Effects of home-based intervention on unplanned readmissions and out-of-hospital deaths.

OBJECTIVE: To determine the effect of a home-based intervention (HBI) on the frequency of unplanned readmission and out-of-hospital death among patients discharged home from acute hospital care. DESIGN: A randomized controlled trial comparing HBI with usual care (UC). SETTING: A tertiary referral hospital servicing the northwestern region of Adelaide, South Australia. PARTICIPANTS: Medical and surgical patients (n = 762) discharged home after hospitalization. INTERVENTION: Home-based intervention (n = 381) consisted of counseling of all patients before discharge followed by a single home visit (by a nurse and pharmacist) to those patients considered to be at high risk of readmission (n = 314) in order to optimize compliance with and knowledge of the treatment regimen, identify early clinical deterioration, and intensify follow-up of such patients where appropriate. MEASUREMENTS: The primary endpoint was the number of unplanned readmissions plus out-of-hospital deaths over a 6-month follow-up period. RESULTS: During the study follow-up, the major endpoint occurred most commonly in the UC group (217 vs 155 episodes: P < .001). Overall, the HBI group demonstrated fewer unplanned readmissions (154 vs 197: P = .022), out-of-hospital deaths (1 vs. 20: P < .001), total deaths (12 vs. 29: P = .006), emergency department attendances (236 vs 314: P < .001), and total days of hospitalization (1452 vs 1766: P < .001). There was a disproportionate reduction in multiple events among HBI patients (P = .035). Hospital-based costs of health care during study follow-up tended to be lower in the HBI group ($A2190 vs $A2680 per patient: P = .102). Mean cost of HBI was $A190 per patient visited, whereas other community-based health care costs were similar for both groups. CONCLUSIONS: Among high-risk patients discharged from acute hospital care, HBI is beneficial in limiting unplanned readmissions and reducing risk of out-of-hospital death. It may be particularly cost-effective if applied selectively to patients with a history of frequent unplanned hospital admission.

Rehospitalisation for asthma within 12 months: unequal rates on the basis of gender in two hospitals.

BACKGROUND: High asthma morbidity has been reported in certain demographic groups in geographical areas of low socioeconomic status (SES). AIM AND METHODS: We tested for an ecological association between the gender of people being frequently hospitalised for asthma and the SES of the area in which they lived, using a cross-sectional study. RESULTS: Women represented 75% of the readmission population at The Queen Elizabeth Hospital (TQEH--low SES hospital) and 55% at Modbury Hospital (moderate-high SES hospital). Women at TQEH were significantly more likely to have one readmission within 12 months and over 30 times more likely to have two or more readmissions than women at Modbury Hospital. CONCLUSION: The ecological association observed in this study needs to be confirmed elsewhere in Australia.

Near-fatal asthma in South Australia: descriptive features and medication use.

BACKGROUND: Self-reported prior morbidity levels and medication use among survivors of a near-fatal asthma attack (NFA) were studied. AIMS: To identify deficiencies in asthma management and opportunities for intervention. METHODS: A hundred and twenty-seven consecutive patients aged 15 years or more presenting with a NFA to accident and emergency departments of teaching hospitals were interviewed. RESULTS: High levels of morbidity due to asthma were reported. Most cases (79%) reported symptoms occurring at least weekly in the three months before their NFA. A mean of 20.8 days was reportedly lost from work, school or other usual daily activity in the 12 months before these events. Regular use of beta agonist as nebuliser solution was reported by 27% of cases, increasing to 34.5% in response to increased symptoms, while 41% reported use of nebulised beta agonist in response to the NFA event. Less than half of all cases (46%) reported using an inhaled corticosteroid on a regular basis. Oral corticosteroids were used by 33% of cases at times of increased symptoms in the preceding 12 months. However, only 7% of cases reported initiating or increasing oral corticosteroids at the time of the NFA. CONCLUSIONS: Despite high levels of prior asthma morbidity, regular preventive inhaled corticosteroid use was not widespread in this series of NFA asthmatics. By comparison, over-reliance on regular beta agonist medication was common. Oral corticosteroids were rarely commenced in response to the NFA.

Characteristics of near-fatal asthma in childhood.

As part of the South Australian asthma mortality survey, we examined 30 cases of near-fatal asthma attacks in children under 15 years of age who were seen over a 3-year period from May 1988 to June 1991. Subjects presented with asthma and either respiratory arrest, PaCO2 above 50 mm Hg, and/or an altered state of consciousness or inability to speak on presentation at a metropolitan Adelaide teaching hospital. A standardized interview and questionnaire was completed with subjects/parents and medical practitioners. Data were reviewed by the assessment panel which made collective judgments based on predetermined criteria. Seventeen patients (57%) were male, 20% were less than 7 years of age, and the majority (53%) were aged between 12 and 15 years. The majority (83%) had severe asthma and only one case (3.3%) had mild asthma. Half of the subjects were waking every night due to asthma and 79% had significant exercise limitation. A quarter of the subjects had a previous ICU admission and 70% had a hospital admission in the last 12 months. Primary care was carried out by a general practitioner in 57% of cases, and 70% of subjects had a crisis plan. Only 46% of those older than 7 years of age had ever used a peak-flow meter. Eighty percent of subjects or their families had high denial scores, and in 73% of cases psychosocial factors were considered to be significant. Eighty percent of cases experienced acute progressive respiratory distress, and 63% of cases delayed seeking medical care.(ABSTRACT TRUNCATED AT 250 WORDS)

Trends in prostate cancer incidence and mortality rates in South Australia, 1977-1993.

OBJECTIVE: To investigate trends in recorded incidence and mortality rates for prostate cancer in South Australia. DESIGN: A multiple Poisson regression analysis of recorded incidence (by diagnostic period) and mortality (by year of death), after adjusting for age at diagnosis and residential location. SUBJECTS AND SETTING: 8073 patients with prostate cancer and 2659 who died of prostate cancer as notified to the South Australian Cancer Registry for 1977-1993. MAIN OUTCOME MEASURES: The relative risk of a recorded diagnosis of prostate cancer (by period of diagnosis), and of a death from prostate cancer (by year of death). RESULTS: During 1977-1989, the recorded age-standardised incidence of prostate cancer was stable, but it increased markedly thereafter. The relative risk (95% confidence limits) of diagnosed prostate cancer was 1.36 (1.29, 1.43) in 1990-1992, and 2.26 (2.12, 2.42) in 1993, when compared with 1977-1989. There was a smaller and less certain increase in prostate cancer mortality. CONCLUSIONS: The large increase in recorded incidence of prostate cancer in South Australia is thought to be due mostly to increased disclosure of latent cases from increased clinical investigations. Until there is experimental evidence of health benefits from screening and related investigations for prostate cancer in asymptomatic men, it will be difficult to reconcile benefits with costs.

Psychiatric and medical features of near fatal asthma.

BACKGROUND: The associations between psychiatric caseness, denial, and self reported measures of handicap and morbidity due to asthma in patients suffering a near fatal attack of asthma have not been fully explored. METHODS: Seventy seven consecutive subjects who presented to Adelaide teaching hospitals with a near fatal attack of asthma were assessed with a validated semi-structured interview following discharge from hospital. RESULTS: 43% of the patients scored > or = 5 on the GHQ-28 questionnaire. There was a positive correlation between GHQ-28 score and limitation to daily activities due to asthma, and between GHQ-28 score and days lost from work, school or usual daily activities, both of which were retained after adjusting for age and sex. Asthma severity did not show a clear association with GHQ-28 score. The asthmatic patients reported high levels of denial, 57% scoring more than 3 out of 5 on the denial scale of the Illness Behaviour Questionnaire. Presentation with a history of progressive respiratory distress was negatively associated with denial score. This persisted after adjustment for age and sex--that is, those with high denial scores were more likely to report presentation as sudden collapse than progressive respiratory distress. CONCLUSIONS: Psychiatric caseness (GHQ score > or = 5) is associated with high levels of morbidity in asthmatic patients who survive a near fatal attack of asthma. High levels of denial in asthmatic subjects may be life threatening. The link between morbidity associated with asthma and psychiatric features, along with other psychosocial issues, warrants further investigation. A broader paradigm than the traditional medical model should be considered when assessing patients with asthma.

Trends in prognostic factors of melanoma in South Australia, 1981-1992: implications for health promotion.

OBJECTIVE: To analyse trends in prognostic factors at diagnosis of melanoma to indicate targets for health promotion. METHODS: Cases of melanoma notified to the South Australian Cancer Registry during 1981-1992 (1361 in situ and 4509 invasive) were analysed by tumour site, histological type, stage, thickness, period of diagnosis and sociodemographic characteristics of the patient. RESULTS: The relative probability of being diagnosed with an in-situ, rather than a thin invasive, lesion increased progressively between 1984-1986 and 1990-1992. The relative probability of having an in-situ melanoma diagnosed was: lower among those aged 80 years or more; higher among patients residing in the upper socioeconomic areas of Adelaide; high for lesions on the face; and high for lentigo maligna as opposed to superficial spreading lesions. The relative probability of invasive lesions being diagnosed when more than 1.5 mm thick decreased progressively between the 1981-1983 and 1990-1992 diagnosis periods. The relative probability of thick lesions being diagnosed was higher among older patients and for nodular lesions compared with superficial spreading or lentigo maligna lesions. Facial lesions and those in males tended to be thicker. CONCLUSIONS: There are favourable trends towards earlier detection of melanomas in South Australia, probably reflecting the effect of skin-cancer awareness campaigns. Further campaigns should emphasise early detection in people aged 60 years and over, males and residents of less affluent areas. Early detection of nodular melanomas and invasive lesions of the face also warrants special attention.