Fidelity benchmarks for two-qubit gates in silicon.

Universal quantum computation will require qubit technology based on a scalable platform1, together with quantum error correction protocols that place strict limits on the maximum infidelities for one- and two-qubit gate operations2,3. Although various qubit systems have shown high fidelities at the one-qubit level4-10, the only solid-state qubits manufactured using standard lithographic techniques that have demonstrated two-qubit fidelities near the fault-tolerance threshold6 have been in superconductor systems. Silicon-based quantum dot qubits are also amenable to large-scale fabrication and can achieve high single-qubit gate fidelities (exceeding 99.9 per cent) using isotopically enriched silicon11,12. Two-qubit gates have now been demonstrated in a number of systems13-15, but as yet an accurate assessment of their fidelities using Clifford-based randomized benchmarking, which uses sequences of randomly chosen gates to measure the error, has not been achieved. Here, for qubits encoded on the electron spin states of gate-defined quantum dots, we demonstrate Bell state tomography with fidelities ranging from 80 to 89 per cent, and two-qubit randomized benchmarking with an average Clifford gate fidelity of 94.7 per cent and an average controlled-rotation fidelity of 98 per cent. These fidelities are found to be limited by the relatively long gate times used here compared with the decoherence times of the qubits. Silicon qubit designs employing fast gate operations with high Rabi frequencies16,17, together with advanced pulsing techniques18, should therefore enable much higher fidelities in the near future.

Uptake of HIV Testing Services Through Novel Community-Based Sexual and Reproductive Health Services: An Analysis of the Pilot Implementation Phase of the Yathu Yathu Intervention for Adolescents and Young People Aged 15-24 in Lusaka, Zambia.

Adolescents and young people aged 15-24 are underserved by available HIV-testing services (HTS). Delivering HTS through community-based, peer-led, hubs may prove acceptable and accessible to adolescents and young people, thus increasing HIV-testing coverage. We used data from the pilot phase of a cluster-randomised trial of community-based sexual and reproductive health services for adolescents and young people in Lusaka, Zambia, between September 2019 and January 2020, to explore factors associated with uptake of HTS through community-based hubs. 5,757 adolescents and young people attended the hubs (63% female), among whom 75% tested for HIV (76% of females, 75% of males). Community-based hubs provided HTS to 80% of adolescents and young people with no history of HIV-testing. Among females, uptake of HTS was lower among married/cohabiting females; among males, uptake was lower among unmarried males and among individuals at risk of hazardous alcohol use. The high number of adolescents and young people accessing hubs for HIV testing suggests they are acceptable. Enhanced targeting of HTS to groups who may not perceive their HIV risk needs to be implemented.

Loophole-free Bell inequality violation using electron spins separated by 1.3 kilometres.

More than 50 years ago, John Bell proved that no theory of nature that obeys locality and realism can reproduce all the predictions of quantum theory: in any local-realist theory, the correlations between outcomes of measurements on distant particles satisfy an inequality that can be violated if the particles are entangled. Numerous Bell inequality tests have been reported; however, all experiments reported so far required additional assumptions to obtain a contradiction with local realism, resulting in 'loopholes'. Here we report a Bell experiment that is free of any such additional assumption and thus directly tests the principles underlying Bell's inequality. We use an event-ready scheme that enables the generation of robust entanglement between distant electron spins (estimated state fidelity of 0.92 ± 0.03). Efficient spin read-out avoids the fair-sampling assumption (detection loophole), while the use of fast random-basis selection and spin read-out combined with a spatial separation of 1.3 kilometres ensure the required locality conditions. We performed 245 trials that tested the CHSH-Bell inequality S ≤ 2 and found S = 2.42 ± 0.20 (where S quantifies the correlation between measurement outcomes). A null-hypothesis test yields a probability of at most P = 0.039 that a local-realist model for space-like separated sites could produce data with a violation at least as large as we observe, even when allowing for memory in the devices. Our data hence imply statistically significant rejection of the local-realist null hypothesis. This conclusion may be further consolidated in future experiments; for instance, reaching a value of P = 0.001 would require approximately 700 trials for an observed S = 2.4. With improvements, our experiment could be used for testing less-conventional theories, and for implementing device-independent quantum-secure communication and randomness certification.

Heralded entanglement between solid-state qubits separated by three metres.

Quantum entanglement between spatially separated objects is one of the most intriguing phenomena in physics. The outcomes of independent measurements on entangled objects show correlations that cannot be explained by classical physics. As well as being of fundamental interest, entanglement is a unique resource for quantum information processing and communication. Entangled quantum bits (qubits) can be used to share private information or implement quantum logical gates. Such capabilities are particularly useful when the entangled qubits are spatially separated, providing the opportunity to create highly connected quantum networks or extend quantum cryptography to long distances. Here we report entanglement of two electron spin qubits in diamond with a spatial separation of three metres. We establish this entanglement using a robust protocol based on creation of spin-photon entanglement at each location and a subsequent joint measurement of the photons. Detection of the photons heralds the projection of the spin qubits onto an entangled state. We verify the resulting non-local quantum correlations by performing single-shot readout on the qubits in different bases. The long-distance entanglement reported here can be combined with recently achieved initialization, readout and entanglement operations on local long-lived nuclear spin registers, paving the way for deterministic long-distance teleportation, quantum repeaters and extended quantum networks.

Factors associated with HIV-testing and acceptance of an offer of home-based testing by men in rural Zambia.

The objective of this study is to describe HIV-testing among men in rural Lusaka Province, Zambia, using a population-based survey for a cluster-randomized trial. Households (N = 120) were randomly selected from each of the 42 clusters, defined as a health facility catchment area. Individuals aged 15-60 years were invited to complete questionnaires regarding demographics and HIV-testing history. Men testing in the last year were defined as recent-testers. After questionnaire completion adults were offered home-based rapid HIV-testing. Of the 2,828 men, 53 % reported ever-testing and 25 % recently-testing. Factors independently associated with ever- and recent-testing included age 20+ years, secondary/higher education, being married or widowed, a history of TB-treatment and higher socioeconomic position. 53 % of never-testers and 57 % of men who did not report a recent-test accepted home-based HIV-testing. Current HIV-testing approaches are inadequate in this high prevalence setting. Alternative strategies, including self-testing, mobile- or workplace-testing, may be required to complement facility-based services.

Frequency of HIV-testing and factors associated with multiple lifetime HIV-testing among a rural population of Zambian men.

BACKGROUND: Across sub-Saharan Africa, men's levels of HIV-testing remain inadequate relative to women's. Men are less likely to access anti-retroviral therapy and experience higher levels of morbidity and mortality once initiated on treatment. More frequent HIV-testing by men at continued risk of HIV-infection is required to facilitate earlier diagnosis. This study explored the frequency of HIV-testing among a rural population of men and the factors associated with more frequent HIV-testing. METHODS: We conducted a secondary analysis of a population-based survey in three rural district in Zambia, from February-November, 2013. Households (N = 300) in randomly selected squares from 42 study sites, defined as a health facility and its catchment area, were invited to participate. Individuals in eligible households were invited to complete questionnaires regarding demographics and HIV-testing behaviours. Men were defined as multiple HIV-testers if they reported more than one lifetime test. Upon questionnaire completion, individuals were offered rapid home-based HIV-testing. RESULTS: Of the 2376 men, more than half (61%) reported having ever-tested for HIV. The median number of lifetime tests was 2 (interquartile range = 1-3). Just over half (n = 834; 57%) of ever-testers were defined as multiple-testers. Relative to never-testers, multiple-testers had higher levels of education and were more likely to report an occupation. Among the 719 men linked to a spouse, multiple-testing was higher among men whose spouse reported ever-testing (adjusted prevalence ratio = 3.02 95% CI: 1.37-4.66). Multiple-testing was higher in study sites where anti-retroviral therapy was available at the health facility on the day of a health facility audit. Among ever-testers, education and occupation were positively associated with multiple-testing relative to reporting one lifetime HIV-test. Almost half (49%) of ever-testers accepted the offer of home-based HIV-testing. DISCUSSION: Reported HIV-testing increased among this population of men since a 2011/12 survey. Yet, only 35% of all men reported multiple lifetime HIV-tests. The factors associated with multiple HIV-testing were similar to factors associated with ever-testing for HIV. Men living with HIV were less likely to report multiple HIV-tests and employment and education were associated with multiple-testing. The offer of home-based HIV-testing increased the frequency of HIV-testing among men. CONCLUSION: Although men's levels of ever-testing for HIV have increased, strategies need to increase the lifetime frequency of HIV-testing among men at continued risk of HIV-infection.

From caution to urgency: the evolution of HIV testing and counselling in Africa.

OBJECTIVE: To describe recent changes in policy on provider-initiated testing and counselling (PITC) for human immunodeficiency virus (HIV) infection in African countries and to investigate patients' experiences of and views about PITC. METHODS: A review of the published literature and of national HIV testing policies, strategic frameworks, plans and other relevant documents was carried out. FINDINGS: Of the African countries reviewed, 42 (79.2%) had adopted a PITC policy. Of the 42, all recommended PITC for the prevention of mother-to-child HIV transmission, 66.7% recommended it for tuberculosis clinics and patients, and 45.2% for sexually transmitted infection clinics. Moreover, 43.6% adopted PITC in 2005 or 2006. The literature search identified 11 studies on patients' experiences of and views about PITC in clinical settings in Africa. The clear majority regarded PITC as acceptable. However, women in antenatal clinics were not always aware that they had the right to decline an HIV test. CONCLUSION: Policy and practice on HIV testing and counselling in Africa has shifted from a cautious approach that emphasizes confidentiality to greater acceptance of the routine offer of HIV testing. The introduction of PITC in clinical settings has contributed to increased HIV testing in several of these settings. Most patients regard PITC as acceptable. However, other approaches are needed to reach people who do not consult health-care services.

Yathu Yathu ("For us, by us"): Design of a cluster-randomised trial of the impact of community-based, peer-led comprehensive sexual and reproductive health services for adolescents and young people aged 15 to 24 in Lusaka, Zambia.

BACKGROUND: In sub-Saharan Africa, the growing population of adolescents and young people aged 15 to 24 face a high burden of HIV, and other preventable and treatable sexually transmitted infections. Despite this burden, adolescents and young people are the population least served by available sexual and reproductive (SRH) services. This trial aims to evaluate the impact of community-based peer-led SRH services, combined with a novel incentivised "loyalty card" system, on knowledge of HIV status and coverage of SRH services. METHODS: A cluster-randomised trial (CRT) with embedded process and economic evaluation. DISCUSSION: With little available evidence of the impact of community-based, peer-led services on coverage of SRH services, our study will provide evidence critical to expanding our knowledge of how to reach adolescents and young people. The "loyalty card" system is also a novel approach to providing SRH services. The delivery of community-based services supported by incentives in the form of loyalty cards is innovative, and may prove a simple strategy to improve access to SRH services. Adolescents and young people remain underserved by available SRH services; there remains a critical need to identify ways to provide adolescents and young people with access to SRH services. Rigorous evidence of whether this innovative strategy, with strong links to the local health facility, increases coverage of critical SRH services would add to the evidence-base of how to reach adolescents and young people.

How Can We Support the Use of Oral PrEP Among Young Women who Sell Sex? A PrEP Cascade Analysis.

BACKGROUND: We constructed self-reported pre-exposure prophylaxis (PrEP) cascades and explored factors associated with and barriers to PrEP use to inform efforts to support PrEP use among young women who sell sex. METHODS: Using self-reported data from HIV-negative young women who sell sex enrolled into a cohort study using respondent-driven sampling in Zimbabwe, we constructed PrEP cascades assessing knowledge of, ever offered, ever used, and current PrEP use in 2017 and 2019. We used logistic regression to examine factors associated with PrEP use by 2019. Through qualitative interviews with 43 women enrolled in the cohort, we investigated barriers to PrEP use. RESULTS: At enrollment, 50% of women had heard of PrEP, 12% had ever been offered PrEP, and 7% ever used PrEP. Over time, all cascade domains: 96% of women had heard of and 55% reported an active offer of PrEP. Among women retained in the study in 2019 (56%; n = 538), 34% ever took PrEP by 2019. PrEP use was associated with, at enrollment, reporting more clients in the past month (10+: 45% vs 1-3: 27% adjOR = 1.71 95% CI: 1.06 to 2.76), duration of selling sex (24% <2 years vs 38% 2-3 years; adjOR = 0.51 95% CI: 0.32 to 0.83), and having visited a female sex worker program in the past 12 months (55% vs 27%; adjOR = 2.92 95% CI: 1.91 to 4.46). Qualitative interviews revealed fear of disclosing sex work, HIV-related/ART-related stigma, and (opportunity) costs of accessing PrEP as barriers to use. CONCLUSION: PrEP use was associated with factors known to increase HIV risk. Fear of stigma, disclosure, and supply-side barriers need to be addressed to increase women's ability to use PrEP.

The role of irradiation source setups and indirect phototransformation: Kinetic aspects and the formation of transformation products of weakly sunlight-absorbing pesticides.

In this study, emission spectra of three different commonly used xenon irradiation sources were analyzed and compared for the first time to ascertain the most suitable setup to simulate natural solar radiation. In order to demonstrate setup differences, absolute photon fluxes of irradiation sources were received by actinometry. Verification was done by measuring quantum yields of the model compounds Penconazole, Terbutryn, and Mecoprop in every setup. Differences regarding kinetic aspects and the formation of transformation products (TPs) was evaluated by analyzing direct phototransformation and additionally photolysis in presence of Nitrate as a photosensitizer in one irradiation setup (optical bench). Results showed that a precise setup characterization is needed to estimate whether irradiation sources are suitable to simulate terrestrial sunlight. This was found to be especially important for weakly sunlight-absorbing substances. In comparison with direct photolysis, indirect photolysis led to an enhancement of degradation rate constants for all substances and in case of Mecoprop to different types of TPs that were formed during irradiation. This study underlined that there are big knowledge gaps regarding irradiation sources setups and conditions. It is therefore absolutely necessary to consider those factors while simulating substance degradation and the TP formation under environmental conditions.

Single-spin qubits in isotopically enriched silicon at low magnetic field.

Single-electron spin qubits employ magnetic fields on the order of 1 Tesla or above to enable quantum state readout via spin-dependent-tunnelling. This requires demanding microwave engineering for coherent spin resonance control, which limits the prospects for large scale multi-qubit systems. Alternatively, singlet-triplet readout enables high-fidelity spin-state measurements in much lower magnetic fields, without the need for reservoirs. Here, we demonstrate low-field operation of metal-oxide-silicon quantum dot qubits by combining coherent single-spin control with high-fidelity, single-shot, Pauli-spin-blockade-based ST readout. We discover that the qubits decohere faster at low magnetic fields with [Formula: see text] µs and [Formula: see text] µs at 150 mT. Their coherence is limited by spin flips of residual 29Si nuclei in the isotopically enriched 28Si host material, which occur more frequently at lower fields. Our finding indicates that new trade-offs will be required to ensure the frequency stabilization of spin qubits, and highlights the importance of isotopic enrichment of device substrates for the realization of a scalable silicon-based quantum processor.

[Diagnosis and treatment of interstitial cystitis (IC/PBS) : S2k guideline of the German Society of Urology]. / Diagnostik und Therapie der interstitiellen Zystitis (IC/BPS) : S2k-Leitlinie der Deutschen Gesellschaft für Urologie.

In this review article, the authors describe all relevant aspects of the new S2k guideline from the German Society of Urology (Deutschen Gesellschaft für Urologie, DGU) for the diagnosis and treatment of IC/PBS (interstitial cystitis/painful bladder syndrome). A list of necessary and optional examinations and the necessity of diagnosis of exclusion are summarized and evaluated. The treatment options listed (ranging from conservative, oral drug, and complementary medicine to interventional surgical procedures) also give the reader a good overview of the contents of the guideline and possible therapeutic approaches. Finally, the recommendations including consensus of the guideline group are also summarized in various information boxes.

Integrated silicon qubit platform with single-spin addressability, exchange control and single-shot singlet-triplet readout.

Silicon quantum dot spin qubits provide a promising platform for large-scale quantum computation because of their compatibility with conventional CMOS manufacturing and the long coherence times accessible using 28Si enriched material. A scalable error-corrected quantum processor, however, will require control of many qubits in parallel, while performing error detection across the constituent qubits. Spin resonance techniques are a convenient path to parallel two-axis control, while Pauli spin blockade can be used to realize local parity measurements for error detection. Despite this, silicon qubit implementations have so far focused on either single-spin resonance control, or control and measurement via voltage-pulse detuning in the two-spin singlet-triplet basis, but not both simultaneously. Here, we demonstrate an integrated device platform incorporating a silicon metal-oxide-semiconductor double quantum dot that is capable of single-spin addressing and control via electron spin resonance, combined with high-fidelity spin readout in the singlet-triplet basis.

[Epidemiology, diagnostics, therapy, prevention and management of uncomplicated bacterial outpatient acquired urinary tract infections in adult patients : Update 2017 of the interdisciplinary AWMF S3 guideline]. / Epidemiologie, Diagnostik, Therapie, Prävention und Management unkomplizierter, bakterieller, ambulant erworbener Harnwegsinfektionen bei erwachsenen Patienten : Aktualisierung 2017 der interdisziplinären AWMF S3­Leitlinie.

BACKGROUND: Update of the 2010 published evidence-based S3 guideline on epidemiology, diagnostics, therapy and management of uncomplicated, bacterial, outpatient-acquired urinary tract infections in adult patients. The guideline contains current evidence for the rational use of antimicrobial substances, avoidance of inappropriate use of certain antibiotic classes and development of resistance. METHODOLOGY: The update was created under the leadership of the German Association of Urology (DGU). A systematic literature search was conducted for the period 01 January 2008 to 31 December 2015. International guidelines have also been taken into account. Evidence level and risk of bias were used for quality review. RESULTS: Updated information on bacterial susceptibility, success, collateral damage and safety of first- and second-line antibiotics was given. For the treatment of uncomplicated cystitis the first line antibiotics are fosfomycin trometamol, nitrofurantoin, nitroxoline, pivmecillinam, trimethoprim (with consideration of the local resistance rates). Fluoroquinolones and cephalosporins should not be used as first choice antibiotics. In the case of uncomplicated pyelonephritis of mild to moderate forms, preferably cefpodoxime, ceftibuten, ciprofloxacin or levofloxacin should be used as oral antibiotics. CONCLUSION: The updated German S3 guideline provides comprehensive evidence- and consensus-based recommendations on epidemiology, diagnostics, therapy, prevention and management of uncomplicated bacterial outpatient acquired urinary tract infections in adult patients. Antibiotic stewardship aspects have significantly influenced the therapeutic recommendations. A broad implementation in all clinical practice settings is necessary to ensure a foresighted antibiotic policy and thus t improve clinical care.

Repeated quantum error correction on a continuously encoded qubit by real-time feedback.

Reliable quantum information processing in the face of errors is a major fundamental and technological challenge. Quantum error correction protects quantum states by encoding a logical quantum bit (qubit) in multiple physical qubits. To be compatible with universal fault-tolerant computations, it is essential that states remain encoded at all times and that errors are actively corrected. Here we demonstrate such active error correction on a continuously protected logical qubit using a diamond quantum processor. We encode the logical qubit in three long-lived nuclear spins, repeatedly detect phase errors by non-destructive measurements, and apply corrections by real-time feedback. The actively error-corrected qubit is robust against errors and encoded quantum superposition states are preserved beyond the natural dephasing time of the best physical qubit in the encoding. These results establish a powerful platform to investigate error correction under different types of noise and mark an important step towards fault-tolerant quantum information processing.

Loophole-free Bell test using electron spins in diamond: second experiment and additional analysis.

The recently reported violation of a Bell inequality using entangled electronic spins in diamonds (Hensen et al., Nature 526, 682-686) provided the first loophole-free evidence against local-realist theories of nature. Here we report on data from a second Bell experiment using the same experimental setup with minor modifications. We find a violation of the CHSH-Bell inequality of 2.35 ± 0.18, in agreement with the first run, yielding an overall value of S = 2.38 ± 0.14. We calculate the resulting P-values of the second experiment and of the combined Bell tests. We provide an additional analysis of the distribution of settings choices recorded during the two tests, finding that the observed distributions are consistent with uniform settings for both tests. Finally, we analytically study the effect of particular models of random number generator (RNG) imperfection on our hypothesis test. We find that the winning probability per trial in the CHSH game can be bounded knowing only the mean of the RNG bias. This implies that our experimental result is robust for any model underlying the estimated average RNG bias, for random bits produced up to 690 ns too early by the random number generator.

Quantum information. Unconditional quantum teleportation between distant solid-state quantum bits.

Realizing robust quantum information transfer between long-lived qubit registers is a key challenge for quantum information science and technology. Here we demonstrate unconditional teleportation of arbitrary quantum states between diamond spin qubits separated by 3 meters. We prepare the teleporter through photon-mediated heralded entanglement between two distant electron spins and subsequently encode the source qubit in a single nuclear spin. By realizing a fully deterministic Bell-state measurement combined with real-time feed-forward, quantum teleportation is achieved upon each attempt with an average state fidelity exceeding the classical limit. These results establish diamond spin qubits as a prime candidate for the realization of quantum networks for quantum communication and network-based quantum computing.