Quantum circuits with many photons on a programmable nanophotonic chip

Growing interest in quantum computing for practical applications has led to a surge in the availability of programmable machines for executing quantum algorithms1,2. Present-day photonic quantum computers3-7 have been limited either to non-deterministic operation, low photon numbers and rates, or fixed random gate sequences. Here we introduce a full-stack hardware-software system for executing many-photon quantum circuit operations using integrated nanophotonics: a programmable chip, operating at room temperature and interfaced with a fully automated control system. The system enables remote users to execute quantum algorithms that require up to eight modes of strongly squeezed vacuum initialized as two-mode squeezed states in single temporal modes, a fully general and programmable four-mode interferometer, and photon number-resolving readout on all outputs. Detection of multi-photon events with photon numbers and rates exceeding any previous programmable quantum optical demonstration is made possible by strong squeezing and high sampling rates. We verify the non-classicality of the device output, and use the platform to carry out proof-of-principle demonstrations of three quantum algorithms: Gaussian boson sampling, molecular vibronic spectra and graph similarity8. These demonstrations validate the platform as a launchpad for scaling photonic technologies for quantum information processing.

The relationship between stigmatisation and quality of life in Ghanaian women and men with fertility problems: mediating role of coping strategies

INTRODUCTION

Fertility problems may have a devastating impact on the people involved. Specifically, in highly pronatalist settings like Ghana, the personal and social consequences are high. This study focused on the relationship between stigmatisation because of fertility problems and quality of life among Ghanaian women and men, and the possible mediating role of coping strategies.

METHODS

Participants (38 women, 11 men) were recruited with the help of a patient organisation and a hospital in Accra. Standardised instruments were used to measure the stigmatisation of having fertility problems, fertility quality of life and coping with fertility problems. Partial Pearson r correlations were conducted, followed by bootstrapped mediation analyses (PROCESS macro).

RESULTS

Stigmatisation was negatively correlated with fertility quality of life, and fertility quality of life was negatively correlated with active-avoidance coping. Active avoidance coping partially mediated the relationship between being stigmatised because of fertility problems and fertility quality of life.

CONCLUSIONS

Professionals working with people with fertility problems should pay more attention to how people are coping with experiences of stigmatisation.

The social and cultural meanings of infertility for men and women in Zambia: legacy, family and divine intervention

Despite the high prevalence of infertility within the sub-Saharan sterility belt, infertility in Zambia is understudied, particularly from a social perspective. Furthermore, few studies in sub-Saharan Africa include the infertility experiences of men. This article seeks to fill this gap by qualitatively describing the ways in which infertility in Zambia is socially and culturally loaded for both men and women. Demonstrating fertility is necessary to be considered a full adult, a real man or woman, and to leave a legacy after death. People in Zambia, including medical professionals, currently lack the necessary information and access to (or ability to provide) care to effectively resolve fertility issues. Infertile people manage their experience through a variety of social, emotional, spiritual, and medical strategies. However, no solution is considered adequate unless the intervention results in childbirth. In this way, infertility is about producing babies and the social meaning of that process, rather than the raising of children.

Broadband quadrature-squeezed vacuum and nonclassical photon number correlations from a nanophotonic device

We report demonstrations of both quadrature-squeezed vacuum and photon number difference squeezing generated in an integrated nanophotonic device. Squeezed light is generated via strongly driven spontaneous four-wave mixing below threshold in silicon nitride microring resonators. The generated light is characterized with both homodyne detection and direct measurements of photon statistics using photon number-resolving transition-edge sensors. We measure 1.0(1) decibels of broadband quadrature squeezing (~4 decibels inferred on-chip) and 1.5(3) decibels of photon number difference squeezing (~7 decibels inferred on-chip). Nearly single temporal mode operation is achieved, with measured raw unheralded second-order correlations g ⁽²⁾ as high as 1.95(1). Multiphoton events of over 10 photons are directly detected with rates exceeding any previous quantum optical demonstration using integrated nanophotonics. These results will have an enabling impact on scaling continuous variable quantum technology.

Detector-Agnostic Phase-Space Distributions

The representation of quantum states via phase-space functions constitutes an intuitive technique to characterize light. However, the reconstruction of such distributions is challenging as it demands specific types of detectors and detailed models thereof to account for their particular properties and imperfections. To overcome these obstacles, we derive and implement a measurement scheme that enables a reconstruction of phase-space distributions for arbitrary states whose functionality does not depend on the knowledge of the detectors, thus defining the notion of detector-agnostic phase-space distributions. Our theory presents a generalization of well-known phase-space quasiprobability distributions, such as the Wigner function. We implement our measurement protocol, using state-of-the-art transition-edge sensors without performing a detector characterization. Based on our approach, we reveal the characteristic features of heralded single- and two-photon states in phase space and certify their nonclassicality with high statistical significance.

Quantum-enhanced interferometry with large heralded photon-number states

Quantum phenomena such as entanglement can improve fundamental limits on the sensitivity of a measurement probe. In optical interferometry, a probe consisting of N entangled photons provides up to aN enhancement in phase sensitivity compared to a classical probe of the same energy. Here, we employ high-gain parametric down-conversion sources and photon-number-resolving detectors to perform interferometry with heralded quantum probes of sizes up to N = 8 (i.e. measuring up to 16-photon coincidences). Our probes are created by injecting heralded photon-number states into an interferometer, and in principle provide quantum-enhanced phase sensitivity even in the presence of significant optical loss. Our work paves the way towards quantum-enhanced interferometry using large entangled photonic states.

Quantum interference enables constant-time quantum information processing

It is an open question how fast information processing can be performed and whether quantum effects can speed up the best existing solutions. Signal extraction, analysis, and compression in diagnostics, astronomy, chemistry, and broadcasting build on the discrete Fourier transform. It is implemented with the fast Fourier transform (FFT) algorithm that assumes a periodic input of specific lengths, which rarely holds true. A lesser-known transform, the Kravchuk-Fourier (KT), allows one to operate on finite strings of arbitrary length. It is of high demand in digital image processing and computer vision but features a prohibitive runtime. Here, we report a one-step computation of a fractional quantum KT. The quantum d-nary (qudit) architecture we use comprises only one gate and offers processing time independent of the input size. The gate may use a multiphoton Hong-Ou-Mandel effect. Existing quantum technologies may scale it up toward diverse applications.

Identification of nonclassical properties of light with multiplexing layouts

In Sperling et al. [Phys. Rev. Lett. 118, 163602 (2017)], we introduced and applied a detector-independent method to uncover nonclassicality. Here, we extend those techniques and give more details on the performed analysis. We derive a general theory of the positive-operator-valued measure that describes multiplexing layouts with arbitrary detectors. From the resulting quantum version of a multinomial statistics, we infer nonclassicality probes based on a matrix of normally ordered moments. We discuss these criteria and apply the theory to our data which are measured with superconducting transition-edge sensors. Our experiment produces heralded multiphoton states from a parametric down-conversion light source. We show that the known notions of sub-Poisson and sub-binomial light can be deduced from our general approach, and we establish the concept of sub-multinomial light, which is shown to outperform the former two concepts of nonclassicality for our data.

Detector-Independent Verification of Quantum Light

We introduce a method for the verification of nonclassical light which is independent of the complex interaction between the generated light and the material of the detectors. This is accomplished by means of a multiplexing arrangement. Its theoretical description yields that the coincidence statistics of this measurement layout is a mixture of multinomial distributions for any classical light field and any type of detector. This allows us to formulate bounds on the statistical properties of classical states. We apply our directly accessible method to heralded multiphoton states which are detected with a single multiplexing step only and two detectors, which are in our work superconducting transition-edge sensors. The nonclassicality of the generated light is verified and characterized through the violation of the classical bounds without the need for characterizing the used detectors.

Infertility in the Global South: Raising awareness and generating insights for policy and practice

Infertility is a highly prevalent reproductive health condition in the global South, which often has a devastating impact on the people concerned. Yet, thus far it hardly received any attention from policy makers, Non-Governmental Organizations (NGOs) or donors working in the field of Sexual and Reproductive Health and Rights (SRHR). For this reason we have set up a project to increase knowledge and awareness about infertility and childlessness among those stakeholders and organizations and to generate insight into (possible) interventions in this field. The project received a grant by Share-Net International (the Knowledge Platform in the field of SRHR, funded by the Dutch Ministry of Foreign Affairs) and is a unique collaboration between universities, fertility clinics, fertility support groups and the Walking Egg Foundation. The project consists of multimethods studies in Ghana and Kenya as well as dissemination workshops and meetings in these countries and the Netherlands. The first workshops in Kenya have already taken place with successful feedback from stakeholders. In this commentary we provide insight into the project and the main points and recommendations discussed in the Workshops in Kenya.

Detection-loophole-free test of quantum nonlocality, and applications

We present a source of entangled photons that violates a Bell inequality free of the "fair-sampling" assumption, by over 7 standard deviations. This violation is the first reported experiment with photons to close the detection loophole, and we demonstrate enough "efficiency" overhead to eventually perform a fully loophole-free test of local realism. The entanglement quality is verified by maximally violating additional Bell tests, testing the upper limit of quantum correlations. Finally, we use the source to generate "device-independent" private quantum random numbers at rates over 4 orders of magnitude beyond previous experiments.

Biomedical infertility care in sub-Saharan Africa: a social science-- review of current practices, experiences and view points

Some sort of infertility treatments, including the use of advanced reproductive technologies (ARTs), is nowadays provided at several places in sub-Saharan Africa. Yet, to date only a few studies have actually looked into the way these treatments are offered, used and experienced. In this review article the authors present and discuss empirical study findings that give insight into the way biomedical infertility care is provided, considered, experienced and/or used in sub-Saharan African countries. They concentrate on four themes that were often referred to in the reviewed studies and underline the importance of taking into account the local sociocultural context and notions when developing and implementing infertility care, namely: counselling, male involvement, acceptability of ARTs and the use of donor material (semen and embryos). In the conclusion the authors emphasize the importance of preventing infertility as part of integrated reproductive health programs and the need to improve the quality of (low tech) infertility care in the public health sector by means of standardized guidelines, training of health staff and improved counselling. In addition, from a reproductive rights perspective, they support initiatives to introduce low cost ARTs to treat tubal factor related infertility. They also point to potential unintended side effects of the introduction of ARTs and the use of donor material in the sub-Saharan African context, affecting gender inequity and inequity between citizens from different social classes, and argue that such effects should be acknowledged and avoided by all possible means. Finally, they present an agenda for future social science research on this topic in sub-Saharan Africa.

Hunger, waiting time and transport costs: Time to confront challenges to ART adherence in Africa

Adherence levels in Africa have been found to be better than those in the US. However around one out of four ART users fail to achieve optimal adherence, risking drug resistance and negative treatment outcomes. A high demand for 2nd line treatments (currently ten times more expensive than 1st line ART) undermines the sustainability of African ART programs. There is an urgent need to identify context-specific constraints to adherence and implement interventions to address them. We used rapid appraisals (involving mainly qualitative methods) to find out why and when people do not adhere to ART in Uganda, Tanzania and Botswana. Multidisciplinary teams of researchers and local health professionals conducted the studies, involving a total of 54 semi-structured interviews with health workers, 73 semi-structured interviews with ARTusers and other key informants, 34 focus group discussions, and 218 exit interviews with ART users. All the facilities studied in Botswana, Tanzania and Uganda provide ARVs free of charge, but ART users report other related costs (e.g. transport expenditures, registration and user fees at the private health facilities, and lost wages due to long waiting times) as main obstacles to optimal adherence. Side effects and hunger in the initial treatment phase are an added concern. We further found that ART users find it hard to take their drugs when they are among people to whom they have not disclosed their HIV status, such as co-workers and friends. The research teams recommend that (i) health care workers inform patients better about adverse effects; (ii) ART programmes provide transport and food support to patients who are too poor to pay; (iii) recurrent costs to users be reduced by providing three-months, rather than the one-month refills once optimal adherence levels have been achieved; and (iv) pharmacists play an important role in this follow-up care.

Viewpoint: medical infertility care in low income countries: the case for concern in policy and practice

Based on published, 'grey' and anecdotal information, this paper explores some aspects of infertility, its medical treatment and their burden in poor countries. Many cases of infertility result from sexually transmitted infections (STI) and unsafe abortion and there is no doubt that their prevention and adequate treatment are of utmost importance, especially as effective infertility treatment, if any, comes at a high price for the consumer, materially as well as physically. Medical infertility interventions are apt to fail a free market of provision because of major information asymmetry. This renders patients in low-resource countries prone to exploitation, potentially damaging practices and waste of their savings. The authors argue that in countries struggling with limited funds and a range of pressing public health problems, public investment in infertility treatment should not have priority. But governments should take an active role in quality control and regulation of treatment practice, as well as invest in counseling skills for lower-level reproductive health staff to achieve rational referral of patients.

Quality of infertility care in poor-resource areas and the introduction of new reproductive technologies

The quality of infertility care is dependent upon adequate material resources and the appropriate use of it. In addition, a mutual understanding between physicians and patients is necessary. These imperatives are more salient in the era of the new reproductive technologies. However, in poor-resource areas these imperatives are insufficiently met. Moreover, in developing countries the negative consequences of childlessness are much stronger than in Western societies. Until recently, the problem of infertility in Third World countries has received little public attention. A plea is made for a stronger policy interest in Third World infertility care. In this it is important to focus on prevention, appropriate diagnosis and treatment at primary and secondary health-care level and to take the existing cultural beliefs into account.

Social and cultural aspects of infertility in Mozambique

Findings of an anthropological study of socio-cultural aspects of infertility among members of the matrilineal ethnic group Macua in the north of Mozambique are presented. Infertile women apply various strategies to have a child. Traditional healers are visited much more often than the modern hospital, and the explanations the infertile women themselves give for their infertility more often originated from the traditional healers than from the hospital staff. Almost all of the interviewed women commit adultery in the hope to conceive. Some of them apply fostering as a partial solution for childlessness. The Macua infertile women experience various consequences due to their infertility, of which exclusion from certain social activities and traditional ceremonies is perceived as a very problematic one. The matrilineal kinship system means that the husband and his family do not mistreat and repudiate her. Infertility must be considered as a serious reproductive health problem in Mozambique. For the long term preventive measures may be more influential than curative one. The findings of this study can be used to elaborate culturally sensitive health education programmes.