Quantum-enhanced Markov chain Monte Carlo.

Quantum computers promise to solve certain computational problems much faster than classical computers. However, current quantum processors are limited by their modest size and appreciable error rates. Recent efforts to demonstrate quantum speedups have therefore focused on problems that are both classically hard and naturally suited to current quantum hardware, such as sampling from complicated-although not explicitly useful-probability distributions1-3. Here we introduce and experimentally demonstrate a quantum algorithm that is similarly well suited to current hardware, but which samples from complicated distributions arising in several applications. The algorithm performs Markov chain Monte Carlo (MCMC), a prominent iterative technique4, to sample from the Boltzmann distribution of classical Ising models. Unlike most near-term quantum algorithms, ours provably converges to the correct distribution, despite being hard to simulate classically. But like most MCMC algorithms, its convergence rate is difficult to establish theoretically, so we instead analysed it through both experiments and simulations. In experiments, our quantum algorithm converged in fewer iterations than common classical MCMC alternatives, suggesting unusual robustness to noise. In simulations, we observed a polynomial speedup between cubic and quartic over such alternatives. This empirical speedup, should it persist to larger scales, could ease computational bottlenecks posed by this sampling problem in machine learning5, statistical physics6 and optimization7. This algorithm therefore opens a new path for quantum computers to solve useful-not merely difficult-sampling problems.

Distinguishing homolytic vs heterolytic bond dissociation of phenylsulfonium cations with localized active space methods.

Modeling chemical reactions with quantum chemical methods is challenging when the electronic structure varies significantly throughout the reaction and when electronic excited states are involved. Multireference methods, such as complete active space self-consistent field (CASSCF), can handle these multiconfigurational situations. However, even if the size of the needed active space is affordable, in many cases, the active space does not change consistently from reactant to product, causing discontinuities in the potential energy surface. The localized active space SCF (LASSCF) is a cheaper alternative to CASSCF for strongly correlated systems with weakly correlated fragments. The method is used for the first time to study a chemical reaction, namely the bond dissociation of a mono-, di-, and triphenylsulfonium cation. LASSCF calculations generate smooth potential energy scans more easily than the corresponding, more computationally expensive CASSCF calculations while predicting similar bond dissociation energies. Our calculations suggest a homolytic bond cleavage for di- and triphenylsulfonium and a heterolytic pathway for monophenylsulfonium.

N-Electron Valence Perturbation Theory with Reference Wave Functions from Quantum Computing: Application to the Relative Stability of Hydroxide Anion and Hydroxyl Radical.

Quantum simulations of the hydroxide anion and hydroxyl radical are reported, employing variational quantum algorithms for near-term quantum devices. The energy of each species is calculated along the dissociation curve, to obtain information about the stability of the molecular species being investigated. It is shown that simulations restricted to valence spaces incorrectly predict the hydroxyl radical to be more stable than the hydroxide anion. Inclusion of dynamical electron correlation from nonvalence orbitals is demonstrated, through the integration of the variational quantum eigensolver and quantum subspace expansion methods in the workflow of N-electron valence perturbation theory, and shown to correctly predict the hydroxide anion to be more stable than the hydroxyl radical, provided that basis sets with diffuse orbitals are also employed. Finally, we calculate the electron affinity of the hydroxyl radical using an aug-cc-pVQZ basis on IBM's quantum devices.

Challenges in the Use of Quantum Computing Hardware-Efficient Ansätze in Electronic Structure Theory.

Advances in quantum computation for electronic structure, and particularly heuristic quantum algorithms, create an ongoing need to characterize the performance and limitations of these methods. Here we discuss some potential pitfalls connected with the use of hardware-efficient Ansätze in variational quantum simulations of electronic structure. We illustrate that hardware-efficient Ansätze may break Hamiltonian symmetries and yield nondifferentiable potential energy curves, in addition to the well-known difficulty of optimizing variational parameters. We discuss the interplay between these limitations by carrying out a comparative analysis of hardware-efficient Ansätze versus unitary coupled cluster and full configuration interaction, and of second- and first-quantization strategies to encode Fermionic degrees of freedom to qubits. Our analysis should be useful in understanding potential limitations and in identifying possible areas of improvement in hardware-efficient Ansätze.

Prenatal maternal stress during the COVID-19 pandemic and infant regulatory capacity at 3 months: A longitudinal study.

The COVID-19 pandemic is a global traumatic experience for citizens, especially during sensitive time windows of heightened plasticity such as pregnancy and neonatal life. Pandemic-related stress experienced by mothers during pregnancy may act as an early risk factor for infants' regulatory capacity development by altering maternal psychosocial well-being (e.g., increased anxiety, reduced social support) and caregiving environment (e.g., greater parenting stress, impaired mother-infant bonding). The aim of the present longitudinal study was to assess the consequences of pandemic-related prenatal stress on infants' regulatory capacity. A sample of 163 mother-infant dyads was enrolled at eight maternity units in northern Italy. They provided complete data about prenatal stress, perceived social support, postnatal anxiety symptoms, parenting stress, mother-infant bonding, and infants' regulatory capacity at 3 months of age. Women who experienced emotional stress and received partial social support during pregnancy reported higher anxious symptoms. Moreover, maternal postnatal anxiety was indirectly linked to the infants' regulatory capacity at 3 months, mediated by parenting stress and mother-infant bonding. Dedicated preventive interventions should be delivered to mothers and should be focused on protecting the mother-infant dyad from the detrimental effects of pandemic-related stress during the COVID-19 healthcare emergency.

Quantum Algorithms for Quantum Chemistry and Quantum Materials Science.

As we begin to reach the limits of classical computing, quantum computing has emerged as a technology that has captured the imagination of the scientific world. While for many years, the ability to execute quantum algorithms was only a theoretical possibility, recent advances in hardware mean that quantum computing devices now exist that can carry out quantum computation on a limited scale. Thus, it is now a real possibility, and of central importance at this time, to assess the potential impact of quantum computers on real problems of interest. One of the earliest and most compelling applications for quantum computers is Feynman's idea of simulating quantum systems with many degrees of freedom. Such systems are found across chemistry, physics, and materials science. The particular way in which quantum computing extends classical computing means that one cannot expect arbitrary simulations to be sped up by a quantum computer, thus one must carefully identify areas where quantum advantage may be achieved. In this review, we briefly describe central problems in chemistry and materials science, in areas of electronic structure, quantum statistical mechanics, and quantum dynamics that are of potential interest for solution on a quantum computer. We then take a detailed snapshot of current progress in quantum algorithms for ground-state, dynamics, and thermal-state simulation and analyze their strengths and weaknesses for future developments.

Post-partum Women's Anxiety and Parenting Stress: Home-Visiting Protective Effect During the COVID-19 Pandemic.

OBJECTIVES: The COVID-19 pandemic resulted in a particularly adverse and stressful environment for expecting mothers, possibly enhancing feelings of anxiety and parenting stress. The present work assesses mothers' anxiety levels at delivery and parenting stress after 3 months as moderated by home-visiting sessions. METHODS: Women (n = 177) in their second or third trimester of pregnancy during the COVID-19 lockdown were enrolled in northern Italy and split into those who did and did not receive home visits. After 3 months, the association between anxiety at delivery and parenting stress was assessed with bivariate correlations in the whole sample and comparing the two groups. RESULTS: Higher anxiety at birth correlated with greater perceived stress after 3 months. Mothers who received at least one home-visiting session reported lower parenting stress at 3 months than counterparts who did not receive home visits. CONCLUSIONS FOR PRACTICE: The perinatal period is a sensitive time window for mother-infant health, especially during a critical time like the COVID-19 pandemic. We suggest that home-visiting programs could be beneficial during global healthcare emergencies to promote maternal well-being after delivery.

Immune response in children with COVID-19 is characterized by lower levels of T-cell activation than infected adults.

Study of immunological features of immune response in 14 children (aged from 12 days up to 15 years) and of 10 adults who developed COVID-19 show increased number of activated CD4 and CD8 cells expressing DR and higher plasmatic levels of IL-12 and IL-1ß in adults with COVID-19, but not in children. In addition, plasmatic levels of CCL5/RANTES are higher in children and adults with COVID-19, while CXCL9/MIG was only increased in adults. Higher number of activated T cells and expression of IL-12 and CXCL9 suggest prominent Th1 polarization of immune response against SARS-CoV2 in infected adults as compared with children.

Breast cancer and circadian disruption from electric lighting in the modern world.

Breast cancer is the leading cause of cancer death among women worldwide, and there is only a limited explanation of why. Risk is highest in the most industrialized countries but also is rising rapidly in the developing world. Known risk factors account for only a portion of the incidence in the high-risk populations, and there has been considerable speculation and many false leads on other possibly major determinants of risk, such as dietary fat. A hallmark of industrialization is the increasing use of electricity to light the night, both within the home and without. It has only recently become clear that this evolutionarily new and, thereby, unnatural exposure can disrupt human circadian rhythmicity, of which three salient features are melatonin production, sleep, and the circadian clock. A convergence of research in cells, rodents, and humans suggests that the health consequences of circadian disruption may be substantial. An innovative experimental model has shown that light at night markedly increases the growth of human breast cancer xenografts in rats. In humans, the theory that light exposure at night increases breast cancer risk leads to specific predictions that are being tested epidemiologically: evidence has accumulated on risk in shift workers, risk in blind women, and the impact of sleep duration on risk. If electric light at night does explain a portion of the breast cancer burden, then there are practical interventions that can be implemented, including more selective use of light and the adoption of recent advances in lighting technology and application.

Quantum computation of dominant products in lithium-sulfur batteries.

Quantum chemistry simulations of some industrially relevant molecules are reported, employing variational quantum algorithms for near-term quantum devices. The energies and dipole moments are calculated along the dissociation curves for lithium hydride (LiH), hydrogen sulfide, lithium hydrogen sulfide, and lithium sulfide. In all cases, we focus on the breaking of a single bond to obtain information about the stability of the molecular species being investigated. We calculate energies and a variety of electrostatic properties of these molecules using classical simulators of quantum devices, with up to 21 qubits for lithium sulfide. Moreover, we calculate the ground-state energy and dipole moment along the dissociation pathway of LiH using IBM quantum devices. This is the first example, to the best of our knowledge, of dipole moment calculations being performed on quantum hardware.

Quantum simulation of electronic structure with a transcorrelated Hamiltonian: improved accuracy with a smaller footprint on the quantum computer.

Quantum simulations of electronic structure with a transformed Hamiltonian that includes some electron correlation effects are demonstrated. The transcorrelated Hamiltonian used in this work is efficiently constructed classically, at polynomial cost, by an approximate similarity transformation with an explicitly correlated two-body unitary operator. This Hamiltonian is Hermitian, includes no more than two-particle interactions, and is free of electron-electron singularities. We investigate the effect of such a transformed Hamiltonian on the accuracy and computational cost of quantum simulations by focusing on a widely used solver for the Schrödinger equation, namely the variational quantum eigensolver method, based on the unitary coupled cluster with singles and doubles (q-UCCSD) Ansatz. Nevertheless, the formalism presented here translates straightforwardly to other quantum algorithms for chemistry. Our results demonstrate that a transcorrelated Hamiltonian, paired with extremely compact bases, produces explicitly correlated energies comparable to those from much larger bases. For the chemical species studied here, explicitly correlated energies based on an underlying 6-31G basis had cc-pVTZ quality. The use of the very compact transcorrelated Hamiltonian reduces the number of CNOT gates required to achieve cc-pVTZ quality by up to two orders of magnitude, and the number of qubits by a factor of three.

Recent developments in the PySCF program package.

PySCF is a Python-based general-purpose electronic structure platform that supports first-principles simulations of molecules and solids as well as accelerates the development of new methodology and complex computational workflows. This paper explains the design and philosophy behind PySCF that enables it to meet these twin objectives. With several case studies, we show how users can easily implement their own methods using PySCF as a development environment. We then summarize the capabilities of PySCF for molecular and solid-state simulations. Finally, we describe the growing ecosystem of projects that use PySCF across the domains of quantum chemistry, materials science, machine learning, and quantum information science.

Association of the CFH Y402H Polymorphism with the 1-Year Response of Exudative AMD to Intravitreal Anti-VEGF Treatment in the Brazilian Population.

AIM: Evidence of the relationship between the polymorphism of the complement factor H (CFH) gene at position 402 (Y402H) and the response to the treatment of wet AMD is controversial. The aim of this study was to compare the functional and morphological 1-year evolution of patients with exudative AMD treated with antivascular endothelial growth factor (VEGF) drugs with the CFH Y402H polymorphism in the Brazilian population. METHODS: Forty-six patients treated for wet AMD with bevacizumab or ranibizumab in a pro re nata regimen were included. The evolution of best-corrected visual acuity (BCVA) and central retinal thickness (CRT), and the number of injections over 1 year of follow-up were correlated with CFH genotypes. RESULTS: The analysis of variance for the difference between the BCVA denoted as logMAR (logarithm of the minimum angle of resolution) values showed an improvement at 1 year when compared to baseline (p = 0.039). Profile contrast analysis showed that this difference was significant only in the group without the C allele (p = 0.049), without significance in patients presenting with the risk allele (p = 0.241). CRT showed a mean reduction at 1 year compared to baseline (p < 0.001). Significant differences in the profile contrast test were found in the group without the C allele (p < 0.001) and in patients with the risk allele (p = 0.002). No difference was found in the number of injections among the different groups (p = 0.787). CONCLUSIONS: The presence of the risk allele of the Y402H polymorphism in the CFH gene was related to a less favorable evolution over 1 year in this sample of the Brazilian population with exudative AMD who were being treated with anti-VEGF drugs. In agreement with similar previous studies, this study concludes that the CFH risk genotypes may affect the disease response to treatment.

Communication: Calculation of interatomic forces and optimization of molecular geometry with auxiliary-field quantum Monte Carlo.

We propose an algorithm for accurate, systematic, and scalable computation of interatomic forces within the auxiliary-field quantum Monte Carlo (AFQMC) method. The algorithm relies on the Hellmann-Feynman theorem and incorporates Pulay corrections in the presence of atomic orbital basis sets. We benchmark the method for small molecules by comparing the computed forces with the derivatives of the AFQMC potential energy surface and by direct comparison with other quantum chemistry methods. We then perform geometry optimizations using the steepest descent algorithm in larger molecules. With realistic basis sets, we obtain equilibrium geometries in agreement, within statistical error bars, with experimental values. The increase in computational cost for computing forces in this approach is only a small prefactor over that of calculating the total energy. This paves the way for a general and efficient approach for geometry optimization and molecular dynamics within AFQMC.

Prospectively-followed pregnancies in patients with inflammatory arthritis taking biological drugs: an Italian multicentre study.

OBJECTIVES: Information on new drugs does not include their possible effects on pregnancy because pregnant women are excluded from clinical trials. Although not classified as teratogenic in animals, limited data is available on biological anti-rheumatic agents and their safety in human pregnancy. The aim of the study is to evaluate the safety of biological drugs in pregnant patients with chronic arthritis. METHODS: Pregnancy outcome and maternal disease variations were prospectively followed in six Italian Rheumatology Centres. Patients exposed to biological agents during the periconceptional period or during pregnancy were included in the study. The occurrence of congenital malformations as well as the obstetric and neonatal outcomes were assessed. RESULTS: Between 1999 and 2013 we identified 79 exposed pregnancies in 67 women affected by different rheumatic diseases with peripheral chronic arthritis. At the time of the start of pregnancy, 56 patients were taking etanercept, 13 adalimumab, 3 infliximab, 2 each certolizumab-pegol and rituximab, 1 each golimumab, anakinra and abatacept. Biological treatment was stopped after a mean of 41 days since documented pregnancy. Live births were reported in 66% of pregnancies. The rate of spontaneous pregnancy loss was 20%. Only one congenital malformation was reported. CONCLUSIONS: TNF-alpha inhibitors can be considered safe in the periconception period, representing a possible therapeutic choice also in young women affected by an aggressive form of chronic arthritis and hoping for a pregnancy. Reports of exposure during 2nd/3rd trimester are still limited and suggest caution. Experience with abatacept, tocilizumab, anakinra and rituximab in pregnancy is insufficient.

Pharmacogenetic Effect of Complement Factor H Gene Polymorphism in Response to the Initial Intravitreal Injection of Bevacizumab for Wet Age-Related Macular Degeneration.

PURPOSE: To compare the functional and morphological response to the initial intravitreal (IVT) injection of bevacizumab in exudative age-related macular degeneration (AMD) patients with the complement factor H (CFH) gene polymorphism T1277C in the Brazilian population. METHODS: Twenty-five unrelated patients with treatment-naive exudative AMD underwent an IVT injection of 1.25 mg bevacizumab at the initial presentation (D0) and were reexamined 7 days (D7) and 28 days (D28) later. The time and extent of visual acuity (VA) and central retinal thickness (CRT) changes were evaluated according to the presence of the T1277C polymorphism. RESULTS: In the homozygous risk group (CC), VA improvement was detected mostly from D7 to D28, while in the heterozygous (CT) and homozygous for the wild-type allele (TT) groups, functional response occurred earlier, from D0 to D7. Morphological response to the first IVT injection of bevacizumab was significant in the CT and TT groups, while the CC group presented no significant change in CRT up to D28. CONCLUSION: The CC variant of the CFH gene polymorphism T1277C is related to delayed functional and limited morphological response to the initial IVT injection of bevacizumab in exudative AMD patients in a sample of the Brazilian population.

Anti-Ro/SSA-p200 antibodies in the prediction of congenital heart block. An Italian multicentre cross-sectional study on behalf of the 'Forum Interdisciplinare per la Ricerca nelle Malattie Autoimmuni (FIRMA) Group'.

OBJECTIVES: To verify the association between the presence of specific anti-52 Ro/SSA-p200 antibodies and congenital heart block (CHB). METHODS: 207 pregnant Italian women carrying anti-Ro/SSA Ab were retrospectively evaluated. Anti-p200 Ab were investigated in the mothers' sera by ELISA (Euro-Diagnostica,Wieslab SS-A p200). RESULTS: CHB occurred in 42 children (34 complete CHB), whereas 165 were not affected. All CHB cases were previously identified with an ELISA screening for anti-Ro/SSA 60 kD Ab. Anti-p200 Ab were more frequently positive (81.0% vs. 59.1%, p=0.013) and at a higher titer in CHB mothers (Absorbance ratio: 2.030 (0.208-4.052) vs. 0.925 (0.200-3.816); p=0.017). This association was maintained even when the 42 mothers of children with CHB were compared with a control group matched for age and diagnosis (80.9% vs. 50.0%; p=0.006). The presence of anti-p200 Ab provided an odds ratio (OR) for CHB of 2.98 (CI: 1.30-6.83), which was higher than that of other variables, such as maternal disease and other antibody specificities. CHB risk significantly decreased in the absence of this fine specificity (OR:0.34, CI: 0.15-0.77). However, while the negative predictive value related to anti-Ro/SSA 60 kD Ab ELISA was 100%, almost 20% of mothers negative for anti-p200 Ab delivered babies with CHB. CONCLUSIONS: Anti-p200 antibodies seem to be associated with CHB with a higher probability than anti-Ro/SSA Ab, and therefore may be an additional test to identify mothers at higher risk to deliver affected children. An ELISA screening for anti-Ro/SSA 60 kD Ab is nevertheless mandatory given the probability of developing CHB also in the absence of anti-p200 Ab.

Diagnostic accuracy and prognostic value of the CD64 index in very low birth weight neonates as a marker of early-onset sepsis.

OBJECTIVE: To assess the diagnostic and prognostic utility of CD64 expression as a marker of early-onset sepsis (EOS) in very low birth weight (VLBW) neonates. METHODS: Neutrophil CD64 expression (CD64 index) was assessed in 129 VLBW neonates within 72 h after birth. The accuracy of the CD64 index in predicting EOS was determined by receiver operating characteristic curve analysis. The relationship between the expression of the CD64 index and neonatal outcomes was evaluated by multivariate analysis. RESULTS: The highest performance of the CD64 index was achieved at 24 h after birth; accuracy, sensitivity, and negative predictive values were 0.85, 0.89, and 0.99, respectively, with a cut-off value of 2.4. The increased expression of CD64 index was significantly associated with subsequent infections (relative risk 1.54; 95% confidence interval 1.02-2.33). CONCLUSIONS: The CD64 index could be used as a reliable marker of EOS in VLBW neonates and it is an independent risk factor for late-onset infections.

Quantum Algorithm for Imaginary-Time Green's Functions.

Green's function methods lead to ab initio, systematically improvable simulations of molecules and materials while providing access to multiple experimentally observable properties such as the density of states and the spectral function. The calculation of the exact one-particle Green's function remains a significant challenge for classical computers and was attempted only on very small systems. Here, we present a hybrid quantum-classical algorithm to calculate the imaginary-time one-particle Green's function. The proposed algorithm combines the variational quantum eigensolver and the quantum subspace expansion methods to calculate Green's function in Lehmann's representation. We demonstrate the validity of this algorithm by simulating H2 and H4 on quantum simulators and on IBM's quantum devices.