Dynamics of magnetization at infinite temperature in a Heisenberg spin chain.

Understanding universal aspects of quantum dynamics is an unresolved problem in statistical mechanics. In particular, the spin dynamics of the one-dimensional Heisenberg model were conjectured as to belong to the Kardar-Parisi-Zhang (KPZ) universality class based on the scaling of the infinite-temperature spin-spin correlation function. In a chain of 46 superconducting qubits, we studied the probability distribution of the magnetization transferred across the chain's center, [Formula: see text]. The first two moments of [Formula: see text] show superdiffusive behavior, a hallmark of KPZ universality. However, the third and fourth moments ruled out the KPZ conjecture and allow for evaluating other theories. Our results highlight the importance of studying higher moments in determining dynamic universality classes and provide insights into universal behavior in quantum systems.

Stable quantum-correlated many-body states through engineered dissipation.

Engineered dissipative reservoirs have the potential to steer many-body quantum systems toward correlated steady states useful for quantum simulation of high-temperature superconductivity or quantum magnetism. Using up to 49 superconducting qubits, we prepared low-energy states of the transverse-field Ising model through coupling to dissipative auxiliary qubits. In one dimension, we observed long-range quantum correlations and a ground-state fidelity of 0.86 for 18 qubits at the critical point. In two dimensions, we found mutual information that extends beyond nearest neighbors. Lastly, by coupling the system to auxiliaries emulating reservoirs with different chemical potentials, we explored transport in the quantum Heisenberg model. Our results establish engineered dissipation as a scalable alternative to unitary evolution for preparing entangled many-body states on noisy quantum processors.

Abnormal cerebral hemodynamics and blood-brain barrier permeability detected with perfusion MRI in systemic lupus erythematosus patients.

OBJECTIVE: Dynamic susceptibility contrast (DSC) magnetic resonance imaging (MRI) has previously shown alterations in cerebral perfusion in patients with systemic lupus erythematosus (SLE). However, the results have been inconsistent, in particular regarding neuropsychiatric (NP) SLE. Thus, we investigated perfusion-based measures in different brain regions in SLE patients with and without NP involvement, and additionally, in white matter hyperintensities (WMHs), the most common MRI pathology in SLE patients. MATERIALS AND METHODS: We included 3 T MRI images (conventional and DSC) from 64 female SLE patients and 19 healthy controls (HC). Three different NPSLE attribution models were used: the Systemic Lupus International Collaborating Clinics (SLICC) A model (13 patients), the SLICC B model (19 patients), and the American College of Rheumatology (ACR) case definitions for NPSLE (38 patients). Normalized cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) were calculated in 26 manually drawn regions of interest and compared between SLE patients and HC, and between NPSLE and non-NPSLE patients. Additionally, normalized CBF, CBV and MTT, as well as absolute values of the blood-brain barrier leakage parameter (K2) were investigated in WMHs compared to normal appearing white matter (NAWM) in the SLE patients. RESULTS: After correction for multiple comparisons, the most prevalent finding was a bilateral significant decrease in MTT in SLE patients compared to HC in the hypothalamus, putamen, right posterior thalamus and right anterior insula. Significant decreases in SLE compared to HC were also found for CBF in the pons, and for CBV in the bilateral putamen and posterior thalamus. Significant increases were found for CBF in the posterior corpus callosum and for CBV in the anterior corpus callosum. Similar patterns were found for both NPSLE and non-NPSLE patients for all attributional models compared to HC. However, no significant perfusion differences were revealed between NPSLE and non-NPSLE patients regardless of attribution model. The WMHs in SLE patients showed a significant increase in all perfusion-based metrics (CBF, CBV, MTT and K2) compared to NAWM. CONCLUSION: Our study revealed perfusion differences in several brain regions in SLE patients compared to HC, independently of NP involvement. Furthermore, increased K2 in WMHs compared to NAWM may indicate blood-brain barrier dysfunction in SLE patients. We conclude that our results show a robust cerebral perfusion, independent from the different NP attribution models, and provide insight into potential BBB dysfunction and altered vascular properties of WMHs in female SLE patients. Despite SLE being most prevalent in females, a generalization of our conclusions should be avoided, and future studies including all sexes are needed.

Formation of robust bound states of interacting microwave photons.

Systems of correlated particles appear in many fields of modern science and represent some of the most intractable computational problems in nature. The computational challenge in these systems arises when interactions become comparable to other energy scales, which makes the state of each particle depend on all other particles1. The lack of general solutions for the three-body problem and acceptable theory for strongly correlated electrons shows that our understanding of correlated systems fades when the particle number or the interaction strength increases. One of the hallmarks of interacting systems is the formation of multiparticle bound states2-9. Here we develop a high-fidelity parameterizable fSim gate and implement the periodic quantum circuit of the spin-½ XXZ model in a ring of 24 superconducting qubits. We study the propagation of these excitations and observe their bound nature for up to five photons. We devise a phase-sensitive method for constructing the few-body spectrum of the bound states and extract their pseudo-charge by introducing a synthetic flux. By introducing interactions between the ring and additional qubits, we observe an unexpected resilience of the bound states to integrability breaking. This finding goes against the idea that bound states in non-integrable systems are unstable when their energies overlap with the continuum spectrum. Our work provides experimental evidence for bound states of interacting photons and discovers their stability beyond the integrability limit.

Noise-resilient edge modes on a chain of superconducting qubits.

Inherent symmetry of a quantum system may protect its otherwise fragile states. Leveraging such protection requires testing its robustness against uncontrolled environmental interactions. Using 47 superconducting qubits, we implement the one-dimensional kicked Ising model, which exhibits nonlocal Majorana edge modes (MEMs) with [Formula: see text] parity symmetry. We find that any multiqubit Pauli operator overlapping with the MEMs exhibits a uniform late-time decay rate comparable to single-qubit relaxation rates, irrespective of its size or composition. This characteristic allows us to accurately reconstruct the exponentially localized spatial profiles of the MEMs. Furthermore, the MEMs are found to be resilient against certain symmetry-breaking noise owing to a prethermalization mechanism. Our work elucidates the complex interplay between noise and symmetry-protected edge modes in a solid-state environment.

Cognitive performance in systemic lupus erythematosus patients: a cross-sectional and longitudinal study.

BACKGROUND: Previous research has provided evidence for cognitive dysfunction as a common symptom of systemic lupus erythematosus (SLE). In light of this, the primary goal of this study was to investigate how cognitive impairment in this patient group develops over time. In addition, the present dataset contributes to delineating the specific abilities that are impaired in SLE patients as well as answering the question whether the disease affects the cognition of SLE patients with neuropsychiatric manifestations (NPSLE) and without (non-NPSLE) in distinct ways. METHODS: 91 female participants (33 NPSLE, 29 non-NPSLE, 29 healthy controls (HC)) underwent standardized neurocognitive testing. A total of ten different cognitive abilities were assessed, among others executive function, memory, and attention. Some of the participants (30 NPSLE patients, 22 non-NPSLE, 13 HC) were tested twice (mean time between testing sessions: 50 months) to enable longitudinal tracking of cognitive abilities. Analyses of Variance (ANOVA) were conducted to determine whether cognitive performance differed cross-sectionally between the groups. Linear mixed effects models were fit to investigate performance differences between the groups over time. RESULTS: Cross-sectional analysis at follow-up demonstrated that the cognitive performance of both NPSLE and non-NPSLE was significantly lower than that of HC for the motor speed and the psychomotor speed domain. Additionally, NPSLE patients performed significantly weaker than HC in the complex attention domain. At the same time, the cross-sectional data did not yield any support for performance differences between NPSLE and non-NPSLE patients. Weak positive correlations between disease duration and psychomotor speed, motor speed and reaction time emerged. A temporal progression of cognitive dysfunction in SLE patients was not confirmed. CONCLUSIONS: Cognitive performance is affected in both non-NPSLE and NPSLE patients. However, a linear decline in performance over time could not be verified. More in-depth longitudinal assessments of cognition in SLE patients are needed to establish how cognitive abilities in this patient population develop over time.

Realizing topologically ordered states on a quantum processor.

The discovery of topological order has revised the understanding of quantum matter and provided the theoretical foundation for many quantum error­correcting codes. Realizing topologically ordered states has proven to be challenging in both condensed matter and synthetic quantum systems. We prepared the ground state of the toric code Hamiltonian using an efficient quantum circuit on a superconducting quantum processor. We measured a topological entanglement entropy near the expected value of ­ln2 and simulated anyon interferometry to extract the braiding statistics of the emergent excitations. Furthermore, we investigated key aspects of the surface code, including logical state injection and the decay of the nonlocal order parameter. Our results demonstrate the potential for quantum processors to provide insights into topological quantum matter and quantum error correction.

Accurately computing the electronic properties of a quantum ring.

A promising approach to study condensed-matter systems is to simulate them on an engineered quantum platform1-4. However, the accuracy needed to outperform classical methods has not been achieved so far. Here, using 18 superconducting qubits, we provide an experimental blueprint for an accurate condensed-matter simulator and demonstrate how to investigate fundamental electronic properties. We benchmark the underlying method by reconstructing the single-particle band structure of a one-dimensional wire. We demonstrate nearly complete mitigation of decoherence and readout errors, and measure the energy eigenvalues of this wire with an error of approximately 0.01 rad, whereas typical energy scales are of the order of 1 rad. Insight into the fidelity of this algorithm is gained by highlighting the robust properties of a Fourier transform, including the ability to resolve eigenenergies with a statistical uncertainty of 10-4 rad. We also synthesize magnetic flux and disordered local potentials, which are two key tenets of a condensed-matter system. When sweeping the magnetic flux we observe avoided level crossings in the spectrum, providing a detailed fingerprint of the spatial distribution of local disorder. By combining these methods we reconstruct electronic properties of the eigenstates, observing persistent currents and a strong suppression of conductance with added disorder. Our work describes an accurate method for quantum simulation5,6 and paves the way to study new quantum materials with superconducting qubits.

Repetitive non-thermal melting as a timing monitor for femtosecond pump/probe X-ray experiments.

Time-resolved optical pump/X-ray probe experiments are often used to study structural dynamics. To ensure high temporal resolution, it is necessary to monitor the timing between the X-ray pulses and the laser pulses. The transition from a crystalline solid material to a disordered state in a non-thermal melting process can be used as a reliable timing monitor. We have performed a study of the non-thermal melting of InSb in single-shot mode, where we varied the sample temperature in order to determine the conditions required for repetitive melting. We show how experimental conditions affect the feasibility of such a timing tool.

Observation of Broadband Entanglement in Microwave Radiation from a Single Time-Varying Boundary Condition.

Entangled pairs of microwave photons are commonly produced in the narrow frequency band of a resonator, which represents a modified vacuum density of states. We generate and investigate the entanglement of a stream of photon pairs, generated in a semi-infinite broadband transmission line, terminated by a superconducting quantum interference device (SQUID). A weak pump signal modulates the SQUID inductance, resulting in a single time-varying boundary condition, and we detect all four quadratures of the microwave radiation emitted at two different frequencies separated by 0.7 GHz. Power calibration is done in situ, and we find positive logarithmic negativity and two-mode squeezing below the vacuum in the observed radiation, indicating entanglement.

Role of Thermal Equilibrium Dynamics in Atomic Motion during Nonthermal Laser-Induced Melting.

This study shows that initial atomic velocities as given by thermodynamics play an important role in the dynamics of phase transitions. We tracked the atomic motion during nonthermal laser-induced melting of InSb at different initial temperatures. The ultrafast atomic motion following bond breaking can in general be governed by two mechanisms: the random velocity of each atom at the time of bond breaking (inertial model), and the forces acting on the atoms after bond breaking. The melting dynamics was found to follow the inertial model over a wide temperature range.

Good survival rates in systemic lupus erythematosus in southern Sweden, while the mortality rate remains increased compared with the population.

OBJECTIVE: To ascertain the mortality rate and causes of death in patients with systemic lupus erythematosus (SLE) within a defined region in southern Sweden during the time period 1981-2014 and determine whether these have changed over time. METHODS: In 1981, a prospective observation study of patients with SLE was initiated in southern Sweden. All incident SLE patients within a defined geographic area were identified using previously validated methods including diagnosis and immunology registers. Patients with a confirmed SLE diagnosis were then followed prospectively at the Department of Rheumatology in Lund. Clinical data was collected at regular visits. Patients were recruited from 1981 to 2006 and followed until 2014. The patient cohort was split into two groups based on the year of diagnosis to determine secular trends. Causes of death were retrieved from medical records and from the cause of death registry at The National Board of Health and Welfare in Sweden. RESULTS: In all, 175 patients were diagnosed with SLE during the study period. A total of 60 deaths occurred during a total of 3053 years of follow-up. In the first half of the study inclusion period 46 patients died, compared with 14 in the latter. The majority of patients (51.7%) died of cardiovascular disease. Infections caused 15% of the deaths and malignancy was the cause of death in 13.3% of patients. SLE was the main cause of death for 6.7% of the patients and a contributing factor for half of the patients. Standardized mortality ratio was increased in patients by a factor of 2.5 compared with the general population. Deaths occurred at an even rate throughout the whole observation period. No significant difference in standardized mortality ratio was observed between genders but was increased in older female patients. Furthermore, secular mortality trends were not identified. CONCLUSIONS: In this long-term epidemiologic follow-up study of incident SLE, we report a substantially raised mortality rate amongst SLE patients compared with the general population. The mortality rates have not changed significantly during the observation period that spanned three decades. The main cause of death was cardiovascular disease and this finding was consistent over time.

Generation of a large compressive strain wave in graphite by ultrashort-pulse laser irradiation.

We have studied strain wave generation in graphite induced by an intense ultrashort laser pulse. The study was performed in the intensity regime above the ablation threshold of graphite. The aim was to maximize the strain and, thus, also the internal pressure (stress). Laser pulses with a 1 ps temporal duration melt the surface of graphite resulting in a molten material which initially exists at the solid density. As the molten material expands, a compressive strain wave starts propagating into the crystal below the molten layer. The strain pulse was studied with time-resolved X-ray diffraction. At a temporal delay of 100 ps after laser excitation, we observed >10% compressive strain, which corresponds to a pressure of 7.2 GPa. This strain could be reproduced by hydrodynamic simulations, which also provided a temperature map as a function of time and depth.

White matter lesions and brain atrophy in systemic lupus erythematosus patients: correlation to cognitive dysfunction in a cohort of systemic lupus erythematosus patients using different definition models for neuropsychiatric systemic lupus erythematosus.

Aim The aim of this study was to evaluate the extent of white matter lesions, atrophy of the hippocampus and corpus callosum, and their correlation with cognitive dysfunction (CD), in patients diagnosed with systemic lupus erythematosus (SLE). Methods Seventy SLE patients and 25 healthy individuals (HIs) were included in the study. To evaluate the different SLE and neuropsychiatric SLE (NPSLE) definition schemes, patients were grouped both according to the American College of Rheumatology (ACR) definition, as well as the more stringent ACR-Systemic Lupus International Collaborating Clinics definition. Patients and HIs underwent a 3 Tesla brain MRI and a standardized neuropsychological test. MRI data were evaluated for number and volume of white matter lesions and atrophy of the hippocampus and corpus callosum. Differences between groups and subgroups were evaluated for significance. Number and volume of white matter lesions and atrophy of the hippocampus and corpus callosum were correlated to cognitive dysfunction. Results The total volume of white matter lesions was significantly larger in SLE patients compared to HIs ( p = 0.004). However, no significant differences were seen between the different SLE subgroups. Atrophy of the bilateral hippocampus was significantly more pronounced in patients with NPSLE compared to those with non-NPSLE (right: p = 0.010; left p = 0.023). Significant negative correlations between cognitive test scores on verbal memory and number and volume of white matter lesions were present. Conclusion SLE patients have a significantly larger volume of white matter lesions on MRI compared to HIs and the degree of white matter lesion volume correlates to cognitive dysfunction, specifically to verbal memory. No significant differences in the number or volume of white matter lesions were identified between subgroups of SLE patients regardless of the definition model used.

Tumour necrosis factor-α/etanercept complexes in serum predict long-term efficacy of etanercept treatment in seronegative rheumatoid arthritis.

OBJECTIVE: To study whether serum levels of tumour necrosis factor-α (TNF-α), free or bound to etanercept, in biological-naïve adults with rheumatoid arthritis (RA) could predict the long-term efficacy of etanercept, measured as drug survival. METHOD: We identified 145 biological-naïve patients with RA starting treatment with etanercept at the Department of Rheumatology, Skåne University Hospital (1999-2008), of whom 16 had seronegative and 129 seropositive RA. TNF-α in serum was quantified using enzyme-linked immunosorbent assay in samples from the onset of treatment and at 6 week follow-up. Drug survival time was used to evaluate the long-term efficacy of etanercept. RESULTS: Levels of TNF-α were significantly increased at follow-up compared to at the start. At the 6 week follow-up, circulating TNF-α mainly comprised TNF-α in complex with etanercept. Longer drug survival time correlated with increased TNF-α at 6 week follow-up in the patients with seronegative RA, but not in the seropositive patients. CONCLUSION: We demonstrated that levels of circulating TNF-α increased in almost all individuals after initiation of treatment with etanercept and that this increase mainly comprised TNF-α in complex with etanercept. More importantly, this increase may predict drug survival in adults with seronegative, but not seropositive, RA and suggests that measuring TNF-α/etanercept complexes in serum may be relevant in patients with seronegative RA.

Stress-induced release of the S100A8/A9 alarmin is elevated in coronary artery disease patients with impaired cortisol response.

Psychological stress is thought to be an important trigger of cardiovascular events, yet the involved pathways and mediators are largely unknown. Elevated systemic levels of the pro-inflammatory alarmin S100A8/A9 correlate with poor prognosis in coronary artery disease (CAD) patients. Here, we investigated the links between S100A8/A9 release and parameters of anti-inflammatory glucocorticoid secretion in two different cohorts subjected to a psychological stress test. In the first cohort of 60 CAD patients, psychological stress induced a rapid increase of circulating S100A8/A9. This rapid S100A8/A9 response strongly correlated with elevated evening saliva cortisol levels, suggesting an association with a dysregulated hypothalamic-pituitary-adrenal (HPA) axis. In the second cohort of 27 CAD patients and 28 controls, elevated S100A8/A9 levels were still detectable 24 h after stress in 40% of patients and 36% of controls, with a tendency for higher levels in patients. The sustained S100A8/A9 response was associated with a poor rapid cortisol release after stress in patients, but not in the control group. Our findings reveal for the first time that acute psychological stress induces elevated levels of S100A8/A9. We also provide hypothesis-generating evidence that dysregulated cortisol secretion in CAD patients might be associated with an exaggerated pro-inflammatory S100A8/A9 response.

Communication: Demonstration of a 20 ps X-ray switch based on a photoacoustic transducer.

We have studied an X-ray switch based on a gold coated indium antimonide crystal using time-resolved X-ray diffraction and demonstrated that the switch could reduce the pulse duration of a 100 ps X-ray pulse down to 20 ps with a peak reflectivity of 8%. We have used a dynamical diffraction code to predict the performance of the switch, which was then confirmed experimentally. The experiment was carried out at the FemtoMAX beamline at the short-pulse facility of the MAX IV laboratory. The performance and limitation of the switch are discussed in terms of acoustic transport properties between the two materials and the electron transport properties of gold.

Treatment with belimumab in systemic lupus erythematosus does not impair antibody response to 13-valent pneumococcal conjugate vaccine.

Background/purpose The objective of this study was to explore the impact of systemic lupus erythematosus and belimumab given in addition to standard of care therapy on 13-valent conjugated pneumococcal vaccine (PCV13) response. Methods Forty-seven systemic lupus erythematosus patients and 21 healthy controls were immunized with a single dose of 13-valent conjugated pneumococcal vaccine. Forty systemic lupus erythematosus patients were treated with traditional disease-modifying anti rheumatic drugs, 11 of those received belimumab in addition, and 32 patients were treated with concomitant prednisolone. Quantification of serotype specific IgG levels to 12 pneumococcal capsular polysaccharides was performed in serum taken before and four to six weeks after vaccination using multiplex fluorescent microsphere immunoassay. IgG levels against serotypes 23F and 6B were also analyzed using standard enzyme-linked immunosorbent assays. Opsonophagocytic assay was performed on serotype 23F to evaluate the functionality of the antibodies. Pre- and post-vaccination log transformed antibody levels were compared to determine the impact of systemic lupus erythematosus diagnosis and different treatments on antibody response. Results Systemic lupus erythematosus patients as a group showed lower post-vaccination antibody levels and lower fold increase of antibody levels after vaccination compared to controls ( p = 0.02 and p = 0.009, respectively). Systemic lupus erythematosus patients treated with belimumab in addition to standard of care therapy or with only hydroxychloroquine did not differ compared to controls, whereas the other treatment groups had significantly lower fold increase of post-vaccination antibody levels. Higher age was associated with lower post-vaccination antibody levels among systemic lupus erythematosus patients. Conclusion Belimumab given in addition to traditional disease-modifying anti rheumatic drugs or prednisolone did not further impair antibody response to 13-valent conjugated pneumococcal vaccine.

Systemic lupus erythematosus: still a challenge for physicians.

Systemic lupus erythematosus (SLE) has a complex clinical picture, and a number of defects in the immune system have been described in patients with the disease. Most organs can be involved in SLE, and in addition to the typical major organ manifestations (e.g. from kidneys and the central nervous system), early cardiovascular disease is a major determinant of prognosis. Several important findings during the last decade have increased the understanding of the mechanisms behind the disease characteristics and the underlying autoimmune process. Amongst, these are defects in the handling of apoptotic cells, increased expression of type I interferon-regulated genes and activation of autoreactive B cells, with both the type I interferon system and the B lymphocyte stimulator (BLyS) having key roles. In addition, a large number of genes have been identified that contribute to these abnormalities. It has also become clear that certain SLE risk genes are associated with some organ manifestations, such as STAT4 with nephritis and IRF8 with myocardial infarction. Furthermore, environmental factors that can induce SLE or trigger a disease flare have been identified. As a consequence of this increased knowledge, new treatments for SLE have been developed. The most recently approved drug for SLE is belimumab, which blocks BLyS, and several new therapies and therapeutic strategies are in the pipeline for clinical application.

Deciphering systemic lupus erythematosus-associated serum biomarkers reflecting apoptosis and disease activity.

Systemic lupus erythematosus (SLE) is a severe chronic inflammatory autoimmune connective tissue disease. Despite major efforts, SLE remains a poorly understood disease with unpredictable course, unknown etiology and complex pathogenesis. Apoptosis combined with deficiency in clearing apoptotic cells is an important etiopathogenic event in SLE, which could contribute to the increased load of potential autoantigen(s); however, the lack of disease-specific protein signatures deciphering SLE and the underlying biological processes is striking and represents a key limitation. In this retrospective pilot study, we explored the immune system as a specific sensor for disease, in order to advance our understanding of SLE. To this end, we determined multiplexed serum protein expression profiles of crude SLE serum samples, using antibody microarrays. The aim was to identify differential immunoprofiles, or snapshots of the immune response modulated by the disease, reflecting apoptosis, a key process in the etiology of SLE and disease activity. The results showed that multiplexed panels of SLE-associated serum biomarkers could be decoded, in particular reflecting disease activity, but potentially the apoptosis process as well. While the former biomarkers could display a potential future use for prognosis, the latter biomarkers might help shed further light on the apoptosis process taking place in SLE.