Imaging the Meissner effect in hydride superconductors using quantum sensors.

By directly altering microscopic interactions, pressure provides a powerful tuning knob for the exploration of condensed phases and geophysical phenomena1. The megabar regime represents an interesting frontier, in which recent discoveries include high-temperature superconductors, as well as structural and valence phase transitions2-6. However, at such high pressures, many conventional measurement techniques fail. Here we demonstrate the ability to perform local magnetometry inside a diamond anvil cell with sub-micron spatial resolution at megabar pressures. Our approach uses a shallow layer of nitrogen-vacancy colour centres implanted directly within the anvil7-9; crucially, we choose a crystal cut compatible with the intrinsic symmetries of the nitrogen-vacancy centre to enable functionality at megabar pressures. We apply our technique to characterize a recently discovered hydride superconductor, CeH9 (ref. 10). By performing simultaneous magnetometry and electrical transport measurements, we observe the dual signatures of superconductivity: diamagnetism characteristic of the Meissner effect and a sharp drop of the resistance to near zero. By locally mapping both the diamagnetic response and flux trapping, we directly image the geometry of superconducting regions, showing marked inhomogeneities at the micron scale. Our work brings quantum sensing to the megabar frontier and enables the closed-loop optimization of superhydride materials synthesis.

Probing many-body dynamics in a two-dimensional dipolar spin ensemble.

The most direct approach for characterizing the quantum dynamics of a strongly interacting system is to measure the time evolution of its full many-body state. Despite the conceptual simplicity of this approach, it quickly becomes intractable as the system size grows. An alternate approach is to think of the many-body dynamics as generating noise, which can be measured by the decoherence of a probe qubit. Here we investigate what the decoherence dynamics of such a probe tells us about the many-body system. In particular, we utilize optically addressable probe spins to experimentally characterize both static and dynamical properties of strongly interacting magnetic dipoles. Our experimental platform consists of two types of spin defects in nitrogen delta-doped diamond: nitrogen-vacancy colour centres, which we use as probe spins, and a many-body ensemble of substitutional nitrogen impurities. We demonstrate that the many-body system's dimensionality, dynamics and disorder are naturally encoded in the probe spins' decoherence profile. Furthermore, we obtain direct control over the spectral properties of the many-body system, with potential applications in quantum sensing and simulation.

U-shaped association between dietary thiamine intake and new-onset diabetes: a nationwide cohort study.

BACKGROUND: The association between dietary thiamine intake and the risk of diabetes remains unknown. AIM: We aimed to evaluate the relation of dietary thiamine intake with new-onset diabetes and examine possible effect modifiers. DESIGN: Prospective cohort study. METHODS: A total of 16 272 participants who were free of diabetes at baseline were enrolled from China Health and Nutrition Survey (CHNS). Dietary nutrients intake information was collected by 3-day dietary recalls in addition to using a 3-day food-weighed method to assess cooking oil and condiment consumption. New-onset diabetes was defined as a fasting blood glucose ≥7.0 mmol/l or a glycated haemoglobin (HbA1c) ≥6.5% (48 mmol/mol) or diagnosed by a physician during the follow-up. RESULTS: During a median follow-up duration of 9.0 years, new-onset diabetes occurred in 1101 participants. Overall, the association between dietary thiamine intake and new-onset diabetes followed a U-shape (P for non-linearity <0.001). Consistently, when thiamine intake was assessed as quartiles, compared with those in the 2-3 quartiles (0.75 to 1.10 mg/day), the significantly higher risks of new-onset diabetes were found in participants in the first quartile [adjusted hazard ratio (HR), 1.33; 95% confidence interval (CI): 1.10, 1.61] and the fourth quartile (adjusted HR, 1.39; 95% CI: 1.17, 1.67). Similar results were found when further adjusting for the intake of other major nutrients or food groups; or using the propensity score weighting to control the imbalance of covariates. CONCLUSION: Our results suggested that there was a U-shape association between dietary thiamine intake and new-onset diabetes in general Chinese adults, with a minimal risk at 0.75-1.10 mg/day.

Emergent hydrodynamics in a strongly interacting dipolar spin ensemble.

Conventional wisdom holds that macroscopic classical phenomena naturally emerge from microscopic quantum laws1-7. However, despite this mantra, building direct connections between these two descriptions has remained an enduring scientific challenge. In particular, it is difficult to quantitatively predict the emergent 'classical' properties of a system (for example, diffusivity, viscosity and compressibility) from a generic microscopic quantum Hamiltonian7-14. Here we introduce a hybrid solid-state spin platform, where the underlying disordered, dipolar quantum Hamiltonian gives rise to the emergence of unconventional spin diffusion at nanometre length scales. In particular, the combination of positional disorder and on-site random fields leads to diffusive dynamics that are Fickian yet non-Gaussian15-20. Finally, by tuning the underlying parameters within the spin Hamiltonian via a combination of static and driven fields, we demonstrate direct control over the emergent spin diffusion coefficient. Our work enables the investigation of hydrodynamics in many-body quantum spin systems.

[A cohort study on the association between resting heart rate and the risk of new-onset heart failure].

Objective: To prospectively explore the relationship between resting heart rate (RHR) and risk of new-onset heart failure. Methods: It was a prospective cohort study. People who attended the physical examination of Kailuan Group Company in 2006 and with complete electrocardiography (ECG) recordings were eligible for this study. A total of 88 879 participants aged 18 years old or more who were free of arrhythmia, a prior history of heart failure and were not treated with ß-blocker were included. Participants were divided into 5 groups according to the quintiles of RHR at baseline (Q(1) group, 40-60 beats/minutes (n=18 168) ; Q(2) group, 67-70 beats/minutes (n=18 970) ; Q(3) group, 71-74 beats/minutes (n=13 583) ; Q(4) group, 75-80 beats/minutes (n=22 739) ; and Q(5) group,>80 beats/minutes (n=15 419) ) .The general clinical data and laboratory test results were collected. The outcome was the first occurrence of heart failure at the end of follow-up (December 31, 2016) .We used Cox regression model to examine the association between RHR and the risk of new-onset heart failure. Hazard ratio (HR) with 95% confidence intervals (CI) were calculated using Cox regression modeling. Results: Among the included patients 68 411 participants were male, mean age was (51.0±12.3) years old, and RHR was (74±10) beats/minutes. Statistically significant differences among the RHR quintiles were found for the following variables: age, gender, systolic blood pressure, diastolic blood pressure, triglycerides, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, fasting blood glucose, body mass index, the level of high-sensitivity C-reactive protein, education status, physical activity, smoking status, drinking status, history of diabetes, history of hypertension and history of use antihypertensive drugs (all P<0.01) . Higher RHR was linked with higher prevalence of diabetes, hypertension history, and higher systolic blood pressure, diastolic blood pressure and FBG levels (all P<0.01). After a mean follow-up of 9.5 years, the incidence of new-onset heart failure in Q(1), Q(2), Q(3), Q(4) and Q(5) groups was 1.60%(290/18 168), 1.36%(258/18 970), 1.80%(245/13 583), 1.76%(400/22 739) and 2.35%(362/15 419),respectively (P<0.01) . The person-year incidence of heart failure in Q(1), Q(2), Q(3), Q(4) and Q(5) groups was 1.7, 1.5, 1.9, 1.9 and 2.6 per 1 000 person-years respectively. Compared with the Q(2) group, multivariate analysis with adjustment for major traditional cardiovascular risk factors showed that HRs of Q(3),Q(4),and Q(5) group were 1.23 (95%CI 1.03-1.48, P<0.05) , 1.19 (95%CI 1.01-1.41, P<0.05) , 1.39 (95%CI 1.18-1.65, P<0.01) , respectively. In the absence of hypertension, diabetes, smoking and acute myocardial infarction, the Cox regression model showed that compared with Q(2) group, the HR of new-onset heart failure in Q(5) group was 1.58 (95%CI 1.02-2.45, P<0.05) . Conclusion: Increased RHR is associated with increased risk of new-onset heart failure in this cohort.

Imaging stress and magnetism at high pressures using a nanoscale quantum sensor.

Pressure alters the physical, chemical, and electronic properties of matter. The diamond anvil cell enables tabletop experiments to investigate a diverse landscape of high-pressure phenomena. Here, we introduce and use a nanoscale sensing platform that integrates nitrogen-vacancy (NV) color centers directly into the culet of diamond anvils. We demonstrate the versatility of this platform by performing diffraction-limited imaging of both stress fields and magnetism as a function of pressure and temperature. We quantify all normal and shear stress components and demonstrate vector magnetic field imaging, enabling measurement of the pressure-driven [Formula: see text] phase transition in iron and the complex pressure-temperature phase diagram of gadolinium. A complementary NV-sensing modality using noise spectroscopy enables the characterization of phase transitions even in the absence of static magnetic signatures.

Imaging the Local Charge Environment of Nitrogen-Vacancy Centers in Diamond.

Characterizing the local internal environment surrounding solid-state spin defects is crucial to harnessing them as nanoscale sensors of external fields. This is especially germane to the case of defect ensembles which can exhibit a complex interplay between interactions, internal fields, and lattice strain. Working with the nitrogen-vacancy (NV) center in diamond, we demonstrate that local electric fields dominate the magnetic resonance behavior of NV ensembles at a low magnetic field. We introduce a simple microscopic model that quantitatively captures the observed spectra for samples with NV concentrations spanning more than two orders of magnitude. Motivated by this understanding, we propose and implement a novel method for the nanoscale localization of individual charges within the diamond lattice; our approach relies upon the fact that the charge induces a NV dark state which depends on the electric field orientation.

Effect of increased UV-B radiation on carotenoid accumulation and total antioxidant capacity in tobacco (Nicotiana tabacum L.) leaves.

Carotenoids are important components of plant antioxidant systems, which protect photosystems from photooxidative destruction during ultraviolet-B (UV-B) exposure. The influence of carotenoids on total antioxidant capacity (TAC) of plants has rarely been studied. In this study, tobacco (Nicotiana tabacum L., 'K326') seedlings exposed to UV-B radiation were used in order to evaluate the effects of ambient levels of UV-B radiation on carotenoid accumulation. The aim was to investigate whether carotenoids could enhance TAC as a means of UV protection. Our results showed that leaf carotenoid content in the low UV-B exposure (+9.75 µW/cm2) plants was approximately 8% higher than that observed in control plants at 2-8 days of exposure. At high UV-B exposure (+20.76 µW/cm2), the carotenoid content increased rapidly after 1 day's exposure (10.41% higher than the control), followed by a return to the content as in control plants. Furthermore, carotenoid content positively correlated with TAC (P = 0.024). These results suggest that carotenoids have antioxidant properties and play an important role in the antioxidant system. UV-B exposure increased the carotenoid synthesis capability of plants. The plants could deplete the carotenoids to scavenge excess ROS at high UV-B radiation levels, which protects the tobacco plant from oxidative damage caused by UV-B stress.

Quantum teleportation from light beams to vibrational states of a macroscopic diamond.

With the recent development of optomechanics, the vibration in solids, involving collective motion of trillions of atoms, gradually enters into the realm of quantum control. Here, building on the recent remarkable progress in optical control of motional states of diamonds, we report an experimental demonstration of quantum teleportation from light beams to vibrational states of a macroscopic diamond under ambient conditions. Through quantum process tomography, we demonstrate average teleportation fidelity (90.6±1.0)%, clearly exceeding the classical limit of 2/3. The experiment pushes the target of quantum teleportation to the biggest object so far, with interesting implications for optomechanical quantum control and quantum information science.

Memory-built-in quantum cloning in a hybrid solid-state spin register.

As a way to circumvent the quantum no-cloning theorem, approximate quantum cloning protocols have received wide attention with remarkable applications. Copying of quantum states to memory qubits provides an important strategy for eavesdropping in quantum cryptography. We report an experiment that realizes cloning of quantum states from an electron spin to a nuclear spin in a hybrid solid-state spin register with near-optimal fidelity. The nuclear spin provides an ideal memory qubit at room temperature, which stores the cloned quantum states for a millisecond under ambient conditions, exceeding the lifetime of the original quantum state carried by the electron spin by orders of magnitude. The realization of a cloning machine with built-in quantum memory provides a key step for application of quantum cloning in quantum information science.

Experimental demonstration of a quantum router.

The router is a key element for a network. We describe a scheme to realize genuine quantum routing of single-photon pulses based on cascading of conditional quantum gates in a Mach-Zehnder interferometer and report a proof-of-principle experiment for its demonstration using linear optics quantum gates. The polarization of the control photon routes in a coherent way the path of the signal photon while preserving the qubit state of the signal photon represented by its polarization. We demonstrate quantum nature of this router by showing entanglement generated between the initially unentangled control and signal photons, and confirm that the qubit state of the signal photon is well preserved by the router through quantum process tomography.

Experimental realization of universal geometric quantum gates with solid-state spins.

Experimental realization of a universal set of quantum logic gates is the central requirement for the implementation of a quantum computer. In an 'all-geometric' approach to quantum computation, the quantum gates are implemented using Berry phases and their non-Abelian extensions, holonomies, from geometric transformation of quantum states in the Hilbert space. Apart from its fundamental interest and rich mathematical structure, the geometric approach has some built-in noise-resilience features. On the experimental side, geometric phases and holonomies have been observed in thermal ensembles of liquid molecules using nuclear magnetic resonance; however, such systems are known to be non-scalable for the purposes of quantum computing. There are proposals to implement geometric quantum computation in scalable experimental platforms such as trapped ions, superconducting quantum bits and quantum dots, and a recent experiment has realized geometric single-bit gates in a superconducting system. Here we report the experimental realization of a universal set of geometric quantum gates using the solid-state spins of diamond nitrogen-vacancy centres. These diamond defects provide a scalable experimental platform with the potential for room-temperature quantum computing, which has attracted strong interest in recent years. Our experiment shows that all-geometric and potentially robust quantum computation can be realized with solid-state spin quantum bits, making use of recent advances in the coherent control of this system.

Experimental distillation of quantum nonlocality.

We report the first experimental demonstration of distillation of quantum nonlocality, confirming the recent theoretical protocol [Phys. Rev. Lett. 102, 120401 (2009)]. Quantum nonlocality is described by a correlation box with binary inputs and outputs, and the nonlocal boxes are realized through appropriate measurements on polarization entangled photon pairs. We demonstrate that nonlocality is amplified by connecting two nonlocal boxes into a composite one through local operations and four-photon measurements.

State-independent experimental test of quantum contextuality in an indivisible system.

We report the first state-independent experimental test of quantum contextuality on a single photonic qutrit (three-dimensional system), based on a recent theoretical proposal [Phys. Rev. Lett. 108, 030402 (2012)]. Our experiment spotlights quantum contextuality in its most basic form, in a way that is independent of either the state or the tensor product structure of the system.

Post-earthquake outbreak of insecticide-associated conjunctivitis in a primary school of Lixian district, China: An epidemiological investigation.

OBJECTIVES: To describe the time course and characteristics of an insecticide-associated incident and highlight potential risks from similar outbreaks that may occur in other areas to enhance the preparedness of emergency physicians and other healthcare providers to deal with the sequelae of these events. STUDY DESIGN: Outbreak investigation METHODS: From 5 to 8 August 2008, an outbreak investigation was carried out among the affected primary school located in the refugee camp area of Lixian district, Sichuan, China. Affected pupils, parents, teachers and doctors working in the local medical stations were visited. Clinical checking, clinical treatment, epidemiological investigation and environmental investigation were undertaken. RESULTS: In total, 138 individuals were diagnosed with acute conjunctivitis, characterized by inflammation of the conjunctiva and intense ocular symptoms such as redness, itching and mucus discharge. According to the results, all risk factors (i.e. drinking water, indoor air and the materials used in camp classrooms) were excluded except insecticide exposure. The characteristics of symptoms, distribution of cases and records of irregular insecticide spraying support the assumption that the conjunctivitis outbreak was associated with synthetic pyrethroid alphacypermethrin exposure. CONCLUSION: The results suggest that non-standard operating procedures in pest control could lead to disease incidents. Medical rescue teams should receive training and education in preventive techniques.