A site-resolved two-dimensional quantum simulator with hundreds of trapped ions.

A large qubit capacity and an individual readout capability are two crucial requirements for large-scale quantum computing and simulation1. As one of the leading physical platforms for quantum information processing, the ion trap has achieved a quantum simulation of tens of ions with site-resolved readout in a one-dimensional Paul trap2-4 and of hundreds of ions with global observables in a two-dimensional (2D) Penning trap5,6. However, integrating these two features into a single system is still very challenging. Here we report the stable trapping of 512 ions in a 2D Wigner crystal and the sideband cooling of their transverse motion. We demonstrate the quantum simulation of long-range quantum Ising models with tunable coupling strengths and patterns, with or without frustration, using 300 ions. Enabled by the site resolution in the single-shot measurement, we observe rich spatial correlation patterns in the quasi-adiabatically prepared ground states, which allows us to verify quantum simulation results by comparing the measured two-spin correlations with the calculated collective phonon modes and with classical simulated annealing. We further probe the quench dynamics of the Ising model in a transverse field to demonstrate quantum sampling tasks. Our work paves the way for simulating classically intractable quantum dynamics and for running noisy intermediate-scale quantum algorithms7,8 using 2D ion trap quantum simulators.

Embedding Quantum Many-Body Scars into Decoherence-Free Subspaces.

Quantum many-body scars are nonthermal excited eigenstates of nonintegrable Hamiltonians, which could support coherent revival dynamics from special initial states when scars form an equally spaced tower in the energy spectrum. For open quantum systems, engineering many-body scarred dynamics by a controlled coupling to the environment remains largely unexplored. Here, we provide a general framework to exactly embed quantum many-body scars into the decoherence-free subspaces of Lindblad master equations. The dissipative scarred dynamics manifest persistent periodic oscillations for generic initial states, and can be practically utilized to prepare scar states with potential quantum metrology applications. We construct the Liouvillian dissipators with the local projectors that annihilate the whole scar towers, and utilize the Hamiltonian part to rotate the undesired states out of the null space of dissipators. We demonstrate our protocol through several typical models hosting many-body scar towers and propose an experimental scheme to observe the dissipative scarred dynamics based on digital quantum simulations and resetting ancilla qubits.

Realizing Synthetic Dimensions and Artificial Magnetic Flux in a Trapped-Ion Quantum Simulator.

Synthetic dimension is a potent tool in quantum simulation of topological phases of matter. Here we propose and demonstrate a scheme to simulate an anisotropic Harper-Hofstadter model with controllable magnetic flux on a two-leg ladder using the spin and motional states of a single trapped ion. We verify the successful simulation of this model by comparing the measured dynamics with theoretical predictions under various coupling strength and magnetic flux, and we observe the chiral motion of wave packets on the ladder as evidence of the topological chiral edge modes. We develop a quench path to adiabatically prepare the ground states for varying magnetic flux and coupling strength, and we measure the chiral current on the ladder for the prepared ground states, which allows us to probe the quantum phase transition between the Meissner phase and the vortex phase. Our work demonstrates the trapped ion as a powerful quantum simulation platform for topological quantum matter.

Probing Complex-Energy Topology via Non-Hermitian Absorption Spectroscopy in a Trapped Ion Simulator.

Non-Hermitian systems generically have complex energies, which may host topological structures, such as links or knots. While there has been great progress in experimentally engineering non-Hermitian models in quantum simulators, it remains a significant challenge to experimentally probe complex energies in these systems, thereby making it difficult to directly diagnose complex-energy topology. Here, we experimentally realize a two-band non-Hermitian model with a single trapped ion whose complex eigenenergies exhibit the unlink, unknot, or Hopf link topological structures. Based on non-Hermitian absorption spectroscopy, we couple one system level to an auxiliary level through a laser beam and then experimentally measure the population of the ion on the auxiliary level after a long period of time. Complex eigenenergies are then extracted, illustrating the unlink, unknot, or Hopf link topological structure. Our work demonstrates that complex energies can be experimentally measured in quantum simulators via non-Hermitian absorption spectroscopy, thereby opening the door for exploring various complex-energy properties in non-Hermitian quantum systems, such as trapped ions, cold atoms, superconducting circuits, or solid-state spin systems.

[Recommendations for diagnosis and treatment of systemic lupus erythematosus].

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease with complicated pathogenesis and diverse clinical manifestations. The current recommendations of the Chinese Rheumatology Association are based on a comprehensive investigation of evidence based medicine, domestic and international guidelines for SLE, and experts' proposals, and aim to provide a more scientific and authoritative reference for the diagnosis and management of SLE. The recommendations focus on four aspects; clinical manifestations, laboratory evaluation, diagnosis and disease assessment, and disease treatment and monitoring. The goal of the recommendations is to standardize the diagnosis and treatment of SLE in China so as to improve the prognosis of SLE patients.

[Exploration of clinical pathway-oriented optimal management diagnosis and treatment model for rare diseases].

This study takes Cushing's syndrome, a rare disease, as a model, and adopts the path of "Plan, Do, Check, Action" (PDCA) to explore new methods to optimize the clinical path, can improve the quality and efficiency of diagnosis and treatment of rare diseases. After sorting out the problems existing in the previous diagnosis and treatment mode, our team optimizes the path in various ways and establishes a standard operation procedure (SOP) for the new path. In the evaluation of the optimized mode, 55 patients with Cushing's syndrome were admitted to the Department of Endocrinology, Peking Union Medical College Hospital, including 19 males and 36 females, aged (41.8±14.4) years (6-68 years). The pathway group (28 cases) and the control group (27 cases) were divided according to whether they were included in the new path management at the time of admission, and the effect of path optimization was assessed in terms of time, efficacy, safety and cost. The results showed that compared with the control group, the pathway group had a shorter time of hospitalization in the Department of Endocrinology and critical tests, such as blood cortisol rhythm, low-dose dexamethasone inhibition test, and bilateral inferior petrosal sinus sampling (all P<0.05). There was no significant differences in the decrease of total cortisol after operation, the incidence of postoperative complications, and hospitalization expenses (all P>0.05). The optimized path improves the medical efficiency while ensuring medical quality, safety and no increase in cost. This study proposes PDCA path optimization for complex diseases and establishes SOP process, which provides experience in management optimization for the patient-centered and clinical path-oriented diagnosis and treatment mode of rare diseases.

Bone microarchitecture impairment in prolactinoma patients assessed by HR-pQCT.

PURPOSE: Prolactinoma may reduce bone mineral density (BMD) and increase fracture risk, but its influence on bone microarchitecture remains to be elucidated. The purpose of this study is to evaluate bone microarchitecture parameters by high-resolution peripheral quantitative computed tomography (HR-pQCT) in prolactinoma patients. METHODS: 31 prolactinoma patients and 62 age- and sex-matched healthy controls in our center were included, and HR-pQCT was used to evaluate their bone microarchitecture at the radius and tibia. Z-scores for bone microarchitecture parameters were calculated based on previously published reference. RESULTS: After adjusting for height and weight, prolactinoma patients had lower trabecular (- 0.011 mm, p = 0.005) and cortical thickness (- 0.116 mm, p = 0.008) and cortical area (- 6.0 mm2, p = 0.013) at radius, as well as lower trabecular (- 0.014 mm, p = 0.008) and cortical (- 0.122 mm, p = 0.022) thickness at tibia compared with the controls. Patients with higher prolactin level had more severe bone microarchitecture impairments. After adjusting for prolactin level and age, male patients had lower trabecular volumetric BMD (vBMD), trabecular number, trabecular thickness, and cortical porosity at radius, as well as lower trabecular vBMD, trabecular bone volume fraction, trabecular number, and cortical area, and higher trabecular separation at tibia compared with female patients. Z-score for radius vBMD was correlated with Z-score for areal BMD (aBMD) at lumbar and femoral neck, while Z-score for tibia vBMD was correlated with Z-score for lumbar aBMD, and some patients with vBMD Z-score below - 2.0 had aBMD Z-score within normal range. CONCLUSION: Peripheral bone microarchitecture was impaired in prolactinoma patients, especially in patients with higher prolactin level. We compared the bone microarchitecture of prolactinoma patients and healthy controls by high-resolution peripheral quantitative computed tomography (HR-pQCT), and found that many bone microarchitecture parameters were impaired among prolactinoma patients. Such impairment was more prominent among patients with higher prolactin level.

Presence and Absence of Barren Plateaus in Tensor-Network Based Machine Learning.

Tensor networks are efficient representations of high-dimensional tensors with widespread applications in quantum many-body physics. Recently, they have been adapted to the field of machine learning, giving rise to an emergent research frontier that has attracted considerable attention. Here, we study the trainability of tensor-network based machine learning models by exploring the landscapes of different loss functions, with a focus on the matrix product states (also called tensor trains) architecture. In particular, we rigorously prove that barren plateaus (i.e., exponentially vanishing gradients) prevail in the training process of the machine learning algorithms with global loss functions. Whereas, for local loss functions the gradients with respect to variational parameters near the local observables do not vanish as the system size increases. Therefore, the barren plateaus are absent in this case and the corresponding models could be efficiently trainable. Our results reveal a crucial aspect of tensor-network based machine learning in a rigorous fashion, which provide a valuable guide for both practical applications and theoretical studies in the future.

Observation of Non-Markovian Spin Dynamics in a Jaynes-Cummings-Hubbard Model Using a Trapped-Ion Quantum Simulator.

The Jaynes-Cummings-Hubbard (JCH) model is a fundamental many-body model for light-matter interaction. As a leading platform for quantum simulation, the trapped ion system has realized the JCH model for two to three ions. Here, we report the quantum simulation of the JCH model using up to 32 ions. We verify the simulation results even for large ion numbers by engineering low excitations and thus low effective dimensions; then we extend to 32 excitations for an effective dimension of 2^{77}, which is difficult for classical computers. By regarding the phonon modes as baths, we explore Markovian or non-Markovian spin dynamics in different parameter regimes of the JCH model, similar to quantum emitters in a structured photonic environment. We further examine the dependence of the non-Markovian dynamics on the effective Hilbert space dimension. Our Letter demonstrates the trapped ion system as a powerful quantum simulator for many-body physics and open quantum systems.

Experimental Realization of the Rabi-Hubbard Model with Trapped Ions.

Quantum simulation provides important tools in studying strongly correlated many-body systems with controllable parameters. As a hybrid of two fundamental models in quantum optics and in condensed matter physics, the Rabi-Hubbard model demonstrates rich physics through the competition between local spin-boson interactions and long-range boson hopping. Here, we report an experimental realization of the Rabi-Hubbard model using up to 16 trapped ions and present a controlled study of its equilibrium properties and quantum dynamics. We observe the ground-state quantum phase transition by slowly quenching the coupling strength, and measure the quantum dynamical evolution in various parameter regimes. With the magnetization and the spin-spin correlation as probes, we verify the prediction of the model Hamiltonian by comparing theoretical results in small system sizes with experimental observations. For larger-size systems of 16 ions and 16 phonon modes, the effective Hilbert space dimension exceeds 2^{57}, whose dynamics is intractable for classical supercomputers.

Quantum Simulation of the Two-Dimensional Weyl Equation in a Magnetic Field.

Quantum simulation of 1D relativistic quantum mechanics has been achieved in well-controlled systems like trapped ions, but properties like spin dynamics and response to external magnetic fields that appear only in higher dimensions remain unexplored. Here we simulate the dynamics of a 2D Weyl particle. We show the linear dispersion relation of the free particle and the discrete Landau levels in a magnetic field, and we explicitly measure the spatial and spin dynamics from which the conservation of helicity and properties of antiparticles can be verified. Our work extends the application of an ion trap quantum simulator in particle physics with the additional spatial and spin degrees of freedom.

A study on serum pro-neurotensin (PNT), furin, and zinc alpha-2-glycoprotein (ZAG) levels in patients with acromegaly.

PURPOSE: Acromegaly caused by growth hormone cell adenoma is commonly associated with abnormal glucolipid metabolism, which may result from changes in adipocytokine secretion. This study aims to investigate serum adipokine levels, including pro-neurotensin (PNT), furin, and zinc alpha-2-glycoprotein (ZAG), in acromegalic patients and the correlation between the levels of these three adipokines and GH levels and glucolipid metabolism indices. METHODS: Sixty-eight acromegalic patients and 121 controls were included, and their clinical data were recorded from electronic medical record system. Serum PNT, furin and ZAG levels were measured by ELISA. RESULTS: Serum PNT levels in acromegalic patients were significantly higher than controls (66.60 ± 12.36 vs. 46.68 ± 20.54 pg/ml, P < 0.001), and acromegaly was an independent influencing factor of PNT levels (P < 0.001). Moreover, subjects with the highest tertile of PNT levels had a close correlation with acromegaly (OR = 22.200, 95% CI 7.156 ~ 68.875, P < 0.001), even in Model 1 adjusted for gender and age and Model 2 adjusted for gender, age and BMI. Additionally, serum PNT levels were positively correlated with BMI (r = 0.220, P = 0.002) and triglycerides (TGs, r = 0.295, P < 0.001), and TGs were an independent influencing factor of serum PNT levels in acromegalic subjects (P < 0.001). Furthermore, serum PNT levels in obese acromegalic patients were significantly higher than those with normal BMI (P < 0.05). However, serum furin levels were lower in acromegalic patients than controls (0.184 ± 0.036 vs. 0.204 ± 0.061 ng/ml, P < 0.001). CONCLUSION: This study is the first to demonstrate that acromegalic patients have increased serum PNT levels. Moreover, serum PNT plays a potential role in abnormal lipid metabolism of acromegalic patients.

[The correlation between reflux esophagitis and Helicobacter pylori infection based on natural population].

Objective: Reflux esophagitis (RE) may be negatively correlated with Helicobacter pylori (H. pylori) infection, but the conclusion and relevant mechanism is still controversial. This study proposed to explore the correlation between RE and H. pylori infection based on natural population. Methods: From July 2013 to December 2014, 3 940 residents aged 40-69 years were recruited in Linqu County of Shandong Province and Hua County of Henan Province by the whole sampling method. All the subjects underwent gastroscopy, and gastric mucosa biopsy specimens were collected for pathological diagnosis and Warthin-Starry (WS) staining to identify H. pylori infection. Venous blood samples of some subjects were collected for H. pylori immunoglobulin G (H. pylori-IgG) detection. Also, demographic and sociological data were collected. Chi-square test and logistic regression were used to analyze the correlation between RE and H. pylori infection. Results: A total of 359 cases of RE were detected. Excluding RE and other upper gastrointestinal organic diseases, 3 382 cases were considered as controls. Chi-square test showed that WS staining positive rate in RE group was significantly lower than that in control group (P=0.023), but there was no significant difference in the positive rate of H. pylori-IgG between the two groups (P=0.281). There were significant differences between RE group and control group in gender composition, age, body mass index (BMI), smoking, alcohol consumption, education level and mucosal active inflammation. Multivariate regression analysis showed that RE was negatively correlated with gastric mucosa active inflammation [OR=0.754 (95%CI 0.600-0.949), P=0.016], and positively correlated with male [OR=4.231 (95%CI 3.263-5.486), P<0.001], age ≥60 years, BMI≥24 kg/m2 [OR=1.540 (95%CI 1.220-1.945), P<0.001]. Compared to those aged 40-49 years and 50-59 years, the odds ratio (OR) of RE in these aged ≥60 years were 1.566 (95%CI 1.144-2.143, P=0.005) and 1.405 (95%CI 1.093-1.805, P=0.008). Conclusion: RE is more closely related to H. pylori present infection. Multivariate analysis showed that RE is negatively correlated with active inflammation of gastric mucosa caused by H. pylori infection, and positively correlated with male, overweight and aged ≥60 years.

[Analysing the occupational status of physicians to improve female physicians career development].

The rights and health problems of physicians have been wildly concerned, which affects the career satisfaction and career achievement of physicians. The occupational environment of physicians in the nation and abroad, as well as the differences in work caused by gender was described. On behalf of gastroenterology, by analysing of pressures and challenges faced by physicians and their occupational status in different genders to understand their work feelings can implement targeted improvement measures in the future medical environment, and encouraging female medical professionals play a better role in healthcare.

[Time trends of H. pylori infection and related drug use in patients with peptic ulcer bleeding in a hospital in Beijing from 2010 to 2019].

Objective: To explore the time trends of H. pylori infection and related drug use in patients with peptic ulcer bleeding (PUB) in recent ten years. Methods: PUB patients in Peking University Third Hospital from 2010 to 2019 were included. Time trends of H. pylori infection, related drugs (non-steroidal anti-inflammatory drugs, aspirin, antiplatelet drugs, anticoagulant drugs, glucocorticoids) use and non-H. pylori-non-drug ulcer in PUB patients were analyzed. Results: A total of 1 140 PUB patients were included from 2010 to 2019 (including 925 males and 215 females). The age M(Q1,Q3)was 53.5 (33.0, 66.0) years, with 833 patients <65 years old. The positive rates of H. pylori were 79.3%, 75.7%, 73.1%, 71.6%, 77.0%, 70.4%, 69.7%, 63.1%, 51.4%, 50.9%, respectively, showing a decreasing trend (χ²=32.386, P<0.001), and the decreasing trends were significant in different ulcer location, age and gender subgroups(all P<0.05). The proportions of PUB patients using at least one of the above drugs were 23.1%, 28.6%, 34.0%, 39.5%, 33.8%, 35.9%, 28.7%, 39.8%, 40.9%, 41.8%, respectively, showing an increasing trend (χ²=6.857, P=0.009), and the proportions of patients with antiplatelet drugs and anticoagulant drugs history showed increasing trends. The proportions of non-H. pylori-non-drug patients were 12.3%, 22.1%, 14.6%, 13.2%, 7.7%, 13.0%, 16.9%, 18.7%, 22.6% and 20.9%, respectively, showing an increasing trend (χ²=4.808, P=0.028). Accordingly, the proportions of elderly (≥65 years old) patients (χ²=4.608, P=0.032) and large ulcer (≥2 cm) patients (χ²=8.173, P=0.004) showed increasing trends. Conclusion: In the last decade, the positive rate of H. pylori in PUB patients showed a decreasing trend, while the proportions of patients with antiplatelet drugs and anticoagulant drugs history and the proportion of non-H. pylori-non-drug patients showed increasing trends.

[The influence of gastroenterologists' intrinsic motivation on work burnout and the mediating effects of work stress].

Objective: To analyze the influence of intrinsic motivation on work burnout and the mediating effects of work stress. Methods: In 2020, questionnaire survey was conducted in 1 655 gastroenterologists working in 28 provinces of China. Mediation model was used to analyze the mediating effects of work stress in the relationship between intrinsic motivation and burnout. Resutls 1655 valid questionnaires were collected, including 1 132 women and 523 men, with an average age of 39.26. Intrinsic motivation was related to reduced level of burnout, including emotional exhaustion, dehumanization and low sense of accomplishment (ß=-2.06, -1, 77 and-4.20;P<0.001). Job stress partially mediated the negative correlation between intrinsic motivation and job burnout in three dimensions, accounting for 40%, 15% and 5% (ß=-1.58, -0.36 and-0.21;P<0.05), respectively. In female physicians, the intrinsic motivation was more directly related to the reduction of burnout, especially in the dimension"emotional exhaustion"(direct effect accounting for 62% in female gastroenterologists and 46% in male). Conclusions: Enhancing the intrinsic motivation of gastroenterologists can directly reduce burnout and indirectly reduce burnout by alleviating work stress. In the same work environment, female physicians' intrinsic motivation had a greater and more direct effect on reducing burnout.

[Research progress of circumferential tracheal reconstruction via tissue-engineered trachea].

Tissue engineering, as a new technology, provides a new avenue for the reconstruction of circumferential tracheal defects, which has always been a tremendous challenge for surgeons around the world. Recently, technologies such as decellularization, 3-dimensional printing, electrospinning and cell sheet have significantly enhanced the chondrification. Implantation of epithelial cells or transplantation of epithelial cell sheets also has accelerated the process of epithelialization. And pedicle muscle flap proved to be a reliable strategy for vascularization of tissue-engineered trachea. But it is still a huge challenge to achieve circumferential tracheal functional reconstruction. The key difficulty lies in how to simultaneously realize the functional regeneration of cartilage, blood vessels and epithelial tissues of tissue-engineered trachea. Therefore, how to integrate the above schemes and finally realize segmental tracheal reconstruction needs further research. This article reviews the research progress of repairing circumferential tracheal defects based on tissue engineering technology.

Observation of Non-Hermitian Topology with Nonunitary Dynamics of Solid-State Spins.

Non-Hermitian topological phases exhibit a number of exotic features that have no Hermitian counterparts, including the skin effect and breakdown of the conventional bulk-boundary correspondence. Here, we implement the non-Hermitian Su-Schrieffer-Heeger Hamiltonian, which is a prototypical model for studying non-Hermitian topological phases, with a solid-state quantum simulator consisting of an electron spin and a ^{13}C nuclear spin in a nitrogen-vacancy center in a diamond. By employing a dilation method, we realize the desired nonunitary dynamics for the electron spin and map out its spin texture in the momentum space, from which the corresponding topological invariant can be obtained directly. From the measured spin textures with varying parameters, we observe both integer and fractional winding numbers. The non-Hermitian topological phase with fractional winding number cannot be continuously deformed to any Hermitian topological phase and is intrinsic to non-Hermitian systems. Our result paves the way for further exploiting and understanding the intriguing properties of non-Hermitian topological phases with solid-state spins or other quantum simulation platforms.

Impact of Spectators on a Two-Qubit Gate in a Tunable Coupling Superconducting Circuit.

Cross-resonance (CR) gates have emerged as a promising scheme for fault-tolerant quantum computation with fixed-frequency qubits. We experimentally implement an entangling CR gate by using a microwave-only control in a tunable coupling superconducting circuit, where the tunable coupler provides extra degrees of freedom to verify optimal conditions for constructing a CR gate. By developing a three-qubit Hamiltonian tomography protocol, we systematically investigate the dependency of gate fidelities on spurious qubit interactions and present the first experimental approach to the evaluation of the perturbation impact arising from spectator qubits. Our results reveal that the spectator qubits lead to reductions in CR gate fidelity dependent on ZZ interactions and particular frequency detunings between spectator and gate qubits. The target spectator demonstrates a more serious impact than the control spectator under a standard echo pulse scheme, whereas the degradation of gate fidelity is observed up to 22.5% as both the spectators are present with a modest ZZ coupling to the computational qubits. Our experiments uncover an optimal CR operation regime, and the method we develop here can readily be applied to improving other kinds of two-qubit gates in large-scale quantum circuits.

Experimental Realization of Multi-ion Sympathetic Cooling on a Trapped Ion Crystal.

Trapped ions are one of the leading platforms in quantum information science. For quantum computing with large circuit depth and quantum simulation with long evolution time, it is of crucial importance to cool large ion crystals at runtime without affecting the internal states of the computational qubits, thus the necessity of sympathetic cooling. Here, we report multi-ion sympathetic cooling on a long ion chain using a narrow cooling beam focused on two adjacent ions, and optimize the choice of the cooling ions according to the collective oscillation modes of the chain. We show that, by cooling a small fraction of ions, cooling effects close to the global Doppler cooling limit can be achieved. This experiment therefore demonstrates an important enabling step for quantum information processing with large ion crystals.