Generation of genuine entanglement up to 51 superconducting qubits.

Scalable generation of genuine multipartite entanglement with an increasing number of qubits is important for both fundamental interest and practical use in quantum-information technologies1,2. On the one hand, multipartite entanglement shows a strong contradiction between the prediction of quantum mechanics and local realization and can be used for the study of quantum-to-classical transition3,4. On the other hand, realizing large-scale entanglement is a benchmark for the quality and controllability of the quantum system and is essential for realizing universal quantum computing5-8. However, scalable generation of genuine multipartite entanglement on a state-of-the-art quantum device can be challenging, requiring accurate quantum gates and efficient verification protocols. Here we show a scalable approach for preparing and verifying intermediate-scale genuine entanglement on a 66-qubit superconducting quantum processor. We used high-fidelity parallel quantum gates and optimized the fidelitites of parallel single- and two-qubit gates to be 99.91% and 99.05%, respectively. With efficient randomized fidelity estimation9, we realized 51-qubit one-dimensional and 30-qubit two-dimensional cluster states and achieved fidelities of 0.637 ± 0.030 and 0.671 ± 0.006, respectively. On the basis of high-fidelity cluster states, we further show a proof-of-principle realization of measurement-based variational quantum eigensolver10 for perturbed planar codes. Our work provides a feasible approach for preparing and verifying entanglement with a few hundred qubits, enabling medium-scale quantum computing with superconducting quantum systems.

Experimental Simulation of Larger Quantum Circuits with Fewer Superconducting Qubits.

Although near-term quantum computing devices are still limited by the quantity and quality of qubits in the so-called NISQ era, quantum computational advantage has been experimentally demonstrated. Moreover, hybrid architectures of quantum and classical computing have become the main paradigm for exhibiting NISQ applications, where low-depth quantum circuits are repeatedly applied. In order to further scale up the problem size solvable by the NISQ devices, it is also possible to reduce the number of physical qubits by "cutting" the quantum circuit into different pieces. In this work, we experimentally demonstrated a circuit-cutting method for simulating quantum circuits involving many logical qubits, using only a few physical superconducting qubits. By exploiting the symmetry of linear-cluster states, we can estimate the effectiveness of circuit-cutting for simulating up to 33-qubit linear-cluster states, using at most 4 physical qubits for each subcircuit. Specifically, for the 12-qubit linear-cluster state, we found that the experimental fidelity bound can reach as much as 0.734, which is about 19% higher than a direct implementation on the same 12-qubit superconducting processor. Our results indicate that circuit-cutting represents a feasible approach of simulating quantum circuits using much fewer qubits, while achieving a much higher circuit fidelity.

Logical Magic State Preparation with Fidelity beyond the Distillation Threshold on a Superconducting Quantum Processor.

Fault-tolerant quantum computing based on surface code has emerged as an attractive candidate for practical large-scale quantum computers to achieve robust noise resistance. To achieve universality, magic states preparation is a commonly approach for introducing non-Clifford gates. Here, we present a hardware-efficient and scalable protocol for arbitrary logical state preparation for the rotated surface code, and further experimentally implement it on the Zuchongzhi 2.1 superconducting quantum processor. An average of 0.8983±0.0002 logical fidelity at different logical states with distance three is achieved, taking into account both state preparation and measurement errors. In particular, the logical magic states |A^{π/4}⟩_{L}, |H⟩_{L}, and |T⟩_{L} are prepared nondestructively with logical fidelities of 0.8771±0.0009, 0.9090±0.0009, and 0.8890±0.0010, respectively, which are higher than the state distillation protocol threshold, 0.859 (for H-type magic state) and 0.827 (for T-type magic state). Our work provides a viable and efficient avenue for generating high-fidelity raw logical magic states, which is essential for realizing non-Clifford logical gates in the surface code.

Ruling Out Real-Valued Standard Formalism of Quantum Theory.

Standard quantum theory was formulated with complex-valued Schrödinger equations, wave functions, operators, and Hilbert spaces. Previous work attempted to simulate quantum systems using only real numbers by exploiting an enlarged Hilbert space. A fundamental question arises: are the complex numbers really necessary in the standard formalism of quantum theory? To answer this question, a quantum game has been developed to distinguish standard quantum theory from its real-number analog, by revealing a contradiction between a high-fidelity multiqubit quantum experiment and players using only real-number quantum theory. Here, using superconducting qubits, we faithfully realize the quantum game based on deterministic entanglement swapping with a state-of-the-art fidelity of 0.952. Our experimental results violate the real-number bound of 7.66 by 43 standard deviations. Our results disprove the real-number formulation and establish the indispensable role of complex numbers in the standard quantum theory.

Realization of an Error-Correcting Surface Code with Superconducting Qubits.

Quantum error correction is a critical technique for transitioning from noisy intermediate-scale quantum devices to fully fledged quantum computers. The surface code, which has a high threshold error rate, is the leading quantum error correction code for two-dimensional grid architecture. So far, the repeated error correction capability of the surface code has not been realized experimentally. Here, we experimentally implement an error-correcting surface code, the distance-three surface code which consists of 17 qubits, on the Zuchongzhi 2.1 superconducting quantum processor. By executing several consecutive error correction cycles, the logical error can be significantly reduced after applying corrections, achieving the repeated error correction of surface code for the first time. This experiment represents a fully functional instance of an error-correcting surface code, providing a key step on the path towards scalable fault-tolerant quantum computing.

The Autocatalytic Cleavage Domain Is Not Required for the Activity of ScpC, a Virulence Protease from Streptococcus pyogenes: A Structural Insight.

Group A Streptococcus (GAS, or Streptococcus pyogenes) is a leading human bacterial pathogen with diverse clinical manifestations, ranging from mild to life-threatening and to severe immune sequela. These diseases, combined, account for more than half a million deaths per year, globally. To accomplish its vast pathogenic potential, GAS expresses a multitude of virulent proteins, including the pivotal virulence factor ScpC. ScpC is a narrow-range surface-exposed subtilisin-like serine protease that cleaves the last 14 C-terminal amino acids of interleukin 8 (IL-8 or CXCL8) and impairs essential IL-8 signaling processes. As a result, neutrophil migration, bacterial killing, and the formation of neutrophil extracellular traps are strongly impaired. Also, ScpC has been identified as a potential vaccine candidate. ScpC undergoes an autocatalytic cleavage between Gln244 and Ser245, resulting in two polypeptide chains that assemble together forming the active protease. Previously, we reported that the region harboring the autocatalytic cleavage site, stretching from Gln213 to Asp272, is completely disordered. Here, we show that a deletion mutant (ScpCΔ60) of this region forms a single polypeptide chain, whose crystal structure we determined at 2.9 Å resolution. Moreover, we show that ScpCΔ60 is an active protease capable of cleaving its substrate IL-8 in a manner comparable to that of the wild type. These studies improve our understanding of the proteolytic activity of ScpC.

Strong Quantum Computational Advantage Using a Superconducting Quantum Processor.

Scaling up to a large number of qubits with high-precision control is essential in the demonstrations of quantum computational advantage to exponentially outpace the classical hardware and algorithmic improvements. Here, we develop a two-dimensional programmable superconducting quantum processor, Zuchongzhi, which is composed of 66 functional qubits in a tunable coupling architecture. To characterize the performance of the whole system, we perform random quantum circuits sampling for benchmarking, up to a system size of 56 qubits and 20 cycles. The computational cost of the classical simulation of this task is estimated to be 2-3 orders of magnitude higher than the previous work on 53-qubit Sycamore processor [Nature 574, 505 (2019)NATUAS0028-083610.1038/s41586-019-1666-5. We estimate that the sampling task finished by Zuchongzhi in about 1.2 h will take the most powerful supercomputer at least 8 yr. Our work establishes an unambiguous quantum computational advantage that is infeasible for classical computation in a reasonable amount of time. The high-precision and programmable quantum computing platform opens a new door to explore novel many-body phenomena and implement complex quantum algorithms.

Demonstration of Adiabatic Variational Quantum Computing with a Superconducting Quantum Coprocessor.

Adiabatic quantum computing enables the preparation of many-body ground states. Realization poses major experimental challenges: Direct analog implementation requires complex Hamiltonian engineering, while the digitized version needs deep quantum gate circuits. To bypass these obstacles, we suggest an adiabatic variational hybrid algorithm, which employs short quantum circuits and provides a systematic quantum adiabatic optimization of the circuit parameters. The quantum adiabatic theorem promises not only the ground state but also that the excited eigenstates can be found. We report the first experimental demonstration that many-body eigenstates can be efficiently prepared by an adiabatic variational algorithm assisted with a multiqubit superconducting coprocessor. We track the real-time evolution of the ground and excited states of transverse-field Ising spins with a fidelity that can reach about 99%.

Perceptions of risk factors for phlebitis among Malaysian nurses.

BACKGROUND: Intravenous therapy is an integral part of professional nursing practice. Nurses have a responsibility to recognise risk factors for phlebitis. AIMS: To investigate nurses' perceptions of risk factors for phlebitis in a tertiary teaching hospital in north-east Peninsular Malaysia. METHODS: A cross-sectional study of 199 randomly selected nurses were surveyed for their perceptions of risk factors for phlebitis using a self-administered questionnaire. FINDINGS: More than half of the nurses (56.8%) had a good perception levels of risk factors for phlebitis. There was a significant association between the clinical area and nurses' perceptions of risk factors for phlebitis (p=0.04). Nurses working in medical, orthopaedic, and surgical areas had slightly better perceptions than nurses working in multidisciplinary and oncology areas. CONCLUSION: These findings suggest that nurses need to continually improve their knowledge about risk factors for phlebitis to ensure safer nursing practice.

Structure of ScpC, a virulence protease from Streptococcus pyogenes, reveals the functional domains and maturation mechanism.

Group A Streptococcus (GAS; Streptococcus pyogenes) causes a wide range of infections, including pharyngitis, impetigo, and necrotizing fasciitis, and results in over half a million deaths annually. GAS ScpC (SpyCEP), a 180-kDa surface-exposed, subtilisin-like serine protease, acts as an essential virulence factor that helps S. pyogenes evade the innate immune response by cleaving and inactivating C-X-C chemokines. ScpC is thus a key candidate for the development of a vaccine against GAS and other pathogenic streptococcal species. Here, we report the crystal structures of full-length ScpC wild-type, the inactive mutant, and the ScpC-AEBSF inhibitor complex. We show ScpC to be a multi-domain, modular protein consisting of nine structural domains, of which the first five constitute the PR + A region required for catalytic activity. The four unique C-terminal domains of this protein are similar to collagen-binding and pilin proteins, suggesting an additional role for ScpC as an adhesin that might mediate the attachment of S. pyogenes to various host tissues. The Cat domain of ScpC is similar to subtilisin-like proteases with significant difference to dictate its specificity toward C-X-C chemokines. We further show that ScpC does not undergo structural rearrangement upon maturation. In the ScpC-inhibitor complex, the bound inhibitor breaks the hydrogen bond between active-site residues, which is essential for catalysis. Guided by our structure, we designed various epitopes and raised antibodies capable of neutralizing ScpC activity. Collectively, our results demonstrate the structure, maturation process, inhibition, and substrate recognition of GAS ScpC, and reveal the presence of functional domains at the C-terminal region.

Biophysical studies and modelling indicate the binding preference of TAZ WW domain for LATS1 PPxY motif.

The Hippo tumor suppressor pathway is an important regulator of cell proliferation and apoptosis, and signal transduction occurs through phosphorylation of the effector protein TAZ by the serine/threonine kinase LATS1/2. Here, we report the biophysical and computational studies to characterize the interaction between TAZ and LATS1/2 through WW domain-PPxY motif binding. We show that the TAZ WW domain exhibits a binding preference for the second of the two PPxY motifs of LATS1 in vitro. We modelled the structure of the domain in complex with LATS1 PPxY2 peptide and, through molecular dynamics simulations, show that WW domain-PPxY2 complex is stable with some flexibility in the peptide region. Next, we predict and verify that L143 and T150 of the WW domain are important for TAZ binding with the PPxY2 peptide using mutational and isothermal titration calorimetric studies. Furthermore, we suggest that the electrostatic potential of charged residues within the binding pocket may influence the ligand affinity among otherwise highly similar WW domains.

[The subtle anatomical structures of normal nasal bone in MSCT image and forensic identification].

OBJECTIVE: To summarize the subtle anatomical structures of the normal nasal bone in multi-slice spiral CT (MSCT) image through the observation of the three-dimensional images. METHODS: One hundred and twenty volunteers who had no nasal trauma and disease history were collected. The nasal was scanned using MSCT. Raw data was reconstructed into bone window images (slice thickness 0.6 mm, slice interval 0.5 mm), and then the images were imported into Syngo Imaging XS software to reconstruct three-dimensional images and to summarize the nasal bone's subtle anatomical structures. RESULTS: The subtle anatomy of normal nasal bone generally included four seams, two holes and one edge. The four seams were left and right nasal-maxillary suture, nasal-frontal seam, and internasal suture. The two holes were left and right nasal aperture. The edge of the nasal was the lower edge of the nasal bone. In addition, there was suture bone in internasal suture in some normal nose. The nasal aperture mostly was hole-like, but some nasal apertures were line shape. The nasal edge can be divided into flat type, wave-shaped type, inverted spike type, hook-shaped type and others. CONCLUSION: The anatomy diversity and individual differences in nasal bone are large. MSCT and three-dimensional image reconstruction techniques, combined with the history of trauma could distinguish between the normal anatomy and fractures.

[Automated assessment of developmental levels of epiphysis by support vector machine].

OBJECTIVE: To realize the automated assessment of the levels of epiphysis of distal radius and ulna by support vector machine (SVM). METHODS: The X-ray films of the left wrist joints were taken from 140 teenagers aged from 11 to 19 years old as training samples. The levels of epiphysis of distal radius and ulna were divided into five developmental levels. Each level contained 28 samples. Another 35 cases were selected as independent verifying samples. SVM classification models of the five developmental levels of epiphysis of distal radius and ulna were established. The internal cross validation was made by leave one out cross validation (LOOCV), while the external validation was made by histogram of oriented gradient (HOG), and then the accuracy (PA) of testing results was calculated, respectively. RESULTS: The PA of SVM, LOOCV and HOG of distal radius epiphyseal level were 100%, 78.6%, and 82.8%, respectively; whereas the PA of SVM, LOOCV and HOG of distal ulna epiphyseal level were 100.0%, 80.0% and 88.6%, respectively. CONCLUSION: The SVM-based automatic models of the growth stage of distal ra- dius and ulna appear to have certain feasibility, and may provide a foundation for software development of bone age assessment by forensic medicine.

[Coronary angiography of in vitro porcine heart using MSCT].

OBJECTIVE: To establish standardized methods and parameters of the isolated heart coronary angiography through the experiment of in vitro porcine heart by MSCT. METHODS: Based on different perfusion volume (50, 60 and 70 mL) and different perfusion-imaging time (5, 10 and 20 min), the in vitro porcine coronary artery was injected liposoluble and water-soluble contrast agents using remodel angiography equipment and scanned by MSCT. And the 3D image results were compared. The images were recorded and evaluated by 2 radiologists and analyzed by statistical software. RESULTS: Liposoluble contrast agent affected the images by damaging and infiltrating the fats around the coronary artery, while the water-soluble contrast agent didn't affect the images. The groups with 60 mL or 70 mL perfusion and 5 min perfusion-imaging time had the best images. CONCLUSION: The suitable parameters of the angiography lay the foundation of postmortem coronary angiography.

Realization of fractional quantum Hall state with interacting photons.

Fractional quantum Hall (FQH) states are known for their robust topological order and possess properties that are appealing for applications in fault-tolerant quantum computing. An engineered quantum platform would provide opportunities to operate FQH states without an external magnetic field and enhance local and coherent manipulation of these exotic states. We demonstrate a lattice version of photon FQH states using a programmable on-chip platform based on photon blockade and engineering gauge fields on a two-dimensional circuit quantum electrodynamics system. We observe the effective photon Lorentz force and butterfly spectrum in the artificial gauge field, a prerequisite for FQH states. After adiabatic assembly of Laughlin FQH wave function of 1/2 filling factor from localized photons, we observe strong density correlation and chiral topological flow among the FQH photons. We then verify the unique features of FQH states in response to external fields, including the incompressibility of generating quasiparticles and the smoking-gun signature of fractional quantum Hall conductivity. Our work illustrates a route to the creation and manipulation of novel strongly correlated topological quantum matter composed of photons and opens up possibilities for fault-tolerant quantum information devices.

[Mathematical models of the teenager's skeletal age evaluation based on CT scan and imaging reconstruction of medial clavicular epiphysis].

OBJECTIVE: To explore the correlation between CT volume rendering (VR) statistics and living age and to build the mathematical models for skeletal age evaluation based on the growth rules of medial clavicular epiphysis of teenagers in China. METHODS: The thin layer CT scan and VR 3D imaging reconstruction of both sides of sternal ends of clavicles were examined for 684 teenagers aged from 15 to 25 in East and South China. The parameters of sternal end of clavicle including the longest diameter of epiphysis, the longest diameter of metaphysis, their length radio, area of epiphysis, area of metaphysic, their area ratio, and other data were measured and calculated in order to establish mathematical models of skeletal age evaluation. Fifty trained subjects were tested to verify the accuracy of the mathematical models. RESULTS: In the same age group, the length ratio and the area ratio had significant difference in genders (P < 0.05). The established mathematical models showed that the growth rules of medial clavicular epiphysis were highly correlated with the living ages. The accuracies of these models were higher than 70.5% +/- 1.0 year) and 82.5% (+/- 1.5 year). CONCLUSION: The mathematical models have easy operability and high accuracy. It can be used to confirm and sustain the conclusion of atlas method. Meanwhile, it is of great significance to study the other single skeletal age evaluation in the future.

[The staging method of sternal end of clavicle epiphyseal growth by thin layer CT scan and imaging reconstruction].

OBJECTIVE: To establish a CT staging method of sternal end of clavicle epiphyseal growth for teenagers by thin layer CT scan, multiplanar reconstruction (MPR) and volume reconstruction (VR) technologies. METHODS: The CT imaging characteristics, which collected from 460 teenagers (aged from 15 to 25) in East and South China, were studied through both sternal ends of clavicles' imagings by thin layer coronal CT scan and axial CT scan, MPR and VR technologies. The parameters of sternal end of clavicle including the longest diameter of epiphysis, the longest diameter of metaphysis, their length ratio, area of epiphysis, area of metaphysis, and their area ratio were measured and calculated in order to establish new classification. RESULTS: Based on the staging method of Schmeling, integrating the CT imaging reconstruction information of sternal end of clavicle, the new classification of sternal end of clavicle epiphyseal growth were divided into 1 to 5 stages, and stage 2 and stage 3, respectively, contained a, b and c sub-classification. CONCLUSION: This new classification has merits of large sample size, wide age range and easy operability. By using CT imaging reconstruction techniques and analyzing the data which closely related to sternal end of clavicle epiphyseal growth of teenagers, the feasibility of the staging method could be increased.

[Progress in thin layer CT scan technology in estimating skeletal age of sternal end of clavicle].

It is practical value for determination the teenagers whether the age is full of the legal responsibility age of 18 years old or not by estimating skeletal age of sternal end of clavicle. The traditional methods mainly based on X-ray radiography. However, sternal end of clavicle and adjacent lung, bronchus, sternum, rib, transverse process of thoracic vertebra are overlapped each other. As a result of overlapping, there will be obtained false negative or positive film reading results when according to X-ray observation of epiphyseal growth of sternal end of clavicle, which directly affect the scientificalness and accuracy of estimating of skeletal age. In recent years, the scholars at home and abroad have started to use thin layer CT scan technology to estimate skeletal age of the sternal end of clavicle. With the 2D and 3D CT recombination technology, the accuracy of the film reading distinctly improves by making the shape, size and position of epiphysis displayed clearly. This article reviews the application and research progress of thin layer CT scanning technology in estimating skeletal age of sternal end of clavicle at home and abroad, analyzes the superiority and value of thin layer CT scan technology, which applied to skeletal age of sternal end of clavicle.

[Bone development trend in the knee joint of Tibetan teenagers in Aba Prefecture of Sichuan Province].

OBJECTIVE: To discuss bone development trend in the knee joint of Tibetan teenagers in Sichuan province and to effectively update the database for estimating the living age of Tibetan teenagers in terms of bone age of the knee joint. METHODS: Radiographs including epiphysis of distal femur, proximal tibia and proximal fibula were taken from 483 Tibetan male and female teenagers aged from 14 to 19 years old in Aba prefecture of Sichuan province in order to observe epiphyseal growth situation. The descriptive data of the epiphyseal closure ages of these teenagers' knee joints were statistically analyzed by SPSS 16.0 software. RESULTS: The distal femur epiphyseal closure occurred earliest, while the proximal fibula epiphyseal closure occurred latest. The epiphyseal growth of knee joints of females occurred about one year earlier than that of males. CONCLUSION: The forensic information and data related to Tibetan teenagers' bone age identification should be updated regularly. These results provide potential value for the practice of forensic medicine, anthropology and clinical medicine.

Mathematical models for teenager's living age evaluation based on CT image of medial clavicular epiphysis.

OBJECTIVE: To explore the correlation between volume rendering (VR) statistics of medial clavicular epiphysis and living age, and establish the mathematical models for living age evaluation using the CT image of medial clavicular epiphysis based on the growth rules of osteoepiphysis of medial clavicle. METHODS: The CT images of the medial clavicles from 795 teenagers aged 15-25, 387 males and 408 females, were collected in East and South China. VR 3D images were reconstructed from 0.60 mm-thick slice CT images. The epiphyseal diameter, sternal end diameter, and their respective diameter ratio (the left: X1; the right: x3); epiphyseal area, sternal end area, and their respective area ratio (the left: x2; the right: x4), were measured and calculated. All these observations were analyzed using SPSS 19.0 statistical software. The statistical differences in gender and age were analyzed by Mann-Whitney U test. The mathematical models were established using least square. Sixty trained subjects, 30 males and 30 females, were tested to verify the accuracy of the established mathematical models. RESULTS: In the group of same age, x1 showed significant difference in gender; the same results were observed in x2, x3, and x4, which suggested that the growth rules of osteoepiphysis of medial clavicle were highly correlated with living age. The accuracy of these mathematical models were all above 67.6% (+/- 1.0 year) and 78.5% (+/- 1.5 year). CONCLUSION: The mathematical models with reasonable accuracy could be manageable in practice to confirm the conclusion of the atlas method. The current study can contribute to the single skeletal age evaluation.