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.

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.

Realization of a crosstalk-avoided quantum network node using dual-type qubits of the same ion species.

Generating ion-photon entanglement is a crucial step for scalable trapped-ion quantum networks. To avoid the crosstalk on memory qubits carrying quantum information, it is common to use a different ion species for ion-photon entanglement generation such that the scattered photons are far off-resonant for the memory qubits. However, such a dual-species scheme can be subject to inefficient sympathetic cooling due to the mass mismatch of the ions. Here we demonstrate a trapped-ion quantum network node in the dual-type qubit scheme where two types of qubits are encoded in the S and F hyperfine structure levels of 171Yb+ ions. We generate ion photon entanglement for the S-qubit in a typical timescale of hundreds of milliseconds, and verify its small crosstalk on a nearby F-qubit with coherence time above seconds. Our work demonstrates an enabling function of the dual-type qubit scheme for scalable quantum networks.

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.

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.

Observation of supersymmetry and its spontaneous breaking in a trapped ion quantum simulator.

Supersymmetry (SUSY) helps solve the hierarchy problem in high-energy physics and provides a natural groundwork for unifying gravity with other fundamental interactions. While being one of the most promising frameworks for theories beyond the Standard Model, its direct experimental evidence in nature still remains to be discovered. Here we report experimental realization of a supersymmetric quantum mechanics (SUSY QM) model, a reduction of the SUSY quantum field theory for studying its fundamental properties, using a trapped ion quantum simulator. We demonstrate the energy degeneracy caused by SUSY in this model and the spontaneous SUSY breaking. By a partial quantum state tomography of the spin-phonon coupled system, we explicitly measure the supercharge of the degenerate ground states, which are superpositions of the bosonic and the fermionic states. Our work demonstrates the trapped-ion quantum simulator as an economic yet powerful platform to study versatile physics in a single well-controlled system.

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.

Proton Compton Scattering from Linearly Polarized Gamma Rays.

Differential cross sections for Compton scattering from the proton have been measured at scattering angles of 55°, 90°, and 125° in the laboratory frame using quasimonoenergetic linearly (circularly) polarized photon beams with a weighted mean energy value of 83.4 MeV (81.3 MeV). These measurements were performed at the High Intensity Gamma-Ray Source facility at the Triangle Universities Nuclear Laboratory. The results are compared to previous measurements and are interpreted in the chiral effective field theory framework to extract the electromagnetic dipole polarizabilities of the proton, which gives α_{E1}^{p}=13.8±1.2_{stat}±0.1_{BSR}±0.3_{theo},ß_{M1}^{p}=0.2∓1.2_{stat}±0.1_{BSR}∓0.3_{theo} in units of 10^{-4} fm^{3}.

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.

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.

Observation of a quantum phase transition in the quantum Rabi model with a single trapped ion.

Quantum phase transitions (QPTs) are usually associated with many-body systems in the thermodynamic limit when their ground states show abrupt changes at zero temperature with variation of a parameter in the Hamiltonian. Recently it has been realized that a QPT can also occur in a system composed of only a two-level atom and a single-mode bosonic field, described by the quantum Rabi model (QRM). Here we report an experimental demonstration of a QPT in the QRM using a 171Yb+ ion in a Paul trap. We measure the spin-up state population and the average phonon number of the ion as two order parameters and observe clear evidence of the phase transition via adiabatic tuning of the coupling between the ion and its spatial motion. An experimental probe of the phase transition in a fundamental quantum optics model without imposing the thermodynamic limit opens up a window for controlled study of QPTs and quantum critical phenomena.

Quantum Communication between Multiplexed Atomic Quantum Memories.

The use of multiplexed atomic quantum memories (MAQM) can significantly enhance the efficiency to establish entanglement in a quantum network. In the previous experiments, individual elements of a quantum network, such as the generation, storage, and transmission of quantum entanglement have been demonstrated separately. Here we report an experiment to show the compatibility and integration of these basic operations. Specifically, we generate photon-atom entanglement from any chosen pair of memory cells in a 6×5 MAQM, convert the spin-wave to time-bin photonic excitation after a controllable storage time, and then store and retrieve the photon in a second MAQM for another controllable storage time. The preservation of quantum information in this process is verified by measuring the state fidelity. We also demonstrate that higher dimension quantum states can be transferred between the two distant MAQMs.

A three-generation family cluster with COVID-19 infection: should quarantine be prolonged?

OBJECTIVES: Families are a transmission route for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) because of the close contact. Monitoring of the viral load will be a valuable method to reduce the optimal number of quarantine days, especially in presymptomatic and symptomatic carriers of their households. The traditional three-generation families living together are seen frequently in East Asia, including in Taiwan. STUDY DESIGN: We report on a family cluster with six individuals infected with coronavirus disease in Taiwan. METHODS: The current public policy in Taiwan is quarantine for at least 14 days, based on the incubation period, or until the patient has tested negative three days in a row using the SARS-CoV-2 reverse transcription polymerase chain reaction. Details on the onset date of clinical symptoms, throat swab conversion, and course of disease were collected from medical records retrospectively. RESULTS: In the household of this three-generation Taiwanese family, the infection rate was 60%. The ratio of males to females was 4:2, and the age range was 11-85 years. The prevalence of asymptomatic disease was 33.3% (2/6). The longest throat swab conversion time was 37 days, and the estimated course of disease from symptoms to first conversion of throat swab was 59 days. CONCLUSIONS: Large families, including three-generation families in a single dwelling, should be monitored when the index case is found. Presymptomatic and symptomatic family members could be quarantined for an appropriate duration which, in our experience, is 2 months.

Experimental Realization of Robust Geometric Quantum Gates with Solid-State Spins.

We experimentally realize a universal set of single-bit and two-bit geometric quantum gates by adiabatically controlling solid-state spins in a diamond defect. Compared with the nonadiabatic approach, the adiabatic scheme for geometric quantum computation offers a unique advantage of inherent robustness to parameter variations, which is explicitly demonstrated in our experiment by showing that the single-bit gates remain unchanged when the driving field amplitude varies by a factor of 2 or the detuning fluctuates in a range comparable to the inverse of the gate time. The reported adiabatic control technique and its convenient implementation offer a paradigm for achieving quantum computation through robust geometric quantum gates, which is important for quantum information systems with parameter-fluctuation noise such as those from the inhomogeneous coupling or the spectral diffusion.

Aberrant activation of the type I interferon system may contribute to the pathogenesis of anti-melanoma differentiation-associated gene 5 dermatomyositis.

BACKGROUND: Anti-melanoma differentiation-associated gene 5 (MDA5) dermatomyositis (DM) is a distinctive subtype of DM that carries a significant risk of interstitial lung disease (ILD). The mechanisms remain elusive. OBJECTIVES: To explore the role of the type I interferon (IFN) system in the pathogenesis of anti-MDA5 DM. METHODS: Twenty patients with anti-MDA5 DM were studied and compared with patients with anti-aminoacyl-tRNA synthetase (ARS) DM (n = 10) and autoantibody-negative patients with DM (n = 20). The levels of inflammatory cytokines, B-cell-activating factor (BAFF) and Krebs von den Lungen (KL)-6 in blood were tested by enzyme-linked immunosorbent assay and multiplex assays. Expressions of transcripts for IFN-associated sensors and type I IFN-inducible genes in peripheral blood mononuclear cells (PBMCs) were detected by real-time polymerase chain reaction. Expressions of the signal transducer and activator of transcription (STAT)1, interferon-stimulated gene (ISG)15 and MxA proteins in skin lesions were analysed by immunohistochemistry. RESULTS: Plasma IFN-α levels were significantly increased in patients with anti-MDA5 DM. PBMCs from patients with anti-MDA5 DM showed significant upregulation of the TLR3, TLR7, IFIH1 and DDX58 genes, as well as serial IFN-inducible genes. Skin biopsies from patients with anti-MDA5 DM were characterized by strong expression of the STAT1, ISG15 and MxA proteins. In the patients with anti-MDA5 DM and ILD with high IFN-α production, there was a positive quantitative correlation between IFN-α and BAFF (rs = 0·63, P = 0·044). In addition, the higher levels of BAFF paralleled the higher concentrations of KL-6 (rs = 0·86, P = 0·0012). CONCLUSIONS: Our data confirm the aberrant activation of the type I IFN system in anti-MDA5 DM. Overproduction of IFN-α linked with BAFF may be implicated in the development of ILD.

[Centronuclear myopathy: clinical characteristics and MRI image features of oral and maxillofacial region].

Objective: To provide biomechnical basis for orthodontics of centronuclear myopathy (CNM) patients, we studied the oral and maxillofacial clinical features and MRI image manifestations to explore application of MRI to objective evaluation the affected facial muscles. Methods: The study consisted of 8 patients who were diagnosed as CNM (CNM group) and 20 healthy volunteers (control group). Their medical information were gathered and then we examined the ptosis situation and the facial index calculation of them. To measure the maximal hight of palate and the width of palate, patients and volunteers were made impressions. We also checked their maximum bite force with occlusion pressure tester. And they took lateral cephalometric radiographs to measure mandibular plane-Frankfort horizontal plane angle (MP-FH). At last, they were taken oral and maxillofacial region MRI to observe the affected situation of masseter muscle, medial pterygoid muscle and lateral pterygoid muscle. Results: Six patients were ptosis; 6 patients had inverse V-shaped mouth; 3 patients were difficulty in swallowing; 4 patients were anterior open bites; 4 patients were mouth breathing; 7 patients liked to eat soft foods. Morphological facial index ([91.3±0.5]%), MP-FH (34.9°±2.0°) of CNM group were greater than the control group, male maximal hight of palate ([19.0±0.2] mm), female maximal hight of palate ([18.0±0.6] mm) of CNM group were greater than the control group (P<0.05). Male width of palate ([34.5±0.8] mm), female width of palate ([33.4±1.0] mm), male maximum bite force ([464.3±78.2] N), female maximum bite force ([320.7±13.8] N), maximal opening of mouth ([3.4±0.3] cm) of CNM group were less than the control group (P<0.05). And these had significant difference compared with the control group (P<0.05). In MRI examination, there were 7 patients' masseter muscles, 4 patients' medial pterygoid muscles and 6 patients' lateral pterygoid muscles to atrophy asymmetrically. These three pieces of muscular fatty infiltration were inordinately, focused on Grade 0 to 4 and the both sides were similar. Conclusions: CNM patients with long and thin face, high palatine arches and low bite force together were the biomechanical basis of the maxillofacial deformities. MRI can clearly show the affected masseter muscle, medial pterygoid muscle, lateral pterygoid muscle, and can serve as an objective examination method for the evaluation of facial muscles. It can be worth of clinical popularization and application.

[Features of facioscapulohumeral muscular dystrophy in oral and maxillofacial region and MRI analysis of facial muscles].

Objective: To investigate the manifestation of facioscapulohumeral muscular dystrophy (FSHD) in oral and maxillofacial region. Methods: A total of 12 patients diagnosed as FSHD and 20 healthy volunteers were included in the study. Their medical history was collected from these patients. The decayed missing filled teeth (DMFT), calculus index-simplified (CI-S), occlusal relationship, maximal opening of mouth and maximum bite force were recorded. The impressions were taken to measure the maximal hight of palate and the width of palate. The lateral cephalometric radiographs were also taken to measure the mandibular plane-frankfurt horizontal plane angle (MP-FH). They finally received oral and maxillofacial region MRI examination to observe the masseter muscle, medial pterygoid muscle and lateral pterygoid muscle. The data were analyzed by t-test or Wilcoxon signed ranks test. Results: There was no significant gender difference in FSHD group. The average age of treatment was (27.5 ± 8.1) years and the average age of onset was (15.7±7.5) years. Nine patients liked to eat soft foods, 4 patients had difficulties of closing eyes, 8 patients had difficulties of cheek-bulging, 10 patients showed pouty lips and 9 patients had mesio-malocclusion. DMFT (4.0±2.3), CI-S (5.8±2.1), male maximal hight of palate (20.5±2.1) mm , female maximal hight of palate (17.9±1.6) mm, MP-FH (31.8°±2.2°) of FSHD group were greater than those of the control group. Male width of palate (34.8±1.4) mm, female width of palate (33.7±1.5) mm, male maximum bite force (451.7 ± 39.0) N, female maximum bite force (326.7 ± 21.6) N, maximal opening of mouth (3.5 ± 0.4) cm of FSHD group were less than those of the control group (P <0.05). Maxillofacial MRI showed muscle asymmetr in 11 cases of masseter and 6 cases of medial pterygoid muscle, 5 cases of lateral pterygoid, and these muscle showed mild fatty infiltration mainly concentrating in the grade 0, grade 1 and grade 2. Conclusions: The FSHD patients have poor oral hygiene, low masticatory function, limited mouth opening, high palate and narrow arch and different degree of malocclusion. The patients' masseter muscle, medial pterygoid muscles and lateral pterygoid muscles exhibit asymmetrical atrophy and fatty infiltration.

Widely Tunable Two-Color Free-Electron Laser on a Storage Ring.

With a wide wavelength tuning range, free-electron lasers (FELs) are well suited for producing simultaneous lasing at multiple wavelengths. We present the first experimental results of a novel two-color storage ring FEL. With three undulators and a pair of dual-band mirrors, the two-color FEL can lase simultaneously in infrared (IR) around 720 nm and in ultraviolet (UV) around 360 nm. We have demonstrated independent wavelength tuning in a wide range (60 nm in IR and 24 nm in UV). We have also realized two-color harmonic operation with the UV lasing tuned to the second harmonic of the IR lasing. Furthermore, we have demonstrated good power stability with two-color lasing, and good control of the power sharing between the two colors.

Novel gain of function mutation in the SLC40A1 gene associated with hereditary haemochromatosis type 4.

Here we report the case of a 69-year-old Chinese Han woman who presented with liver cirrhosis, diabetes mellitus, skin hyperpigmentation, hyperferritinaemia and high transferrin saturation. Subsequent genetic analyses identified a novel heterozygous mutation (p.Cys326Phe) in the SLC40A1 gene. This is the first report regarding a SLC40A1 mutation in the Chinese Han population and provides novel clinical evidence for the importance of p.Cys326 in SLC40A1 gene function.