*Nat Commun ; 13(1): 3412, 2022 Jun 14.*

##### RESUMO

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.

*Phys Rev Lett ; 128(20): 200502, 2022 May 20.*

##### RESUMO

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.

*Phys Rev Lett ; 128(16): 160504, 2022 Apr 22.*

##### RESUMO

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.

*Phys Rev Lett ; 127(14): 143201, 2021 Oct 01.*

##### RESUMO

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.

*Phys Rev Lett ; 127(9): 090501, 2021 Aug 27.*

##### RESUMO

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.

*Phys Rev Lett ; 127(6): 060505, 2021 Aug 06.*

##### RESUMO

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.

*Phys Rev Lett ; 126(15): 152502, 2021 Apr 16.*

##### RESUMO

A new α-emitting isotope ^{214}U, produced by the fusion-evaporation reaction ^{182}W(^{36}Ar,4n)^{214}U, was identified by employing the gas-filled recoil separator SHANS and the recoil-α correlation technique. More precise α-decay properties of even-even nuclei ^{216,218}U were also measured in the reactions of ^{40}Ar, ^{40}Ca beams with ^{180,182,184}W targets. By combining the experimental data, improved α-decay reduced widths Î´^{2} for the even-even Po-Pu nuclei in the vicinity of the magic neutron number N=126 are deduced. Their systematic trends are discussed in terms of the N_{p}N_{n} scheme in order to study the influence of proton-neutron interaction on α decay in this region of nuclei. It is strikingly found that the reduced widths of ^{214,216}U are significantly enhanced by a factor of two as compared with the N_{p}N_{n} systematics for the 84≤Z≤90 and N<126 even-even nuclei. The abnormal enhancement is interpreted by the strong monopole interaction between the valence protons and neutrons occupying the π1f_{7/2} and ν1f_{5/2} spin-orbit partner orbits, which is supported by the large-scale shell model calculation.

*Nat Commun ; 12(1): 1126, 2021 Feb 18.*

##### RESUMO

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.

*Phys Rev Lett ; 125(3): 032502, 2020 Jul 17.*

##### RESUMO

A new, very short-lived neutron-deficient isotope ^{222}Np was produced in the complete-fusion reaction ^{187}Re(^{40}Ar,5n)^{222}Np, and observed at the gas-filled recoil separator SHANS. The new isotope ^{222}Np was identified by employing a recoil-α correlation measurement, and six α-decay chains were established for it. The decay properties of ^{222}Np with E_{α}=10016(33) keV and T_{1/2}=380_{-110}^{+260} ns were determined experimentally. The α-decay systematics of Np isotopes is improved by adding the new data for ^{222}Np, which validates the N=126 shell effect in Np isotopes. The evolution of the N=126 shell closure is discussed in the neutron-deficient nuclei up to Np within the framework of α-decay reduced width.

*Phys Rev Lett ; 124(24): 240504, 2020 Jun 19.*

##### RESUMO

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.

*Sci Adv ; 6(21): eaba7292, 2020 May.*

##### RESUMO

The Kibble-Zurek mechanism provides a unified theory to describe the universal scaling laws in the dynamics when a system is driven through a second-order quantum phase transition. However, for first-order quantum phase transitions, the Kibble-Zurek mechanism is usually not applicable. Here, we experimentally demonstrate and theoretically analyze a power-law scaling in the dynamics of a spin-1 condensate across a first-order quantum phase transition when a system is slowly driven from a polar phase to an antiferromagnetic phase. We show that this power-law scaling can be described by a generalized Kibble-Zurek mechanism. Furthermore, by experimentally measuring the spin population, we show the power-law scaling of the temporal onset of spin excitations with respect to the quench rate, which agrees well with our numerical simulation results. Our results open the door for further exploring the generalized Kibble-Zurek mechanism to understand the dynamics across first-order quantum phase transitions.

*Zhonghua Nei Ke Za Zhi ; 59(7): 528-534, 2020 Jul 01.*

##### RESUMO

Objective: To investigate the significance of plasma pentraxin 3 (PTX3) in patients with secondary hemophagocytic lymphohistiocytosis (sHLH). Methods: Plasma PTX3 levels were tested by ELISA in 48 newly diagnosed sHLH patients, 18 healthy volunteers and 9 lymphoma controls in the First Affiliated Hospital of Nanjing Medical University from January 2017 to July 2019. Clinical parameters were collected, and the correlations with PTX3 levels were analyzed. Results: PTX3 level in newly diagnosed group was significantly higher than that of healthy control group [16.29(1.17-66.00) vs. 0.76(0.01-7.86) µg/L, P<0.01]. Patients with lymphoma-associated HLH(LHLH) had higher plasma level of PTX3 than Fhose with infection-associated HLH (IHLH) [24.29(3.36-66.00) vs. 9.56(1.17-36.50)µg/L, P<0.05]. Plasma PTX3 levels in 48 sHLH patients were positively correlated with serum ferritin (P<0.05). Receiver operating characteristic (ROC) curve for plasma PTX3 levels of sHLH and healthy controls produced a cutoff value at 3.9 µg/L, with its 86.7% sensitivity and 94.4% specificity. And ROC analysis showed that PTX3 17.5 µg/L was the critical value for diagnosis of LHLH from non-LHLH group, that the sensitivity and specificity were 63.0% and 76.2% respectively. The 1-year overall survival (OS) rate in patients with PTX3≥17.5 µg/L was significantly lower in those with PTX3<17.5 µg/L (18.5% vs. 75.8%, P<0.01). Conclusion: These results indicate the potential of PTX3 as a biomarker for diagnosis and prognosis in patients with sHLH.

##### Assuntos

Proteína C-Reativa , Linfo-Histiocitose Hemofagocítica , Componente Amiloide P Sérico , Biomarcadores Tumorais , Proteína C-Reativa/análise , Humanos , Linfo-Histiocitose Hemofagocítica/diagnóstico , Curva ROC , Sensibilidade e Especificidade , Componente Amiloide P Sérico/análise*Phys Rev Lett ; 124(4): 043001, 2020 Jan 31.*

##### RESUMO

Dynamical quantum phase transitions are closely related to equilibrium quantum phase transitions for ground states. Here, we report an experimental observation of a dynamical quantum phase transition in a spinor condensate with correspondence in an excited state phase diagram, instead of the ground state one. We observe that the quench dynamics exhibits a nonanalytical change with respect to a parameter in the final Hamiltonian in the absence of a corresponding phase transition for the ground state there. We make a connection between this singular point and a phase transition point for the highest energy level in a subspace with zero spin magnetization of a Hamiltonian. We further show the existence of dynamical phase transitions for finite magnetization corresponding to the phase transition of the highest energy level in the subspace with the same magnetization. Our results open a door for using dynamical phase transitions as a tool to probe physics at higher energy eigenlevels of many-body Hamiltonians.

*Phys Rev Lett ; 123(14): 140602, 2019 Oct 04.*

##### RESUMO

We elucidate the relation between out-of-time-order correlators (OTOCs) and quantum phase transitions via analytically studying the OTOC dynamics in a degenerate spectrum. Our method points to key ingredients to dynamically detect quantum phases via out-of-time-order correlators for a wide range of quantum phase transitions and explains the existing numerical results in the literature. We apply our method to a critical model, the XXZ model that numerically confirms our predictions.

*Phys Rev Lett ; 123(7): 076401, 2019 Aug 16.*

##### RESUMO

We study amorphous systems with completely random sites and find that, through constructing and exploring a concrete model Hamiltonian, such a system can host an exotic phase of topological amorphous metal in three dimensions. In contrast to the traditional Weyl semimetals, topological amorphous metals break translational symmetry, and thus they cannot be characterized by the first Chern number defined based on the momentum space band structures. Instead, their topological properties will manifest in the Bott index and the Hall conductivity as well as the surface states. By studying the energy band and quantum transport properties, we find that topological amorphous metals exhibit a diffusive metal behavior. We further introduce a practical experimental proposal with electric circuits where the predicted phenomena can be observed using state-of-the-art technologies. Our results open the door to exploring topological gapless phenomena in amorphous systems.

*Nat Commun ; 10(1): 4382, 2019 09 26.*

##### RESUMO

Two-mode interferometers lay the foundations for quantum metrology. Instead of exploring quantum entanglement in the two-mode interferometers, a single bosonic mode also promises a measurement precision beyond the shot-noise limit (SNL) by taking advantage of the infinite-dimensional Hilbert space of Fock states. Here, we demonstrate a single-mode phase estimation that approaches the Heisenberg limit (HL) unconditionally. Due to the strong dispersive nonlinearity and long coherence time of a microwave cavity, quantum states of the form [Formula: see text] can be generated, manipulated and detected with high fidelities, leading to an experimental phase estimation precision scaling as â¼N-0.94. A 9.1 dB enhancement of the precision over the SNL at N = 12 is achieved, which is only 1.7 dB away from the HL. Our experimental architecture is hardware efficient and can be combined with quantum error correction techniques to fight against decoherence, and thus promises quantum-enhanced sensing in practical applications.

*Zhonghua Xue Ye Xue Za Zhi ; 40(6): 502-506, 2019 Jun 14.*

##### RESUMO

Objective: To investigate the clinical characteristics of secondary hemophagocytic lymphohistiocytosis (sHLH) complicated with capillary leak syndrome (CLS) . Methods: The clinical and laboratory data of 87 sHLH patients, who were treated in our hospital between January 2015 and December 2017, were retrospectively analyzed. Depending on whether they were complicated with CLS, 21 sHLH patients were classified as the CLS-sHLH group, while 66 were classified as the non-CLS-sHLH group. The differences of clinical manifestations, laboratory tests, treatment and prognosis between the two groups were compared. Results: There was no significant difference in the etiology of sHLH between the CLS-sHLH group and the non-CLS-sHLH group (P>0.05) . The neutrophil, fibrinogen and albumin levels in the CLS-sHLH group were lower than those in the non-CLS-sHLH group, while the triacylglycerol levels were higher than those in the non-CLS-sHLH group (P<0.05) . Varying degrees of edema, weight gain, hypotension, hypoproteinemia, oliguria and multiple serous effusions were observed in the CLS-sHLH group. Among them, there were 15 patients that CLS get improved, and the medial time of improvement was 7 (5-14) days. The other 6 patients did not get remission, while they died within 6-30 days. The median overall survival of the CLS-sHLH group was lower than that of the non-CLS-sHLH group (75 days vs not reached, P=0.031) . Conclusions: There may be no correlation between the cause of sHLH and the occurrence of CLS. Severity of neutropenia, fibrinogen and albumin levels, and triglyceride levels may be accompanied for sHLH patients complicated with CLS. Patients with sHLH who complicated with CLS have a poor prognosis. Active treatment of HLH and its primary disease, reasonable fluid replacement and oxygen supply are crucial, which can effectively control disease progression.

##### Assuntos

Síndrome de Vazamento Capilar , Linfo-Histiocitose Hemofagocítica , Fibrinogênio , Humanos , Prognóstico , Estudos Retrospectivos*Phys Rev Lett ; 122(19): 192503, 2019 May 17.*

##### RESUMO

A new short-lived neutron-deficient isotope ^{220}Np was synthesized in the fusion-evaporation reaction ^{185}Re(^{40}Ar,5n)^{220}Np at the gas-filled recoil separator SHANS. Based on the measurement of the correlated α-decay chains, the decay properties of ^{220}Np with E_{α}=10040(18) keV and T_{1/2}=25_{-7}^{+14} µs were determined, which are in good agreement with theoretical predictions. From the new experimental results coupled with the recently reported α-decay data of ^{219,223}Np, the α-decay systematics for Np isotopes around N=126 was established, which allows us for the first time to test the robustness of the N=126 shell closure in Z=93 Np isotopes. The results also indicate that, in the region of nuclei with Z≥83, the proton drip line has been reached for all odd-Z isotopes up to Np.

*Phys Rev Lett ; 122(1): 010503, 2019 Jan 11.*

##### RESUMO

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.

*Zhonghua Xue Ye Xue Za Zhi ; 40(12): 1040-1043, 2019 Dec 14.*