ISSN 0253-2778

CN 34-1054/N

Physics

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Temperature-robust diamond magnetometry based on the double-transition method
Caijin Xie, Yunbin Zhu, Yijin Xie, Tingwei Li, Wenzhe Zhang, Yifan Wang, Xing Rong
2023, 53(7): 0701. doi: 10.52396/JUSTC-2022-0150
Abstract:
As a promising solid-state sensor at room temperature, diamond magnetometers based on nitrogen-vacancy (NV) centers have been developed tremendously in recent years. Many studies have demonstrated its potential for achieving high spatial resolution and sensitivity. However, the temperature dependence of the zero-field splitting D of NV centers poses an enormous challenge for the application of diamond magnetometry, since it is difficult to avoid temperature drift in most application scenarios. Here, we demonstrate a type of temperature-robust diamond magnetometry based on the double-transition method. By utilizing both transitions between \begin{document}$|m_{\rm{s}}=0\rangle$\end{document} and \begin{document}$|m_{\rm{s}}=\pm1\rangle$\end{document} sublevels with incomplete degeneracy of the \begin{document}$|m_{\rm{s}}=\pm1\rangle$\end{document}states, the impacts of D variations induced by temperature drift can be counteracted. The drift of magnetic field measurement result has been reduced by approximately 7-fold. With further improvements, the temperature-robust diamond magnetometry has the potential to be applied in biomagnetism and space science research. As a promising solid-state sensor at room temperature, diamond magnetometers based on nitrogen-vacancy (NV) centers have been developed tremendously in recent years. Many studies have demonstrated its potential for achieving high spatial resolution and sensitivity. However, the temperature dependence of the zero-field splitting D of NV centers poses an enormous challenge for the application of diamond magnetometry, since it is difficult to avoid temperature drift in most application scenarios. Here, we demonstrate a type of temperature-robust diamond magnetometry based on the double-transition method. By utilizing both transitions between $|m_{\rm{s}}=0\rangle$ and $|m_{\rm{s}}=\pm1\rangle$ sublevels with incomplete degeneracy of the $|m_{\rm{s}}=\pm1\rangle$states, the impacts of D variations induced by temperature drift can be counteracted. The drift of magnetic field measurement result has been reduced by approximately 7-fold. With further improvements, the temperature-robust diamond magnetometry has the potential to be applied in biomagnetism and space science research.
Electronic correlation effects on stabilizing a perfect Kagome lattice and ferromagnetic fluctuation in LaRu3Si2
Yilin Wang
2023, 53(7): 0702. doi: 10.52396/JUSTC-2022-0182
Abstract:
A perfect Kagome lattice features flat bands that usually lead to strong electronic correlation effects, but how electronic correlation, in turn, stabilizes a perfect Kagome lattice has rarely been explored. Here, we study this effect in a superconducting (\begin{document}$T_{\rm{c}} \sim 7.8$\end{document} K) Kagome metal LaRu3Si2 with a distorted Kagome plane consisting of pure Ru ions, using density functional theory plus \begin{document}$ U $\end{document} and plus dynamical mean-field theory. We find that increasing electronic correlation can stabilize a perfect Kagome lattice and induce substantial ferromagnetic fluctuations in LaRu3Si2. By comparing the calculated magnetic susceptibilities to experimental data, LaRu3Si2 is found to be on the verge of becoming a perfect Kagome lattice. It thus shows moderate but non-negligible electronic correlations and ferromagnetic fluctuations, which are crucial to understand the experimentally observed non-Fermi-liquid behavior and the pretty high superconducting \begin{document}$T_{\rm{c}}$\end{document} of LaRu3Si2. A perfect Kagome lattice features flat bands that usually lead to strong electronic correlation effects, but how electronic correlation, in turn, stabilizes a perfect Kagome lattice has rarely been explored. Here, we study this effect in a superconducting ($T_{\rm{c}} \sim 7.8$ K) Kagome metal LaRu3Si2 with a distorted Kagome plane consisting of pure Ru ions, using density functional theory plus $ U $ and plus dynamical mean-field theory. We find that increasing electronic correlation can stabilize a perfect Kagome lattice and induce substantial ferromagnetic fluctuations in LaRu3Si2. By comparing the calculated magnetic susceptibilities to experimental data, LaRu3Si2 is found to be on the verge of becoming a perfect Kagome lattice. It thus shows moderate but non-negligible electronic correlations and ferromagnetic fluctuations, which are crucial to understand the experimentally observed non-Fermi-liquid behavior and the pretty high superconducting $T_{\rm{c}}$ of LaRu3Si2.
A coherent study of e+eωπ0, ωπ+π, and ωη
Yan Wu, Qinsong Zhou, Wenbiao Yan, Guangshun Huang
2023, 53(7): 0704. doi: 10.52396/JUSTC-2023-0086
Abstract:
In this work, a combined analysis is performed on the processes of \begin{document}$e^+e^-\to\omega\pi^0\pi^0$\end{document}, \begin{document}$e^+e^-\to\omega\pi^+\pi^-$\end{document}, and \begin{document}$e^+e^-\to\omega\eta$\end{document} to study possible \begin{document}$\omega$\end{document} excited states at approximately 2.2 GeV. The resonance parameters are extracted by simultaneous fits of the Born cross section line shapes of these processes. In the fit with one resonance, the mass and width are fitted to be \begin{document}$(2207\pm14)$\end{document} MeV\begin{document}$/c^2$\end{document} and \begin{document}$(104\pm16)$\end{document} MeV, respectively. The result is consistent with previous measurements. In the fit with two resonances, the mass and width for the first resonance are fitted to be \begin{document}$(2160\pm36)$\end{document} MeV\begin{document}$/c^2$\end{document} (solution I), \begin{document}$(2154\pm12)$\end{document} MeV\begin{document}$/c^2$\end{document} (solution II) and \begin{document}$(141\pm74)$\end{document} MeV (solution I), \begin{document}$(152\pm77)$\end{document} MeV (solution II), respectively. The mass and width for the second resonance are fitted to be \begin{document}$(2298\pm19)$\end{document} MeV\begin{document}$/c^2$\end{document} (solution I), \begin{document}$(2309\pm6)$\end{document} MeV\begin{document}$/c^2$\end{document} (solution II) and \begin{document}$(106\pm77)$\end{document} MeV (solution I), \begin{document}$(99\pm23)$\end{document} MeV (solution II), respectively. The result is consistent with the theoretical prediction of \begin{document}$\omega(4S)$\end{document} and \begin{document}$\omega(3D)$\end{document}. The intermediate subprocesses in \begin{document}$e^+e^-\to\omega\pi^+\pi^-$\end{document} are analyzed using the resonance parameters of the previous fits in this work. In the fit with one resonance, the fitting result of \begin{document}$\varGamma^{e^+e^-}_{{\rm{R}}}B_{{\rm{R}}}$\end{document} is partially consistent with the previous result. In the fit with two resonances, the fitting result of \begin{document}$\varGamma^{e^+e^-}_{{\rm{R}}}B_{{\rm{R}}}$\end{document} is of the same order of magnitude as the theoretical prediction. This work may provide useful information for studying the light flavor vector meson family. In this work, a combined analysis is performed on the processes of $e^+e^-\to\omega\pi^0\pi^0$, $e^+e^-\to\omega\pi^+\pi^-$, and $e^+e^-\to\omega\eta$ to study possible $\omega$ excited states at approximately 2.2 GeV. The resonance parameters are extracted by simultaneous fits of the Born cross section line shapes of these processes. In the fit with one resonance, the mass and width are fitted to be $(2207\pm14)$ MeV$/c^2$ and $(104\pm16)$ MeV, respectively. The result is consistent with previous measurements. In the fit with two resonances, the mass and width for the first resonance are fitted to be $(2160\pm36)$ MeV$/c^2$ (solution I), $(2154\pm12)$ MeV$/c^2$ (solution II) and $(141\pm74)$ MeV (solution I), $(152\pm77)$ MeV (solution II), respectively. The mass and width for the second resonance are fitted to be $(2298\pm19)$ MeV$/c^2$ (solution I), $(2309\pm6)$ MeV$/c^2$ (solution II) and $(106\pm77)$ MeV (solution I), $(99\pm23)$ MeV (solution II), respectively. The result is consistent with the theoretical prediction of $\omega(4S)$ and $\omega(3D)$. The intermediate subprocesses in $e^+e^-\to\omega\pi^+\pi^-$ are analyzed using the resonance parameters of the previous fits in this work. In the fit with one resonance, the fitting result of $\varGamma^{e^+e^-}_{{\rm{R}}}B_{{\rm{R}}}$ is partially consistent with the previous result. In the fit with two resonances, the fitting result of $\varGamma^{e^+e^-}_{{\rm{R}}}B_{{\rm{R}}}$ is of the same order of magnitude as the theoretical prediction. This work may provide useful information for studying the light flavor vector meson family.
Design of a fiber cavity ion trap for a high-efficiency and high-rate quantum network node
Xing-Yu Bao, Jin-Ming Cui, Ding Fang, Wei-Bin Chen, Jian Wang, Yun-Feng Huang, Chuan-Feng Li, Guang-Can Guo
2023, 53(7): 0705. doi: 10.52396/JUSTC-2023-0005
Abstract:
The main purpose of this paper is to design a novel coupled system of an ion trap and a fiber cavity. This integrated solution is achieved by fabricating a fiber cavity with a metal mask on the side and end faces of the fiber. The fiber cavity with the metal mask can transmit light and electric charges, and the metal mask on the fiber end-face can shield electric charges on the dielectric high-reflection film. This system is designed to trap a single \begin{document}$ ^{138}\text{Ba}^{+} $\end{document} ion and realize coupling of the fiber cavity to the fluorescence at a 493 nm wavelength of \begin{document}$ ^{138}\text{Ba}^{+} $\end{document}. To efficiently collect fluorescent photons, we perform a theoretical analysis of the overall system to achieve optimal coupling of each individual part. The cavity length is designed to be \begin{document}$ 250 $\end{document} μm, and the optimized coupling parameters are \begin{document}$(g,\kappa,\gamma)/2{\text{π}}=(55,\;105,\;20)$\end{document} MHz. We also improve the stability and reliability of the system by analyzing the vibration, performance of the ion trap, and thermal stability. The core of the system is composed of materials with similar thermal expansion coefficients to improve thermal stability. The system uses spring connections to isolate vibrations inside and outside the vacuum chamber. We theoretically solve the difficulties of manufacturing the coupled system and have completed the experimental verification of some key technologies. The whole system is expected to be extended into a complex quantum network system to realize quantum computation and communication. The main purpose of this paper is to design a novel coupled system of an ion trap and a fiber cavity. This integrated solution is achieved by fabricating a fiber cavity with a metal mask on the side and end faces of the fiber. The fiber cavity with the metal mask can transmit light and electric charges, and the metal mask on the fiber end-face can shield electric charges on the dielectric high-reflection film. This system is designed to trap a single $ ^{138}\text{Ba}^{+} $ ion and realize coupling of the fiber cavity to the fluorescence at a 493 nm wavelength of $ ^{138}\text{Ba}^{+} $. To efficiently collect fluorescent photons, we perform a theoretical analysis of the overall system to achieve optimal coupling of each individual part. The cavity length is designed to be $ 250 $ μm, and the optimized coupling parameters are $(g,\kappa,\gamma)/2{\text{π}}=(55,\;105,\;20)$ MHz. We also improve the stability and reliability of the system by analyzing the vibration, performance of the ion trap, and thermal stability. The core of the system is composed of materials with similar thermal expansion coefficients to improve thermal stability. The system uses spring connections to isolate vibrations inside and outside the vacuum chamber. We theoretically solve the difficulties of manufacturing the coupled system and have completed the experimental verification of some key technologies. The whole system is expected to be extended into a complex quantum network system to realize quantum computation and communication.
Controlled properties of perovskite oxide films by engineering oxygen octahedral rotation
Junhua Liu, Xiaofei Gao, Wen Xiao, Shilin Hu, Yaoyao Ji, Lin Li, Kai Chen, Zhaoliang Liao
2023, 53(1): 1. doi: 10.52396/JUSTC-2022-0101
Abstract:
Complex perovskite oxides exhibit extremely rich physical properties in terms of magnetism, electrical transport, and electrical polarization characteristics due to the competition and coupling of many degrees of freedom. The B-site ions and O ions in perovskite form six-coordinated octahedral units, which are connected at a common vertex toward the basic framework of the perovskite oxide, providing a crucial platform to tailor physical properties. The rotation or distortion of the oxygen octahedra will tip the competing balance, leading to many emergent ground states. To further clarify the subtle relationship between emergent properties and oxide octahedral behavior, this article reviews the structure of perovskite oxides, the characterization methods of oxygen octahedral rotation and the response of transport, electrical polarization and magnetism of several typical perovskite heterostructures to oxygen octahedral rotation modes. With knowledge of how to manipulate the octahedral rotation behavior and regulate the physical properties of perovskite oxides, rationally designing the sample manufacturing process can effectively guide the development and application of novel electronic functional materials and devices. Complex perovskite oxides exhibit extremely rich physical properties in terms of magnetism, electrical transport, and electrical polarization characteristics due to the competition and coupling of many degrees of freedom. The B-site ions and O ions in perovskite form six-coordinated octahedral units, which are connected at a common vertex toward the basic framework of the perovskite oxide, providing a crucial platform to tailor physical properties. The rotation or distortion of the oxygen octahedra will tip the competing balance, leading to many emergent ground states. To further clarify the subtle relationship between emergent properties and oxide octahedral behavior, this article reviews the structure of perovskite oxides, the characterization methods of oxygen octahedral rotation and the response of transport, electrical polarization and magnetism of several typical perovskite heterostructures to oxygen octahedral rotation modes. With knowledge of how to manipulate the octahedral rotation behavior and regulate the physical properties of perovskite oxides, rationally designing the sample manufacturing process can effectively guide the development and application of novel electronic functional materials and devices.
Twisted plasma waves driven by twisted ponderomotive force
Yin Shi, David R Blackman, Robert J Kingham, Alexey Arefiev
2023, 53(1): 3. doi: 10.52396/JUSTC-2022-0080
Abstract:
We present the results of twisted plasma waves driven by twisted ponderomotive force. With the beating of two, co-propagating, Laguerre-Gaussian (LG) orbital angular momentum (OAM) laser pulses with different frequencies and also different twist indices, we can obtain the twisted ponderomotive force. Three-dimensional particle-in-cell simulations are used to demonstrate the twisted plasma waves driven by lasers. The twisted plasma waves have an electron density perturbation with a helical rotating structure. Different from the predictions of the linear fluid theory, the simulation results show a nonlinear rotating current and a static axial magnetic field. Along with the rotating current is the axial OAM carried by particles in the twisted plasma waves. A detailed theoretical analysis of twisted plasma waves is also given. We present the results of twisted plasma waves driven by twisted ponderomotive force. With the beating of two, co-propagating, Laguerre-Gaussian (LG) orbital angular momentum (OAM) laser pulses with different frequencies and also different twist indices, we can obtain the twisted ponderomotive force. Three-dimensional particle-in-cell simulations are used to demonstrate the twisted plasma waves driven by lasers. The twisted plasma waves have an electron density perturbation with a helical rotating structure. Different from the predictions of the linear fluid theory, the simulation results show a nonlinear rotating current and a static axial magnetic field. Along with the rotating current is the axial OAM carried by particles in the twisted plasma waves. A detailed theoretical analysis of twisted plasma waves is also given.
Twenty years of quantum contextuality at USTC
Zheng-Hao Liu, Qiang Li, Bi-Heng Liu, Yun-Feng Huang, Jin-Shi Xu, Chuan-Feng Li, Guang-Can Guo
2022, 52(10): 1. doi: 10.52396/JUSTC-2022-0073
Abstract:
Quantum contextuality is one of the most perplexing and peculiar features of quantum mechanics. Concisely, it refers to the observation that the result of a single measurement in quantum mechanics depends on the set of joint measurements actually performed. The study of contextuality has a long history at the University of Science and Technology of China (USTC). Here we review the theoretical and experimental advances in this direction achieved at USTC over the last twenty years. We start by introducing the renowned simplest proof of state-independent contextuality. We then present several experimental tests of quantum versus noncontextual theories with photons. Finally, we discuss the investigation of the role of contextuality in general quantum information science and its application in quantum computation. Quantum contextuality is one of the most perplexing and peculiar features of quantum mechanics. Concisely, it refers to the observation that the result of a single measurement in quantum mechanics depends on the set of joint measurements actually performed. The study of contextuality has a long history at the University of Science and Technology of China (USTC). Here we review the theoretical and experimental advances in this direction achieved at USTC over the last twenty years. We start by introducing the renowned simplest proof of state-independent contextuality. We then present several experimental tests of quantum versus noncontextual theories with photons. Finally, we discuss the investigation of the role of contextuality in general quantum information science and its application in quantum computation.
Design and optimization of transparent scattering solar concentrator based on SiO2 aerogel
Feng Zhang, Jun Bao, Chen Gao
2022, 52(10): 2. doi: 10.52396/JUSTC-2022-0047
Abstract:
Scattering solar concentrators (SSCs), an important component of transparent/translucent photovoltaic devices, can concentrate large-area sunlight on small-area solar cells while allowing some sunlight to pass through the devices. However, owing to the lack of suitable scattering materials, there have been few reports on SSCs in recent years. In this study, we fabricated SiO2 aerogel-based SSCs and tested their performances. The photoelectric performance was found to be moderate. Additionally, the results demonstrated excellent transmittance and color rendering index, which meet the lighting requirements of the windows. A Monte Carlo ray tracing program was developed to simulate an SSC and analyze the fate of all photons. We also analyzed the multiple scattering mechanism in SSCs that damages the photoelectric efficiency of a device via theoretical simulation. Finally, we proposed an anisotropic scattering device that can increase the primary scattering and suppress multiple scattering, resulting in excellent photoelectric efficiency. Scattering solar concentrators (SSCs), an important component of transparent/translucent photovoltaic devices, can concentrate large-area sunlight on small-area solar cells while allowing some sunlight to pass through the devices. However, owing to the lack of suitable scattering materials, there have been few reports on SSCs in recent years. In this study, we fabricated SiO2 aerogel-based SSCs and tested their performances. The photoelectric performance was found to be moderate. Additionally, the results demonstrated excellent transmittance and color rendering index, which meet the lighting requirements of the windows. A Monte Carlo ray tracing program was developed to simulate an SSC and analyze the fate of all photons. We also analyzed the multiple scattering mechanism in SSCs that damages the photoelectric efficiency of a device via theoretical simulation. Finally, we proposed an anisotropic scattering device that can increase the primary scattering and suppress multiple scattering, resulting in excellent photoelectric efficiency.
Pure state tomography with adaptive Pauli measurements
Xiangrui Meng, Minggen He, Zhensheng Yuan
2022, 52(8): 1. doi: 10.52396/JUSTC-2022-0037
Abstract:
Quantum state tomography provides a key tool for validating and fully exploiting quantum resources. However, current protocols of pure-state informationally-complete (PS-IC) measurement settings generally involve various multi-qubit gates or complex quantum algorithms, which are not practical for large systems. In this study, we present an adaptive approach to \begin{document}$N$\end{document}-qubit pure-state tomography with Pauli measurements. First, projective measurements on each qubit in the Z-direction were implemented to determine the amplitude of each base of the target state. Then, a set of Pauli measurement settings was recursively deduced by the Z-measurement results, which can be used to determine the phase of each base. The number of required measurement settings is \begin{document}$O(N)$\end{document} for certain quantum states, including cluster and W states. Finally, we numerically verified the feasibility of our strategy by reconstructing a 1-D chain state using a neural network algorithm. Quantum state tomography provides a key tool for validating and fully exploiting quantum resources. However, current protocols of pure-state informationally-complete (PS-IC) measurement settings generally involve various multi-qubit gates or complex quantum algorithms, which are not practical for large systems. In this study, we present an adaptive approach to $N$-qubit pure-state tomography with Pauli measurements. First, projective measurements on each qubit in the Z-direction were implemented to determine the amplitude of each base of the target state. Then, a set of Pauli measurement settings was recursively deduced by the Z-measurement results, which can be used to determine the phase of each base. The number of required measurement settings is $O(N)$ for certain quantum states, including cluster and W states. Finally, we numerically verified the feasibility of our strategy by reconstructing a 1-D chain state using a neural network algorithm.
Non-Hermitian skin effect in a spin-orbit-coupled Bose-Einstein condensate
Haowei Li, Xiaoling Cui, Wei Yi
2022, 52(8): 2. doi: 10.52396/JUSTC-2022-0003
Abstract:
We study a Bose-Einstein condensate of ultracold atoms subject to a non-Hermitian spin-orbit coupling, where the system acquires the non-Hermitian skin effect under the interplay of spin-orbit coupling and laser-induced atom loss. The presence of the non-Hermitian skin effect is confirmed through its key signatures in terms of the spectral winding under the periodic boundary condition, the accumulation of eigen wavefunctions at boundaries under an open boundary condition, and bulk dynamics signaled by a directional flow. We show that bulk dynamics, in particular, serves as a convenient signal for experimental detection. The impact of interaction and trapping potentials is also discussed based on the non-Hermitian Gross-Pitaevskii equations. Our work demonstrates that the non-Hermitian skin effect and its rich implications in topology, dynamics, and beyond are well within the reach of current cold-atom experiments. We study a Bose-Einstein condensate of ultracold atoms subject to a non-Hermitian spin-orbit coupling, where the system acquires the non-Hermitian skin effect under the interplay of spin-orbit coupling and laser-induced atom loss. The presence of the non-Hermitian skin effect is confirmed through its key signatures in terms of the spectral winding under the periodic boundary condition, the accumulation of eigen wavefunctions at boundaries under an open boundary condition, and bulk dynamics signaled by a directional flow. We show that bulk dynamics, in particular, serves as a convenient signal for experimental detection. The impact of interaction and trapping potentials is also discussed based on the non-Hermitian Gross-Pitaevskii equations. Our work demonstrates that the non-Hermitian skin effect and its rich implications in topology, dynamics, and beyond are well within the reach of current cold-atom experiments.
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