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Origin of the tiny energy gap and Dirac points in monoclinic trilayer nickelate La4Ni3O10

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arXiv 2025年

作者： Zhang, Hu Hebei Research Center of The Basic Discipline for Computational Physics Hebei Key Laboratory of High-precision Computation and Application of Quantum Field Theory College of Physics Science and Technology Hebei University Baoding071002 China

Superconductivity was recently found in trilayer nickelate La4Ni3O10 under high pressure with a phase transition from the monoclinic P21/a structure to the tetragonal I4/mmm structure. Previous experimental works have confirmed the existence of a tiny energy gap formed with Ni 3dz2 orbitals in monoclinic La4Ni3O10. Here we investigate the physical origin of this gap by analyzing symmetry properties of energy bands based on the group theory. The tiny gap comes from energy bands with opposite parity at the Brillouin zone center. In addition, we also find previously unknown Dirac points in some momentum directions around the Fermi level. An effective Hamiltonian is constructed to describe low energy physics of the tiny energy gap and Dirac points. Due to the low crystal symmetry of monoclinic La4Ni3O10, its energy bands display strong anisotropic properties. © 2025, CC BY.

关键词： Hamiltonians

Realization of zero skyrmion Hall angle by elongating skyrmions

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Physical Review B 2025年第13期111卷 134426-134426页

作者： Zhaohua Liu Shuang Li Qiyuan Zhu Xingqiang Shi Ruining Wang Jianglong Wang Hu Zhang Penglai Gong Ruqian Lian Chendong Jin Hebei Research Center of the Basic Discipline for Computational Physics Hebei Key Laboratory of High-precision Computation and Application of Quantum Field Theory College of Physics Science and Technology Hebei University Baoding 071002 People's Republic of China School of Mathematical and Physical Sciences Chongqing University of Science and Technology Chongqing 401331 People's Republic of China

Magnetic skyrmions are considered to be potential information carriers in racetrack memory. However, the skyrmion Hall effect limits the maximum speed of skyrmions along the current direction, which hampers their further application. Here, we investigate the fundamental properties of an elongated skyrmion induced by an anisotropic Dzyaloshinskii-Moriya interaction (DMI). Spin-orbit torque-driven dynamics of the elongated skyrmion under various conditions, including anisotropic DMI, Gilbert damping, and current, are also performed by a combination of micromagnetic simulations and solutions of the Thiele equation. It is found that elongated skyrmions can realize a zero skyrmion Hall angle, and the gradient of Gilbert damping is an effective method to significantly control the skyrmion Hall angle. It should be noted that the rotational symmetry breaking of the elongated skyrmions results in lower thermal stability than the circular skyrmions. Our results offer the possibility of zero skyrmion Hall angle motion, which may help guide the potential application of elongated skyrmions in racetrack memory.

关键词： Anisotropy

A Two-Stage Solution to Quantum Process Tomography: Error Analysis and Optimal Design

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IEEE Transactions on Information Theory 2025年第3期71卷 1803-1823页

作者： Xiao, Shuixin Wang, Yuanlong Zhang, Jun Dong, Daoyi Mooney, Gary J. Petersen, Ian R. Yonezawa, Hidehiro University of New South Wales School of Engineering and Technology CanberraACT2600 Australia University of Michigan-Shanghai Jiao Tong University Joint Institute Shanghai Jiao Tong University Shanghai200240 China The Australian National University School of Engineering CanberraACT2601 Australia Chinese Academy of Sciences Key Laboratory of Systems and Control Academy of Mathematics and Systems Science Beijing100190 China The Australian National University CIICADA Laboratory School of Engineering CanberraACT2601 Australia The University of Melbourne School of Physics ParkvilleVIC3010 Australia RIKEN Center for Quantum Computing Saitama351-0198 Japan Centre for Quantum Computation and Communication Technology Australian Research Council CanberraACT2600 Australia

Quantum process tomography is a critical task for characterizing the dynamics of quantum systems and achieving precise quantum control. In this paper, we propose a two-stage solution for both trace-preserving and non-trace-preserving quantum process tomography. Utilizing a tensor structure, our algorithm exhibits a computational complexity of O(MLd2) where d is the dimension of the quantum system and M, L(M≥ d2, L≥ d2) represent the numbers of different input states and measurement operators, respectively. We establish an analytical error upper bound and then design the optimal input states and the optimal measurement operators, which are both based on minimizing the error upper bound and maximizing the robustness characterized by the condition number. Numerical examples and testing on IBM quantum devices are presented to demonstrate the performance and efficiency of our algorithm. © 1963-2012 IEEE.

关键词： Error analysis

Phase diagrams of neutron-proton superfluid in asymmetric nuclear matter

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Physical Review C 2025年第1期111卷 014320-014320页

作者： K. D. Duan H. B. Zhang X. L. Shang Department of Physics Hebei University Baoding 071002 China CAS Key Laboratory of High Precision Nuclear Spectroscopy Institute of Modern Physics Chinese Academy of Sciences Lanzhou 730000 China School of Nuclear Science and Technology University of Chinese Academy of Sciences Beijing 100049 China Key Laboratory of High-Precision Computation and Application of Quantum Field Theory of Hebei Province Baoding 071002 China

The finite-temperature phase structures for neutron-proton superfluidity in asymmetric nuclear matter are investigated, with a particular focus on the angular dependence of the pairing gap induced by the SD13 nucleon-nucleon interaction. This angular dependence of the pairing gap results in the Cooper pair momentum in the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state exhibiting exactly two distinct stable orientations: one orthogonal (FFLO-ADG-O) and the other parallel (FFLO-ADG-P) to the symmetry axis of the pairing gap. The FFLO-ADG-O state dominates at low asymmetries, while the FFLO-ADG-P state prevails at high asymmetries. Additionally, this analysis of normal-superfluid phase separation reveals that the angular dependence of the pairing gap eliminates phase separation in the low-asymmetry regime, whereas the Cooper pair momentum effectively suppresses phase separation at high asymmetries. These two mechanisms act in concert to significantly prevent the occurrence of normal-superfluid phase separation across the entire phase diagram, ensuring the stability of the homogeneous superfluid state over a broad range of asymmetries. These results provide new insights into the interplay between the angular dependence of the pairing gap and the stability of superfluidity in asymmetric nuclear matter.

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Generalized cross-entropy benchmarking for random circuits with ergodicity

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Chip 2025年第2期4卷

作者： Cheng, Bin Meng, Fei Zhang, Zhi-Jiong Yung, Man-Hong Shenzhen Institute for Quantum Science and Engineering And Department of Physics Southern University of Science and Technology Shenzhen518055 China Centre for Quantum Technologies National University of Singapore Singapore119077 Singapore Centre for Quantum Software and Information Faculty of Engineering and Information Technology University of Technology Sydney NSW2007 Australia Department of Physics City University of Hong Kong Tat Chee Avenue Kowloon999077 Hong Kong QICI Quantum Information and Computation Initiative Department of Computer Science The University of Hong Kong Pokfulam Road 999077 Hong Kong International Quantum Academy Shenzhen518048 China Guangdong Provincial Key Laboratory of Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China Shenzhen Key Laboratory of Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China

Cross-entropy benchmarking is a central technique adopted to certify a quantum chip in recent investigations. To better understand its mathematical foundation and develop new benchmarking schemes, the concept of ergodicity was introduced to random circuit sampling and it was found that the Haar random quantum circuit could satisfy an ergodicity condition—the average of certain types of postprocessing function over the output bit strings is close to the average over the unitary ensemble. For noiseless random circuits, it was proven that the ergodicity holds for polynomials of degree t with positive coefficients when the random circuits form a unitary 2t-design. For strong enough noise, the ergodicity condition is violated, which suggests that ergodicity is a property that can be exploited to certify a quantum chip. The deviation of ergodicity was formulated as a measure for quantum chip benchmarking, and it was demonstrated that it can be used to estimate the circuit fidelity for global depolarizing noise and weakly correlated noise. For a quadratic postprocessing function, our framework recovered Google's result on estimating the circuit fidelity via linear cross-entropy benchmarking (XEB), and we gave a sufficient condition on the noise model characterizing when such estimation is valid. The results establish an interesting connection between ergodicity and noise in random circuits and provide new insights into designing quantum benchmarking schemes. © 2025 The Author(s)

关键词： Quantum electronics

Nuclear Spins in a Solid Exceeding 10-Hour Coherence Times for Ultra-Long-Term Quantum Storage

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PRX Quantum 2025年第1期6卷 010302-010302页

作者： Fudong Wang Miaomiao Ren Weiye Sun Mucheng Guo Matthew J. Sellars Rose L. Ahlefeldt John G. Bartholomew Juan Yao Shuping Liu Shenzhen Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen 518055 China International Quantum Academy and Shenzhen Branch Hefei National Laboratory Shenzhen 518048 China Centre of Excellence for Quantum Computation and Communication Technology Research School of Physics Australian National University Canberra Australian Capital Territory 0200 Australia Centre for Engineered Quantum Systems School of Physics The University of Sydney Sydney New South Wales 2006 Australia The University of Sydney Nano Institute The University of Sydney Sydney New South Wales 2006 Australia

Long-term quantum storage for quantum communication applications will require optically accessible states with coherence times exceeding the desired storage time. Ground-state hyperfine levels in Eu3+:Y2SiO5 have previously shown coherence times as long as 6 h at 1.4 K when operated at a zero-first-order-Zeeman (ZEFOZ) point. Here, we have characterized the limiting decoherence mechanisms acting in this regime, which shows that the coherence time is limited by the presence of spin impurities. This dephasing effect has been suppressed by cooling the sample to 125 mK, resulting in an extension in the coherence time to over 13 h. In the absence of these impurities, the dominant source of dephasing is the field inhomogeneity of the ZEFOZ point arising from the spin inhomogeneous broadening. We have shown that coherence times over 18 h can be achieved by operating using a spectrally narrow subensemble selected from within the inhomogeneous line. The observed coherence time is longer than that of any other system suitable for an optical quantum memory. Furthermore, at a much higher temperature of 6 K, we have realized a 6-h coherence time, which has been obtainable using single-stage cryocoolers. These results imply advanced engineering feasibility in designing and operating future quantum information-storage devices for a wide range of applications, including in satellites.

关键词： Optical recording

Generalized Cross-Entropy Benchmarking for Random Circuits with Ergodicity

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arXiv 2025年

作者： Cheng, Bin Meng, Fei Zhang, Zhi-Jiong Yung, Man-Hong Shenzhen Institute for Quantum Science and Engineering Department of Physics Southern University of Science and Technology Shenzhen518055 China Centre for Quantum Technologies National University of Singapore Singapore Centre for Quantum Software and Information Faculty of Engineering and Information Technology University of Technology SydneyNSW2007 Australia Department of Physics City University of Hong Kong Tat Chee Avenue Kowloon Hong Kong QICI Quantum Information and Computation Initiative Department of Computer Science The University of Hong Kong Pokfulam Road Hong Kong International Quantum Academy Shenzhen518048 China Guangdong Provincial Key Laboratory of Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China Shenzhen Key Laboratory of Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China

Cross-entropy benchmarking is a central technique used to certify a quantum chip in recent experiments. To better understand its mathematical foundation and develop new benchmarking schemes, we introduce the concept of ergodicity to random circuit sampling and find that the Haar random quantum circuit satisfies an ergodicity condition—the average of certain types of post-processing function over the output bit strings is close to the average over the unitary ensemble. For noiseless random circuits, we prove that the ergodicity holds for polynomials of degree t with positive coefficients and when the random circuits form a unitary 2t-design. For strong enough noise, the ergodicity condition is violated. This suggests that ergodicity is a property that can be exploited to certify a quantum chip. We formulate the deviation of ergodicity as a measure for quantum chip benchmarking and show that it can be used to estimate the circuit fidelity for global depolarizing noise and weakly correlated noise. For a quadratic post-processing function, our framework recovers Google’s result on estimating the circuit fidelity via linear cross-entropy benchmarking (XEB), and we give a sufficient condition on the noise model characterizing when such estimation is valid. Our results establish an interesting connection between ergodicity and noise in random circuits and provide new insights into designing quantum benchmarking schemes. Copyright © 2025, The Authors. All rights reserved.

关键词： Quantum electronics

Universal logical operations with a dynamical qubit in Floquet code

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arXiv 2025年

作者： Sun, Xuandong Li, Longcheng Wu, Zhiyi Guo, Zechen Huang, Peisheng Huang, Wenhui Li, Qixian Liang, Yongqi Liu, Yiting Sun, Daxiong Wang, Zilin Xie, Changrong Xiong, Yuzhe Yang, Xiaohan Zhang, Jiajian Zhang, Jiawei Zhang, Libo Zhang, Zihao Guo, Weijie Jiang, Ji Liu, Song Linpeng, Xiayu Niu, Jingjing Qiu, Jiawei Ren, Wenhui Tao, Ziyu Yuan, Yuefeng Zhou, Yuxuan Chu, Ji Zhong, Youpeng Sun, Xiaoming Yu, Dapeng Shenzhen Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China International Quantum Academy Shenzhen518048 China Guangdong Provincial Key Laboratory of Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China Institute of Computing Technology Chinese Academy of Sciences Beijing China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing China School of Physics Peking University Beijing100871 China School of Physics Ningxia University Yinchuan750021 China Shenzhen Branch Hefei National Laboratory Shenzhen518048 China

Quantum error correction (QEC) protects quantum systems against inevitable noises and control inaccuracies, providing a pathway towards fault-tolerant (FT) quantum computation. However, the significant overhead of physical qubits required to encode a single logical qubit poses a major challenge for scalability and practical implementation. Floquet QEC codes, a recent innovation, mitigate this challenge by utilizing time-periodic measurements to introduce additional dynamical logical qubits, thereby enhancing resource efficiency in QEC. Here, we experimentally implement the Floquet-Bacon-Shor code on a superconducting quantum processor. We encode a dynamical logical qubit within a 3 × 3 lattice of data qubits, alongside a conventional static logical qubit. We demonstrate FT encoding and measurement of the two-qubit logical states and stabilize the states using repeated error detection cycles. Additionally, we showcase universal single-qubit logical gates on the dynamical qubit. By implementing a logical CNOT gate, we entangle the dynamical and static logical qubits, generating an error-detected logical Bell state with a fidelity of 75.9%. Our results highlight the potential of Floquet codes for scalable and resource-efficient FT quantum computation. Copyright © 2025, The Authors. All rights reserved.

关键词： Qubits

Basis light-front quantization for the Λb and Σb baryons

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arXiv 2025年

作者： Meng, Lingdi Peng, Tian-Cai Hu, Zhi Xu, Siqi Lan, Jiangshan Mondal, Chandan Wang, Guo-Li Zhao, Xingbo Vary, James P. Department of Physics Hebei University Baoding071002 China Institute of Modern Physics Chinese Academy of Sciences Gansu Lanzhou730000 China School of Physical Science and Technology Lanzhou University Lanzhou730000 China Lanzhou Center for Theoretical Physics Key Laboratory of Theoretical Physics of Gansu Province Lanzhou University Lanzhou730000 China Key Laboratory of Quantum Theory and Applications of MoE Lanzhou University Lanzhou730000 China Research Center for Hadron and CSR Physics Lanzhou University Institute of Modern Physics of CAS Lanzhou730000 China Ibaraki305-0801 Japan School of Nuclear Science and Technology University of Chinese Academy of Sciences Beijing100049 China Department of Physics and Astronomy Iowa State University AmesIA50011 United States Advanced Energy Science and Technology Guangdong Laboratory Guangdong Huizhou516000 China Key Laboratory of High-precision Computation Application of Quantum Field Theory of Hebei Province Baoding China

Within the basis light-front quantization framework, we compute the masses and light-front wave functions of the Λb baryon and its isospin triplet counterparts Σ+b , Σ0b, and Σ−b using a light-front effective Hamiltonian in the leading Fock sector. These wave functions are obtained as eigenstates of the effective Hamiltonian, which incorporates the one-gluon exchange interaction with fixed coupling and a three-dimensional confinement potential. With the quark masses and the couplings as adjustable parameters, the computed masses are set within the experimental range. The resulting predictions for their electromagnetic properties align well with other theoretical calculations. Additionally, the parton distribution functions (PDFs) of these baryons are obtained for the first time, with gluon and sea quark distributions dynamically generated through QCD evolution of the valence quark PDFs. © 2025, CC BY.

关键词： Elementary particles