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Efficient quantum simulation of open quantum dynamics at various Hamiltonians and spectral densities
Na-Na Zhang (张娜娜), Ming-Jie Tao (陶明杰), Wan-Ting He (何宛亭), Xin-Yu Chen (陈鑫宇), Xiang-Yu Kong (孔祥宇), Fu-Guo Deng (邓富国), Neill Lambert, Qing Ai (艾清)
Front. Phys. . 2021, 16 (5 ): 51501-.
https://doi.org/10.1007/s11467-021-1064-y
Simulation of open quantum dynamics for various Hamiltonians and spectral densities are ubiquitous for studying various quantum systems. On a quantum computer, only log2 N qubits are required for the simulation of an N-dimensional quantum system, hence simulation in a quantum computer can greatly reduce the computational complexity compared with classical methods. Recently, a quantum simulation approach was proposed for studying photosynthetic light harvesting [npj Quantum Inf . 4, 52 (2018)]. In this paper, we apply the approach to simulate the open quantum dynamics of various photosynthetic systems. We show that for Drude–Lorentz spectral density, the dimerized geometries with strong couplings within the donor and acceptor clusters respectively exhibit significantly improved efficiency. We also demonstrate that the overall energy transfer can be optimized when the energy gap between the donor and acceptor clusters matches the optimum of the spectral density. The effects of different types of baths, e.g., Ohmic, sub-Ohmic, and super-Ohmic spectral densities are also studied. The present investigations demonstrate that the proposed approach is universal for simulating the exact quantum dynamics of photosynthetic systems.
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Noncyclic nonadiabatic holonomic quantum gates via shortcuts to adiabaticity
Sai Li, Pu Shen, Tao Chen, Zheng-Yuan Xue
Front. Phys. . 2021, 16 (5 ): 51502-.
https://doi.org/10.1007/s11467-021-1087-4
High-fidelity quantum gates are essential for large-scale quantum computation. However, any quantum manipulation will inevitably affected by noises, systematic errors and decoherence effects, which lead to infidelity of a target quantum task. Therefore, implementing high-fidelity, robust and fast quantum gates is highly desired. Here, we propose a fast and robust scheme to construct high-fidelity holonomic quantum gates for universal quantum computation based on resonant interaction of three-level quantum systems via shortcuts to adiabaticity. In our proposal, the target Hamiltonian to induce noncyclic non-Abelian geometric phases can be inversely engineered with less evolution time and demanding experimentally, leading to high-fidelity quantum gates in a simple setup. Besides, our scheme is readily realizable in physical system currently pursued for implementation of quantum computation. Therefore, our proposal represents a promising way towards fault-tolerant geometric quantum computation.
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The relative importance of structure and dynamics on node influence in reversible spreading processes
Jun-Yi Qu, Ming Tang, Ying Liu, Shu-Guang Guan
Front. Phys. . 2021, 16 (5 ): 51503-.
https://doi.org/10.1007/s11467-021-1082-9
The reversible spreading processes with repeated infection widely exist in nature and human society, such as gonorrhea propagation and meme spreading. Identifying influential spreaders is an important issue in the reversible spreading dynamics on complex networks, which has been given much attention. Except for structural centrality, the nodes’ dynamical states play a significant role in their spreading influence in the reversible spreading processes. By integrating the number of outgoing edges and infection risks of node’s neighbors into structural centrality, a new measure for identifying influential spreaders is articulated which considers the relative importance of structure and dynamics on node influence. The number of outgoing edges and infection risks of neighbors represent the positive effect of the local structural characteristic and the negative effect of the dynamical states of nodes in identifying influential spreaders, respectively. We find that an appropriate combination of these two characteristics can greatly improve the accuracy of the proposed measure in identifying the most influential spreaders. Notably, compared with the positive effect of the local structural characteristic, slightly weakening the negative effect of dynamical states of nodes can make the proposed measure play the best performance. Quantitatively understanding the relative importance of structure and dynamics on node influence provides a significant insight into identifying influential nodes in the reversible spreading processes.
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Specific heat ratio effects of compressible Rayleigh–Taylor instability studied by discrete Boltzmann method
Lu Chen (陈璐), Huilin Lai (赖惠林), Chuandong Lin (林传栋), Demei Li (李德梅)
Front. Phys. . 2021, 16 (5 ): 52500-.
https://doi.org/10.1007/s11467-021-1096-3
Rayleigh–Taylor (RT) instability widely exists in nature and engineering fields. How to better understand the physical mechanism of RT instability is of great theoretical significance and practical value. At present, abundant results of RT instability have been obtained by traditional macroscopic methods. However, research on the thermodynamic non-equilibrium (TNE) effects in the process of system evolution is relatively scarce. In this paper, the discrete Boltzmann method based on non-equilibrium statistical physics is utilized to study the effects of the specific heat ratio on compressible RT instability. The evolution process of the compressible RT system with different specific heat ratios can be analyzed by the temperature gradient and the proportion of the non-equilibrium region. Firstly, as a result of the competition between the macroscopic magnitude gradient and the non-equilibrium region, the average TNE intensity first increases and then reduces, and it increases with the specific heat ratio decreasing; the specific heat ratio has the same effect on the global strength of the viscous stress tensor. Secondly, the moment when the total temperature gradient in y direction deviates from the fixed value can be regarded as a physical criterion for judging the formation of the vortex structure. Thirdly, under the competition between the temperature gradients and the contact area of the two fluids, the average intensity of the non-equilibrium quantity related to the heat flux shows diversity, and the influence of the specific heat ratio is also quite remarkable.
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Helicity-dependent time delays in multiphoton ionization by two-color circularly polarized laser fields
Qing-Hua Ke, Yue-Ming Zhou, Yi-Jie Liao, Jin-Tai Liang, Yong Zhao, Jia Tan, Min Li, Pei-Xiang Lu
Front. Phys. . 2021, 16 (5 ): 52503-.
https://doi.org/10.1007/s11467-021-1084-7
By numerically solving the three-dimensional time-dependent Schrödinger equation, we have invest-tigated multiphoton ionization of hydrogen atom in the two-color circularly polarized (TCCP) laser fields consisting of a strong 400 nm and a much weaker 800 nm pulses. Due to the presence of perturb-bative 800 nm laser pulse, sideband peaks emerge between the above-threshold ionization rings in the photoelectron momentum distributions. Our numerical results show that the sideband peaks exhibit one-lobe structure in the co-rotating TCCP laser fields, while it displays the three-lobe structure in the counter-rotating TCCP laser fields. Moreover, the photoelectron yield of sidebands in the co-rotating TCCP fields is much higher than those of the counter-rotating TCCP fields. These phenomena could be well explained from the perspective of the photon-absorption channels via the selection rules. In-terestingly, an obvious phase shift between the sidebands of different orders from the co-rotating and counter-rotating TCCP fields is observed. This shift indicates the helicity-dependent time delay in the one-photon continuum-continuum transition process.
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Designing nonlinear thermal devices and metamaterials under the Fourier law: A route to nonlinear thermotics
Gao-Le Dai
Front. Phys. . 2021, 16 (5 ): 53301-.
https://doi.org/10.1007/s11467-021-1048-y
Nonlinear heat transfer can be exploited to reveal novel transport phenomena and thus enhance people’s ability to manipulate heat flux at will. However, there has not been a mature discipline called nonlinear thermotics like its counterpart in optics or acoustics to make a systematic summary of relevant researches. In the current review, we focus on recent progress in an important part of nonlinear heat transfer, i.e., tailoring nonlinear thermal devices and metamaterials under the Fourier law, especially with temperature-dependent thermal conductivities. We will present the basic designing techniques including solving the equation directly and the transformation theory. Tuning nonlinearity coming from multi-physical effects, and how to calculate effective properties of nonlinear conductive composites using the effective medium theory are also included. Based on these theories, researchers have successfully designed various functional materials and devices such as the thermal diodes, thermal transistors, thermal memory elements, energy-free thermostats, and intelligent thermal materials, and some of them have also been realized in experiments. Further, these phenomenological works can provide a feasible route for the development of nonlinear thermotics.
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Negative thermal expansion: Mechanisms and materials
Erjun Liang, Qiang Sun, Huanli Yuan, Jiaqi Wang, Gaojie Zeng, Qilong Gao
Front. Phys. . 2021, 16 (5 ): 53302-.
https://doi.org/10.1007/s11467-021-1070-0
Negative thermal expansion (NTE) of materials is an intriguing phenomenon challenging the concept of traditional lattice dynamics and of importance for a variety of applications. Progresses in this field develop markedly and update continuously our knowledge on the NTE behavior of materials. In this article, we review the most recent understandings on the underlying mechanisms (anharmonic phonon vibration, magnetovolume effect, ferroelectrorestriction and charge transfer) of thermal shrinkage and the development of NTE materials under each mechanism from both the theoretical and experimental aspects. Besides the low frequency optical phonons which are usually accepted as the origins of NTE in framework structures, NTE driven by acoustic phonons and the interplay between anisotropic elasticity and phonons are stressed. Based on the data documented, some problems affecting applications of NTE materials are discussed and strategies for discovering and design novel framework structured NET materials are also presented.
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Generic spiral spin liquids
Xu-Ping Yao, Jian Qiao Liu, Chun-Jiong Huang, Xiaoqun Wang, Gang Chen
Front. Phys. . 2021, 16 (5 ): 53303-.
https://doi.org/10.1007/s11467-021-1074-9
Spiral spin liquids are unique classical spin liquids that occur in many frustrated spin systems, but do not comprise a new phase of matter. Owing to extensive classical ground-state degeneracy, the spins in a spiral spin liquid thermally fluctuate cooperatively from a collection of spiral configurations at low temperatures. These spiral propagation wavevectors form a continuous manifold in reciprocal space, i.e., a spiral contour or a spiral surface, that strongly governs the low-temperature thermal fluctuations and magnetic physics. In this paper, the relevant spin models conveying the spiral spin liquid physics are systematically explored and the geometric origin of the spiral manifold is clarified in the model construction. The spiral spin liquids based on the dimension and the codimension of the spiral manifold are further clarified. For each class, the physical properties are studied both generally and for specific examples. The results are relevant to a wide range of frustrated magnets. A survey of materials is given and future experiments are suggested.
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BiVO4 /TiO2 heterojunction with rich oxygen vacancies for enhanced electrocatalytic nitrogen reduction reaction
Yunliang Liu, Peiji Deng, Ruqiang Wu, Ramadan A. Geioushy, Yaxi Li, Yixian Liu, Fengling Zhou, Haitao Li, Chenghua Sun
Front. Phys. . 2021, 16 (5 ): 53503-.
https://doi.org/10.1007/s11467-021-1067-8
The large-scale production of ammonia mainly depends on the Haber–Bosch process, which will lead to the problems of high energy consumption and carbon dioxide emission. Electrochemical nitrogen fixation is considered to be an environmental friendly and sustainable process, but its efficiency largely depends on the activity and stability of the catalyst. Therefore, it is imperative to develop highefficient electrocatalysts in the field of nitrogen reduction reaction (NRR). In this paper, we developed a BiVO4 /TiO2 nanotube (BiVO4 /TNT) heterojunction composite with rich oxygen vacancies as an electrocatalytic NRR catalyst. The heterojunction interface and oxygen vacancy of BiVO4 /TNT can be the active site of N2 dynamic activation and proton transition. The synergistic effect of TiO2 and BiVO4 shortens the proton transport path and reduces the over potential of chemical reaction. BiVO4 /TNT has high ammonia yield of 8.54 μg·h−1 ·cm−2 and high Faraday efficiency of 7.70% in −0.8 V vs. RHE in 0.1 M Na2 SO4 solution.
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Toplayer-dependent crystallographic orientation imaging in the bilayer two-dimensional materials with transverse shear microscopy
Sabir Hussain, Rui Xu, Kunqi Xu, Le Lei, Shuya Xing, Jianfeng Guo, Haoyu Dong, Adeel Liaqat, Rashid Iqbal, Muhammad Ahsan Iqbal, Shangzhi Gu, Feiyue Cao, Yan Jun Li, Yasuhiro Sugawara, Fei Pang, Wei Ji, Liming Xie, Shanshan Chen, Zhihai Cheng
Front. Phys. . 2021, 16 (5 ): 53504-.
https://doi.org/10.1007/s11467-021-1072-y
Nanocontact properties of two-dimensional (2D) materials are closely dependent on their unique nanomechanical systems, such as the number of atomic layers and the supporting substrate. Here, we report a direct observation of toplayer-dependent crystallographic orientation imaging of 2D materials with the transverse shear microscopy (TSM). Three typical nanomechanical systems, MoS2 on the amorphous SiO2 /Si, graphene on the amorphous SiO2 /Si, and MoS2 on the crystallized Al2 O3 , have been investigated in detail. This experimental observation reveals that puckering behaviour mainly occurs on the top layer of 2D materials, which is attributed to its direct contact adhesion with the AFM tip. Furthermore, the result of crystallographic orientation imaging of MoS2 /SiO2 /Si and MoS2 /Al2 O3 indicated that the underlying crystalline substrates almost do not contribute to the puckering effect of 2D materials. Our work directly revealed the top layer dependent puckering properties of 2D material, and demonstrate the general applications of TSM in the bilayer 2D systems.
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A DFT study of Ti3 C2 O2 MXenes quantum dots supported on single layer graphene: Electronic structure and hydrogen evolution performance
Qingquan Kong, Xuguang An, Lin Huang, Xiaolian Wang, Wei Feng, Siyao Qiu, Qingyuan Wang, Chenghua Sun
Front. Phys. . 2021, 16 (5 ): 53506-.
https://doi.org/10.1007/s11467-021-1066-9
Heterojunction structure has been extensively employed for the design of novel catalysts. In the present study, density functional theory was utilized to investigate the electronic structure and hydrogen evolution performance of Ti3 C2 O2 MXene quantum dots/graphene (QDs/G) heterostructure. Results show that a slight distortion can be observed in graphene after hybriding with QDs, due to which the electronic structure of QDs have been changed. Associated with such QDs-graphene interaction, the catalytic activity of Ti3 C2 O2 QDs has been optimized, leading to excellent HER catalytic performance.
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Quantum deleting and cloning in a pseudo-unitary system
Yu-Cheng Chen, Ming Gong, Peng Xue, Hai-Dong Yuan, Cheng-Jie Zhang
Front. Phys. . 2021, 16 (5 ): 53601-.
https://doi.org/10.1007/s11467-021-1063-z
In conventional quantum mechanics, quantum no-deleting and no-cloning theorems indicate that two different and nonorthogonal states cannot be perfectly and deterministically deleted and cloned, respectively. Here, we investigate the quantum deleting and cloning in a pseudo-unitary system. We first present a pseudo-Hermitian Hamiltonian with real eigenvalues in a two-qubit system. By using the pseudo-unitary operators generated from this pseudo-Hermitian Hamiltonian, we show that it is possible to delete and clone a class of two different and nonorthogonal states, and it can be generalized to arbitrary two different and nonorthogonal pure qubit states. Furthermore, state discrimination, which is strongly related to quantum no-cloning theorem, is also discussed. Last but not least, we simulate the pseudo-unitary operators in conventional quantum mechanics with post-selection, and obtain the success probability of simulations. Pseudo-unitary operators are implemented with a limited efficiency due to the post-selections. Thus, the success probabilities of deleting and cloning in the simulation by conventional quantum mechanics are less than unity, which maintain the quantum no-deleting and no-cloning theorems.
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18 articles