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Maxwell Demon and Einstein–Podolsky–Rosen Steering
Meng-Jun Hu, Xiao-Min Hu, and Yong-Sheng Zhang
Chin. Phys. Lett. 2024, 41 (5):
050302
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DOI: 10.1088/0256-307X/41/5/050302
Research of Maxwell demon and quantum entanglement is important because of its foundational significance in physics and its potential applications in quantum information. Previous studies on the Maxwell demon have primarily focused on thermodynamics, taking into account quantum correlations. Here we consider from another perspective and ask whether quantum non-locality correlations can be simulated by performing work. The Maxwell demon-assisted Einstein–Podolsky–Rosen (EPR) steering is thus proposed, which implies a new type of loophole. The application of Landauer's erasure principle suggests that the only way to close this loophole during a steering task is by continuously monitoring the heat fluctuation of the local environment by the participant. We construct a quantum circuit model of Maxwell demon-assisted EPR steering, which can be demonstrated by current programmable quantum processors, such as superconducting quantum computers. Based on this quantum circuit model, we obtain a quantitative formula describing the relationship between energy dissipation due to the work of the demon and quantum non-locality correlation. The result is of great physical interest because it provides a new way to explore and understand the relationship between quantum non-locality, information, and thermodynamics.
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Random Green's Function Method for Large-Scale Electronic Structure Calculation
Mingfa Tang, Chang Liu, Aixia Zhang, Qingyun Zhang, Jiayu Zhai, Shengjun Yuan, and Youqi Ke
Chin. Phys. Lett. 2024, 41 (5):
053102
.
DOI: 10.1088/0256-307X/41/5/053102
We report a linear-scaling random Green's function (rGF) method for large-scale electronic structure calculation. In this method, the rGF is defined on a set of random states and is efficiently calculated by projecting onto Krylov subspace. With the rGF method, the Fermi–Dirac operator can be obtained directly, avoiding the polynomial expansion to Fermi–Dirac function. To demonstrate the applicability, we implement the rGF method with the density-functional tight-binding method. It is shown that the Krylov subspace can maintain at small size for materials with different gaps at zero temperature, including H$_{2}$O and Si clusters. We find with a simple deflation technique that the rGF self-consistent calculation of H$_{2}$O clusters at $T=0$ K can reach an error of $\sim$ $1$ meV per H$_{2}$O molecule in total energy, compared to deterministic calculations. The rGF method provides an effective stochastic method for large-scale electronic structure simulation.
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Three-Channel Interference Interpretation of Fano Profile
Bo Li, Tian-Jun Li, Zi-Ru Ma, Xi-Yuan Wang, Xin-Chao Huang, and Lin-Fan Zhu
Chin. Phys. Lett. 2024, 41 (5):
053201
.
DOI: 10.1088/0256-307X/41/5/053201
Fano resonance is a ubiquitous phenomenon, and it is commonly interpreted as a two-channel interference of the discrete and continuous channels. The present work investigates the Fano profile from a perspective of the temporal evolution of the wave function. By exciting the atom with a $\delta$ pulse and calculating the evolution of the wave function, the Fano formula is deduced. The results clearly show that the Fano resonance is of a three-channel interference, which is different from the traditional understanding. The three channels are revealed as the ground-continuum, ground-discrete-continuum, and a previously unmentioned third channel, i.e., ground-continuum-discrete-continuum. The present three-channel interpretation can be easily generalized to other physical systems, contributing to a deeper understanding of the Fano profile.
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Experimental Investigations of Quasi-Coherent Micro-Instabilities in J-TEXT Ohmic Plasmas
Peng Shi, G. Zhuang, Zhifeng Cheng, Li Gao, Yinan Zhou, Yong Liu, J. T. Luo, and Jingchun Li
Chin. Phys. Lett. 2024, 41 (5):
055201
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DOI: 10.1088/0256-307X/41/5/055201
Quasi-coherent micro-instabilities is one of the key topics of magnetic confinement fusion. This work focuses on the quasi-coherent spectra of ion temperature gradient (ITG) and trapped-electron-mode instabilities using newly developed far-forward collective scattering measurements within ohmic plasmas in the J-TEXT tokamak. The ITG mode is characterized by frequencies ranging from 30 to 100 kHz and wavenumbers ($k_{\theta}\rho_{\rm s})$ less than 0.3. Beyond a critical plasma density threshold, the ITG mode undergoes a bifurcation, which is marked by a reduction in frequency and an enhancement in amplitude. Concurrently, enhancements in ion energy loss and degradation in confinement are observed. This ground-breaking discovery represents the first instance of direct experimental evidence that establishes a clear link between ITG instability and ion thermal transport.
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Influence of High-Pressure Induced Lattice Dislocations and Distortions on Thermoelectric Performance of Pristine SnTe
Bowen Zheng, Tao Chen, Hairui Sun, Manman Yang, Bingchao Yang, Xin Chen, Yongsheng Zhang, and Xiaobing Liu
Chin. Phys. Lett. 2024, 41 (5):
057301
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DOI: 10.1088/0256-307X/41/5/057301
As a sister compound of PbTe, SnTe possesses the environmentally friendly elements. However, the pristine SnTe compounds suffer from the high carrier concentration, the large valence band offset between the $L$ and $\varSigma $ positions and high thermal conductivity. Using high-pressure and high-temperature technology, we synthesized the pristine SnTe samples at different pressures and systemically investigated their thermoelectric properties. High pressure induces rich microstructures, including the high-density dislocations and lattice distortions, which serve as the strong phonon scattering centers, thereby reducing the lattice thermal conductivity. For the electrical properties, pressure reduces the harmful high carrier concentration, due to the depression of Sn vacancies. Moreover, pressure induces the valence band convergence, reducing the energy separation between the $L$ and $\varSigma $ positions. The band convergence and suppressed carrier concentration increase the Seebeck coefficient. Thus, the power factors of pressure-sintered compounds do not deteriorate significantly under the condition of decreasing electrical conductivity. Ultimately, for a pristine SnTe compound synthesized at 5 GPa, a higher $ZT$ value of 0.51 is achieved at 750 K, representing a 140% improvement compared to the value of 0.21 obtained using SPS. Therefore, the high-pressure and high-temperature technology is demonstrated as an effectively approach to optimize thermoelectric performance.
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Interlayer Magnetic Interaction in the CrI$_3$/CrSe$_2$ Heterostructure
Qiu-Hao Wang, Mei-Yan Ni, Shu-Jing Li, Fa-Wei Zheng, Hong-Yan Lu, and Ping Zhang
Chin. Phys. Lett. 2024, 41 (5):
057401
.
DOI: 10.1088/0256-307X/41/5/057401
Based on first-principles calculations, we systematically study the stacking energy and interlayer magnetic interaction of the heterobilayer composed of CrI$_3$ and CrSe$_2$ monolayers. It is found that the stacking order plays a crucial role in the interlayer magnetic coupling. Among all possible stacking structures, the AA-stacking is the most stable heterostructure, exhibiting interlayer antiferromagnetic interactions. Interestingly, the interlayer magnetic interaction can be effectively tuned by biaxial strain. A 4.3% compressive strain would result in a ferromagnetic interlayer interaction in all stacking orders. These results reveal the magnetic properties of CrI$_3$/CrSe$_2$ heterostructure, which is expected to be applied to spintronic devices.
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Mott Gap Filling by Doping Electrons through Depositing One Sub-Monolayer Thin Film of Rb on Ca$_{2}$CuO$_{2}$Cl$_{2}$
Han Li, Zhaohui Wang, Shengtai Fan, Huazhou Li, Huan Yang, and Haihu Wen
Chin. Phys. Lett. 2024, 41 (5):
057402
.
DOI: 10.1088/0256-307X/41/5/057402
Understanding the doping evolution from a Mott insulator to a superconductor probably holds the key to resolve the mystery of unconventional superconductivity in copper oxides. To elucidate the evolution of the electronic state starting from the Mott insulator, we dose the surface of the parent phase Ca$_{2}$CuO$_{2}$Cl$_{2}$ by depositing Rb atoms, which are supposed to donate electrons to the CuO$_{2}$ planes underneath. We successfully achieved the Rb sub-monolayer thin films in forming the square lattice. The scanning tunneling microscopy or spectroscopy measurements on the surface show that the Fermi energy is pinned within the Mott gap but close to the edge of the charge transfer band. In addition, an in-gap state appears at the bottom of the upper Hubbard band (UHB), and the Mott gap will be significantly diminished. Combined with the Cl defect and the Rb adatom/cluster results, the electron doping is likely to increase the spectra weight of the UHB for the double occupancy. Our results provide information to understand the electron doping to the parent compound of cuprates.
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The Combined Effect of Spin-Transfer Torque and Voltage-Controlled Strain Gradient on Magnetic Domain-Wall Dynamics: Toward Tunable Spintronic Neuron
Guo-Liang Yu, Xin-Yan He, Sheng-Bin Shi, Yang Qiu, Ming-Min Zhu, Jia-Wei Wang, Yan Li, Yuan-Xun Li, Jie Wang, and Hao-Miao Zhou
Chin. Phys. Lett. 2024, 41 (5):
057502
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DOI: 10.1088/0256-307X/41/5/057502
Magnetic domain wall (DW), as one of the promising information carriers in spintronic devices, have been widely investigated owing to its nonlinear dynamics and tunable properties. Here, we theoretically and numerically demonstrate the DW dynamics driven by the synergistic interaction between current-induced spin-transfer torque (STT) and voltage-controlled strain gradient (VCSG) in multiferroic heterostructures. Through electromechanical and micromagnetic simulations, we show that a desirable strain gradient can be created and it further modulates the equilibrium position and velocity of the current-driven DW motion. Meanwhile, an analytical Thiele's model is developed to describe the steady motion of DW and the analytical results are quite consistent with the simulation data. Finally, we find that this combination effect can be leveraged to design DW-based biological neurons where the synergistic interaction between STT and VCSG-driven DW motion as integrating and leaking motivates mimicking leaky-integrate-and-fire (LIF) and self-reset function. Importantly, the firing response of the LIF neuron can be efficiently modulated, facilitating the exploration of tunable activation function generators, which can further help improve the computational capability of the neuromorphic system.
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Cosmology-Independent Photon Mass Limits from Localized Fast Radio Bursts by Using Artificial Neural Networks
Jing-Yu Ran, Bao Wang, and Jun-Jie Wei
Chin. Phys. Lett. 2024, 41 (5):
059501
.
DOI: 10.1088/0256-307X/41/5/059501
A hypothetical photon mass $m_{\gamma}$ can produce a frequency-dependent vacuum dispersion of light, which leads to an additional time delay between photons with different frequencies when they propagate through a fixed distance. The dispersion measure and redshift measurements of fast radio bursts (FRBs) have been widely used to constrain the rest mass of the photon. However, all current studies analyzed the effect of the frequency-dependent dispersion for massive photons in the standard $\Lambda$CDM cosmological context. In order to alleviate the circularity problem induced by the presumption of a specific cosmological model based on the fundamental postulate of the masslessness of photons, here we employ a new model-independent smoothing technique, artificial neural network (ANN), to reconstruct the Hubble parameter $H(z)$ function from 34 cosmic-chronometer measurements. By combining observations of 32 well-localized FRBs and the $H(z)$ function reconstructed by ANN, we obtain an upper limit of $m_{\gamma} \le 3.5 \times 10^{-51}$ kg, or equivalently $m_{\gamma}\le2.0 \times 10^{-15}$ eV/c$^2$ ($m_{\gamma} \le 6.5 \times 10^{-51}$ kg, or equivalently $m_{\gamma} \le 3.6 \times 10^{-15}$ eV/c$^2$) at the $1\sigma$ ($2\sigma$) confidence level. This is the first cosmology-independent photon mass limit derived from extragalactic sources.
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13 articles
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