arXiv subjects

M. Qin

Publications and source records attributed to M. Qin.

18 recordsLinked to original sources

arXiv2026

Anomalous mobility edges and extended-localized transition in a quasiperiodic emitter-cavity array

The manipulation of localization in quasiperiodic systems by mobility edges or localization transition holds significant physical importance. In this letter, we demonstrated that the dissipation can induce the emergence of anomalous mobility edges and extended-localized transition in emitter-cavity arrays controlled by quasiperiodic potentials. Specifically, we observe that the localization properties of emitters is governed by the nature of quantum bound states, either discrete or embedded in continuum, providing a unified mechanism linking the emitter-photon bound physics to quasiperiodic criticality. Depending on the bound state discrete or continuumlike, the induced effective excitation hopping exhibits either exponentially decaying or sinusoidally oscillating, giving rise to the formation of localized or critical states, respectively. Through a generalized duality transformation, we analytically determine the anomalous mobility edges and the critical strength of potential, enabling the construction of a full phase diagram. The study reveals that the physical characteristics of cavity exert a significant influence on excitation localization. Therefore, the manipulation of excitation localization can be achieved solely by adjusting the cavity fields.

quant-ph↗

arXiv2026

Do Solar Energetic Electrons cross the Heliospheric Current Sheet? - A Statistical Study

Solar eruptive events such as flares and coronal mass ejection (CME)-driven shocks can release solar energetic particles (SEPs) into the heliosphere. The heliospheric current sheet (HCS) is a large-scale structure that separates regions of opposite magnetic polarity, and its influence on SEP propagation remains poorly understood. We classify SEE events into two groups: same-side events, where both the solar source and spacecraft are in the same magnetic sector, and opposite-side events. The magnetic polarities of the solar source region and the spacecraft location are determined comprehensively based on Potential Field Source Surface (PFSS), magnetic field measurements, the pitch angle distribution of strahl electrons, and the first-order anisotropy of energetic electrons. The spacecraft magnetic polarities determined by footpoint positions at the source surface and in-situ observations are consistent for most events, providing a useful methodological reference for future studies. We identify 60 same-side events and 9 opposite-side events. Our results show that opposite-side events tend to be more isotropic, and that both the solar source and the spacecraft are closer to the HCS than in same-side events. This suggests that particle transport across the HCS is inefficient unless the source or the observer is close to the HCS. These preliminary statistical findings advance our understanding of the role of the HCS in shaping SEP transport.

astro-ph.SR↗

arXiv2026

NGC 1647: A young open cluster with a broad main sequence observed with LAMOST

In this work we present the results of our analysis of medium-resolution LAMOST spectra of candidate members of the cluster NGC 1647 with the aim of determining the stellar parameters, activity level, lithium abundance, and to study the cluster properties. We used the code ROTFIT to determine the atmospheric parameters (Teff, logg, and [Fe/H]), radial velocity (Vr), and projected rotation velocity (vsini) for 158 cluster members. Moreover, for solar-type and cooler stars (Teff< 6500 K), we calculated the H-alpha and LiI-6708 net equivalent width by means of the subtraction of inactive photospheric templates. We determined the rotation periods for 160 stars by analyzing the available TESS photometry. We found four double-lined spectroscopic systems for which we provide the radial velocities of the two components. The Vr distribution of the cluster members peaks at -5.3 km/s with a dispersion of 1.6 km/s, while the average metallicity is [Fe/H]=-0.08$\pm$0.08 dex, in line with previous determinations. From the fitting of the spectral energy distribution of 160 likely members we infer the existence of a differential reddening across the cluster field with an average value of $A_V$=1.1 mag. The $A_V$ values show a distinct correlation with the color offset from the lower boundary of the main sequence; conversely, this offset appears to be uncorrelated with vsini. These two findings confirm that differential reddening is the primary driver behind the observed extended Main-Sequence Turn-Off (eMSTO) in this cluster. The age of NGC 1647, obtained from the lithium abundance, is 203$\pm$27 Myr, which is compatible with the values inferred from a gyrochronological approach and the isochrone fitting.

astro-ph.SR↗

arXiv2024

Quantum Mpemba effect of localization in the dissipative mosaic model

The quantum Mpemba effect in open quantum systems has been extensively studied, but a comprehensive understanding of this phenomenon remains elusive. In this paper, we conduct an analytical investigation of the dissipative dynamics of single excitations in the The mosaic model. Surprisingly, we discover that the presence of an asymptotic mobility edge, denoted as $E_c^{\infty}$, can lead to unique dissipation behavior, serving as a hallmark of the quantum Mpemba effect. Especially, it is found that the energy level $E_c^{\infty}$ exhibits a global periodicity in the real configuration, which acts to inhibit dissipation in the system. Conversely, when the system deviates from $E_c^{\infty}$, the quasidisorder sets in, leading to increased dissipative effects due to the broken of periodicity. Furthermore, we find that the rate of dissipation is closely linked to the localization of the initial state. As a result, the quantum Mpemba effect can be observed clearly by a measure of localization.

quant-ph↗

arXiv2023

Effective Hamiltonian approach to the quantum phase transitions in the extended Jaynes-Cummings model

The study of phase transitions in dissipative quantum systems based on the Liouvillian is often hindered by the difficulty of constructing a time-local master equation when the system-environment coupling is strong. To address this issue, the complex discretization approximation for the environment is proposed to study the quantum phase transition in the extended Jaynes-Cumming model with an infinite number of boson modes. This approach yields a non-Hermitian effective Hamiltonian that can be used to simulate the dynamics of the spin. It is found that the ground state of this effective Hamiltonian determines the spin dynamics in the single-excitation subspace. Depending on the opening of the energy gap and the maximum population of excitations on the spin degree of freedom, three distinct phases can be identified: fast decaying, localized, and stretched dynamics of the spin. This approach can be extended to multiple excitations, and similar dynamics were found in the double-excitation subspace, indicating the robustness of the single-excitation phase.

quant-ph↗

arXiv2023

Effective Hamiltonian approach to the exact dynamics of open system by complex discretization approximation for environment

The discretization approximation method commonly used to simulate the dynamics of quantum system coupled to the environment in continuum often suffers from the periodically partial recovery of initial state because of the effect of finite dimension, dubbed the recurrence. To address this issue, we proposes a generalization of the discretization approximation method into the complex frequency space basing on complex Gauss quadratures. An effective Hamiltonian can be established by this way, which is non-Hermitian and demonstrates the complex energy modes with negative imaginary part, describing the dissipation of the system. This method is applied to examine the dynamics in two exactly solvable models, the dephasing model and the single-excitation dissipative dynamics in the Aubry-Andr\'{e}-Harper model. By comparison with the exact numerics and analytical results, it is found that our approach not only significantly reduces the effect of recurrence and improve the effectiveness of calculation, but also provide a unique perspective into the dynamics of open system from the point of complex energy levels. Furthermore, we establish a simple relationship between the parameters in computation and the effectiveness of simulation by analyzing the computational error.

quant-ph↗

arXiv2022

Energetic electron precipitation driven by electromagnetic ion cyclotron waves from ELFIN's low altitude perspective

We review comprehensive observations of electromagnetic ion cyclotron (EMIC) wave-driven energetic electron precipitation using data from the energetic electron detector on the Electron Losses and Fields InvestigatioN (ELFIN) mission, two polar-orbiting low-altitude spinning CubeSats, measuring 50-5000 keV electrons with good pitch-angle and energy resolution. EMIC wave-driven precipitation exhibits a distinct signature in energy-spectrograms of the precipitating-to-trapped flux ratio: peaks at 0.5 MeV which are abrupt (bursty) with significant substructure (occasionally down to sub-second timescale). Multiple ELFIN passes over the same MLT sector allow us to study the spatial and temporal evolution of the EMIC wave - electron interaction region. Using two years of ELFIN data, we assemble a statistical database of 50 events of strong EMIC wave-driven precipitation. Most reside at L=5-7 at dusk, while a smaller subset exists at L=8-12 at post-midnight. The energies of the peak-precipitation ratio and of the half-peak precipitation ratio (our proxy for the minimum resonance energy) exhibit an L-shell dependence in good agreement with theoretical estimates based on prior statistical observations of EMIC wave power spectra. The precipitation ratio's spectral shape for the most intense events has an exponential falloff away from the peak (i.e., on either side of 1.45 MeV). It too agrees well with quasi-linear diffusion theory based on prior statistics of wave spectra. Sub-MeV electron precipitation observed concurrently with strong EMIC wave-driven 1MeV precipitation has a spectral shape that is consistent with efficient pitch-angle scattering down to 200-300 keV by much less intense higher frequency EMIC waves. These results confirm the critical role of EMIC waves in driving relativistic electron losses. Nonlinear effects may abound and require further investigation.

physics.space-ph↗

arXiv2021

Open dynamics in the Aubry-André-Harper model coupled to a finite bath: the influence of localization in the system and dimensionality of bath

The population evolution of single excitation is studied in the Aubry- André- Harper (AAH) model coupled to a $d (=1,2,3)$-dimensional simple lattices bath with a focus on the effect of localization in the system and the dimensionality of bath. By performing a precise evaluation of time-independent Schrödinger equation, the reduced energy levels of the system can be determined. It is found that the reduce energy levels show significant relevance for the bath dimensions. Subsequently, the time evolution of excitation is studied in both the system and bath. It is found that excitation in the system can decay super-exponentially when $d=1$ or exponentially when $d=2,3$. Regarding the finite nature of bath, the spreading of excitation in the lattices bath is also studied. We find that, depending on the dimensions of bath and the initial state, the spreading of excitation in the bath is diffusive or behaves localization.

quant-ph↗

arXiv2021

Localization-enhanced dissipation in a generalized Aubry-Andr\'{e}-Harper model coupled with Ohmic baths

In this work, the exact dynamics of excitation in the generalized Aubry-Andr\'{e}-Harper model coupled with an Ohmic-type environment is discussed by evaluating the survival probability and inverse participation ratio of the state of system. In contrast to the common belief that localization will preserve the information of the initial state in the system against dissipation into the environment, our study found that strong localization can enhance the dissipation of quantum information instead. By a thorough examination of the dynamics, we show that the coherent transition between the energy state of system is crucial for understanding this unusual behavior. Under this circumstance, the coupling induced energy exchange between the system and its environment can induce the periodic population of excitation on the states of system. As a result, the stable or localization-enhanced decaying of excitation can be observed, dependent on the energy difference between the states of system. This point is verified in further by checking the varying of dynamics of excitation in the system when the coupling between the system and environment is more strong.

quant-ph↗

arXiv2020

Edge state, bound state and anomalous dynamics in the Aubry-André-Haper system coupled to non-Markovian baths

Bound states and their influence on the dynamics of an one-dimensional tight-binding system subject to environments are studied in this paper. We identify specifically three kinds of bound states. The first is a discrete bound state (DBS), of which the energy level exhibits a gap from the continuum. The DBS exhibits the similar features of localization as the edge states in the system and thus can suppress the decay of system. The second is a bound state in the continuum (BIC), which can suppress the system decay too. It is found that the BIC is intimately connected to the edge mode of the system since both of them show almost the same features of localization and energy. The third one displays a large gap from the continuum and behaves extendible (not localized). Moreover the population of the system on this state decays partly but not all of them does. This is different from the two former bound states. The time evolution of a single excitation in the system is studied in order to illustrate the influence of the bound states. We found that both DBS and BIC play an important role in the time evolution, for example, the excitation becomes localized and not decay depending on the overlap between the initial state and the DBS or BIC. Furthermore we observe that the single excitation takes a long-range hopping when the system falls into the regime of strong localizations. This feature can be understood as the interplay of system localizations and the bath-induced long-range correlation.

quant-ph↗

arXiv2017

Enhanced exciton transmission by quantum-jump-based feedback

With rotating-wave approximation (RWA), we show in this paper that exciton transmission in a one-dimensional two-level molecule chain embedded in a cavity can be enhanced or suppressed by strong cavity-chain couplings. This exciton transmission is closely related to the number of molecules and the distribution of molecular exciton energy. In addition, we propose a proposal to enhance the exciton transmission by quantum-jump-based feedback. These results may find applications in experiments of exciton transmission in organic materials.

quant-ph↗

arXiv2017

Optical Schrödinger Cat States in One Mode and two Coupled-Modes Subject to Environments

Taking the decoherence into account, we investigate nonclassical features of the optical Schrödinger cat states in one mode and two coupled-modes systems with two-photon driving. In the one mode system, the relationship between the Schrödinger cat states and the system parameters is derived. We observe that in the presence of single-photon decay the steady states would be a mixture of Schrödinger cats. The dynamics and steady states of such a cat versus single-photon decay are examined. In the two coupled-modes cases with linear and nonlinear couplings, the dynamics of entanglement and mutual information are examined with two different initial states and single-photon decay. Compared to the linear coupling case, more complicated structure appears in the Wigner function in the nonlinear coupling case. The joint quadrature distributions are also explored. Such nonclassical states can be used not only in exploring the boundary between the classical and the quantum worlds but also in quantum metrology and quantum information processing.

quant-ph↗

arXiv2016

Edge state preparation in one dimensional lattice by quantum Lyapunov control

Quantum Lyapunov control uses a feedback control methodology to determine control fields which are applied to control quantum systems in an open-loop way. In this work, we adopt two Lyapunov control schemes to prepare an edge state for a fermionic chain consisted of cold atoms loaded in an optical lattice. Such a chain can be described by the Harper model. Corresponding to the two schemes, state distance and state error Lyapunov functions are considered. The results show that both the schemes are effective to prepare the edge state within a wide range of parameters. We found that the edge state can be prepared with high fidelity even \textbf{if} there are moderate fluctuations in on-site or hopping potentials. Both control schemes can be extended to similar chains (3$m+d$, $d$=2) of different lengths. Since regular amplitude control field is easier to apply in practice, amplitude-modulated control fields are used to replace the unmodulated one to prepare the edge state. Such control approaches provide tools to explore edge states for one dimensional topological materials.

cond-mat.quant-gas↗

arXiv2015

A multi-pathway model for Photosynthetic reaction center

Charge separation in light-harvesting complexes occurs in a pair of tightly coupled chlorophylls at the heart of photosynthetic reaction centers of both plants and bacteria. Recently it has been shown that quantum coherence can, in principle, enhance the efficiency of a solar cell, working like a quantum heat engine (QHE). Here, we propose a biological quantum heat engine (BQHE) motivated by Photosystem {\rm II} reaction center (PS{\rm II} RC) to describe the charge separation. Our model mainly considers two charge-separation pathways more than that in the published literature. The two pathways can interfere via cross-couplings and work together to enhance the charge-separation yields. We explore how these cross-couplings increase the current and voltage of the charge separation and discuss the advantages of multiple pathways in terms of current and power. The robustness of the BQHE against the charge recombination in natural PS{\rm II} RC and dephasing induced by environments is also explored, and extension from two pathways to multiple pathways is made. These results suggest that nature-mimicking architectures with engineered multiple pathways for charge separations might be better for artificial solar energy devices.

physics.bio-ph↗

arXiv2015

Dynamics and quantumness of excitation energy transfer through a complex quantum network

Understanding the mechanisms of efficient and robust energy transfer in organic systems provides us with new insights for the optimal design of artificial systems. In this paper, we explore the dynamics of excitation energy transfer (EET) through a complex quantum network by a toy model consisting of three sites coupled to environments. We study how the coherent evolution and the noise-induced decoherence work together to reach efficient EET and illustrate the role of the phase factor attached to the coupling constant in the EET. By comparing the differences between the Markovian and non-Markovian dynamics, we discuss the effect of environment and the spatial structure of system on the dynamics and the efficiency of EET. A intuitive picture is given to show how the exciton is transferred through the system. Employing the simple model, we show the robustness of EET efficiency under the influence of the environment and elucidate the important role of quantum coherence in EET. We go further to study the quantum feature of the EET dynamics by {\it quantumness} and show the importance of quantum coherence from a new respect. We calculate the energy current in the EET and its quantumness, results for different system parameters are presented and discussed.

physics.chem-ph↗

arXiv2015

Quantum response theory for open systems and its application to Hall conductance

Quantum linear response theory considers only the response of a closed quantum system to a perturbation up to first order in the perturbation. This theory breaks down when the system subjects to environments and the response up to second order in perturbation is not negligible. In this paper, we develop a quantum nonlinear response theory for open systems. We first formulate this theory in terms of general susceptibility, then apply it to deriving the Hall conductance for the open system at finite temperature. Taking the two-band model as an example, we derive the Hall conductance for the two-band model. We calculate the Hall conductance for a two-dimensional ferromagnetic electron gas and a two-dimensional lattice model via different expressions for $d_α(\vec p), \ α=x,y,z$. The results show that the transition points of topological phase almost remain unchanged in the presence of environments.

quant-ph↗

arXiv2014

Exact non-Markovian master equation for a driven damped two-level system

Driven two-level system is a useful model to describe many quantum objects, particularly in quantum information processing. However, the exact master equation for such a system is barely explored. Making use of the Feynman-Vernon influence functional theory, we derive an exact non-Markovian master equation for the driven two-level system and show the lost feature in the perturbative treatment for this system. The perturbative treatment leads to the time-convolutionless (TCL) and the Nakajima-Zwanzig (NZ) master equations. So to this end, we derive the time-convolutionless (TCL) and the Nakajima-Zwanzig (NZ) master equations for the system and compare the dynamics given by the three master equations. We find the validity condition for the TCL and NZ master equations. Based on the exact non-Markovian master equation, we analyze the regime of validity for the secular approximation in the time-convolutionless master equation and discuss the leading corrections of the nonsecular terms to the quantum dynamics, significant effects are found in the dynamics of the driven system.

quant-ph↗

arXiv2014

Single-Photon Storing in Coupled Non-Markovian Atom-Cavity System

Taking the non-Markovian effect into account, we study how to store a single photon of arbitrary temporal shape in a single atom coupled to an optical cavity. Our model applies to Raman transitions in three-level atoms with one branch of the transition controlled by a driving pulse, and the other coupled to the cavity. For any couplings of input field to the optical cavity and detunings of the atom from the driving pulse and cavity, we extend the input-output relation from Markovian dynamics to non-Markovian one. For most possible photon shapes, we derive an analytic expression for the driving pulse in order to completely map the input photon into the atom. We find that, the amplitude of the driving pulse depends only on the detuning of the atom from the frequency of the cavity, i.e., the detuning of the atom to the driving pulse has no effect on the strength of the driving pulse.

quant-ph↗