arXiv subjects

Cheng Shang

Publications and source records attributed to Cheng Shang.

24 records · Page 2Linked to original sources

arXiv2025

Nonreciprocal quantum router with non-Markovian environments

Quantum routers are essential elements of quantum networks, enabling coherent information transfer between distant nodes. While their behavior has been extensively studied under Markovian approximations, investigations in non-Markovian regimes remain limited. In this paper, we study a nonreciprocal quantum router embedded in non-Markovian environments, enabling directional control of single photons, which allows transmission from one side while blocking it from the other. The cascade system under study consists of two quantum nodes: one comprising two coupled coplanar-waveguide resonators and the other featuring a superconducting ring resonator. Each node is respectively coupled to a single Yttrium iron garnet (YIG) disk, with nonreciprocity arising from the selective coupling between magnons and microwave photons in our model. We analytically derive the transmission and reflection spectra of the system when a photon is input respectively from the left and right sides of the transmission line in the non-Markovian regimes. Our results demonstrate that, with appropriate parameters, a single photon can be routed from a given input port to either of the two output ports, while being fully absorbed when incident from the opposite side. We further compare the scattering behavior in non-Markovian and Markovian regimes through numerical simulations. In the non-Markovian case, the transmission spectrum exhibits two unity peaks (two valleys with a minimum value of zero), whereas in the Markovian case, high transmission appears only within a narrow window near zero detuning when the photon is injected from the left. As the environmental bandwidth increases, non-Markovian results converge to the Markovian limit. This formalism may enable new applications in quantum information and communication exploiting non-Markovianity.

physics.optics↗

arXiv2025

Manipulating spectral transitions and photonic transmission in a non-Hermitian optical system through nanoparticle perturbations

In recent years, extensive research has been dedicated to the study of parity-time ($\mathcal{PT}$) symmetry, which involves the engineered balance of gain and loss in non-Hermitian optics. Complementary to $\mathcal{PT}$ symmetry, the concept of anti-$\mathcal{PT}$ symmetry has emerged as a natural framework for describing the dynamics of open systems with dissipations. In this work, we study spectral transitions and photon transmission in a linear spinning resonator perturbed by nanoparticles. First, we show that by precisely controlling the nanoparticle perturbations, the eigenvalues (or spectra) of a non-Hermitian system satisfying anti-$\mathcal{PT}$ symmetry can transit to that of a quasi-closed Hermitian system. Second, we outline the essential conditions for constructing a quasi-closed system and analyze its dynamic behavior with respect to photon transmission. By adjusting the rotational angular velocity of the spinning resonator and the strength of the nanoparticle perturbations, the quasi-closed system enables a variety of photon distribution behaviors, which may have significant applications in quantum devices. Our findings offer valuable insights for the design of dissipative quantum devices under realistic conditions and for understanding their responses to external perturbations.

physics.optics↗

arXiv2023

Resonance-dominant optomechanical entanglement in open quantum systems

Motivated by entanglement protection, our work utilizes a resonance effect to enhance optomechanical entanglement in the coherent-state representation. We propose a filtering model to filter out the significant detuning components between a thermal-mechanical mode and its surrounding heat baths in the weak coupling limit. We reveal that protecting continuous-variable entanglement involves the elimination of degrees of freedom associated with significant detuning components, thereby resisting decoherence. We construct a nonlinear Langevin equation of the filtering model and numerically show that the filtering model doubles the robustness of the stationary maximum optomechanical entanglement to the thermal fluctuation noise and mechanical damping. Furthermore, we generalize these results to an optical cavity array with one oscillating end-mirror to investigate the long-distance optimal optomechanical entanglement transfer. Our study breaks new ground for applying the resonance effect to protect quantum systems from decoherence and advancing the possibilities of large-scale quantum information processing and quantum network construction.

quant-ph↗

arXiv2023

Analytical approach to higher-order correlation functions in U(1) symmetric systems

We derive a compact analytical solution of the $n$th-order equal-time correlation functions by using scattering matrix ($S$ matrix) under a weak coherent state input. Our solution applies to any dissipative quantum system that respects the U(1) symmetry. We further extend our analytical solution into two categories depending on whether the input and output channels are identical. The first category provides a different path for studying cross-correlation and multiple-drive cases, while the second category is instrumental in studying waveguide quantum electrodynamics systems. Our analytical solution allows for easy investigation of the statistical properties of multiple photons even in complex systems. Furthermore, we have developed a user-friendly open-source library in Python known as the quantum correlation solver, and this tool provides a convenient means to study various dissipative quantum systems that satisfy the above-mentioned criteria. Our study enables using $S$ matrix to study the photonic correlation and advance the possibilities for exploring complex systems.

quant-ph↗

arXiv2022

Origin of performance degradation in high-delithiation Li$_x$CoO$_2$: insights from direct atomic simulations using global neural network potentials

Li$_x$CoO$_2$ based batteries have serious capacity degradation and safety issues when cycling at high-delithiation states but full and consistent mechanisms are still poorly understood. Herein, a global neural network potential (GNNP) is developed to provide direct theoretical understandings by performing long-time and large-size atomic simulations. We propose a self-consistent picture as follows: (i) CoO$_2$ layers are easier to glide with longer distances at more highly delithiated states, resulting in structural transitions and structural inhomogeneity; (ii) at regions between different phases with different Li distributions due to gliding, local strains are induced and accumulate during cycling processes; (3) accumulated strains cause the rupture of Li diffusion channels and result in formation of oxygen dimers during cycling especially when Li has inhomogeneous distributions, leading to capacity degradations and safety issues. We find that large tensile strains combined with inhomogeneous distributions of Li ions play critical roles in the formation processes of blocked Li diffusion channels and the oxygen dimers at high-delithiation states, which could be the fundamental origins of capacity degradations and safety issues. Correspondingly, suppressing accumulations of strains by controlling charge and discharge conditions as well as suppressing the gliding will be helpful for improving the performance of lithium-ion batteries (LIBs).

physics.comp-ph↗

arXiv2018

Single photon transmission in strong three-mode optomechanical circulatory system

In the few-photon regime, we theoretically propose a feasible scheme to realize strong coupling optomechanical cycle in a three-mode optomechanical circulatory system (OMCS) comprising of cross-Kerr (CK) type and linear coupling between the corresponding two bosonic modes, meanwhile, where one of the bosonic modes is strongly coherently driven and the rest are weakly driven. A Langevin equation for strong three-mode OMCS is derived by adjusting the parameters of the appropriate strong coherent laser. We show that this strong coupling of optomechanical originates from the strong coherently driven the CK coupling modes, thereby, in coherent state displacement representation enhance the optomechanical coupling and present the strengthen of the nonolinearity. We obtain a set of optimal parameters by full numerical simulation of dynamics matrix, under this condition, minimal strong OMCS that exhibit a single photon perfect non-reciprocal transmission between the two optical modes, and unidirectional transportation inter the optomechanical modes. For a detection field, the system presents optomechanical induced transparency (OMIT) behavior. The presented results can be widely applied to quantum devices such as circulators, diodes, and transistors. Moreover, we brief analysis that a system which consisting of dual mechanical modes and one optical mode, further extend the system to a generalized coupled one-dimensional optomechanical array and arbitrary modes optomechanical loop network. Experimentally, the system has been demonstrated to be achieved through a variety of experimental protocols and configurations, for example optomechanical crystal and integrated quantum superconducting circuit.

quant-ph↗