arXiv subjects

Weng C. Chew

Publications and source records attributed to Weng C. Chew.

8 recordsLinked to original sources

arXiv2026

Full-Wave Green's-Function Modeling of Collective Single-Photon Emission in Non-Markovian Open-System QED with Finite-Bandwidth Compensation of Dispersive Interactions

This work presents a full-wave Green's function framework for modeling collective and coherent single-photon emission from multiple quantum emitters embedded in complex electromagnetic structures. Starting from a transverse modal completeness relation of modified Langevin noise formalism, we derive a closed set of coupled equations for population dynamics and frequency-resolved field amplitudes in the single-excitation regime. Since the electromagnetic reservoir is not traced out at the level of the dynamical amplitudes, the emitted single-photon dynamics can be modeled within the same closed set of equations without Markovian approximation in open and dissipative environments. We demonstrate that finite-bandwidth truncation of the spectral density leads to systematic deviations in coherent dispersive interactions, even when dissipative rates appear converged. To restore causal consistency, we introduce a counter-term compensation scheme that restores the missing dispersive contributions without modifying the retained non-Markovian memory kernel. To validate the scheme and demonstrate the practicality of the proposed framework, we present numerical examples ranging from benchmark configurations to a three-dimensional dispersive ring-resonator structure via finite element method. These capabilities provide a practical route for rigorously incorporating full-wave electromagnetic simulations into non-Markovian multi-emitter quantum electrodynamics, enabling predictive modeling of collective emission, coherent energy exchange, and single-photon radiation in realistic open structures.

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arXiv2025

Atom-Field Non-Markovian Dynamics in Open and Dissipative Systems: An Efficient Memory-Kernel Approach Linked to Dyadic Greens Function and CEM Treatments

In this work, we present a numerical framework for modeling single photon emission from a two level system in open and dissipative systems beyond the Markovian approximation. The method can be readily integrated into standard computational electromagnetic (CEM) solvers such as finite difference time domain (FDTD) and finite element method (FEM). We numerically verify the completeness of boundary and medium assisted modes in the modified Langevin noise formalism by reconstructing the imaginary part of the dyadic Greens function through modal expansion in three dimensions. This reconstruction enables a first principles description of atom field interaction via the multi mode Jaynes Cummings model in open and dissipative environments. Within the single excitation manifold, we show that the memory kernel of a two level system is determined by the imaginary part of the Greens function, implying that radiative modes alone govern the relevant dynamics. The proposed framework thus provides a Greens function based approach for describing atomic population and single photon dynamics, directly compatible with Maxwell solvers. We then present concrete strategies for implementing our method in both FDTD and FEM frameworks, demonstrating its practical applicability. We further verify numerical results for a lossy Lorentz Drude type mirror, including both the case of a TLS near a finite sized metallic mirror and that of a TLS centered in a Fabry Perot cavity. This work establishes a rigorous foundation for incorporating quantum emitter dynamics into computational electromagnetics, thereby extending classical solvers toward quantum light matter interactions.

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arXiv2023

Efficient tensor-network simulation for the few-atom multimode Dicke model via coupling-matrix transformation

We present a novel generalization of the chain mapping technique that applies to multi-atom, multimode systems by making use of coupling matrix transformations. This is extremely useful for tensor network simulations of multimode Dicke model and multi-spin-boson model because their coupling structures are altered from the star form to the chain form with near-neighbor interactions. Our approach produces an equivalent Hamiltonian with the latter coupling form, which we call the band Hamiltonian, and we demonstrate its equivalence to the multimode Dicke Hamiltonian. In the single atom case, our approach reduces to the chain mapping technique. When considering several tens of field modes, we have found that tensor network simulation of two atoms in the ultrastrong coupling regime is possible with our approach. We demonstrate this by considering a pair of entangled atoms confined in a cavity, interacting with thirty electromagnetic modes.

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arXiv2023

Matrix product states and numerical mode decomposition for the analysis of gauge-invariant cavity quantum electrodynamics

There has been a problem of gauge ambiguities with the Rabi Hamiltonian due to the fact that it can be derived from two formally different but physically equivalent fundamental Hamiltonians. This problem has recently been resolved for models with single quantized electromagnetic mode. In this work, we mathematically and numerically verify this for multimode models. With this established, we combine the numerical methods, matrix product states (MPS) and numerical mode decomposition (NMD), for analyzing cavity QED systems. The MPS method is used to efficiently represent and time evolve a quantum state. However, since the coupling structure of the Rabi Hamiltonian is incompatible with MPS, it is numerically transformed into an equivalent Hamiltonian that has a chain coupling structure, which allows efficient application of MPS. The technique of NMD is used to extract the numerical electromagnetic modes of an arbitrary environment. As a proof of concept, this combined approach is demonstrated by analyzing 1D cavity QED systems in various settings.

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arXiv2022

Full-Wave Methodology to Compute the Spontaneous Emission Rate of a Transmon Qubit

The spontaneous emission rate (SER) is an important figure of merit for any quantum bit (qubit), as it can play a significant role in the control and decoherence of the qubit. As a result, accurately characterizing the SER for practical devices is an important step in the design of quantum information processing devices. Here, we specifically focus on the experimentally popular platform of a transmon qubit, which is a kind of superconducting circuit qubit. Despite the importance of understanding the SER of these qubits, it is often determined using approximate circuit models or is inferred from measurements on a fabricated device. To improve the accuracy of predictions in the design process, it is better to use full-wave numerical methods that can make a minimal number of approximations in the description of practical systems. In this work, we show how this can be done with a recently developed field-based description of transmon qubits coupled to an electromagnetic environment. We validate our model by computing the SER for devices similar to those found in the literature that have been well-characterized experimentally. We further cross-validate our results by comparing them to simplified lumped element circuit and transmission line models as appropriate.

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arXiv2021

An Introduction to the Transmon Qubit for Electromagnetic Engineers

One of the most popular approaches being pursued to achieve a quantum advantage with practical hardware are superconducting circuit devices. Although significant progress has been made over the previous two decades, substantial engineering efforts are required to scale these devices so they can be used to solve many problems of interest. Unfortunately, much of this exciting field is described using technical jargon and concepts from physics that are unfamiliar to a classically trained electromagnetic engineer. As a result, this work is often difficult for engineers to become engaged in. We hope to lower the barrier to this field by providing an accessible review of one of the most prevalently used quantum bits (qubits) in superconducting circuit systems, the transmon qubit. Most of the physics of these systems can be understood intuitively with only some background in quantum mechanics. As a result, we avoid invoking quantum mechanical concepts except where it is necessary to ease the transition between details in this work and those that would be encountered in the literature. We believe this leads to a gentler introduction to this fascinating field, and hope that more researchers from the classical electromagnetic community become engaged in this area in the future.

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arXiv2021

Circuit quantum electrodynamics: A new look toward developing full-wave numerical models

Devices built using circuit quantum electrodynamics architectures are one of the most popular approaches currently being pursued to develop quantum information processing hardware. Although significant progress has been made over the previous two decades, there remain many technical issues limiting the performance of fabricated systems. Addressing these issues is made difficult by the absence of rigorous numerical modeling approaches. This work begins to address this issue by providing a new mathematical description of one of the most commonly used circuit quantum electrodynamics systems, a transmon qubit coupled to microwave transmission lines. Expressed in terms of three-dimensional vector fields, our new model is better suited to developing numerical solvers than the circuit element descriptions commonly used in the literature. We present details on the quantization of our new model, and derive quantum equations of motion for the coupled field-transmon system. These results can be used in developing full-wave numerical solvers in the future. To make this work more accessible to the engineering community, we assume only a limited amount of training in quantum physics and provide many background details throughout derivations.

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arXiv2019

Quantum Information Propagation Preserving Computational Electromagnetics

We propose a new methodology, called numerical canonical quantization, to solve quantum Maxwell's equations useful for mathematical modeling of quantum optics physics, and numerical experiments on arbitrary passive and lossless quantum-optical systems. It is based on: (1) the macroscopic (phenomenological) electromagnetic theory on quantum electrodynamics (QED), and (2) concepts borrowed from computational electromagnetics. It was shown that canonical quantization in inhomogeneous dielectric media required definite and proper normal modes. Here, instead of ad-hoc analytic normal modes, we numerically construct complete and time-reversible normal modes in the form of traveling waves to diagonalize the Hamiltonian. Specifically, we directly solve the Helmholtz wave equations for a general linear, reciprocal, isotropic, non-dispersive, and inhomogeneous dielectric media by using either finite-element or finite-difference methods. To convert a scattering problem with infinite number of modes into one with a finite number of modes, we impose Bloch-periodic boundary conditions. This will sparsely sample the normal modes with numerical Bloch-Floquet-like normal modes. Subsequent procedure of numerical canonical quantization is straightforward using linear algebra. We provide relevant numerical recipes in detail and show an important numerical example of indistinguishable two-photon interference in quantum beam splitters, exhibiting Hong-Ou-Mandel effect, which is purely a quantum effect. Also, the present methodology provides a way of numerically investigating existing or new macroscopic QED theories. It will eventually allow quantum-optical numerical experiments of high fidelity to replace many real experiments as in classical electromagnetics.

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