arXiv subjects

Dan Jiao

Publications and source records attributed to Dan Jiao.

12 recordsLinked to original sources

arXiv2026

Beyond the Purcell Effect: Controlling Pure Quantum Dephasing with Spin Noise Metasurfaces

One central theme in quantum photonics is tailoring the interactions between atoms/spins and their electromagnetic (EM) environments. Considerable effort has focused on engineering spontaneous emission by shaping EM environments, known as the Purcell effect. However, photonic environment control of pure dephasing, which is a complementary paradigm of non-unitary atom/spin couplings with EM environments, remains largely unexplored. Here, we introduce a nanophotonic approach to modify qubit pure dephasing dynamics. Unlike Purcell engineering that tailors photonic environments at qubit resonance frequencies (typically optical/near-infrared), we develop ultra-subwavelength spin noise metasurfaces for efficient broadband control of low-frequency (e.g., $\sim$MHz) photonic environments far off-resonant with atoms/spins for dephasing engineering. We experimentally demonstrate our approach using lithographically defined CoFeB metasurfaces and shallow nitrogen-vacancy (NV) centers in diamond. Instead of modified spontaneous emission, we observe modified NV pure dephasing dynamics near different spin noise metasurfaces. We further isolate metasurface-controlled dephasing from other dephasing mechanisms (e.g., spin bath) by measuring the NV ensemble dephasing noise spectrum with dynamical decoupling spectral decomposition techniques. Our results establish a new frontier in engineering quantum light-matter interactions with nanophotonic structures.

quant-ph↗

arXiv2026

Full-Scale GPU-Accelerated Transient EM-Thermal-Mechanical Co-Simulation for Early-Stage Design of Advanced Packages

In the early-stage design of advanced electronic packages, designers face a critical trade-off between simulation fidelity and computational turnaround time. Conventional early-stage methodologies typically achieve speed by relying on steady-state assumptions and structural homogenization. While computationally efficient, these approximations fundamentally fail to capture dynamic thermal events and stress concentrations at fine-grained internal interfaces, effectively masking failure mechanisms driven by transient signal bursts. In this work, we present a GPU-accelerated transient coupled Electromagnetic-Thermal-Mechanical solver that resolves this bottleneck. The proposed solver enables full-scale, non-homogenized, time-domain simulation of large-scale packages with runtimes amenable for rapid design iteration. Simulation of a NEC SX-Aurora TSUBASA package demonstrates that the tool allows for the identification of signal-induced adiabatic stress that is typically invisible to steady-state and homogenized baselines. This capability brings sign-off level physics fidelity to the early design phase, facilitating the prevention of costly late-stage design failures and broader transient thermal performance degradation risks.

physics.comp-ph↗

arXiv2026

Efficient and Accurate Method for Separating Variant Components from Invariant Background and Component Model Fusion for Fast RFIC Design Space Exploration

The design of RFIC often involves exploring a large number of design variations in an invariant background composed of the processing stack and unchanged circuit blocks. Conventional electromagnetic solvers require a full-domain simulation for every design variation. In this work, we present a fast method that effectively separates the variant components from the invariant background. It algebraically decomposes the total field solution into the contributions from the design-dependent variations and the invariant background. Hence, the field response due to the invariant background can be simulated once and reused for all design variations. Only the variant components need to be simulated at each design variation, the size of which is small. We also develop an efficient way of reusing the model of each component and fusing them accurately to obtain the model of a system composed of many components. The reduced system of variant components involves computing the field solutions in the invariant background due to all possible sources located at variant components, the number of which can be large. We develop a fast algorithm to reduce them to a few field solutions, the number of which is on the order of the layer number. The proposed method has been applied to RFIC design space exploration. Its accuracy, robustness, and efficiency have been demonstrated.

physics.comp-ph↗

arXiv2024

Computational Electromagnetics Meets Spin Qubits: Controlling Noise Effects in Quantum Sensing and Computing

Solid-state spin qubits have emerged as promising platforms for quantum information. Despite extensive efforts in controlling noise in spin qubit quantum applications, one important but less controlled noise source is near-field electromagnetic fluctuations. Low-frequency (MHz and GHz) electromagnetic fluctuations are significantly enhanced near lossy material components in quantum applications, including metallic/superconducting gates necessary for controlling spin qubits in quantum computing devices and materials/nanostructures to be probed in quantum sensing. Although controlling this low-frequency electromagnetic fluctuation noise is crucial for improving the performance of quantum devices, current efforts are hindered by computational challenges. In this paper, we leverage advanced computational electromagnetics techniques, especially fast and accurate volume integral equation based solvers, to overcome the computational obstacle. We introduce a quantum computational electromagnetics framework to control low-frequency magnetic fluctuation noise and enhance spin qubit device performance. Our framework extends the application of computational electromagnetics to spin qubit quantum devices. Furthermore, we demonstrate the application of our framework in realistic quantum devices. Our work paves the way for device engineering to control magnetic fluctuations and improve the performance of spin qubit quantum sensing and computing.

quant-ph↗

arXiv2023

First-Principles Study of Large Gyrotropy in MnBi for Infrared Thermal Photonics

Nonreciprocal gyrotropic materials have attracted significant interest recently in material physics, nanophotonics, and topological physics. Most of the well-known nonreciprocal materials, however, only show nonreciprocity under a strong external magnetic field and within a small segment of the electromagnetic spectrum. Here, through first-principles density functional theory calculations, we show that due to strong spin-orbit coupling manganese-bismuth (MnBi) exhibits nonreciprocity without any external magnetic field and a large gyrotropy in a broadband long-wavelength infrared regime (LWIR). Further, we design a multi-layer structure based on MnBi to obtain a maximum degree of spin-polarized thermal emission at 7 $μ$m. The connection established here between large gyrotropy and the spin-polarized thermal emission points to a potential use of MnBi to develop spin-controlled thermal photonics platforms.

cond-mat.mtrl-sci↗

arXiv2023

Limits to Quantum Gate Fidelity from Near-Field Thermal and Vacuum Fluctuations

High-fidelity quantum gate operations are essential for achieving scalable quantum circuits. In spin qubit quantum computing systems, metallic gates and antennas which are necessary for qubit operation, initialization, and readout, also cause detriments by enhancing fluctuations of electromagnetic fields. Therefore evanescent wave Johnson noise (EWJN) caused by thermal and vacuum fluctuations becomes an important unmitigated noise, which induces the decay of spin qubits and limits the quantum gate operation fidelity. Here, we first develop a quantum electrodynamics theory of EWJN. Then we propose a numerical technique based on volume integral equations to quantify EWJN strength in the vicinity of nanofabricated metallic gates with arbitrary geometry. We study the limits to two spin-qubit gate fidelity from EWJN-induced relaxation processes in two experimentally relevant quantum computing platforms: (a) silicon quantum dot system and (b) NV centers in diamond. Finally, we introduce the Lindbladian engineering method to optimize the control pulse sequence design and show its enhanced performance over Hamiltonian engineering in mitigating the influence of thermal and vacuum fluctuations. Our work leverages advances in computational electromagnetics, fluctuational electrodynamics and open quantum systems to suppress the effects of thermal and vacuum fluctuations and reach the limits of two-spin-qubit gate fidelity.

quant-ph↗

arXiv2023

Observation of Non-Vanishing Optical Helicity in Thermal Radiation from Symmetry-Broken Metasurfaces

Spinning thermal radiation is a unique phenomenon observed in condensed astronomical objects including the Wolf-Rayet star EZ-CMa and the red degenerate star G99-47, due to existence of strong magnetic fields. Here, by designing symmetry-broken metasurfaces, we demonstrate that spinning thermal radiation with a non-vanishing optical helicity can be realized even without applying a magnetic field. We design non-vanishing optical helicity by engineering a dispersionless band which emits omnidirectional spinning thermal radiation, where our design reaches 39% of the fundamental limit. Our results firmly suggest metasurfaces can impart spin coherence in the incoherent radiation excited by thermal fluctuations. The symmetry-based design strategy also provides a general pathway for comprehensively controlling thermal radiation in its temporal and spin coherence.

physics.optics↗

arXiv2022

An A-Phi Formulation Solver in Electromagnetics Based on Discrete Exterior Calculus

An efficient numerical solver for the A-Phi formulation in electromagnetics based on the discrete exterior calculus (DEC) is proposed in this paper. The A-Phi formulation is immune to low-frequency breakdown and ideal for broadband and multi-scale analysis. The generalized Lorenz gauge is used in this paper, which decouples the A equation and the Phi equation. The A-Phi formulation is discretized by using the DEC, which is the discretized version of the exterior calculus in differential geometry. In general, DEC can be viewed as a generalized version of the finite difference method, where Stokes' theorem and Gauss's theorem are naturally preserved. Furthermore, compared with finite difference method, where rectangular grids are applied, DEC can be implemented with unstructured mesh schemes, such as tetrahedral meshes. Thus, the proposed DEC A-Phi solver is inherently stable, free of spurious solutions and can capture highly complex structures efficiently. In this paper, the background knowledge about the A-Phi formulation and DEC is introduced, as well as technical details in implementing the DEC A-Phi solver with different boundary conditions. Numerical examples are provided for validation purposes as well.

cs.CE↗

arXiv2021

Broadband circularly polarized thermal radiation from magnetic Weyl semimetals

We numerically demonstrate that a planar slab made of magnetic Weyl semimetal (a class of topological materials) can emit high-purity circularly polarized (CP) thermal radiation over a broad mid- and long-wave infrared wavelength range for a significant portion of its emission solid angle. This effect fundamentally arises from the strong infrared gyrotropy or nonreciprocity of these materials which primarily depends on the momentum separation between Weyl nodes in the band structure. We clarify the dependence of this effect on the underlying physical parameters and highlight that the spectral bandwidth of CP thermal emission increases with increasing momentum separation between the Weyl nodes. We also demonstrate using recently developed thermal discrete dipole approximation (TDDA) computational method that finite-size bodies of magnetic Weyl semimetals can emit spectrally broadband CP thermal light, albeit over smaller portion of the emission solid angle compared to the planar slabs. Our work identifies unique fundamental and technological prospects of magnetic Weyl semimetals for engineering thermal radiation and designing efficient CP light sources.

physics.optics↗

arXiv2019

Accuracy Controlled Structure-Preserving ${\cal H}^2$-Matrix-Matrix Product in Linear Complexity with Change of Cluster Bases

${\cal H}^2$-matrix constitutes a general mathematical framework for efficient computation of both partial-differential-equation and integral-equation-based operators. Existing linear-complexity ${\cal H}^2$ matrix-matrix product (MMP) algorithm lacks explicit accuracy control, while controlling accuracy without compromising linear complexity is challenging. In this paper, we develop an accuracy controlled ${\cal H}^2$ matrix-matrix product algorithm by instantaneously changing the cluster bases during the matrix product computation based on prescribed accuracy. Meanwhile, we retain the computational complexity of the overall algorithm to be linear. Different from the existing ${\cal H}^2$ matrix-matrix product algorithm where formatted multiplications are performed using the original cluster bases, in the proposed algorithm, all additions and multiplications are either exact or computed based on prescribed accuracy. Furthermore, the original ${\cal H}^2$-matrix structure is preserved in the matrix product. While achieving optimal complexity for constant-rank matrices, the computational complexity of the proposed algorithm is also minimized for variable-rank ${\cal H}^2$-matrices. The proposed work serves as a fundamental arithmetic in the development of fast solvers for large-scale electromagnetic analysis. Applications to both large-scale capacitance extraction and electromagnetic scattering problems involving millions of unknowns on a single core have demonstrated the accuracy and efficiency of the proposed algorithm.

math.NA↗

arXiv2017

Accuracy Directly Controlled Fast Direct Solutions of General ${\cal H}^2$-Matrices and Its Application to Electrically Large Integral-Equation-Based Electromagnetic Analysis

The dense matrix resulting from an integral equation (IE) based solution of Maxwell's equations can be compactly represented by an ${\cal H}^2$-matrix. Given a general dense ${\cal H}^2$-matrix, prevailing fast direct solutions involve approximations whose accuracy can only be indirectly controlled. In this work, we propose new accuracy-controlled direct solution algorithms, including both factorization and inversion, for solving general ${\cal H}^2$-matrices, which does not exist prior to this work. Different from existing direct solutions, where the cluster bases are kept unchanged in the solution procedure thus lacking explicit accuracy control, the proposed new algorithms update the cluster bases and their rank level by level based on prescribed accuracy, without increasing computational complexity. Zeros are also introduced level by level such that the size of the matrix blocks computed at each tree level is the rank at that level, and hence being small. The proposed new direct solution has been applied to solve electrically large volume IEs whose rank linearly grows with electric size. A complexity of $O(NlogN)$ in factorization and inversion time, and a complexity of $O(N)$ in storage and solution time are both theoretically proven and numerically demonstrated. For constant-rank cases, the proposed direct solution has a strict $O(N)$ complexity in both time and memory. Rapid direct solutions of millions of unknowns can be obtained on a single CPU core with directly controlled accuracy.

math.NA↗

arXiv2017

$O(N)$ Iterative and $O(NlogN)$ Fast Direct Volume Integral Equation Solvers with a Minimal-Rank ${\cal H}^2$-Representation for Large-Scale $3$-D Electrodynamic Analysis

Linear complexity iterative and log-linear complexity direct solvers are developed for the volume integral equation (VIE) based general large-scale electrodynamic analysis. The dense VIE system matrix is first represented by a new cluster-based multilevel low-rank representation. In this representation, all the admissible blocks associated with a single cluster are grouped together and represented by a single low-rank block, whose rank is minimized based on prescribed accuracy. From such an initial representation, an efficient algorithm is developed to generate a minimal-rank ${\cal H}^2$-matrix representation. This representation facilitates faster computation, and ensures the same minimal rank's growth rate with electrical size as evaluated from singular value decomposition. Taking into account the rank's growth with electrical size, we develop linear-complexity ${\cal H}^2$-matrix-based storage and matrix-vector multiplication, and thereby an $O(N)$ iterative VIE solver regardless of electrical size. Moreover, we develop an $O(NlogN)$ matrix inversion, and hence a fast $O(NlogN)$ \emph{direct} VIE solver for large-scale electrodynamic analysis. Both theoretical analysis and numerical simulations of large-scale $1$-, $2$- and $3$-D structures on a single-core CPU, resulting in millions of unknowns, have demonstrated the low complexity and superior performance of the proposed VIE electrodynamic solvers. %The algorithms developed in this work are kernel-independent, and hence applicable to other IE operators as well.

math.NA↗