arXiv subjects

Yijun Xie

Publications and source records attributed to Yijun Xie.

7 recordsLinked to original sources

arXiv2025

Snowpark: Performant, Secure, User-Friendly Data Engineering and AI/ML Next To Your Data

Snowflake revolutionized data analytics with an elastic architecture that decouples compute and storage, enabling scalable solutions supporting data architectures like data lake, data warehouse, data lakehouse, and data mesh. Building on this foundation, Snowflake has advanced its AI Data Cloud vision by introducing Snowpark, a managed turnkey solution that supports data engineering and AI and ML workloads using Python and other programming languages. This paper outlines Snowpark's design objectives towards high performance, strong security and governance, and ease of use. We detail the architecture of Snowpark, highlighting its elastic scalability and seamless integration with Snowflake core compute infrastructure. This includes leveraging Snowflake control plane for distributed computing and employing a secure sandbox for isolating Snowflake SQL workloads from Snowpark executions. Additionally, we present core innovations in Snowpark that drive further performance enhancements, such as query initialization latency reduction through Python package caching, improved workload scheduling for customized workloads, and data skew management via efficient row redistribution. Finally, we showcase real-world case studies that illustrate Snowpark's efficiency and effectiveness for large-scale data engineering and AI and ML tasks.

cs.DC↗

arXiv2024

Development of a Monte Carlo tool for simulating electron transport in noble liquids

This study presents a Monte Carlo simulation tool for modeling the transportation processes of thermal electrons in noble liquids, specifically focusing on liquid argon and liquid xenon. The study aims to elucidate the microscopical mechanisms governing the drift and diffusion of electrons within the context of time projection chambers (TPCs), with detailed considerations of coherent electron-atom scattering and electric field force. The simulation tool is implemented in the Geant4 framework, allowing for the exploration of electron transport parameters, including drift velocity, longitudinal diffusion coefficient, and transverse diffusion coefficient. The simulation is validated by comparing its results for drift velocity and diffusion coefficients with experimental measurements, revealing good agreement in the low to moderate electric field ranges. Discrepancies in high electric field regions are discussed, highlighting the impact of impurities and the need for improved cross-section calculations. Despite some limitations, the simulation tool provides valuable insights into electron transport in noble liquids, offering a foundation for future enhancements and applications in diverse research areas.

hep-ex↗

arXiv2023

Inverse-designed broadband low-loss grating coupler on thick lithium-niobate-on-insulator platform

A grating coupler on 700-nm-thick Z-cut lithium-niobate-on-insulator platform with high coupling efficiency, large bandwidth, and high fabrication tolerance is designed and optimized by inverse design method. The optimized grating coupler is fabricated with a single set of e-beam lithography and etching process, and it is experimentally characterized to possess peak coupling efficiency of -3.8 dB at 1574.93 nm, 1-dB bandwidth of 71.7 nm, and 3-dB bandwidth of over 120 nm.

physics.optics↗

arXiv2022

Photonic frequency microcombs based on dissipative Kerr and quadratic cavity solitons

Optical frequency comb, with precisely controlled spectral lines spanning a broad range, has been the key enabling technology for many scientific breakthroughs. In addition to the traditional implementation based on modelocked lasers, photonic frequency microcombs based on dissipative Kerr and quadratic cavity solitons in high-Q microresonators have become invaluable in applications requiring compact footprint, low cost, good energy efficiency, large comb spacing, and access to nonconventional spectral regions. In this review, we comprehensively examine the recent progress of photonic frequency microcombs and discuss how various phenomena can be utilized to enhance the microcomb performances that benefit a plethora of applications including optical atomic clockwork, optical frequency synthesizer, precision spectroscopy, astrospectrograph calibration, biomedical imaging, optical communications, coherent ranging, and quantum information science.

physics.optics↗

arXiv2022

Dissipative soliton generation and real-time dynamics in microresonator-filtered fiber lasers

Optical frequency combs in microresonators (microcombs) have a wide range of applications in science and technology, due to its compact size and access to considerably larger comb spacing. Despite recent successes, the problems of self-starting, high mode efficiency as well as high output power have not been fully addressed for conventional soliton microcombs. Recent demonstration of laser cavity soliton microcombs by nesting a microresonator into a fiber cavity, shows great potential to solve the problems. Here we comprehensively study the dissipative soliton generation and interaction dynamics in a microresonator-filtered fiber laser in both theory and experiment. We first bring theoretical insight into the mode-locking principle, discuss the parameters effect on soliton properties and provide experimental guidelines for broadband soliton generation. We predict chirped bright dissipative soliton with flat-top spectral envelope in microresonators with normal dispersion, which is fundamentally infeasible for externally driven case. Furthermore, we experimentally achieve soliton microcombs with large bandwidth of ~10 nm and high mode efficiency of 90.7%. Finally, by taking advantage of an ultrahigh-speed time magnifier, we study the real-time soliton formation and interaction dynamics and experimentally observe soliton Newton's cradle. Our study will benefit the design of the novel, high-efficiency and self-starting microcombs for real-world applications.

physics.optics↗

arXiv2022

Spatiotemporal mode-locking and photonic flywheel in multimode microresonators

Dissipative Kerr soliton (DKS) frequency combs - also known as microcombs - have arguably created a new field in cavity nonlinear photonics, with a strong cross-fertilization between theoretical, experimental, and technological research. Spatiotemporal mode-locking (STML) not only add new degrees of freedom to ultrafast laser technology, but also provide new insights for implementing analogue computers and heuristic optimizers with photonics. Here, we combine the principles of DKS and STML for the first time to demonstrate the STML DKS by developing an unexplored ultrahigh-quality-factor Fabry-Perot microresonator based on graded index multimode fiber (GRIN-MMF). Using the intermodal stimulated Brillouin scattering, we can selectively excite either the eigenmode DKS or the STML DKS. Furthermore, we demonstrate an ultralow noise microcomb that enhances the photonic flywheel performance in both the fundamental comb linewidth and DKS timing jitter. The demonstrated fundamental comb linewidth of 400 mHz and DKS timing jitter of 500 attosecond represent improvements of 25x and 2.5x, respectively, from the state-of-the-art. Our results show the potential of GRIN-MMF FP microresonators as an ideal testbed for high-dimensional nonlinear cavity dynamics and photonic flywheel with ultrahigh coherence and ultralow timing jitter.

physics.optics↗

arXiv2021

Time-magnified photon counting with a 550fs resolution

Time-resolved photon-counting plays an indispensable role in precision metrology in both classical and quantum regimes. In particular, time-correlated single-photon counting (TCSPC) has been the key enabling technology for applications such as low-light fluorescence lifetime spectroscopy and photon counting time-of-flight (ToF) 3D imaging. However, state-of-the-art TCSPC single-photon timing resolution (SPTR) is limited in the range of 10-100 ps by the available single-photon detector technology. In this paper, we experimentally demonstrate a time-magnified TCSPC (TM-TCSPC) that achieves an unprecedentedly short SPTR of 550 fs for the first time with an off-the-shelf single-photon detector. The TM-TCSPC can resolve ultrashort pulses with a 130-fs pulsewidth difference at a 22-fs accuracy. When applied to photon counting ToF 3D imaging, the TM-TCSPC greatly suppresses the range walk error that limits all photon counting ToF 3D imaging systems by 99.2 % (130 times) and thus provides unprecedentedly high depth measurement accuracy and precision of 26 μm and 3 μm, respectively.

physics.optics↗