About

I am an incoming fifth-year Ph.D. candidate at Penn State University, advised by Prof. Necdet Serhat Aybat. Before joining Penn State University, I obtained my Bachelor’s degree in Mathematics from Lanzhou University. Previously, I was a research intern at Machine Learning group, Microsoft Research, advised by Dr. Lei Song.

My research interests include large language models, reinforcement learning, convex optimization and non-convex optimization.

News

• [May 2025] I joined X, The Moonshot Factory (Formerly Google X Lab) as an AI Resident in May 2025, working on Tapestry project utilizing the power of LLMs and RL.
• [May 2025] Our paper Unveiling Markov heads in Pretrained Language Models for Offline Reinforcement Learning is accepted by ICML 2025.
• [May 2024] I joined Microsoft Research as a Research Intern, working on in-context learning and offline reinforcement learning.

Experience

• AI Resident, X, The Moonshot Factory (Formerly Google X Lab).
  • 05/2025 - Now
• Research Intern, Microsoft Research.
  • 05/2024 - 08/2024
• Research Assistant, Penn State University.
  • 08/2021 - Now

Selected Publications

• Unveiling Markov heads in Pretrained Language Models for Offline Reinforcement Learning
  Qiushui Xu*, Wenhao Zhao*, Linjie Xu, Lei Song, Jinyu Wang, Chunlai Zhou, Jiang Bian
  • Accepted by ICML 2025.
• A stochastic gda method with backtracking for solving nonconvex (strongly) concave minimax problems
  Qiushui Xu, Xuan Zhang, Necdet Serhat Aybat, Mert Gürbüzbalaban
  • ArXiv preprint, 2024.

• AGDA+: Proximal Alternating Gradient Descent Ascent Method With a Nonmonotone Adaptive Step-Size Search For Nonconvex Minimax Problems
  Xuan Zhang*, Qiushui Xu*, Necdet Serhat Aybat
  • Arxiv preprint, 2024.

(* indicates equal contribution)

Invited Talks

• INFORMS 2024, INFORMS 2023, MOPTA 2023. Title: A stochastic gda method with backtracking for solving nonconvex (strongly) concave minimax problems.

Service

• Journal Reviewer: Mathematics of Computation
• Conference Reviewer: AAAI 2024, NeurIPS 2024, AISTATS 2025

Teaching

• Deterministic Models in Operations Research
  • Teaching Assistant, The Pennsylvania State University, 2025 Spring
• Deterministic Models in Operations Research
  • Teaching Assistant, The Pennsylvania State University, 2024 Fall
• Manufacturing Systems Design and Analysis
  • Teaching Assistant, The Pennsylvania State University, 2024 Fall
• Linear Algebra
  • Instructor, The Pennsylvania State University, 2023 Summer Bootcamp