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Machine Learning Researcher

Citadel Securities
🇬🇧LondonSeniorFull-timePosted September 22, 2026

About the Role

At Citadel Securities, Machine Learning Researchers on our Options team come from a wide range of industries and turn cutting-edge ideas and petabyte-scale data into bleeding edge models with direct trading impact. Our team of researchers iterate quickly, own decisions end-to-end, and operate with substantial autonomy, resources, and scope in a flat, no-bureaucracy environment.

  • Own the full research lifecycle, from hypothesis, experiment design, model validation, risk/overfit controls, to deployment
  • Conduct cutting-edge research and development in machine learning (e.g. LLMs) at scale with a focus on industry leading techniques and their applications in quantitative finance
  • Ship models to production that move P&L in options markets—measured by clear, testable outcomes
  • Prototype, test and iterate fast, taking great ideas from concept to trading in a very short space of time
  • Discover alpha in high-dimensional data with deep learning, time-series, and representation learning
  • Engineer scalable research pipelines from feature generation to distributed training and backtesting
  • Develop trading intuition to translate insights into executable strategies
  • Leverage large scale compute and data (petabytes; large budgets) to run ambitious experiments and push the frontier

Responsibilities

  • Own the full research lifecycle, from hypothesis, experiment design, model validation, risk/overfit controls, to deployment
  • Conduct cutting-edge research and development in machine learning (e.g. LLMs) at scale with a focus on industry leading techniques and their applications in quantitative finance
  • Ship models to production that move P&L in options markets—measured by clear, testable outcomes
  • Prototype → test → iterate fast The resources and support to take great ideas from concept to trading in a very short space of time
  • Discover alpha in high-dimensional data with deep learning, time-series, and representation learning
  • Engineer scalable research pipelines from feature generation to distributed training and backtesting
  • Develop trading intuition to translate insights into executable strategies
  • Leverage large scale compute and data (petabytes; large budgets) to run ambitious experiments and push the frontier

Requirements

  • A curiosity to learn about financial markets, and excitement to understand microstructure, options dynamics, and volatility regimes on the job
  • Masters or PhD degree in mathematics, statistics, physics, computer science, or another highly quantitative field, with advanced training and a strong research track record working on machine learning problems
  • Deep knowledge of cutting edge large scale models and their training and design
  • Training techniques (pre-training, fine-tuning, RL, RLHF), and optimization methods
  • A results-oriented track record of having taken ML ideas from theory to measurable impact
  • Strong math fundamentals (linear algebra, probability, optimization) and mastery of regression/ML for large scale data
  • Hands-on with modern machine learning (sequence models/transformers, representation learning, regularization, cross-validation, causal/robust inference) applied in practice
  • Bias to action & problem-solving demonstrated ability and comfort around owning decisions, iterating quickly, and simplifying complex problems to impactful solutions
  • Curiosity about markets and enthusiasm to learn microstructure, options dynamics, and volatility regimes on the job
  • Fluency in Python (NumPy, PyTorch) and the ability to write clean, modular, performant code for large-scale experiments