Senior Research Scientist | Model Steering in London

Meet DeepL. DeepL is a global AI product and research company focused on building secure, intelligent solutions to complex business problems. Over 200,000 business customers and millions of individuals across 228 global markets today trust DeepL's Language AI platform for human-like translation, improved writing and real-time voice translation. Founded in 2017 by CEO Jaroslaw “Jarek” Kutylowski, DeepL now has around 1,000 passionate employees and is supported by world-renowned investors including Benchmark, IVP, and Index Ventures. Our goal is to become the global leader in trusted, intelligent AI technology, building products that drive better communication, foster connections, and create a meaningful impact.

What sets us apart is our blend of cutting-edge AI technology, meaningful work, and a culture where people truly thrive. We’re a team of innovators, researchers, and creators driven by a shared purpose to unlock human potential by making work simpler, smarter, and more connected. When we share what it’s like to work at DeepL, the reactions are overwhelmingly positive. This might be because of our technology that helps millions of people and businesses communicate and work better every day, or because of the trust, curiosity, and care that shape our culture. What we know for sure is this: being part of DeepL means joining a team dedicated to innovation, growth, and well-being.

Our Language AI teams form the foundation of DeepL's success. We are a dedicated group of researchers who collaborate closely with engineers, product managers, and designers. Our mission is to build the world's leading language AI system to deliver perfect translations for the most demanding use cases. To that end, we take responsibility for the entire life cycle of the machine learning models that power our language AI products. This includes data, training, quality assurance, and operational aspects. In our highly collaborative teams, each person has the scope to drive impact across the company.

Your responsibilities include:

• Driving the development of translation models that are steerable conditioned on user preferences, rules and context.
• Conducting hands-on research and development on post-training for our core translation models: supervised fine-tuning, knowledge distillation, preference optimisation, and reinforcement learning tuned to translation quality.
• Building reward models and evaluator models for translation, including rubric- and reference-based grading, and investigating and mitigating reward hacking and quality-estimation failure modes.
• Driving an agenda toward models that ingest multimodal content and context to increase translation quality.
• Owning the full lifecycle of model delivery: prototyping, ablations, training, evaluation, optimisation, and production deployment, working closely with engineering to ship into real-time systems at scale.
• Establishing strong practices for evaluation, reproducibility, monitoring, and continuous model improvement in production.
• Mentoring researchers and engineers, promoting hands-on collaboration, and raising the bar for model quality.

Qualities we look for:

• Proven experience making large models steerable and instruction-following by identifying the most effective method to instill a given behaviour, drawing from instruction tuning, latent space methods, steering vectors, and/or constrained encoding and decoding methods.
• Deep, hands-on expertise in LLM post-training (SFT, DPO), knowledge distillation (teacher-student training), and/or reinforcement learning (RLHF/RLAIF, PPO/GSPO, and reward modelling).
• Strong data-centric instincts for building synthetic-data and preference-data pipelines, LLM-as-judge generation, data curation and filtering, and reasoning about data mixtures and ablations.
• Experience designing evaluation and reward signals using automatic metrics, LLM-as-judge evaluation, non-verifiable rewards, and human-in-the-loop evaluation.
• A hands-on builder who enjoys training models, running experiments, debugging pipelines, and integrating ML systems into production while staying grounded in product impact and real-world quality.
• Ownership of a substantial research direction with strong execution, and experience mentoring others on a fast-moving, applied research team.
• Strong coding and experimentation skills (Python, PyTorch/JAX/Tensorflow), and the ability to communicate clearly and align research with product and engineering priorities.

Nice to have:

• Demonstrated experience fine-tuning and training large models at scale, including distributed/multi-node training (e.g. FSDP, DeepSpeed, or Megatron-style frameworks) and efficient training techniques.
• Experience fine-tuning existing reasoning models for specific tasks and behaviours without degrading their reasoning capabilities.
• Experience with machine translation, multilingual NLP, or language quality estimation.
• Familiarity with inference and serving at scale (e.g. via vLLM, SGLang, TensorRT-LLM, etc) and long-context modelling.
• Publications at top-tier venues.

What we offer:

• Diverse and internationally distributed team: joining our team means becoming part of a large, global community with people of more than 90 nationalities.
• Open communication, regular feedback: as a language-focused company, we value the importance of clear, honest communication.
• Hybrid work, flexible hours: we offer a hybrid work schedule, with team members coming into the office twice a week.
• Virtual Shares: an ownership mindset in every role.
• Regular in-person team events: we bond over vibrant events that are as unique as our team.
• Monthly full-day hacking sessions: every month, we have Hack Fridays.
• 30 days of annual leave: we value your peace of mind.
• Competitive benefits: we’ve crafted it to reflect the diversity of our team.

If this role and our mission resonate with you, but you’re hesitant because you don’t check all the boxes, don’t let that hold you back. At DeepL, it’s all about the value you bring and the growth we can foster together. We can’t wait to meet you!

We are an equal opportunity employer. You are welcome at DeepL for who you are - we appreciate authenticity here. Our product is for everyone, and so is our workplace. The more voices we have represented and amplified in our business, the more we will all succeed, contribute, and think forward!