We are a European deep-tech leader in quantum and AI, backed by major global strategic investors and strong EU support. Our groundbreaking technology is already transforming how AI is deployed worldwide — compressing large language models by up to 95% without losing accuracy and cutting inference costs by 50–80%.
Joining us means working on cutting-edge solutions that make AI faster, greener, and more accessible — and being part of a company often described as a “quantum-AI unicorn in the making.”

We offer

Competitive annual salary

Two unique bonuses: signing bonus at incorporation and retention bonus at contract completion.

Relocation package (if applicable).

Up to 9-month contract, ending on June 2026.

Hybrid role and flexible working hours.

Be part of a fast-scaling Series B company at the forefront of deep tech.

Equal pay guaranteed.

International exposure in a multicultural, cutting-edge environment.

As a Senior LLM Engineer, you will

Design and implement strategies for creating, sourcing, and augmenting datasets tailored for LLM training and fine-tuning.

Develop scalable pipelines to collect, clean, filter, annotate, and validate large volumes of text data, ensuring quality, ethical compliance, etc.

Collaborate with ML engineers, researchers, and software engineers to achieve ambitious goals in the preparation of LLMs and complementary work (preparing datasets, model evaluation, model serving, etc.).

Develop and integrate new routines for modifying and enhancing LLMs, and extending their functionality.

Make effective use of distributed compute resources and clusters (GPU’s), identify opportunities for further optimization.

End-to-end preparation of compressed and specialized LLMs for use in production.

Keep up to date with research trends in LLM foundation models, dataset curation, LLM pretraining data, and benchmarking.

Contribute to building documentation, development standards, and a healthy shared code base.

Mentor other engineers and provide knowledge sharing of cutting-edge techniques.

Required Qualifications

Master’s, or Ph.D. in Computer Science, AI, Data Science, Physics, Math, or a related field. Or equivalent industry experience.

3+ years of experience in data science, machine learning, or related roles, with demonstrated experience with NLP or LLMs.

In-depth knowledge of large foundational model architectures (language and multimodal models) and their lifecycle: training, fine-tuning, alignment, and evaluation.

Proficient in Python and data tooling ecosystems (Pandas, NumPy, Hugging Face Datasets & Transformers libraries).

Hands-on experience with text data collection from diverse sources: web scraping, APIs, proprietary corpora, etc.

Strong understanding of data quality metrics including bias detection, toxicity, and readability.

Experience working in large shared distributed computing environments, familiarity with relevant tools for hardware optimization (vLLM, TensorRT, NeMo, etc.).

Experience with version control (git), unit testing, and other fundamental aspects of software development.

Effective communication and interpersonal abilities.

Preferred Qualifications

Experience building or contributing to datasets used in LLM pretraining or supervised fine-tuning.

Experience building foundational LLMs from the ground up

Familiarity with alignment techniques (e.g., reinforcement learning, preference modeling, reward modeling).

Exposure to multilingual and low-resource language datasets.

Contributions to open-source datasets, tools, or publications in dataset-centric research.

Knowledge of ethical AI, data governance, privacy laws (e.g., GDPR), and responsible data use.

Familiarity with the software development lifecycle and agile methodologies

About Multiverse Computing

Founded in 2019, we are a well-funded, fast-growing deep-tech company with a team of 180+ employees worldwide. Recognized by CB Insights (2023 & 2025) as one of the Top 100 most promising AI companies globally, we are also the largest quantum software company in the EU.
Our flagship products address critical industry needs:

CompactifAI → a groundbreaking compression tool for foundational AI models, reducing their size by up to 95% while maintaining accuracy, enabling portability across devices from cloud to mobile and beyond.

Singularity → a quantum and quantum-inspired optimization platform used by blue-chip companies in finance, energy, and manufacturing to solve complex challenges with immediate performance gains.

You’ll be working alongside world-leading experts in quantum computing and AI, developing solutions that deliver real-world impact for global clients. We are committed to an inclusive, ethics-driven culture that values sustainability, diversity, and collaboration — a place where passionate people can grow and thrive. Come and join us!

As an equal opportunity employer, Multiverse Computing is committed to building an inclusive workplace. The company welcomes people from all different backgrounds, including age, citizenship, ethnic and racial origins, gender identities, individuals with disabilities, marital status, religions and ideologies, and sexual orientations to apply.

Department: Technical
Role: Machine Learning Engineer
Locations: Madrid, Barcelona
Employment type: Contract
Workplace type: Hybrid
Seniority level: Mid-Senior level

About MULTIVERSE COMPUTING

Come and join our multicultural team!

5 locations
+27 languages

Founded in 2019

Coworkers +150

Technical · Madrid, Barcelona

Senior LLM Engineer(9-month contract with bonus incentives)

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