PhD Research Scientist Intern - Reinforcement Learning for Diffusion Modelling

Canva; Greater London; Hybrid; GBP 12,000 - 16,000; Full time

Job summary

Canva in London (Hoxton) seeks current PhD students for a 16-week AI Research Internship starting in September. You’ll work with Canva’s AI team on a live, industry-scale project, turning your PhD journey into real-world impact, with hands-on data, production infrastructure and deadlines.

You’ll design and validate VLM-based evaluators, develop reward models, and collaborate with researchers, engineers and product teams as ideas move toward production and Canva's layered-generation roadmap.

Qualifications

• Currently pursuing a PhD, ideally third year or later.
• Strong diffusion or flow-matching background, with hands-on policy-gradient RL for generative models (GRPO, PPO, DPO or similar).
• Experience fine-tuning VLMs (e.g. with LoRA) and designing prompts or rubrics for evaluation tasks.
• Reward modelling experience, preference optimisation, pseudo-labelling, distillation.
• You can read a recent paper and reproduce it quickly.
• You communicate technical work clearly, in writing and in presentations.

Responsibilities

• Designing and validating a rubric-guided, per-layer VLM judge for RGBA layer decomposition, calibrated against human evaluations.
• Building VLM-based methods for automatic, human-aligned evaluation of multi-layer designs.
• Turning VLM-based evaluators into reward functions to train generative models in a reinforcement learning setting.
• Distilling those judges into lightweight reward models that score layered images from learned representations, at a fraction of the inference cost.
• Collaborating with research, engineering, and product teams to move findings toward production and Canva's layered-generation roadmap.
• Contributing to the broader research community through publication where results support it.

Skills

PhD candidate

Diffusion models

Reinforcement learning

LoRA fine-tuning

VLMs

Prompt design

Reward modelling

Research communication

Education

Pursuing PhD in relevant field

Tools

PyTorch

Multi-GPU

DeepSpeed

Job description

Company Description

Join the team redefining how the world experiences design. Hey, g'day, mabuhay, kia ora, 你好, hallo, vítejte! Our global HQ is in Sydney, Australia, but our London campus sits in Hoxton Square, right in the middle of Shoreditch. It's a bit of a warren of stairs and rooms — you will get lost at first, and someone will happily give you a tour. It's a space where our UK team comes together to connect, create and collaborate. Fun fact: our London team is one of the places where the AI powering Canva gets built. This role is based in London, and we're looking for someone who calls it home. Our hybrid way of working gives you flexibility — you'll have the option to work from home as well as connecting and collaborating with your team in-person, on campus. We trust teams to choose the balance that empowers them to achieve their goals.

Job Description

We’re looking for current PhD students ready to bring their research into the real world and help shape the culture of AI at Canva.

Our full-time, 16 week AI Research Internship starts in September. During your internship, you’ll work directly with Canva’s AI team on a live, industry-scale project, turning part of your PhD journey into real world impact. You’ll gain hands on experience with real data, production infrastructure and real deadlines, while learning from and working alongside the researchers and engineerings creating Canva’s next generation of AI-powered experiences.

What You'd Be Doing In This Role

As Canva scales, change continues to be part of our DNA — but we like to think that's all part of the fun. This gives you a flavour of the work you'd start with, and it will likely evolve over time. At the moment, this role is focused on:

• Designing and validating a rubric-guided, per-layer VLM judge for RGBA layer decomposition, calibrated against human evaluations.
• Building VLM-based methods for automatic, human-aligned evaluation of multi-layer designs.
• Turning VLM-based evaluators into reward functions to train generative models in a reinforcement learning setting.
• Distilling those judges into lightweight reward models that score layered images from learned representations, at a fraction of the inference cost.
• Collaborating with research, engineering, and product teams to move findings toward production and Canva's layered-generation roadmap.
• Contributing to the broader research community through publication where results support it.

The team builds the groundwork before you arrive — baselines reproduced, harnesses running, data prepared. That means you start on the novel parts in week one rather than spending a month on setup.

You're probably a match if

• You're currently completing a PhD, ideally third year or later.
• A strong diffusion or flow-matching background,with hands-on policy-gradient RL for generative models (GRPO, PPO, DPO or similar).
• Experience fine-tuning VLMs (e.g. with LoRA) and designing prompts or rubrics for evaluation tasks.
• Reward modelling experience, preference optimisation, pseudo-labelling, distillation.
• You can read a recent paper and reproduce it quickly.
• You communicate technical work clearly, in writing and in presentations.
• You enjoy working closely with researchers and engineers on hard problems.
• Juggle several threads at once, drop into a new one without losing the last
• Set your own priorities on a daily basis and between checkpoints

Nice to have

• PyTorch at scale, and the ability to write research code for data processing, training and evaluation.
• Multi-GPU training (FSDP, DeepSpeed) and evaluation-harness engineering.
• Layered or RGBA generation, matting, or inpainting experience.
• Familiarity with reward-hacking and score-compression diagnostics, or human-evaluation design.
• Publications or open-source contributions in generative modelling, RLHF, or multimodal models.

What You Should Aim To Take Away

• Publishable and patentable contributions based on the work you’ve done
• A paper draft covering said work, with support on publication strategy.
• Compute, base checkpoints, preference data and annotation budget, provided.
• Four mentors: a coach for weekly 1:1s, plus a specialist lead on each workstream.
• Work that feeds directly into a product used by hundreds of millions of people.

Additional Information

We make hiring decisions based on your experience, skills and passion, as well as how you can enhance Canva and our culture. We celebrate all types of skills and backgrounds at Canva so even if you don’t feel like your skills quite match what’s listed above - we still want to hear from you! Please note that interviews are conducted virtually.