PhD Research Scientist Intern - Reinforcement Learning for Diffusion Modelling

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.

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

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 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

• PyTorch at scale, and the ability to write research code for data processing, training and evaluation.
• Multi-GPU training (FSDP, Deep Speed) and evaluation-harness engineering.
• Layered or RGBA generation, matting, or in painting 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.

• 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.

Other stuff to know

We make hiring decisions based on your experience, skills and passion, as well as how you can enhance Canva and our culture. When you apply, please tell us the pronouns you use and any reasonable adjustments you may need during the interview process.

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.