Quantinuum Software Engineer Interview Questions
& Process

So, this whole thing with Quantinuum took about six months. It started when a recruiter from LinkedIn found me in late September. My first chat was a video call in early October. After that, crickets for three months. Then, mid-January 2026, they reached out again to schedule an on-site interview at their Broomfield, CO office. The on-site interviews are a full day thing, with multiple group sessions. A key part is giving a presentation about something I've worked on that's relevant to the role. This specific role is Principal / Lead Compiler Engineer. Back in October, they mentioned they wanted to improve their compiler's quality, admitting it was currently subpar. What was surprising was that in the later rounds, none of the interviewers seemed to have compiler expertise, and I wasn't asked any compiler-specific questions during the whole day. I even gave a presentation specifically about compilers, but received no questions about it. It felt like they weren't sure what they were looking for. Despite lacking compiler backgrounds, some interviewers had strong opinions on compiler development. The afternoon was more management/behavioral, focusing on team dynamics like handling disagreements and reaching consensus. One interviewer was taken aback when I said I'd admit if I didn't know something and would look it up, suggesting maybe they expected a 'fake it till you make it' response. Some of my presentations included complex code examples related to compiler development, but it seemed nobody grasped the code's subtleties, with one person admitting they couldn't parse it. I wasn't asked about the code, and had to walk through every line. Overall, a pretty disappointing and frankly concerning experience.

Had a chat with HR first, then a technical interview, followed by a chat with the group manager. Things moved quickly after the technical interview. The team is really friendly and helpful, and the team lead is one of the best managers I've had.

The interview process had two stages. The first stage was a technical interview, conducted online via Teams. It was an enjoyable panel interview with 3 people. There weren't any major surprises, it included a logic puzzle, a coding challenge, questions about cloud computing, and a code review. The second stage was a 30-minute call with the hiring manager for the group. I didn't pass this stage; I don't think my background was a good fit, and he might have been right.