Schedule an 2-hour phone interview with their quant researchers (each for one hour). One that scheduled time, they call me and the interview took place over phone. There's two part: one for math/stats problem, and the other for coding (via hackerrank). You can choose whatever language you prefer.

Process involves 3 x 1 hour virtual interviews that will cover basic probability/stats/coding tasks, passing this there is an in person day with a more involved challenge and presentation to team. Final HR style interview will only happen all this and one should expect 2-3 weeks between interviews.