Here's a recording of an interview with James Thomas, Director of Research for Headlands Technologies, LLC, recorded ~3 years ago.
https://soundcloud.com/techzing/techzing-185
As you may have expected, he did not disclose anything related to trading algorithms. Therefore this interview is just a nice alternative to playing background music while think/coding your strategy.
The only useful thing that I got out of the interview was that Headlands are using GPUs for trading.