A month ago many computer-driven investors watched astonished as markets were wracked by a financial tempest, with once-hot stocks tumbling and previously shunned sectors enjoying a revival. But for Michael Kharitonov, the chief executive of San Francisco-based Voleon Group, the rapid rotation out of momentum stocks that wrongfooted many investors was "boring". The $6bn-in-assets hedge fund hardly noticed the brief but dramatic reversal. "We saw nothing," he says, with a chuckle. Voleon sees itself as at the vanguard of the next wave of quantitative investing, using machine learning to unearth patterns too faint for others to detect.