Twenty-three-time Grand Slam champion Serena Williams defeated world number one Simona Halep on Monday to reach Australian Open quarter-finals for the 12th time. Seven-time Australian Open champion Serena beat Halep with a scoreline of 6-1, 4-6, 6-4 in an hour and 47 minutes. Halep had finished runner-up last year, after losing in the final to Caroline Wozniacki.