Ludwig will join the staff of new Aztecs coach Rocky Long, who took over after Brady Hoke left to coach Michigan.
Ludwig, 46, was offensive coordinator at Cal the past two seasons.
Horton hired at SDSU
Jeff Horton will be named assistant head coach/running backs coach at San Diego State, Rivals.com has learned.
Horton is a veteran coach who was offensive coordinator at Minnesota last season. He took over as interim head coach after Tim Brewster was fired in mid-October, leading the Gophers to a 2-3 record that included a win over Iowa to earn Minnesota the Floyd of Rosedale Trophy. It was the first trophy-game win for the Gophers since before Brewster took over.
Horton was head coach at Nevada in 1993, going 7-4. He also was head coach at UNLV from 1994-98, forging a 13-44 mark with one bowl trip.
Horton has been an assistant at Wisconsin (1999-2005) as well as with the NFL's St. Louis Rams (2006-08) and Detroit Lions (2009).