We don't know for sure of any planets around Alpha Centauri but, if there were any, SPHERE should be able to resolve a 5000 times fainter (the system is 75 times closer) IR source orbiting as close as 2 UA (roughly the same angular separation from the star as the closest planet detected at 160 UA) from Alpha Centauri A or B.

As for Proxima, Proxima b orbits at 0.05 UA (which is very close). I don't think we could separate its light from the parent star.