  We present an optical "enantio-selective switch", that, in two steps, turns a
("racemic") mixture of left-handed and right-handed chiral molecules into the
enantiomerically pure state of interest. The optical switch is composed of an
"enantio-discriminator" and an "enantio-converter" acting in tandem. The method
is robust, insensitive to decay processes, and does not require molecular
preorientation. We demonstrate the method on the purification of a racemate of
(transiently chiral) D$_2$S$_2$ molecules, performed on the nanosecond
timescale.
