  While compressing a colloidal state by optical means alone has been
previously achieved through a specific time-dependence of the trap stiffness,
realizing quickly the reverse transformation stumbles upon the necessity of a
transiently expulsive trap. To circumvent this difficulty, we propose to drive
the colloids by a combination of optical trapping and diffusiophoretic forces,
both time-dependent. Forcing via diffusiophoresis is enforced by controlling
the salt concentration at the boundary of the domain where the colloids are
confined. The method takes advantage of the separation of time scales between
salt and colloidal dynamics, and realizes a fast decompression in an optical
trap that remains confining at all times. We thereby obtain a so-called
shortcut to adiabaticity protocol where colloidal dynamics, enslaved to salt
dynamics, can nevertheless be controlled as desired.
