  A non-dispersing wave packet has been attracting much interest from various
scientific and technological viewpoints. However, most quantum systems are
accompanied by anharmonicity, so that retardation of quantum wave-packet
dispersion is limited to very few examples only under specific conditions and
targets. Here we demonstrate a conceptually new and universal method to retard
or advance the dispersion of a quantum wave packet through 'programmable time
shift' induced by a strong non-resonant femtosecond laser pulse. A numerical
simulation has verified that a train of such retardation pulses stops
wave-packet dispersion.
