Dynamical suppression for decoherence of continuous variable quantum information

A quantum master equation is derived in a rigorous way for a bosonic system coupled to a thermal reservoir when phase-modulation π-pulses are applied to the relevant system. It is shown that decoherence of continuous variable quantum information can be suppressed if the pulse separation is shorter than the correlation time of the thermal reservoir. The time-evolutions of nonclassicality and entanglement are investigated.