opens up an exciting avenue of dynamical protection of quantum entanglement. Indeed, it is now possible to efficiently lock a two-qubit system on a desired entangled state, without any knowledge of the bath. Encouraged by our results for two-qubit systems, we then show that in general, the coherence of an arbitrary $M$-level quantum system, which is characterized by our generalized coherence measure, can also be preserved by UDD to the order of $1+O(T^{N+1})$ with only $N$ pulses, irrespective of how this system is coupled with its environment. Hence, in principle, an arbitrary (but known) quantum state of an $m$-qubit system with $M=2^{m}$ levels can be locked by UDD, provided that the required control Hamiltonian can be implemented experimentally. To establish an interesting connection with a kicked multi-level system recently realized in a cold-atom laboratory [@Jessen], we also explicitly construct the UDD control Hamiltonian for decoherence suppression in three-level quantum systems.

This paper is organized as follows. In Sec. II, we first briefly outline an important result proved by Yang and Liu [@univUDD]; we then present our theory for UDD in two-qubit systems, followed by an extension to multi-level quantum systems. In Sec. III, we present supporting results from some simple 