Flux qubits (also known as persistent current qubits), one kind of superconducting tunnel junction circuits, are recently demonstrated as a promising candidate to realize quantum computations. In order to do large-scale quantum information processing, it is necessary to switch on and off the couplings between individual flux qubits in the time-domain while those qubits retain coherence. This report contains two parts: one is to describe my understanding of models, fabrications and measurements for one single flux qubit; the other is to compare two proposed schemes and the corresponding experimental realizations of coherent tunable couplings between flux qubits.