  Decoherence-free subspaces allow for the preparation of coherent and
entangled qubits for quantum computing. Decoherence can be dramatically
reduced, yet dissipation is an integral part of the scheme in generating stable
qubits and manipulating them via one and two bit gate operations. How this
works can be understood by comparing the system with a three-level atom
exhibiting a macroscopic dark period. In addition, a dynamical explanation is
given for a scheme based on atoms inside an optical cavity in the strong
coupling regime and we show how spontaneous emission by the atoms can be highly
suppressed.
