As manifested in Shor’s groundbreaking seminal work, quantum mechanics promise the possibility of having substantially more effective computation devices. This is in fact the result of quantum parallelism: the coherent interference pattern between the multitude of superpositions.
But the fragility of a quantum state, which on one hand is used to take advan- tage of the power of entanglement, also can result in undesired interference between the state of the quantum system, carrying or storing the information, with the envi- ronment. The problem of maintaining quantum coherence remains one of
the most important obstacles in the attempt of exploiting the new possibilities opened up by applications of quantum mechanics in classical computations.
The seminal independent work of Shor and Steane gave birth to the current active theory of quantum error correction, which is the subject of this thesis.