Quantum Computation and raising Schrodinger´s cat

Two discrete energy levels in quantum system, such as an atom, can be used to store a bit of information. However, quantum systems can also exist in superposition states, thereby storing both states of the bit simultaneously. This property potentially leads to an exponential increase in memory and processing capacity. It would enable a quantum computer to efficiently solve certain problems, such as factorizing large numbers, which may be intractable on a classical computer. Actually building a useful quantum computer is an extremely daunting task due to the necessity of overcoming decoherence. Nevertheless, in the near term, the principles of quantum information processing may find important applications in metrology. A quantum computer would also realize a mesoscopic version of "Schrodinger\´s Cat," a bizarre situation where a cat could be simultaneously dead and alive. A number of physical systems are currently considered for building a quantum computer; we focus on examples using atoms, but also discuss other possible implementations