||Quantum computing is contrasted with classical computing. The foundation of classical computing starts with a bit, a unit of information that can be in one of two states, 0 or 1. In quantum computing, the analogue of a bit is a qubit. For a qubit, 0 and 1 are just two possible states that a qubit could be in among others. The other possible physical states are motivated by possibilities of quantum systems such as superpositions. The idea behind a qubit as a means for computing has historically been speculative, but recent technological advances are bringing us closer to the realization of quantum computing. One of the main challenges in this area is to construct quantum systems that avoid decoherence as long as possible while manipulating the system. Another issue has to do with algorithms that serve as a foundation for security. If quantum computing systems are eventually constructed, they have the potential to undermine current encryption practices because many known intractable factoring problems would be turned into tractable ones. Of more philosophical interest, the technological development of quantum computing has the potential to help us better understand the foundations of quantum physics.