The differences between quantum information and classical information are due to the difference of a qubit in a quantum-physical system capable of storing it from a bit in a classical-physical system capable of storing it.1 This difference arises primarily from the superposition principle of quantum mechanics; despite its being bivalent in the chosen computational basis, a qubit system can be in one of an infinite number of significant states, whereas a bit is capable of being in only one of two significant states.2 A qubit system in general also must be considered as at the same time potentially being in one measurable state and/or the other opposite state rather than actually being in just one of the two available states as must necessarily be the case for a bit encoded in a classical physical system. Furthermore, unlike a classical state, a single unknown qubit-system state cannot generally be found by a single measurement. Rather, an ensemble of systems must be measured to discover their unknown shared quantum state.3 It is the nature of quantum potentiality that alternative possibilities for reaching a given quantum state at a given moment superpose, and so are capable of interfering with each other.


Quantum State Pure State Stokes Parameter Quantum Gate Qubit State 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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© Springer Science+Business Media, LLC 2007

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