Quantum nanoscience preserve and maximize coherence. Superposition is the quantum phenomena wherein an entity can simultaneously exist in two states. The classic description is the though experiment of Schroedinger’s Cat. In this gedanken experiment, the cat can be both alive and dead until the state of the cat is actually observed. Entanglement can link the quantum states of two or more objects over any distance. Entanglement lies at the heart of quantum teleportation and quantum communication. The pursuit of quantum coherence-enabled functionality includes the enabling fields of quantum nanoscientific research, such as enabling materials and tools that are directed towards the goal
Measurement in quantum mechanics bit more convenient to write the Hilbert space as a direct sum of multiple eigen"spaces". The probability of measuring a particular eigenvalue is the squared component of the state vector in the corresponding eigenspace, and the new state after measurement is the projection of the original state vector into the appropriate eigenspace. Instead of performing quantum-mechanics computations in terms of wave functions (kets), it is sometimes necessary to describe a quantum-mechanical system in terms of a density matrix. The analysis in this case is formally slightly different, but the physical content is the same, and indeed this case can be