Editing Quantum information (section)

==Relation to quantum mechanics==
[[Quantum mechanics]] is the study of how microscopic physical systems change dynamically in nature. In the field of quantum information theory, the quantum systems studied are abstracted away from any real world counterpart. A qubit might for instance physically be a [[photon]] in a [[Linear optical quantum computing|linear optical quantum computer]], an ion in a [[trapped ion quantum computer]], or it might be a large collection of atoms as in a [[Superconducting quantum computing|superconducting quantum computer]]. Regardless of the physical implementation, the limits and features of qubits implied by quantum information theory hold as all these systems are mathematically described by the same apparatus of [[Density matrix|density matrices]] over the [[complex number]]s. Another important difference with quantum mechanics is that while quantum mechanics often studies [[infinite-dimensional]] systems such as a [[Quantum harmonic oscillator|harmonic oscillator]], quantum information theory is concerned with both continuous-variable systems<ref name="Weedbrook2012"/> and finite-dimensional systems.<ref name="Hayashi2017"/><ref name="Watrous2018"/><ref name="Wilde2017"/>