Editing Quantum decoherence (section)

==Timescales==
Decoherence represents an extremely fast process for macroscopic objects, since these are interacting with many microscopic objects, with an enormous number of degrees of freedom in their natural environment. The process is needed if we are to understand why we tend not to observe quantum behavior in everyday macroscopic objects and why we do see classical fields emerge from the properties of the interaction between matter and radiation for large amounts of matter. The time taken for off-diagonal components of the density matrix to effectively vanish is called the '''decoherence time'''. It is typically extremely short for everyday, macroscale processes.<ref name="zurek03"/><ref name="zurek91"/><ref name="Zurek02"/> A modern basis-independent definition of the decoherence time relies on the short-time behavior of the fidelity between the initial and the time-dependent state<ref name=Beau2017>{{cite journal
 | last1= Beau
 | first1 = M.
 | last2 = Kiukas
 | first2 = J.
 | last3 = Egusquiza
 | first3 = I. L.
 | last4 = del Campo
 | first4 = A.
 | title = Nonexponential quantum decay under environmental decoherence 
 | journal = Phys. Rev. Lett. 
 | volume = 119
 | pages = 130401
 | year = 2017
 | issue = 13
 | doi = 10.1103/PhysRevLett.119.130401
 | pmid = 29341721
 | bibcode = 2017PhRvL.119m0401B 
 | arxiv = 1706.06943
 | s2cid = 206299205
 }}</ref> or, equivalently, the decay of the purity.<ref name=Xu2019>{{cite journal
 | last1= Xu
 | first1 = Z.
 | last2 = García-Pintos
 | first2 = L. P.
 | last3 = Chenu
 | first3 = A.
 | last4 = del Campo
 | first4 = A.
 | title = Extreme Decoherence and Quantum Chaos
 | journal = Phys. Rev. Lett. 
 | volume = 122
 | pages = 014103
 | year = 2019
 | issue = 1
 | doi = 10.1103/PhysRevLett.122.014103
 | pmid = 31012673
 | bibcode = 2019PhRvL.122a4103X 
 | arxiv = 1810.02319
 | s2cid = 53628496
 }}</ref>