Environment-induced decoherence: off-diagonals decay exp(−t/T₂)

Zeh 1970 / Zurek 1981-1991 / Joos-Zeh 1985: coupling of a quantum system to a macroscopic environment causes the off-diagonal coherences of the reduced density matrix ρ_S = Tr_B(ρ_tot) to decay on a timescale T₂ (or T_coh) much shorter…