Dephasing and relaxation
Environmental coupling reduces useful phase information.
$$1/T_2=1/(2T_1)+1/T_\varphi$$
Physical intuition
Environmental coupling reduces useful phase information.
Deep dive: physical mechanism
Energy relaxation changes populations; pure dephasing randomizes relative phase without exchanging energy.
What is measured experimentally?
Ramsey and inversion-recovery sequences separate coherence channels.
Assumptions, noise and limitations
The simple relation assumes exponential Markovian decay.
Research and simulation exercise
Fit simulated T1 and T2 traces and infer pure dephasing.
Connect the ideas
Explore the chapter overview, learning path, and references.