With Γ = 0, the Bloch vector rotates while its length stays 1. The state remains pure.
Live state
time t/T0.000
2|ρ₀₁|1.000
purity Tr(ρ²)1.000
entropy S(ρ)0.000 bit
phase0.0°
PURE COHERENT STATE
Read this picture carefully: the sphere is an abstract state space, not a physical shell around a particle. The trail is the history of the state, not a trajectory through ordinary space.
What the controls reveal
For a superposition, the transverse radius shrinks. Off-diagonal density-matrix terms fade.
Pure dephasing leaves r_z unchanged. This separates loss of phase coherence from energy relaxation.
The same evolution can be read as a Bloch vector, a density matrix, coherence, purity, or entropy.
Try to break your intuition
Select |0⟩, then push dephasing to the maximum. Why does almost nothing happen? A Z-basis eigenstate has no relative phase between |0⟩ and |1⟩ to erase. Then switch back to |+⟩ and compare.
Change the initial state and ΓT. The lab will report what the model predicts.