Ramsey fringe visibility: V(τ) = exp(−τ/T₂); P(τ) = 0.5·(1 + V·cos(ωτ + φ))

Ramsey fringe decoherence envelope. From framework F7, the signal visibility decays exponentially with phase-relaxation time T₂: V(τ) = e^(−τ/T₂). Sympy canonical pins: V = 'exp(-tau/T_2)'; P(τ) = '1/2 + exp(-tau/T_2)*cos(omega*tau +…