Add `vev(expr) = scalar_term(normal_order(expr))` — the first user-facing observable; composes with everything else. Tests: `vev(a^n * dag(a)^n) == factorial(n)` for n=1..5; `vev(dag(a)*a) == 0`.
Add
vev(expr) = scalar_term(normal_order(expr))— the first user-facing observable; composes with everything else.Tests:
vev(a^n * dag(a)^n) == factorial(n)for n=1..5;vev(dag(a)*a) == 0.