Closed loops hold integer multiples of Φ₀ — no stable half-quantum. One 2π slip writes/erases one packet. Area of V(t) stays Φ₀; circulating current ≈ Φ₀/L.
Φ₀ ≈ 2.07 mV·ps. Shape of the spike can change; the area is the token. CMOS stores continuous voltage — SFQ stores discrete flux packets.