SFQ Symbol Card (five symbols)

Prereqs: none (cheatsheet) · best with How to read SFQ notation
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In one minute. These five labels show up everywhere in SFQ sketches. Learn the job of each symbol; details live on the linked pages.

The five symbols

  Φ0     flux quantum          "one packet of magnetic flux"
  Ic     critical current      "how hard you can push before the JJ switches"
  φ      Josephson phase       "the junction's internal angle; 2π slip ↔ one packet"
  βC     McCumber parameter    "damping personality: pulse vs latch"
  ∫V dt  pulse area            "for one slip, area = Φ0"

Symbol	Say it	Means (teaching)	Not
${\Phi }_0$	"phi-zero"	One flux packet / pulse token size ($\approx 2.07\text{mV}\cdot \text{ps}$)	A CMOS voltage rail
$I_c$	"I-sub-c"	Max supercurrent before the junction switches	Supply voltage $V_{DD}$
$\varphi$	"phi"	Phase across the junction	Magnetic flux $\Phi$ (related but different letter)
${\beta }_C$	"beta-C"	Damping: small → short pulse; large → can latch	Transistor gain
$\int Vdt$	"integral V dt"	Voltage-time area of a pulse	Peak millivolts alone

Interactive lab

Try this in place. Prefer full-screen? Open the lab page.

1. Tap a card to peek at the teaching gloss, then pick the matching meaning.
2. Cycle all five: ${\Phi }_0$, $I_c$, $\varphi$, ${\beta }_C$, $\int Vdt$.

Tiny sketches

Pulse (overdamped):     V
                        |  /\
                        |_/  \___   area ≈ Φ0

Stored bit (loop):      ( loop )  with Φ0 inside ↔ circulating current

Analogy palette (used in this curriculum)

Picture	Stands for
Airport / terminals	Branches of superconducting electronics
Telegraph / clicks	Classical SFQ pulses in timing windows
Music hall	Fragile superconducting qubits (not SFQ logic)

Next steps

• Full dialect lesson: How to read SFQ notation
• Express lane continues: Superconductivity intuition