April 11, 2026
One gate, many hot takes
Tofolli gates are all you need
A tiny switch flip ignites a big brawl: typo cops, space prophets, and “prove it” skeptics
TLDR: A reversible “Toffoli” switch can build any logic and may cut energy use by avoiding data erasure, says the article. The crowd split fast: typo enforcers nitpicked, cosmic theorists dreamed big, and skeptics demanded real-world proof—turning a physics lesson into a punchy debate over hype vs. reality.
The article says a reversible “switch trick” called a Toffoli gate can build any logic and, used cleverly, may save energy today—because erasing data burns power. That’s a big claim! But the comments stole the show. First move? A drive‑by correction: “*Toffoli”—and suddenly the headline itself is on trial. Classic internet.
Then the thread veers into the cosmos when a user drops Tipler’s Omega Point—a wild theory about ultimate computation at the end of the universe. From “fix the typo” to “we’ll compute eternity” in two comments flat. Meanwhile, the pragmatists crash the party: one voice demands, where is this working now and how big are the savings? No hype, just receipts. Another user backs that up with receipts of their own, linking an IEEE Spectrum piece on reversible computing and a 2016 YouTube talk, name‑dropping Michael Frank’s cameo in an earlier HN thread.
Between the energy physics (Landauer’s principle = erasing info costs energy), the not‑quite‑sci‑fi promise of “run your computer backward,” and the fine print (reversible tricks need extra bits), the community mood swings from pedantic to prophetic to prove‑it. Verdict? Big brains flipping switches—and bigger egos flipping out.
Key Points
- •Landauer’s principle sets the minimum energy to erase one bit at E ≥ log(2) kB T.
- •Reversible computation has no theoretical lower limit on energy consumption.
- •In practice, bit erasure energy is about a billion times higher than Landauer’s bound, yet reversible circuits can still use less energy than conventional ones.
- •A Toffoli gate is reversible, self-inverse, and flips its third bit only when the first two inputs are 1.
- •A NAND gate can be implemented using a Toffoli gate with input (a, b, 1), implying any Boolean function can be computed reversibly, albeit with extra inputs/outputs.