The idea of a quantum bit
A quantum computer sidesteps the exponential blowup of classical simulation by using a two-state quantum system as its basic unit, the qubit, so that superposition, entanglement, and complex-number accounting happen naturally at the hardware layer rather than being approximated in software. The core argument traces to a 1981 talk by Richard Feynman, who closed with the line: 'Nature isn't classical, damn it. And if you want to take a simulation of nature, you'd better make it quantum mechanical.' Bell's theorem, which rules out local hidden variables, supplies the theoretical justification: because the universe has a rich quantum layer that cannot be explained away, a computer meant to simulate it faithfully must operate by the same rules.
- Feynman's 1981 talk also cited earlier work by Toffoli and Benioff, who had already shown that reversible logic gates and manipulation of quantum states were theoretically possible.
- 46 years after Feynman's talk, a practical, general-purpose quantum computer still does not exist.
Transcript
This chapter, from the episode video's captions · 441 words
48:24where the bit is a two-state quantum system and then we bake into the computer the interaction that we're trying to study, right? Then the the quantum mechanics inside the computer is going to take care of all of the superposition entanglement and all of the blow up of complex numbers, right? Because because we're just harnessing the quantum mechanics that we're trying to study >> and at the foundational layer of where the compute happens. >> Yeah. Yeah. hardware is king >> versus after the fact at the software level or at the systems level. >> Yes, exactly. And so he ends his talk with a very famous line that um rings across a lot of quantum computing
49:05literature and a lot of quantum computing deep dives. He says, "Nature isn't classical, damn it. And if you want to take a simulation of nature, you'd better make it quantum mechanical. And by golly, it's a wonderful problem because it doesn't look so easy." No, it certainly doesn't. It certainly does not look so easy. 46 years later, um, we're still trying to make one. >> This is I I think this is a really great starting point because what we've done so far is we've sort of created this understanding of the difference between classical systems versus quantum mechanical systems at a at a theoretical level. Mhm. How that informed the early
49:46countercultural era of computing in general. how this idea then moved to this point of there is actually quantum computing as a competing way to solve certain types of problems as opposed to classical computing because there are fundamental limitations because we found violations of Bell's theorem that mean that the hidden variable thing and the realists sorry >> and if we really want to create simulations that are true to our lived fourdimensional time space. >> Yeah. Whatever. Yeah. >> Right. This magical thingy.
50:27>> Um we're going to need the compute layer to reflect the same quantum mechanical attributes that our theoretical frameworks currently suggest. Yeah. >> Exist. >> Yes. Is that a fair? >> That's exactly right. And and that talk happened in 1981. And he he mentions all of the priors that I've been talking about. He mentions Bell's theorem. He mentions Tifo and Beni off and all these people who said, "Hey, quantum quantum computing is a possibility, right? We have reversible logic, >> right? >> We have a paradigm where we can manipulate a quantum state, right? Even theoretically. And Bell shows that
51:07there's this rich underlying layer that we can actually exploit if we want to, right? um Fineman's argument about
From How Quantum Computing Actually Works (Part 1)
Part I of our quantum computing deep dive traces the field from Bell and Feynman to Deutsch and Shor—and explains what quantum computers actually do differently from classical machines.