Part 2 mentions two quantum algorithms that could be used to break Bitcoin (and SSH and SSL/TLS; and most modern cryptographic security systems):
Shor's algorithm for factorization and Grover's search algorithm.
I don't know what heading I'd suggest for something about how concentration of quantum capabilities will create dangerous asymmetry. (That is why we need post-quantum ("quantum resistant") hash, signature, and encryption algorithms in the near future.)
So I guess an explanation has to be very careful with that then. I liked the style. Good way to make clear that this isn't some uptight explanation, but the attempt to experience a little with the explanation style. But it comes with the risk to just confuse people.
The best introduction to this kind of computation that I've seen is Eric Johnston's SIGGRAPH 2016 talk[1], and the associated interactive simulator[2]. In the talk uses quantum superposition to implement a type of "quantum supersampling[3]".
I feel like theres potential here for quantum computers to represent perceptrons in neural networks, since they seem to both operate with rough states.
I meant, physically, what gives different? why after applying the gate once on 1 there is a 50% the spins flip but when applying to 0 no-chance of that.
The states you get are H(|0>)=|0>+|1> and H(|1>)=|0>-|1>, both of which have 50% probablity to end up as 0 or 1 once they are measured. The difference of the "-" in the second state is only visible if you carry on the computation, not if you measure.
> Qubits represent 0 and 1 using quantum phenomenon like the nuclear spin direction of individual atoms.
Not trying to be that guy but this is so wrong/misleading, it hurts (and I'm not even a physicist!). Spin isn't a "direction" and atoms don't "spin" -- well, they might, but the quantum kind of spin has nothing to do with angular momentum.
>In quantum mechanics and particle physics, spin is an intrinsic form of angular momentum carried by elementary particles
And
>In some ways, spin is like a vector quantity; it has a definite magnitude, and it has a "direction" (but quantization makes this "direction" different from the direction of an ordinary vector).
Not a physicist but I did study a degree in it. Spin is absolutely a direction and absolutely related to angular momentum, since it's basically the angular momentum that you get when all the angular momentum we understand is removed.
There's a reason it's called spin! I think what you're trying to get at is that it can't be understood in the traditional context of an object spinning, but the way that you're saying it is wrong.
No, ELECTRON spin is not exactly a direction, as in 3D vector. In every direction, it can be +1 or -1. It follows different transformation than a vector(wigner matrix for j=1/2 and 1). Expressions like direction |z> and |x> are not independent in this case.
Photon spin is actually a vector, as with all spin 1 particle.
Apart from praising Common Lisp he describes how they are building an assembler-like language for quantum computing.
The HN thread: https://news.ycombinator.com/item?id=15880172