It kinda depends on how much info you want to know, but basically superposition is the key here, superposition means a particle is in every possible state at once. It's not until we observe a particle that the particle chooses a state.
The most common example would be the double-slit experiment where light was shown to have both particle and wave properties depending on when it was observed, each photon itself would somehow turn into two photons when passed through a double slit without being observed, but when the photons were detected at either slit before being allowed to go through, only one photon appears on the back wall.
Full blown quantum computers rely on something known as entanglement, and what that mean is that two particles are linked to one another, I won't get too in-depth with entanglement, but basically when you observe the state of one you will instantly know the state of the other no matter how far apart the entangled particles are. China uses this pretty effectively to secure their military and intelligence satellite comms.
Now, that is actually also something you *could* build at home, unfortunately the BBO crystal is ridiculously expensive, there are cheaper alternatives, but in addition to that you also need a very powerful laser.
As for my model, it's purely a random number generator designed for cryptographic keys. It will produce any number of bits with equal probability of being a 1 or a 0.
so for a single bit:
1 = 50%
0 = 50%
00-11 = 25%
Probability of generating any 1024 bit number:
What makes it secure is it does not rely on an algorithm to generate a number. This means nobody can reliably recreate a random number (which they could on other systems). So if you have a 1024 bit cryptokey an attacker could not decrypt it by attacking the randomness of it and it also means if you somehow got hacked they would not be able to pre-seed it to change any future key generations you attempt.
Right now I'm using a 555 timer to keep things cheap, but since it uses light to generate our numbers rather than an algorithm, we're going to be able to generate gigabytes of random numbers in a very short timespan.
I'm also looking into selling these as kits with instructions on how to build your own with off the shelf components for the DIYers among us