Cool game! Even if I have some knowledge of quantum computing, it did not kept me from finding some enjoyment out of the game ! It's the type of games that makes me want to find optimal strategy using some maths. I think it's really original to have particle spin as your theme component.
The visual are fine. I think it would have been better to have a more rapid color change when a particle starts slowing down, or maybe making it flicker would better catch player's attention. The visual when the Qomputations take place is extremely satisfying !
If you have not got any ideas yet for musics and sound effects:
(for the music) I would suggest some ambient sound reminding of space
(for sound effect) a cash register sound effect when you buy something
coins sound effects when you get some money
a spinning object sound (in the ideas of a washing machine for example) when all particles are in superposition, this way the player as a audio hint to know if all particles are in superposition
An electricity sound effect when a computation happen would add even more satisfaction to it, in my opinion
Overall, really cool stuff and a nerd like me can play this for a long time