> B: apparently |0>, but elsewhere you refer to it being unconstrained. This is probably due to my wording not really being a parallel construction. The uncons

> B: apparently |0>, but elsewhere you refer to it being unconstrained. This is probably due to my wording not really being a parallel construction. The unconstrained qubit was A; in my example, B is the qubit that's in the ground state. Sorry for the confusion! A sibling commenter elaborated on my parenthetical, which is really just a constraint on what values can be used for the probability amplitudes a and b. (I kind of hate the term "probability amplitude", but that's the standard nomenclature.) There are two main observations from a and b being complex numbers: 1. You can turn these amplitudes into classical probabilities for getting a particular outcome out of measuring A by squaring their magnitudes. So if you had a = 3/5 and b = -4/5 i, then you'd have (3/5)^2 = 36% chance of observing |0> and |-4/5 i|^2 = 64% chance of observing |1>. 2. What's perhaps the most important bit about quantum computing is the relative phase between these eigenstates, and the ability to achieve just the right interference pattern such that everything cancels out except for certain peaks that can give you something interesting. This is what differentiates QM from classical probability theory, and why we can't just take the existing quantum algorithms and reimplement them in classical computers.