How Far Out Is Quantum Theory Really?

The quantum world is commonly conceived of as (i) wildly strange, and (ii) far removed from everyday experience. But (i) certainly need not be true: many find quantum theory quite natural and intuitive (although others disagree, as I have discussed before). And it's similarly unclear whether or not (ii) is true. So I propose we try to figure it out.

For example, here's an experimental illustration of quantum diffraction (called "quantum eraser" by the authors) that you can do in your house. Admittedly, this particular experiment has a classical description. But is it possible to make the experiment just a little more sophisticated, and observe a truly non-classical effect? And are there other canonical "quantum phenomena" that are similarly accessible?

I know of no satisfying answer. So let me pose the following challenge:

Using only simple, every-day objects, design experiments illustrating all the canonical quantum effects.

There are different ways of breaking down what these effects are, but here's one way of doing it. Design "every-day" experiments of the following three phenomena:

1. Discrete energy values (e.g., a blackbody radiation experiment);


2. General diffraction (outside the scope of classical E&M); and


3. Coherent superposition.

These phenomena together are sufficient to give us much of the basis for ordinary non-relativistic quantum mechanics. Wouldn't it be nice to have some idea as to just how far out they really are?