It is sometimes said that wave functions are not real, and simply represent the observer's knowledge of the system. I would like to comment against this point by presenting an experimental setup which would tend to indicate that the wave function is quite real. As far as I know, this setup per se has never been executed (although I am hoping someone might recognize it as something which has been). To follow the setup, you should be familiar with the following experiment: Bell inequalities and quantum mechanics, J. H. Eberly (2001) See Figure 1, the Bell analyzer loop, in which a beam is split into H and V components. Those are then recombined so that the H/V information is erased, leaving a beam with the same properties as it was originally. So if you took a pair of entangled particles, Alice and Bob, and ran each through a Bell analyzer loop, the recombined Alice and Bob are still entangled. This is what the above paper is saying. --------------------- Here is my twist: Frankenstein photons: ===================== Split Alice into Alice-H and Alice-V. Split Bob into Bob-H and Bob-V. Now recombine Alice-H with Bob-V (which is identical to Alice-V). Recombine Bob-H with Alice-V (likewise identical to Bob-V). You will now have 2 Frankenstein photons that are polarization entangled! Now, if the above is accurate (I don't see how it could be expected to be otherwise), then you would have to admit that you are mixing the wave functions of different photons to obtain an effect that clearly does not occur with either portion of the component wave functions alone. So I conclude that the wave function is quite real. Your thoughts?