I know I shouldn't try, but.. I guess I'm a glutton for punishment.

The concepts of "wavefunction" and "wavefunction collapse" (or "quantum state collapse") themselves are analogs of the mathematical properties we do know do apply.

For example, in the double-slit experiment, because the interference pattern occurs even when individual quanta are passed through –– easily implemented with photons and electrons, but applies to all quanta –– we know that each individual quanta passes through

*both* slits. That in fact, it is what we call the wavefunction that passes through the slits. It is not strictly speaking a probability distribution: although the squared wavefunction amplitude correlates to the statistical distribution of the measurables, due to the interference in the individual quanta double-slit experiment, it does have to pass through both slits at the same time.

If we add any kind of interaction that determines which slit a quanta passed through, the interference vanishes. This is what we call a wavefunction collapse.

The key thing to realize is that in the default double-slit experiment, the quanta interacts with the double slit as a wavefunction: it really passes through both slits. When we modify the interaction so that the quanta is localized to either slit passing through, the interference vanishes, and the wavefunction "collapses" to a particle (according to the probability distribution of the wavefunction magnitude squared).

(In general "wavefunction collapse" or "quantum state collapse" refers to an interaction which causes one or more properties to "collapse" to a real measurable value, with probabilities described by the square of the wavefunction amplitude.)

We have no fucking idea whether wave functions are real, whether wavefunction collapse is real, or whether these are just "side effects" of the mathematical representation we currently use for these. Really.

We do know that the mathematical models work so well that we haven't been able to "break" them yet. But they don't tell us what or why, only how.

Let's consider the situation where a photon hits some solid matter.

In most cases, the photon hits one of the outer electrons bound to an atom. Mathematically, the interaction is not between two point-like objects that pick a random location and properties according to their wave function, but between the two wave functions directly. Now, if you look at it statistically, they

*seem* to be the same thing, but they are not: just like in the double-slit experiment, you get "extra" effects compared to the statistical-particle-approach.

When a photon hits a regular lattice or a large molecule with many electrons bound to the lattice or molecule instead of particular electrons in it, the photon essentially interacts with

*all* those electrons at once –– even though usually a single electron will change state due to the added energy. (Again, you could model this statistically assuming the photon interacts with a random electron, but things like

*inverse Compton scattering*, where the photon gains energy and the electron(s) lose energy, and in general how the properties of the electron state change reflect the entire set of electrons and not that particular electron, indicates it is a simplification, and to capture the phenomena correctly, one must look at how the wavefunctions interact –– and not just how "collapsed wavefunctions" could interact.)

When two electrons interact, for example when you have two neutral hydrogen atoms approaching each other, the bound electrons do not interact as point-like particles: to model the interaction correctly, you must integrate the charge density according to the square of the wavefunction amplitudes –– as if you considered all possible electron-electron pairs over an empty universe except for the two, and calculated the overall probability density. However, the statistical interpretation is not exactly correct, because the end result will still act like a wavefunction in double-slit type experiments. In other words, such interaction does not cause a "wavefunction collapse".

Now, if you start asking "okay, exactly what does cause a wavefunction collapse", you get into the la-la land, into

Wigner's friend the Ultimate Observer and such. We don't know, and we cannot know until we understand what the fuck the mathematical construct we call a wavefunction corresponds to in reality, and what wavefunction collapse is, if it is not just a mathematical construct.

Thing is, those of us who are only interested in

*applying* these things to create interesting stuff (like

quantum dots to LEDs, solar cells, transistors, et cetera), don't need to understand

*what*; only

*how*.

To some, this is extremely easy, and to others, extremely hard. It is like considering in mutually exclusive statements, and not rejecting any of them, but forming an opinion weighted by their instant probabilities from moment to moment, situation to situation. Easy to some, impossible for others.

Analogs and simplifications very often suffice to get stuff done, although one must understand they are just that, and not over-extend them; which is why the first thing anyone applying physical models to solve a problem should ask after getting some results is

*"does this make any sense?"*Indeed, in my opinion, true physics doesn't provide any human-scale/human-understandable/intuitive explanations of

*what* or

*why* at all, only

*how*, and that via mathematical models; math being the most precise language to express such things in.

There is an aphorism,

*"Perfect is the enemy of good"*, reflecting that striving for perfection often prevents implementation of smaller improvements; and that since perfectness is rarely achievable, effort is wasted and improvements lost.

My own attitude towards physics is similar. I like philosophical ponderings at least as much as the next person (especially along the von Neumann-Wigner interpretation), but to me, they are human philosophy and not physics. When it comes to science and engineering, better modeling of the ways we can interact with the measurable reality is what matters to me; not which authority or Big Name you follow, or whose ideas you like best. Unfortunately, even physics discussions often devolve into just that, and in my opinion, it is a pure waste of time, when one could discuss

*how* known physics could be utilized if we had enough energy and sufficiently high tech gadgets at hand.

As to the question in the title, the answer is that

*"according to the best current models of measurable reality, no; instant information transfer is not possible"*. Others have expanded on the details, but the key point is that everything we currently know about the properties of "wavefunction collapse" indicates it cannot

*transfer* any information: you cannot "force" the collapse to occur in a specific way, so that another party measuring its entangled partner would make a specific measurement.

Think of it this way: you have a pair of (almost infinite-faced) magic dice, that you know will show the same faces next time they're thrown, and they can only be thrown that one time. You give one to someone moving far, far away. Can you use them to communicate anything? No, because you cannot even tell which one of you threw the dice first. You cannot tell if the other side has thrown the dice yet, because you need to throw it yourself to find out. You cannot "peek" at the face either, because that counts as a throw too. Everything we know thus far about such situations in physics says it is impossible to convey any message, not even a single bit, with such magic dice. Or entangled particles.

(Here, "throwing" corresponds to the wavefunction collapse between the entangled pair, and the face corresponds to the entangled physical measurable, like

spin.)

But again, that is just an analog; the best one that I can construct based on the mathematical description of entanglement. So, you can poke holes in it, easy. To me, its purpose is to give a rough intuitive understanding of the limitations here, not a precise one, because the rough one suffices for purposes of making new interesting stuff. Researchers and scientists, you need to look at the math instead.