Last week was the final week of classes, and I brought my ph12b class, aka baby-quantum, to conclusion. Just like the last time I taught the class, I concluded with what should make the students honor the quantum gods – the EPR paradox and Bell’s inequality. Even before these common conundrums of quantum mechanics, the students had already picked up on the trouble with measurement theory and had started hammering me with questions on the “many-worlds interpretation”. The many-worlds interpretation, pioneered by Everett, stipulates that whenever a quantum measurement is made of a state in a quantum superposition, the universe will split into several copies where each possible result will be realized in one of the copies. All results come to pass, but if we are cats, in some universes, we won’t survive to meaow about it.
Questions on the many-worlds interpretation always make me think back to my early student days, when I also obsessed over these issues. In fact, I got so frustrated with the question, that I started having heretic thoughts: What if it is all in our minds? What if the quantum superposition is always there, but maybe evolution had consciousness always zoom in on one possible outcome. Maybe hunting a duck is just easier if the duck is not in a superposition of flying south and swimming in a pond. Of course, this requires that at least you and the duck, and probably other bystanders, all agree on which quantum reality it is that you are operating in. No problem – maybe evolution equipped all of our consciousnesses with the ability to zoom in on a common reality where all of us agree on the results of experiments, but there are other possibilities for this reality, which still live side by side to ‘our’ reality, since – hey – it’s all in our minds!
Doesn’t make sense to you? I can’t blame you. Consider though: many would say that quantum mechanics doesn’t make sense either.
My ‘collapsing mind’ theory has clear drawbacks, but suppose it were true, just imagine the possibilities! It could explain many mysterious phenomena around us. As a first example: The web is full of rumors of people with multiple personalities losing some scar or tumor, as they transition between personalites…* aha! I know what’s wrong – their mind is not ‘collapsing correctly’! The multiple personalities are easily explained as the same personality, just reacting to a quantum reality which is different than the one that the rest of us agree on. By a little. What about Schizophrenia? You guessed it! Hallucinations might just be interpreting sensory stimulus from a different part of the collective wavefunction. In fact, this approach could start a whole new field: “Quantum archeology”. A hallucination might be an exploration of an alternative quantum reality that could have happened – well – happened, but had split off from our common reality some time in the past. Contrasting alternative realities with ours may possibly allow us to interpolate and reconstruct the critical junctures of the evolution of our reality. You see orange men all around? Maybe in a different branch of evolution we did actually turn orange.
As you can hopefully tell, this was not a serious candidate I was proposing to replace the Copenhagen interpretation. At best, I thought of making it into a science fiction story (“mind collapse?”, “Quantumphrenia?”). But then, years later, at the recommendation of my wife, I read a book by the German writer Juli Zeh, “Schilf”. In English it was published under the name ‘In Free Fall’. The book is a detective story which focuses on two physics frenemies. One is an experimentalist who is an ardent believer of the many-worlds interpretation. The other, a CERN theorist, is a complete many-worlds skeptic. One of them commits a nasty murder.
Before the murder, however, the book describes a televised quantum-measurement showdown, and there it appeared out of nowhere – Dieter Zeh and his many-minds interpretation. This caught me by complete surprise, as I thought that at least my science fiction was original, not to mention that I never heard of Zeh before. Wikipedia to the rescue: Dieter Zeh, unrelated to the krimi** author, has indeed proposed the so called ‘many-minds’*** interpretation back in 1970’s. Not only that, he reproduced a 1981 paper from the ‘Epistemological letters’ in the preprint arxiv in 1999 as quant-ph/9908084. There it was, my crazy science fiction idea, come to life! And proven to be consistent – actually, the only consistent – interpretation of quantum mechanics and the many-worlds theory.
Usually I’m upset about being scooped, but somehow I let this one go without too much agony. I sat back and finished reading the book. At least my college quantum measurement escapade turned into a good detective story, even if I didn’t win a Nebula award in the process. The book was the most quantum-physics piece of literature that both me and my wife (a Germanist) could equally enjoy. Quantum measurement was all over the plot. Even the detective that solves the case has a girlfriend which may or may not exist and is constantly fretting about calling her, concerned about collapsing the wavefunction to a reality where she does not exist.
It seems that (J) Zeh, despite being a lawyer by training, hit on something that I thought only us quantum physicists really knew: quantum-measurement theory is nothing less than a matter of life and death and not necessarily only for cats!
* Some examples I found by light googling:
** Criminal novel in German slang
*** Initially the many-consciousness interpretation