I get the New Scientist magazine every week. The front cover usually shows the headline of the main feature inside. Often, this describes a fundamental idea about quantum theory, newly published on arXiv or in one of the print journals. This probably shouldn’t be surprising, in spite of the fact that the theory’s roots are a century old, because quantum mechanics is so unintuitive that no “explanation” has ever met with universal approval, and always invites a flurry of counter-explanations.
The cover of this week’s magazine is prompted by two recent papers by Daniel Sudarsky and his co-workers. The hook, that reality might not exist without us, refers to “objective collapse” of the wave function, which Sudarsky uses in his work.
Some physicists and philosophers believe that the Copenhagen interpretation of quantum mechanics requires a “measurement” by a “conscious observer” before the wave function will collapse into a definite state. Objective collapse gets round this by positing a small but finite chance of the wave function of any particle collapsing without the need for an observer, rather as in the process of radioactive decay. In a large collection of such particles, the collapse of the wave function of just one of them will trigger the rest to collapse also, because the particles will be entangled.
I was never one of those who thought the Copenhagen interpretation required an actual measurement, let alone by a conscious observer. I presumed that merely interacting with some other object in the environment would be sufficient to collapse the putative wave function. Be that as it may, my argument that the wave function is not real still stands (see Wave Function Collapse): the wave function is merely a way to calculate the probability that a given version of you is in a universe featuring a particular outcome of a quantum event.
So I am still unmoved by the reality behind the intriguing headline on the cover of my New Scientist.