My interpretation of QM, so not orthodox

This is another answer I wrote on Quora. I’ve forgotten the question, but the answer is self-explanatory. It doesn’t cover anything new (from me) but it’s more succinct than other posts I’ve written.

I’m not a physicist, but I’m well read in this area and quantum mechanics (QM) has a particular fascination for me.

Someone did a survey at a conference and, from memory, the most popular was still Bohr’s so-called Copenhagen interpretation, which many now call ‘the shut up and calculate school’. I think most physicists no longer believe that consciousness is required to ‘observe’ the outcome of a quantum experiment (like the famous double slit experiment). 

Schrodinger’s famous cat thought experiment was to demonstrate how absurd that is. In his book, What is Life?, Schrodinger asks rhetorically where does the quantum effect become ‘real’. Does it occur in the optic nerve going to the brain? Or does it occur before then or when the person has their ‘Aha’ moment? Most people would now say it happens at the apparatus level, when the isotope decays, even before it affects the cat. 

One of the most popular interpretations seems to be the multiple worlds interpretation (Philip Ball calls it the MWI hypothesis). In this scenario, the universe spits into 2 (or more) so that all possibilities occur in some universe, but you only experience one of them.

There are other interpretations, like David Bohm’s pilot wave and the ‘transaction’ interpretation, which incorporates the time-symmetrical nature of the wave function. But, for the sake of brevity, I’ll discuss Roger Penrose’s, Paul Davies’ and Freeman Dyson’s.

Roger Penrose describes QM in 3 phases: U, R and C (always designated in bold). U is the evolution of the wave function (in Schrodinger’s equation), R is the observation or ‘decoherence’ when the wave function ‘collapses’ (or simply disappears) and C is the classical physics phase. Penrose thinks gravity plays a role in decoherence but I won’t discuss that here. 

Paul Davies argues for John Wheeler’s famous “…participatory universe” in which observers—minds, if you like—are inextricably tied to the concretization of the physical universe emerging from quantum fuzziness over cosmological durations.

This comes from Wheeler’s famous thought experiment that light from a distant quasar could be ‘lensed’ by an intervening massive object, like a galaxy, but we don’t know what path the light takes until it’s observed. This is an extension of his ‘delayed choice’ thought experiment relating to the double slit experiment (later confirmed in a laboratory setting).

Davies discusses this very cogently in an on-line paper and references another paper by Freeman Dyson, where he says, “Dyson concludes that a quantum description cannot be applied to past events.”

Personally, I agree with Dyson that QM describes the future and classical physics describes the past. In other words, I argue that the wave function is in the future, which is why it is never observed. This is consistent with Penrose’s 3 phases, which logically occur in a temporal sequence.

If one takes this approach to Wheeler’s photon from his quasar, it exists in the future of whatever it interacts with, including an observer’s instrument. Let’s assume, hypothetically, that the instrument is the observer’s eye. Because the wave function is time symmetrical the ‘delayed choice’ is really a backwards-in-time pathway to the photon’s source, so the observer sees it instantaneously in the past. In effect, this is the so-called transactional interpretation.

Richard Feynman’s path integral method of QED takes the sum of every path possible (most of which cancel out) to give a probability of where a particle (including a photon) will be observed. If all these paths exist in the future, that’s not a problem; only one of them will exist in the past, observed in retrospect. This is the opposite of the MW interpretation which claims all paths exist simultaneously.

Freeman Dyson comes to the following conclusion: 

“We do not need a human observer to make quantum mechanics work. All we need is a point of reference, to separate past from future, to separate what has happened from what may happen, to separate facts from probabilities.”

The curious thing about that statement is that the ‘point of reference’ is consciousness, because (as Schrodinger pointed out in What is Life?) consciousness is the only thing we know that exists in the continuous present.

This doesn’t make the observer the cause, because the cause is still at the photon’s source. It’s just that consciousness happens to be present in the ‘now’ between the QM future and the classical physics past that Dyson references.

Here is the link to both Davies’ and Dyson’s discussions.