First published: February 20, 2023
Last revised: November 16, 2024

Oh boy this is gonna be a controversial one, but allow me to indulge. If we consider the whole universe as a closed system, we can imagine it has a wave function that evolves unitarily. However, the moment we consider an observer we need to partition the whole universe into the observer and the rest. And here's the hypothesis: as the observer is entangled with the rest, it could be that consciousness *is* the entanglement.

This idea has some interesting aspects:

1. We don't need to invoke new physics
2. Thanks to the Schmidt decomposition we don't need the brain to be entangled with the whole universe, but with at most as many degrees of freedom as there are in the brain.
3. It would make consciousness not identical to its simulation, unless the simulation consists of the same kind of entanglement (so not a classical simulation).

On the other hand, it is an open question whether at the brains' end there exist quantum degrees of freedom that are as long-lived as conscious processes, i.e. O(100ms).

But what does exactly happen when and after light hits the retina? Which entanglement am I supposed to be experiencing? And what if the light isn't entangled with anything else? Will I still experience it? For example, a candle and a laser pointer emit incoherent and coherent light respectively. Incoherent light (the candle) can be granted benefit of the doubt and considered to be entangled with something else, but coherent light (the laser pointer) is by definition a pure state and therefore not entangled with anything else. Yet we experience both, so what gives? Perhaps the entanglement that matters is the one that is created after the light has hit the retina? This hypothesis has quite a few issues.