In the September 2018 issue of Nature, two physicists, Daniela Frauchiger and Renato Renner, describe a thought experiment in which two different “observers” — say two people — each perform an experiment, independently — but on the same thing, which is a system that is in a “quantum state”. A quantum state is one in which one can fully characterize the quantum parameters of the system. Generally only small groups of particles that are isolated from other particles can be put into a quantum state.
The catch of the thought experiment is that one observer is also observing the experimental results of the other, as their “experiment”.
It is important to note that the observer — the human being — cannot be treated as part of a quantum system. A human being is a macroscopic entity, whose quantum state cannot be characterized. This is because a human body consists of billions of separate atoms, interacting with each other continuously. It is not possible to know the quantum state of each atom individually because there is too much randomness, with the atoms bumping into each other all the time.
This is why Schodinger’s paradox is not actually possible: a cat cannot be in a quantum state, because one cannot know the full wave function of the cat’s many atoms. If a particle in a quantum state interacts with a cat, the particle is immediately subsumed into the macroscopic state of the cat, which will be definitively in a state of being alive or being dead.
But one can, in theory, define the quantum state of the equipment of a human observer — or a cat — if the equipment is controlled enough. That’s a detail, but a very important one.
The authors analyze this setup, and discover that quantum theory tells them that each of the experimenters can observe a different result.
In August of this year (2020), a team of physicists reported on an experiment that largely validates the thought experiment of Frauchiger and Renner.
Imagine a macroscopic equivalent: you measure the length of a table and get 30 cm, and another person then measures the same table and gets 60 cm.
We view this as impossible, yet that is essentially what is happening in the experiment.
The philosophical implications of this are immense:
Reality is subjective. There is no absolute reality.
A scientific role for consciousness?
Quantum theory is the first scientific theory in the history of humanity that hints at a role for consciousness. It is referred to as “the observer”. Debates raged in the early days, and still do, as to whether the “observer” is an aspect of the system being observed — a “collapsing wave function” — or an aspect of the observer — a “consciousness”, apart from what is being observed.
It seems that the latter is the case.
I say “seems” because nothing here is certain: we cannot trust that we are even capable of understanding the depth of the true reality of the universe. Perhaps we are like fish in a bowl, incapable of understanding what is beyond the bowl. But that should not stop us from trying! — so here goes:
The experiment by Kok-Wei Bong et. al. seems to imply that consciousness is not part of the universe that we observe. It is part of some universe — but it is not part of the stuff that we see, measure, etc. The universe that we see and measure is a subset of what is there — if it is even “there” at all, in a sense apart from our consciousness. Our consciousness — or whatever gives rise to it, is separate from the universe that is described by our equations and experienced by our perceptions.
To put it another way, it appears that a consciousness selects or creates a reality; and separate consciousnesses may select (or create) different — even inconsistent — realities.
That would seem to mean that reality does not give rise to consciousness; but rather it is the other way around: that either (a) consciousness gives rise to reality; or (b) consciousness and reality are two sides of a single phenomenon — that reality and consciousness arise together and are inseparable, like two sides of a coin.
In other words, consciousness either chooses (or constructs) a reality, or consciousness is that choosing (or construction).
We don’t know how the choosing (or construction) takes place; but this seems to put to bed assertions by some — perhaps most famously Steven Weinberg — that consciousness is an illusion; since if it were, then every observation of a quantum system would merely result in quantum entanglement — there would be no selection (or construction) of a reality. Instead, the observation would merely produce a more complex, composite wave function. There would be no need for a single outcome to be selected above any other. Yet a single outcome is what conscious beings experience.
Even scientists do not have agreement on what an “observation” really is. Some contend that it is a conscious observation; others claim that consciousness has nothing to do with it — that it is “interference” from the environment that is what causes a quantum state to “decohere” into a “macroscopic” state — turning an object from a “quantum object” into just a plain old ordinary object like we are all familiar with.
But that view confuses two separate phenomena: collapse and decoherence. A quantum state “collapse” is really a transition to another quantum state, by the action of an observer. For example, suppose that a particle is in a superposition of two states: one state with spin “up” and the other state with spin “down”. If the particle passes through a magnetic field, then at some point it will interact with a photon (because a magnetic field is a manifestation of the electromagnetic force, for which photons are the conveyer of the force). To an observer, the interaction will cause the particle to “choose” an up or down state, and so from that moment on, the particle will be in a single state of up or down. Thus, its superposition “collapsed”, but this was really just the transition from one quantum state to another. Yet if there was no observer recording the choice of the particle, the particle will still be in a superposition state, but now involving the magnetic field.
In contrast, if a particle that is in a known quantum state is subject to interference, say by collision with a random gas molecule, the state of the particle will become indeterminate. In fact, its state explodes — physicists say that it “decoheres” — the state of the combined system takes on a vast number of possible values, making it essentially unknowable. In that case, the particle has been subsumed into the macroscopic state of the gas to which the gas molecule belongs.
Thus, observation of a quantum state — aka “collapse” — and interference by external sources are two very different ways that a carefully created quantum superposition state can be ruined.
To summarize, when something “interferes” with a quantum system, it adds randomness, and in the process the size of the “state space” explodes — so much that we can no longer say what its state is. All we can then do is measure “macroscopic” parameters such as average position and temperature, the latter being essentially an average of the energy of all of the particles.
It is like with entropy. Imagine that you have a set of particles, each confined to its own isolated quantum “box”. You can compute the quantum wave function of that system: its state. Its state has measurement indeterminacy because it is a wave function, but you can write that wave function precisely: it is the sum of the wave function of each separate particle.
But suppose you then release the particles so that they are all now in a single box. You can no longer write the wave function: it is too complex — there is too much randomness. It has become a macroscopic object. In statistical physics we say that the entropy has increased: the size of the state space has increased. That’s what happens when a quantum system “decoheres” so that you can no longer treat it as a quantum system: you lose track of its quantum state. Thus, the inexorable rise of entropy has to do with the explosion of quantum states as particles interact.
The size of the system — the number of particles — is theoretically irrelevant. Destroying a wave function through interference is just the process of losing track of all of the individual particles, so that one can then only treat it as an aggregate system — a macroscopic system. It means that we lost knowledge of the wave function of each particle. So we are back to awareness — to consciousness. The particles are still there — they have wave functions — we just don’t know what they are.
Consciousness is not an illusion; and we don’t need the multiverse
All this seems to make the “multiverse” interpretation of quantum theory, first proposed by the physicist Hugh Everett, less necessary. In that interpretation, each physical event — each “observation” — “splits” the universe into a branch for every possible outcome. I have never liked the theory because it does not say where the energy comes from to create a whole new universe for each quantum event.
But if a consciousness selects (or constructs) a reality, then we no longer need the splitting: there is a selection (or construction) process instead, and that suffices — a new universe need not be created.
We don’t know how this selection (or construction) occurs. We have no clue what it means, or what mechanism drives it. All we know is that we — our observations — are at the center of it.
There are additional possible implications of this. It would seem to mean that causality, which is the irreversible progression of observed events, is somehow an evolution of consciousness. But as Stephen Wolfram has convincingly conjectured, time seems to be nothing more than an ever-expanding tree of “causal” events. And if that is the case, then our new understanding of consciousness must lead us to conclude that consciousness is an ever-expanding tree of reality selections, or reality constructions.
But if time is merely the progression of events, then in what dimension is consciousness evolving? In what dimension is it growing its event tree? It would seem to mean that there is another dimension: one in which the reality constructed or selected by each consciousness evolves over what? — not over time, but over some other dimension — some other degree of freedom.
Perhaps each consciousness is that degree of freedom: perhaps it is the degree of freedom in which an event tree evolves. Perhaps two consciousnesses each propagate through their own respective dimension — their own tree of causality — until they intersect, at which point the causal trees that are inconsistent fall away.
We had it backwards
All this time — for thousands of years — we had it backwards. We thought that the universe started somehow — from a singularity according to cosmologists, although they admit that that was not actually possible — and life evolved, and then consciousness somehow emerged from that.
Instead, it seems that consciousness might be what is here a-priori, and it somehow creates the world around it. The quantum-to-macroscopic transition is still a confounding puzzle, but at least at a quantum level, consciousness seems like it might somehow be a determiner of reality, rather than an “observer”.
The only constraint seems to be that each of us has observed the same thing when we compare notes — but if we don’t compare notes — if our causal trees do not intersect — then our realities can be different. At least in terms of our observations of quantum systems.
Again I repeat that how or if this extends to macroscopic systems — systems that we lack quantum state information about — is unclear. True, we cannot define the quantum state of a macroscopic object, because we do not know the state of its atoms. That lack of information is the key: the statistics of large numbers is what makes the macroscopic world seem deterministic. But there is always a vanishingly tiny chance that it will transition in an unexpected way, in violation of macroscopic physical laws. It is not clear if we can create a macroscopic system that sits on the edge of a quantum knife so to speak: one that is like an actual Schrodinger’s cat — an object that is in an actual superposition. We would have to carefully arrange the statistics of its atoms, so that they are on the verge of a cascade that would be macroscopically visible.
Even if we manage to do that, it still does not tell us that the world around us is ruled by our consciousness. Instead, it seems to be ruled by statistics, and the advance of entropy — of decreasing knowledge about the quantum state of everything around us. We are still “observing”, but not controlling the world: the statistics are such that the range of possible outcomes is so narrow that our observation makes no difference in the outcome.
A thought experiment: if consciousness rules all
Let’s do a thought experiment. Let’s consider what it would mean if the “observer” extends in some way to macroscopic systems: that consciousness is somehow in the driver’s seat, instead of merely being along for the ride. Even if observing does not change macroscopic outcomes, perhaps an “observer” is still selecting (or constructing) the world that they perceive from a very large set of indistinguishable choices.
One objection to this interpretation of things is that the universe is so rich with detail, that how could a consciousness conjure all that? But it turns out that the human mind — or, what we think is the human mind since now we suspect that that is merely a construct — actually takes in very little data. Despite the detail of our visual field, the amount of information transferred from the eye to the brain is very low, on account of the fact that the visual system encodes and transmits only changes to the visual field, instead of transmitting the entire visual field.
Further, people’s attention and memories are not detailed. The mind focuses on a very small portion of what it is looking at — all the detail that we think is there in the periphery is actually a very fuzzy model that our mind maintains, and we can miss even large things that we are not focused on.
If only consistency between observers who “compare notes” matters, then there is not a-lot of information involved. Consider that prodigious sources of data such as the Large Hadron Collider never actually present all that data to a human mind: most of it gets processed by computers. The constraint on consistency between observers who “compare notes” only applies to what those minds actually observe — not to the data that is believed to pass through their equipment.
But then we remember that these are macroscopic things; so they must be “real” — but only in the sense that our observation selected (or constructed) that reality from a large set of nearly identical possible realities — possible wave functions of the macroscopic system. So we are still selecting (or constructing) — it is just that our choices are all nearly identical.
A hint that something lies beyond
All this gives hope to those who seek an afterlife (who would not like that?) It means that consciousness might somehow be the most important part of the universe. And if that is true, then it would not make sense — to a mere human mind anyway — that consciousness would just dissipate when someone dies. If consciousnesses was here first, and a consciousness creates or selects reality, then if it dies, then there is no need for a reality!
And so apart from any religion, science now hints to us that there might be something beyond our existence — a consciousness fountain or machine that is not visible to us — and that the essence of us — our consciousness — might actually exist in some way for eternity.
Perhaps it is by design that we have no memory or view of our larger existence: for if we did — if we had memory of existences stretching to infinity — then we might either see it as futile or go mad…