Je suis, nous sommes Wigner! A perspectival exploration of the Frauchiger–Renner paradox by Malcolm Riddoch

Hi Edwin,

and thanks for checking my essay out, I'm reading through your contribution as we speak and have a couple of questions to ask. Will do that on your entry's thread.

As for taking two weeks to work through my essay it would probably go much faster if you were familiar with the original F-R paper by Daniela Frauchiger and Renato Renner, "Quantum Theory Cannot Consistently Describe the Use of Itself," in Nature Comms.

I take it you would have read George Musser's FQXi article on it?

The equations in my essay aren't proofs for or against the F-R paradox but rather part of the flow of the disjointed Socratic dialogue indicating the thought processes of each agent as they try to accommodate the F-R argument within their different QM viewpoints. At the end of the day I think the F-R paradox is more about how we might conceptualise quantum foundations than it is about the quantum formalism used to illustrate the argument. At least that's how I've approached the problem given my specialty is philosophical thought rather than linear algebra!

As for the scoring system it does seem to have disappeared although it looks like someone's trying to fix the site as FQXi keeps going down every now and then for a reboot.

Hi Luca,

thanks for the comments and I've got your essay first up on my to read list!

"Did I understand your essay right, that you left every one of the actors in their own view? No chance get to an agreement?"

Correct, and that's precisely where quantum foundations is right now don't you think? How do you agree on anything in a debate if everyone is arguing on the basis of apparently incommensurable ontologies?

Where's the common ground between Wbar who believes that physical reality is the underlying singular objective reality upon which we can apply quantum formalisms (with or without hidden variables), and Fbar who is tending towards relative-state based wave function realism?

Or F who is a sort of post-structural Bohrian QBist for whom 'objective reality' is a function of probabilistic beliefs based on an individual's empirical experience, which is precisely how they judge Wbar, Fbar and W's differing beliefs.

And then there's W the practical minded experimentalist who, insofar as they want to think metaphysically at all, wants to believe that wave function collapse is an actual physical event in the micro-world leaving everyone happily classically together in the one physical macro-world.

How does anyone come to any sort of agreement on what QM means when applied to the world of our experience given these orthogonal viewpoints? And then throw them into opposing Wigner-Friend relationships with the implied observer bias and everyone interpreting their position differently - which is where I think the F-R paradox works very nicely in demonstrating exactly the tangled narrative that is contemporary quantum foundations. So no, I do not expect any resolution of this metaphysical tangle any time soon!

"And the narrator? Interestingly the narrator knows from the beginning, what the point of view the actors will have."

Our narrators in the F-R paper are the authors, and Renner makes it very clear that their preferred frame of reference is Wbars 'fleshy qubit' computing angle where the "idea is to substitute agents Fbar and F by computers" (F&R, p. 7). And this just demonstrates the Wigner bias that I'm pointing to, where it's only from the M perspective that the Friends can be thought of as redundant human qubits, whereas from their perspective the W's are both likewise their Friends, but why would you replace the W's with computers?

"But if Wigner interferes with a non compatible measurement, then the friends measurement is not unitary any more. This is like the friend trying to weight something with a sensitive scale and Wigner the giant constantly shakes the lab where the friend is measuring the weight."

So from what physical frame of reference and whose ontology does it make sense to think of Wigner as the giant and the Friends as Lilliputians? I think this is precisely the point I'm trying to tease out in my essay, and Luca, as your own narrator, if you were placed in Lbar and allegedly superposed then Hadamarded from the M perspective would you still not be your own Wigner in your own observable world?

Hi Luca,

I am enjoying engaging with your excellent essay, and yes I think there are many correlations to be had between our closed semantic systems!

"the definition of what is real is underdetermined by observation, since we only have indirect access to objects."

From my perspective, I would perhaps rather say that the strictly empirical definition of what is observationally real is to be determined by observing real rather than imagined objects, unless one is observing the reality of one's own inner imagination of course!

But then I guess if you insist on holding to an ontology for which 'real objects' are only ever indirectly observable then ... so long as you 'wear your ontology on your sleeve' so to speak then all your conclusions should follow logically and transparently from that basis ... and will make perfect sense from within that sematic enclosure ... including your insistence that all observations by all observers "must be objective and unique in one world".

So does that make you a colleague of the W's, and you're sitting against the back wall in my fictional M lab observing the ongoing experiment? And you really want to believe in a single world outcome, that your observable world is nonetheless the indirectly real objective world that every other observer must conform to, even if that means the F's really can be squeezed through a Hadamard gate as if they were fleshy qubits?

Hi Yutaka,

I'd say your question is precisely what my essay is all about! How would you even begin to define what a 'fundamental reference frame' is, in order to then share it with the others?

From the relative state or relational perspective, the fundamental frame is simply the one you're in. For Many Worlds that means self-locating uncertainty rules the day, and your current branch is your current empirical reality relative to all other branches. I can't see how one can apply this to the W's but then not to the F's! They're all on their own branches until they decohere back together in M.

I've assumed that QBist interpretations are sort of similar, in that what you're concerned with is your own probabilistic beliefs about your own empirical experience of the world, and that the others, W's and F's alike, are also free to assign their own credence to what they perceive as the reality of their own situation.

Hidden variables would suggest that the fundamental frame of reference is the real world of which there is just this one physical reality we're all in. From that perspective I have no idea what a Bohmian might make of their own reality in L, there being just the single underlying entangled physical reality between all the labs ... what do you think?

The experimentalist is similar in that when forced to talk metaphysically about the physical reality they experiment with, the real world is just fundamentally the one we all wake up in! I'd say they're much more comfortable in M just getting on with Hadamarding the fleshy qubit side of the experiment from the only fundamental frame of reference that counts ... our very own observable universe!

For me, it's these basic, pre-mathematical, ontological positions that define the various cross purposes against which quantum foundational debates are always struggling--from the very beginnings of the arguments between supporters of Bohr and Einstein at the fifth Solvay Conference if not earlier.

Do we define the fundamental reference frame with respect to an external classical grid-like spacetime reality within which we're all variously situated?

Or do we define the fundamental reference frame with respect to a universal wave function of which we're each of us an entangled sub-system?

Classical realism or wave function realism or a refusal of these externalist metaphysics in favour of post-Bohrian QBism or experimentalist naivete or any other 'fundamental frame of reference' you might want to include?

What's your poison?

Hi Cristinel,

thank you for both of those papers! And as Renner himself said of the only clear outcome of the debate: "Users of quantum theory cannot consistently decide whether the theory can consistently describe its own use."

Regarding the distinction between classical and non-classical states, and the question of wave function collapse, at the moment neither of these notions are accommodated in my personal philosophical picture of QT as, like Fbar, I'm tending much more towards the non-collapse side of things. Salom's use of 'subjective experience' as a way to rescue a 'subjective collapse' interpretation does highlight the perspectival problem the F-R paradox brings out with respect to the Friends' experience. And it's this problem of 'subjective experience' that for me is getting somewhere towards the heart of the paradox.

The Wigner perspective has an implied 'subjective conscious experience' that either isn't called into question or is used as the standard from which the Friends must conform, and it's also the presumed 'subjective' perspective of the Reader and Narrator, which is 'our' perspective here reading and joining in this discussion.

This unquestioned super observer experience/perspective, always in each case one's own, only becomes problematic when we Wigners are forced to consider the 'conscious experience' of the Friends who are otherwise assumed to be simple physical systems evolving unitarily in quantum states that are interchangeable with qubits--which is what Renner explicitly argues.

And I just can't see how if we arbitrarily assign ourselves a 'super observer' Wigner status, how can we then not allow the Friends the same priority from their perspectives? If Wigner is Wigner then we are all Wigner!

But questions such as 'what is subjective experience?' or 'what is consciousness?' are I think red herrings that lead the debate away from the nonetheless related but fundamental question: What is the 'observer' and their 'empirical observational experience'? The original Wigner's Friend argument falls down that philosophy of mind rabbit hole and then you get ridiculous debates about how a thing called 'consciousness' can cause the 'collapse' of unobservable physical quantum states ... which doesn't really advance the debate much past Elisabeth of Bohemia's objections to Descartes' substance dualism over 300 years ago.

For me, the mind-numbing circularity of the F-R paradox isn't anything to do with the quantum formalism but much more to do with the tortured metaphysics and the conceptual bogs we start to drown in as soon as we try and even just simply picture how an observer and their observational experience might be related to whatever the frak a 'quantum state' might be said to be ... in terms of whatever ontology of physical reality one subscribes to.

There seems to be something fundamentally wrong with how we conceive of the 'observer' and thus 'observations'. Everett for example, for all the wonders of his concept of the universal wave function still pictures its observer subsystem as a simple physical automaton which again as a model of 'us observers' isn't much advanced on the Renaissance clockwork automata that so fascinated early modern natural philosophy.

And so it goes on and around, quantum foundations seems to me to be entangled in a tangle of half thought out occidental ontologies and sedimented concepts with ancient, mediaeval and renaissance roots. Which just reflects the state of contemporary philosophy in general. But we have to first work through a tangle in order to dis-entangle our entanglements and things do seem to be loosening up slowly! At least that's as far as my optimism allows me to go :)

Hi SNP,

"So can you list the fundamental concepts to be considered for forming a new theory.....?"

Yes ... and no? While I personally think philosophy is great for looking at things from a widest angle perspective and critically pulling theories apart from there, what you end up with is a lot of disconnected, confused/conflated bits of ontology and open ended questions without any guarantee of ever coming to an overall consistently agreed view ... or even knowing if such an ontological overview is even possible ... or not ... which is also why I think a lot of people find philosophers and philosophy rather annoying--Socrates was fundamentally correct!

So given this fundamental conceptual indeterminacy I'd say 'bootstrapping' is perhaps the second fundamental concept for thinking about quantum foundations.

My own guess as to what comes next would be that first we really need to ditch classical realism concerning an 'external physical reality' ... which probably means that a lot of people will need group therapy philosophy sessions where they all join hands singing Kumbaya as they let go of deeply held early modern superstitions about an unobservable supersensuous world where God is dead but real things nonetheless reside ... and so only with this 'letting go' (Gelassenheit) can we all walk together as one into the brave new 21st C information/theoretic world of structural wave function realism!

And in this vein I prefer observer dependent notions of reality where the observer experience is based on the 'irreducible Heraclitean flux' of phenomenal experience (cf. Husserl) and the 'experiencer' is fundamentally an observational/relational process rather than an observer thing already in a world. A first person perspective that can dynamically reconstitute our 3D+t reality such that space and time are emergent phenomena definitely appeals to my phenomenological biases!

So in this essay contest papers such as Flavio del Santo on intuitionistic/constructive maths, and especially Markus Mueller's notion of ontic structural realism, are standouts for me, along with Sara Imari Walker's work on maths/information/physicality/complexity. It's certainly encouraging to see how far theorising has come just the last 30 years, and the younger generations now appear to have increasingly more freedom to push the boundaries of what's thinkable in quantum foundations without jeopardising their science careers. Should be very interesting to see how far quantum computing pushes that envelope over the next decade!

And how about you? What are your possibly fundamental concepts?

Thanks Alyssa,

and you are much too kind! My little essay is probably a great demonstration of my own confusion regarding the ontological mess that is quantum foundations. But I agree that the observer dependent perspective is looking interesting across a raft of different disciplines dealing with various aspects of our real world.

I've added a comment and question regarding just that to your own excellent essay on Computing Complex Systems. And i'm enjoying the interdisciplinary network here on FQXi, which is exactly what is needed to keep things moving forwards!

Regards,

Malcolm