Edit: I’ve corrected the text to indicate that Jim Baggott actually started out as a chemist, not a physicist. Sorry Jim! But, as a wise man once said, the only real difference is that a physicist studies one atom while a chemist studies two.
A few weeks ago in late November, I had the pleasure of attending the workshop on Quantum Physics and the Nature of Reality organised by Anton Zeilinger and Časlav Brukner. The workshop was held at the International Academy in the idyllic location of Traunkirchen, a small town in Upper Austria, where the Traunstein mountain dominates the sky above the Traunsee lake.
According to the online brochure, “…the former monastery is home to the International Academy and the Summer Academy for Painting. It thus connects the eventful past of a religious centre with the promising future of particle physics.” Appropriately, the workshop was sponsored by the John Templeton Foundation, which supports (perhaps paradoxically) scientific research in addition to theological and religious studies .
The weather was not as accommodating as in the brochure picture above, with stormy grey clouds encroaching over the Traunsee, but our beautiful and cosy lodgings provided the perfect rainy-day atmosphere. There’s nothing like gathering near a fireplace with coffee or tea to do some physics. Much of the discussion centered on questions raised in a recent article, `The Oxford Questions on the foundations of quantum physics’, with a particular focus on the following two questions:
1. What are the most interesting and exciting things you have learned in the last three years?
2. What new findings, developments, impulses are at the heart of your hopes for the future?
This Traunkirchen conference was not the first of its kind – some of you might recall the controversy surrounding Schlossauer, Kofler and Zeilinger’s now infamous poll of the participants at an earlier Traunkirchen conference in 2011. The poll was meant to provide a “snapshot of foundational attitudes towards quantum mechanics”, but as Matt Leifer observed, the evidence merely indicates that “…people who went to a meeting organized by Zeilinger are likely to have views similar to Zeilinger” . Given this background, the present Traunkirchen conference promised to be interesting, with a wide assortment of guests including philosophers and philosophically-inclined physicists, not to mention popular author Jim Baggott, whose latest book `Farewell to Reality: How Fairytale Physics Betrays the Search for Scientific Truth’ goes beyond recent criticisms of String Theory to provide an intelligent critique of similar troubling practices in modern physics as a whole.
I took Jim’s presence at the conference as a positive sign. While most scientists readily acknowledge the importance of communicating with the public (after all, much of our funding does come from public money) those who do take the brave step into the public domain also risk separating themselves from the cutting edge of research and thereby alienating themselves from the very community that they are supposed to represent. As Jim cheerfully remarked, Traunkirchen was his first academic conference since the 80’s, just before he decided to leave his post as an academic chemist and take up an industry job. Despite the long absence, positive reviews of his work from practicing scientists bolstered the relevance of his commentary to the modern physics community, and his presence was well received by the other attendees. Another welcome addition in this vein was Michael Raymer from the University of Oregon, who has taken on the formidable challenge of teaching physics, including quantum mechanics, to university students that have absolutely no background in science. The fact that this could be done effectively is quite a remarkable demonstration of the public’s ability to understand science, if scientists just take the time to explain it to them.
Interestingly, while many of the more philosophically-geared talks tended to get sidetracked or bogged down in technicalities, Jim managed to articulate a clear position against what he called `fairytale physics’ without being tripped up or sidetracked too much by the crowd, which was feeling particularly mischievous after an invigorating breakfast (at one point, Jim was even asked to explain what it means for a thing `to exist’). He raised a few hackles when he turned his attention away from string theory (to which everybody was more than happy to add their own critiques) to black holes, for which he argued that the amount of research far outstripped the attention warranted by empirical evidence. He did not try to argue that research on black holes was unimportant, but rather that the amount of attention given to them in the literature did not seem justified, given that some of the most talked-about features of black holes like Hawking radiation have never been observed. While one might find grounds to disagree with Jim on the topic of black holes, Jim’s talk reminded us that one should always be careful to apply the same criticisms one has of opposing ideas to one’s own pet theories, lest one become a perpetrator of fairytale physics.
The talks by Jess Riedel, Markus Appleby, Danny Greenberger, and George Ellis, among others, were notable for the diversity of preferred interpretations presented, ranging from Riedel boldly taking the existence of a wavefunction of the entire universe for granted, all the way to Ellis’s provocative argument that the usual quantum mechanical description is unlikely to be appropriate even at human scales, let alone astronomical scales. Every viewpoint was respected and carefully analysed by the participants in the discussion that followed. By the end of the conference, however, I sensed that a large contingent of the attendees subscribed to what one might call variants of the `informational interpretation’ of quantum mechanics.
Broadly speaking, informational interpretations tend to have the following points in common:
(i) They regard wave-function collapse to not be a real phenomenon, but more akin to the “collapse” of one’s knowledge upon gaining new information. This idea is elucidated most clearly by the Quantum Bayesians (QBists), but is common to other interpretations as well (certain readings of Bohr’s Copenhagen interpretation run this way).
(ii) While they typically regard the wavefunction as representing information about the expectations of some agent or appropriately defined observer, they do not consider the wavefunction to represent information about some underlying, observer-independent reality. For example, this is in opposition to hidden variable interpretations like the De Broglie-Bohm interpretation.
Note that (i) and (ii) do not preclude a realist view of physics, although this is a point on which the informational views tend to diverge from each other. For example one could take a `realist-instrumentalist’ stance, where the measurement settings and the outcomes produced by the devices (i.e. the objects of our experience), are taken to be real. Alternatively, following Carlo Rovelli, one could take a relational view, in which the relationships between physical systems can be considered `real’. In that case, we identify a physical system as an `observer’, and the wavefunction represents an objective property of the interaction between observer and system. In contrast to both these views, the subjective Bayesian, as embodied by Chris Fuchs, would deny that there are any `elements of reality’ at all. All of these views nevertheless count as informational interpretations by the rough guidelines given above.
Personally, I am sympathetic to the informational approach; hence one should take a grain of salt with my assertion that discussions at the conference supported this view. After all, research on cognitive biases suggests it is possible that I subconsciously accepted information at face value that was compatible with my preferred viewpoint, while seeking reasons to disregard information that opposed it — this could then lead me to think that the talks at the conference favoured the informational interpretation much more than they actually did .
I’ll conclude with some brief comments on Anton Zeilinger’s own philosophical sympathies, as expressed by him in his talk at the end of the conference. As near as I can tell, Zeilinger’s view is similar to the realist-instrumentalist view I mentioned above — the quantum state represents an abstraction of our expectations for what should happen to our instruments in an experiment. The measurement setting and outcomes are real, but the objects that appear in our formulas that connect the settings to the predicted outcomes are not necessarily real things in their own right. Quoth Zeilinger:
“Collapse is at the heart of Quantum Mechanics — it does not represent a breakdown of Quantum Mechanics. […] It is impossible to operationally verify any distinction between reality and information.”
I take this as basically saying that wave function collapse is a change in information, not a change in the `elements of reality’, in accordance with (i). Regarding the question of whether the wavefunction represents information about some underlying reality, he says:
“It is wrong to think there is anything behind the randomness.”
Perhaps the best understanding of the Zeilinger interpretation of QM can be gleaned from his closing remark:
“There are two fundamental freedoms: our freedom to define which measurement apparatus to use and thus to determine which quality can become reality; and Nature’s freedom to give the answer she likes.”
 There was some intriguing discussion about the unease that some physicists feel regarding the religious side of Templeton’s agenda, but I’m postponing a discussion of that topic until I’ve made up my own mind about it. For the moment, I think funding science can only be a good thing in the long run, regardless of whether it is coming from Templeton, Laziridis, Milner, Zuckerberg or Leprechauns.
 To be fair, Zeilinger frequently entertains guests with quite different interpretational attitudes than himself, recent examples being John Cramer, originator of the `transactional interpretaion’, and Lev Vaidman, whose preferred interpretation has a distinct many-worlds flavour, not to mention several attendees of this recent conference.