Quantum mechanics lies at the heart of many modern technologies–lasers, superconductors, many forms of computing, cryptography and so on. That’s partly because the theory is so good and well tested to mind boggling accuracy.

And yet, there is trouble at the heart of quantum mechanics and the way we should use it to understand the nature of reality. Perhaps nothing reflects this better than a survey published today by Anton Zeilinger at the University of Vienna and a couple of buddies. These guys have surveyed a group of physicists, philosophers and mathematicians about their views on the foundations of quantum mechanics.

1 Why this poll?
In August 1997, Max Tegmark polled 48 participants of the conference \Fundamental Problems
in Quantum Theory," held at the University of Maryland, Baltimore County, about their favorite
interpretation of quantum mechanics [1]. By Tegmark's own admission, the survey was \highly
informal and unscientific," as \several people voted more than once, many abstained, etc." While
the Copenhagen interpretation gathered the most votes, the many-worlds interpretation turned out
to come in second, prompting Tegmark to declare a \rather striking shift in opinion compared to
the old days when the Copenhagen interpretation reigned supreme."
Today, debates about the foundations of quantum mechanics show no sign of abating. Indeed,
they have only become more lively in the years since Tegmark's poll. Thus, we felt the time had
come to take a new snapshot. A perfect photo opportunity had just presented itself: the conference
\Quantum Physics and the Nature of Reality," held in July 2011 at the International Academy
Traunkirchen, Austria, and organized by one of us (A.Z.). A mix of physicists, philosophers, and
mathematicians had gathered at a former monastery at the shore of Lake Traunsee in Austria
(see Appendix B for a list of participants). We handed the conference participants a prepared
questionnaire with 16 multiple-choice questions covering the main issues and open problems in the
foundations of quantum mechanics. We permitted multiple answers per question to be checked,
because in many cases the different answers were not, and could not be, mutually exclusive.
Just as Tegmark's poll, our poll cannot claim to be representative of the communities at large.
But, as a snapshot, it contains interesting|and in parts even surprising|information. A total
of 33 people turned in their completed questionnaires; of those, 27 stated their main academic
affiliation as physics, 5 as philosophy, and 3 as mathematics (here, too, multiple answers were
allowed). While this is not a huge sample size, it is to our knowledge the most comprehensive poll
of quantum-foundational views ever conducted.1 Also, we were certainly aware of the fact that the
multiple-choice format can sometimes obliterate the all-important nuances: two people may check
the answer \local realism is untenable," and yet mean completely different concepts by each word
in this sentence. This, however, is a small price to pay for the ability to directly tally up the votes
and to analyze correlations between answers.

5 Conclusions
Quantum theory is based on a clear mathematical apparatus, has enormous significance for the natural
sciences, enjoys phenomenal predictive success, and plays a critical role in modern technological
developments. Yet, nearly 90 years after the theory's development, there is still no consensus in the
scientific community regarding the interpretation of the theory's foundational building blocks. Our
poll is an urgent reminder of this peculiar situation.