The End Of Physics As We Know It? | Award Winning Physicists Make Quantum Mechanics Even More Weird

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Prof. Dr. Caslav Brukner, Prof. Dr. Renato Renner and Prof. Dr. Eric Cavalcanti just won the Paul Ehrenfest Best Paper Award for Quantum Foundations. Their different no-go theorems make us reconsider the fundamental nature of reality. Bell's theorem in quantum mechanics already confronted us with the fact that locality and 'physical realism,' in the sense that particles have predetermined physical properties prior to measurement, cannot both be true. But in certain variations of the Wigner's Friend thought experiment an additional metaphysical assumption is now also put in question: the absoluteness of facts. In different words: can we safely assume that a measurement outcome for one observer is a measurement for all observers?

Chapters:
00:00 Introduction: The end of physics as we know it?
16:12 Start of the interview
17:30 Caslav Brukner on Bell and Wigner's Friend
20:32 Renato Renner on how Quantum Mechanics cannot consistently describe the use of itself...
23:59 Eric Cavalcanti on Experimental Metaphysics
26:15 On the progression of metaphysics in physics since Einstein
27:01 Is the question that we either have to give up locality or realism? And Cavalcanti nuancing the world 'realism'
30:54 Renner and Brukner on how to define 'realism'
34:21 Can we assign reality to the observations of different observers?
35:48 Even loophole free Bell test make assumptions, namely that from a certain time an outcome exists.
36:44 Aren't we here doubting the very enterprise of physics?
38:41 Maybe Bell's inequalities won't be violated if we do the tests with human observers...
40:54 On how the proposed experiments differ from Bell experiments.
45:20 Brukner on direct experience and the reality status we assign to it, intersubjectivity
50:57 Renner on how we have to get used to counter intuitive idea that facts might not be absolute
54:19 In general relativity you could still 'patch' different reference frames together. Now the events themselves are relative...
56:13 The relationship with many worlds interpretation
59:27 In Einstein's universe we could still look at it from the outside...
1:03:43 Where do you place the boundary between classical and quantum
1:11:38 None of the existing interpretations of QM gives a satisfying answer...
1:16:41 What about the difference between ontic and epistemic interpretations of QM?
1:20:06 Renato Renner on QBism
1:22:37 What philosophers capture this?
1:24:53 Where to place the Heisenberg cut?
1:28:41 What role has consciousness to play?
1:37:49 Does consciousness sit at the end of a causal chain in our universe?
1:45:05 On the role of qualia and is our universe a collection of views upon itself?
1:48:45 Hans wrapping it up from his perspective

1:49:57 Intro to the conference lectures
1:51:13 Paul Ehrenfest Best Paper Award Ceremony
1:56:14 Caslav Brukner Conference Presentation: What Happens?
2:25:32 Eric Cavalcanti Conference Presentation: The Local Friendliness Research Program
2:45:49 Renato Renner Conference Presentation: 'Quantum Theory Cannot Describe the use of Itself

These recordings were made possible thanks to the Institute for Quantum Optics and Information (IQOQI) in Vienna, co-founded by Nobel Laureate Anton Zeilinger:

The website of the conference featured in this video:


The Award Winning Papers:
Č. Brukner, A no-go theorem for observer-independent facts, Entropy 20, 350 (2018),

D. Frauchiger and R. Renner, Quantum theory cannot consistently describe the use of itself, Nature Communications 9, 3711 (2018),

K.-W. Bong, A. Utreras-Alarcón, F. Ghafari, Y.-C. Liang, N. Tischler, E. G. Cavalcanti, G. J. Pryde, and H. M. Wiseman, A strong no-go theorem on the Wigner’s friend paradox, Nature Physics 16, 1199–1205 (2020),

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