Notwithstanding Bohr, the Reasons for QBism

Without Niels Bohr, QBism would be nothing. But QBism is not Bohr. This paper attempts to show that, despite a popular misconception, QBism is no minor tweak to Bohr's interpretation of quantum mechanics. It is something quite distinct. Along the way, we lay out three tenets of QBism in some detail: 1) The Born Rule---the foundation of what quantum theory means for QBism---is a normative statement. It is about the decision-making behavior any individual agent should strive for; it is not a descriptive "law of nature" in the usual sense. 2) All probabilities, including all quantum probabilities, are so subjective they never tell nature what to do. This includes probability-1 assignments. Quantum states thus have no "ontic hold" on the world. 3) Quantum measurement outcomes just are personal experiences for the agent gambling upon them. Particularly, quantum measurement outcomes are not, to paraphrase Bohr, instances of "irreversible amplification in devices whose design is communicable in common language suitably refined by the terminology of classical physics." Finally, an explicit comparison is given between QBism and Bohr with regard to three subjects: a) The issue of the "detached observer" as it arose in a debate between Pauli and Bohr, b) Bohr's reply to Einstein, Podolsky, and Rosen, and c) Bohr's mature notion of "quantum phenomena." At the end, we discuss how Bohr's notion of phenomena may have something to offer the philosophy of William James: A physics from which to further develop his vision of the world---call it an ontology if you will---in which "new being comes in local spots and patches."

[1]  W. Heisenberg.  Physics and Beyond: Encounters and Conversations , 1971 .

[2]  Suzanne Gieser,et al.  The Innermost Kernel: Depth Psychology and Quantum Physics. Wolfgang Pauli's Dialogue with C.G. Jung , 2004 .

[3]  Niels Bohr,et al.  Causality and Complementarity , 1937, Philosophy of Science.

[4]  Thomas Durt.  Symmetric Informationally Complete POVM tomography: theory and applications. , 2007 .

[5]  A. J. Scott.  SICs: Extending the list of solutions , 2017 .

[6]  N. Bohr.  Faraday lecture. Chemistry and the quantum theory of atomic constitution , 1932 .

[7]  James H. Bunn.  Complementarity: Anti-epistemology after Bohr and Derrida , 1995 .

[8]  C. Jung,et al.  Atom and Archetype: The Pauli/Jung Letters, 1932-1958 , 2001 .

[9]  C. Fuchs.  QBism, the Perimeter of Quantum Bayesianism , 2010, 1003.5209.

[10]  Steven Weinberg,et al.  Lectures on Quantum Mechanics: HISTORICAL INTRODUCTION , 2012 .

[11]  Krister Shalm,et al.  A Loophole-Free Test of Local Realism , 2016 .

[12]  Caslav Brukner,et al.  On the Quantum Measurement Problem , 2015, 1507.05255.

[13]  Stephen G. Brush,et al.  The Chimerical Cat: Philosophy of Quantum Mechanics in Historical Perspective , 1980 .

[14]  “Physics as Meaning Circuit”: Three Problems , 1986 .

[15]  N. Bohr,et al.  Light and Life , 1933, Nature.

[16]  W. James.  Pragmatism, A New Name for Some Old Ways of Thinking: Together With Four Related Essays Selected From The Meaning of Truth , 2010 .

[17]  C. Fuchs,et al.  A Quantum-Bayesian Route to Quantum-State Space , 2009, 0912.4252.

[18]  Charles H. Bennett,et al.  Teleporting an unknown quantum state via dual classical and Einstein-Podolsky-Rosen channels. , 1993, Physical review letters.

[19]  William James,et al.  Essays in Radical Empiricism , 1907 .

[20]  Scott Aaronson,et al.  The Ghost in the Quantum Turing Machine , 2013, The Once and Future Turing.

[21]  T. Yamanouchi.  Analysis and Synthesis in Science , 1964 .

[22]  K. V. Laurikainen,et al.  Beyond the Atom: The Philosophical Thought of Wolfgang Pauli , 1988 .

[23]  R. M. Wenley,et al.  Pragmatism, a New Name for Some Old Ways of Thinking: Popular Lectures on Philosophy , 1907 .

[24]  V. Baeyer,et al.  QBism: The Future of Quantum Physics , 2016 .

[25]  D. Albert,et al.  A quantum threat to special relativity. , 2009, Scientific American.

[26]  W. Heisenberg,et al.  Philosophic Problems Of Nuclear Science , 1952 .

[27]  Yemima Ben-menahem.  Dummett vs Bell on quantum mechanics , 1997 .

[28]  Richard Phillips Feynman,et al.  The Concept of Probability in Quantum Mechanics , 1951 .

[29]  Blake C. Stacey,et al.  QBism: Quantum Theory as a Hero's Handbook , 2016, 1612.07308.

[30]  N. Bohr.  Atomic Theory and Mechanics , 1925, Nature.

[31]  D. M. Appleby,et al.  Properties of QBist State Spaces , 2009, 0910.2750.

[32]  C. Fitts,et al.  The Unity of Knowledge , 1952, Nature.

[33]  David Favrholdt.  IV - Physical Science and the Study of Religions , 1999 .

[34]  Gary James Jason,et al.  The Logic of Scientific Discovery , 1988 .

[35]  Isaac L. Chuang,et al.  Quantum Computation and Quantum Information (10th Anniversary edition) , 2011 .

[36]  Carlton M. Caves,et al.  Subjective probability and quantum certainty , 2006 .

[37]  Tim Maudlin,et al.  What Bell did , 2014, 1408.1826.

[38]  Dmitriy Khots,et al.  Probability in quantum theory from observer's mathematics point of view , 2012 .

[39]  Albert Einstein,et al.  Can Quantum-Mechanical Description of Physical Reality Be Considered Complete? , 1935 .

[40]  Christopher A. Fuchs,et al.  Interview with a Quantum Bayesian , 2012, 1207.2141.

[41]  W. Pauli,et al.  Writings on Physics and Philosophy , 2010 .

[42]  Christopher A. Fuchs,et al.  The SIC Question: History and State of Play , 2017, Axioms.

[43]  B G Sidharth,et al.  Law without Law , 2007, 0710.3900.

[44]  Robert W. Spekkens,et al.  Einstein, Incompleteness, and the Epistemic View of Quantum States , 2007, 0706.2661.

[45]  D. Hendrick,et al.  Introduction , 1998, Thorax.

[46]  Christopher A. Fuchs,et al.  On Participatory Realism , 2016, 1601.04360.

[47]  Niels Bohr,et al.  Discussion with Einstein on Epistemological Problems in Atomic Physics , 1996 .

[48]  W. Durant,et al.  The Story of Philosophy: The Lives and Opinions of the Greater Philosophers , 1961 .

[49]  Raymond Klibansky,et al.  Quantum Physics and Philosophy–Causality and Complementarity , 1996 .

[50]  Blake C. Stacey.  Multiscale Structure in Eco-Evolutionary Dynamics , 2015, 1509.02958.

[51]  Arkady Plotnitsky,et al.  Reading Bohr: Physics and Philosophy , 2006 .

[52]  Biology and atomic physics , 1938 .

[53]  John Archibald Wheeler.  World as system self-synthesized by quantum networking , 1988 .

[54]  C. Fuchs.  Quantum Mechanics as Quantum Information (and only a little more) , 2002, quant-ph/0205039.

[55]  J. Stachel.  Einstein from 'B' to 'Z' , 2001 .

[56]  Arthur Fine.  Do correlations need to be explained , 1989 .

[57]  W. James.  A Pluralistic Universe , 2010 .

[58]  S. Wehner,et al.  Loophole-free Bell inequality violation using electron spins separated by 1.3 kilometres , 2015, Nature.

[59]  Ruediger Schack,et al.  Quantum-Bayesian Coherence , 2009, 1301.3274.

[60]  T. Norsen.  John S. Bell’s concept of local causality , 2007, 0707.0401.

[61]  J. Schreiber.  Foundations Of Statistics , 2016 .

[62]  Blake C. Stacey,et al.  Introducing the Qplex: a novel arena for quantum theory , 2016, 1612.03234.

[63]  Argyll.  THE UNITY OF NATURE. , 1881, Science.

[64]  N. Mermin,et al.  Why QBism Is Not the Copenhagen Interpretation and What John Bell Might Have Thought of It , 2014, 1409.2454.

[65]  Ian D. Lawrie,et al.  The emergent multiverse – quantum theory according to the Everett interpretation , 2016 .

[66]  W. James.  The Sentiment of Rationality , 2005 .

[67]  Frank A. Manny,et al.  Some Problems of Philosophy: A Beginning of an Introduction to Philosophy. , 1912 .

[68]  Richard Healey,et al.  Quantum States as Objective Informational Bridges , 2015, Foundations of Physics.

[69]  Abner Shimony,et al.  The Philosophy of Niels Bohr: The Framework of Complementarity , 1985 .

[70]  Nicolas Gisin,et al.  Collapse. What else , 2017, 1701.08300.

[71]  Christopher A. Fuchs,et al.  Coming of Age With Quantum Information - Notes on a Paulian Idea , 2011 .

[72]  Marcus Appleby,et al.  SICs and Algebraic Number Theory , 2017, 1701.05200.

[73]  Berthold-Georg Englert,et al.  On quantum theory , 2013, 1308.5290.

[74]  C. Fuchs,et al.  Quantum probabilities as Bayesian probabilities , 2001, quant-ph/0106133.

[75]  R. Baierlein.  Probability Theory: The Logic of Science , 2004 .

[76]  A. Cabello.  The Unspeakable Why , 2016, 1612.02680.

[77]  N. Bohr.  The Quantum Postulate and the Recent Development of Atomic Theory , 1928, Nature.

[78]  E. T. Jaynesz,et al.  Clearing up Mysteries { the Original Goal , 1989 .

[79]  Niels Bohr,et al.  The Causality Problem in Atomic Physics , 1958 .

[80]  W. Heisenberg.  Physics and Philosophy: The Revolution in Modern Science , 1958 .

[81]  W. James,et al.  The Will to Believe , 1997, Arguing About Knowledge.

[82]  J. Faye.  Niels Bohr: His Heritage and Legacy: An Anti-Realist View of Quantum Mechanics , 1991 .

[83]  Blake C. Stacey.  Von Neumann was not a Quantum Bayesian , 2014, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[84]  J. Brennum,et al.  What is a life worth living? , 2017, Acta Neurochirurgica.

[85]  NIELS BOHR.  Natural Philosophy and Human Cultures , 1939, Nature.

[86]  J. Dewey.  The Postulate of Immediate Empiricism , 2016 .

[87]  Van Fraassen,et al.  Belief and the Will , 1984 .

[88]  N. David Mermin,et al.  An introduction to QBism with an application to the locality of quantum mechanics , 2013, 1311.5253.

[89]  Christopher G. Timpson,et al.  Quantum Bayesianism: A study , 2008, 0804.2047.

[90]  Christopher A. Fuchs,et al.  Group theoretic, lie algebraic and Jordan algebraic formulations of the sic existence problem , 2013, Quantum Inf. Comput..

[91]  Paul Busch,et al.  Lüders Rule , 2009, Compendium of Quantum Physics.

[92]  A. Zeilinger,et al.  Significant-Loophole-Free Test of Bell's Theorem with Entangled Photons. , 2015, Physical review letters.

[93]  W. Heisenberg,et al.  Across the Frontiers. , 1965, British medical journal.

[94]  C. Fuchs,et al.  Unknown Quantum States: The Quantum de Finetti Representation , 2001, quant-ph/0104088.