Christopher A. Fuchs

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Christopher A. Fuchs
Cris.AFuchs.png
Fuchs during an interview with Essentia Foundation
Born
Cuero, Texas, United States
Education University of Texas at Austin (BS, Mathematics & Physics)
University of New Mexico (PhD, Physics)
Known for QBism
Quantum information theory
Quantum foundations
AwardsInternational Quantum Communication Award (2010)
Fellow of the American Physical Society (2012)
Chancellor's Award for Distinguished Scholarship, UMass Boston (2021)
Scientific career
Fields Quantum information science, Quantum foundations
Institutions University of Massachusetts Boston (current)
Bell Labs
Perimeter Institute for Theoretical Physics
Raytheon BBN Technologies
Thesis Distinguishability and Accessible Information in Quantum Theory (1996)
Doctoral advisor Carlton M. Caves

Christopher Alan Fuchs (born in Cuero, Texas) is an American theoretical physicist whose work focuses on quantum information theory and the foundations of quantum mechanics. He is a professor of physics at the University of Massachusetts Boston. [1] [2] Fuchs is known for technical work in quantum information theory and for co-developing QBism, [3] [4] [5] an interpretation of quantum mechanics that radically departs from conventional approaches by treating quantum states as personal probability assignments an agent uses to calculate expectations about the outcomes of their own experimental interventions.

Contents

Fuchs' current work includes research into symmetric informationally complete measurements (SIC-POVMs), which QBism uses to represent quantum states as probability distributions in a framework where the Born rule appears as a modification of the classical law of total probability.

He is a Fellow of the American Physical Society. [6]

Education and career

Fuchs was born in Cuero, Texas. He received two Bachelor of Science degrees, in physics and mathematics, both with high honors, from the University of Texas at Austin in 1987, where he studied under John Archibald Wheeler. [1] [7] In 1996 [8] he completed his Ph.D. in physics at the University of New Mexico under the supervision of Carlton M. Caves. [1] Michael Nielsen and Isaac Chuang's textbook Quantum Computation and Quantum Information would later recommend Fuchs' PhD thesis as providing "a wealth of material on distance measures for quantum information". [9]

After completing his doctorate, Fuchs held several postdoctoral positions, including the Lee A. DuBridge Prize Postdoctoral Fellowship at the California Institute of Technology (Caltech). He later worked as a member of the technical staff at Bell Laboratories in Murray Hill, New Jersey. [1] [10] [11] From 2007 to 2013 Fuchs served as a senior researcher at the Perimeter Institute for Theoretical Physics in Waterloo, Canada, a centre devoted to research in theoretical physics, particularly in areas such as cosmology and quantum foundations. [12] [13] From 2013 to 2014 he was a senior scientist at Raytheon BBN Technologies in Cambridge, Massachusetts. [1]

Since 2015 he has been a professor of physics at the University of Massachusetts Boston, where he leads a research group dedicated to quantum foundations and quantum information theory. The group works on the development and study of QBism and on the analysis of related mathematical structures, such as SIC-POVMs, used in probabilistic formulations of quantum mechanics. [1] [14] [15]

Early contributions to quantum information

In the field of quantum information theory, Fuchs has worked on measures of fidelity and distinguishability for quantum states, bounds on accessible information, and relations between disturbance and information in quantum measurements. Some of these results appear in his doctoral thesis and in later work on quantum cryptography and quantum communication. [16] [17]

Fuchs and Jeroen van de Graaf introduced two-sided bounds connecting trace distance and fidelity, now called the Fuchs–van de Graaf inequalities. They are widely used in literature for converting error and fidelity bounds in the analysis of quantum protocols. [18] [19]

Fuchs also collaborated in proving the no-broadcasting theorem, a generalization of the no-cloning theorem. [20] [21] Together with Carlton Caves and Rüdiger Schack, he developed a quantum version of de Finetti's theorem. [22]

He was one of the originators of the concept now known as an unextendible product basis, sets of quantum states that prove by example that the Peres–Horodecki criterion for entanglement is necessary but not sufficient. [23] [24] Together with Charles H. Bennett and John Smolin, he posed the conjecture that the classical capacity of a noisy quantum channel can be increased by entangled codings, [25] [26] a result eventually established by Matthew Hastings. [27]

In May 2000, when Fuchs was a postdoc at the Los Alamos National Laboratory, his home and most of his family's possessions were destroyed in the Cerro Grande Fire. [28] Fuchs had been actively corresponding over email with many prominent figures in the then-nascent field of quantum information. In an example of what he called "backing up my hard drive", he posted an edited collection of this correspondence to the arXiv preprint server, with a foreword by N. David Mermin. Later, Växjö University Press printed a limited edition of this collection, and in 2011, Cambridge University Press printed it (with a new introduction) under the title Coming of Age with Quantum Information. [29] [30] [31]

QBism

QBism is an interpretation of quantum mechanics that regards the theory as a tool for each agent to evaluate and update their expectations about the outcomes of their own actions on the world. [32] [33] [34] In this view, the quantum state is not understood as an objective property of a system, but as a mathematical expression of an agent’s beliefs about that system. From this perspective, quantum mechanics does not describe a reality independent of the observer; instead, it provides a normative framework for decision-making. In QBism, measurement is conceived as an action carried out by an agent upon the external world, with the outcome identified as the experience that action elicits for that agent. The outcome is not regarded as the disclosure of a pre-existing, observer-independent value, but as the product of a particular interaction between the agent and the system. [35] [36] [37] Within QBism, probability is treated in a subjectivist, personalist sense, in the tradition of de Finetti, with Dutch-book coherence used as a criterion of rationality. Coherence justifies the standard rules of probability as normative constraints on an agent's gambling commitments, while quantum theory adds further normative structure tailored to a quantum world. [38]

From the QBist point of view, a formalism was developed that allows standard quantum states to be replaced by the distributions associated with the outcomes of reference devices defined by informationally complete measurements. [39] Under this approach, quantum states are interpreted as expressions of belief. Within this framework, the Born rule is not interpreted as a law of nature that determines which outcomes occur, but as a normative rule: a constraint that an agent adopts in order to maintain internal coherence among their personal probability assignments. The rule links an agent's probability assignments for the outcomes of an informationally complete reference measurement with their assignments for the outcomes of any other possible measurement. [40] [41] [42]

This constraint takes its simplest form when the reference measurement is a symmetric informationally complete measurement (SIC-POVM), [43] a type of POVM first studied by Gerhard Zauner. [44] This makes SIC-POVMs of interest to the QBist program. [45] [46] [47]

Honors and awards

Media coverage

Christopher Fuchs’s work on the foundations of quantum mechanics and quantum information theory has attracted sustained attention in both scientific and general-interest media. His research and interpretive views have been discussed in major international outlets such as The Wall Street Journal , [54] [55] Aeon , [56] and National Public Radio. [57] Extended profiles, interviews, and feature articles examining his contributions and their implications for the interpretation of quantum mechanics have appeared in Vox , [5] Scientific American , [58] Quanta , [4] Discover Magazine , [59] Nautilus , [60] [61] Science, [7] the Frankfurter Allgemeine Sonntagszeitung , [62] and other publications. [63]

Fuchs and QBism were profiled in a 2014 episode of Morgan Freeman's documentary series Through the Wormhole. [64]

References

  1. 1 2 3 4 5 6 "Christopher Fuchs – Curriculum Vitae" (PDF). Center for Quantum Information and Control, University of New Mexico.
  2. ↑ "Christopher A. Fuchs". University of Massachusetts Boston.
  3. ↑ Falk, Dan (25 September 2024). "Could the "QBism" interpretation solve many of the paradoxes of quantum mechanics?". First Principles. Retrieved 27 November 2025.
  4. 1 2 Gefter, Amanda (4 June 2015). "A Private View of Quantum Reality". Quanta Magazine. Retrieved 27 November 2025.
  5. 1 2 Walsh, Bryan (29 November 2023). "Christopher Fuchs is revolutionizing how we understand our quantum reality". Vox. Retrieved 27 November 2025.
  6. 1 2 "APS Fellow Archive – Christopher A. Fuchs". American Physical Society.
  7. 1 2 Savitsky, Zack (December 4, 2025). "Putting the U in Quantum". Science. Retrieved December 12, 2025.
  8. ↑ Fuchs, Christopher A. (1995). Distinguishability and Accessible Information in Quantum Theory (PhD thesis). University of New Mexico. arXiv: quant-ph/9601020 .
  9. ↑ Nielsen, Michael A.; Chuang, Isaac L. (2010). Quantum Computation and Quantum Information (10th anniversary ed.). Cambridge: Cambridge University Press. p. 424. ISBN   978-1-107-00217-3.
  10. ↑ Fuchs, Christopher (November 2003). "Soul-searching at Caltech". Physics World. 16 (11): 49–49. doi:10.1088/2058-7058/16/11/38.
  11. ↑ Preskill, John (2012-08-01). "Alesha". Quantum Frontiers. Institute for Quantum Information and Matter, Caltech. Retrieved 2025-12-13.
  12. ↑ Wells, Paul (27 September 2010). "Solving the universe". Maclean's Magazine. Vol. 123. pp. 17–24. Retrieved December 13, 2025.
  13. ↑ Siegfried, Tom (2012-03-23). "Bits of Reality". Science News . Retrieved 2025-12-13.
  14. ↑ "Professor Christopher Fuchs". SheQuantum. 2019.
  15. ↑ Fuchs, Christopher A. "QBism Research Group". University of Massachusetts Boston.
  16. ↑ Fuchs, Christopher A.; Peres, Asher (April 1, 1996). "Quantum-State Disturbance versus Information Gain: Uncertainty Relations for Quantum Information". Physical Review A. 53 (4): 2038–2045. arXiv: quant-ph/9512023 . doi:10.1103/PhysRevA.53.2038.
  17. ↑ Gisin, Nicolas; Ribordy, Grégoire; Tittel, Wolfgang; Zbinden, Hugo (March 8, 2002). "Quantum cryptography". Reviews of Modern Physics. 74 145. arXiv: quant-ph/0101098 . doi:10.1103/RevModPhys.74.145.
  18. ↑ Fuchs, Christopher A.; van de Graaf, Jeroen (1999). "Cryptographic distinguishability measures for quantum-mechanical states". IEEE Transactions on Information Theory. 45 (4): 1216–1227. doi:10.1109/18.761271.
  19. ↑ Watrous, John. "The Theory of Quantum Information (book manuscript)" (PDF). University of Waterloo.
  20. ↑ Barnum, Howard; Caves, Carlton M.; Fuchs, Christopher A.; Jozsa, Richard; Schumacher, Benjamin (1996-04-08). "Noncommuting Mixed States Cannot Be Broadcast". Physical Review Letters. 76 (15): 2818–2821. arXiv: quant-ph/9511010 . Bibcode:1996PhRvL..76.2818B. doi:10.1103/physrevlett.76.2818.
  21. ↑ Lemm, Marius; Wilde, Mark M. (2017-07-05). "Information-theoretic limitations on approximate quantum cloning and broadcasting". Physical Review A. 96 (1). doi:10.1103/PhysRevA.96.012304.
  22. ↑ Brandão, Fernando G. S. L.; Harrow, Aram W. (June 2013). "Quantum de Finetti theorems under local measurements with applications". STOC '13: Proceedings of the forty-fifth annual ACM symposium on Theory of Computing. ACM: 861–870. arXiv: 1210.6367 . doi:10.1145/2488608.2488718. ISBN   978-1-4503-2029-0.
  23. ↑ Bennett, Charles H.; DiVincenzo, David P.; Fuchs, Christopher A.; Mor, Tal; Rains, Eric; Shor, Peter W.; Smolin, John A.; Wootters, William K. (1999-02-01). "Quantum nonlocality without entanglement". Physical Review A. 59 (2): 1070–1091. arXiv: quant-ph/9804053 . doi:10.1103/PhysRevA.59.1070.
  24. ↑ Bengtsson, Ingemar; Życzkowski, Karol (2017). Geometry of Quantum States: An Introduction to Quantum Entanglement (2nd ed.). Cambridge, UK: Cambridge University Press. pp. 458–460. ISBN   978-1-107-02625-4.
  25. ↑ Bennett, C. H.; Fuchs, C. A.; Smolin, J. A. (1997). "Entanglement-Enhanced Classical Communication on a Noisy Quantum Channel". In Hirota, O.; Holevo, A. S.; Caves, C. M. (eds.). Quantum Communication, Computing and Measurement. Plenum Press. pp. 79–88. arXiv: quant-ph/9611006 .
  26. ↑ Matsumoto, Keiji; Shimono, Toshiyuki; Winter, Andreas (2004). "Remarks on additivity of the Holevo channel capacity and of the entanglement of formation". Communications in Mathematical Physics. 246 (3): 427–442. doi:10.1007/s00220-003-0919-0.
  27. ↑ Hastings, M. B. (2009). "A Counterexample to Additivity of Minimum Output Entropy". Nature Physics. 5: 255. arXiv: 0809.3972 . doi: 10.1038/nphys1224 .
  28. ↑ Fuchs, Christopher A. (2011). Coming of Age with Quantum Information: Notes on a Paulian Idea. Cambridge: Cambridge University Press. ISBN   978-0-521-19926-1.
  29. ↑ Trabesinger, Andreas (June 2011). "Inside quantum information". Nature Physics. 7: 443–444. doi:10.1038/nphys2020.
  30. ↑ Greenberger, Daniel M. (October 2011). "Book Reviews". American Journal of Physics. 79 (10): 1083–1084. doi:10.1119/1.3602093.
  31. ↑ Cavalcanti, Eric (2011). "Quantum Subversives". American Scientist. 99 (6): 500–502. doi:10.1511/2011.93.500.
  32. ↑ Mermin, N. David (March 2014). "Physics: QBism puts the scientist back into science". Nature. 507 (7493): 421–423. doi:10.1038/507421a.
  33. ↑ Fuchs, Christopher A. (2023). "QBism, Where Next?". In Berghofer, Philipp; Wiltsche, Harald A. (eds.). Phenomenology and QBism: New Approaches to Quantum Mechanics. Routledge. arXiv: 2303.01446 . doi:10.4324/9781003259008-4. ISBN   9781003259008.
  34. ↑ Berghofer, Philipp (2024). "Quantum Reconstructions as Stepping Stones Toward ψ-Doxastic Interpretations?". Foundations of Physics. 54 (46) 46. arXiv: 2410.22132 . Bibcode:2024FoPh...54...46B. doi:10.1007/s10701-024-00778-2. PMC   11222275 . PMID   38974192.
  35. ↑ Fuchs, Christopher A.; Mermin, N. David; Schack, Rüdiger (2014). "An introduction to QBism with an application to the locality of quantum mechanics". American Journal of Physics. 82 (8): 749–754. arXiv: 1311.5253 . Bibcode:2014AmJPh..82..749F. doi:10.1119/1.4874855.
  36. ↑ Fuchs, Christopher A.; Stacey, Blake C. (2019). Rasel, E. M.; Schleich, W. P.; Wölk, S. (eds.). "QBism: Quantum Theory as a Hero's Handbook". Foundations of Quantum Theory, Proceedings of the International School of Physics "Enrico Fermi". 197 (Foundations of Quantum Theory). IOS Press: 133–202. arXiv: 1612.07308 . doi:10.3254/978-1-61499-937-9-133.
  37. ↑ Crease, Robert P. (2022-08-24). "When physicists and philosophers realize they share a noble truth". Physics World. Retrieved 2025-12-13.
  38. ↑ Stacey, Blake C. (2016). "Von Neumann Was Not a Quantum Bayesian". Philosophical Transactions of the Royal Society A. 374 (2068): 20150235. arXiv: 1412.2409 . Bibcode:2016RSPTA.37450235S. doi:10.1098/rsta.2015.0235.{{cite journal}}: CS1 maint: article number as page number (link)
  39. ↑ Fuchs, Christopher A. (2023). "Letters for Andrei: QBism and the Unfinished Nature of Nature". In Plotnitsky, Arkady; Haven, Emmanuel (eds.). The Quantum-Like Revolution: A Festschrift for Andrei Khrennikov. Springer. pp. 61–90. arXiv: 2109.08153 . doi:10.1007/978-3-031-12986-5_3. ISBN   978-3-031-12986-5.
  40. ↑ Fuchs, Christopher A.; Olshanii, Maxim; Weiss, Matthew B. (2021-12-01). "Quantum mechanics? It's all fun and games until someone loses an i". Asian Journal of Physics. 30 (12): 1701–1726. arXiv: 2206.15343 .
  41. ↑ DeBrota, John B.; Fuchs, Christopher A.; Schack, Rüdiger (2020). "Respecting One's Fellow: QBism's Analysis of Wigner's Friend". Foundations of Physics. 50 (12): 1859–1874. arXiv: 2008.03572 . Bibcode:2020FoPh...50.1859D. doi:10.1007/s10701-020-00369-x.
  42. ↑ DeBrota, John B.; Fuchs, Christopher A.; Pienaar, Jacques L.; Stacey, Blake C. (2021). "Born's rule as a quantum extension of Bayesian coherence". Physical Review A. 104 (2): 022207. arXiv: 2012.14397 . Bibcode:2021PhRvA.104b2207D. doi:10.1103/PhysRevA.104.022207.{{cite journal}}: CS1 maint: article number as page number (link)
  43. ↑ DeBrota, John B.; Fuchs, Christopher A.; Stacey, Blake C. (2020). "Symmetric informationally complete measurements identify the irreducible difference between classical and quantum systems". Physical Review Research. 2 (1): 013074. arXiv: 1805.08721 . Bibcode:2020PhRvR...2a3074D. doi:10.1103/PhysRevResearch.2.013074.{{cite journal}}: CS1 maint: article number as page number (link)
  44. ↑ Zauner, Gerhard (1999). Quantendesigns. Grundzüge einer nichtkommutativen Designtheorie [Quantum designs: foundations of a noncommutative design theory](PDF) (PhD thesis) (in German). University of Vienna.
  45. ↑ Healey, Richard (February 22, 2022). "Quantum-Bayesian and Pragmatist Views of Quantum Theory". In Zalta, Edward N. (ed.). Stanford Encyclopedia of Philosophy .
  46. ↑ Słomczyński, Wojciech; Szymusiak, Anna (2020-09-30). "Morphophoric POVMs, generalised qplexes, and 2-designs". Quantum. 4: 338. doi:10.22331/q-2020-09-30-338.
  47. ↑ Weiss, Matthew B. (May 8, 2025). "Characterizing quantum state-space with a single quantum measurement". Physical Review A. 111 052205. arXiv: 2412.13505 . doi:10.1103/PhysRevA.111.052205.
  48. ↑ "International Quantum Communication Award". International Conference on Quantum Communication, Measurement and Computing. Retrieved December 13, 2025.
  49. ↑ "About Us: Honours and Awards". Perimeter Institute. Retrieved December 13, 2025.
  50. ↑ "Preface: Quantum Communication, Measurement and Computing (QCMC)". AIP Conference Proceedings. 1363: 1. 2011. doi:10.1063/1.3630136.
  51. ↑ Furusawa, A.; Sørensen, J. L.; Braunstein, S. L.; Fuchs, C. A.; Kimble, H. J.; Polzik, E. S. (1998-10-23). "Unconditional Quantum Teleportation". Science. 282 (5389): 706–709. doi:10.1126/science.282.5389.706.
  52. ↑ "The Runners-Up: The News and Editorial Staffs". Science. 282 (5397): 2157–2161. 1998-12-18. doi:10.1126/science.282.5397.2157.
  53. ↑ "Chancellor's Distinguished Scholarship Award Recipients" (PDF). University of Massachusetts Boston. Retrieved December 12, 2025.
  54. ↑ Crumey, Andrew (August 3, 2018). "'Through Two Doors at Once' Review: Interfering with Reality". Wall Street Journal. Retrieved December 12, 2025.
  55. ↑ Crumey, Andrew (September 13, 2019). "'Do Dice Play God?' Review: The Ins and Outs of Odds". Wall Street Journal. Retrieved December 12, 2025.
  56. ↑ Frank, Adam (March 13, 2017). "Minding Matter". Aeon. Retrieved December 12, 2025.
  57. ↑ Frank, Adam (March 26, 2017). "Mind, Matter and Materialism". NPR.
  58. ↑ von Baeyer, Hans Christian (June 2013). "Quantum Weirdness? It's All in Your Mind". Scientific American. 308 (6): 46–51. Bibcode:2013SciAm.308f..46V. doi:10.1038/scientificamerican0613-46. PMID   23729070.
  59. ↑ Powell, Corey S. (29 November 2019). "Quantum Physics Is No More Mysterious Than Crossing the Street: A Conversation with Chris Fuchs". Discover Magazine.
  60. ↑ Henderson, Bob (23 February 2022). "My Quantum Leap: The theory of physics that showed me a new reality". Nautilus.
  61. ↑ Gefter, Amanda (December 4, 2025). "Reality Exists Without Observers? Boooo!". Nautilus. Retrieved December 12, 2025.
  62. ↑ von Rauchhaupt, Ulf (9 February 2014). "So liegt denn alles im Auge des Betrachters". Frankfurter Allgemeine Sonntagszeitung (in German). No. 6. p. 62.
  63. ↑ Examples:
    • Bachmann, Klaus (December 2021). "Jede Messung kreiert etwas Neues im Universum". GEOkompakt (in German) (69): 80–83.
    • Kvellestad, Anders (29 September 2017). "Tumbling Down a Quantum Rabbit Hole". Mentsch Magazine.
    • Gelonesi, Joe (25 September 2015). "Why the Multiverse Is All about You". ABC Radio National – The Philosopher’s Zone.
    • Poirier, Hervé (2012). "L'information relance la quantique". Science et Vie, Hors Série (in French). No. 260. pp. 100–102.
  64. ↑ QBism Through the Wormhole. Hosted and narrated by Morgan Freeman. 2014 – via YouTube.{{cite AV media}}: CS1 maint: others in cite AV media (notes) (link)
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