Quantum Inf Process (2012) 11:633–636DOI 10.1007/s11128-011-0343-x

BOOK REVIEW

Christopher A. Fuchs: Coming of age with quantuminformation: notes on a Paulian ideaCambridge University Press

Eric Cavalcanti

© All rights reserved 2011

In post-Stalin Soviet Union, dissidents used underground networks to distribute cen-sored material. This activity, which was called samizdat (translates to “self-published”)put its practitioners at grave risk. Though certainly not nearly as risky, it requiressubstantial courage for scientists to “come out” and make public their philosophi-cal thoughts. It likewise requires a large dose of chutzpah for one to publish one’sown emails as a book. In “Coming of Age with Quantum Information” ChristopherFuchs—who is a Senior Researcher at the Perimeter Institute for Theoretical Physics,in Waterloo, Canada—does both of these things. The book grew out of his correspon-dence with friends and colleagues between 1995 and 2001. and which he started todistribute—also electronically—as his “samizdat”.

Among the “subversives” that were—knowingly or not—dragged into Chris’ sam-izdat bv corresponding with him are many leading quantum information scientists:Charles Bennett, Gilles Brassard, Carlton Caves, Rolf Landauer, David Mermin, AsherPeres, John Preskill, Abner Shimony, Bill Wootters, Anton Zeilinger, among others.The conversations are often about technical aspects of quantum information. But aboveall, these very interesting and often very personal letters, full of scholarship, excite-ment, enthusiasm and perplexity, are about a passionate young scientist’s attempts tocome to grips with “the message quantum theory is trying to tell us”.

In contrast with the Soviet dissidents, Fuchs takes a philosophical position that is,among the plethora of interpretations of quantum theory, well aligned with mainstreamthought—that is to say, well aligned with the operationalist philosophy defended byNiels Bohr, Werner Heisenberg and Wolfgang Pauli, the view referred to as the “Copen-hagen interpretation.” Indeed, Fuchs says that he is “concerned by the growing aban-donment of standard (Copenhagen) quantum mechanics that I see all around me”.

E. Cavalcanti (B)Griffith University, Brisbane, QLD, Australiae-mail: eric.cavalcanti@gmail.com

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What makes Fuchs’ contribution unique however, is that he is one of the very few whotake the details of that philosophy very seriously, and follow them to what seems to betheir ultimate consequences. And those consequences, when clearly spelled out, cansound subversive indeed.

We learn in the introduction of the book that Chris was a nonconformist from anearly age. After finding that the physics he learned in junior high school wouldn’tallow him to fulfill his television-fuelled dream of flying to the stars, he decided that“Physics must be wrong!” and that he “had to become a physicist, not for the loveof physics, but for the distrust of it.” He chose to attend the University of Texasat Austin, where his rebellious spirit found much to resonate with in John Wheelerand his program of “law without law”. Wheeler’s influence is patent throughout thebook, and provides some of the most amusing and thought-provoking passages: “Youknow that John Wheeler had this idea that things become more real as they becomeacknowledged by more and more members of the “community of communicators.”I would hate one of the things we said to become real if later we decided we didn’tlike it!”

As in the one above, many passages in the book may on the surface appear toveer dangerously close to the type of bad mysticism one may find in some popularmisrepresentations of quantum theory, but that’s far from being the case. It is goodmysticism—akin to that of Schrödinger or Bohr, not that of What the bleep do weknow!? It is well-informed, and often deep. And unapologetic: in one passage DavidMermin comments that he is “getting close to Schrödingerian mysticism” and that“the difference (…) is that you say the observer is in the world while Schrödingersays that the world is in the observer. Both of you say (with Pauli) that they cannotbe separated”. Fuchs’ reaction dispels any doubt: “God I love that! Can I put it in theSamizdat??!?”. He seems to have no qualms with sounding mystic; he talks to Merminof his “religious love of the quantum and its mysteries”, and to his friend Greg Comerthat “I think I take religious comfort in it (…) I am a priest, a student of the holyscriptures.” But when Fuchs forwards to Paul Benioff one of his later letters to Comer,he is careful to say: “Don’t take the religious imagery as a serious reflection of myviews; I used it only to help drive a point home.”

It was in Pauli that Fuchs found substance to his thoughts: “With Pauli’s way ofputting things, I felt I had finally latched on to the correct flavor of idea for takingWheeler’s program forward.” The series of emails that are collected in this book are, inFuchs’ words, “my best effort to date at defining a vague thought that keeps creepinginto my mind—the Paulian idea.” That idea is perhaps best represented in a quotefrom Pauli that Fuchs shares with Comer: “In the new pattern of thought we do notassume any longer the detached observer… but an observer who by his indeterminableeffects creates a new situation, theoretically described as a new state of the observedsystem.” Or as Fuchs himself puts it in a later letter to Comer: “The world in some veryreal sense is a construct and creation of thinking beings simply because its propertiesare so severely tied to the particular questions we ask of it. But on the other hand,the world is not completely unreal as a result of this; we generally cannot control theoutcomes of our measurements.”

This book is above all very personal (what else could a collection of emails be?). Init the reader will find plenty of anecdotes about Chris’ friends, his wife and daughter,

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his dogs, his bad poems and his dreams, including the one where he finds a bottleof “Kant Cola” in a dark, smoky Bohemian-feeling joint in Austin, takes a sip and“for a miraculous moment”, he says, “I understood all the intricacies of the world—I understood the necessity of quantum mechanics.” The personal stories give lifeto the book, like when we find about his family’s tragic loss of their home inNew Mexico and almost all of their belongings to a bush fire originating in the nearbyCerro Grande in May 2000, an event which gave him the tongue-in-cheek excuse topublish this collection of emails as a “backup” on arxiv.org.

One should not approach this book expecting a coherent treatise—it is the fur-thest from that. But the reader who understands its personal character will find init a delightfully poetic vision. Fuchs’ message is one of hope—that we will soonfinally get to “the bottom of things”, and that when we do, we will find that “theworld is so much more than a mechanical contraption clinking along” and that “thereis room for something new under the sun.” When he writes to friends and familyabout losing his belongings in the fire, he says, “Now that so many of my recordsare gone, I hope there is a grain of truth in John Wheeler’s words. For then, the pastwould be every bit as open as the future.” He finds it “hard to gulp that my wholelife is an illusion”. He hopes that the world has a place for human free will, andfinds that “quantum mechanics helps me believe we’re closer to that situation thanI once thought possible.”

Fuchs can be tendentious at times. In one passage, for instance, Fuchs dismisses themany-worlds interpretation of quantum theory because “[the many-worlders] likelywould have been predisposed to many-worlds even if they had known no quantummechanics.” Writing to Peres about some of the criticism of their 1999 Physics Todayarticle, he claims that “I am not pushed to the rejection of a free-standing reality inthe quantum world out of a predilection for positivism. I am pushed there becausethat is the overwhelming message quantum THEORY is trying to tell me.” Elsewhere,however, he gives signs that he would probably also have been predisposed to hissubjectivist view even if he had known no quantum mechanics: “If [quantum] inde-terminism had not been of such a variety as to allow us more free reign over ourdestiny or destruction, I think I would be quite disappointed in it.” And indeed, justlike with many worlds, one can of course believe in Bayesianism regardless of quan-tum mechanics. Indeed, subjective probabilities actually makemore sense in a classicalworld—in a deterministic universe any probabilities must be a measure of someone’signorance about the factual situation; in a quantum world, where probabilities seemto be determined by physical law, it is harder to defend this interpretation.

But taken with a grain of salt, this book is indeed a gem. It is certainly recom-mended reading for anyone in the field of quantum information: as Mermin puts it inthe foreword, “Chris Fuchs is the conscience of the field.” It is not aimed at a generalreadership, as it is often very technical, but none of the technicalities are importantfor the understanding, or entertainment, that the book provides, and its nonlinear stylemeans that skipping the most opaque parts hardly implies any break in continuity. Thereader interested in quantum foundations will surely find this book an inexhaustiblesource of amusing quotes and food for thought, even when—or especially when!—they may disagree with its views. And for anyone who might have been under theimpression that all questions about the foundations of quantum theory have been set-

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tled long ago ought to take this unique opportunity to peek into the personal commu-nications of some of the leaders in the field and find evidence that those foundationaldebates are very much alive.

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