In a recent result, Frauchiger and Renner argue that if quantum theory accurately describes complex systems like observers who perform measurements, then "we are forced to give up the view that there is one single reality." Following a review of the Frauchiger-Renner argument, I argue that quantum mechanics should be understood probabilistically, as a new sort of non-Boolean probability theory, rather than representationally, as a theory about the elementary constituents of the physical world and how these elements evolve dynamically over time. I show that this way of understanding quantum mechanics is not in conflict with a consistent "single-world" interpretation of the theory.

1 aBub, Jeffrey uhttps://arxiv.org/abs/1804.0326700500nam a2200109 4500008004100000245009500041210006900136260003100205100001700236700001500253856012200268 2018 eng d00aTotally random: why nobody understands quantum mechanics (a serious comic on entanglement)0 aTotally random why nobody understands quantum mechanics a seriou bPrinceton University Press1 aBub, Jeffrey1 aBub, Tanya uhttps://quics.umd.edu/publications/totally-random-why-nobody-understands-quantum-mechanics-serious-comic-entanglement00534nas a2200109 4500008004100000245003200041210003000073260001500103520025200118100001700370856003700387 2017 eng d00aWhy Bohr was (Mostly) Right0 aWhy Bohr was Mostly Right c2017/11/053 aAfter a discussion of the Frauchiger-Renner argument that no “singleworld” interpretation of quantum mechanics can be self-consistent, I propose a “Bohrian” alternative to many-worlds or QBism as the rational option.

1 aBub, Jeffrey uhttps://arxiv.org/abs/1711.0160401739nam a2200109 4500008004100000245004800041210004700089260004000136520139900176100001701575856003701592 2016 eng d00aBananaworld: Quantum Mechanics for Primates0 aBananaworld Quantum Mechanics for Primates bOxford University Pressc2012/11/133 aThis is intended to be a serious paper, in spite of the title. The idea is that quantum mechanics is about probabilistic correlations, i.e., about the structure of information, since a theory of information is essentially a theory of probabilistic correlations. To make this clear, it suffices to consider measurements of two binary-valued observables, x with outcomes a = 0 or 1, performed by Alice in a region A, and y with outcomes b = 0 or 1 performed by Bob in a separated region B --or, to emphasize the banality of the phenomena, two ways of peeling a banana, resulting in one of two tastes. The imagined bananas of Bananaworld are non-standard, with operational or phenomenal probabilistic correlations for peelings and tastes that lie outside the polytope of local correlations. The 'no go' theorems tell us that we can't shoe-horn these correlations into a classical correlation polytope, which has the structure of a simplex, by supposing that something has been left out of the story, without giving up fundamental principles that define what we mean by a physical system. The nonclassical features of quantum mechanics, including the irreducible information loss on measurement, are shown to be generic features of correlations that lie outside the local correlation polytope. As far as the conceptual problems are concerned, we might as well talk about bananas.

1 aBub, Jeffrey uhttp://arxiv.org/abs/1211.3062v200412nas a2200121 4500008004100000245004700041210004500088260001500133100001700148700002100165700002400186856008000210 2016 eng d00aWhose Information? Information About What?0 aWhose Information Information About What c2016/01/011 aBub, Jeffrey1 aZeilinger, Anton1 aBertlmann, Reinhold uhttps://quics.umd.edu/publications/whose-information-information-about-what01441nas a2200133 4500008004100000245011300041210006900154260001500223300001400238490000700252520098600259100001701245856004501262 2015 eng d00aThe Measurement Problem from the Perspective of an Information Theoretic Interpretation of Quantum Mechanics0 aMeasurement Problem from the Perspective of an Information Theor c10/28/2015 a7374-73860 v173 aThe aim of this paper is to consider the consequences of an information-theoretic interpretation of quantum mechanics for the measurement problem. The motivating idea of the interpretation is that the relation between quantum mechanics and the structure of information is analogous to the relation between special relativity and the structure of space-time. Insofar as quantum mechanics deals with a class of probabilistic correlations that includes correlations structurally different from classical correlations, the theory is about the structure of information: the possibilities for representing, manipulating, and communicating information in a genuinely indeterministic quantum world in which measurement outcomes are intrinsically random are different than we thought. Part of the measurement problem is deflated as a pseudo-problem on this view, and the theory has the resources to deal with the remaining part, given certain idealizations in the treatment of macrosystems.1 aBub, Jeffrey uhttp://www.mdpi.com/1099-4300/17/11/737400905nas a2200121 4500008004100000245004100041210004100082260001500123520053800138100001700676700002200693856006800715 2015 eng d00aQuantum Entanglement and Information0 aQuantum Entanglement and Information c02/07/20153 aQuantum entanglement is a physical resource, like energy, associated with the peculiar nonclassical correlations that are possible between separated quantum systems. Entanglement can be measured, transformed, and purified. A pair of quantum systems in an entangled state can be used as a quantum information channel to perform computational and cryptographic tasks that are impossible for classical systems. The general study of the information-processing capabilities of quantum systems is the subject of quantum information theory.1 aBub, Jeffrey1 aZalta, Edward, N. uhttp://plato.stanford.edu/archives/sum2015/entries/qt-entangle/00594nas a2200145 4500008004100000245009000041210006900131260001500200100001700215700002900232700002300261700002000284700002600304856011800330 2014 eng d00a"Einstein and Bohr Meet Alice and Bob', Logic and Science Facing the New Technologies0 aEinstein and Bohr Meet Alice and Bob Logic and Science Facing th c2014/01/011 aBub, Jeffrey1 aSchroeder-Heister, Peter1 aHeinzmann, Gerhard1 aHodges, Wilfrid1 aBour, Pierre, Edouard uhttps://quics.umd.edu/publications/einstein-and-bohr-meet-alice-and-bob-logic-and-science-facing-new-technologies02166nas a2200133 4500008004100000245005300041210005300094260001400147300001600161490000700177520179400184100001701978856003701995 2014 eng d00aQuantum Correlations and the Measurement Problem0 aQuantum Correlations and the Measurement Problem c2013/6/30 a3346 - 33690 v533 a The transition from classical to quantum mechanics rests on the recognition that the structure of information is not what we thought it was: there are operational, i.e., phenomenal, probabilistic correlations that lie outside the polytope of local correlations. Such correlations cannot be simulated with classical resources, which generate classical correlations represented by the points in a simplex, where the vertices of the simplex represent joint deterministic states that are the common causes of the correlations. The `no go' hidden variable theorems tell us that we can't shoe-horn correlations outside the local polytope into a classical simplex by supposing that something has been left out of the story. The replacement of the classical simplex by the quantum convex set as the structure representing probabilistic correlations is the analogue for quantum mechanics of the replacement of Newton's Euclidean space and time by Minkowski spacetime in special relativity. The nonclassical features of quantum mechanics, including the irreducible information loss on measurement, are generic features of correlations that lie outside the local correlation polytope. This paper is an elaboration of these ideas, and its consequences for the measurement problem of quantum mechanics. A large part of the difficulty is removed by seeing that the inconsistency in reconciling the entangled state at the end of a quantum measurement process with the definiteness of the macroscopic pointer reading and the definiteness of the correlated value of the measured micro-observable is only apparent and depends on a stipulation that is not required by the structure of the quantum possibility space. Replacing this stipulation by an alternative consistent stipulation resolves the problem. 1 aBub, Jeffrey uhttp://arxiv.org/abs/1210.6371v302190nas a2200133 4500008004100000245008300041210006900124260001400193490000700207520177000214100001701984700001802001856003702019 2014 eng d00aQuantum Interactions with Closed Timelike Curves and Superluminal Signaling 0 aQuantum Interactions with Closed Timelike Curves and Superlumina c2014/2/120 v893 a There is now a significant body of results on quantum interactions with closed timelike curves (CTCs) in the quantum information literature, for both the Deutsch model of CTC interactions (D-CTCs) and the projective model (P-CTCs). As a consequence, there is a prima facie argument exploiting entanglement that CTC interactions would enable superluminal and, indeed, effectively instantaneous signaling. In cases of spacelike separation between the sender of a signal and the receiver, whether a receiver measures the local part of an entangled state or a disentangled state to access the signal can depend on the reference frame. We propose a consistency condition that gives priority to either an entangled perspective or a disentangled perspective in spacelike separated scenarios. For D-CTC interactions, the consistency condition gives priority to frames of reference in which the state is disentangled, while for P-CTC interactions the condition selects the entangled state. Using the consistency condition, we show that there is a procedure that allows Alice to signal to Bob in the past via relayed superluminal communications between spacelike separated Alice and Clio, and spacelike separated Clio and Bob. This opens the door to time travel paradoxes in the classical domain. Ralph (arXiv:1107.4675) first pointed this out for P-CTCs, but we show that Ralph's procedure for a 'radio to the past' is flawed. Since both D-CTCs and P-CTCs allow classical information to be sent around a spacetime loop, it follows from a result by Aaronson and Watrous (Proc.Roy.Soc.A, 465:631-647 (2009)) for CTC-enhanced classical computation that a quantum computer with access to P-CTCs would have the power of PSPACE, equivalent to a D-CTC-enhanced quantum computer. 1 aBub, Jeffrey1 aStairs, Allen uhttp://arxiv.org/abs/1309.4751v400722nas a2200121 4500008004100000245002900041210002800070260001500098300001200113520042100125100001700546856003700563 2012 eng d00aWhy the Tsirelson bound?0 aWhy the Tsirelson bound c2012/08/18 a167-1853 a Wheeler's question 'why the quantum' has two aspects: why is the world quantum and not classical, and why is it quantum rather than superquantum, i.e., why the Tsirelson bound for quantum correlations? I discuss a remarkable answer to this question proposed by Pawlowski et al (2009), who provide an information-theoretic derivation of the Tsirelson bound from a principle they call 'information causality.' 1 aBub, Jeffrey uhttp://arxiv.org/abs/1208.3744v101025nas a2200121 4500008004100000245007200041210006900113260001500182520063400197100001700831700001800848856003700866 2010 eng d00aContextuality in Quantum Mechanics: Testing the Klyachko Inequality0 aContextuality in Quantum Mechanics Testing the Klyachko Inequali c2010/06/023 a The Klyachko inequality is an inequality for the probabiities of the values of five observables of a spin-1 particle, which is satisfied by any noncontextual assignment of values to this set of observables, but is violated by the probabilities defined by a certain quantum state. We describe an experiment between two entangled spin-1 particles to test contextuality via a related inequality. We point out that a test of contextuality by measurements on a single particle to confirm the Klyachko inequality requires an assumption of non-disturbance by the measuring instrument, which is avoided in the two-particle experiment. 1 aBub, Jeffrey1 aStairs, Allen uhttp://arxiv.org/abs/1006.0500v201335nas a2200133 4500008004100000245005200041210005100093260001500144300001200159490000700171520096900178100001701147856003701164 2010 eng d00aQuantum computation and pseudo-telepathic games0 aQuantum computation and pseudotelepathic games c2010/05/14 a458-4720 v753 a A quantum algorithm succeeds not because the superposition principle allows 'the computation of all values of a function at once' via 'quantum parallelism,' but rather because the structure of a quantum state space allows new sorts of correlations associated with entanglement, with new possibilities for information-processing transformations between correlations, that are not possible in a classical state space. I illustrate this with an elementary example of a problem for which a quantum algorithm is more efficient than any classical algorithm. I also introduce the notion of 'pseudo-telepathic' games and show how the difference between classical and quantum correlations plays a similar role here for games that can be won by quantum players exploiting entanglement, but not by classical players whose only allowed common resource consists of shared strings of random numbers (common causes of the players' correlated responses in a game). 1 aBub, Jeffrey uhttp://arxiv.org/abs/1005.2449v101818nas a2200109 4500008004100000245006700041210006500108260001500173520146600188100001701654856003701671 2010 eng d00aQuantum probabilities: an information-theoretic interpretation0 aQuantum probabilities an informationtheoretic interpretation c2010/05/143 a This Chapter develops a realist information-theoretic interpretation of the nonclassical features of quantum probabilities. On this view, what is fundamental in the transition from classical to quantum physics is the recognition that \emph{information in the physical sense has new structural features}, just as the transition from classical to relativistic physics rests on the recognition that space-time is structurally different than we thought. Hilbert space, the event space of quantum systems, is interpreted as a kinematic (i.e., pre-dynamic) framework for an indeterministic physics, in the sense that the geometric structure of Hilbert space imposes objective probabilistic or information-theoretic constraints on correlations between events, just as the geometric structure of Minkowski space in special relativity imposes spatio-temporal kinematic constraints on events. The interpretation of quantum probabilities is more subjectivist in spirit than other discussions in this book (e.g., the chapter by Timpson), insofar as the quantum state is interpreted as a credence function---a bookkeeping device for keeping track of probabilities---but it is also objective (or intersubjective), insofar as the credences specified by the quantum state are understood as uniquely determined, via Gleason's theorem, by objective correlational constraints on events in the nonclassical quantum event space defined by the subspace structure of Hilbert space. 1 aBub, Jeffrey uhttp://arxiv.org/abs/1005.2448v101422nas a2200133 4500008004100000245006200041210005700103260001400160300001600174490000700190520103700197100001701234856003701251 2010 eng d00aVon Neumann's 'No Hidden Variables' Proof: A Re-Appraisal0 aVon Neumanns No Hidden Variables Proof A ReAppraisal c2010/6/11 a1333 - 13400 v403 a Since the analysis by John Bell in 1965, the consensus in the literature is that von Neumann's 'no hidden variables' proof fails to exclude any significant class of hidden variables. Bell raised the question whether it could be shown that any hidden variable theory would have to be nonlocal, and in this sense 'like Bohm's theory.' His seminal result provides a positive answer to the question. I argue that Bell's analysis misconstrues von Neumann's argument. What von Neumann proved was the impossibility of recovering the quantum probabilities from a hidden variable theory of dispersion free (deterministic) states in which the quantum observables are represented as the 'beables' of the theory, to use Bell's term. That is, the quantum probabilities could not reflect the distribution of pre-measurement values of beables, but would have to be derived in some other way, e.g., as in Bohm's theory, where the probabilities are an artefact of a dynamical process that is not in fact a measurement of any beable of the system. 1 aBub, Jeffrey uhttp://arxiv.org/abs/1006.0499v101445nas a2200145 4500008004100000245006100041210005900102260001400161300001400175490000700189520103100196100001701227700001801244856003701262 2009 eng d00aContextuality and nonlocality in 'no signaling' theories0 aContextuality and nonlocality in no signaling theories c2009/4/21 a690 - 7110 v393 a We define a family of 'no signaling' bipartite boxes with arbitrary inputs and binary outputs, and with a range of marginal probabilities. The defining correlations are motivated by the Klyachko version of the Kochen-Specker theorem, so we call these boxes Kochen-Specker-Klyachko boxes or, briefly, KS-boxes. The marginals cover a variety of cases, from those that can be simulated classically to the superquantum correlations that saturate the Clauser-Horne-Shimony-Holt inequality, when the KS-box is a generalized PR-box (hence a vertex of the `no signaling' polytope). We show that for certain marginal probabilities a KS-box is classical with respect to nonlocality as measured by the Clauser-Horne-Shimony-Holt correlation, i.e., no better than shared randomness as a resource in simulating a PR-box, even though such KS-boxes cannot be perfectly simulated by classical or quantum resources for all inputs. We comment on the significance of these results for contextuality and nonlocality in 'no signaling' theories. 1 aBub, Jeffrey1 aStairs, Allen uhttp://arxiv.org/abs/0903.1462v202123nas a2200121 4500008004100000245003900041210003900080260001500119520179200134100001701926700002101943856003701964 2007 eng d00aTwo dogmas about quantum mechanics0 aTwo dogmas about quantum mechanics c2007/12/273 a We argue that the intractable part of the measurement problem -- the 'big' measurement problem -- is a pseudo-problem that depends for its legitimacy on the acceptance of two dogmas. The first dogma is John Bell's assertion that measurement should never be introduced as a primitive process in a fundamental mechanical theory like classical or quantum mechanics, but should always be open to a complete analysis, in principle, of how the individual outcomes come about dynamically. The second dogma is the view that the quantum state has an ontological significance analogous to the significance of the classical state as the 'truthmaker' for propositions about the occurrence and non-occurrence of events, i.e., that the quantum state is a representation of physical reality. We show how both dogmas can be rejected in a realist information-theoretic interpretation of quantum mechanics as an alternative to the Everett interpretation. The Everettian, too, regards the 'big' measurement problem as a pseudo-problem, because the Everettian rejects the assumption that measurements have definite outcomes, in the sense that one particular outcome, as opposed to other possible outcomes, actually occurs in a quantum measurement process. By contrast with the Everettians, we accept that measurements have definite outcomes. By contrast with the Bohmians and the GRW 'collapse' theorists who add structure to the theory and propose dynamical solutions to the 'big' measurement problem, we take the problem to arise from the failure to see the significance of Hilbert space as a new kinematic framework for the physics of an indeterministic universe, in the sense that Hilbert space imposes kinematic (i.e., pre-dynamic) objective probabilistic constraints on correlations between events. 1 aBub, Jeffrey1 aPitowsky, Itamar uhttp://arxiv.org/abs/0712.4258v201544nas a2200109 4500008004100000245005900041210005900100260001500159520119900174100001701373856004401390 2006 eng d00aQuantum computation from a quantum logical perspective0 aQuantum computation from a quantum logical perspective c2006/05/293 a It is well-known that Shor's factorization algorithm, Simon's period-finding algorithm, and Deutsch's original XOR algorithm can all be formulated as solutions to a hidden subgroup problem. Here the salient features of the information-processing in the three algorithms are presented from a different perspective, in terms of the way in which the algorithms exploit the non-Boolean quantum logic represented by the projective geometry of Hilbert space. From this quantum logical perspective, the XOR algorithm appears directly as a special case of Simon's algorithm, and all three algorithms can be seen as exploiting the non-Boolean logic represented by the subspace structure of Hilbert space in a similar way. Essentially, a global property of a function (such as a period, or a disjunctive property) is encoded as a subspace in Hilbert space representing a quantum proposition, which can then be efficiently distinguished from alternative propositions, corresponding to alternative global properties, by a measurement (or sequence of measurements) that identifies the target proposition as the proposition represented by the subspace containing the final state produced by the algorithm. 1 aBub, Jeffrey uhttp://arxiv.org/abs/quant-ph/0605243v200408nas a2200121 4500008004100000245005700041210005600098260001500154520003800169100001800207700001700225856004400242 2005 eng d00aConditionalizing and commutativity: a note on Malley0 aConditionalizing and commutativity a note on Malley c2005/06/193 a This paper has been withdrawn. 1 aStairs, Allen1 aBub, Jeffrey uhttp://arxiv.org/abs/quant-ph/0506159v200763nas a2200109 4500008004100000245004000041210004000081260001500121520045600136100001700592856004400609 2005 eng d00aQuantum information and computation0 aQuantum information and computation c2005/12/153 a This article deals with theoretical developments in the subject of quantum information and quantum computation, and includes an overview of classical information and some relevant quantum mechanics. The discussion covers topics in quantum communication, quantum cryptography, and quantum computation, and concludes by considering whether a perspective in terms of quantum information sheds new light on the conceptual problems of quantum mechanics. 1 aBub, Jeffrey uhttp://arxiv.org/abs/quant-ph/0512125v200876nas a2200133 4500008004100000245005100041210005100092260001500143300001400158490000700172520050200179100001700681856004400698 2005 eng d00aQuantum mechanics is about quantum information0 aQuantum mechanics is about quantum information c2005/04/01 a541 - 5600 v353 a I argue that quantum mechanics is fundamentally a theory about the representation and manipulation of information, not a theory about the mechanics of nonclassical waves or particles. The notion of quantum information is to be understood as a new physical primitive -- just as, following Einstein's special theory of relativity, a field is no longer regarded as the physical manifestation of vibrations in a mechanical medium, but recognized as a new physical primitive in its own right. 1 aBub, Jeffrey uhttp://arxiv.org/abs/quant-ph/0408020v201289nas a2200109 4500008004100000245002100041210002000062260001500082520102100097100001701118856004401135 2004 eng d00aWhy the quantum?0 aWhy the quantum c2004/02/203 a This paper is a commentary on the foundational significance of the Clifton-Bub-Halvorson theorem characterizing quantum theory in terms of three information-theoretic constraints (Foundations of Physics 33, 1561-1591 (2003); quant-ph/0211089). I argue that: (1) a quantum theory is best understood as a theory about the possibilities and impossibilities of information transfer, as opposed to a theory about the mechanics of nonclassical waves or particles, (2) given the information-theoretic constraints, any mechanical theory of quantum phenomena that includes an account of the measuring instruments that reveal these phenomena must be empirically equivalent to a quantum theory, and (3) assuming the information-theoretic constraints are in fact satisfied in our world, no mechanical theory of quantum phenomena that includes an account of measurement interactions can be acceptable, and the appropriate aim of physics at the fundamental level then becomes the representation and manipulation of information. 1 aBub, Jeffrey uhttp://arxiv.org/abs/quant-ph/0402149v100882nas a2200121 4500008004100000245007000041210006900111260001500180520048400195100002000679700001700699856004400716 2003 eng d00aCan quantum cryptography imply quantum mechanics? Reply to Smolin0 aCan quantum cryptography imply quantum mechanics Reply to Smolin c2003/11/113 a Clifton, Bub, and Halvorson (CBH) have argued that quantum mechanics can be derived from three cryptographic, or broadly information-theoretic, axioms. But Smolin disagrees, and he has given a toy theory that he claims is a counterexample. Here we show that Smolin's toy theory violates an independence condition for spacelike separated systems that was assumed in the CBH argument. We then argue that any acceptable physical theory should satisfy this independence condition. 1 aHalvorson, Hans1 aBub, Jeffrey uhttp://arxiv.org/abs/quant-ph/0311065v101116nas a2200157 4500008004100000245008100041210006900122260001500191300001600206490000700222520063100229100001700860700001700877700002000894856004400914 2002 eng d00aCharacterizing quantum theory in terms of information-theoretic constraints0 aCharacterizing quantum theory in terms of informationtheoretic c c2003/11/01 a1561 - 15910 v333 a We show that three fundamental information-theoretic constraints--the impossibility of superluminal information transfer between two physical systems by performing measurements on one of them, the impossibility of broadcasting the information contained in an unknown physical state, and the impossibility of unconditionally secure bit commitment--suffice to entail that the observables and state space of a physical theory are quantum-mechanical. We demonstrate the converse derivation in part, and consider the implications of alternative answers to a remaining open question about nonlocality and bit commitment. 1 aClifton, Rob1 aBub, Jeffrey1 aHalvorson, Hans uhttp://arxiv.org/abs/quant-ph/0211089v200957nas a2200109 4500008004100000245005800041210005700099260001500156520062000171100001200791856004400803 2002 eng d00aMaxwell's demon and the thermodynamics of computation0 aMaxwells demon and the thermodynamics of computation c2002/03/053 a It is generally accepted, following Landauer and Bennett, that the process of measurement involves no minimum entropy cost, but the erasure of information in resetting the memory register of a computer to zero requires dissipating heat into the environment. This thesis has been challenged recently in a two-part article by Earman and Norton. I review some relevant observations in the thermodynamics of computation and argue that Earman and Norton are mistaken: there is in principle no entropy cost to the acquisition of information, but the destruction of information does involve an irreducible entropy cost. 1 aBub, J. uhttp://arxiv.org/abs/quant-ph/0203017v100513nas a2200121 4500008004100000245007000041210006800111260001400179490000700193520013500200100001200335856004400347 2001 eng d00aSecure key distribution via pre- and post-selected quantum states0 aSecure key distribution via pre and postselected quantum states c2001/2/140 v633 a A quantum key distribution scheme whose security depends on the features of pre- and post-selected quantum states is described. 1 aBub, J. uhttp://arxiv.org/abs/quant-ph/0006086v300978nas a2200109 4500008004100000245003900041210003500080260001500115520067700130100001700807856004400824 2000 eng d00aThe quantum bit commitment theorem0 aquantum bit commitment theorem c2000/07/253 a Unconditionally secure two-party bit commitment based solely on the principles of quantum mechanics (without exploiting special relativistic signalling constraints, or principles of general relativity or thermodynamics) has been shown to be impossible, but the claim is repeatedly challenged. The quantum bit commitment theorem is reviewed here and the central conceptual point, that an `Einstein-Podolsky-Rosen' attack or cheating strategy can always be applied, is clarified. The question of whether following such a cheating strategy can ever be disadvantageous to the cheater is considered and answered in the negative. There is, indeed, no loophole in the theorem. 1 aBub, Jeffrey uhttp://arxiv.org/abs/quant-ph/0007090v400624nas a2200109 4500008004100000245004400041210004400085260001500129520030900144100001700453856004400470 1999 eng d00aQuantum Mechanics as a Principle Theory0 aQuantum Mechanics as a Principle Theory c1999/10/223 a I show how quantum mechanics, like the theory of relativity, can be understood as a 'principle theory' in Einstein's sense, and I use this notion to explore the approach to the problem of interpretation developed in my book Interpreting the Quantum World (Cambridge: Cambridge University Press, 1999). 1 aBub, Jeffrey uhttp://arxiv.org/abs/quant-ph/9910096v100707nas a2200133 4500008004100000245010200041210006900143260001500212520024500227100001700472700001700489700002300506856004400529 1999 eng d00aRevised Proof of the Uniqueness Theorem for 'No Collapse' Interpretations of Quantum Mechanics 0 aRevised Proof of the Uniqueness Theorem for No Collapse Interpre c1999/10/223 a We show that the Bub-Clifton uniqueness theorem for 'no collapse' interpretations of quantum mechanics (Studies in the History and Philosophy of Modern Physics 27, 181-219 (1996)) can be proved without the 'weak separability' assumption. 1 aBub, Jeffrey1 aClifton, Rob1 aGoldstein, Sheldon uhttp://arxiv.org/abs/quant-ph/9910097v1