Foundations of Quantum Mechanics: An Exploration of the Physical Meaning of Quantum Theory (Undergraduate Lecture Notes in Physics)

Quite frankly this is a book that is a must have in anyone's library concerning Quantum Mechanics.When I first heard of it it looked intriguing but as a layperson with limited experience with math I was wondering if I could really understand it all. I will say this, though the math is written in a language that is often beyond me the author somehow summarizes, reiterates, and pictures things in such a way that quite frankly I had a hard time being lost and he does this without any feeling of repetitiveness. Even the math that I didn't know I often understood quite easily. I honestly doubted whether that could be done and well I think this book shows it can and for that reason I can highly recommend it even for just a very interested layman such as myself. He covers topics not usually discussed and clears away confusions and misconceptions concerning Quantum Theory.This book is divided into 9 Chapters they are as follows:1. Pre-Quantum Theories: This Chapter was very eye-opening to me. I've read other books on Quantum Physics that talk about Pre-Quantum Theories but seldom do they link them to Quantum Theory. For example Travis will often mention things that are similar or sort of precursors to concepts in Quantum Theory which is extremely helpful as a bridge to it and gets you familiar to concepts to come so that you already have the resources to understand and picture it.2. Quantum Examples: This is where he then takes you to Quantum Theory and explains many things in Quantum Theory that were both similar to Pre-Quantum Theory but also what separates it in general so is an overview. You learn more key concepts. The pictures here and the fact that he taught from Chapter 1 the way he did makes this much easier and fun to understand.3. The Measurement Problem: This is where it really starts to take off. Armed with what you learned, Travis introduces a problem that has plagued Quantum Theory. You also see many examples of thought experiments that were implored to understand the issues and this again makes it quite easy to grasp. He also talks more about issues of Hidden Variables and of an interpretation favored by people like Einstein called the Ignorance Interpretation. These are keys for understanding later solutions and you get a glimpse of the Paradoxes if you will in Quantum Theory.4. Locality Problem: This to me was one of the most fascinating as Travis goes even more into history and the thoughts of people like Einstein and Bohr, particularly concerning the EPR experiment. It is often stated that Bohr bested Einstein here but Travis dispels that quite convincingly and shows that Bohr hardly understood Einstein and when he did he did little more than give convoluted sentences that helped nothing. Travis also implores David Bohm and John S. Bell to better explain the experiment with Bohm's easier Reformulation of it and Bell's Re-telling of these events which again has Travis reiterating things but in a more clear yet accurate way that you will feel the force of the mystery and through these great men.5. The Ontology Problem: I've heard of this problem but yet again many things are brought up that are seldom brought up that I was quite pleased with this section. Travis shows that merely having a wave function that evolves according to the Schrödinger Equation will not solve the issues as a matter of fact it contradicts experiment. Moreover he talks about Schrödinger's attempt to explain things in a real empirical way instead of just talking instrumentally and some issues encountered.6. Copenhagen Interpretation: Here the Standard view of Quantum Physics is explained. Interestingly he shows the differences between certain Fathers of it such as Bohr and Heisenberg thus having one see the confusion involved. This is interpretation is not only confused and unintelligible at times but also what it says about reality if anything isn't even agreed upon by its Fathers. He shows Bohr's confused/muddled reply to the EPR experiment in more detail and contemporary perspectives on it. They often give lip service to the Standard interpretation that the particle wasn't anywhere till observed in which it is compelled to a definite outcome. However when pushed they tend to fall back to Agnosticism and stop the conversation. As Travis points out Science is more than just shutting up and calculating and that this isn't a matter of idle philosophical speculation, indeed it is the Copenhagenists who should be doing just that in the "Shut up and Calculate!" Approach as they often dogmatically hold to Bohr's Philosophy.Pilot-Wave Theory: The Copenhagen camp said that it couldn't be done, that one couldn't give an accurate and real and clear physical description of the world in terms of Quantum Theory. Travis here shows they were simply too dogmatic and wrong. The Pilot-Wave Theory is a Theory that has a clear Physical Ontology that avoids the measurement problem and completes Quantum Theory. It was unfortunately abandoned by de Broglie and was picked up and advanced by David Bohm who completed it. I learned that it was a Theory that starting with De Broglie was prior even to the Copenhagen Interpretation and after Bohm's completion of it was taken back up by De-Broglie who wrote a forward for David Bohm's work on it. Travis points out some issues such as whether the abstract spaces can be given real physical descriptions or not and that it is incompatible with Einstein's local Relativity Theories because of this Einstein did not like this theory.8. Bell's Theorem: Here is where John Bell takes more of a center stage. Here Travis shows that Locality like that of Einsteinian Relativity is in fact violated as the Pilot-Wave Theory says but not leaving it at that Travis goes even on to explain to my shock a rival Relativity Theory of Hendrik Antoon Lorentz in its updated form called neo-Lorentzian Relativity that is infact consistent with all the experiments including non-locality. Placing Pilot-Wave Theory right before this was ingenious as you can see very clearly the non-locality issue in Bohm and its problem with Einsteinian Relativity, here Travis points out that these aren't much problems at all. Moreover Bell unlike Bohr was clear and unlike Einstein was concise this Chapter due to that is a breath of fresh air.9. The Spontaneous Collapse Theory: This Theory is similar to Pilot-Wave Theory and the Copenhagen Interpretation almost like a hybrid. Like Pilot-Wave Theory it is non-local and realistic, unlike it but like Copenhagen it is Indetermistic and has collapse. However it isn't really a Quantum Theory but an alternative since the maths are different and due to this it can be distinguished and falsified. It has issues also in being ad hoc, also how things are in the real world in terms of Ontology differs depending on the version either Massy or Flashy. It has an interesting feature of being compatible with Einstein's Relativity theories however.10. The Many-Worlds Interpretation: I already wasn't a fan of this interpretation due to Philosophical reasons but the Empirical reasons against it are much more formidable than even I thought. Proponents often implore it as being the simplest in terms of the maths as it uses only a wave-function without other beables and such but tries to keep it consistent via multiple branches, unfortunately Travis points out that again only having a wave-function has various issues all of which to me seem very problematic. One would need to take it as being merely a mathematical description without a physical base, but then you would need to add extra Ontology which takes away its supposed simplicity or one would have to take the macroscopic world as illusory or other. Also due to its many-worlds so to speak it has problems with probability that seem to have no good solution. Moreover while proponents claim it is a local Theory, Travis points out that this is extremely questionable, whether it is local, non-local or as it seems just unclear is very much unresolved.I think this book was extremely fair and written in such a way that you can both understand and enjoy. It also has end projects which I really enjoyed as it helps one to study and contemplate what was read. I noticed for example how wrong Wikipedia entries often get it as Travis will sometimes use it as examples. The only issue I found was lack of an index but with such an array of amazing and clear information this book cannot be overlooked.If you haven't decided on it yet I give it a resounding yes!

Norsen's treatment of locality is the best I have ever seen, and quite persuasive. The take-home is that the failure of local causality was present from the first in QM, although Schrodinger tried for a while to deny it. Certainly Einstein knew this from the first, because the collapse of the wave function is a non-local event. Einstein did not like this failure and the EPR paper was an attempt to show QM is incomplete (i.e., there are hidden variables). Now here I think Norsen drops the ball (or correct me, dear reader, if I am wrong), because he claims that Bell's 1964 paper is really a proof of non-local causality, not the impossibility of hidden variables. What this paper shows is that there is no locally causal hidden variable model. This does NOT follow from the Copenhagen interpretation of QM, from deBroglie-Bohm, or anything else.Norsen's untangling of locality, hidden variables, the EPR argument, and deBroglie-Bohm. can be summarized as follows (my summary, not Norsen's): EPR show that local causality implies realism; realism means hidden variables; Bell shows that QM plus hidden variables contradict local causality; Bohm shows that hidden variables are possible in QM; experiment confirms Bell. Hence local causality is false---QM is in conflict with special relativity.I do not agree with his defense of Bohm's theory. There is no evidence for it and it does not extend to relativistic quantum mechanics. Moreover, it models may particles (e.g., electrons in the ground state of an atom) as having zero momentum. This is a lot worse than saying there are several "superposed" momenta. In the end, this theory s just a balm for some people's metaphysics. Occam's razor favors the more empirically founded Copenhagen interpretation, with all of its ambiguities and clearly provisional nature.Norsen provides a spirited defense of the Many Worlds theory, but it also must be rejected because there is no evidence for it. It is not outlandish, as some would have it (the Universe increases its degree of superposition over time, but the various Hilbert basis states are in configuration space, not physical space, so there are no real "splitting" of universes into "parallel" universes as some would have it. The"relative state" formulation is elegant, but this approach cannot handle probabilities.I wish Norsen had dealt more with decoherence, which is barely mentioned in the book.

I have used Norsen' s book as main text for my recent course on theFoundations of Quantum Mechanics which I have taught at Goethe-University Frankfurt (Germany) during the winter semester 2023/24. The course consisted of one two-hour lecture per week. In addition,I met with the students for an extra hour per week where we solved some exercise problems and the students gave talks on special topics related to the interpretation, history or application of quantum mechanics. . With some minor omissions, during the 15 weeks of the winter semester I have covered the entire contents of Norsen's book. The book is very carefully written and gives a nice summary of the problemsrelated to the interpretation of QM and the proposed solutions. I also like about this bookthat Norsen describes the proposed alternatives to the orthodox interpretation (De-Broglie-Bohm, spontaneous collapse, many-worlds) in an unbiased way. Only at the end of the book he reveals that he tends to favor De-Broglie_Bohm. This is not only a great book for teaching, but is also very well suited for self-study. As a condensed-matter theorist I have been happy with the "shut-up-and-calculate" interpretation of QM all my scientific career. Norsen's book has changed my attitude towards QM -- although I am still happily calculating....

This is a very interesting and accessible book on the foundations of quantum mechanics.The book is highly simulating and helps you understand difficult concepts with great ease. It starts by clearly explaining the notions of configuration space and locality in the context of classical physics. Then, after introducing the quantum formalism and some simple examples, the book explains with a cristal clear clarity the three main difficulties in Quantum Mechanics: the measurement problem, the locality problem and the ontology problem. Then, the book provides conceptual, formal and highly objective explanations on the Copenhagen interpretation, Bell’s theorem, the de Broglie Bohm pilot-wave theory, the GRW spontaneous collapse theory and the Everett many-world theory. This is a must read book for anyone who has some background in physics and desires to understand the perplexing problems of the foundations of quantum mechanics. I greatly enjoyed reading this book and, I highly recommend it.

Disclosure. I am a Ph.D. student working on foundations of quantum mechanics, and I recently wrote a letter to the author asking for some help with my work. My decision to reach out to him came partially from my opinion about the book.The book is a deep introduction to the foundations of quantum mechanics. It covers the measurement problem, the problem of how to physically interpret the formalism of quantum mechanics, quantum non-locality, Bell's theorem, and the most popular/discussed interpretations of quantum mechanics (Copenhagen, Bohmian mechanics, objective collapse, and many worlds). In my opinion, it is the best introduction to the foundations of quantum mechanics at the moment.The book has a good balance between formal rigor and conceptual clarity. It does not shy away from the formal aspects, and it does not waste time on insignificant details. At the end of each chapter, there are engaging problems that allow you to go deeper on many issues.I think this book can be used to design courses on the foundations of quantum mechanics. I will certainly use it for that purpose.

I would highly recommend this book to anyone interested in the foundations of Quantum Mechanics. It first introduces us to the conceptual issues that have plagued Quantum Mechanics from the beginning, namely the measurement problem, the locality problem, and the ontology problem. It then explores various interpretations of Quantum Mechanics and how they fare with respect to these issues.Travis writes eloquently and with ease. Probably the biggest merit of this work is the clarity of exposition (on topics which often leave readers perplexed and confused).For students of Quantum Mechanics, this is the perfect place to start. For those already immersed in the topic, an invaluable reference and perhaps a challenge to their views.I thoroughly enjoyed reading this book and, once again, highly recommend it!

Excellent introduction to the foundational issues of interpreting quantum mechanics, including the much-neglected ontology problem, and a clear and forceful explication of the locality problem, in addition to the measurement problem. Should be read by all students of quantum mechanics!Ebook version unfortunately is not well formatted, though still completely readable. Would recommend the hardcover textbook. But the content is excellent!