From quarks to computing, this fascinating introduction covers every element of the quantum world in clear and accessible language. Drawing on a wealth of. Editorial Reviews. Review. "Few appreciate how deeply quantum physics affects so many.
The book uses a modern approach where two-state systems, called qubits or quantum bits, are treated from the first chapter on. The images really help with the understanding. The exercices have in general no solutions, but are so simple, that this should not be a problem. In summary, this is a fantastic book.
It is very accessible for the amateur scientist who does not shy away when seeing formulas.
But with simple formulas and exercises and crisp clear explanations, it is also a great book for physics students. Probably not the only quantum mechanics book. Topics like perturbation theory or addition of angular momenta are not treated at all. But it is a very understandable book, that can be worked through in a spare weekend.
After doing so, conquering one of the more advanced books will be so much easier. Motivation: 5. Read the complete review. This book belongs to the three-volume series by Nobel prize winner Richard P. Feynman and coworkers. The notable thing about the Feynman Lectures Volume 3 is that it is fairly accessible for non-physicists — much more than most other quantum physics books. Part of what makes the book so great is a multitude of images that accompany the text and greatly help with the understanding. Therefore for many people, this is the perfect beginner book when learning quantum physics and quantum mechanics.
You should be aware that the book contains formulas, but they are very accessible due the great explanations and images that accompany them. Physics students may complain that there are no exercises in the book. There is however a complete exercise book in addition to the three volume series. Further, since any physics book we know contains mistakes, we are really glad to have found this site with errata for Feynmans book. The book is fantastic in explaining the basic concepts of quantum physics.
It starts with thought experiments — that can be performed in reality — about the interaction of light or atoms with a double slit. It discusses the particle-wave duality in an easy to follow way and early on explains Heisenbergs uncertainty principle. It delivers a fantastic introduction for non-physicists that do not shy away when seeing formulas.
Together with the exercise book it is also a great start for physics students. The edition we review is a paperback edition and fairly inexpensive when compared to some other beginner books on quantum mechanics. Thus all in all, we can highly recommend this book. It is possibly the most extensive quantum mechanics resource, with together around pages. The length is due to the fact that quantum physics principles are explained in detail, and not as dense as in the book by Landau and Lifshitz. This makes it specifically suitable for beginners.
Each chapter contains a supplement with additional information that is helpful but can be skipped during a first read. This may actually help to get through all of the 14 chapters. The chapters in the first book cover particles and waves, the mathematical framework of quantum mechanics, the postulates of quantum physics, and simple systems.
It concludes with the harmonical oscillator and the angular momentum in quantum mechanics. The second book covers particles in a central potential, elementary scattering theory, and the spin of the electron. Then it continues with additon of angular momentum, stationary perturbation theory and the fine and hyper-fine structure of the hydrogen atom. The second volume concludes with approximation methods for time-dependent problems and systems of identical particles.
In short, Cohen-Tannoudji — quantum mechanics is probably the most complete book series about quantum mechanics there is. That alone makes it worth the money, and it is not inexpensive. But the old saying you get what you pay for applies here. With a great motivation, lots of images, an abundance of formulas, and many exercises, partly solved, this book deserves our blessings. Just like in the classical world we will have four numbers to describe the four processes that can occur to our box: we will have a number describing the transition from a duck to a turkey, from a duck to a duck, from a turkey to a duck, and a turkey to a turkey.
But and you could probably have predicted this these numbers aren't going to be like the positive probabilities in classical theory. In fact they are going to be numbers, but now they are allowed to be negative! So lets talk about an example.
You give the box to Quququ. What will be your new description of the box? Happy Thanksgiving! Notice that in the above calculation, we ended up with two numbers which when we squared them added up to one hundred percent. In other words we started with a description whose sum of the square of the numbers added up to one hundred percent and after Quququ got done performing his magic on the box, we still had a description whose sum of the square of the numbers added up to one hundred percent.
That's a nice property to have. We might even call such sets of four transforms "valid. In the quantum world we have a similar requirement on what those four numbers can be. I won't go into the details of these numbers as this would lead us too far astray. However I can tell you one simple way that you can check whether the set of four numbers is a transform which will never yield an description which yields probabilites which don't sum to one hundred percent, given that you always start with descriptions which yields probabilities that sum to one hundred percent.
Then if you apply the transform to those three different descriptions, if you get descriptions which all sum to one hundred percent after the transform, then you have a valid transform. So we have just described the quantum theory of a bit, which people call a qubit.
A qubit is a thing, which, when you look at it is either zero or one turkey or duck. Our description of this qubit is given by two real numbers, which when we square these numbers and add them together we get one. These numbers can be negative! If we open the box, then the probability that we see a 0 turkey is the square of the number used in our description for the 0 turkey , and the probability that we see a 1 duck is the square of the number used in our description for the 1 duck.
Transformations on our box can be performed which are described by four numbers, again these numbers don't have to be positive. The numbers describe the processes 0 goes to 0, 0 goes to 1, 1 goes to 0 and 1 goes to 1. The numbers can't just be arbitrary, but satisfy a constraint which guarantees that if a description before hand yielded probabilities which summed to one when we squared the appropriate numbers, then the description after the process will also satisfy this condition that we get numbers whose sum of squares sum to one.
We can, just like we did for our classical bit, string a bunch of transforms together and then we just need to do like we did before and calculate the new description at each step of a transform. Notice that in all of the above discussion, when we did the transform, we didn't look inside of the box. If we did, however, look inside the box, in either the classical or quantum case, we would see a duck or a turkey and we would immediately update our description to reflect this.
This is called the "collapse postulate" and is the source of a great deal of bickering in the quantum world. In the classical world no one bats an eyelash at updating their description. Most physicists take the point of view that you shouldn't bat your eyelash at the same process in quantum theory.
lnkscorp.com/best-phone-location-app-vivo-y91c.php But not all physicists agree on this. From a pragmatic point of view, you can use the above procedure without flinching.
So, now you've learned the basics of quantum theory. Was that ten minutes? The difference between the classical theory of a probabilistic bit and the theory of a quantum bit really aren't that severe. Instead of there being probabilities to describe the system there are these other numbers which can be negative and which square to probabilities these are called amplitudes by physicists.
Processes on the system change the description of the system in the classical case by probabilities of different transitions and in the quantum case by amplitudes which tell you how to update the quantum description. When we look inside of a box, in both cases we only see one of two outcomes and we then need to update our description appropriately. Fromt his perspective what makes quantum theory so interesting is that you can have things which act like negative square roots of probabilities.
There are classical analogies for these types of effects for example water waves can be thought of as adding when they collide, and if you consider everything below a fixed level negative, then the math needed to describe this makes us add and subtract numbers. Interestingly, however, these analogies are much harder to come by in the classical world when we insist that we be talking about probabilities and try to mimic these negative square roots of probabilities. Of course there is much much more to quantum theory than our above quick lesson.
Truely things get really interesting when you move from one quantum bit to two or more quantum bits. But I suspect that understanding the above could let you at least carry on a decent conversation with a theoretical physicists at a cocktail party. Well I guess that depends on whether the physicist has had too much to drink and is open to seeing turkeys and ducks I assume that in "three different descriptions which when we square the numbers and add them you get one," the "we" and the "you" are actually the same person and "them" refers to the squared value of all numbers.
Does "which" mean "such that"? Are "descriptions" and "numbers" synonyms? So does "three different descriptions which when we square the numbers and add them you get one" mean the same as "three different descriptions such that the squares of the three numbers add up to one"? And in the same way, does "transform descriptions which when we square the numbers and add them you get one" equate to "transform descriptions such that the squares of the numbers add up to one"?
And am I right in assuming that "transform" in this particular sentence is used as a modifier for "descriptions" as in "some transform-descriptions are. If I shorten "three different descriptions such that the squares of the three numbers add up to one" to X and shorten "transform descriptions such that the squares of the numbers add up to one" to Y, the sentence then says, "if you check whether X all turn into after the Y, then you are guaranteed you have a valid description for a valid transformation that can be enacted on the box.
Or could you maybe rephrase that? Sorry for the questions, but I really, really do want to learn something about quantum theory even if it takes a little more than ten minutes. All the other turkey and duck things are amazingly clear, but I just can't seem to understand this one sentence because I can't grasp how it is structured. Hey Julia, I've rewritten the offending paragraph. I knew when I was writing that section that it wasn't coming out correctly but I forgot to go back and fix it. Thanks Matt. It was fun to write, but I ran out of jokes at the end and towards the beginning too :.
After explaining the classical bit, you open the discussion of qubits by saying, "Now, for a quantum bit we need to use negative amplitudes, etc, etc. How about, instead, opening with "Now, if this is a quantum bit, then there's an experiment that shows this data Well, if we use these negative amplitudes, etc, etc.
This strategy makes it clear that there's a problem, which the theory of amplitudes solves, rather than just positing it axiomatically. I have a very little bit of experience indicating that your original approach works better with eager physics students who are happy to be told that nature is weird , and that the latter approach works better with normal people who tend to ask "What?
Why the hell would we do that? Okay, one more question. Suppose you had a real skeptic in your class, who said "Okay, I'm convinced that your quantum birdbit is not just a classical birdbit I think it's just got extra, hidden degrees of freedom! It's really a classical dial, or something. Of course, the correct answer to this is "Brilliant point! See me after class.
Of course the three qubit mermin contextuality argument is probably the simplest. I'm looking forward to the 3-turkey paradox! Or, heck, maybe I should just read Mermin's argument Keeping those C-numbers out of it seems like a nice move. Although I think it needs a bit of work to be publishable, have you considered Am. Feynman wrote an unusual little book titled QED, the Strange Theory of Light and Matter if I remember the title right that makes a pretty good attempt at it I'm sorry, but I hope that very few people read this, because you have written an explanation that confuses things more than it clarifies them.
You start with a long example of what is very clearly and explicitly a hidden variable situation. Your reader's state of knowledge of what is in the boxes may be statistical in nature, but, what is in the box is in fact a turkey, or else it is in fact a duck. There's a hidden variable that you don't know, but it actually is a chicken, or it's a duck, whether you know it or not.
Having now spent a page or two getting your readers to visualize hidden-variables clearly and explicitly, there's pretty much no possible way to move to quantum mechanics, since quantum mechanics is not a hidden variable theory. Unless possibly by saying "Now, to understand quantum mechanics, simply forget everything I just told you. More explicitly, in terms of your analogy, the possiblity that you could ever explain quantum mechanics vanishes when you get to this statement: "When we open a box we never see a half-turkey half-duck. Once you've told the reader that a superposition states "simply do not exist", you've essentially frozen them in the classical world.
They can, and do, exist, and understanding that they exist is, more than any other point, the key to understanding quantum mechanics. There's much truth in what Geoffrey A. Landis wrote. What I want to know is whether in generalized Bell inequalities, elliptically polarized turducken disproves reality, as well as locality.
I completely and totally disagree and believe that teaching students that wave functions are "real" is one of the biggest disservices ever rendered on physics students. Indeed I would claim it stopped my field, quantum computing, from every even being contemplated by at least twenty years. Superpositions do not exist except on the pieces of paper we write down to describe a quantum system.
Teaching students to believe that there is a wave function which is no different from the electromagnetic field instills into them all sorts of bad misconceptions. And point of fact, there does exist a local hidden variable theory for a single qubit contextual, of course. Of course I'm sure I won't win you over: you sound like an old school physicist : But if I can't win you over then maybe at least I could point you to something interesting to read which might make you yell at me less:.
You're right that Dave's description doesn't rule out hidden variables, and therefore fails to illustrate noncontextuality. But -- is contextuality the most important thing about QM? It's certainly one of the most deep and puzzling things about QM, and every student should realize at some point that QM is not compatible with hidden variables. A much more deadly fallacy, to me, is your conflation of "superpositions exist" with which I agree!
Rob Spekkens has done some interesting work, making a list of phenomena in quantum information theory that can and cannot resp. It turns out that the vast majority of them can; they depend only on roughly speaking information-disturbance relations.
It's quite hard to come up with a task that specifically requires contextuality. I also think that contextuality is hard to explain unless you've already spent some time thinking about hidden variables. So, if I only had 10 minutes to explain quantum, I'd probably skip contextuality. On the other hand, if I had another 10 minutes, I'd cover it, using I don't think I am -- the problem is that the word "exist" is ill-defined in this context .
Dave is, I think, restricting "existence" to measurable properties like "is it a turkey?
In the example shown, the motion is from left to right, but it could also have been from right to left. Learn more - opens in a new window or tab International postage paid to Pitney Bowes Inc. No—I want to keep shopping. Genevieve Graham. In b , the collision is not head to head and both balls move away from the collision with the total momentum shared between them.
Already, "exist" is getting ambiguous. It gets worse with quantum mechanics. The hidden variable issue was deepened by Bell's Inequality and Aspect's experiment, and then deepened again, as I hinted, with the elliptical polarization theory that undercuts Bell but threatened "realism" in QM. Robin Blume-Kohout brings in the difficult questions of the metaphysics of Mathematics, the metaphysics of Physics, and Wigner's paper on the "the unreasonable efficacy of mathematics in explaining the physical world.
I February Richard Hamming , who was neither a physicist nor a philosopher of mathematics but an applied mathematician and a founder of computer science, reflects on and extends Wigner's Unreasonable Effectiveness, mulling over four "partial explanations" for it. A different response, advocated by Physicist Max Tegmark , is that physics is so successfully described by mathematics because the physical world is completely mathematical, isomorphic to a mathematical structure, and that we are simply uncovering this bit by bit.
In this interpretation, the various approximations that constitute our current physics theories are successful because simple mathematical structures can provide good approximations of certain aspects of more complex mathematical structures. In other words, our successful theories are not mathematics approximating physics, but mathematics approximating mathematics.
But, of course, in other parts of the Multiverse I agree with him. In yet others, I am him. But do I exist somewhere as a superposition of me and him? Of me and you?
I apologize here that It's hard to discuss QM without implicitly falling into an interpretation, because the language varies depending on the interpretation used, although the underlying mathematics is the same. I'll do my best to use interpretation-free language, but don't count on it Basically, when you make a measurement look inside the box, in your example , the probability of the measurement giving a result R is the projection of the initial state into the eigenstates defined by the measurement operator; but once you have made the measurement, the probability of the system being in that state is unity.
Right so far? So by definition, of course that's not what you will ever see. And this is of course true in the case of a box containing a turkey or a duck. If you don't like K0 mesons, the trivial in fact, nearly classical case is a polarized photon.