Qm Definition and 1000 Threads

I'd like to go over what Quantum Teleportation is, how it works, and the absolute basic fundamentals of quantum mechanics. This thread may contain some relatively advanced concepts, but this is what I've learned over only a couple months. This only scratches the surface of the tip of the iceberg...

I think I almost get there, but something's not right, and need your help. if F(ψa,ψb) is a complex valued (scalar) functional of the two variable vectors ψa and ψb with linearity properties. Show that F can be represented as an inner product F(ψa,ψb)=(ψa, Aψb), for every ψa,ψb and the previous...

What are the advantages of RQM against QM? If RQM is more accurate that QM then why use QM (yet only if it is) or better said if it is more complete? I read Paul Diracs lectures 1-4 and he talked about relativistic quantum mechanics and quantization of flat and curved spaces in lectures 3-4, so...

Homework Statement In a spin-\frac{1}{2} system all particles are in the state |\psi\rangle. 3 experiments performed and are separate, the results are as follows: Particle in state |\psi\rangle, measured S_z = \frac{\hbar}{2}, with P=1/4 Particle in state |\psi\rangle, measured S_x =...

1) When we learn about MO theory, we learn that there are different ways to combine atomic orbitals to find the molecular orbitals for a molecule. However, going back to the fundamental/physical meaning of orbitals, orbitals are the wavefunctions. Wavefunctions do not have any physical meaning...

im planing to educate myself . on quantum mechanics/physics . so could you please refer me 1 good fundamental QM text / reference book . and 1 book that covers all the theories on time ( space time , time line ...)

I would like to reopen a discussion on assertions made by David Mermin such as: “There is no conceivable way to assign such instruction sets to the particles from one run to the next that can account for the fact that in all runs taken together, without regard to how the switches are set, the...

I'm beginning the wondrous process of applying to graduate schools. Long story short in my last semester of undergrad stuffs I took Modern Optics instead of taking Quantum Mechanics II. Modern Optics is still a 400 level course but at the time I wasn't considering applying to physics graduate...

I'm a senior physics major in the first semester of a two semester QM sequence using Griffiths. All of the physics majors talk about how great quantum mechanics is and how it is the pinnacle of the undergrad physics degree. The upper level physics courses seem to build up the foundation that one...

"Determinism often is taken to mean causal determinism, which in physics is known as cause-and-effect. It is the concept that events within a given paradigm are bound by causality in such a way that any state (of an object or event) is completely determined by prior states" -- from wiki Does...

I am in a graduate class taught by a super genius who advises us to just keep rereading Gottfried (it's the sole text and all HW comes from it) if we don't understand. Me and my classmates feel like we aren't learning QM because the text is inscrutable and the HW isn't teaching us anything...

I keep hearing that QM and GR don't play well together. For example, a singularity, a result of GR, is small enough for QM to apply but...it doesn't. I was hoping someone could explain exactly where the "equations fail." Unfortunately I'm so ignorant in this subject matter that I can't be...

http://www.falstad.com/qm1d/ is a really good way of getting a feel for the dynamics of a single particle in a variety of potential wells. Does anyone know of an equivalent (hopefully free) program for multi-particle systems? Dustin Soodak

Hi everyone! I am an undergraduate student interested in quantum physics. I want to do a project in quantum but do not know how to come up with a good idea to start with. I have read the book Zettili and most of the book Cohn-Tannoudji. so I think I am able to work on a good idea. Any idea...

At the core of the quantum concept by Planck was the black-body radiation, then: electromagnetic waves, whose amplitudes are electric and magnetic fields, but when one follow the developments and one comes to the Schrödinger waves, now their amplitudes are not of that kind but related to...

I have a problem concerning gauge invariance in QM. QM should be invariant of electromagnetic gauge. However, the following two physically equivalent vector potential: 1. A = (-\frac{1}{2}By, \frac{1}{2}Bx, 0 ) 2. A = (-By, 0 , 0 ) generates the following hamitonian: 1. H =...

Hello, I'm taking a break from school this semester to work and pursue interests that I have let fall to the way-side due to studies. I'm an EE major but physics is sort of a "hobby" that I enjoy learning past what is required for my classes. I would like to take a QM course next year some...

Hi, I had a look at Susskinds explanation about QM and this is pretty strange from my point of view. Video: Around minute 36. He says that if there is no measurement after the electron/photon/whatever is going trough the slit and if you would reverse time the whatever would come...

Relativity and continuum I have read contrasting things about the issue. Can you explain briefly why the assumption of discrete space and time is absolutely incompatible with relativity? What is the main problem? Lorenz invariance or what? Thanks

I can tell this is simple, but I'm just not seeing it: (pages 146-147) Radial equation = d^{2}u/dp^{2} = [1 - p_{0}/p + l(l+1)/p^{2}]u Later... (having stripped off the asymptotic p^{l}e^{-p} parts) d^{2}u/dp^{2} = p^{l}e^{-p}{[-2l-2+p+l(l+1)/p]v + 2(l+1-p)dv/dp + p*d^{2}v/dp^{2}} And he...

Hi all! I am wondering if there is an interpretation of QM where the future is "set in stone" (for lack of a better phrase). It can be unknowable (the future)...but it shouldn't be random in any way. Edit: basically I'm looking for a hard determinism type of QM interpretation.

Hi. I'm a self-learner, and I'm doing an introductory QM from Griffiths. My question is should I memorize all the derivations and proofs in the book or I just have to memorize the final results? Another point is that I have nobody to ask about my solutions to problems or to help me in the hard...

I found this article recently on Wired.com and thought others might like to see it. Basically its revisiting Bohmian Mechanics in the context of fluidics and how everyday objects can have quantum-like behavior explained via pilot waves: Fluid Experiments Support Deterministic...

Hi there: I am reading a book (Atom-Photon interaction by Claude Cohen-Tannoudji, Page 448) and the following things gave a big headache. (1) Is there a density equation in Schrodinger Picture. because I encounter one, like: ##i \hbar \frac{d \sigma}{dt}=[\hat{H}, \sigma]## and...

Hi I am currently trying to learn quantum physics using David J. Griffiths textbook. However, in chapter 4 and 5 he lost me a little. I would prefer a textbooks that handholds me through solving the PDE's rather than just giving me the solutions. The topic of these chapters are: QM in three...

Forgive the title if improper, the language of QM is not my native tongue. :) All scenarios where QM is invoked that I am used to involve parameters that do not commute, but I suppose I've never truly asked myself if QM is necessary to describe scenarios wherein you are not concerned with this...

because of the probabilities located in the equations of QM, wave functions and uncertainty principles? Instead of exact values for particles in QM there are potential ranges of values, these ranges over greater 'theoretic energy value difference' (like a range instead of an exact value of 5...

I am wondering why if quantum mechanics is self consistent, equal to itself, and thought to be equal to reality, and the same can be said of the theory of Gravity, why the separate theories and equations can not be plugged through a process of guess and check/trial and error by supercomputers...

Homework Statement The mathematical complication I'm having comes from Problem 1.9 in Griffiths' Introduction to Quantum Mechanics. I'm just going to provide the mathematics here: The norm squared of the wave function is \ \left|\Psi \right|^{2} = (\frac{2am}{h\pi})^{1/2}...

Homework Statement I've been told that the operator ##\hat n \cdot \hat {\vec L}## has the same eigenvalues as ##L_z##. Later I've been told that it has the same eigenvalues as any component of ##\hat {\vec L}##. But I am a bit confused, as far as I understand the eigenvalues of ##L_x##...

Hey guys, I studied with this book now for some weeks. The last few days I solved a lot of exercises to prepare for the exam, but unfortunately I can not check if my answers are correct. There are no solutions in this book. Does anyone know if the solutions are availabe somewhere? This would be...

Could anyone recommend an up-to-date and not too advanced book or online notes on applied quantum mechanics or quantum technology? Most of my books are quite old and I need to have a basic understanding of the subject for a work experience project in six weeks time. Thank you!

Hi, my name is Tristan Barrow, I know this forum has gotten a lot of questions like this but none of them really fit my particular needs so I thought I would ask it again. Do the math subjects I am interested in lead me to Quantum Mechanics? If not what would be the best place for me given...

Having done a course in QM I still find the first two chapters of Landau Vol. 3 extremely dense. Is there any nice reference that closely parallel's Landau's development, just giving more details/examples? Literally just the first two chapters, but done almost the exact same way + details/examples.

I read today about Ehrenfest's theorem on mechanical systems (with adiabatic hamiltonian evolution). Well in the book, it says that the Ehrenfest's theorem was also used by Bohr and Sommerfield who proposed the quantization of quantities such as: \oint p dq According to Bohr-Sommerfield's...

I'm looking at how a l j1,j2,jm> state can be operated on by the ladder operators, changing the value of m, and how this state can be expressed as a linear combination of l j1, j2, m1, m2> states. Where the following relationships must be obeyed (x2): m=m1+m2 l j1-j2 l ≤ j ≤ j1+j2 So...

Homework Statement The task is to calculate the transmission probability when E<V0 given that the step potential barrier is of infinite length. Homework Equations So far it seems simple enough. For region I, where x<0, (we're assuming, as usual, that the particles/ waves are coming...

This is the sort of thing that should be easy but my brain has blanked due to be overloaded in other areas of Physics. I've tried a great deal of different approaches but I'll walk though the one that led closest. I assumed that \hat{A} and \check{B} where both hermitian so there...

I have read in a classical EM book: " The picture of conduction electrons moving freely in conductors is an oversimplification, although it gives a good qualitative description of many of the properties of electric current. In some materials the current is due to the motion of carriers...

Hi All, Would it be reasonable to state that, together with the quantum mechanics appearance, there appeared also a new way to calculate probabilities? I have never heard any teacher pointing out that QM has brought a new probability method. They speak of amplitudes of probability but...

I'm trying to understand what is the correct rule for the Dirac delta normalization of a non-integrable wave function, and can't seem to find any decent references. My issue is with achieving the proper dimensionality of the resulting wave function. This would be length-1/2 for the states of a...

I am starting to review to go back to grad school. One topic I didn't feel like I did so hot in as an undergrad is QM. I want to go through a textbook myself. I was thinking about "Principles of Quantum Mechanics, 2nd Edition" by Ravi Shankar. Are other books that might be good for me or...

Hello, As written, I am wondering if the causality principle gets violated in QM. Do virtual particles violate the causality principles? Do instantaneous events violate the causality principle? Thank you in advance.

I have a basic question that still is not clear to me. In QM, various operators are generators of something (ie. momentum is a generator of linear translations, Ang. Mom the generator of Rotations and such) Question 1: Let us look at L, or a component, say Lz. When we operate on a...

Homework Statement A particle of mass m moves in a 1-D Harmonic oscillator potential with frequency \omega. The second excited state is \psi_{2}(x) = C(2 \alpha^{2} x^{2} + \lambda) e^{-\frac{1}{2} a^{2} x^{2}} with energy eigenvalue E_{2} = \frac{5}{2} \hbar \omega. C and \lambda are...

Leonard Suskind's new book on Quantum Mechanics: The Theoretical Minimum is now available. I bought a copy at the local Barnes and Nobles. It looks pretty good after briefly scanning it but I'll know more once I begin reading. Can it be placed in the list of recommended books that Greg started...

The probabilistic nature of QM seems apparent(in theoretical formulation as well as experimentally), then why do most of the physicists give the credit of in-determinism to the nature itself and look for many worlds, abruptly collapsing observer conscious experiment setups, and the likes...

Hello all, I'm taking my first actual quantum course this semester. I went over "briefly" some quantum mechanics Fall of 2012 in a Modern Physics course during my sophomore year, currently I'm a junior. To get straight to the point, this course is making me miserable. I had high hopes for...

Hey guys, I study biophysics, so maybe this is a sophomoric question. I've done a cursory, albeit fruitless search of the forums and the web, I think I don't know how to properly ask the question... I was wondering if there is some sort of limit -- I would assume a given mass of an object...

I know that transistors work using QM, but I don't know how, can someone explain this to me?