Quantum physics Definition and 728 Threads

Hi all, below is my attempt. Pretty new at quantum so do correct me if I'm wrong. Thanks i) Since 1nm is the wavelength of the electron, Wavelength = 1nm, 1nm=2(2nm)/n , n=4? ii) - iii) From n=1 to n=4, Change in E = 15h^2/8mL where m is the mass of electron and L is 2nm? From the change in E...

Hello friends. I was thinking that if you study physics, you learn first the basic math to understand it, but you don't go beyond, or deeper, you just learn the minimum math necessary to understand what you are going to see in your physics leassons. For example, if you are going to learn...

I am a second year Physics student. I am keen to know more about the space(strings) and everything around me and how they interact with each other(the true behind energy). I really think studying physics was my perfect choice I have made and being part of Physics Forums too. Working on...

Coherent Quantum Physics: A Reinterpretation of the Tradition by @A. Neumaier https://www.amazon.com/dp/3110667290/?tag=pfamazon01-20

A new mathematical result seems to have very important implications for quantum mechanics. https://www.nature.com/articles/d41586-020-00120-6?fbclid=IwAR0DxBdyEW10Te3C1Vfyn17TZshyCRrO8nX6D5Iq4CGahZ_DXgfeQ_Ii0Z8 The original paper is a very hard read: https://arxiv.org/abs/2001.04383

Hello! I'll be entering my second semester of my junior year of my Physics Degree. My uni doesn't have a bad physics program, but it's really small so I have to take my upper level classes as soon as they're offered or I won't take them for another 2 years or so. They are on a cycle so I will be...

Is there any evidence that Panpsychism may hold its own in the quantum world? What quantum physics principals violate the ideology of Panpsychism? This is meant to be fun. I am curious what other people think.

Homework Statement:: Consider an electron trapped in a one-dimensional finite well of width L. What is the minimum possible kinetic energy of the electron? A) 0 B) Between 0 and h^2/8mL^2 C) ≈h^2/8mL^2, but it is not possible to find the exact value because of the uncertainty principle D)...

Because I do have a background in the latter it was originally very difficult for me to understand some aspects of QP (quantum physics) when I initially learned it. More specifically whenever probabilities were involved I couldn’t really make full sense of it while I never had any problems...

From the point of view of science and physics, is the simulation hypothesis true? What is the scientific refutation of this hypothesis? What do physicists say about this?

I am going to get laughed out of this forum but at least it will put my mind to rest when this happens. I've been thinking about this for a few years now and what better place for an answer than a physics forum? Amongst many other things I have read A Brief History of Time seven or eight times...

I calculated the complex conjugate of both the given wavefunctions. For ψ1: ∫re^((-2)mod(r)x)dx=1 with upper limit ∞ & lower limit -∞. I replaced the upper and lower limit after breaking down the function inside integration as follows- r*∫e^(2rx)dx from -1/r to 0 and r*e∫e^(-2rx)dx from 0 to...

Brief Description of New Quantum Forum Structure A common topic of discussion regarding quantum mechanics is the foundations of QM as a theory structure and different interpretations of QM. These discussions are of interest to many PF members, but they present some unique challenges since they...

Is classical physics independent from quantum physics? Or is classical physics an approximation derived from quantum physics? Is it dependent on interpretations? What quantum interpretations support the latter above?

Hey guys, I want to build a strong and straight plan for my next years of studying and once finish I am able to do something on my own and come up with crazy ideas and actually test them, build some awesome algorithms, all that cool stuff, but I'm kinda stumble so it would be nice if someone...

Summary: CordFriebe et al. Has anybody read this book? I am wading through this tome for the second time. Was wondering what others whom might have read it thought. https://www.amazon.com/dp/3319783548/?tag=pfamazon01-20

Please see this page and give me an advice. https://physics.stackexchange.com/questions/499269/simultanious-eigenstate-of-hubbard-hamiltonian-and-spin-operator-in-two-site-mod Known fact 1. If two operators ##A## and ##B## commute, ##[A,B]=0##, they have simultaneous eigenstates. That means...

In Quanta Magazine there is article on this link...

In this problem I am supposed to treat the shelf as a weak perturbation. However it doesn't give us what the perturbed state H' is. At the step V(x) = Vo, but that is all that is given and isn't needed to determine H'. This isn't in a weak magnetic field so I wouldn't you use H'=qEx and then...

What does quantum physics say about the simulation hypothesis?

Using the fact that Pa ∝ |α|^2 and Pb ∝ |β|^2, we get: Pa = k|α|^2 and Pb = k|β|^2 Since the probability of measuring the two states must add up to 1, we have Pa + Pb = 1 => k = 1/(|α|^2 + |β|^2). Substituting this in Pa and Pb, we get: Pa = |α|^2/(|α|^2 + |β|^2) and Pb = |β|^2/(|α|^2 + |β|^2)...

Is there a relationship between the momentum operator matrix elements and the following: <φ|dH/dkx|ψ> where kx is the Bloch wave number such that if I have the latter calculated for the x direction as a matrix, I can get the momentum operator matrix elements from it?

Hi all, Given that the question: From what i know , I am not sure how this equation can help me estimate the von-klitzing constant? Or is there another way? Thanks!

Two questions, where the 1st is related to previous discussion regarding thes couplings: The selection rules for LS coupling is quite clear - it's based on calculating the compatible electric dipole matrix element. However, in the case of jj coupling we end up with different selection rules...

1) I know that the binding energy is the energy that holds a nucleus together ( which equals to the mass defect E = mc2 ). But what does it mean when we are talking about binding energy of an electron ( eg. binding energy = -Z2R/n2 ? ). Some website saying that " binding energy = - ionization...

Can anyone elaborate on Deutsch's attempt to solve the incoherence problem? He postulates a continuously infinite set of universes, together with a preferred measure on that set. And so when a measurement occurs, the proportion of universes in the original branch that end up on a given branch...

Greg Bernhardt submitted a new blog post A Classical View of the Qubit Continue reading the Original Blog Post.

Homework Statement Homework Equations I've used: ##mv^2/r## = Centripetal ##q^2/r^2## = Force pulling the electron in A bunch of other ones which I really can't be bothered listing. The Attempt at a Solution I managed to get Part A of the question using pretty simple methods. I set ##mv^2/r...

Is it possible that evolution happens in quantum jumps as no intermediate lifeforms were ever found? Analogous to an electron jumping from lower energy level to higher energy level without intermediary states.

A complete description of the thermal interpretation of quantum physics can be found in my just finished papers (for the bare bones, see Section 2.5 of Part II) Foundations of quantum physics I. A critique of the tradition, Foundations of quantum physics II. The thermal interpretation...

Hi there, Question from a biologist with very poor background in physics, but willing to understand quantum physics. I think quantum entanglement shocks everyone, even if it has been proven right. I would love to know if there is any hypothesis or crazy theory out there to explain why or how...

Greg Bernhardt submitted a new blog post Against "interpretation" Continue reading the Original Blog Post.

According to QFT, are there hydrogen bonds or Van der Waals force? Or this an outdated concept of classical physics?

My question is: What is the contribution of Quantum Physics to the discovery, of the transistor? In Adam Becker's book What is real? I read that, "the discovery of quantum physics in the early twentieth century led directly to the [discovery] of silicon transistors..." He implies that, the...

Greg Bernhardt submitted a new blog post Wigner's Friend Continue reading the Original Blog Post.

Hello all, The second quantization of a general electromagnetic field assumes the energy density integration to be performed inside a box in 3D space. Someone mentioned to me recently that the physical significance of the actual volume used is that it should be chosen based on the detector used...

Greg Bernhardt submitted a new blog post The Unreasonable Effectiveness of the Popescu-Rohrlich Correlations Continue reading the Original Blog Post.

There is so much discussion about what does "really happen" at the quantum level, because we can not directly observe the most minute details of quantum systems, and much is left to inference and to the "interpretations". Does the system really collapse by transferring state information to its...

Let me present what I think is the understanding of a particular situation in quantum mechanics, and ask people to tell me whether I am right or wrong. To say that everything happens randomly in QM would be misleading at best. We get at least statistical prediction. But discussions such as the...

Homework Statement How should I calculate the expectation value of momentum of an electron in the ground state in hydrogen atom. Homework Equations The Attempt at a Solution I am trying to apply the p operator i.e. ##-ihd/dx## over ##\psi##. and integrating it from 0 to infinity. The answer I...

In @A. Neumaier 's excellent Physics FAQ, he notes under "Are electrons pointlike/structureless?" that "Physical, measurable particles are not points but have extension. By definition, an electron without extension would be described exactly by the 1-particle Dirac equation, which has a...

Homework Statement Is the following matrix a state operator ? and if it is a state operator is it a pure state ? and if it is so then find the state vectors for the pure state. If you don't see image here is the matrix which is 2X2 in MATLAB code: [9/25 12/25; 12/25 16/25] Homework...

Every time I watch another YouTube video about the "spooky" stuff or multiple slit experiments they never have a proposed explanation of how they work. It would seem to me that if you had a proposed idea then people could think of experiments to prove or disprove the idea. But with no ideas it...

I'm having trouble with trying to find the expansion coefficients of a superposition of a Gaussian wave packet. First I'm decomposing a Gaussian wave packet $$\psi(\textbf{r},0) = \frac{1}{(2\pi)^{3/4}\sigma^{3/2}}\text{exp}\left[ -\frac{(\textbf{r} - \textbf{r}_0)^2}{4\sigma^2} + i\textbf{k}_0...

I would love to know about not only the rankings of the universities (Which I see a lot) but more what makes each one special. Which means I appreciate personal experience related to the courses as well as for example if there is any research done (or a way to get some hands-on experience in the...

...to give a number? https://ocw.mit.edu/courses/physics/8-04-quantum-physics-i-spring-2016/lecture-notes/MIT8_04S16_LecNotes5.pdf On page 6, it says, " Matrix mechanics, was worked out in 1925 by Werner Heisenberg and clarified by Max Born and Pascual Jordan. Note that, if we were to write xˆ...

Quantum Mechanics of Particles and Wave Fields by Arthur March... Does anyone know of the author? I think I found an error in this book. :(

Homework Statement Find the wave packet Ψ(x, t) if φ(k) = A for k0 − ∆k ≤ k ≤ k0 + ∆k and φ(k) = 0 for all other k. The system’s dispersion relation is ω = vk, where v is a constant. What is the wave packet’s width? Homework Equations [/B] I solved for Ψ(x, t): $$\Psi(x,t) =...