Quantum Definition and 998 Threads

While reading something recently that mentioned the Casimir Effect, it occurred to me that the plates used in an experiment to measure the force between them would be close enough to allow quantum tunnelling if the plates were transparent, which led me to wonder whether (and how much) the force...

Cost me a fortune when the dollar was so high in the eighties :rolleyes: ##\ ##

Hello everyone, I'm trying to recall the title and author of a quantum mechanics textbook I read many years ago, likely a couple of decades or more. My local library had what I thought was a very good quantum mechanics book, which I worked through during the summer holidays after completing my...

Roderich Tumulka (a long-time Bohmian) demonstrates in his newest preprint, R. Tumulka, A Vision for a Bohm-Style Theory of Quantum Electrodynamics, arXiv:2409.07784. that for the interpretation QED, the Bohmian interpretation has nothing to offer (apart from speculation called vision), and...

TL;DR Summary: Funny (but very well informed) video about QM. Hope this is not considered off-topic, but anyone so inclined and with 4+ mins to spare might enjoy this (intentionally funny) QM video by eigenchris:

I am happy to announce my book A. Neumaier and D. Westra, Algebraic Quantum Physics, Vol. 1: Quantum mechanics via Lie algebras, de Gruyter, Berlin 2024. It features a mathematically rigorous but still physically lucid account of quantum mechanics from the point of view of symmetries...

Assuming the situation where there is an infinite inflation stream, from which bubble universes are appearing in locally slowed regions. There could be many many such bubble universes and so very rare occurrences in some bubbles can sometimes happen. Also assumed, as is often postulated, that...

Hello to everyone. I have some doubts about one problem of quantum mechanics. My attempt. I need to calculate the coefficient ##W_{ij}=<\psi_i | H' |\psi_j>## where ##H' = -eE(t)z## is a perturbation term in the hamiltonian and ##|\psi_i> = |\psi_{nlm}>##. We have four states and sixteen...

So one of the major topics in physics is trying to reconcile quantum mechanics and general relativity. And the classical expression of electromagnetism is Maxwell's equations, and its linked to quantum models of electromagnetism. And then there's also a gravitational analogue of Maxwell's...

How does QFT treat the Young’s DSE? Is there a wave function (wave packet) attached (and created at the moment of launching of the photon) or the modes of the EM quantum field are pre-existing due to experimental configuration (including the screen) and do they play the role the wave function is...

How did you find PF?: Wandering on the internet looking for answers about Bell's theorem I teach adult education at 2 universities near Denver and I'm writing a book for non-scientists interested in quantum mechanics and its foundations. The challenge is to present the concepts digestibly...

https://physics.stackexchange.com/questions/824561/two-element-theory

For this, The solution is I have doubt where they got the reflection probability formula from. Someone may know how to find it. I think that ##R + T = 1##. But I'm not sure where the transmission probability formula comes from either. Kind wishes

For this problem, The solution is, I have a doubt about Step number 3 about boundary conditions. Someone maybe be able to solve that doubt? Kind wishes

So basically assume both the star and earth have high-tech machines and a mapping of natural changes in orbit such that the detectors will always be the same settings on star and earth, and the ship in between earth and star will move in such a way that the alignment will be exactly halfway in...

Suppose that Bob and Alice decides to do a quantum experiment, more precisely, The Shroedinger Cat Experiment. Alice goes to the Andromeda Galaxy, and wait for Bob’s results. According with the MWI, the wave function never collapses, suppose that in one world Bob found the cat alive, in the...

in an interview Michio Kaku was asked about Loop Quantum gravity and he replied that it is only a theory of pure gravity, but that the universe also contains particles, the particles of the standard model, and only superstring theory unifies both quantum gravity and the standard model. the...

Recently I’ve been learning more about quantum physics, and Physics Forums has had a lot of good answers to questions I had. I’m looking forward to learning even more, and asking questions that I’ve beenconfused about.

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hi, I'm solving this statement, We split into parts Can some expert in Quantum say that my working is professional? Kind wishes to you

Hi, I try and solve this problem I have solved the problem in different parts But me not sure how to plot the graph. Maybe someone knows? Merci

How did you find PF?: Good Need documents to help me understand quantum computing!

A quantum dot is placed in a line between two optic fibers The dot can emit a photon in every direction which is unknown. If the fibers are combined at a beamsplitter would there be interference if the photon is not observed outside the fibers? Do you know if somebody made such experiment...

I have come across the following paper (arxiv preprint link, it looks like it is published in Phys Rev D) that claims to have found a consistent quantum field theory of tachyons, overcoming three issues which have been said in previous literature to make such a theory impossible...

I am currently a research scholar specializing in open quantum systems.

Hello, I am interested in the following model: $$ H = \sum_{<i,j>} -t (c_i c_j^{\dagger} + \text{H.C.}) + U (n_i n_j) + \sum_{<<i,j>>} -t' (c_i c_j^{\dagger} + \text{H.C.}) + U' (n_i n_j) $$ where \( <i,j> \) indicates nearest neighbors, and \( <<i,j>> \) indicates next-nearest neighbors...

My first "active" encounter with the transactional interpretation happened when I tried to react to Ruth Kastner's criticism of consistent histories. My next encounter happened when I was fighting with reciprocity occuring for crystal effects in electron scattering, and hoped for help from time...

I am a second-year combined honour in physics and math with prerequisites for 4th-year math courses. I am hoping for a direct entry (if possible) into a top US PhD physics program in quantum with a current unofficial cGPA of 3.9/4 (88%). Since I am in Canada, we only have percentage grades that...

https://www.guardianmag.us/2023/02/scientists-levitate-glass-nanosphere.html "the nanosphere was suspended in its lowest quantum mechanical state, one of extremely limited motion where quantum behavior can start to happen." To my reading, the glass bead was cooled down and then suspended with...

The lowest two energy level corrections (l=0, s_{z}=-1/2 and l=0, s_{z}=1/2) are easy to work out since the eigenvalues are not degenerate and the unperturbed energy levels also happen to be eigenstates of H'. However I have three degenerate energy levels for the third eigenvalue of the form...

Hi guys, I have a problem with point 2 of this exercise: The electron of a hydrogen atom is initially found in the state: having considered the quantum numbers n,l,m and epsilon related to the operators H, L^2, Lz and Sz. I am asked: determine the possible outcomes of a measurement of J^2...

Next, we assume a solution in this form: Which simplifies (according to my notes) to this: In the middle equation, we have factorised out the F(t). My question is why is it wavefunction(x,t) rather than wavefunction(x). I first thought it was a mistake in the notes, but it uses the same...

In reading Weinberg volume 1 I learned gravity is not renormalizable by Dyson power counting. This means that it has an infinite number of free parameters, and such theories lose their predictive power at energies of the common mass scale. This being said, T Hooft and Veltman showed miraculously...

Many more questions....please enlighten me on this topic. thank you!

I was tryingt to find away to build a setup for conducting the quantum erase experiment, demonstrating the observer effect. It seemed impossible without expensive equipment for sending single photont and detecting single photons, then however I bumbed into this guide from scientific american...

Well, I am not making any exciting claims or anything, just asking a question that I cannot stop asking myself. WE all know the Quantum theory on spontaneous generation of particles in a vacuum etc and many have asked is this linked to dark energy somehow. I like to try Einstein type Thought...

Hi, when normalising the wavefunction I get two answers. Is this correct? My notes only has 1/sqrt(L) = A.

TL;DR Summary: Why is HgCl2 more covalent than CaCl2 via shielding? Hg^2+ in HgCl_2 has more shells of p-orbitals and s-orbitals than Ca^2+ in CaCl2 - Do those extra p and s shells of Hg^2 in HgCl2 shield the two chlorines in HgCl2 from the effect of Hg^2+'s nucleus attraction, or leave the...

If we have a pair of super-asymmetrical entwined particles, and move them a light year away so that they retain their quantum entanglement, and we set a clockwise spin as 0 and a counter-clockwise spin as 1. Would it be possible to transmit binary data faster than the speed of light? If we hold...

Sakurai's Modern Quantum Mechanics is 1/2 of a very good graduate textbook. Unfortunately Sakurai passed away midway through writing it, and it is very obvious exactly where it swapped from their writing to just using their notes. The back half of the book, while by no means bad, is notably less...

Student of master of physics.

A.E. Allahverdyan, R. Balian, and T.M. Nieuwenhuizen, Teaching ideal quantum measurement, from dynamics to interpretation, Comptes Rendus Physique 25 (2024), 251--287. https://www.researchgate.net/publication/380862732

If gravity is not a force, but rather curvature of spacetime, are gravitons necessary to couple with gravitational field?

I suppose, anybody here knows about the Elitzur–Vaidman bomb tester and the counterfactual definiteness: https://en.wikipedia.org/wiki/Elitzur–Vaidman_bomb_tester https://en.wikipedia.org/wiki/Counterfactual_definiteness I have a question: can this experiment be performed at the level of...

Color charge is not scalar. Still, do their components have dimensions (in metrological terms)?

Firstly I have found the eigenstates for both the original well and the new well as the following $$\psi_{n,\frac{L}{2}} = \begin{cases} \sqrt{\frac{2}{L}} \cos{\frac{n \pi x}{L}} \; \; \; \; \; n \text{ odd} \\ \sqrt{\frac{2}{L}} \sin{\frac{n \pi x}{L}} \; \; \; \; \; n \text{ even}...

Am reading a book (Ballentine, "Quantum Mechanics: A modern development) which I have found very helpful. Am now puzzled by section 3.4, where the position operator satisfies Q|x> = x |x> (I have simplified from 3 dims to 1 dim). Here, x is any real number. There are, thus, uncountably many...

A physicist (I'm not a physicist by profession, as you'll have gathered) told me, without being more specific, that interference is not an 'interaction' in the strict sense of the word, in other words in the physical sense of the term. I can only guess at what is meant by this (but perhaps...

Every once in a while I use my ancient trick of searching something in google with keywords, and found the above article. I don't think there's a free copy of it, because it's from 1989. I guess I need to read the pink book on foundations of Q-Groups by Majid. You know who also has written a...

Hi everyone I'm Justina. I'm excited in joining physics forums and I'm high school student who is interested in Quantum mechanics a lot .I used to spend lot of time on knowing Quantum mechanics and i learnt few little things. And this is my first time, joining an online community hope I will...