In physics, a quantum (plural quanta) is the minimum amount of any physical entity (physical property) involved in an interaction. The fundamental notion that a physical property can be "quantized" is referred to as "the hypothesis of quantization". This means that the magnitude of the physical property can take on only discrete values consisting of integer multiples of one quantum.
For example, a photon is a single quantum of light (or of any other form of electromagnetic radiation). Similarly, the energy of an electron bound within an atom is quantized and can exist only in certain discrete values. (Atoms and matter in general are stable because electrons can exist only at discrete energy levels within an atom.) Quantization is one of the foundations of the much broader physics of quantum mechanics. Quantization of energy and its influence on how energy and matter interact (quantum electrodynamics) is part of the fundamental framework for understanding and describing nature.
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...
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.
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...
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...
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...
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...
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...
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...
I am a long-retired physics lecturer, with the bulk of my lecturing focused on quantum and relativity. I am still active in research. I have completely lost contact with the challenge of explaining this stuff to students, and was curious to see how these challenges are met on this forum, not...
I know this wavefunction should behave as a symmetric cosine function (possibly as Cos( (k∗x)/(hbar) ?). I also know for a bound state, the wavefunction must decay exponentially outside the well.
Additionally, r = (-β+ik)/(β−ik) .
However, aside from that, I do not know how to get this question...
IIUC, entanglement sometimes plays a role in conserving come quantity like momentum or spin: the quantities measured for two particles must be correlated in order to get a certain total value.
But is this always the case? For example, what, if anything, is conserved in the Hong-Ou-Mandel...
In the 1934 novel by John Taine, Before the Dawn, scientists are able to retrieve images of the past by accessing the light absorbed by stones throughout history. While this is fictional, 1934 was really before the dawn of quantum physics.
In the far future, could we retrieve images from light...