Quantum Definition and 999 Threads

I was / am trying to derive the energy shift resulting from the normal Zeeman-Effect by coupling the Hamiltonian to the external field ##\vec{A}##, that carries the information about the field ##\vec{B}## via ##\vec{B} = \nabla \times \vec{A}##. Let ##q = -e## be the charge of the electron and...

how do i write the z spin state using the spin state on x or on y?

Covering: - New Ramsey number bounds - Aperiodic tiling discovery of an Einstein tile - Three Arithmetic Progressions

It is cited here, and here like so: And here [edit] - and here The full quote from the paper I cited: I don't see how this paper is not a paper about the no boundary proposal.

and how is it known that the two photons are entangled in the first place? I mean before measuring how do you know that you have the correct two photons?

I have this following Gaussian wavefunction. I found the constant C to be $$\sqrt{\sqrt{\frac{2 \alpha}{\pi}}}$$. Now they're asking me to find the normalized impuls wavefunction $$\phi(p)$$. I tried to use the fourier transform relation $$\phi (p) = \int e^{-\frac{i ( p x)}{\hbar}} \Psi...

I cannot find a clear answer on the following beginner’s question on some QM fundamentals: Suppose we have two particles, A and B. Let’s say we generated these as (or otherwise entangled them as) an entangled pair with opposite/orthogonal states. Perhaps horizontally and vertically polarized...

Starting from this link my understanding of Bell inequality proof goes as follows: Suppose we have a model of local pre-determinate hidden variables for QM. This amounts to say QM objects are in pre-determinate given states even if we do not measure it. Locality just means that spacelike...

Just a guy with huge Curiosity Quotient, in subjects ranging from Astronomy to Quantum Physics, to Geology and Ancient Mythology, Chemistry to Science Fiction & Fantasy, and finally Science in General.

Hi all, I was wondering if there was a reference/textbook where the degenerate perturbation calculation for the Transverse Ising model was treated fully. I want to better understand how in the weak magnetic field limit, the ground state degeneracy only lifts at N'th order in perturbation theory...

Neil deGrasse Tyson has been a great "goto" and respected physicist for me to follow online. I've read Einstein's biography and have been fascinated with the world as theorized by some of the greatest minds and proofs. Recently, I've come across a name I've never known. Admittedly, this is a...

An electron requires an "exact" wavelength photon to transition from one level of an atom to another. Yet the wavelength of a photon has a a continuous probability distribution, implying that the point probability of achieving an exact wavelength is zero. One can only talk meaningfully about...

Hello, I understand the photoelectric effect, its importance, and the basic theory. But I have a few questions: 1) One photon "can" free only a single electron, correct? However, it is not certain that if we shine exactly 10 photons (frequency? ##f_0##), that 10 photoelectrons will be free...

By the results of the photoelectric effect experiment, the photoelectric effect does not occur at all if the frequency of the light source is below a certain value. We have the Work Function for a metal. Why when the energy of the photons of the light source is W/2, we don't have the...

TL;DR Summary: I have spent all day on these 2 problems but i cannot solve them. Can somebody give me any clue on the solution?

Hey, I was just contemplating career opportunities after my Undergrad. I am slightly interested in theoretical physics but I can't imagine doing it the rest of my life. My main interests are nano-photonics and quantum technologies and I am planning to do research in these fields. I am not...

Hi, I am new here. I expect that most people will find my approach to science interesting because I do not do standard physics. I do SUSY inversion and the He-BEC DE DM model corresponding to a revision of quark charge calculations giving rise to Baryonic symmetry.

I'd like to hear your professional opinion on and experience with using Quantum Field Theory for the Gifted Amateur by Tom Lancaster and Stephen J. Blundell as a self-study textbook. Thank you.

How and/or why does the existence of the quantum of action (Planck's constant) cause indeterminism?

I'm reading the article on the Many Worlds Interpretation in the Stanford Encyclopedia of Philosophy. I'm keeping up well, but this excerpt uses things I'm very unfamiliar with: I guess some characters weren't recognized. It's Section 3.6 here. I'm somewhat familiar with Wigner's Friend, but...

Between the walls of a finite well, the solution to the time independent Schrodinger equation is a combination of sines and cosines. Outside the walls where E - Uo is positive, the solutions are exponential functions. Why?

This is the given circuit: I think to add another Cnot on the right with a1 as control and a0 as target, to set initial states of a0 an a1 both |0⟩, and to measure the a0. If a0=|0⟩ then b0=b1, and vice versa. Is it correct?

Hi, my name is Kennard Callender. I am an independent scientist from Panama working on the foundations of quantum mechanics and relativity. I look forward to meeting people who desire to understand nature at its most fundamental level and who can help me polish my work.

Join the Quantum hip, we are here 🤠

Hi guys I have a question for you. Virtual particles can appear anywhere and when they have enough energy they turn into real. And if it happens long enough in a vacuum, will it remain a vacuum? If not, then is matter infinite?

The title is from a great book by Eric Kraft, who plays around with one's physical-being in elemental terms in an excellent novel. He is very funny. To get down to my question: Do electrons or photons on anything move faster than the speed of light?

I just learned about the Stern-Gerlach experiment and have some questions: 1: clearly there's no objective "up" or "down"--the directions are measured relative to the magnetic field, correct? And well always find just 2 spots of equal and opposite distance on the detector, implying the magnetic...

How can we link the band gap to lattice spacing? For (a), if we purely do dimension analysis, then I would guess $$a=\frac{\hbar c}{E_g}$$. But what's the reason behind this answer, and will the true lattice spacing be larger or smaller? For (b), I guess $$\lambda=\frac{\hbar c}{E_g}$$ due to...

If I have a brittle piece of rock and hit it with a hammer, can a round ball split of in some universe, verses in our universe a piece with rugged ends always form? If so, why do we always, in our universe seem to get "expected" results? Why dont strange things happen here sometimes? Why is our...

Let's assume that there is a closed box, with mass M. There are some random quantum processes inside it, say radioactive decay. Let's assume that we can manipulate the decay from the outside somehow, thus 'putting information' into the box. Can that affect its mass?

Can you swap out the RNG that is the wave function collapse with a suitable deterministic chaotic process that matches the wave function (squared)? I can picture a multi leg pendulum swinging around drawing out the wave function. The point where you measure is the point the pendulum was at. Is...

Hello Dear Physicists, I know this question probably discussed many times before. But I need a clear answer about this setup in case there is no beam splitter. What is gonna happen in this situation? My classical intuitions say I will see a correlated interference pattern on both screens(or...

ATTEMPT AT SOLUTION: I understand if looking for positive this will be +hwo/2 (hbar) for Sz so must find |a|^2. and if looking for negative this will be -hwo/2 (hbar) so must find |b|^2. If asked to find say Sx and original question in Sz, we must find new eigenstates associated with this state...

Are the K-point mesh and monkhorst pack same. I was reading research papers using VASP and in some papers as the number of cells increases the Monkhorst Pack increases but in others the K-Point mesh decreases.

This might seem like a rather peculiar observation and question. However, a rather strange physical anomaly was noted about a decade ago. While gazing thorough a living-room window. A flying-insect was seen with a portion of its torso fixed within the pane of glass. It seemed, as if, it...

Let's try to get into the looking glass of quantum mechanics together.

hello! my name is Mohammad Sameer from India. Pursuing five years integrated masters in physics, will be starting my second year in couple of days. Interested in quantum theory of classical entities and want to explore more in the domain.

In this video Dirac talks about the Fine Structure Constant 1/137. Can we now explain why this is?

If you have, say, a two-mirror interferometer that is producing an interference pattern, how many photons are interfering? Two, or just one?

Non-perturbative methods are critical in parts of quantum field theory, such as QCD, and have at least some applications in quantum electrodynamics. You can also have mathematical problems that don't have perturbative solutions. But, it isn't clear to me if classical physics can ever have...

Hi, is it possible to ionise a solid, so that it has no electrons left? Josiah

A perovskite, normally used for solar energy collection, may find an application in quantum computing. The article is article is published in Nature (with a paywall), It is also covered in SciTech Daily. This is not the first material that has been able to generate photons so precisely...

The recent rescue operation of a sub in the ocean made me wonder how difficult it is to communicate with underwater vessels. Is it that all parts of the EM spectrum gets absorbed at extreme depths that things like GPS is not possible. I wondered what wavelengths of the spectrum were absorbed...

Hello everyone. First, sorry for my english. Second, I have got question where vibration mode of H2+ molecule (I think it is the most simple molecule for this topic explanation) comes from. If I should get basics before asking this tell me :). By my count the most important factor behind "being"...

Hello everyone. My name is Przemek. I am from Poland and I am intrested in quantum physics and intermolecular forces.

Hi all, This should be a simple question but it has been bothering me for a bit: Consider 2 Hamiltonian terms ##H_{1},H_{2}## that satisfy ##[H_{1},H_{2}] = 0##. Suppose we are working in the Heisenberg picture and we time evolve some operator ##A## according to ##A(t) =...

So the whole idea with quantum entangled computing, is that particles in superposition can compute more than one thing at the same time, right? But how does a system know which computed result is which? Maybe like a hashtag that separates one from another? But wouldn't that get jumbled, and...

In a collapsing star, the expression for what goes on is "degeneracy pressure". The way it's put is that the Pauli Exclusion Principle just doesn't allow more than one fermion to exist in one place (state). So the star reaches a certain volume and, on the way, produces a lot of Energy. I can...

Say you have a simplified 1d Gaussian wave function describing location of a particle. Many worlds says that every outcome is a separate branch. Copenhagen says you will get one of those branches. So how many distinct positions, imaginary or real, can you generate from a fixed segment of a...

Assume spin 1/2 particle So the spin operator gives +/- hbar/2 eg. S |n+> = +/- hbar/2 |n+> But S= s(s+1) hbar = sqrt(3)/2 hbar So I'm off by a factor of sqrt(3). I suspect I am missing something fundamental about my understanding of spin. My apologies and thanks in advance.