Questions tagged [heisenberg-uncertainty-principle]

This tag is for Heisenberg's quantum mechanical uncertainty principle. DO NOT USE THIS TAG for uncertainty in a non-quantum measurement.

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Momentum Increase Limit in Black Hole Case

During gravitational collapse of larger stars the compression of matter will make the position of fundamental particles more precise. This is bound to increase their momentum. My question is does the ...
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Proving uncertainty principle [duplicate]

I am newly introduced to Uncertainty principle which says that you cannot measure both the position and the momentum of a particle in the same time. The product of uncertainty must be greater than h/...
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Do empty space have momentum since uncertainty principle forbids 0 energy at any point?

I like to know do vacuum space have momentum due to quantum fluctuations?
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Uncertainty as a founding principle of QM? [closed]

Ideally, every new physical theory is derived from its fundamental principles. Hall & Reginatto derived the Schrödinger equation from an uncertainty principle and probabilistic classical mechanics,...
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Energy-Time Uncertainty Relation and Virtual Particles [duplicate]

I've come across a hole in my understanding. Heisenberg's Uncertainty Principle can be expressed in terms of energy and time as $$ \Delta E \, \Delta t \geq \frac{\hbar}{2} $$ where $\Delta E$ is ...
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A question about Dyson's argument of divergence of perturbative QFT

Related question Doubt in Dyson's argument about the divergent nature of the perturbative expansion in QED My question is, suppose $e^2<0$ and the aggregations of the same type of charge, ...
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Setting Maxwell's demon loose on quantum mechancial systems

Does Maxwell's demon (information being entropy) justify Heisenberg's Uncertainty principle? My thought behind this is that extracting any information from a quantum mechanical system and subsequently ...
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At how small does the uncertainty in position have to become to create uncertainty in momentum?

At what range of possible positions (i.e. what diameter opening) is the uncertainty principle invoked (i.e. where more uncertainty is created in the momentum space)? How small of a range of momentums ...
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Unclear explanation: HUP in Griffiths’ 3rd Edition

In chapter 1, part 6 of the 3rd Ed. Of Introduction to Quantum Mechanics, Griffiths’ says “Please understand what uncertainty principle means:Like position measurements, momentum measurements ...
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How can the uncertainty principle lead to a lower energy level in a $H_{2}$ molecule compared to the separate molecules?

I was studying and came across this quote from Giancoli's Physics For Scientists & Engineers with Modern Physics. in Chapter 40. "From the uncertainty principle with $\Delta$x larger, we see that $...
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Is the cut-off energy in the calculation of the electron's self-energy associated with an electron size?

I have got two questions on the self energy/point particle concept of the electron: What do physicists exactly mean when they say the elementary particles (e.g. the electron) are point particles? ...
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Time taken to determine source of a wave

I have a problem to solve. Suppose I have radiation coming at me from different sources, both with different frequencies, what would be the minimum time needed to find out where each source is coming ...
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Uncertainty principle and meaning of particle's position

Suppose we have a particle and a detector. The detector will detect electron position not in a sharp peak but according Heisenberg principle in a peak with a deviation. But what that deviation ...
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The time-energy uncertainty relation on a compact space

This post follows this answer of Ben Crowell. The problem with the time-energy uncertainty relation $$[H,T]=i\hbar$$ is that it implies that the spectrum of the energy operator $H$ cannot be ...
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According to quantum uncertainty, can an object transform into another object even with extremely low probability?

First of all I would like to point out that when it comes to quantum physics, I have very poor knowledge so please excuse me if I misuse some words to describe what I mean. My question is based on ...
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Feynman's path integral and uncertainty principle?

The Feynman's path integral representation gives the quantum amplitude to go from point $x$ to point $y$ as an integral over all paths. How is that idea consistent with the uncertainty principle that ...
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Conservation of Angular Momentum of an Electron

In applying conservation of angular momentum for an electron we use the relation $mvr=\frac {nh}{2 \pi}$ however the angular momentum has terms of velocity and distance from the line of action. ...
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In electron degeneracy pressure, do electron gains mass?

I think there is no room for fidgeting but then they are still subjected to uncertainty principle, my question is when the electrons are sardine-packed to the extreme so that Pauli exclusion principle ...
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Heisenberg uncertainty principle in single slit diffraction

I have a question about the vertical uncertainty (z direction in the diagram below) for an electron in a single slit diffraction experiment. Would it be correct to take the uncertainty to be $3\mu m$...
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Example of Heisenberg Uncertainty Principle (energy & time)

Beside momentum and position I read that Heisenberg Uncertainty can also apply to energy and time so for instance virtual particle (energy) could pop into existence but for a very brief moment (time) ...
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If a state is an energy eigenstate, then it cannot be localized in time

In Weinberg books The quantum field Theory he says that if a state is an energy eigenstate, then it cannot be localized in time. I am not understanding this statement. For example if $\Psi$ is energy ...
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Experimental physics: $\langle\mathbf{P}\rangle\approx\Delta \mathbf{P}$?

In many of my experimental courses solving a problem in atomic or solid state physics comes down to using the Heisenberg Uncertainity relation $$\Delta \mathbf{X} \Delta \mathbf{P}\geq \frac{\hbar}{2}...
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Why does the uncertainty principle imply that empty space is filled with energy?

I read from this website that the uncertainty principle implies that seemingly empty space is filled with energy, called vacuum energy . The relevant equation I can think of is $$\Delta E\Delta t \geq ...
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What happens when uncertainty in position approaches 0 in Heisenberg’s equation?

In class today we were taught about Heisenberg’s equation, $\Delta x\Delta p\ge\frac{h}{4\pi}$. What happens when one of these uncertainties approaches zero? If we can predict the momentum exactly, ...
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Where does $\pi$ come from in the Heisenberg equation?

In class today we were taught about Heisenberg’s equation, $$\Delta x\Delta p\ge\frac{h}{4\pi}. $$ Experience tells me that any time an equation involves pi, circles aren’t far behind. Obviously this ...
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Why does Heisenberg’s Uncertainty Principle not take wavelength into account?

In class today we were taught about Heisenberg’s equation, $\Delta x\Delta p\ge\frac{h}{4\pi}$. Why isn’t De Broglie wavelength a factor here - or is it, but it’s represented behind the deltas ...
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Does quantum measurement uncertainty still apply when conjuate measurements are inferred?

Consider an apparatus which emits a particle at A which then travels through free space to B. I measure some aspect of that particle at A and transmit that information to B in a light beam. Let's say ...
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On understanding the relation between Heisenberg Uncertanity Principle, Indeterminism and classical chaos

I recently read Emperor's New Mind by Roger Penrose. In it he talks at length on the notion of determinism in science. In this context how does the Heisenberg Uncertanity Principle bring about the ...
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Expected values and $(\Delta X)^2$ for a quantum wave packet

I got stuck at one point in this problem. We are given a quantum packet in the form: $$\psi(x,t)=\frac{1}{\sqrt{2\pi}} \int_{-\infty}^{\infty} g(k) e^{-iw(k)t+ikx}dk$$ where $w(k)=\frac{\hbar}{2m} k^...
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Where is the photon getting energy to deviate from its path?

If we make $\triangle$x really small, then in order to not break the Heisenberg uncertainty principle the photons will need to change momentum($\triangle$p), so where is it getting the energy to ...
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Quantum mechanical measurement

Suppose, a particle has non zero probability to be in any between x = 1 and x = 10. Let, we measure its position with a very low energy photon. It will collapse it’s wave function, since it disturbs ...
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Why does $\Delta L_{x}=\Delta L_{z}=\frac{\hbar}{2}$ and $\Delta L_{y}=\frac{\hbar}{\sqrt{2}}$ in this experiment?

Note: NO, this is not at all a homework question. I struggle to understand the solution our professor gave us to a problem, and that's why I am asking here. Also, given the nature of the problem, I ...
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Isn't the uncertainty principle a circular argument? [closed]

The uncertainty principle says that uncertainty must be greater than or equal to some value. That's the same as saying if uncertainty exists, it exists. $$\Delta x\Delta p\geq\frac{\hbar}{2}$$ If ...
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Heisenberg vs. Bandwidth Principle

Is it true that the Heisenberg Uncertainty Principle is "obvious" because of the Bandwidth Theorem (Fourier Transforms)?
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Why do we need short wavelength to measure the position of a particle accurately?

I am reading "A brief history of time" by Stephen Hawking. It is explaining the uncertainty principle: ... However, one will not be able to determine the position of the particle more accurately ...
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Derivation of mass-lifetime relation in particle physics

How is the inverse relation between the lifetime and mass of a virtual particle derived? For example, it is said that the strong force is short range because its force carrier is massive, and hence ...
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Theory that we cannot observe everything

If I remember physics class correctly, and if not feel free to correct me, there is a theory that shows that we can not observe everything. I think the example given was energy and space. So either we ...
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What is The Heisenberg Uncertainty Principle Making Statements About?

Non-physicist here, trying to understand details about Heisenberg's uncertainty principle: Watching the The more general uncertainty principle, beyond quantum about the uncertainty principle I came ...
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Time Dependence of Momentum Uncertainty for a Free Particle

Question: Show that in a free-particle wave packet the momentum uncertainty $∆p$ does not change in time. I am not sure how to solve for the time derivative of the momentum uncertainty $ ∆p $. I am ...
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How will the uncertainty principle broaden emission spectrums?

I have been told in a lecture that the broadening of peaks detected from photon emission in a hydrogen lamp is due to the uncertainty principle, but can’t work out how it does or find any equation ...
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Query about Heisenberg uncertainty principle

acoording to heisenbergy uncertainty principle if the electrons change the radius of their orbit, then it is like making transition even though the change in radius is small and they should emit ...
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Uncertainty about the ensemble average?

Does an uncertainty in momentum of $\Delta p$ mean that the actual momentum is in the range $\langle p \rangle - \Delta p\space <p< \langle p\rangle+\Delta p\space$ ? Or does it mean that the ...
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Does uncertainty principle imply that the past history of universe is also undetermined?

I read the page here: Is the Uncertainty Principle valid for information about the past?, but I am still somewhat confused. If you measure the momentum/position (with uncertainty) of a particle, what ...
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Can one find the uncertainty of a particle from Schrödinger's wave equation? [closed]

Right now I am studying quantum mechanics and I'm having trouble understanding what exactly $\Psi$ is in Schrodinger's equation $\Psi(x) = A\sin(kx) + B\cos(kx)$. After doing some googling I learned ...
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What does “An experiment performed with certainty has results with uncertainty.” mean? [closed]

A physics book says: An experiment performed with certainty has results with uncertainty. What does this mean?
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Heisenberg uncertainty principle on bosons at absolute zero [duplicate]

Bosons obey Heisenberg's uncertainty principle but not Pauli's exclusion principle. In Bose-Einstein Condensation quantum effects are much more important and here we get a large number of particles ...
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Why the ground state energy of bosons are 0 at T=0K ? Does it violate Heisenberg's Uncertainity Principle at 0K?

Bosons obey Heisenberg's Uncertainity Principle but do not Pauli's Exclusion Principle. That's why in Bose Condensation we get a large amount of particles in a single state i.e. ground state at T=0K. ...
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Does the Copenhagen interpretation (+ “quasi-classical apparatus”) allow one to bypass a derivation's objection? [closed]

Background I asked this question, where I'm thinking about this joshphysics's answer: And the gist of what I get is (from the answers and the chatroom) within interpretations of quantum mechanics ...
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What is uncertainty in position of electron when it is revolving around the nucleus?

Consider an electron revolving around the nucleus in a circle of radius $r$. We need to apply Heisenberg's uncertainty principle on it. What exactly do we take $\Delta x $ to be? One way to think ...
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Validity of the derivation of time-energy uncertainty principle?

Background The top voted answer to this question seems to make some assumptions I'm uncertain about (to say the least): What is $\Delta t$ in the time-energy uncertainty principle? Assumptions The ...