This tag is for Heisenberg quantum mechanical uncertainty principle.

learn more… | top users | synonyms

4
votes
4answers
450 views

Is uncertainty principle a technical difficulty in measurement?

I have searched for an answer to this question on physics SE but I have not seen a question in which it is addressed properly. Please let me know if there is an answer already. My question briefly ...
0
votes
5answers
257 views

Why does the universe follow the uncertainty principle?

I have been thinking about this question for quiet a long time but, couldn't make up an answer myself. Usually when someone asks about why a system is the way it is we answer it by saying that it is ...
0
votes
3answers
435 views

How to derive the uncertainty relation for a system of arbitrary potential?

I've been trying to understand the derivation of the uncertainty principle for the harmonic oscillator as described here (see pages 100-101). What I don't understand is how the potential for the ...
1
vote
2answers
112 views

Photons vs Uncertainty Principle

The uncertainty principle states: $\Delta_x\Delta_p>ħ/4$ We know the photon has a 0 rest mass but we are say that it's momentum is always the same $e=pc$ And more we are certain about the ...
-1
votes
1answer
128 views

Uncertainty principle in atomic clocks?

How does the uncertainty principle limit the accuracy of atomic clocks. I know line width and measurement time are important but not exactly why?
0
votes
1answer
139 views

Help with the Heisenberg relation in Gaussian wave

In short laserpulses there is a minimal product of the frequency width and the pulselength for Gaussian pulses $\tau \cdot \Delta\omega \geq4\ln2$ this is the fourier boundary. So I know it origins ...
7
votes
3answers
492 views

Is the uncertainty principle valid?

The uncertainty principle says that the product of the uncertainties in position and momentum can be no smaller than a simple fraction of Planck's constant $h$. Several articles lately suggest this ...
1
vote
1answer
260 views

Heisenberg uncertainty principle - question [closed]

A beam of particles each having mass $m$ and velocity $v$ in the incident on a circular hole of radius $b$ located on a screen. If another screen is placed at a distance $D$ from the hole, ...
-1
votes
1answer
82 views

Electron in strong magnetic field [closed]

What if we apply a very strong magnetic field to an electron so that it's position be a constant. Then if it's position is constant, it's momentum will also be a constant. But it is in violation of ...
2
votes
2answers
96 views

Quantum uncertainty in cell functions

In class today (philosophy of the mind) we discussed the ideas of Richard Lewontin. He stated that in determining the phenotype of a gene we must take into account the environment but also quantum ...
1
vote
1answer
104 views

Weird Behaviour of the act of measurement to a quantum system

I and my friend were disputing about some weird behaviour of the act of measuring some observables quantities e.g. Energy, position. But I still don't think what he said is strictly true. He said" ...
0
votes
1answer
65 views

In what range the acceleration value of quantum particle lies?

According to Heisenberg's uncertainity principle, the position and velocity of an quantum particle cannot be determined simultaneously. Is it possible to determine position and acceleration ...
2
votes
1answer
485 views

Why is classical physics not valid for a harmonic oscillator in its lowest energy state? [closed]

I am reading Born's interpretation of wave function in quantum physics by Eisberg & Resnick and I am not able to understand this description about comparison between the classical and quantum ...
0
votes
1answer
1k views

Uncertainty in momentum of an excited electron trapped in a box (1D)?

An electron is trapped in a one-dimensional well of width $0.132\,$nm. The electron is in the ninth excited state ($n=10$) state. What is the uncertainty in its momentum? The problem gives a hint to ...
0
votes
0answers
27 views

Question regarding waves squeezed

in one MOOC I am taking, the professor had a slide stating "when squeezed into a narrow space wave is amplified". I am not sure I understand what he meant by that, and I am trying to think into terms ...
0
votes
2answers
201 views

More Heisenberg Uncertainty Principle (HUP) Clarification

If you look at the commutation relation of the position and momentum operators (in 1D position space), you get: $$[\hat{x}, \hat{p}_x] = [x,-i \hbar \frac{\partial}{\partial x}] = i \hbar$$ All this ...
3
votes
1answer
322 views

Why doesn't gravity act as a measurement?

I think this must be a very basic question but I couldn't find the answers anywhere. I was starting reading about Quantum Mechanics and these questions came in mind: As I understand the quantum ...
1
vote
2answers
107 views

Why the wave-particle duality cannot be explained as a traveling-standing wave duality?

This would explain why speed and position cannot be measured at the same time, since either the wave would be traveling (speed) or enclosed and standing (position). The act of enclosing it (to be ...
0
votes
4answers
231 views

Heisenberg's uncertainty principle for electrons and atoms

Here is a video of Michio Kaku discussing Moore's Law and the quantum mechanical limits thereof. Around the 1:30 mark he's talking about how the chips today have a layer of 20 atoms across (I'm ...
5
votes
3answers
362 views

Uncertainty principle and the energy-momentum 4-vector

In each of the uncertainty relations $$\Delta p_x \Delta x \geq \hbar/2$$ $$\Delta p_y \Delta y \geq \hbar/2$$$$\Delta p_z \Delta z \geq \hbar/2$$$$\Delta E \Delta t \geq \hbar/2$$ the second term on ...
1
vote
1answer
231 views

How does the uncertainty principle make a photon beam spread out?

I'm reading about uncertainty principle, and something has been bothering me for quite a while. There is the formula: $$\sigma_x \sigma_p \ge \frac{\hbar}{2}$$ I know what this means: the more you ...
2
votes
1answer
93 views

Does Heisenberg uncertainty apply within each quantum configuration, or in the amplitude distribution over them?

I'm still absorbing some basic ideas about quantum physics and now I think I have to reconsider the Uncertainty Principle. Here is what I understand, in summary: a "configuration" specifies the ...
2
votes
2answers
150 views

Uncertainty principle and multiple observers

My understanding is that an observer can measure the precise location of a particle so long as the corresponding uncertainty in momentum measurement is not an issue and vice-versa. Say there is ...
2
votes
0answers
149 views

Uncertainty Principle and Bohmian mechanics

The Uncertainty Principle is a relationship between measurements of pairs of attributes, position and momentum, as well as energy and time. Perfect precision of one attribute's measurement leads to a ...
2
votes
2answers
231 views

Question on the uncertainty principle

The problem statement: Measurement detects a position of a proton with accuracy of $\pm10pm$. How much is the position uncertainty $1s$ later? Assume the speed of a proton $v\ll c$. What i ...
7
votes
3answers
650 views

Connection between $\Delta x \Delta p \geq \frac{\hbar}{2}$ and $\Delta E \Delta t \geq \frac{\hbar}{2}$

Is there a way to derive second equation from the first one? I mean is there a connection between those two uncertainty relations? \begin{align} \Delta x \Delta p &\geq \frac{\hbar}{2}\\ \Delta ...
1
vote
0answers
57 views

commutators in an uncertainty relationship derived from a partition function?

The maximum information principle for the discrete case gives rise to a partition function (>>> see details here) $$Z(\lambda_1,\ldots, \lambda_m) = \sum_{i=1}^n \exp\left[\lambda_1 f_1(x_i) + \cdots ...
2
votes
0answers
78 views

commutator to entropy in an uncertainty relationship?

Question: Does there exist a commutator to entropy in an uncertainty relationship? Similar Energy and time for instance.
8
votes
3answers
1k views

Eigenstate of position+momentum?

I'm studying Quantum Mechanics on my own, so I'm bound to have alot of wrong ideas - please be forgiving! Recently, I was thinking about the quantum mechanical assertion (postulate?) that states with ...
8
votes
5answers
687 views

Why doesn't a quantum particle in an attractive 1D potential accumulate at the center?

I have two questions regarding (possibly counter intuitive results) Schrodinger equation and its application to two (strictly hypothetical) scenarios. Consider the 1D potential $V(x) = - ...
8
votes
2answers
4k views

Heisenberg Uncertainty Principle: Which formula is correct?

Some websites and textbooks refer to $\Delta x \Delta p \geq \frac{\hbar}{2}$ as the correct formula for the uncertainty principle whereas other sources use the formula $\Delta x \Delta p \geq \hbar$ ...
1
vote
1answer
126 views

Formulation of the uncertainty principle for a system?

There is a biological system that I can indeed describe by a simple quantum Hamiltonian $H$ having eigenstates $|q\rangle$ labelled by the numbers $q$, and having energies proportional to $f(q)$ - ...
0
votes
2answers
98 views

Reconciliation of a particle's rest frame and the uncertainty principle

When calculating in a rest frame, doesn't one assume both, definite velocity (zero) and position (origin)? Why is Heisenberg okay with that? Edit: E.g. For a decay we can do calculations in which we ...
4
votes
2answers
274 views

A quantum particle which is almost at rest but whose position is random!

Assume a particle is given by a quantum state which is constructed in such a way that it is equally probable to find it anywhere in an fixed interval $(0,L)$ but has arbitrarily low velocity. The ...
4
votes
1answer
616 views

What physical significance has the Heisenberg Group?

I read that the canonical commutation relation between momentum and position can be seen as the Lie Algebra of the Heisenberg group. While I get why the commutation relations of momentum and momentum, ...
1
vote
2answers
152 views

Uncertainty in path integral formulation

In Feynman's path integral formulation, in order to calculate the probability amplitude, we sum up all the possible trajectories of the particle between the points $A$ and $B$. Since we know ...
-2
votes
1answer
209 views

Is there a heuristic explanation for the derivation of Heisenbergs Uncertainty Principle from String Theory?

Heisenberg famously derived his uncertainty principle by considering the disturbance that a measurement would have on a small enough system. Of course in the mathematical formalism of Quantum ...
1
vote
1answer
335 views

Conservation of Energy and Quantum Fluctuations

Regarding conservation of mass-energy Wikipedia says: "this is an exact law, or more precisely, has never been shown to be violated." However, regarding quantum fluctuations, Wikipedia says here: ...
1
vote
2answers
180 views

How does the Cern LHC collide particles head on if uncertainty principle limits the precision

I have been wondering why doesn't the uncertainty principle prevent the LHC experiment as if one want to collide two particles together one must accelerate a particle to certain speed and aim it at ...
4
votes
1answer
375 views

Is the number-phase uncertainty relation classical?

For a harmonic oscillator in one dimension, there is an uncertainty relation between the number of quanta $n$ and the phase of the oscillation $\phi$. There are all kinds of technical complications ...
1
vote
2answers
98 views

Quantum Mechanics, Uncertainty Principle— help understanding notes

There is a section of my notes which I do not understand, hopefully someone here will be able to explain this to me. The notes read (after introducing the uncertainty operator): If the state ...
5
votes
3answers
411 views

How can particles travel in a straight line?

A particle can be set off in a certain direction by giving them momentum. Momentum is a vector, so the particle heads off in a specific direction. But the wave function of the particle allows it to ...
0
votes
1answer
85 views

The Univere's mass-energy and uncertainty [duplicate]

A virtual creation with total mass-energy = $E$ is allowed as long as that virtual creation doesn’t last longer than $E/h$. Can the uncertainty principle also be used to estimate the mass-energy in ...
2
votes
1answer
118 views

Uncertainty Principle on System of particles

I am new to Quantum Mechanics. I read the uncertainty principle - it says there are pairs of physical quantities which can't both be determined with certainty for a particle. My question is does the ...
0
votes
1answer
220 views

Why is the Heisenberg Uncertainty Principle not obvious give the conservation of mass- energy?

A photons energy is given by $E=h *f$ and momentum $p=E/c$ (spin?) but the photon has no (rest) mass! Therefore it is the ultimate probing tool for looking at any mass position and velocity because ...
1
vote
0answers
28 views

Does quantum mechanics depend solely on electromagnetic waves? [duplicate]

I am beginning to learn quantum mechanics. Since determining the position of an object involves probing by electromagnetic waves and since i have read a simple derivation of Heisenberg's uncertainty ...
1
vote
1answer
319 views

Uncertainty-principle and the Maxwell formalism of electromagnetic waves

An electromagnetic wave (like a propagating photon) is known to carry it's electric and magnetic field-vectors perpendicular and each depending on the differential change of the other thus "creating" ...
4
votes
1answer
851 views

Phase space in quantum mechanics and Heisenberg uncertainty principle

In my book about quantum mechanics they give a derivation that for one particle an area of $h$ in $2D$ phase space contains exactly one quantum mechanical state. In my book about statistical physics ...
4
votes
3answers
228 views

Reaching the speed of light via quantum mechanical uncertainty?

Suppose you accelerate a body to very near the speed of light $c$ where $v = c - \epsilon$. Although this would take an enormous energy, is it possible the last arbitrarily small velocity needed -- ...
3
votes
1answer
109 views

Connection between a simple matter wave and Heisenberg's uncertainty relation

When looking at the wave function of a particle, I usually prefer to write $$ \Psi(x,t) = A \exp(i(kx - \omega t)) $$ since it reminds me of classical waves for which I have an intuition ($k$ ...