This tag is for Heisenberg quantum mechanical uncertainty principle.

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Uncertainty in position and kinetic energy

How do you find the uncertainties for $x$ and $K$? Knowing that the general uncertainties = $$ \sigma_A \sigma_B \geq 1/2\int \psi ^*[\hat A,\hat B] \psi dx\, $$ I figured out the commutator, for ...
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can one measure energy to a finite accuracy?

Can one measure energy to a finite accuracy in bounded amount of time? I don't know much about QM, but someone told me that the energy-time uncertainty principle says that it would take infinite ...
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Stopping an isolated metal ion

If we obtain something like a single isolated hydrogen atom I.e. $H^+$ is it possible by keeping it in a system of charged rings to contain and stop it at the centre of the system? Any positively ...
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Can we describe Quantum Mechanics using filters and matrices? [closed]

Can mathematical filters or ultrafilters be used to predict quantum physics 'events' as accurately as using matrices like Schrodinger did? Is there a way to explain some of the predictive power of ...
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Position and potential Energy

Why are the position and potential energy of a particle able to be measured precisely in Quantum Mechanics? I mean why do they commute with each other?
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Uncertainty principle in Quantum mechanics

The Uncertainty principle says that "△x△p>h/2"; we cannot precisely obtain both position $x$ and momentum $p$ simultaneously. Is this because the uncertainty is the natural characteristic or it is ...
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Relating Schrödinger's Wave Equation and Heisenberg Uncertainty Principle

A homework question that I don't conceptually understand: A quantum particle of mass M is trapped inside an infinite, one-dimensional square well of width $L$. If we were to solve Schrodinger's wave ...
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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, ...
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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 $f(q)$ - ...
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Uncertainty and Thermodynamics

Dilemma The uncertainty principle of energy and the 2nd law of thermodynamics don't add up : the uncertainty principle of energy says that $\Delta \tau \cdot \Delta E \ge \frac{h}{4\pi} = ...
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Experimental perspective in understanding the Heisenberg Uncertainty Principle

I need to confirm whether or not I understand Heisenberg Uncertainty Principle. So the crucial thing is that you need an "ensemble" of measurements: $$\delta x \delta p \ge \frac{\hbar}{2}.$$ If I ...
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Where does the “borrowed energy” come from in Alpha decay?

I was also thinking about the uncertainty principle in regards with energy & time. The question of something like: Alpha tunneling out of the nucleus is where this can be invoked, but having an ...
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How does position uncertainty change in time?

I have an online homework for my Modern Physics class, that requires me to find the uncertainty in velocity and position of a duck. The question is as below: Suppose a duck lives in a universe in ...
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Non-locality in non-relativistic Quantum Mechanic

I guess the following obvious question is answered by any flavor of relativistic Quantum Mechanics, but I just wanted to check whether I understand correctly: Is it correct that nonrelativistic QM ...
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Uncertainty relation for non-simultaneous observation

Heisenberg's uncertainty relation in the Robertson-Schroedinger formulation is written as, $$\sigma_A^2 \sigma_B^2 \geq |\frac{1}{2} \langle\{\hat A, \hat B\}\rangle -\langle \hat A\rangle\langle ...
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What is the experiment used to actually observe the position of the electron in the H atom?

Prior to observation, the electron can be found anywhere (from inside the nucleus to the ends of the universe), but once its position is determined the answer is precise (albeit its momentum is not ...
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Is uncertainty a physical obstacle? [duplicate]

Heisenberg's Uncertainty Principle states that you cannot know the position and the momentum of a particle at the same time (I believe this is the main idea behind it). And I have read in various ...
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A few questions on wave packets and uncertainty relations

According to Cohen-Tannoudji the wave-function for a one-dimensional free particle can be written as $$ \psi (x,0)=\frac{1}{\sqrt{2 \pi}} \int g(k) e^{ikx} dk.$$ While $g(k)$ is not specified, there ...
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Does Planck's constant imply limits to computing *results*

... I don't mean quantum effects limiting hardware fabrication sizing. Such small scales have for some time exhibited issues. Rather, along the lines of imagining the smallest possible divisions of ...
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Time energy uncertainty principle [duplicate]

$ \sigma _{H}\sigma _{Q}\geqslant \frac{h}{4\pi }\frac{d\left \langle Q \right \rangle}{dt}$ $\Delta E = \sigma _{H}$ $\Delta t = \frac{\sigma _{Q}}{d\left \langle Q \right \rangle / dt}$ $\Delta E ...
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Heisenberg Uncertainity Principle

If any senior member of the group has access to the book, The Physical Principles of Quantum Theory by W. Heisenberg, then please help me in understanding the first section of chapter 2 where he gives ...
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Including special relativistic effects in momentum in Heisenberg's Uncertainty Principle

I've been told that an electron is somewhere within the space of $10^{-10}m$ and am supposed to find the uncertainty in its velocity. Simply applying $m\Delta x \Delta v \geq \frac{h}{4\pi}$ results ...
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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 ...
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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 ...
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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 ...
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General physics question involving Heisenberg Uncertainty Principle [closed]

Question: An unstable particle produced in a high-energy collision is measured to have an energy of $483\ \mathrm{MeV}$ and an uncertainty in energy of $84\ \mathrm{keV}$. Use the Heisenberg ...
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Why complex functions for explaining wave particle duality?

I have this very bad habit of going to the scratch, discarding all the developments of a theory and worldly knowledge, and ask some fundamental (mostly stupid and naive, as some may say) questions as ...
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Operators Uncertainty

$\hat A$ is an operator. The uncertainty on $\hat{A}$, $\Delta A$ is defined by: $$\Delta A=\sqrt{\langle\hat A^2\rangle - \langle\hat A\rangle^2}$$ what is difference between $\langle\hat ...
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What would be likely to completely stop a subatomic particle assuming it was possible?

Suppose that completely stopping a subatomic particle, such as an electron, could happen under certain conditions. What would be likely ways to get an electron to be perfectly still, or even just stop ...
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Is the uncertainity principle a practical reality, a theoretical law or a measurement problem?

I understand we cannot state with arbitrary precision the position and momentum of a micro-particle as we superpose infinite waves to create a wave packet at the exact position of the particle and ...
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is there any uncertainty on the free particle with a definite momentum $\vec p$?

The probability amplitude for a free particle with momentum $\ p$ and energy $E$ is the complex wave function: $$\psi_{(\vec x , t)}=e^{i(\vec k\cdot \vec x -\omega t)}$$ is there any uncertainty on ...
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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 ...
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Couldn't we measure electrons with good enough technology? [duplicate]

I am a bit confused about the Heisenberg's Uncertainty Principle - just read about it in How to Teach Physics to Your Dog, by Chad Orzel. He states that the reason electrons can't be measured is ...
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Determining zero energy from $k=0$?

I'm curious as to the equations necessary for finding a total energy of 0 (or, I suppose, the energy density of empty space due to quantum fluctuations) in a flat Friedmann universe such as ours. The ...
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Question on Quantum Harmonic Oscillator

My textbook claims that the uncertainty in position of the particle in a quantum harmonic oscillator is $\frac{A}{\sqrt{2}}$ and the uncertainty in the particle momentum is $\frac{p}{\sqrt{2}}$ ...
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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 ...
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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 ...
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Quantum entanglement, quantum measurement, spin and position

By uncertainty principle, we know that determining particle's position at some location is limited. So we cannot determine the position of a particle at some exact point location as this would make ...
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Trapping an electron

Imagine that one could theoretically trap a single electron in a small box, with walls that somehow prevent the electron from passing through and out of the box. Now, the box begins to move in on ...
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NO Uncertainties for particles in their own frames!

Well I had this thought experiment in which a particle observes itself, and something like the following is observed. Taking in mind the uncertainty principle all particles even stopped at 0K jiggle ...
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Velocity of measurement

As per to Heisenberg uncertainty we will not be able to calculate the position and momentum at same instant because by the time we calculate the next of the one, it changes (i.e.) the changes are very ...
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Electron at rest

David Griffiths suggested a website in his book where I got this paper http://www.hep.princeton.edu/~mcdonald/examples/electronatrest.pdf Here the author says classically a particle at rest(in some ...
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Relationship between Energy and Time [closed]

Is there a relationship between energy and time? What is it?
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Repeating a measurement vs uncertainty

The wikipedia says on measurement in quantum mechanics that: Repeating the same measurement without any evolution of the quantum state will lead to the same result. On the other hand, doesn't ...
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Uncertainty Principle tricked - so why not Newtonian Determinism?

Recently I read that some results are obtained in directions of tricking the uncertainty principle. The relevant link is here: http://www.caltech.edu/content/tricking-uncertainty-principle , and the ...
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Do the same experiments yield different results due to the principle of uncertainty?

When thinking about small particles and their uncertainity, I've allways rather seen them being all over the place rather than randomly changing location. I would think that, in the same time, you'd ...
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Uncertainty Principle Upper-bound?

In quantum mechanics, is there an upper bound for the uncertainty principle? I know that quantum harmonic oscillator (QHO) has the uncertainty relation $\sigma_x\sigma_p = \hbar(n+1/2)$, but I think ...
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How can a clock work if the uncertainty principle is true?

If the uncertainty principle and Copenhagen Interpretation are true, then how can a clock tick? Supposedly particles can do all sorts of things when not measured, then how can they be formed into ...
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Change In Momentum In Uncertainty Principle

The most basic explanation for the Heisenberg Uncertainty Principle is that the momentum and position of a quantum particle is not very distinct when an attempt is made to measure them together. But ...
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Collapse of the wave function and Heisenberg uncertainty

I have been studying quantum mechanics for a few weeks, in particular wave mechanics, as created by Schrodinger, and his equation. As a high school student, I haven't found an answer to this question ...