This tag is for Heisenberg quantum mechanical uncertainty principle.

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How can an electron be fired at a target when uncertainty principle says it will spread out around axis of motion?

Consider an electron fired at a target. Taking the axis of motion to be $x$, and position to be $(x,y,z)$ then $\Delta y = \Delta z = 0$ Therefore by the uncertainty principle $\Delta p_y = ...
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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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An ideal condition in Heisenbergs uncertainity principle

We all know that the Heisenberg uncertainity principle implies $\Delta x\, \Delta p\geq\frac{\hbar}{2}.$ But is there an ideal condition where we can measure $\Delta x$ to a particular precision and ...
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Why is uncertainty $\geq {\hbar}/{2} $ [duplicate]

Almost all uncertainties (for example the position-momentum uncertainty or time-energy uncertainty) are greater than ${\hbar}/{2} $. But what is the derivation of this uncertainty by Heisenberg? Is ...
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Heisenberg Uncertainty Principle

Question: The uncertainty in position is equal to the uncertainty in momentum. What is the uncertainty in velocity? What I did: I know that the uncertainty in position multiplied by uncertainty in ...
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Question about Heisenberg's uncertainty. [closed]

Heisenberg said that we can't tell precisely both the location of an electron and the momentum of it in the same instant. If we observe one thing, the other is changed. How he concluded this ...
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What is the reason behind why a quantum particle cannot be at rest?

So I've seen different reasonings for this; which is correct, or are they both corollaries of each other? 1) For a particle to be at rest, we would know its momentum and therefore by Heisenberg's ...
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Energy of quarks and the mass of the proton

We know that energy of quarks inside the proton can not be exactly fixed because if it,the 'proton decay' must not be exist. My question is if the energy of quarks inside the proton is not exactly ...
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Finding $\Delta p$ for discontinuous wave function

So I have a triangle Wavefunction defined as: $$\psi(x)=\begin{cases}x &0<x<\frac{L}{2} \\ L-x &\frac{L}{2}<x<L\end{cases}$$ When I try to find the uncertainty in momentum, I ...
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Quantum state with zero standard deviation of position operator

Is any quantum state $|\psi\rangle$ possible such that the standard deviation $\sqrt{\langle\psi|(\Delta\hat{x})^2|\psi\rangle}$ of the position operator $\hat{x}$ is zero? If not, why?
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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What's the proper way to approximate the position uncertainty of a particle?

In this problem: shouldn't $\Delta x\sim\lambda/\sin\theta$ be $$\Delta x\sim \frac{\lambda}{\sin\theta} - \left(\frac{-\lambda}{\sin\theta}\right) = 2\frac{\lambda}{\sin\theta}$$ instead such ...
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Heisenberg's principle in Quantum Cryptography

In quantum cryptography why do we need the Heisenberg uncertainty principle? Edit: I only know the statement of the Heisenberg uncertainity principle. As I know that if Eve tries to know the ...
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Does the uncertainty principle affect event horizons? [duplicate]

I was thinking about black holes. For a simple black hole the event horizon is given by a distance of 2 times mass (energy) of the black hole. (2m). But according to quantum mechanics, if you try to ...
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Does the electron confinement energy vary with temperature?

I was introduced the electron confinement energy. At room temperature thermal energy of a particle is about $k_B T$, where $T=298K$, giving about $25meV$. I was told that $E_\text{confinement}=50emV$, ...
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Luminal motion and the uncertainty principle

I had a thought the other day about a connection between special relativity and the uncertainty principle. According to special relativity, you need an infinite amount of energy to accelerate a ...
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Question on Heisenberg's uncertainty principle [duplicate]

Can we measure limit of precision of measuring wavelength using uncertainty principle? If yes how can we do that?
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Why position and momenta are fluctuating quantities?

In a coordinate basis we have $$\langle \Psi \mid \Psi \rangle = \int \prod_{i=1}^N d^3q_i |\Psi(\textbf{q}_1,\dots,\textbf{q}_N)|^2=1$$ This means that for any quantum state $\mid \Psi ...
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Could quantum particle have a specific velocity without position at all?

I understand that electron spin on different axis is an example of complementary properties, which cannot be measured accurately at the same time. I also understand that if we have an electron is ...
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Are the particle-wave duality and the quantum uncertainty principle united?

In a recent paper by Patrick Coles, Jedrzej Kaniewski, and Stephanie Wehner at the Centre for Quantum Technologies at the National University of Singapore, they came to the conclusion that the ...
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Energy Conservation in Quantum System?

Let us assume, 2 same mass atoms are moving towards each other at equal velocity and they are in course to crash into each other - so what would happen when they do crash into each other? If we use ...
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wormhole time machine and violation of uncertainty? [duplicate]

Let's asssume we have a wormhole that allows sending info to the past and receiving information from the future. Next, we have a particle moving in two dimensions, for which we can evaluate $ p_{y} $ ...
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Quantum relativistic effects

I was performing a thought experiment: let us assume an object is traveling so close to the speed of light that the length of the object is small enough for quantum effects to become noticeable to a ...
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Gedankenexperiment to derive the Robertson uncertainty relation without confusing it with the obersver effect

In the last years there seemed to be much activity on the meaning Heisenberg's uncertainty relation. The main point of the discussion was Heisenbergs noise-disturbance-relation (see: ...
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Uncertainty Principle - measuring momentum on one entangled particle, position on the other

If two entangled particles are sent far apart and then at exactly the same time the position of one, and the momentum of the other, is measured, won't this mean that, because the corresponding values ...
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Could the uncertainty principle theoretically be violated at 0 K? [duplicate]

Ok so please excuse me if the following mental argument is completely ridiculous or obviously flawed :P I was reading about how, even at 0 K (assuming we could experimentally reach such a ...
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Is there a Planck uncertainty?

There are theories which place lower limits on length, time and temperature. Is there a corresponding one for the lower limit for uncertainty? Is there a probability so small it cannot exist in this ...
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What is uncertainty principle exactly? [duplicate]

I've learned a little about uncertainty principle. According to words on Internet, it says that the position and the velocity of an object cannot both be measured exactly at the same time. And there ...
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Quantum properties of objects with zero velocity

Just curious: What would the Heisenberg Uncertainty Principle and De Broglie Wavelength be for a baseball that is not moving (i.e has zero velocity)? Also, since macroscopic objects like baseballs ...
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Huygens and philosophy of the slit

A single (narrow) slit diffraction pattern, can be explained/described classically with Huygens' principle (1678), and quantum mechanically with the Uncertainty principle. If the pattern on the screen ...
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How can I prove this inequality for a harmonic oscillator?

I need a hand with this problem. I have to prove that for a particle in any quantum state in an harmonic potential $$ \langle X\rangle \leq2\Delta E\Delta P/(m \omega^2 \hslash) $$ Here's my ...
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Is uncertainty in velocity via HUP reference frame dependent? [duplicate]

Simply put HUP involves position and momentum, further more consider a mass of 1kg. as momentum is mass X velocity = 1X velocity = velocity for calculation purposes. now for a stationary observer the ...
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What is the physical interpretation of time-energy uncertainty? [duplicate]

I have a question. What is the physical interpretation of time-energy uncertainty?
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The electron: why can't it have both momentum and position [duplicate]

Total amateur here. I've been watching video lectures on Quantum Mechanics and it's said that there is no way to know both position and momentum of an electron at the same time. But is it because when ...
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Interesting (new to me) things in the exposition of Landau's book on QM

In section I.1 (The uncertainty principle), a principle I already know, the author suggests a "relaxing" picture (Unusual): "We have defined "apparatus" as a physical object which is governed, ...
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Uncertain if invoking uncertainty principle for wave function is handwaving [duplicate]

Why doesn't the electron collapse onto the proton in a hydrogen atom? One explanation seems to be given by the Heisenberg uncertainty principle, which follows from the purely physical assertion that ...
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Slit width for minimum spot size in electron slit diffraction if involving uncertainity principle

I don't believe the following is an accurate description of the physical but a homework problem to help understanding. A beam of electron of energy 0.025 eV moving along x-direction, passes ...
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Uncertainty principle implies the non-deterministic universe? [duplicate]

Does the uncertainty principle imply the non-deterministic universe, or just the fact that our model of the universe, the one based on observation, can be at most non-deterministic, since we will not ...
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Doesn't the uncertainty principle mean all particles with identical energy are indistinguishable and hence have an amplitude for exchange?

I wonder if someone could tell me where my logic is going wrong here? If two particles both have definite energy, then they have indefinite position. As their positions could literally be anywhere ...
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551 views

Can Zeno's Dichotomy Paradox be Resolved with Quantum Mechanics?

I would like to start off by saying this is not a philosophical question. I have a specific question pertaining to physics after the following explanation and background information, which I felt was ...
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29 views

Light pulses and energy-time uncertainty principle [duplicate]

Suppose we have a monochromatic light beam. We put an obstacle between source and observer and remove it repeatedly by certain frequency such that observer sees an oscillating intensity of light. Will ...
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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 ...
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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 ...
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199 views

About Heisenberg uncertainty principle [duplicate]

What would happen if someone invented a way to measure both position and momentum precisely? If it is impossible why?
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Naive Uncertainty principle for string theory

Is it possible, in some sense, that a naive uncertainly principle for string theory could be expressed as : $$ \Delta x_i \Delta p_j \Delta \sigma ~=~ \delta_{ij} \hbar \ell_s$$ where $\ell_s$ is ...