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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Do emitted photons have a well defined frequency or just a spread as per HUP?

I have read this question: Conservation of Energy in photon exchange between two atoms where Kurshal Shah in a comment says: As per the energy-time uncertainty relation, the emitted photon ...
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Why does heisenberg uncertainty principle work? [duplicate]

Hiesenberg's Uncertainty Principle states that inaccuracy in momentum and position will always be there and we will never ever be able to get it 100% accurate. Suppose in future millions of years from ...
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Does this wave function from Zettili book (Quantum Mechanics) violate uncertainy principle?

I am not sure whether my question counts as homework and exercises or not, because I already know the answer. The problem is, I find Zettili answer rather unsatisfactory. Problem 1.11 (a) Find the ...
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Hawking temperature, uncertainty principle and size of a black hole

I was playing with the Hawking temperature formula $$T_H = \frac{\hbar\ c^3}{8 \pi\ G\ M\ k_B}$$ and I thought it would be interesting to associate a velocity to this temperature: $$k_B\ T_H = \frac{1}...
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Hard boundary of Heisenberg's uncertainty principle

Heisenberg's uncertainty principle states that we cannot know the position and momentum of subatomic particles simultaneously...but what exactly is the boundary of size of such a particle? Does such a ...
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A doubt on waves

We know that every progressive wave depends on its position X and time variable T. y= Asin (kx- wt) My doubt is "Even an election is a wave (de broglie's hypothesis), but we cannot write its equation ...
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schrodinger's cat experiment puzzle [duplicate]

In Schrodinger experiment, the cat is both alive and dead until an observer opens the box to observe the radioactive decay - but why isn't the cat itself an observer?
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What is the characteristic of a property?

Background: The following two observations are , in my understanding, pretty much accepted in quantum theory: Location is a property which is not preexisting but is established by measurement. It is ...
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Can momenta eigenstate written in term of $x$ be an eigenfunction of position?

Being non-commuatable operators, momentum and position cannot have simultaneous eigenfunctions. But in "Theoretical Minimum: QM" by Lenny Susskind and Artsy Friedman, in explaining Heisenberg's ...
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Can the “external” field in DFT be that of an electron?

In my experience with (Kohn-Sham) density functional theory, the external potential is due to a massive particle like a nucleus or ion. I have never seen an electron be the source of the potential, ...
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Quantum Zeno effect and Heisenberg uncertainty principle

The Heisenberg uncertainty principle forbids the existence of static atoms But in the Quantum Zeno effect observing atoms makes them stand still does the Quantum Zeno effect violate the Heisenberg ...
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Can measurement of the momentum of a particle can be done without observing its position?

Uncertainty principle says that one cannot measure exactly the position and momentum of a particle at same time. As per common understanding when we are measuring momentum of an object it is ...
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Heuristic for large $x$ behavior from small $q$ behavior of Fourier Transform

If I have a function $h(\mathbf x)$ which may be written $$h(\mathbf x)= \int \frac{\text{d}^d\mathbf q}{(2\pi)^d} \, h(\mathbf q) e^{-i \mathbf q \cdot \mathbf x}$$ and assume spherical ...
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Proof of Heisenberg's uncertainty principle for operators [duplicate]

Why is Heisenberg's uncertainty principle for the position and momentum operators in the Cartesian coordinates system defined as $$\sigma_{x}^{2} \sigma_{p_{x}}^{2} \geqslant\left(\frac{1}{2 i}\...
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56 views

How can the momentum-position Uncertainty Principle not violate conservation of energy? [duplicate]

As far as I understand, the primary reason why an electron doesn't fall into a nucleus is that, when it gets close, it has a sufficiently high probability of having a lot of momentum to get back to ...
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What does it mean to say “since the magnitude of actual momentum is smaller than uncertainty, the value cannot be defined”?

What does it mean to say "since the magnitude of actual momentum is smaller than uncertainty, the value cannot be defined"? Original question: Uncertainty in the momentum of an electron is $ 2.6 \...
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Quantum mechanics limits to understanding the Universe [closed]

By definition, a wave function does not describe a particle's state exactly, we can only know that information when we make measurements and thus collapse the wave function. This gives us a lot of ...
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How does the Uncertainty Principle work? [duplicate]

In my textbook they have explained the Heisenberg's uncertainty principle using the example where you cannot measure the position of the electron using the photon because the wavelength of the photon ...
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1answer
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Heisenbergs uncertainity principle clashing with momentum conservation

If a particle of mass $M$ spontaneously explodes breaking up into two pieces we know by energy conservation $m_1 v_1 = -m_2v_2$, so if i measure the position of $m_1$ accurately and measure the ...
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Uncertainty of place and momentum of free particle

Given the Hamiltonian $H=\frac{P^2}{2m}$. I want to know $<x(t)>, <p(t)>, ( \delta x(t))^2,( \delta p(t))^2$ Using the Ehrenfest Theorem I have: $\frac{d}{dt}<x>=\frac{i}{\hbar}&...
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Heisenberg's Uncertainty Principle - finding uncertainty in wavelength

I am confused about this problem: I needed to find the uncertainty of a wavelength using Heisenberg's uncertainty principle. In the solution, they differentiated $λ=c/f$ with respect to frequency to ...
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Uncertainty principle for $\Delta\frac{1}{x}\Delta p$

I've tried to determine uncertainty for operators $\xi=\frac{1}{x}$ and $p$. To do so, I used relation that $B^{-1}[A, B]B^{-1} = -[A, B^{-1}]$ and so I got: $$ \frac{1}{x}[p, x]\frac{1}{x} = \frac{-i ...
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Double sit experiment and Uncertainty

If we try to an electron with a high energy photon, we precisely detect its position, while its momentum becomes totally uncertain. On the other hand, if we detect it using a low energy photon, its ...
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Is there a uncertainty relation between viscosity and volume in fluids?

If I make no mistake, dynamic viscosity $\eta$ is measured in $ \rm kg /(s\, m) $. And volume is measured in $\rm m^3$. The product of the two has the same units of Planck's quantum of action $\hbar$...
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What does it mean: $[\langle(\Delta x)^2\rangle\langle(\Delta p)^2\rangle](t)$?

I got following expression regarding linear harmonic oscillator in quantum mechanics, and I don't understand what it means. $[\langle(\Delta x)^2\rangle\langle(\Delta p)^2\rangle](t)$ $\Delta x$ ...
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Uncertainity relation of Kinetic energy with position

In R. Shankar's Principle of quantum mechanics book in the problem Now $$\Delta T = \frac{-\hbar^2}{2m} \Delta( p^2)$$ And I don't arrive anywhere using this, but I also know that $\Delta A \...
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Heisenberg's Uncertainty principle: Position of momentum of Electron orbital

I need some clarification in my understanding of HUP with respect to electron in an atom. This is my current understanding, Position of electron here means which orbit (Quatized orbits around nucleus)...
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Why does zero $x$ angular momentum imply nonzero $z$ angular momentum?

Assume we have a state $\psi =|n, L =1, L_x =0\rangle$. If we compute it's reprentation in $L_z$ basis we get: $$\psi = \frac{1}{\sqrt{2}}|n, L =1, L_z =1\rangle - \frac{1}{\sqrt{2}}|n, L =1, L_z =-1\...
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Can you help me clear up the double slit experiment?

So I know what happens in a double slit experiment and that if you put an observer, it changes the outcome of the experiment. It has to do with Heisenberg's uncertainty, but how does his uncertainty ...
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Uncertainty Principle for a Particle on a Ring [duplicate]

In the case of a particle on a line, if I prepare an (although non-normalizable) eigenstate of the momentum so that the uncertainty in the measurement of the momentum vanishes, the uncertainty ...
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Quantum state where uncertainty in kinetic energy is zero?

While reading Shankar's book on Quantum Mechanics, I encountered an interesting problem: Compute $\Delta T\cdot\Delta X$, where $T = P^2/2m$. I found several solutions online which arrive at the ...
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Heisenberg's Uncertainty Principle about electrons [closed]

According to Heisenberg's Uncertainty Principle when we shoot or project photons on an electron from one side then there is 100% possibility that there is some error in calculating the position and ...
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1answer
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Uncertainty principle for a particle of known momentum

For a particle of known momentum we know the wave function. But why is that in that case we have uncertainty in momentum then according to uncertainty principle ∆x∆p>=h/2π? If so then uncertainty in ...
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Can faster sampling frequency solve the x-ray diffraction phase problem?

In the x-ray diffraction, only the intensity the light that hits the detector is captured while the phase of the light is not determined. The energy flux of the light is the Poynting vector. For a ...
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Heisenberg's Microscope and the Compton effect

https://www.youtube.com/watch?v=dgoA_jmGIcA&t=459s Hi, this is my first question on physics stack exchange. I'm in my second year in college and I'm currently learning quantum/nuclear physics. So ...
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Doubt on application of uncertainty principle for an ion trap

Ion trap involves the application of an electromagnetic field to suspend and confine a charged particle. At the centre of this picture, you see a saddle shape. This means that the ions are pushed ...
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Is this explanation for the uncertainty principle correct?

In a pre-print I read that "The position of the particle is indeterminate as it could be anywhere along the wave packet. Hence compressing the wave packet to reduce the indeterminacy in position will ...
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Uncertainty principle in classical mechanics and quantum mechanics

I was just listening to the Leonard Susskind lectures on youtube on qunatum mechanics basics. He said that uncertainty principle in classical mechanics is completely different from that of quantum ...
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Physical interpretation of eliminating the real component when deriving the uncertainty principle

I've been working on some quantum information theory problems and I've revisited Griffith's Quantum Mechanics. On page 109, he derives the uncertainty principle. He goes through the steps: For ...
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Does wave-particle duality rely on accepting the Copenhagen interpretation?

If you're a scientist that subscribes to the many worlds theorem, does that mean you do not accept wave particle duality? Seeing as MW postulates that the wave or particle form has always existed that ...
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What is exactly a quantum fluctuation?

According to the quantum fluctuation by Heisenberg Uncertainty Principle, matters and antimatters are created and disappearing by colliding in an almost complete vacuumed area of space near the event ...
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In Bohmian mechanics, do electrons move inside an atom?

Look at http://www.bohmian-mechanics.net/whatisbm_pictures_hydrogen.html. It is mentioned that in the rest states of a bound electron, the position of the electron is stationary, since the ...
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General commutation question

If I have three general observables, $\hat{C}$, $\hat{H}$, and $\hat{L}$, and the commutation relation between $\hat{C}$ and $\hat{H}$ is given by, $$ [\hat{C}, \hat{H}] = \hbar \hat{L} $$ At the ...
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By recombination ion/electron does predominataly the ground level form?

When an electron is near an ion and has small velocity it will be certainly captured and both form an atom. I think that the electron will predominantly release energy dE just the proper quantity ...
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What would happen if the opposite complementary variables of two entangled particles were measured at the same time?

Many explanations about the uncertainty principle and its related EPR paradox state that it is impossible to measure opposite complementary variables on different entangled particles; for example, ...
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Is polarization complementary along its different axes?

Is polarization complementary along its different axes -- much like the spin of a particle is -- thus implying that the uncertainty principle holds for polarization measurements on these different ...
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What does the Heisenberg principle actually mean? [duplicate]

As far as I can understand, the Heisenberg principle limits the possibility of calculating the exact position and momentum of electrons, as the light we use to observe it changes it's velocity. But ...
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Virtual pair of particle-antiparticles trajectory [duplicate]

Is it possible to do heuristic calculations on virtual pair of particle-antiparticle trajectories that appear in a vacuum? For example, what is the maximum distance between them during virtual process?...
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Why doesn't detecting a photon's position after passing through a narrow slit violate HUP?

I understand that after passing through a narrow slit a photon's momentum is uncertain, however since its position can be inferred from having passed through the slit, a subsequent position ...
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Does uncertainty principle truly represent the “lower bound” of the information we can obtained from a pair of noncommunicable operator?

Background I: Suppose the commonly used non commuting operator $\hat p$ and $\hat x$. The uncertainty principle told us that $\sigma_p\sigma_x\geq \frac{\hbar}{2}$. In standard quantum mechanic ...