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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Uncertainty principle ( tau lepton) [on hold]

A tau lepton mass's is $1.8$ $\frac{GeV}{c^{2}}$ and has a life time of $0.3ps$. Find $\frac{\Delta m}{m}$. My first idea was calculate the energy uncertainty, then I tried to find $\Delta m$ but, I ...
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26 views

Confusion regarding Vacuum fluctuations, Strings & The Casimir Effect

From Wikipedia: Casimir Effect The typical example is of the two uncharged conductive plates in a vacuum, placed a few nanometers apart. In a classical description, the lack of an external field ...
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96 views

Modern interpretation of wave-particle duality

As far as I understand, in the early days of quantum theory there was quite a lot of debate over how to interpret what it meant for a quantum mechanical object to exhibit both wave-like and ...
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53 views

Proof for fluctuations in vacuum

I'm not a physicist. My understanding of Heisenberg's uncertainty principle and its proof (that is given by an imaginary microscope) is that for example: at a specified time determining the exact ...
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1answer
42 views

Does Heisenberg's uncertainty hold for any two quantum measurements?

Heisenberg's uncertainty principle is most commonly expressed in terms of the uncertainty in measurement of position and momentum of a particle, $$\Delta x\Delta p \geq \hbar$$and uncertainty in ...
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52 views

Uncertainty Principle with the corresponding operators

Why does the corresponding operator do not commute if there is uncertainty related to two observables A and B that states $\Delta A\,\Delta B > 0 $ ?
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1answer
57 views

Measurements in quantum mechanics

Why does measurement change things? I read that measurement changes things because we have to bounce photons off an object to 'see' it and that changes its position, momentum etc... But on the other ...
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1answer
52 views

What is the accuracy when firing an electron at a target?

Consider firing an electron at a target. Let the target be at a distance $d$ and the electron be travelling at a non-relativistic speed $v$. How can we estimate the maximum possible accuracy ...
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33 views

Uncertainty principle and digital camera

I recently got into a discussion in how far (miniaturized) digital cameras are affected by the uncertainty principle. Specifically the question was, whether the uncertainty principle is one of the ...
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1answer
77 views

Heisenberg's uncertainty principle derivation in a ring [duplicate]

The standard derivation But now suppose the space is a ring of length $L$, it seems the derivation could work out exactly the same and we get $$\Delta p \Delta x \geq \hbar/2.$$ But since $\Delta x$ ...
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2answers
78 views

Is the momentum of a particle both uncertain and, independently, also random?

Is momentum of a particle "random" because it is uncertain, or is it uncertain in addition to being random? Is the uncertainty principle and quantum randomness different names the same physical ...
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0answers
33 views

Interpretations of uncertanity principle used for approximation

Just a short question regarding an interpretation of the Heisenberg uncertainty principle $\sigma_x \sigma_p \geq \frac{\hbar}{2}$. Question: Why is it also sometimes that $\Delta x$ and $\Delta ...
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1answer
49 views

Interpretations and approximations of uncertainty principle

Just a short question regarding an interpretation of the Heisenberg uncertainty principle $$\sigma_x \sigma_p \geq \frac{\hbar}{2}$$. Question: The uncertainty principle is sometimes written as ...
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2answers
407 views

Is gravity the current limitation to laser cooling?

This is something I've been wondering for a while. I've read about the experiment with NASA to reach unprecedented cold temperatures in space because of the microgravity environment not being such a ...
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0answers
36 views

Uncertainty in orientation of angular momentum

To calculate the uncertainty it looks like I'm going to find an expression for the root mean square of either $J_x$ or $J_y$, or the $J$ in the x/y plane? But I'm not sure if that's what it means by ...
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0answers
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Gaussian Minimizes Uncertainty - Statement Qualification [duplicate]

On the last page of this paper, the following statements are made (I'll jump right to around the point of interest): Example: Consider $A=p_x$, $B=x$. Then $$\langle A\rangle=\langle ...
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51 views

Quantum mechanics - “God does not play dice” - does he? Or might he not? [duplicate]

I'm a mechanical engineer by training, so please forgive ignorance in my question. Heisenberg's uncertainty principle states (to my understanding) that one cannot measure both position and momentum ...
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1answer
69 views

Butterfly and quantum uncertainty

I'm sorry for the long question. In Brian Greene's book 'The Hidden Reality' he gives a nice illustration of the uncertainty principle. Imagine a butterfly flying around in a room. We would like to ...
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1answer
79 views

How does the uncertainty principle relate to quantum fluctuations?

I found a webpage that just kind of mentions the uncertainty principle lightly but doesn't really go into detail as to why we need it in the first place when considering quantum fluctuations and ...
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0answers
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Is there a limit to the frequency of light? [duplicate]

I am assuming that light frequency would eventually be limited by Planck distance and/or Heisenberg limitations. Could this frequency ever be approached in practical terms?
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1answer
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“Everything is Uncertain.” Heisenberg Uncertainty Principle Question [closed]

I'm new to the concept and only understand that nothing can be measured accurately simultaneously. Is the statement (in title post) true? Can you also use an example from Quantum Mechanics for the ...
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1answer
66 views

Mathematical proof of Bohr's complementarity principle

Complementarity principle, in physics, tenet that a complete knowledge of phenomena on atomic dimensions requires a description of both wave and particle properties. Depending on the experimental ...
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50 views

Calculating Natural Broadening of Emission Lines

I'm trying to demonstrate the small effect of Natural Broadening as compared to other types of broadening (Doppler, Stark, van der Waals, etc.) and my calculations don't match the accepted values. My ...
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0answers
50 views

Heisenberg theory of uncertainty

I was watching a video on YouTube about uncertainty theory of Heisenberg it said that there is a relation between momentum (multiple of mass and speed) and wave length. And the relation is that if ...
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1answer
23 views

Point source of monochromatic photons - self-contradictory in QM?

Suppose we have a point source of photons located somewhere in space. So when the photons are released their location is well known, $\Delta x \approx 0, \Delta y \approx 0, \Delta z \approx 0$ ...
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Heisenberg's uncertainty principle for mean deviation?

The Heisenberg uncertainty principle states that $$\sigma_x \sigma_p \ge \frac{\hbar}{2}$$ However, this is only for the standard deviation. What is the inequality if the mean deviation, defined as ...
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1answer
52 views

Uncertainty relation and quantum gravity

Suppose a quantum version of gravity exists (which I don´t think). What will be the quantities in the uncertainty relation connected with this quantum gravity? Some time ago I sent a letter to Lee ...
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1answer
64 views

Would two identical universes evolve identically? [duplicate]

What if there were 2 universes (completely disconnected - not part of the same multiverse) which were identical and a given point in time (say when they first began). Would these 2 universes evolve in ...
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2answers
219 views

Aharonov Bohm Effect Interaction Energy Interpretation: $\vec E_m = -∇Φ - D\vec A/Dt$?

The Wang paper "An experimental proposal to test the physical effect of the vector potential" proposes an experiment to decide between two interpretations of the Aharonov-Bohm effect: “the ...
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4answers
201 views

Could the Heisenberg uncertainty principle be derived from the speed of light limit? [closed]

Background: As I was thinking about an alternative approach to the question: "why is there a finite speed of light, and why its magnitude corresponds to c?" –ultimately, I was trying to understand ...
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1answer
71 views

A thought experiment about Heisenberg's Uncertainty Principle

If there is a box full of magnetized particles which are taking random movement continuously, then I put a coil connected to a device that can detect the value of current in it and it's designed to ...
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135 views

The integration of Einstein's equations [closed]

Einstein's equation is $$G_{\mu\nu} + \Lambda g_{\mu\nu} = {8 \pi G \over c^4} T_{\mu\nu}$$ where $G_{\mu\nu} = R_{\mu\nu} - (1/2)g_{\mu\nu}\,R$ is the Einstein tensor, which combines the Ricci ...
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4answers
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Uncertainty in Uncertainty?

I was reading about how the Planck's Constant can be measured with LEDs, which made me think about this question. The Heisenberg Uncertainty Principle states that: $$\Delta x \Delta p \ge ...
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104 views

Heisenberg's uncertainty principle at the Planck scale

A particle of mass has a reduced Compton wavelength $$\overline{\lambda}_{C} = \frac {\lambda_{C}}{2 \pi} = \frac {\hbar}{m c}$$ Schwarzschild radius of the particle is $$r_s = ...
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How do we know that there is a wavefunction which collapse?

How do we know that there actually is a wavefunction in the first place which collapse. How do we know that there is a transition from some linear combination of the eigenfunctions to a single one? ...
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1answer
155 views

Could the uncertainty principle create matter in the Universe?

According to quantum mechanics we have the uncertainty principle: $$\Delta E \ \Delta t \geq \frac{\hbar}{2}$$ Near the beginning of the Universe $\Delta t$ is very small and therefore $\Delta E$ is ...
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How to estimate the ground state of a potential well when a confinement dimension is added

I have a finite harmonic potential where I trap an electron. The confinement length changes in size. Now, I'm interested in the ground state energy, so I have this 1D Poisson solver which gives me the ...
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1answer
27 views

Distinguish statistical uncertaincy from noise disturbance relation in slit gedankenexperiment

I am just reading the "Statistical Interpretation of Quantum Mechanics" from L. Ballentine. In section 3.2. he discusses the difference between the observer effect and the statistical ...
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Application of uncertainty principle [duplicate]

why doesn't Heisenberg's uncertainty principle also work for macroscopic bodies which are in-turn made up of quantum-particles? ps: if proof is provided it will be a lot more useful.
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1answer
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Reason behind the uncertainty principle [duplicate]

I know that Heisenberg Uncertainty principles states that the momentum and position of a quantum object can not be determined at the same time. This is very strange to me. I want the basic reason ...
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1answer
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Finding natural linewidth's

I want to check whether my fit parameter for the width of a Lorentzian fit on my digital spectroscopy data for Helium (the 5875 Angstrom line) is what you would expect from the uncertainty principle, ...
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5answers
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Quantum Theory just lazy physics?

Is it true that physicists decided that because they couldn't predict with certainty the location of an electron at any given time, that they just created equations using probability instead, still ...
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1answer
95 views

Relationship between Quantum superposition and Uncertainty principle

I'm an amateur in quantum mechanics. I am confused after reading the following in the wikipedia article about quantum superposition: If the operators corresponding to two observables do not ...
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3answers
79 views

Decrease of uncertainty of momentum with increase of width of infinite well in QM(intuition)

Why does the uncertainty in the momentum decrease with the increase of the width for an energy eigenstate in the classic problem if the infinite well in Quantum Mechanics? I have worked out the ...
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6answers
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Is there something behind non-commuting observables?

Consider a quantum system described by the Hilbert space $\mathcal{H}$ and consider $A,B\in \mathcal{L}(\mathcal{H},\mathcal{H})$ to be observables. If those observables do not commute there's no ...
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1answer
92 views

Is there a simple way to explain quantised conductance? [closed]

I am biologist and I need to pass a nanotechnology class. I am stuck with this term of quantum resistance. Basically this appears to me as normal Ohm's law, except that takes into account Heisenberg ...
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1answer
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Why doesn't $σ_xσ_p$ change with the width of the well in the infinite square well problem (intuition)?

I calculated that the product of the uncertainty in position $\sigma_x$ for the ground state of an infinite square well of width $L$ with the uncertainty in the momentum $\sigma_p$ for the same state, ...
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3answers
111 views

Would the uncertainty principle apply to gravitational waves?

The uncertainty principle is one of the most basic rules of quantum mechanics, but Quantum mechanics still has not been unified with general relativity, so would the uncertainty principle apply to ...
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1answer
110 views

What does it mean that an electron's position is described by probability?

I just read an answer to a Phys.SE question about why electrons don't collide with protons where an answering user said: In quantum mechanics, an electron doesn't have a definite position or ...
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Does Heisenberg's Uncertainty Principle describe real uncertainty or measured uncertainty?

Some derivations of Hesenberg's Uncertainty principle are based on the momentum of light or particles used in measuring an object's position and momentum. Does this lower limit on uncertainty describe ...