This tag is for Heisenberg quantum mechanical uncertainty principle.

learn more… | top users | synonyms

0
votes
1answer
73 views

Uncertainty principle

I am reading about uncertainity principle. My textbook says, if $λ$ is the wavelength of the radiation used to observe the particle then the position of the particle cannot be determined with ...
1
vote
2answers
108 views

Uncertainty principle in quantum field theory

Can the uncertainty principle be derived in quantum field theory? If yes, does is have a different interpretation than quantum mechanics because the coordinates $x_i$ are now parameters and not ...
2
votes
4answers
285 views

Heisenberg uncertainty principle clarification

I found these two examples in a books which demonstrate Heiseberg's uncertainty relation: 1) It shows that when we try to locate a moving electron,we transferred momentum via the photon that we ...
0
votes
1answer
49 views

Heisenberg uncertainty principle applied to large bodies?

Suppose I have a ball of a certain radius inside a box (with the length bigger than the radius) such that the ball fits in the box. The ball has a large mass (1 Kg). Heisenberg uncertainty principle ...
2
votes
1answer
167 views

Why does the uncertainty principle relate position and momentum when mass is always certain?

Why do physicists relate $x$ and $p$, instead of $x$ and $v$ since mass is well known and is not uncertain?
1
vote
2answers
99 views

Is entanglement a consequence of the uncertainty principle?

I am an aspiring physicist and once, I asked my professor on what triggers quantum entanglement and he graciously remarked "The great uncertainty principle!" - I was slightly confused and didn't say ...
1
vote
2answers
59 views

reflection of light and the uncertainty principle

I've heard that light reflects the same angle that it falls and so if we know the position of photon (the spot where it hits the surface) and the direction of where it shall go - that's violation of ...
0
votes
1answer
49 views

Why do momentum and position have the same direction in space in the Heisenberg Uncertainty Principle?

It is known that $\Delta p \Delta x \geq \frac{h}{4\pi}$. I read that the two uncertainties must be along same axes. Why is that so?
-1
votes
1answer
78 views

How to derive Uncertainty Principle relation?

How to derive Heisenberg Uncertainty Principle relation?
0
votes
1answer
28 views

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 $E_\text{confinement}=50emV$, ...
9
votes
2answers
594 views

How do tracking detectors in particle accelerators create the pretty pictures we see?

I have read several sources about tracking detectors used in particle accelerators like LHC, but still have not found a more detailed source that can still be understood by a layperson like myself. I ...
1
vote
2answers
90 views

Why is what Heisenberg's uncertainty principle describes true?

As I understand it, Heisenberg's uncertainty principle (HUP) states that the more precisely we know the location of an electron, the less precisely we know its momentum, and vice versa. However, I've ...
1
vote
1answer
36 views

Minimal phase space volume $h^3$ out of Heisenberg's principle

So the explanation in my text book is this: we have a phase space volume $\Delta x\Delta y\Delta z\Delta p_x\Delta p_y\Delta p_z$. Now they state that Heisenberg's uncertainty principle states $\Delta ...
1
vote
1answer
44 views

Uncertainty relation and instrumental errors

I was puzzled recently by what I've read in the internets about Heisenberg's uncertainty principle (one probably should never do this). It claimed that in the usual relation $$ ...
4
votes
2answers
223 views

Using the uncertainty principle to estimate the ground state energy of hydrogen

I have been reading through this estimate of the ground state energy of hydrogen and others like it. In this one it says it is using the uncertainty principal but then proceeded to use the following: ...
0
votes
1answer
37 views

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 ...
0
votes
0answers
43 views

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?
2
votes
1answer
74 views

Entanglement and the uncertainty principle

Suppose you have two maximally entangled particles. You measure the spin about the x axis of the first and the spin about the y axis of the second. But both spins cannot be known simultaneously, so ...
0
votes
2answers
32 views

How can the uncertainty principle be used to deduce range of a force from properties of the force carrier?

Question: How can the uncertainty principle be used to deduce range of a force from properties of the force carrier? My thoughts? Not too sure how this can be done and would like some advice. ...
2
votes
5answers
178 views

Which way will the pencil fall?

Let's say you had a perfect pencil, with a point which was just that one point (see this question). The pencil's mass was perfectly distributed, and there are no flaws in the craftsmanship. Let's say ...
4
votes
6answers
884 views

What is the uncertainty principle?

I looked on Wikpedia for information on the uncertainty principle, but after reading it I still had no idea. I know it has something to do with how many things you can hold at some spot for some ...
0
votes
1answer
71 views

Do all quantum systems have zero point energy ?

I understand that it is possible to write an uncertainty relation between the Hamiltonian of a system and time, where the time uncertainity is defined by the amount of time it takes an arbitrary ...
-4
votes
2answers
83 views

Classical notion of trajectory [closed]

Why the classical notion of trajectory is meaningless in quantum mechanics? I am asking here about notion of trajectory from classical mechanics and why in quantum mechanics we cannot use it or is ...
62
votes
7answers
11k views

Can we theoretically balance a perfectly symmetrical pencil on its one-atom tip?

I was asked by an undergrad student about this question. I think if we were to take away air molecules around the pencil and cool it to absolute zero, that pencil would theoretically balance. Am I ...
0
votes
0answers
50 views

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 ...
0
votes
2answers
98 views

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 ...
1
vote
0answers
93 views

Quantum Gravity Singularity Question?

I am not a expert in QG (Quantum Gravity) or GR (General Relativity) for that matter so please forgive if I make any small mistakes, its just a curious question but I know that a singularity is a ...
1
vote
0answers
38 views

Minimum Uncertainty Wavepackets

I'm reading over some lecture notes on minimum uncertainty wavepackets in quantum mechanics, and I've come across a statement that I'm not entirely convinced by. My take on minimum uncertainty states ...
0
votes
0answers
76 views

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 ...
0
votes
1answer
50 views

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 ...
2
votes
0answers
34 views

Group velocity and calculating wavelength [closed]

A stone tossed into a body of water creates a disturbance at the point of impact that lasts for Dt = 4.0s. Measurements indicates that the wave speed is v = 25 cm/s. (a) Over what distance on ...
0
votes
2answers
86 views

Why uncertainty principle on a large scale doesn't impose limitations on precision?

The question is By choosing reasonable numerical values for mass and velocity, show that $\Delta x \Delta p >=\frac{ \hbar}{2}$ doesn't impose any limitations on the precision with which the ...
1
vote
1answer
163 views

Are the authors saying that the observer effect plays no role in Bohr's thought experiment of the Heisenberg uncertainty principle?

Here is an excerpt from Eisberg & Resnick's Quantum Physics of Atoms, Molecules, Solids, Nuclei, and Particles. Here is introducing Bohr's though experiment to establish a physical origin for the ...
3
votes
3answers
598 views

Uncertainty principle and measurement

I would like to really understand how the uncertainty principle in QM works, from a practical point of view. So this is my narrative of how an experiment goes, and I'm quickly in trouble: we prepare ...
0
votes
2answers
39 views

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} $ ...
2
votes
2answers
100 views

Heisenberg uncertainty and probabilistic nature of QM

I am trying to understand whether the HUP and the probabilistic nature of QM are orthogonal or not. By that I mean that the HUP fundamentally derives from operators not commuting, which is the ...
0
votes
2answers
43 views

RH side of the Uncertainty principle: when is it a number and when an expectation value?

The uncertainty principle between the position $x$ and the momentum $p$ is given by: $$ \sigma_x \sigma_p \geq \hbar/2,$$ whereas for the $x$ and $y$ components of the angular momentum is given by: ...
11
votes
3answers
333 views

Is there a prediction of quantum mechanics that could be construed as representing an “energy-time uncertainty relation?” [duplicate]

As the title suggests. Is there a prediction of quantum mechanics that could be construed as representing an "energy-time uncertainty relation?" Does there exist any reference to such a prediction, or ...
1
vote
0answers
19 views

Diffraction from a single slit experiment and Heisenberg's uncertainty principle [duplicate]

Practically how to separated between Fraunhofer and Fresnel diffraction? Do all diffraction fringes from single slit have same peaks? Why?
0
votes
3answers
99 views

Energy of system in eigenstate of Hamiltonian

I know how to find the spectrum of the Hamiltonian to get the allowed energies for a system. If the spectrum is quantized, I can get definite values for each energy level. But when the system is in ...
1
vote
1answer
64 views

Why can't we define a unique wavelength for a short wave train? [duplicate]

Here we encounter a strange thing about waves; a very simple thing . . .namely, we cannot define a unique wavelength for a short wave train. Such a wave train does not have a definite wavelength; ...
0
votes
0answers
61 views

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 ...
0
votes
1answer
77 views

electrons inside nucleus and uncertainty principle [closed]

State the assumptions of the proton-electron model of the nucleus. Show that if one uses the Heisenberg uncertainty relation to estimate the speed of an electron inside a nucleus with a diameter of ...
0
votes
2answers
154 views

The uncertainty principle and spin

I realize that this may be a very basic question, but I've been unable to find the answer elsewhere so thanks in advance for the help. Suppose an electron's spin is measured about an axis, and then ...
2
votes
2answers
54 views

Can mass be uncertain?

If you can have uncertainty in momentum, then wouldn't you have uncertainty in mass and velocity? Why can't mass be uncertain?
4
votes
6answers
557 views

Explanation for the EPR-like paradox

I am trying to understand the process of Quantum Entanglement for use in Quantum computers. The problem I have is this: Suppose some nuclear process emits an electron-positron pair. Now after ...
0
votes
1answer
70 views

Can we put $\Delta p, \Delta x, \Delta E, \Delta t$ into one big uncertainty equation?

According to my calculations $x$ * $p$ has unit $[kg m^2/s]$ which is what we would get if we multiply $E$ by $t$ So $$ Et = xp$$ Starting from here, can we some how derive a formula that puts all ...
0
votes
2answers
108 views

Why only 1 component of angular momentum?

Griffiths says that you can have only 1 well defined component of the angular momentum because of the uncertainty principle. From the uncertainty principle, we get that $$ \sigma_{L_x}\sigma_{L_y} ...
1
vote
1answer
51 views

On quantum randomness, the longest weather predictions and perfect macroscopic caos

Which is the maximum number of days we can predict future weather conditions with a reasonable degree of accuracy if we knew all of the initial conditions of everything that effects the weather down ...
0
votes
0answers
38 views

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: ...