# 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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### Uncertainty principle for single slit diffraction

Let's suppose there is an aperture of diameter $d$. If particles undergoes diffraction at the aperture, since uncertainty in the "x-coordinate" is $\Delta x = d/2$, by the Uncertainty ...
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### I can't track too many particle ==> Statistical Mechanics OR Quantum uncertainity ==> Statistical Mechanics

I'm sort of confused with these two ideas. We start by saying that the trajectory of the particle can be described by giving the phase space coordinate $(q,p)$. So Given the initial condition, I can ...
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### Why we can stand on the floor? [duplicate]

Feynman (Volume 1, 38-4) seems to explain the normal force of a floor acting on a table as quantum mechanical, arising from the Pauli Exclusion Principle and also, the Heisenberg Uncertainty Principle....
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### Is it possible the quantum world to be actually deterministic after all? [closed]

Possible the "Heisenberg Uncertainty Principle" (HUP) describes the fact that we are not able to probe beyond a small size scale into the quantum world because the relative long light waves ...
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### Why don't we observe quantum effects for large massive objects at rest? [duplicate]

The de Broglie wavelength of any massive particle is $\lambda = \frac{h}{p}$. We know that if a large object (say, a baseball) is at rest, it will have $p=0$ and hence $\lambda$ will be infinite. This ...
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### How could theoretical physics without experimentalists aid distinguish observer effect from Kennard's uncertainty principle?

Regarding this experiment which was carried out in 2012: https://arxiv.org/abs/1208.0034 I'm wondering how could the scientific society be totally convinced(prior to this paper being published) based ...
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### Is it an assumption that Heisenberg's uncertainty principles applies to the vacuum or is there proof?

The Heisenberg uncertainty principle was found to apply to all particles in physics. Was it an assumption that it should also apply to the vacuum? One of the consequence of this extrapolation is that ...
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### What are Uncertainties in Quantum Mechanics intuitively? [duplicate]

So $\Delta x$ and $\Delta p$ are uncertainties in quantum mechanics. What exactly does the term "uncertainties" mean?
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### Possibility of staying within nucleus for a electron according to Uncertainty Principle

Academic Problem: According to Uncertainty Principle, show that electron can't stay within nucleus. That's a general problem indeed. Anyway, we know that uncertainty of position in this case can't ...
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### Are “intelligent” systems able to bypass the uncertainty principle?

This paper talks about finding theoretical correlations to experiential phenomena in quantum mechanical experiments using artificial intelligence (AI). If AI applications can be sufficiently well ...
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### Why isn't the final screen in the double slit experiment a 'detector' which would collapse the wave function retroactively?

I'm sorry if this is a stupid question but I'm someone who is not from the physics world trying to learn about this for the first time (I'm reading Daniel Golding's Quantum Physics for Beginners and ...
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### Interfering alternatives and identical particles in Feynman and Hibbs

I am currently self-studying Feynman and Hibbs, and in his first chapter, Feynman talked about 'alternatives' like the various possibilities or paths an experiment can take. He defined two different ...
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### Feynman's non-rigid double slit experiment

I am currently reading Quantum Mechanics and Path Integrals by Feynman and Hibbs, and in the very first chapter, Feynman qualitatively tries to motivate the Uncertainty Principle. He started out with ...
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### Subsequent measurement of energy [duplicate]

I am interested in the subsequent measurement of energy, like assume the energy of the electron was measured to be $E_1$ and the wavefunction of the electron is described by a finite superposition of ...
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### What does it “physically” mean, in terms of uncertainty and measurements, for a commutator to be different than zero in quantum mechanics?

Let's consider the commutator $[L_i,L_j] = i \hbar L_k$ of the angular momentum. The consequence of this equation is that two components of the angular momentum cannot be simultaneously measured. I ...
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### Does the Kalman filter incorporate a Heisenberg-like uncertainty principle?

In the case of mechanical systems, applying the Kalman filter involves combining model based prediction (using an apriori known dynamical model) with real-world noisy observations of the positions and ...
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### The frequency spread of a wavepacket from a femtosecond laser pulse

I want to ask a question about the frequency spread of a wavepacket from a femtosecond laser pulse. I was presented with the following question today: Compute the frequency spread of a wavepacket ...
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### If Heisenberg uncertainty principle involves the standard deviation of quantities then why do we use it in a different way as here?

Heisenberg uncertainty principle is mathematically given as $$\sigma_x \cdot \sigma_p \ge {{\hbar} \over {2}}$$ The two terms on the left being the standard deviations of position and momentum. But on ...
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### Heisenberg uncertainty principle in German [closed]

I have heard that uncertainty was not the actual translation for the word which Heisenberg had used to describe his original principle (in German). The translated meaning is a bit different. What was ...
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### Heisenberg uncertainty principle fluctuations and dimensions less than 3+1

I've been looking at the 1+1 dimensional Dirac equation recently and am wondering if the Heisenberg uncertainty principle would allow application of said model to spin-1/2 fermions in 3+1 dimensions ...
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### The definition of complementarity principle

I am looking for a precise definition of complementary principle. It is rather briefly mentioned in the textbook, and I feel that authors have deliberately avoided defining it precisely. I'm a math ...
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Suppose that we have a quantum particle with defined momentum $p=\hbar k$, this means that the particle is in an eigenstates of the momentum operator $|k \rangle$. We can now ask: what is the ...
I am trying to show the uncertainty relation of $\Delta x\Delta p = \frac{\hbar}{2}$ using a gaussian wave function and its Fourier transform. I have found correctly the uncertainty in position \$\...