# 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.

227 questions with no upvoted or accepted answers
Filter by
Sorted by
Tagged with
757 views

### Which position and momentum distributions arise from some wave function?

Consider a particle in one dimension with wave function $\psi$. The probability density function describing how likely it is to find it in a given position is given by $f(x)=\left|\psi(x)\right|^2$. ...
175 views

### On an Uncertainty Relation for Angular Variables

I'm looking for a proof of the Angular Momentum - Angle uncertainty relation $$\frac{\Delta L \Delta \theta}{1-(3/\pi^2)\Delta \theta^2} \geq \frac{\hbar}{2}$$ which does not involve solving the ...
605 views

### What is the maximum number of bounces a ball can be expected to make on another fixed ball of same radius on the ground?

In the book 'Quantum Mechanics' by Leonard I. Schiff, this question can be found at the end of chapter one. More specifically it asks: A perfectly elastic ping pong ball is dropped in vacuum from a ...
• 466
2k views

• 514
63 views

### Quantum conditional von Neumann entropy - changing system I condition on, i.e. bipartite vs tripartite entropic uncertainty relation with qu. memory

I am reading Entropic Uncertainty Relations and their Applications by Patrick J. Coles, Mario Berta, Marco Tomamichel and Stephanie Wehner. https://arxiv.org/abs/1511.04857 I am trying to reproduce ...
181 views

### Uncertainty principle in relativistic quantum mechanics

In Walter Greiner book about relativistic quantum mechanics, he writes the uncertainty relations for 4-position and 4-momentum in a neat way as: $$[p^\mu, x^\nu] = i\hbar \eta^{\mu\nu}{\bf 1}$$ with ...
• 119
148 views

### Can current and voltage be linked by an uncertainty relation when electrons tunnel through a barrier?

Quantum tunneling has been shown to be linked to uncertainty relations for some observables involved in the system. For instance, if we consider electrons tunneling through a potential barrier it can ...
• 31
160 views

### Quantum tunneling for bound states

In QM, take a particle in a bound state in $\mathbb{R}^n$ subject to a potential (need not be smooth and not necessarily bounded above, but is bounded from below, say, something that might roughly ...
• 2,024
209 views

### Is there a Heisenberg Force?

If I read him correctly, in his book Quantum Theory, David Bohm argues that the reason an electron doesn't collapse into the nucleus is there is essentially a pressure due to the uncertainty principle ...
• 2,728
104 views

### Connection Between Gaussian Fourier Transform and Minimal Uncertainty

The Fourier Transform of a Gaussian is a Gaussian. In QM, we get minimal uncertainty for a (normalized) Gaussian wave packet: $\Delta x\cdot \Delta p=\hbar /2$ Does the second fact has nothing to do ...
956 views

### The Heisenberg Uncertainty in Bose Einstein condensates

What happens to the Heisenberg uncertainty principle, when a system reaches the Bose-Einstein condensed state? In our statistical mechanics lecture, we derived the following formula for the fraction ...
• 383
136 views

### Underlying C*Algebra operators in standard quantum mechanics?

Linearity in standard quantum mechanics (QM) is the key to making the math possible in this field, but the presence of nonlinear operators in QM is what is more generally dealt with. Working with the ...
188 views

### 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 ...
271 views

• 94
372 views

### Are phase and particle (photon) number in QED conjugated variables?

I found in A. Zee's book "QFT in a nutshell" (1.edition) the interesting relation (8) respectively (9) in chapter III section 5 (p.173) which states that in a collective of non-relativistic bosons the ...
• 9,748
94 views

### Spread of the (smeared) field observable under time-evolution

Setup: Essentially, I'm interested in performing an analysis which is completely standard in QM, but I've never seen the analogue in QFT: Given I measure a system to have some value of its canonical ...
• 695
92 views

### In Cardy-Verlinde generalized uncertainty principle (GUP), how we know that the alpha is a constant of order one?

The GUP equation [1] is, $$\Delta x_i\geq\frac{\hbar}{\Delta p_i}+\alpha^2l_p^2\frac{\Delta p_i}{\hbar},$$ where $l_p$ is the Planck length. How do we know that $\alpha$ has a order of unity [1]? What'...
• 177
189 views

### Why is information conservation not restricted by the uncertainty principle?

The idea of information conservation seems to be: if all field equations/states of all particles/matter/waves at a certain time are known, all trajectories/waves can be backpropagated to retrieve all ...
• 409
251 views

• 1,788
935 views

### Uncertainty Principle and Bohmian mechanics

The Uncertainty Principle is a relationship between measurements of pairs of attributes, position and momentum, as well as energy and time. Perfect precision of one attribute's measurement leads to a ...
• 125
134 views

### commutator to entropy in an uncertainty relationship?

Question: Does there exist a commutator to entropy in an uncertainty relationship? Similar Energy and time for instance.
• 618
1 vote
28 views

### Heisenberg uncertainty principle and QKD protocols

Some Quantum Key Distribution (QKD) protocols, like the well-known BB84, are said to be based on the uncertainty principle which I assume it to be the Heisenberg principle. This one states that two ...
• 151
1 vote
47 views

### Photon and Observer effect

We cannot determine the position and momentum of a particle simultaneously with certainty . The product of uncertainty of them is greater than or equal to reduce planck's constant . The reason for ...
• 61
1 vote