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2
votes
1answer
68 views

Heisenberg uncertainty principle meaning and using it to determine approximate sizes confusion

I was always under the impression that the Heisenberg uncertainty principle tells us to what precision we can make a momentum measurement given a position one. However, when doing quantum mechanics ...
2
votes
2answers
58 views

Relation between momentum and momentum uncertainty

I have read the following sentence in a section which is explaining why particle accelerators need such high energy: As we require high precision position measurement, the Heisenberg uncertainty ...
-5
votes
1answer
95 views

Is the uncertainty principle a circular argument? [closed]

Uncertainty is due to the measurement techniques humans tend to use requiring photoelectric effect. The Planck constant is due to the photoelectric effect. If the standard deviation of measurement was ...
0
votes
1answer
118 views

Smallest uncertainty ever achieved in position measurement in QM?

The Heisenberg uncertainty principle states that $$\Delta x\Delta y\geq\hbar/2$$ Since the magnitude of $\hbar$ is $10^{-34}$ we could measure both $x$ and $p$ with an uncertainty magnitude of $10^{-...
0
votes
1answer
195 views

Maximum Uncertainty of a Measurement?

I know the state of a system at a time T1, and perform a measurement at a later time T2. My question is this: is there a maximum uncertainty on what state I could expect to measure the system? Of ...
0
votes
1answer
76 views

What is currently the approximate precision or accuracy $\delta r$ with which the position $r$ of an electron can be measured?

The measurement of the position of an electron has associated, on the one hand, a quantum uncertainty $\Delta r$ which gives an idea of the probability cloud where the electron can appear, for example ...
2
votes
1answer
86 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 ...
2
votes
0answers
268 views

Simultaneous measurement of non-commuting observables without uncertainty

A pair of non-commuting Observables $\hat{X}$ and $\hat{P}$ does not have a common set of eigenfunctions, i.e., it can not be measured simultaneously. Let us for the sake of simplicity assume that $[\...
2
votes
3answers
237 views

Does every interaction of quantum objects introduce backaction?

The motivation of this question is the following experiment: Assume you have quantum mechanical oscillator, e.g. a particle in a potential $V(q_x)\propto q_x^2$. Now the position of the particle ...
4
votes
3answers
4k views

What is the experiment used to actually observe the position of the electron in the H atom?

Prior to observation, the electron can be found anywhere (from inside the nucleus to the ends of the universe), but once its position is determined the answer is precise (albeit its momentum is not ...
0
votes
3answers
755 views

Repeating a measurement vs uncertainty

The wikipedia says on measurement in quantum mechanics that: Repeating the same measurement without any evolution of the quantum state will lead to the same result. On the other hand, doesn't ...
1
vote
2answers
122 views

can one measure energy to a finite accuracy?

Can one measure energy to a finite accuracy in a bounded amount of time? I don't know much about QM, but someone told me that the energy-time uncertainty principle says that it would take an infinite ...
2
votes
3answers
956 views

Measuring position and momentum at the same time?

In a non-relativistic quantum mechanical system in an infinite potential well. I try to measure the energy and the position of the system simultaneously. Since, the respective operators do commute ...
5
votes
5answers
829 views

Uncertainty principle with two photons

Imagine an experimental setup in which you have to measure the momentum and location of a particle. To measure it we know we will have to affect it, and the uncertainty principle would come into the ...
18
votes
1answer
2k views

Is the Uncertainty Principle valid for information about the past?

My layman understanding of the Uncertainty Principle is that you can't determine the both the position and momentum of a particle at the same point in time, because measuring one variable changes the ...
11
votes
7answers
2k views

Shouldn't the Uncertainty Principle be intuitively obvious, at least when talking about the position and momentum of an object?

Please forgive me if I'm wrong, as I have no formal physics training (apart from some in high school and personal reading), but there's something about Heisenberg's Uncertainty Principle that strikes ...
2
votes
1answer
254 views

Uncertainty on a single observable measurement

Heisenberg Uncertainty Principle states (in the form of the Robertson-Schroedinger Formula) that measurement of two non-commuting observables has a limiting precision, even for flawless measurement ...
0
votes
1answer
58 views

Velocity of measurement

As per to Heisenberg uncertainty we will not be able to calculate the position and momentum at same instant because by the time we calculate the next of the one, it changes (i.e.) the changes are very ...
1
vote
1answer
272 views

Experimental perspective in understanding the Heisenberg Uncertainty Principle

I need to confirm whether or not I understand Heisenberg Uncertainty Principle. So the crucial thing is that you need an "ensemble" of measurements: $$\delta x \delta p \ge \frac{\hbar}{2}.$$ If I ...