Uncertainty principle and angular momentum

In summary, the uncertainty principle in quantum mechanics states that any two Hermitian operators that do not commute with each other cannot be simultaneously diagonalized, leading to a non-zero commutator and the inability to measure both eigenvalues with arbitrary precision. This principle applies to \Delta{x}\Delta{p}, \Delta{E}\Delta{t}, and particle spin, all of which have units of angular momentum and the ability to be quite uncertain. However, it is important to note that while \Delta{x}\Delta{p} and particle spin are operators in QM, \Delta{E}\Delta{t} are not, and therefore do not have the same kind of uncertainty relation.
  • #1
Upisoft
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[itex]\Delta{x}\Delta{p}[/itex], [itex]\Delta{E}\Delta{t}[/itex] and particle spin all have units of angular momentum and have ability to be quit uncertain... Any idea if they have something in common (except the units of measurement)?
 
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  • #2
Upisoft said:
[itex]\Delta{x}\Delta{p}[/itex], [itex]\Delta{E}\Delta{t}[/itex] and particle spin all have units of angular momentum and have ability to be quit uncertain... Any idea if they have something in common (except the units of measurement)?

Before I try to answer the question, one correction is in order. Yes, the uncertainty principle states that [itex]\Delta{x}\Delta{p} <= h/2[/itex], but the same kind of statement does not come from QM (at least not directly) for [itex]\Delta{E}\Delta{t}[/itex]. This is because X and P are are operators in QM, but E and t are not. E and t are real valued parameters.

OK, back to the uncertainty: in QM, any two Hermitian operators which do not commute with each other cannot be simultaneously diagonalized. Translated into plain English, this says that the eigenvalues of the two operators cannot be measured with arbitrary precision without affecting the other's eigenvalues. All uncertainty relations in QM have this feature in common: there is an underlying non-zero commutator for the two operators in question. If on the other hand, you have two commuting operators, then you can measure both of them with arbitrary precision without affecting the other, and there is no corresponding uncertainty relation for them.
 

FAQ: Uncertainty principle and angular momentum

1. What is the Uncertainty Principle?

The Uncertainty Principle, also known as Heisenberg's Uncertainty Principle, is a fundamental concept in quantum mechanics that states that it is impossible to know both the exact position and momentum of a particle at the same time. This principle is a result of the wave-particle duality of matter, which states that particles can exhibit both wave-like and particle-like behavior.

2. How does the Uncertainty Principle relate to angular momentum?

The Uncertainty Principle also applies to angular momentum, which is a measure of the rotational momentum of a particle. This means that it is impossible to know both the exact angular position and angular momentum of a particle at the same time. This is because measuring one property with high accuracy will cause the other property to become more uncertain.

3. What is the mathematical expression for the Uncertainty Principle?

The Uncertainty Principle is mathematically expressed as ΔxΔp ≥ ħ/2, where Δx represents the uncertainty in position, Δp represents the uncertainty in momentum, and ħ is the reduced Planck's constant. This means that the product of the uncertainties in position and momentum must be greater than or equal to half of the reduced Planck's constant.

4. How does the Uncertainty Principle impact our ability to measure particles?

The Uncertainty Principle places a fundamental limit on our ability to measure particles. This means that there will always be a degree of uncertainty in our measurements, and we can never know the exact properties of a particle. However, this does not mean that we cannot make accurate predictions about the behavior of particles, as quantum mechanics allows us to make statistical predictions based on the probabilities of different outcomes.

5. Can the Uncertainty Principle be violated?

No, the Uncertainty Principle is a fundamental principle in quantum mechanics and has been extensively tested and validated through experiments. It is a fundamental aspect of the behavior of particles and cannot be violated. However, there are certain situations where the uncertainty in one property can be reduced at the expense of increasing the uncertainty in another property, but the overall uncertainty remains the same.

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