Wave-particle duality question

In summary, this person is asking about the EPR paradox and wave-particle duality. They state that if you measure momentum and position, the latter cannot be accurately determined. This is because you need to measure the particle in an approximate eigenstate of the momentum operator first. If you reverse the order, you will end up screwing up the momentum and get the Heisenberg limit. Interestingly, if you measure momentum and position at the same time, the Heisenberg uncertainty principle does apply.
  • #1
autonomous
4
0
i was wondering, what if you shined two parallel rays of light directly next to each other and shot the particle throught them, one being a short wavelength and the other a long wavelength and measured each one. the first ray of light would find the momentum, so when u found the position you could already know its momentum. would this be accurate, considering the speed of the particle is constant?
 
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  • #2
if you untirely understand what I am saying, its basically to help find a particles position and momentum, sense the whole wave-particle duality is about how its impossible to find both because once you find one you now no less of the other. a shorter wave length will help you find the position, and the longer wave length helps you find the momentum, or maybe its the other way around, but this is what I've read, and no one has ever tried doing both so i figured it may be possible. just read up on the 'wave-particle duality' and you will know more of what my earlier post is asking.
 
  • #3
autonomous said:
if you untirely understand what I am saying, its basically to help find a particles position and momentum, sense the whole wave-particle duality is about how its impossible to find both because once you find one you now no less of the other. a shorter wave length will help you find the position, and the longer wave length helps you find the momentum, or maybe its the other way around, but this is what I've read, and no one has ever tried doing both so i figured it may be possible. just read up on the 'wave-particle duality' and you will know more of what my earlier post is asking.

Search and read up on the EPR paradox, you might be enlightened to know that you weren't the first one to propose the collapse of the uncertainty principle.
 
  • #4
autonomous said:
i was wondering, what if you shined two parallel rays of light directly next to each other and shot the particle through them, one being a short wavelength and the other a long wavelength and measured each one. the first ray of light would find the momentum, so when u found the position you could already know its momentum. would this be accurate, considering the speed of the particle is constant?

For your plan to work, you're going to have to measure momentum first, then position. Clearly if you reversed the order, you'd end up screwing up the momentum and get the Heisenberg limit.

So your question really comes down to this. When you make a measurement of momentum, does it also screw up later measurements of position?

The answer is that it does. In QM, to make an accurate measurement of momentum requires that the particle be placed in an approximate eigenstate of the momentum operator. The math then shows that its position cannot be accurately determined.

By the way, the EPR experiment involves correlated particles being measured, one for momentum, the other for position. In your case, you only have one particle, so the Heisenberg uncertainty principle does, in fact, apply.

Carl
 
  • #5
The discussion here is quite complete.

https://www.physicsforums.com/showthread.php?t=78949

In QM, to make an accurate measurement of momentum requires that the particle be placed in an approximate eigenstate of the momentum operator. The math then shows that its position cannot be accurately determined.

To be even clearer, it won't have a localised position in the classical sense
which is subject to discovery. But it will acquire one if and when a position
measurement is made.

I use the funny verbiage "subject to discovery" because in english the
word "determine" has two meanings and is the source of much confusion
on this topic.
 
  • #6
It is interesting to note that if you perform one masurement you may find experimental results for position and momentum with as high precision as you want.
The HUP enters the discussion when you try to associate these values of position and momentum to a certain time, a certain initial state and a certain set of physical influences (Hamiltonian). By doing a set of identical experiments you will find statistical dispersion on these results, and it is exactly at this point that HUP appears, if I understood it well.

Best Regards

DaTario
 

1. What is wave-particle duality?

Wave-particle duality is a concept in physics that states that particles, such as electrons and photons, can exhibit both wave-like and particle-like behavior.

2. How was wave-particle duality discovered?

Wave-particle duality was first observed in experiments with light by Thomas Young in the early 1800s. Later, in the early 1900s, scientists such as Max Planck and Albert Einstein further developed the concept through their work on the photoelectric effect and quantum mechanics.

3. What evidence supports wave-particle duality?

One of the key pieces of evidence for wave-particle duality is the double-slit experiment, where a single particle is passed through two slits and creates an interference pattern, much like a wave would. Additionally, experiments such as the photoelectric effect and diffraction of electrons further support the concept of wave-particle duality.

4. How does wave-particle duality impact our understanding of the world?

The concept of wave-particle duality has revolutionized our understanding of the world, particularly in the fields of quantum mechanics and particle physics. It has also led to the development of important technologies, such as transistors and lasers.

5. Is wave-particle duality still a topic of debate in the scientific community?

While the concept of wave-particle duality is widely accepted in the scientific community, there are still ongoing debates and discussions about its implications and how it fits into our understanding of the universe. New experiments and discoveries continue to shed light on this complex and fascinating concept.

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