Can someone please explain quantum superposition?

[Hero of Pizza Time]

Hey,

I am curious about quantum physics and I heard this term "quantum superposition." After a bit of research, here is what I found:

• According to the principle, an object can be in multiple possible states until "observed"
• Light can behave as a particle or wave
• This has something to do with some sort of Heisenberg uncertainty principle
• This originated from a double slit experiment where electrons were shot at a wall with two slits. The screen behind the double slit wall seemed to be hit by the electrons in places that were covered by the wall, suggesting that electrons behaved as waves. The experiment was conducted again but this time with human observation and the electrons only went straight through the slits behaving like particles.

So I'm confused as to how human observation can change a particles behavior. I have tried googling it but I still can't really seem to understand it. It would be great if someone could explain this.

-Thanks

 

[YIGAhim]

I don't know much about this stuff, but I think that researching your question in a broad way won't get you quite the answers you want. Rather, I think you should try to understand each aprt by section until you can piece together the puzzle. For example, look up the double slit experiment on its own first, and also look up under which conditions light behaves as which and ect. It always helps me, but idk

 

[Spiritual Mask Salesman]

Schrödinger's cat explains this well, the experiment, basically, is a cat is placed within an enclosed box. It cannot be seen, or heard. So there are mutiple states, many different possibilities when the box is observered. Is there a cat inside at all? If there is, is it alive, or dead? All possibilities in the moment co-exist, and could be argued to all be valid, maybe even real. But once the box is finally opened, and the cat observered, only one outcome can be ascertained, and whatever the state of the cat is becomes the reality.

---

In the case of particles, they cannot be observed by humans without our presence causing a disturbence with the velocity of the particles. So pinpointing the exact postion of a particle is an impossibility. This is the Uncertainty Principle.

 

[TheGreatCthulhu]

Hey,

I am curious about quantum physics and I heard this term "quantum superposition." After a bit of research, here is what I found:

• According to the principle, an object can be in multiple possible states until "observed"
• Light can behave as a particle or wave
• This has something to do with some sort of Heisenberg uncertainty principle
• This originated from a double slit experiment where electrons were shot at a wall with two slits. The screen behind the double slit wall seemed to be hit by the electrons in places that were covered by the wall, suggesting that electrons behaved as waves. The experiment was conducted again but this time with human observation and the electrons only went straight through the slits behaving like particles.

So I'm confused as to how human observation can change a particles behavior. I have tried googling it but I still can't really seem to understand it. It would be great if someone could explain this.

-Thanks

I'm a student of physics, so I feel I can help you and others to get a practical, if simplistic, understanding of quantum mechanics.

First off, everyone misinterprets the superposition principle.

All it states is that since matter is quantized, separate possible quantum states can exist at the same time.

Say we have an electron. Say we want to find out which direction its spinning.

We can calculate a specific set of values for the electron spinning in a specific way, at a specific geometric angle, at a specified point in space and time, that we can say its spinning clockwise.

But if we imagine electrons as little balls of matter (they aren't, but go with that assumption for a moment), we can certainly say that electrons can spin counter-clockwise as well right?

Well, until we calculate the probability of the particle to be spinning in a specific direction, at a specific rate, in a specified geometric angle, at a specified point in space and time, we can't really say that all electrons spin clockwise right?

This is superposition, you can have an electron, until it is observed to do so at a specified point in space and time, to be spinning both clockwise, and counter-clockwise.

Here's a simpler way of looking at it. Say you're about to flip a coin right? If I ask you, "Heads or tails?" we both don't know if it could be heads or tails unless we flip the coin right? Thus, it can either be both heads and tails.

Thus, this explains Erwin Schrodinger's thought experiment. He used his thought experiment to demonstrate, using quantum physics, that a cat in a box can be both alive or dead, unless we open the box and observe the cat to be in either one of these possible states.

Now, onto the double slit experiment. This study has been so misunderstood, that quite frankly, I view this as a failure of the mainstream media to explain the results in a cogent, but easy to understand way. Sure, you can read the paper on the experiment, but sometimes they're difficult reads, especially when dealing with physics.

The result of the experiment was that photons behave as waves. But the mere act of observing caused the photons to behave like particles, or little balls of matter. However, when we're dealing with quantum mechanics, a study of the EXTREMELY SMALL, that means that observing the system is actually physically interacting with the system.

Quantum mechanical systems are very sensitive to any outside interaction.

Think of it like this, say you drop a dime in between the cushions of your car seats. Every time you try to grab the dime, it keeps moving itself deeper into the cushion right? That's analogous to the observation device interacting with the photons in that experiment.

I hope this helps. Quantum physics is one of the strongest fields of science, if not the strongest field of science, and it's a shame that some people don't have a basic grasp of its core concepts.

Hope this helped!

 

[Hero of Pizza Time]

I'm a student of physics, so I feel I can help you and others to get a practical, if simplistic, understanding of quantum mechanics.

First off, everyone misinterprets the superposition principle.

All it states is that since matter is quantized, separate possible quantum states can exist at the same time.

Say we have an electron. Say we want to find out which direction its spinning.

We can calculate a specific set of values for the electron spinning in a specific way, at a specific geometric angle, at a specified point in space and time, that we can say its spinning clockwise.

But if we imagine electrons as little balls of matter (they aren't, but go with that assumption for a moment), we can certainly say that electrons can spin counter-clockwise as well right?

Well, until we calculate the probability of the particle to be spinning in a specific direction, at a specific rate, in a specified geometric angle, at a specified point in space and time, we can't really say that all electrons spin clockwise right?

This is superposition, you can have an electron, until it is observed to do so at a specified point in space and time, to be spinning both clockwise, and counter-clockwise.

Here's a simpler way of looking at it. Say you're about to flip a coin right? If I ask you, "Heads or tails?" we both don't know if it could be heads or tails unless we flip the coin right? Thus, it can either be both heads and tails.

Thus, this explains Erwin Schrodinger's thought experiment. He used his thought experiment to demonstrate, using quantum physics, that a cat in a box can be both alive or dead, unless we open the box and observe the cat to be in either one of these possible states.

Now, onto the double slit experiment. This study has been so misunderstood, that quite frankly, I view this as a failure of the mainstream media to explain the results in a cogent, but easy to understand way. Sure, you can read the paper on the experiment, but sometimes they're difficult reads, especially when dealing with physics.

The result of the experiment was that photons behave as waves. But the mere act of observing caused the photons to behave like particles, or little balls of matter. However, when we're dealing with quantum mechanics, a study of the EXTREMELY SMALL, that means that observing the system is actually physically interacting with the system.

Quantum mechanical systems are very sensitive to any outside interaction.

Think of it like this, say you drop a dime in between the cushions of your car seats. Every time you try to grab the dime, it keeps moving itself deeper into the cushion right? That's analogous to the observation device interacting with the photons in that experiment.

I hope this helps. Quantum physics is one of the strongest fields of science, if not the strongest field of science, and it's a shame that some people don't have a basic grasp of its core concepts.

Hope this helped!

So I have heard that the best way to illustrate electrons is as a "probability cloud" around the nucleus because the electrons are constantly moving, but we can still calculate the probability of where it will be and how often it will be where it is. However, the electron, technically speaking, is really just at one place at one time, even if we can act as if it is in multiple places at the same time.

Is this basically the same principle as quantum superposition? Because this would mean that an object can technically only be in one place at a time, but the uncertainty of that state can be represented as the object being in both states until it is measured. That would mean that this principle is more of a tool for scientists rather than an objective law of the universe.

 

[TheGreatCthulhu]

So I have heard that the best way to illustrate electrons is as a "probability cloud" around the nucleus because the electrons are constantly moving, but we can still calculate the probability of where it will be and how often it will be where it is. However, the electron, technically speaking, is really just at one place at one time, even if we can act as if it is in multiple places at the same time.

Is this basically the same principle as quantum superposition? Because this would mean that an object can technically only be in one place at a time, but the uncertainty of that state can be represented as the object being in both states until it is measured. That would mean that this principle is more of a tool for scientists rather than an objective law of the universe.

Not necessarily the same thing. You're thinking of the Heisenberg Uncertainty Principle. Superposition is a bit different.

And regarding it being a tool rather than an objective law. It's both.

 

[Hero of Pizza Time]

Not necessarily the same thing. You're thinking of the Heisenberg Uncertainty Principle. Superposition is a bit different.

And regarding it being a tool rather than an objective law. It's both.

So then something can actually be in two opposite states at once?

 

[TheGreatCthulhu]

So then something can actually be in two opposite states at once?

That's not the right way of looking at it. The fundamental problem most people have is that they want to be able to look at the world and see it for what it is. But there's a fundamental principle in quantum physics that says what you observe an electron doing is not how the electron actually is in reality, if that makes sense.

So rather than pointing to a point in space and time, and saying, "Here's the electron, here's its charge, its velocity, and so on," it's more of a sense of, "If I look at this point in space and time, what's the probability of the electron being there?"

So that brings us back to the coin flip analogy. We have a coin that can be heads or tails, but we can't 100% say for sure if it'll be heads or tails unless we flip the coin. Thus, the coin exists in superposition of heads and tails.

 

[Hero of Pizza Time]

That's not the right way of looking at it. The fundamental problem most people have is that they want to be able to look at the world and see it for what it is. But there's a fundamental principle in quantum physics that says what you observe an electron doing is not how the electron actually is in reality, if that makes sense.

So rather than pointing to a point in space and time, and saying, "Here's the electron, here's its charge, its velocity, and so on," it's more of a sense of, "If I look at this point in space and time, what's the probability of the electron being there?"

So that brings us back to the coin flip analogy. We have a coin that can be heads or tails, but we can't 100% say for sure if it'll be heads or tails unless we flip the coin. Thus, the coin exists in superposition of heads and tails.

So quantum superposition is basically the state of something (like a measurement or a property) being undetermined?

 

[TheGreatCthulhu]

So quantum superposition is basically the state of something (like a measurement or a property) being undetermined?

That's a better way of looking at it. It's not magic, but it's the principle with which to look at subatomic particles.

There's more nuance that the mathematics shows, of course, but you got the whole gist of it.

Edit: On top of this, the reason why this works, is because of wave-particle duality. Basically that the electron as it is, is a wave, but the second you try to observe where it is, it collapses that wave function. Say you have an electron that exists in superposition spinning both clockwise and counter-clockwise, and you want to observe which direction it's spinning. The second you observe the electron, that collapses to showing you either clockwise or counter-clockwise, not both.

That's purely due to how probability and wave functions work in mathematics, it ain't magic, like some out there would say.