How can something be in two places at once?

[New Scientist]

I have just read the article here: http://www.technologyreview.com/Infotech/21086/?a=f about researchers being able to control the position of a single electron in a silicon circuit.

I'm no scientist and my knowledge of quantum mechanics is laughable but I am a keen albeit frequently perplexed enthusiast. My puzzlement is when the article states that "the electron [was] in two places at once". I can't conceive how something can be in two places at once. Surely if there was an electron in one place and then a counterpart appeared somewhere else, the original electron is the one that hasn't moved from it's original position and the newcomer in a different location is merely a copy?

For something to be a different entity it surely requires that the entity is both:
- in another location (i.e. not sharing the space of another entity), and
- of itself (i.e. not part of the same matter of another entity)

Why is it the case that this '2nd' electron is not applicable to this definition?

Thank you for any replies and apologies if I have made any glaring errors.

p.s. I've posted this here because it seems to be moderated more frequently than the Science board.

[Tigger]

Quoting New Scientist from 16:59, 26th Jul 2008
I have just read the article here: http://www.technologyreview.com/Infotech/21086/?a=f about researchers being able to control the position of a single electron in a silicon circuit.

I'm no scientist and my knowledge of quantum mechanics is laughable but I am a keen albeit frequently perplexed enthusiast. My puzzlement is when the article states that "the electron [was] in two places at once". I can't conceive how something can be in two places at once. Surely if there was an electron in one place and then a counterpart appeared somewhere else, the original electron is the one that hasn't moved from it's original position and the newcomer in a different location is merely a copy?

For something to be a different entity it surely requires that the entity is both:
- in another location (i.e. not sharing the space of another entity), and
- of itself (i.e. not part of the same matter of another entity)

Why is it the case that this '2nd' electron is not applicable to this definition?

Thank you for any replies and apologies if I have made any glaring errors.

p.s. I've posted this here because it seems to be moderated more frequently than the Science board.

Well, to put your mind at rest, firstly, its an arsenic atom, with, and i quote, "an electron that’s in two distinct quantum states at the same time". Technically, twoplaces at the same time, just badly worded. secondly, its science, being that they have to make it look good, as making hamsters sick with a specific number of chocolate buttons is obviously not getting enought grant sponsorship.

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(Claire Raynor)

[d_24]

Quoting Tigger from 20:37, 26th Jul 2008
Well, to put your mind at rest, firstly, its an arsenic atom, with, and i quote, "an electron that’s in two distinct quantum states at the same time". Technically, twoplaces at the same time, just badly worded. secondly, its science, being that they have to make it look good, as making hamsters sick with a specific number of chocolate buttons is obviously not getting enought grant sponsorship.

If it's technically two places at the same time and the OP said two places at the same time then you're not really making anything clearer.

And you just flat out lost me with the hamsters gibberish.

[hr]

Before Bauer...There Was House

[Frank]

Right, my explanation might be off*, but hopefully the job's a good 'un.

The quantum states aren't 'two places at once' as much as 'equal probability of being in either state at once'. It is surely a superposition of the quantum states meaning that, as said before, the electron has exactly the same likelyhood of being in one place as the other. Quite how that unfolds and is achieved is...vague in the article and I'm unable to research it further.

The devil, as always, is in the details. And, when you say something in physics (like any science) there's a huge background behind what's actually meant. If you're not clear, acquainted or simply familiar with the terminology it is very to get lost amongst it. I'd also say, however, that the OP's linked article isn't the best research review I've ever read.

Given the quality of some of the review articles I saw in my third year, I'm surprised to learn the authors'a graduate science writer. It really is a bit...unclear. (That said many of the review articles circulated around our level, my own included, fall short again on clarity for 'out of field' readers)


* Superhands. A game, the cousin of Edward Ciderhands, wherein you tape two cans of Tenants Super to your hands.

[hr]

"There is only ever one truth. Things are always black or white, there's no such thing as a shade of grey. If you think that something is a shade of grey it simply means that you don't fully understand the situation. The truth is narrow and the path of the pursuit of truth is similarly narrow."
Also, some years later:
"here we are arguing about a few uppity troublemakers with a bee in their bonnet and a conspiracy theory."

[Guest]

if the atom is equally likely to be in one place as another, is this evidence of the existence of parallel unvierses? because the position cannot be exactly pinpointed it is possible that it is existing within another universe aswell as ours

[Lid]

Quoting from 22:46, 28th Jul 2008
if the atom

It's the electron that we've been talking about, not the atom, and its associated quantum waveform. It we suddenly started talking about an atom, even in Hydrogen, we'd have to factor in a proton, which is about 1800 times more massive and would greatly alter some stuff, or something. Semantics, probably.

The problem arises insofar as if you try to measure the position, the waveform collapses and you can't measure momentum, so for a given point, you might know where it is, but not where it's going, and how quickly. Or something like that anyway, I did my best to ignore this newfangled quantum in my 3 years.

[hr]

Mathematical Anti Telharsic Harfatum Septomin

[Guest]

Reading through all this...I can't really find an answer to the OP's question.

[Haunted]

The only question I see in OP is "is this other electron a copy?"

No, because it's not another electron it's the same one it just hasn't been spacially confined/defined very well. Single particles can exist in multiple places, thats just QM, it's counter-intuitive.
The problem is with the human imagination (or lack of in thise case), electrons are not billiard balls that bounce around in white sea of other billiard balls.

[hr]

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[Guest]

So quoting the language used above, an 'entity' made of matter can't take up the same space as something else but subatomic particles like electrons are, on a quantum level, a 'waveform' and can.

Does this have anything to do with mass? Such that things that don't have mass can't take up space?

[FuzzyBeans]

Quoting from 22:25, 31st Jul 2008
So quoting the language used above, an 'entity' made of matter can't take up the same space as something else but subatomic particles like electrons are, on a quantum level, a 'waveform' and can.

Does this have anything to do with mass? Such that things that don't have mass can't take up space?

Does this question make sense to anyone else?

An electron does have mass, 1.6x10^-19 kg to be exact. It also has an 'associated' wave function which is basically just a theory, not a real wave. The wave function allows the possibility of the electron being in 2 places at once, or 2 distinct states. The problem arises when you want to actually find out which state it is in, ie, make a measurement. If you make a measurement the wavefunction collapses, ie, you get one state with a born probability. Its called a collapse because all the other possible states 'collapse' into nothing.

Does this answer the confusing question? Im confused. Quantum Mechanics is not for the faint hearted.......

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[Haunted]

Quoting from 22:25, 31st Jul 2008
So quoting the language used above, an 'entity' made of matter can't take up the same space as something else but subatomic particles like electrons are, on a quantum level, a 'waveform' and can.

Does this have anything to do with mass? Such that things that don't have mass can't take up space?

Macroscopic objects also have an associated wavefunction. There's a small chance you could be in multiple states at the same and there's a small chance you could quantum tunnel your way through a wall.

[hr]

Now with 100% more corn

[Power Metal Dom]

Sounds to me, from what's been said, like the theory asserts something can be in 2 places at once without actually explaining how that's possible. It's all very well saying 'Oh well the wave function allows a physical object to be in two places at once or at least has the liklihood of being in two places at once' but that still doesn't really explain the OP's question which seems to ask how can two physical objects, however small, take up same point in space.

Also, to add another healthy dose of confusion, how can something have two different states at once? Doesn't that present the same sort of problem?

[hr]

Like flames on fuel...upon metal I drool

[Haunted]

Quoting Power_Metal_Dom from 12:32, 7th Aug 2008
Sounds to me, from what's been said, like the theory asserts something can be in 2 places at once without actually explaining how that's possible. It's all very well saying 'Oh well the wave function allows a physical object to be in two places at once or at least has the liklihood of being in two places at once' but that still doesn't really explain the OP's question which seems to ask how can two physical objects, however small, take up same point in space.

http://en.wikipedia.org/wiki/Wave-particle_duality
http://en.wikipedia.org/wiki/Uncertainty_principle
http://en.wikipedia.org/wiki/Quantum_superposition
http://en.wikipedia.org/wiki/Copenhagen_interpretation
http://en.wikipedia.org/wiki/EPR_paradox

Why is red red? If you keep asking why questions you will eventually come across a "just because" answer.

[hr]

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[MaverickMenzies]

Quantum mechanics does not say particles can occupy two spatial locations simultaneously. What it says is:

1) Electrons and other "particles" can exist as delocalised waves over a given spatial volume.

2) The act of measuring the "position" creates a definite spatial location of the particle. Prior to the measurement, the electron has no unique position i.e. its delocalised.

Ultimately, this behaviour occurs as a result of seperating observable quantities of a system from the state of the system. In classical physics, the two amount to the same thing. Not so in quantum theory. So, for example, an electron can be in a state which does not actually have a well-defined spatial location.

[Humphrey]

Quoting Power_Metal_Dom from 12:32, 7th Aug 2008
Sounds to me, from what's been said, like the theory asserts something can be in 2 places at once without actually explaining how that's possible. It's all very well saying 'Oh well the wave function allows a physical object to be in two places at once or at least has the liklihood of being in two places at once' but that still doesn't really explain the OP's question which seems to ask how can two physical objects, however small, take up same point in space.

Also, to add another healthy dose of confusion, how can something have two different states at once? Doesn't that present the same sort of problem?

[hr]

Like flames on fuel...upon metal I drool

Its pretty confusing and counter-intuitive. Here's a consolation though, if Quantum mechanics didn't happen to work in that way you wouldn't be around to ask these questions; so be glad the world of the small makes no sense.

[hr]

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http://www.livejournal.com/users/humphrey_clarke/

[Power Metal Dom]

Quoting Haunted from 12:48, 7th Aug 2008

Quoting Power_Metal_Dom from 12:32, 7th Aug 2008
Sounds to me, from what's been said, like the theory asserts something can be in 2 places at once without actually explaining how that's possible. It's all very well saying 'Oh well the wave function allows a physical object to be in two places at once or at least has the liklihood of being in two places at once' but that still doesn't really explain the OP's question which seems to ask how can two physical objects, however small, take up same point in space.

http://en.wikipedia.org/wiki/Wave-particle_duality
http://en.wikipedia.org/wiki/Uncertainty_principle
http://en.wikipedia.org/wiki/Quantum_superposition
http://en.wikipedia.org/wiki/Copenhagen_interpretation
http://en.wikipedia.org/wiki/EPR_paradox

Why is red red? If you keep asking why questions you will eventually come across a "just because" answer.

1. Wiki links
2. Just because.

Haha! Spoken like a true Sinner. Philosophy likes the "erm, because it is" answer too, same with the "just run with it cos it fits my theory nicely" answer (though the question of why red is red is at least answerable). It is a little unnerving that our understanding of a lot of things rests on things that do not actually make sense; hence why no one can give a satisfying answer to the OP. For example:

Quoting MaverickMenzies from 13:42, 7th Aug 2008
2) The act of measuring the "position" creates a definite spatial location of the particle. Prior to the measurement, the electron has no unique position i.e. its delocalised.

Doesn't this just raise the impossibility of something existing but not having a position?

[hr]

Like flames on fuel...upon metal I drool

[Frank]

Quoting Power_Metal_Dom from 19:18, 7th Aug 2008
Doesn't this just raise the impossibility of something existing but not having a position?

[hr]

"There is only ever one truth. Things are always black or white, there's no such thing as a shade of grey. If you think that something is a shade of grey it simply means that you don't fully understand the situation. The truth is narrow and the path of the pursuit of truth is similarly narrow."
Also, some years later:
"here we are arguing about a few uppity troublemakers with a bee in their bonnet and a conspiracy theory."

[LonelyPilgrim]

Perhaps I can answer the OP's question.

An electron can only be in one place at a given time. The problem arises because we can not observe the electron in that place without changing its behaviour, and hence, its place. So, for purposes of calculation, the electron has a probability of being in several given places at any given time. It is really in only one of those places, but we have no way of knowing which one so we treat it as though it is in all of them.

That's incredibly simplified, and no doubt a physicist would take issue, but it is the easiest 'lie we tell to children' that can explain the problem you raise. Just reassure yourself that it is a theoretical model used to perform calculations and it isn't 'real', it is merely useful.

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Man is free; yet we must not suppose that he is at liberty to do everything he pleases, for he becomes a slave the moment he allows his actions to be ruled by passion. --Giacomo Casanova

[MaverickMenzies]

Quoting Power_Metal_Dom from 19:18, 7th Aug 2008
Doesn't this just raise the impossibility of something existing but not having a position?

No. What is the position of a wave? Position is need not be a fundamental quantity associated to objects.

[Power Metal Dom]

Quoting LonelyPilgrim from 08:57, 8th Aug 2008
Perhaps I can answer the OP's question.

An electron can only be in one place at a given time. The problem arises because we can not observe the electron in that place without changing its behaviour, and hence, its place. So, for purposes of calculation, the electron has a probability of being in several given places at any given time. It is really in only one of those places, but we have no way of knowing which one so we treat it as though it is in all of them.

That's incredibly simplified, and no doubt a physicist would take issue, but it is the easiest 'lie we tell to children' that can explain the problem you raise. Just reassure yourself that it is a theoretical model used to perform calculations and it isn't 'real', it is merely useful.

That makes sense to me! Another great post from LP.

Quoting MaverickMenzies from 12:48, 8th Aug 2008
Position is need not be a fundamental quantity associated to objects.

If so then can you give an instance of when an object does not have a spatial location?

[hr]

Like flames on fuel...upon metal I drool