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David Knisely
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Reged: 04/19/04

Loc: southeastern Nebraska
Re: Schrodenger's cat new [Re: llanitedave]
      #5849234 - 05/09/13 03:03 AM Attachment (6 downloads)

I would hang old Schrodinger for the way he treated that cat! As for me, I long ago concluded that the photon is a particle whose behavior is dictated by the statistical probabilities given by quantum electrodynamics. In large numbers, statistically the distribution of photons does display some wave light properties, but individually (or in individual single-photon events), I consider them to be particles. That ended all my headaches about trying to make it into both a wave and a particle. Clear skies to you.

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dickbill
scholastic sledgehammer


Reged: 09/30/08

Re: Schrodenger's cat new [Re: David Knisely]
      #5849621 - 05/09/13 09:36 AM

Clear skies to you too, but that's not correct. Photons sent one by one towards the two slits will still produce an interference pattern on the projection screen. To do that, the single particle photon must have been through the two slits at the same time. Same thing for single electrons sent one by one to the slits, they will produce an interference pattern....as long you don't try to find out which slit they went through.

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jchaller
Pooh-Bah


Reged: 05/29/08

Loc: Tenino, WA.
Re: Schrodenger's cat new [Re: David Knisely]
      #5850001 - 05/09/13 01:01 PM

Looks like my cat - who prefers to sit on my lap when I have something better to do. He might disagree with me referring to him as "my cat".

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TL2101
professor emeritus


Reged: 09/17/10

Loc: Concord, Ca
Re: Schrodenger's cat new [Re: jchaller]
      #5850189 - 05/09/13 02:49 PM

Is it true that on the double slit that if the detectors are on but the data is never collected that you will get an interference pattern.

In other words it is the data not the detector collapsing the the wave?

If this is true (must be I read it on the Internet) its implications are mind bending.


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dickbill
scholastic sledgehammer


Reged: 09/30/08

Re: Schrodenger's cat new [Re: TL2101]
      #5850677 - 05/09/13 07:00 PM

No it's the detection. It also makes sense, or let's say it's not surprising, since to detect the photon or electron, you need to make it interact with something, like another photon.

But let's go ad absurdum again, if the quantum event could be entangled with a macroscopic system, first the geiger, then the cat, when or when would that stop?
There is no reason the entanglement would stop at the cat, the box should be entangled as well, then the outside observer and everything else that is causaly related. An infinite chain of observers is then absolutely necessary: You know the cat is alive because you watch him, but how do YOU know that YOU are alive? somebody must be watching you and so on...


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deSitter
Still in Old School


Reged: 12/09/04

Re: Schrodenger's cat new [Re: dickbill]
      #5850720 - 05/09/13 07:17 PM

dickbill, good point.

-drl


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TL2101
professor emeritus


Reged: 09/17/10

Loc: Concord, Ca
Re: Schrodenger's cat new [Re: dickbill]
      #5851134 - 05/09/13 11:20 PM

Quote:

No it's the detection. It also makes sense, or let's say it's not surprising, since to detect the photon or electron, you need to make it interact with something, like another photon.




That makes sense but what about the delayed choice experiment. Doesn't it hit a detector but is then erased showing an interference pattern?

The only reason I ask is there is a NASA physicist with a book that claims it is the act of knowing the data that collapses the wave function. He goes into quite a bit of detail about it.

Are all these physicists like Greene and others that write books for the general public a bunch of charlatans who can't be trusted? I am too old to learn physics so I have to trust someone for whats going on in the science community.

And why do physicists pick on cats? Shouldn't they use rats like other scientists?


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David Knisely
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Reged: 04/19/04

Loc: southeastern Nebraska
Re: Schrodenger's cat new [Re: dickbill]
      #5851324 - 05/10/13 03:38 AM Attachment (6 downloads)

Quote:

Clear skies to you too, but that's not correct. Photons sent one by one towards the two slits will still produce an interference pattern on the projection screen. To do that, the single particle photon must have been through the two slits at the same time. Same thing for single electrons sent one by one to the slits, they will produce an interference pattern....as long you don't try to find out which slit they went through.




Nope, a single photon sent towards a two slit setup will appear at a single location on the screen behind the slit, and not as a "pattern". The next photon sent through the 2-slit system will hit the screen behind the slits at a different location on the screen, and the next one after that at a still different location, and so on. If one keeps this up and keeps track of where each one hit the screen, eventually, you will see a banded distribution of photon locations on the screen which mimics the two-slit diffraction pattern seen for wave mechanics. This is the probability distribution for the two-slit experiment. If you have a whole huge stream of millions of photons going towards the screen, then the two slit diffraction pattern does appear, but for single photons, all you can see are single tiny impact spot locations and all you can calculate is the probability that a photon will hit a given location on the screen. More will hit certain locations than others, and if you do the statistics, the distribution of the photon impact locations looks just like the double slit pattern for wave mechanics. Clear skies to you.


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freestar8n
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Reged: 10/12/07

Re: Schrodenger's cat new [Re: David Knisely]
      #5851346 - 05/10/13 04:32 AM

I'm not sure how you get comfort viewing individual photons as "particles" when they don't follow ballistic trajectories. Those individual photons land in completely non-classical locations. The fact that individual locations behave according to the overall distribution expected from classical wave interference, and yet each one appears to "hit" at a single location, is what particle/wave duality is all about.

As for Schrodinger's cat - I view it as using words and analogies way outside the intended scope. A "particle in a box" with a separate observer "opening" it is an abstract and well defined concept - but a macroscopic cat in a macroscopic box with a macroscopic observer opening it is totally different. It is all a single system and there is no separation of the experiment from the observer and the observation. It's a single system "in a box" and there is no clear description of it that makes the observer distinct from the system being measured.

So if any conceptual paradoxes arise from pondering it - it doesn't really matter since it isn't following the rules of the game in the first place.

Frank


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Charlie B
scholastic sledgehammer


Reged: 03/22/08

Loc: Sterling, Virginia
Re: Schrodenger's cat new [Re: freestar8n]
      #5851605 - 05/10/13 09:14 AM

Two-slit experiment 2012!

I believe I would go with David on this point.

Charlie B


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dickbill
scholastic sledgehammer


Reged: 09/30/08

Re: Schrodenger's cat new [Re: Charlie B]
      #5851743 - 05/10/13 10:41 AM

David, i understand that there is a need to send more than one photon. The point here, it's impossible to say one photon interacts with another photon to create the distribution pattern. In the link that Charlie posted, the comment from 'Blueyes' about the 'quantum eraser' just add more to the weirdness of all that.
I am not a quantum physicist but this 'superimposition of states' can be worded in different ways, some more accurate than others, but in any cases, in the 'slit experiment' versus 'Schrodinger's cat', the 'cat' is more about the possibility of having a macroscopic system entangled by just using a macroscopic causal link with a quantum event. As I said above, I don't think it is possible, however, Penrose (yes, Roger Penrose)and Hamerhoff (a neurobiologist) suggest that the deep nature of the mind might be just that.
I quote Hameroff website: "In this (their) model, quantum-superposed states develop in microtubule subunit proteins ("tubulins"), remain coherent and recruit more superposed tubulins until a mass-time-energy threshold (related to quantum gravity) is reached".
I don't understand the quantum gravity point, and i don't think the 'tubulin' thing is a big deal, there is enough other stuff in a neurone that could potentially be in a quantum entanglement at a microscopic scale. But that's it, 'at a microscopic scale only' is my personnal opinion. For one, these molecules all interact with each other, which is like a measurement that will destroy any quantum effect.
But who knows, human consciousness is obviously very special, but can it be that special? does anyone has an interest in this issue? have a look:
http://www.quantumconsciousness.org/penrose-hameroff/consciousevents.html


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freestar8n
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Reged: 10/12/07

Re: Schrodenger's cat new [Re: Charlie B]
      #5851755 - 05/10/13 10:48 AM

I guess I'm not sure when anyone is saying. A single photon appears on the other side at a single point - sure - but that point has some arbitrary location that lets you know it was no ordinary particle following a ballistic trajectory through one or the other slit. It's something very weird and non particle-like.

You don't need to look at a whole bunch of them to know that individual ones hit in very non-particle locations.

Frank


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Pess
(Title)
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Reged: 09/12/07

Loc: Toledo, Ohio
Re: Schrodenger's cat new [Re: TL2101]
      #5851926 - 05/10/13 12:35 PM

Quote:



The only reason I ask is there is a NASA physicist with a book that claims it is the act of knowing the data that collapses the wave function. He goes into quite a bit of detail about it.





More accurately, it is the measurement itself that collapses the wave. For the case of the electron, in order to measure some aspect of it you have to force it to interact with your measuring tool (say another electron, photon, etc).

There are a couple collaries to quantrum functions that are equally as absurb (from a Newtonian viewpoint)

For example, for entangled particles they are said to collapse together despite being light years apart (measure one, the other is instantly at FTL existing in the opposite state.)

But you can never use entanglement for FTL communication because the observer stationed at particle #1 can never measure the state of particle #2 at anything but slower than FTL speeds.

Also consider the implications of quantum distribution. We all know about electron tunneling but it also follows that an electron orbiting that proton right in front of you can be found next to the proton (high probability) but there is also the probability that at any given moment that particular electron is on the other side of the galaxy (low probability). Highly improbably yes, but not statistically possible.

Which begs the age old question I have been posting here for years: What exactly defines a particles position in the Universe? What is it about a quark that, let's say puts it near Earth as opposed to an identical quark out around Pluto?

Is there some inherent coordinate system inside quarks that determines its position in time and space?

Pesse (And, more importantly, is that what powers the TARDIS??!) Mist


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Charlie B
scholastic sledgehammer


Reged: 03/22/08

Loc: Sterling, Virginia
Re: Schrodenger's cat new [Re: dickbill]
      #5853779 - 05/11/13 12:51 PM

The full article about the experiment is here.

You may want to read the full article about the experiment.

Regards,

Charlie B


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freestar8n
Post Laureate
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Reged: 10/12/07

Re: Schrodenger's cat new [Re: Charlie B]
      #5853876 - 05/11/13 02:08 PM

I view that article as making things even weirder than particle/wave duality. Even when you can in fact determine which slit a "particle" "went through" - it still can hit in a non ballistic and very wave-like location. It's bad enough - for a single particle - to hit in a non ballistic location when you have no idea which - or even both - slits it went through. But in this experiment you can get info on which slit it "went through" - and still a single hit can happen in a non ballistic - but very "interference wave" like location. Again all it takes is one hitting in a non-ballistic location to know they aren't normal particles - individually or collectively.

Frank


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HiggsBoson
Carpal Tunnel
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Reged: 02/21/07

Loc: Kal-li-fornia
Re: Schrodenger's cat new [Re: freestar8n]
      #5854485 - 05/11/13 10:20 PM

An amusing thread…

Two points:

When physicist refer to ‘particles’ they include those that have mass like the electron and those without mass such as the photon. The word does not imply a small object that has the characteristic of location or size. These are the characteristics of ‘classical particles’.

QM provides a description of photons, electrons and other ‘particles’ that have predictive value. These QM descriptions do not impose a requirement that they fit the classical definitions. Therefor the question is a photon a (classical) particle or a wave is obsolete. Our best description of a photon is silent on the question. The same is true for the electron. Both can exhibit behavior classically associated with classical particles and waves.


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CounterWeight
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Reged: 10/05/08

Loc: Palo alto, CA.
Re: Schrodenger's cat new [Re: HiggsBoson]
      #5854730 - 05/12/13 01:43 AM

Maybe the cat in the example is composed of instantons?

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freestar8n
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Reged: 10/12/07

Re: Schrodenger's cat new [Re: HiggsBoson]
      #5854805 - 05/12/13 03:53 AM

Quote:

Therefor the question is a photon a (classical) particle or a wave is obsolete.




Just to be clear - I'm not calling anything anything, except maybe "weird." Apparently at least some people in this thread want to view photons as individual particles that behave collectively as waves - and I don't understand the motivation.

I don't find quantum paradox talk very interesting because it's usually based just on words disconnected from the formalism. I think the paper mentioned does have a surprising result - but I don't see it helping give a "feel" for particle vs. wave.

All I can say about the cat is that it will be alive until the particle decays, and I have a sense for how long that will be based on the half life of the particle.

Frank


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llanitedave
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Reged: 09/26/05

Loc: Amargosa Valley, NV, USA
Re: Schrodenger's cat new [Re: freestar8n]
      #5855186 - 05/12/13 10:43 AM

What I want to know is, once the cat is dead can it be used to remove warts?

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TL2101
professor emeritus


Reged: 09/17/10

Loc: Concord, Ca
Re: Schrodenger's cat new [Re: llanitedave]
      #5855634 - 05/12/13 02:40 PM

All I can say is do not try this experiment at home!

I tried throwing my cat through one slit and then two. All I ended up with was one angry cat and interference scratches all over my body.


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