DebateGate
General Category => 3DHS => Topic started by: Amianthus on July 22, 2010, 04:14:25 PM
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19:00 22 July 2010 by David Shiga
It is one of the all-time greatest physics experiments: such a classic that it's taken a century to go one better.
In the double-slit experiment of 1908, a photon fired at a pair of slits passed through both simultaneously and interfered with itself. This surprising effect provided one of the first clues to the weird world of quantum mechanics.
Now precise measurements have been made on a version with three slits - and they again confirm the predictions of quantum mechanics.
Why are we still testing such predictions? It is not just tilting at windmills: physicists have long struggled to unite quantum mechanics with general relativity, which describes gravity, and some believe quantum mechanics will need tweaking to make this work.
Those tweaks, some physicists have argued, might include altering a quantum dictum called Born's rule. It predicts that interference patterns from three or more slits is equivalent to combining the effects of several double-slit experiments.
But although it is easy to add a third slit to the double-slit experiment, it has been more challenging to do it in a way that allows the precise measurements needed to check the validity of quantum mechanics.
"The experiment is much harder than it might seem," says James Franson of the University of Maryland, Baltimore County, who was not involved in the study. "The slightest misalignment of the slits might produce errors."
Urbasi Sinha of the University of Waterloo in Ontario, Canada, and colleagues managed to do it by carving into a metal coating on a glass plate to make three equally spaced transparent slits, 30 micrometres wide and 100 micrometres apart. Then they used a laser to fire photons one at a time at the plate and recorded the pattern of light on the other side.
The result was a wavy interference pattern that matched the predictions of Born's rule to within the experiment's error margin of 1 per cent.
Franson says it is important to check for deviations from what theory predicts, even though the results were unsurprising in this case. "People tend to take things for granted, but physics is an experimental science and we should test these things," he says.
Journal reference: Science, DOI: 10.1126/science.1190545
Original Article (http://www.newscientist.com/article/dn19215-tripleslit-experiment-confirms-reality-is-quantum.html)
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I think you hit the wrong keys, this forum isn't the nerd forum. If I may speak for the group, we'd rather watch paint dry than discuss slit experiments. BORING!
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I was just wondering if the slits could be made adjustable.
Cutting them at these precice measurements was so difficult , I would have cut them on three diffrent plates and attached them to a micrometer type screw movement.
Rather than machineing them at such a fine measurement they could have been gradually been moved untill the difraction pattern appeared and then measured.
Have you ever seen optical flats used?
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I think you hit the wrong keys, this forum isn't the nerd forum. If I may speak for the group, we'd rather watch paint dry than discuss slit experiments. BORING!
You only speak for the less intelligent members of the forum.
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I think you hit the wrong keys, this forum isn't the nerd forum. If I may speak for the group, we'd rather watch paint dry than discuss slit experiments. BORING!
You only speak for the less intelligent members of the forum.
sorry I hurt your feelings
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sorry I hurt your feelings
Your pathetic jabs don't bother me. I was just correcting your arrogance.
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sorry I hurt your feelings
Your pathetic jabs don't bother me. I was just correcting your arrogance.
like I said sorry for hurting your feelings
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like I said sorry for hurting your feelings
Sorry for putting you in your place.
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like I said sorry for hurting your feelings
Sorry for putting you in your place.
yawn
you and and your Triple-slit experiment are boring. Plane liked it though so don't feel too bad.
Do you have an assortment of pocket protectors? Something tells me that you have a secret lab in your basement where all your experiments take place -- tell me it ain't so, please please please say it ain't so!
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actually i wear a pocket protector, pens tend to explode alot with me & I do wear horn rimed glasses. but thats only because thier alot more comfortable than the wire frames. but unfortunately I`m also a intimidating guy. it works very well at my guard job.
I like it when we have some hard science here, I used to be a astro-physics major.
not a problem
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actually i wear a pocket protector, pens tend to explode alot with me & I do wear horn rimed glasses. but thats only because thier alot more comfortable than the wire frames. but unfortunately I`m also a intimidating guy. it works very well at my guard job.
I like it when we have some hard science here, I used to be a astro-physics major.
not a problem
I hear ya kimba, I was just a little disappointed because when I first read the title I got kinda excited thinking it was a story about 3 twenty year old chicks (a red head, blond & brunette) and Tiger woods in a hotel room in Vegas.
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If I may speak for the group
No, you may not.
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If I may speak for the group
No, you may not.
damn, when I said that you never crossed my mind.
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I'm sure a lot of things didn't cross your mind.
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I'm sure a lot of things didn't cross your mind.
well no doubt what didn't cross my mind probably crossed yours.
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All things considered, that's saying quite a lot.
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http://physicsworld.com/cws/article/news/43275 (http://physicsworld.com/cws/article/news/43275)
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All things considered, that's saying quite a lot.
well, since you are the universal prince everything crosses your mind.
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you and and your Triple-slit experiment are boring. Plane liked it though so don't feel too bad.
Yes, I understand that a lack of intelligence makes the story seem boring. However, those of us with normal or better levels of intelligence find it interesting.
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you and and your Triple-slit experiment are boring. Plane liked it though so don't feel too bad.
Yes, I understand that a lack of intelligence makes the story seem boring. However, those of us with normal or better levels of intelligence find it interesting.
You have a fixation on intelligence going way back. Is there something in your past that keeps bringing up this word in so many of your posts or is this just a typical and boring response, because you have nothing else in your ammo bag? Is this 'intelligence' thing a deep seated childhood scar or wound that keeps rearing its ugly head revealing something sinister and ugly about a past event in your life? Did someone in your early life taunt or keep telling you that you were dumb or not smart enough? I find that both you and XO seem to use this (dumb label) as your #1 insult. Have you ever considered adding other insults to your repertoire or do you plan on using the generic 'you are dumb' line all the time? It certainly would be more entertaining being more creative with your insults or shall I say childish retorts. Or is creativity lacking in your so-called superior intelligence? Are you one of those really brainy guys that lack common sense? I find it odd that you have taken this triple slit experiment thing so personal, why? What is your investment? Just because the subject is as boring as watching paint dry (to most people) shouldn't curb your enthusiasm. By all means have a good time delving deeper and deeper into the subject. No doubt I'm wrong and you are right that most people are just fascinated by this subject. In his next SOTUA Obama should devote at least 5,000 words to the subject. The experiment is so interesting that I bet there are forums that go on and on about the subject. Don't let my lack of appreciation pop your bubble or spoil you party. By all means keep having fun with it. I just have one question though: I assume you are pretty familiar with the Double Slit Experiment that shows photons behaving as waves and or particles? Well I was wondering if a Triple Slit experiment had ever been tried or theorized about. It's well known that detecting a photon passing through one of two paths will cause the probability waveform to collapse in a Double Slit Experiment and show that photon behaving as a particle, but what would be the effect of monitoring one possible path in a triple slit experiment? Detecting the photon passing along the monitored path would obviously result in it behaving as a particle, but not detecting it would result in it having an equal probability of passing along either of the other two paths to the detector screen, would you end up with an experiment that showed a photon behaving as both a particle and a wave all in one experiment, or would the detecting device in one of the three paths result in every photon showing particle properties?
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Most creative people find science interesting. I'm sorry you don't have the creativity to see it.
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I just have one question though: I assume you are pretty familiar with the Double Slit Experiment that shows photons behaving as waves and or particles? Well I was wondering if a Triple Slit experiment had ever been tried or theorized about. It's well known that detecting a photon passing through one of two paths will cause the probability waveform to collapse in a Double Slit Experiment and show that photon behaving as a particle, but what would be the effect of monitoring one possible path in a triple slit experiment? Detecting the photon passing along the monitored path would obviously result in it behaving as a particle, but not detecting it would result in it having an equal probability of passing along either of the other two paths to the detector screen, would you end up with an experiment that showed a photon behaving as both a particle and a wave all in one experiment, or would the detecting device in one of the three paths result in every photon showing particle properties?
I assume from this question that you read neither the article nor Plane's response. This article is about the results of a team *conducting* the triple split experiment. And the weirdness that shows up in the double slit experiments also shows up in the triple split experiment, which confirms that subatomic particles have the ability to pass through all three slits simultaneously. These experiments show the "duality" of nature - detectors that register particles show them as particles, while detectors that register waves show them as waves. Which confirms that subatomic particles are actually blobs of uncollapsed probability waves, which collapse when you "look" at them.
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I just have one question though: I assume you are pretty familiar with the Double Slit Experiment that shows photons behaving as waves and or particles? Well I was wondering if a Triple Slit experiment had ever been tried or theorized about. It's well known that detecting a photon passing through one of two paths will cause the probability waveform to collapse in a Double Slit Experiment and show that photon behaving as a particle, but what would be the effect of monitoring one possible path in a triple slit experiment? Detecting the photon passing along the monitored path would obviously result in it behaving as a particle, but not detecting it would result in it having an equal probability of passing along either of the other two paths to the detector screen, would you end up with an experiment that showed a photon behaving as both a particle and a wave all in one experiment, or would the detecting device in one of the three paths result in every photon showing particle properties?
I assume from this question that you read neither the article nor Plane's response. This article is about the results of a team *conducting* the triple split experiment. And the weirdness that shows up in the double slit experiments also shows up in the triple split experiment, which confirms that subatomic particles have the ability to pass through all three slits simultaneously. These experiments show the "duality" of nature - detectors that register particles show them as particles, while detectors that register waves show them as waves. Which confirms that subatomic particles are actually blobs of uncollapsed probability waves, which collapse when you "look" at them.
Bingo
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Now that we have solved that one can we move on to Black Holes?
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There could be any number of slits involved .
The important part is the spaceing and the width of the slits .
This isn't easy , but you could make a grateing or a screen that caused an interference pattern as a single photon took every possible path the way a wave does . This ought to prove that a photon is a wave , but it doesn't because other experiments prove equally well that it behaves like a particle.
Now you still cannot pitch a baseball throw two diffrent windows in the same wall in a single pitch and you cannot get a sea wave to sit still , but the line that seaprates the weird duality of quantum reality gets a little clearer with each new experiment.
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Now that we have solved that one can we move on to Black Holes?
Another unrealized porn reference, Kramer?
I'll put in a vote to let Ami and others keep putting science-related articles on the board. They are interesting, though obviously not to you. I would say that they are among the few threads unlikely to lead to pointless flame wars, but this thread indicates that I underestimate the abilities and resolve of the thermowarrior set.
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Now that we have solved that one can we move on to Black Holes?
Another unrealized porn reference, Kramer?
I'll put in a vote to let Ami and others keep putting science-related articles on the board. They are interesting, though obviously not to you. I would say that they are among the few threads unlikely to lead to pointless flame wars, but this thread indicates that I underestimate the abilities and resolve of the thermowarrior set.
My my the Mormon has a dirty mind. The only thing that comes to my mind about black holes other than Black Holes is that thing they call a brain on Obama. Now that is a massive black hole that needs to be studied by mental health professionals.
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For a single Photon , you really can't perform two tests.
If you perform a test that fixes the position of the photon at a point you cannot also perform a test that finds a diffraction pattern , you may choose either one but never both .
Very simple , the photon is destroyed by the first test so it cannot be tested again.
For slightly larger particles or waves two tests can be performed , but the accuracy of one is affected by the other.
Heisenburg proved that there is a minimum energy required for any test , so there is a directly related limit on precision in very small measurements. at the tinyness of a single photon , the minimum energy is near the size of the photon itself.
I wonder if there might be a dodge for sidestepping the Heisenburg limits on precision? Experiments like this bring us close.
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Experiments like this bring us close.
oh yeah, I'm feeling the closeness, are you? Would that be called the Heisenburg Maneuver?
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Experiments like this bring us close.
oh yeah, I'm feeling the closeness, are you? Would that be called the Heisenburg Maneuver?
We are indeed close.
When you use a cell phone or a gps a good understanding of quantum effects and Einstienian rules of times relitivity are being demonstrated and used , quantum effects are important in the design of small circuits, and without correcting for the compression of time due to the satilites speed a gps couldn't aviod large error.
As circuits shrink and the individual pulses of electrons that operate the transistors also shrink , it becomes moe important all the time to understand quantum effects.
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Experiments like this bring us close.
oh yeah, I'm feeling the closeness, are you? Would that be called the Heisenburg Maneuver?
We are indeed close.
When you use a cell phone or a gps a good understanding of quantum effects and Einstienian rules of times relitivity are being demonstrated and used , quantum effects are important in the design of small circuits, and without correcting for the compression of time due to the satilites speed a gps couldn't aviod large error.
As circuits shrink and the individual pulses of electrons that operate the transistors also shrink , it becomes moe important all the time to understand quantum effects.
OK well now that you put it that way I am now more than ever against these experiments. Technology is out of control. Google is going to take over the world. We are prisoners to smart phones, computers, TV's, iPods, iPads, iPhones, ear phones, robots, bluray, GPS, voice recognition, face recognition, DNA testing, embryonic cell implanting and many other forms of crazy science and technology. I can actually remember the good old days when we had a Black & White TV. Now I'm thinking the Beatles ruined it all!
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Irony abounds.
It probably takes more money to set yourself up in a primitive homestead than it takes to get a good education and a technical job and an apartment in the city.
Ever see "the Yearling?" Back when pioneers worked to avoid starvation by planting food , ahhh well nostalgia will never get you there. Perhaps if you set up a Tesla car dealership you would eventually be able to afford sixty acres of hardscrabble farm?
http://www.imdb.com/title/tt0039111/fullcredits (http://www.imdb.com/title/tt0039111/fullcredits)
(http://[url=http://ia.media-imdb.com/images/M/MV5BMTM0OTQ4NjIyMl5BMl5BanBnXkFtZTYwNzY4MTM5._V1._SX96_SY140_.jpg]http://ia.media-imdb.com/images/M/MV5BMTM0OTQ4NjIyMl5BMl5BanBnXkFtZTYwNzY4MTM5._V1._SX96_SY140_.jpg[/url][)
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Irony abounds.
It probably takes more money to set yourself up in a primitive homestead than it takes to get a good education and a technical job and an apartment in the city.
Ever see "the Yearling?" Back when pioneers worked to avoid starvation by planting food , ahhh well nostalgia will never get you there. Perhaps if you set up a Tesla car dealership you would eventually be able to afford sixty acres of hardscrabble farm?
http://www.imdb.com/title/tt0039111/fullcredits (http://www.imdb.com/title/tt0039111/fullcredits)
(http://[url=http://ia.media-imdb.com/images/M/MV5BMTM0OTQ4NjIyMl5BMl5BanBnXkFtZTYwNzY4MTM5._V1._SX96_SY140_.jpg]http://ia.media-imdb.com/images/M/MV5BMTM0OTQ4NjIyMl5BMl5BanBnXkFtZTYwNzY4MTM5._V1._SX96_SY140_.jpg[/url][)
In the 'old' days not many people had time to get in trouble. Just food, clothing & sheltering took up 99% of our time. Can you imagine (75 years ago) people having the time to participate in a Gay Parade?
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Yeah, technology is all out of control, and it's all the Beatles' fault.
Do you blame Paul or Ringo more?
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Yeah, technology is all out of control, and it's all the Beatles' fault.
Do you blame Paul or Ringo more?
Nope I really think it's more John's fault than either of those two.
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Now that we have solved that one can we move on to Black Holes?
Another unrealized porn reference, Kramer?
I'll put in a vote to let Ami and others keep putting science-related articles on the board. They are interesting, though obviously not to you. I would say that they are among the few threads unlikely to lead to pointless flame wars, but this thread indicates that I underestimate the abilities and resolve of the thermowarrior set.
My my the Mormon has a dirty mind. The only thing that comes to my mind about black holes other than Black Holes is that thing they call a brain on Obama. Now that is a massive black hole that needs to be studied by mental health professionals.
WHAT? I saw you say "black" hole referring to Obama"s brain! You dirty racist, you!
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Now that we have solved that one can we move on to Black Holes?
Another unrealized porn reference, Kramer?
I'll put in a vote to let Ami and others keep putting science-related articles on the board. They are interesting, though obviously not to you. I would say that they are among the few threads unlikely to lead to pointless flame wars, but this thread indicates that I underestimate the abilities and resolve of the thermowarrior set.
My my the Mormon has a dirty mind. The only thing that comes to my mind about black holes other than Black Holes is that thing they call a brain on Obama. Now that is a massive black hole that needs to be studied by mental health professionals.
WHAT? I saw you say "black" hole referring to Obama"s brain! You dirty racist, you!
A true racist would say that the right side of his brain is white and the left is black. He is Mulatto, right?
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In the 'old' days not many people had time to get in trouble. Just food, clothing & sheltering took up 99% of our time.
Incorrect. During the middle ages and the renaissance, people had more leisure time than we do now.
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In the 'old' days not many people had time to get in trouble. Just food, clothing & sheltering took up 99% of our time.
Incorrect. During the middle ages and the renaissance, people had more leisure time than we do now.
I was referring to North America.
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I was referring to North America.
Prior to the industrial revolution, that was true in North America as well.
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I was referring to North America.
Prior to the industrial revolution, that was true in North America as well.
None of that nonsense matters regarding my original point. You have staggered away from my point in an effort to somehow build up your insecure ego. I really don't care how much time people had on their hands in the 'OLD' days I just know MOST people spent a lot more time building shelter, growing & hunting food, making cloths and other life support efforts because there were not supermarkets, Costco's, and other faster methods. Comparing the life of a peasant versus royalty is like comparing apples to oranges.
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Comparing the life of a peasant versus royalty is like comparing apples to oranges.
I'm talking about the life of "peasants" in pre-industrial times. Is that not the subject?
Terry Jones has a pretty good description in his book / documentary Medieval Lives (http://www.netflix.com/WiMovie/Terry_Jones_Medieval_Lives/70090365?trkid=1211018) (Netflix link, you can rent or watch online). Book is available through Amazon.
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Comparing the life of a peasant versus royalty is like comparing apples to oranges.
I'm talking about the life of "peasants" in pre-industrial times. Is that not the subject?
Terry Jones has a pretty good description in his book / documentary Medieval Lives (http://www.netflix.com/WiMovie/Terry_Jones_Medieval_Lives/70090365?trkid=1211018) (Netflix link, you can rent or watch online). Book is available through Amazon.
75 years ago isn't Medieval times. Medieval times doesn't include N. America, at least in my way of thinking.
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Could a luddite movement survive now?
Rather than retreat to what the past was really like could a modern antitech reform the past as it ought to have been?
Then live in it?
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75 years ago isn't Medieval times. Medieval times doesn't include N. America, at least in my way of thinking.
75 years ago was during the industrial revolution. If you want to get back to the land and live on your own resources, you need to go to pre-industrial times. 75 years ago life was roughly the same as now, without some of the conveniences. The last time people were able to live on their own without outside support was during the middle ages / early renaissance.
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75 years ago isn't Medieval times. Medieval times doesn't include N. America, at least in my way of thinking.
75 years ago was during the industrial revolution. If you want to get back to the land and live on your own resources, you need to go to pre-industrial times. 75 years ago life was roughly the same as now, without some of the conveniences. The last time people were able to live on their own without outside support was during the middle ages / early renaissance.
OK
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Perhaps if you are willing to live with a lot less, you might make it as a subsistence farmer. Perhaps it would be hard to wear animal skins until you built a loom for fabric. I am not saying that it would be likely or easy, just that it could be possible.
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Perhaps if you are willing to live with a lot less, you might make it as a subsistence farmer. Perhaps it would be hard to wear animal skins until you built a loom for fabric. I am not saying that it would be likely or easy, just that it could be possible.
I made my first loom in an afternoon. Wasn't great, but it worked.
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Perhaps you would be better than average at subsistence existence. You seem to be rather inventive, and many are not.
Actually, I would say that someone with a Whole Earth Catalog could get by a lot better than the average 1800's pioneers or medieval peasants.
I understand how a loom works, but I am not that confident that I could make any seriously wearable clothing without several weeks of practice. If I had to grow my own food and tend to livestock, that would make it harder. A subsistence farmer is not an 8 hour a day job.
My friend Peter Gardiner, the German I met in Paraguay, said that land reform in Paraguay is impossible, because giving a family 20 hectares and no equipment would be a death sentence. He seems to have done fairly well for himself, but then, he has a degree in agronomy and came to Paraguay with money. The average Paraguayan campesino cannot read. What happens is that a group of campesinos demands land from a large estancia, and if they get it, because the extanciero is in bad with the government (which is rare), they sell out within a year and go on to another place. I have no way to verify that, but I have read articles about this. Not being Paraguayan, I am unable to have a valid opinion about this.
I would say that Peter has proven that a person can be self-sufficient if he is clever enough. See his new website at paraguay.ch. But again, he is anything but typical. I am thinking that he was very clever to get that website.
Read about the Mennonite farmers in the Chaco sometime. They came between the end of WWI and the 1950's and started with practically nothing.
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Actually, I would say that someone with a Whole Earth Catalog could get by a lot better than the average 1800's pioneers or medieval peasants.
I think that Lehman's in Ohio (http://www.lehmans.com/) is a better resource. They specialize in stuff for the Amish, so most of their tools and equipment either don't require power, or use simple, easy to obtain fuels like alcohol, vegetable oils, or kerosene.
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The Whole Earth catalogue is not a mail order house. It is a compendium of how-to information. I have heard of Lehmans, and they sound fine, but the Whole Earth catalogue is something entirely different.It tells you how to make simple devices and gives info on where you can find more detail. During the siege of Gorazde in Bosnia, they built small dynamos on the River Drina after those mentioned in the WEC. It was the all-purpose handbook at every Hippie commune around in the 60's and 70's.
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The Whole Earth catalogue is not a mail order house. It is a compendium of how-to information. I have heard of Lehmans, and they sound fine, but tghe Whole Earth catalogue is something entirely different.
Yes, I have several versions (it was updated many times). It was, however, still basically a list of items and tools along with how to use them and where to get them. The last one was published in 1998 and is totally out of date by now. A better source is Mother Earth News, to which I continue to subscribe, as it's sources and information have been kept up to date. However, many of the items in both still assume a steady source of electricity, while many of the items sold by Lehman's do not (which is why many Amish and Mennonite buy from them).
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you and and your Triple-slit experiment are boring. Plane liked it though so don't feel too bad.
Yes, I understand that a lack of intelligence makes the story seem boring. However, those of us with normal or better levels of intelligence find it interesting.
You have a fixation on intelligence going way back. Is there something in your past that keeps bringing up this word in so many of your posts or is this just a typical and boring response, because you have nothing else in your ammo bag? Is this 'intelligence' thing a deep seated childhood scar or wound that keeps rearing its ugly head revealing something sinister and ugly about a past event in your life? Did someone in your early life taunt or keep telling you that you were dumb or not smart enough? I find that both you and XO seem to use this (dumb label) as your #1 insult. Have you ever considered adding other insults to your repertoire or do you plan on using the generic 'you are dumb' line all the time? It certainly would be more entertaining being more creative with your insults or shall I say childish retorts. Or is creativity lacking in your so-called superior intelligence? Are you one of those really brainy guys that lack common sense? I find it odd that you have taken this triple slit experiment thing so personal, why? What is your investment? Just because the subject is as boring as watching paint dry (to most people) shouldn't curb your enthusiasm. By all means have a good time delving deeper and deeper into the subject. No doubt I'm wrong and you are right that most people are just fascinated by this subject. In his next SOTUA Obama should devote at least 5,000 words to the subject.
What the hell??? The information is fascinating - to be sure, I consider physics breakthroughs of any kind to be fascinating, but this is the best of the best.
I don't get why you were picking at Ami in the first place.
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you and and your Triple-slit experiment are boring. Plane liked it though so don't feel too bad.
Yes, I understand that a lack of intelligence makes the story seem boring. However, those of us with normal or better levels of intelligence find it interesting.
You have a fixation on intelligence going way back. Is there something in your past that keeps bringing up this word in so many of your posts or is this just a typical and boring response, because you have nothing else in your ammo bag? Is this 'intelligence' thing a deep seated childhood scar or wound that keeps rearing its ugly head revealing something sinister and ugly about a past event in your life? Did someone in your early life taunt or keep telling you that you were dumb or not smart enough? I find that both you and XO seem to use this (dumb label) as your #1 insult. Have you ever considered adding other insults to your repertoire or do you plan on using the generic 'you are dumb' line all the time? It certainly would be more entertaining being more creative with your insults or shall I say childish retorts. Or is creativity lacking in your so-called superior intelligence? Are you one of those really brainy guys that lack common sense? I find it odd that you have taken this triple slit experiment thing so personal, why? What is your investment? Just because the subject is as boring as watching paint dry (to most people) shouldn't curb your enthusiasm. By all means have a good time delving deeper and deeper into the subject. No doubt I'm wrong and you are right that most people are just fascinated by this subject. In his next SOTUA Obama should devote at least 5,000 words to the subject.
What the hell??? The information is fascinating - to be sure, I consider physics breakthroughs of any kind to be fascinating, but this is the best of the best.
I don't get why you were picking at Ami in the first place.
There is a certain elegance in the double slit experiment , it uses simple concept to prove grand concept.
Quantum mechanics is confusing ,most of us are not used to it.
But it really is how things work on that scale , we are accustomed to things on our own scale where throwing a rock results in a hit or a miss , not in a probability that can only be partially measured.
How many people feel sorry for Shrodingers cat?
If you read "Dresden Codax ",the comic, you know that there is a fan base of people who do "get" jokes about Phisics and Science concept.
http://dresdencodak.tumblr.com/post/863092417/how-a-dresden-codak-page-is-made (http://dresdencodak.tumblr.com/post/863092417/how-a-dresden-codak-page-is-made)
Also there is a whole nother layer of people who have a hobby of makeing Superman Cannon make sense .
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http://amultiverse.com/2010/07/23/hamster-drippings/ (http://amultiverse.com/2010/07/23/hamster-drippings/)
(http://amultiverse.com/files/comics/2010-07-23-Hamster-Drippings.gif)
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How many people feel sorry for Shrodingers cat?
I feel worse for this poor puppy being awakened in this description of Quantum Interrogation - or Kramer's head exploding when he reads it:
http://blogs.discovermagazine.com/cosmicvariance/2010/05/26/repost-quantum-interrogation/ (http://blogs.discovermagazine.com/cosmicvariance/2010/05/26/repost-quantum-interrogation/)
Quantum mechanics, as we all know, is weird. It?s weird enough in its own right, but when some determined experimenters do tricks that really bring out the weirdness in all its glory, and the results are conveyed to us by well-intentioned but occasionally murky vulgarizations in the popular press, it can seem even weirder than usual.
Last week was a classic example: the computer that could figure out the answer without actually doing a calculation! (See Uncertain Principles, Crooked Timber, 3 Quarks Daily.) The articles refer to an experiment performed by Onur Hosten and collaborators in Paul Kwiat?s group at Urbana-Champaign, involving an ingenious series of quantum-mechanical miracles. On the surface, these results seem nearly impossible to make sense of. (Indeed, Brad DeLong has nearly given up hope.) How can you get an answer without doing a calculation? Half of the problem is that imprecise language makes the experiment seem even more fantastical than it really is ? the other half is that it really is quite astonishing.
Let me make a stab at explaining, perhaps not the entire exercise in quantum computation, but at least the most surprising part of the whole story ? how you can detect something without actually looking at it. The substance of everything that I will say is simply a translation of the nice explanation of quantum interrogation at Kwiat?s page, with the exception that I will forgo the typically violent metaphors of blowing up bombs and killing cats in favor of a discussion of cute little puppies.
So here is our problem: a large box lies before us, and we would like to know whether there is a sleeping puppy inside. Except that, sensitive souls that we are, it?s really important that we don?t wake up the puppy. Furthermore, due to circumstances too complicated to get into right now, we only have one technique at our disposal: the ability to pass an item of food into a small flap in the box. If the food is something uninteresting to puppies, like a salad, we will get no reaction ? the puppy will just keep slumbering peacefully, oblivious to the food. But if the food is something delicious (from the canine point of view), like a nice juicy steak, the aromas will awaken the puppy, which will begin to bark like mad.
It would seem that we are stuck. If we stick a salad into the box, we don?t learn anything, as from the outside we can?t tell the difference between a sleeping puppy and no puppy at all. If we stick a steak into the box, we will definitely learn whether there is a puppy in there, but only because it will wake up and start barking if it?s there, and that would break our over-sensitive hearts. Puppies need their sleep, after all.
Fortunately, we are not only very considerate, we are also excellent experimental physicists with a keen grasp of quantum mechanics. Quantum mechanics, according to the conventional interpretations that are good enough for our purposes here, says three crucial and amazing things.
First, objects can exist in ?superpositions? of the characteristics we can measure about them. For example, if we have an item of food, according to old-fashioned classical mechanics it could perhaps be ?salad? or ?steak.? But according to quantum mechanics, the true state of the food could be a combination, known as a wavefunction, which takes the form (food) = a(salad) + b(steak), where a and b are some numerical coefficients. That is not to say (as you might get the impression) that we are not sure whether the food is salad or steak; rather, it really is a simultaneous superposition of both possibilities.
The second amazing thing is that we can never observe the food to be in such a superposition; whenever we (or sleeping puppies) observe the food, we always find that it appears to be either salad or steak. (Eigenstates of the food operator, for you experts.) The numerical coefficients a and b tell us the probability of measuring either alternative; the chance we will observe salad is a2, while the chance we will observe steak is b2. (Obviously, then, we must have a2 + b2 = 1, since the total probability must add up to one [at least, in a world in which the only kinds of food are salad and steak, which we are assuming for simplicity].)
Third and finally, the act of observing the food changes its state once and for all, to be purely whatever we have observed it to be. If we look and it?s salad, the state of the food item is henceforth (food) = (salad), while if we saw that it was steak we would have (food) = (steak). That?s the ?collapse of the wavefunction.?
You can read all that again, it?s okay. It contains everything important you need to know about quantum mechanics; the rest is just some equations to make it look like science.
Now let?s put it to work to find some puppies without waking them up. Imagine we have our morsel of food, and that we are able to manipulate its wavefunction; that is, we can do various operations on the state described by (food) = a(salad) + b(steak). In particular, imagine that we can rotate that wavefunction, without actually observing it. In using this language, we are thinking of the state of the food as a vector in a two-dimensional space, whose axes are labeled (salad) and (steak). The components of the vector are just (a, b). And then ?rotate? just means what it sounds like: rotate that vector in its two-dimensional space. A rotation by ninety degrees, for example, turns (salad) into (steak), and (steak) into -(salad); that minus sign is really there, but doesn?t affect the probabilities, since they are given by the square of the coefficients. This operation of rotating the food vector without observing it is perfectly legitimate, since, if we didn?t know the state beforehand, we still don?t know it afterwards.
So what happens? Start with some food in the (salad) state. Stick it into the box; whether there is a puppy inside or not, no barking ensues, as puppies wouldn?t be interested in salad anyway. Now rotate the state by ninety degrees, converting it into the (steak) state. We stick it into the box again; the puppy, unfortunately, observes the steak (by smelling it, most likely) and starts barking. Okay, that didn?t do us much good.
But now imagine starting with the food in the (salad) state, and rotating it by 45 degrees instead of ninety degrees. We are then in an equal superposition, (food) = a(salad) + a(steak), with a given by one over the square root of two (about 0.71). If we were to observe it (which we won?t), there would be a 50% chance (i.e., [one over the square root of two]2) that we would see salad, and a 50% chance that we would see steak. Now stick it into the box ? what happens? If there is no puppy in there, nothing happens. If there is a puppy, we have a 50% chance that the puppy thinks it?s salad and stays asleep, and a 50% chance that the puppy thinks it?s steak and starts barking. Either way, the puppy has observed the food, and collapsed the wavefunction into either purely (salad) or purely (steak). So, if we don?t hear any barking, either there?s no puppy and the state is still in a 45-degree superposition, or there is a puppy in there and the food is in the pure (salad) state.
Let?s assume that we didn?t hear any barking. Next, carefully, without observing the food ourselves, take it out of the box and rotate the state by another 45 degrees. If there were no puppy in the box, all that we?ve done is two consecutive rotations by 45 degrees, which is simply a single rotation by 90 degrees; we?ve turned a pure (salad) state into a pure (steak) state. But if there is a puppy in there, and we didn?t hear it bark, the state that emerged from the box was not a superposition, but a pure (salad) state. Our rotation therefore turns it back into the state (food) = 0.71(salad) + 0.71(steak). And now we observe it ourselves. If there were no puppy in the box, after all that manipulation we have a pure (steak) state, and we observe the food to be steak with probability one. But if there is a puppy inside, even in the case that we didn?t hear it bark, our final observation has a (0.71)2 = 0.5 chance of finding that the food is salad! So, if we happen to go through all that work and measure the food to be salad at the end of our procedure, we can be sure there is a puppy inside the box, even though we didn?t disturb it! The existence of the puppy affected the state, even though we didn?t (in this branch of the wavefunction, where the puppy didn?t start barking) actually interact with the puppy at all. That?s ?non-destructive quantum measurement,? and it?s the truly amazing part of this whole story.
But it gets better. Note that, if there were a puppy in the box in the above story, there was a 50% chance that it would start barking, despite our wishes not to disturb it. Is there any way to detect the puppy, without worrying that we might wake it up? You know there is. Start with the food again in the (salad) state. Now rotate it by just one degree, rather than by 45 degrees. That leaves the food in a state (food) = 0.999(salad) + 0.017(steak). [Because cos(1 degree) = 0.999 and sin(1 degree) = 0.017, if you must know.] Stick the food into the box. The chance that the puppy smells steak and starts barking is 0.0172 = 0.0003, a tiny number indeed. Now pull the food out, and rotate the state by another 1 degree without observing it. Stick back into the box, and repeat 90 times. If there is no puppy in there, we?ve just done a rotation by 90 degrees, and the food ends up in the purely (steak) state. If there is a puppy in there, we must accept that there is some chance of waking it up ? but it?s only 90*0.0003, which is less than three percent! Meanwhile, if there is a puppy in there and it doesn?t bark, when we observe the final state there is a better than 97% chance that we will measure it to be (salad) ? a sure sign there is a puppy inside! Thus, we have about a 95% chance of knowing for sure that there is a puppy in there, without waking it up. It?s obvious enough that this procedure can, in principle, be improved as much as we like, by rotating the state by arbitrarily tiny intervals and sticking the food into the box a correspondingly large number of times. This is the ?quantum Zeno effect,? named after a Greek philosopher who had little idea the trouble he was causing.
So, through the miracle of quantum mechanics, we can detect whether there is a puppy in the box, even though we never disturb its state. Of course there is always some probability that we do wake it up, but by being careful we can make that probability as small as we like. We?ve taken profound advantage of the most mysterious features of quantum mechanics ? superposition and collapse of the wavefunction. In a real sense, quantum mechanics allows us to arrange a system in which the existence of some feature ? in our case, the puppy in the box ? affects the evolution of the wavefunction, even if we don?t directly access (or disturb) that feature.
Now we simply replace ?there is a puppy in the box? with ?the result of the desired calculation is x.? In other words, we arrange an experiment so that the final quantum state will look a certain way if the calculation has a certain answer, even if we don?t technically ?do? the calculation. That?s all there is to it, really ? if I may blithely pass over the heroic efforts of some extremely talented experimenters.
Quantum mechanics is the coolest thing ever invented, ever.
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Quantum mechanics is the coolest thing ever invented, ever.
I prefer the cat. If looks could kill . . .
That was a great post, Henny. If I could only get off my lazy duff and get into quantum physics I am sure it would be a favorite subject. It's just that I have so much to do and so little energy. My eldest daughter is reading a book about the universe called "The Whole Shebang" that looks terribly interesting. But I have a reading list that is ever-growing and a way-too-involved love of learning new things. I think the medical term is ADHD - lol!
You have now swung the pendulum of my easily-distracted interest towards the subject. Thanks!
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Quantum mechanics is the coolest thing ever invented, ever.
I prefer the cat. If looks could kill . . .
That was a great post, Henny. If I could only get off my lazy duff and get into quantum physics I am sure it would be a favorite subject. It's just that I have so much to do and so little energy. My eldest daughter is reading a book about the universe called "The Whole Shebang" that looks terribly interesting. But I have a reading list that is ever-growing and a way-too-involved love of learning new things. I think the medical term is ADHD - lol!
You have now swung the pendulum of my easily-distracted interest towards the subject. Thanks!
I think it's totally worth it, Pooch. Although I'm not a purist like Ami or Plane - I need things dumbed down for me, ala Brian Greene, Michio Kaku, etc. ;D
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If I could only get off my lazy duff and get into quantum physics I am sure it would be a favorite subject.
Ahhh, skip the quantum mechanics and dive into string theory. Read a couple of Brian Greene's books on strings.
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I am thinking that quantum mechanics has always existed, and therefore is not an invention. It's a discovery. Just like we cannot say that Columbus (or the Indians) invented America. It is a bit difficult to comprehend, because the universe was not designed for us to understand it or how it works. There may be an operating system, but it is not human-user friendly.
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If I could only get off my lazy duff and get into quantum physics I am sure it would be a favorite subject.
Ahhh, skip the quantum mechanics and dive into string theory. Read a couple of Brian Greene's books on strings.
Indeed: Greene's books are (for me) religious ecstasy in amazement and wonder. Better even.
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I am thinking that quantum mechanics has always existed, and therefore is not an invention. It's a discovery. Just like we cannot say that Columbus (or the Indians) invented America. It is a bit difficult to comprehend, because the universe was not designed for us to understand it or how it works. There may be an operating system, but it is not human-user friendly.
Did Quanta all have diffrent waveform before they were observed?
Did Quantum mechanics have a diffrent state pre its discovery?
How will we know?
Pass me some of that salad.
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I am thinking that quantum mechanics has always existed, and therefore is not an invention. It's a discovery. Just like we cannot say that Columbus (or the Indians) invented America. It is a bit difficult to comprehend, because the universe was not designed for us to understand it or how it works. There may be an operating system, but it is not human-user friendly.
Did Quanta all have diffrent waveform before they were observed?
Did Quantum mechanics have a diffrent state pre its discovery?
How will we know?
Pass me some of that salad.
*Chuckle*
I feel like buying a pocket protector and adding a snort to my laugh - great observation! :D