Quantum Holography

Buzz Skyline writes "Physicists succeed where psychics fail. Researchers from Boston University propose a quantum holography system that can construct 3d images of objects sealed in closed containers. Could it lead to quantum luggage scanners at the airport?"

Comments

Schroedinger's Cat

[gblues]

Great! Now we'll be able to tell Schroedinger once and for all whether his stupid cat is dead or not.

Nathan

Re:Schroedinger's Cat

[the_2nd_coming]

yeah, what implications will this have on that tried and true metiphor? by doing this, we are not realy observing the object directly, we are indirectly observing it. so does this destroy the uncertanty priciple or is this considered direct observation?

Re:Schroedinger's Cat

[Octal]

Actually, I got bored last week and opened the box. The cat died of starvation and has been decomposing for years. The radioactive isotope still hasn't decayed, however.

Re:Schroedinger's Cat

[FrozedSolid]

We are observing the object, period. If it's observed, then it completely destroys the principle.

Duh :)

Re:Schroedinger's Cat

[Tenebrious1]

It wasn't actually Shroedinger's cat. He was a dog person. He used his girlfriend's cat, which he didn't like too much anyway.

Re:Schroedinger's Cat

[the_2nd_coming]

it seems to me that we are just observing the interactions of photons that we send into the box. not looking at the object in any way.

Re:Schroedinger's Cat

[SuperguyA1]

Given that this theory is what? 40-50 years old. I would guess that the cat is dead, regardless of the isotope.

Re:Schroedinger's Cat

[big_groo]

Uh...that's how we 'see' - by our retinal receptors detecting said 'photons'.

Re:Schroedinger's Cat

[autocracy]

If mere observation ruins it, what the hell do you think shooting particles at the stuff is going to do?

Re:Schroedinger's Cat

[elmegil]

But we're not looking at the photons in the box, we're looking at quantum entangled photons that never were in the box.

Re:Schroedinger's Cat

[base2op]

Nothing is observed directly. Sad, but true.

Re:Schroedinger's Cat

[jeffy124]

Schroedinger's gonna have to rephrase the question - is the cat dead or just sleeping?

Re:Schroedinger's Cat

[the_2nd_coming]

it is not that the particles are ruining it, it is that quantom probability states that when you do not observe an object you can not make an asumption on its state. hitting it with particles will do nothing since we realy don't know if the particles are hitting it or not. what we are observing is the quantom entangles photons that have never been in the box and that is what give us the immage.....quantom entangle ment is the instant communication of 2 sub atomic particles. (this is what puts the GR folks on there head since 2 quantom entangeled particles could be 1,000,000 Lightyears away from each other, but they can communicate to each other instantly which would make that communication faster than light which is impossable according to GR.

Re:Schroedinger's Cat

[Paolomania]

Great! Now we'll be able to tell Schroedinger once and for all whether his stupid cat is dead or not.

great ... in a godellian twist, a quantum device is created that invalidates the principles of quantum physics upon which it is based - to be followed shortly thereafter by the implosion of the universe. i wonder what the great big BSoD in the sky will look like ...

Re:Schroedinger's Cat

[Kushana]

The idea that observation destroys states is an unfortunate one that is false. In no case should one think of consciousness as physically producing a change in the state of a system.

The real meat behind the Cat is coherence, which deals with the amount of quantum interaction between an object and the rest of the universe. Perhaps unfortunately (for quantum literature, anyway), cats interact way too much to ever wholly enter an indeterminate quantum state.

Re:Schroedinger's Cat

[yesthatguy]

You could always just smash the box with a sledgehammer, and leave it there. Then you'd never have to worry whether the cat is alive or not, and could worry about more important things :)

Re:Schroedinger's Cat

[SpinyNorman]

The collapse postulate is an add-on hack to the Cohenhagen interpretation that makes for a simplistic quantum to classical mapping. IMO it's bunk - the other interpretations that don't require it make a lot more sense, if not [i]common]/i] sense!

IMO the quantum wave is it. Everything is just probabalistic (there is no classical reality), but sometimes the probability is close to 100% or at least appears that way.

Re:Schroedinger's Cat

[yesthatguy]

*Anything* which firmly establishes the state of the cat will collapse the wave function. If you burn the box in a crematorium, the cat is definitely dead -- no uncertainty. If you "see" into the box using a method other than opening it, then you know the result. There are many ways to collapse the metaphorical wave function, observing it is just the most direct way, and also relates most directly to the position of an electron, which can best be determined by observation, though not with the naked eye.

Re:Schroedinger's Cat

[Faramir]

This is a good question, and there have already been several good answers. However, I don't feel like they've really answered your question.

Far from destroying the uncertainty principal, the article indicates that one of the "spooky" things about quantum holography is, essentially, the exploitation of the uncertainty principle.

Now, as to direct observation and the uncertainty principle: perhaps these should be explained for the casual /.'ers out there.

The uncertainty principle says that we cannot know exactly both the position and momentum at the same time. Momentum is a combination of mass and velocity. Mass often remains constant, so sometimes this is stated as "position and velocity" instead. Now, I used the word "exactly", and I meant just that. We can have a good idea of both numbers, but the more exact one measurement is, the less exact the other measurement will be. Basically, think of it this way: if we take a probe, like the tip of a pencil, and move it around till we find exactly were a particle is, we'll find it. But we'll also hit it and change its momentum.

Now, all observations require some kind of probe, be it pencils, electrons, or photons (light). A related feature of quantum mechanics is that the equations we use to determine where a particle (or wave, they're the same thing at this level) is going (the famous Schrodinger equations) don't actually tell us where a particle is going--only where its likely to go. So we don't even know how to say where it is going to go. In fact, it is considered that a particle does not have just one specific path until the particle has been measured.

In our case, that measurement--that is, the observation of the photons--occurs at the wall of the chamber. And from this data, convoluted equations work backwards to figure out what the photons bounced off of.

Hope that helps...

Re:Schroedinger's Cat

[Anonymous Coward]

what a55h01e moderator gave this comment a redundant? the rest of the world sees it funny and insightful.

Re:Schroedinger's Cat

[autocracy]

If I shoot a bullet through the center of 3 pieces of paper all one inch a part at signifigant speed, I KNOW it will hit the forth one that I can't see if it's an inch away. Physics. And you can damned well bet that it changed things. (Note: I do believe in the theory of quantum *).

Re:Schroedinger's Cat

[Anonymous Coward]

..but they can communicate to each other instantly which would make that communication faster than light which is impossable according to GR.

No they don't. It's correlation NOT communication! You can't transmit information that way. All you get is random noise.

Re:Schroedinger's Cat

[jabber01]

He's not dead.. He's pining for the fjords!!

Re:Schroedinger's Cat

[SpinyNorman]

Actually, Schroedringer's cat, being a classsically sized critter, is saved from the being a member of the living dead by decoherence.

How decoherence killed schroedringer's cat

Maybe one day we'll be able to figure out how to keep cats in superimposed states, but for the time being Schroedringer's gonna have to decide whether to whack the cat before he closes the lid.

Re:Schroedinger's Cat

[Happy Monkey]

great ... in a orwellian twist, a quantum device is created that invalidates the principles of quantum physics upon which it is based - to be followed shortly thereafter by its use in airport security.

Re:Schroedinger's Cat

[mindstrm]

This has nothing to do (as others pointed out) with the Uncertainty Principle.

The Schroedinger's Cat thought-experiment is totally different.

ANd how does this bother the Cat problem at all? It doesn't.. if you observe the Cat in the box, in any way whatsoever, you have now observed it, and hence, caused it to assume a known state.

Re:Schroedinger's Cat

[jd10131]

What about the black hole between the third and fourth sheets of paper? You can never be certain, unless you look. =)

It all comes down to black holes in the end... =)

Re:Schroedinger's Cat

[Anonymous Coward]

On a related note, I solved Schroedinger's cat a few years ago. What you do is perform the two-slit experiment, with single electrons, with a device to measure which slit the electron goes through.
If you place it right, such that the CRT screen is outside the chamber, but the slit-measurement device displays its output only to the cat, then the wave of the electron breaks down iff:

1. cats have souls (meaning they consistently break down quantum phenomena by observation, or something like that)
   AND
   
2. the cat is alive

If the cat is dead, the wave should not break down, so the interference pattern should show on the screen. If cats go into a quantum state of being half dead, the interference pattern would always show, otherwise 50% of the time the interference pattern would disappear.
The actual solution is left to the reader.

-- TDR

Re:Schroedinger's Cat

[autocracy]

What makes you think the paper wouldn't be ripped away?

Re:Schroedinger's Cat

[Iron Webmaster]

Yes but ...

Do we see the inside of the box or the inside of the cat or the inside of the cat's stomach?

Re:Schroedinger's Cat

[jafac]

so, you're saying that, because math is an imperfect tool for deriving the particle's exact location, that the particle is not in an exact location?

Re:Schroedinger's Cat

[Pseudonym]

Exactly. Indeed, the molecules, atoms and subatomic particles in the air, the poison, the box and the rest of the cat can act like "observers" to the events caused by the introduction of poison into the cat's anatomy, causing the wavefunction to collapse.

Re:Schroedinger's Cat

[simon_cockle]

I think he has it wrong.

We cannot know both the momentum and position of a particle (i.e. electron) at a given time not because of the limitations of experimentation (due to interference of the observer) but because electrons (for example) do not have both the properties of position and momentum at a given instant. An electron can have either a known position *or* a known momentum at a given time, never both.

Re:Schroedinger's Cat

[rasilon]

cats have souls (meaning they consistently break down quantum phenomena by observation,

Yippee, my calculator has a soul! Not only that, but so do my socks!

Re:Schroedinger's Cat

[DavidTC]

You mean, it's lack of communication like, oh...what the object in the box looks like?

Granted, you can't send normal information, like 'Hello world', but it certainly is possible to send 'information', as in, something that isn't know at the other end, as demonstrated by the article above.

Re:Schroedinger's Cat

[supruzr]

Well if you read the article, you will see that light is being bounced off the object in question. This more or less explicitly states that direct observation is taking place, where "observation" is defined as bombarding an object with particles in order to learn something about it. The fact that these photons never reach human eyes is irrelevant. The fact that the photons are entangled with others somewhere else is irrelevant. So yes, the state of Schrodinger's cat collapses, and we can determine that it is either alive or dead, but not a superposition of both.

Re:Schroedinger's Cat

[Faramir]

No, this is not what I was saying. I apologize if it sounds so.

The example was intended to help illuminate the meaning/effect of the uncertainty principle, not explain from whence it arises.

Another reply correctly stated that one way of looking at things is that the particle/wave does not have a specific location or momentum until it is measured. I think I said that in my previous post.

So, it has nothing to do with math being an imperfect tool, and there is no judgement on math's perfection or lack of as a tool.

Re:Schroedinger's Cat

[Hal-9001]

The actual solution is left to the reader.

Will it fit in the margin? ;-)

Re:Schroedinger's Cat

[Fjord]

Pining for the fjords? What kind of talk is that?

Re:Schroedinger's Cat

[Augury]

Actually, as is commonly noted alongside this experiment, if you use a device which measures which slit the particle goes through, the wave is collapsed at the moment that device performs that detection. That means you will always get a collapsed wave, whether the cat has a soul/is alive/etc or not.

Sorry to burst the bubble. :P

Re:Schroedinger's Cat

[Augury]

Actually, it's already been determined that the collapse of a quantum entanglement is not a 'communication', since you cannot determine or effect which state these particles are in, just that they are in a similar state. I've read a doc somewhere which explains this much more clearly, but basically, it doesn't break GR.

Psychic?

[s20451]

Physicists succeed where psychics fail.

Sure, but can it tell me whether my wife is cheating on me? Or that I will meet a mysterious stranger after a journey of great distance?

Re:Psychic?

[AstroJetson]

This can.

Re:Psychic?

[Anonymous Coward]

the physicist could be porking your wife and waiting to kill you in london. L)

No luggage scanning here

[Rob Parkhill]

The article seems to imply that you need a specially constructed sphere to make this work. One that lets light in at a specific point, and allows no light out. It also is built in such a way to detect when a photon hits the inside surface. Just take a look at the diagram.

So unless someone is stupid enough to try and sneak a bomb onto a plane in one of these spheres, it's not much use to the security guards.

Re:No luggage scanning here

[frank_adrian314159]

So unless someone is stupid enough to try and sneak a bomb onto a plane in one of these spheres, it's not much use to the security guards.

We could always pass a law mandating that all bombs being carried on by terrorists be enclosed in this type of sphere.

And if that didn't work, we could always require that the device be clearly labeled "BOMB". I think a $300 fine should be sufficient penalty for this, don't you? At least it would be if we were talking about corporate violators...

Re:No luggage scanning here

[the_2nd_coming]

true, but a few years ago, reasearchers transported a photon from point a to point b with out the photon traversing the space in between. this would let you get the photons into the container with out having to have a hole......of cource reading the results is a diffrent issue.

Re:No luggage scanning here

[Strange_Attractor]

Don't dismiss it too hastily!
The specially constructed sphere is the easiest, and thus first, configuration to be tried in the lab.

All they need to do is require all interior luggage surfaces be built from these time-reporting light sensors (and maybe prevent travellers from putting anything else in the bag if they have a bomb), and voila! No time-and-cost-prohibitive bomb-sniffing machinery!

Re:No luggage scanning here

[Tiny Elvis]

There is no need to label it "BOMB" if you just require all bombs use the classic bomb shape: bowling ball sized black spheres with a large fuse on top. A stick or bundle of TNT should be OK too, assuming it is bright red and also uses a lit fuse.

Re:No luggage scanning here

[Bradee-oh!]

ah, but they did that by exploiting the whole entangled-pair thing that the 3d scanning is supposed to exploit. Now I'm no quantum mechanic, but unless you can create some sort of entangled triad of photons - one entanglement for the teleportation and one for the scanning, I dunno how that'd work :)

Re:No luggage scanning here

[Bradee-oh!]

...and thousands of people unhappy at being forced to drop 50 grand on their high tech luggage instead of throwing a change of clothes in a backpack.

Good plan :)

Re:No luggage scanning here

[linzeal]

If you consider Caddyshack a classic by now can we have small plactic explosive rodents?

Re:No luggage scanning here

[gpinzone]

I'm shocked nobody has come up with another use for this concept other than as a means to look for bombs in luggage. It's not like this could have prevented the 9/11 disaster since there were no bombs brought on board any of the planes.

Come on people! Where are all the tinfoil-helmet-wearing-security-freaks when you need them? How can the government use this to invade our privacy? this is Slashdot for cry-not-loud!

Re:No luggage scanning here

[gpinzone]

Do you really think Osama bin Laden gets his explosives from Acme Labs? We already know Bert is involved with Osama; maybe WileE.Coyote is in cahoots with him, too!

Peering into luggage..

[billn]

Would spare them from the dreaded Dirty Laundry DoS attack frequently perpetrated at Customs. =)

Unexciting

[Anonymous Coward]

These little "press releases from the future" never amount to anything.

Nice ap, but no real world potential yet

[linuxrunner]

As I see it, if you CAN'T see the back side of an object, then you can't see it!

You can assume what it looks like and then create an image out of that assumption, but unless you are looking directly at it, you'll never know.

Re:Nice ap, but no real world potential yet

[Myriad]

As I see it, if you CAN'T see the back side of an object, then you can't see it! You can assume what it looks like and then create an image out of that assumption, but unless you are looking directly at it, you'll never know.

Ah, but what if I knew what it looked like before setting the whole thing up? If my hologram looked like the original, as I saw it in the first place, then is this not accurate?

I suppose you could argue collapsing wave functions and quantum probability, but I'd think that was pushing it, no?

Re:Nice ap, but no real world potential yet

[Anonymous Coward]

no its not.

More important implmentations

[scott1853]

Why does everybody still have airport security on their brain still? Think if this can be used in medicine.

No more exploratory surgery. Quickly detect cancer growths.

Re:More important implmentations

[Syberghost]

No more exploratory surgery. Quickly detect cancer growths.

Yeah, I can see it now:

"After putting you in this big sphere and exposing you to massive amounts of electromagnetic radiation, we've determined that you do indeed have skin cancer."

Re:More important implmentations

[scott1853]

1.37% of Slashdot posters actually read the articles

Re:More important implmentations

[Tiny Elvis]

What if you have to fly in a plane to get to the lab where they have this equipment? You could be blown up.

Re:More important implmentations

[Anonymous Coward]

I was kidding about the luggage scanners. I guess the joke is a little tired though.

Re:More important implmentations

[drsquare]

Why would anyone want to read articles? Articles are boring. Posting to Slashdot is fun.

Re:More important implmentations

[Guignol]

LOL
if you did read the article to know how the stuff is supposed to work, then if you want to see the inside of someone's body instead of inside the sphere, then you can imagine how it's going to be done.
At last, our Trolls favorite guy doing something useful for science.
(for the preliminary tests, until they can do with something smaller)

Re:More important implmentations

[Anonymous Coward]

Yeah! And the FBI can also use it to take a virtual walk through our "private" residences - without our even knowing it! This is so fucking cool! Who ever said freedom isn't free?

X - Ray Specs

[__4096]

Perhaps somone will be able to make a pair of X-RAY specs that actually work! :)

Re:X - Ray Specs

[Anonymous Coward]

do they have a laser that puts out X-Rays? if so then why don't they just use that ot get hidden holographic objects.

Re:X - Ray Specs

[Anonymous Coward]

They already have it's called Sony 0lux.

Schroedinger's Cat: The Secret Revealed!

[LittleGuy]

It's a dog.

Not such a good idea...

[wardomon]

I called the phone number listed in the article. Now the website and his phone have been /.ed! That really sucks.

only with special holographic-quantum luggage

[xlurker]

• According to the scheme, the inside of chamber would be designed
  to detect the time when a photon hits the wall but not where it hits.

hey! this wont't work with any random luggage...
this only works with special luggage that can detect when a photon hits its inner lining...

Can't see inside solid objects

[plshoberg]

The photons merely bounce off the surface of the object and hit the detector wall. The reconstructed image is therefore only the surface contours of the object and not the contents, if any. Would likely have to use a different matter beam to peer inside baggage.

Re:Quantum Holography

[elmegil]

"Far more sensetive than anything that exists today"? According to the article, the researchers claim that there are "no technological hurdles". Which is right?

Dunno if their idea works...

[jd]

...but I get to check two boxes in Slashdot Buzzword Bingo. Just a few more to go....

Re:Dunno if their idea works...

[Anonymous Coward]

Oh please please make up some rules for this ... set up a little sheet every morning when I come into work ... and see if get bingo by the end of the day ... God work would be like that much more fun then!

Re:Dunno if their idea works...

[jd]

Slashdot Buzzword Bingo, for today:

You can pick only one of the following lists, which you should write down in a checker/chequer pattern on some paper. For each row or column, you score 1 point. The first full-house wins. If nobody gets a full-house, then highest score wins.

Card 1: Digitati, Quantum, Holodeck, Spooks, Jon Katz, DMCA, Conspiracy, Amazing, X-Box

Card 2: Microsoft, IBM, SGI, Red Hat, Oracle, Sun, Nintendo, Gartner Group, Linus Torvalds

Card 3: Broadband, @Home, Wireless, DoS, Viruses, Security, Encryption, .NET, Felton

No Technological Obstacles?

[Myriad]

For the moment, quantum holography exists only on paper. But the researchers assert that there are no technological obstacles to the proposal, and they hope to begin building an experimental system soon.

Correct me if I'm wrong here, but according to the article this process relies on quantum entanglement. As far as I know this has never been achieved on a large scale - only in single pairs.

As I see it here this would require two lasers to be emitting entangled beams. I've never heard of a way this can be done. Without, as far as I can see, this process would not work. Seems to be a rather large sticking point... though I don't know how many photon pairs they actually need out of those beams. Anyone know more about this?

None the less, the theory is 'spooky' indeed.

Re:No Technological Obstacles?

[UCRowerG]

Correct me if I'm wrong here, but according to the article this process relies on quantum entanglement. As far as I know this has never been achieved on a large scale - only in single pairs.

IANAPhysicist, but...
Doesn't the uncertainty principle and the whole probability function idea of quantum mechanics suggest than a single photon pair would be all you'd need for the whole object? Theoretically, you could superimpose the probabilities of it bouncing off every single surface of the object at once to get the whole thing. The article mentioned that they would measure when the particle hit the sphere, not where, so that measurement wouldn't disrupt anything.

Now how do they extract and superimpose all those probablilities.

Re:No Technological Obstacles?

[nerdlyone]

Quantum entanglement has been accomplished en masse, and recently (though I can't seem to find the reference right now--try physics news update for the past few months).

And I don't think they would need two different lasers emitting entangled beams. One laser could have its beam split, same as in normal holography.

Re:No Technological Obstacles?

[ajmarks]

Once you note the photon's collision with the chamber, you colapse its wavefunction. Because of this, one can only get a single reading per photon (unless of course the chamber is partially reflecting, but that's a different matter). In order to get the shape of the entire object, they must get those probabilities by shooting a large number of photons at the object.

Re:No Technological Obstacles?

[bloggins02]

Never been achieved on a large scale? What about 1 trillion atoms? Correct me if I'm wrong, but 1 trillion sounds like a pretty large number to me :)

Did they charge $4.99 a minute for the call?

[Tenebrious1]

They can make a bundle, pay off the technology. I hear Madam Cleo is having problems with the psychic network, maybe the scientists can get her to work for them.

Airports?

[Legion303]

Screw the airports. Send one of these to the admin of www.xxxgirlsongirls.com stat!

-Legion

Re:Airports?

[diesel_jackass]

of course! as we all know:
No technology will ever succeed unless it can also be used for porn.

Re:Airports?

[Anonymous Coward]

Then you really will be able to see her kidneys!

Re:Airports?

[Anonymous Coward]

Uhhh... wouldn't you want to just see what the ball is in, not what was in the ball at that point?

What it's used for?

[thelenm]

It seems like this type of device would be more useful when you know what's in the sealed container and want a holographic image of it. So maybe you have an Xbox controller and you want to send someone a holographic image so they can see how huge it is. But since you need one of these special compartments, I don't think it will be very useful for seeing things inside any old container, such as checked luggage. Unless I misunderstood how this thing works?

This could be used to fight terrorism

[dfeldman]

Currently, we are at war with an enemy we cannot see who lurks within our borders. Our lawmakers want to try to find this enemy by relaxing the government's self-imposed limitations on searches and seizures, so that it is easier to determine whether a given individual is carrying items that may be used in an act of violence.

This technology could change everything. Rather than giving law enforcement officers the right to search and harass individuals who fit a "profile" (which, by itself, tends to favor searching Arab and other Middle Eastern types), the government could instead mandate the use of a holographic device such as the one described in this article. The advantages of this approach is that it is not invasive (people will not be embarrassed or inconvenienced by needless searches) and that it would be more effective because it could quickly be used to scan, say, every bag or container in an airport.

This sort of device would also render body cavity searches obsolete. Rather than training LEOs to probe peoples' orifices in a vain attempt to find drugs or weapons, people could be seamlessly screened as they enter "sensitive" buildings. These devices would do for terrorism what store security cameras did for shoplifting: nearly stop it dead in its tracks.

I, for one, would rather see law enforcement widely deploy these devices, rather than subject me to degrading searches. Certainly the majority of Americans feel the same way. We can have our cake and eat it too.

df

Re:This could be used to fight terrorism

[czardonic]

These devices would do for terrorism what store security cameras did for shoplifting: nearly stop it dead in its tracks.

Shoplifting has NOT been stopped dead in its tracks, and certainly not because of security cameras. In fact, shoplifting is still vastly more common than terroism, despite the fact that it is an enemy that we CAN see.

Re:This could be used to fight terrorism

[FlowerPotAdmin]

Think for a moment which is worse: to have the government searching you in broad daylight, where everyone can witness, or to give that government the power to search you at any time it wishes, with neither consent nor notification?

I for one do not feel the same way. In my mind, this kind of "secret" searching is just as degrading, and does not provide as much protection for the citizen.

Re:This could be used to fight terrorism

[Anonymous Coward]

Wow.
You didn't even read the article! Did you?
Thats not just some magic device that can scan everything. You need a lot of special setup. (The item has to be in a special container...)

damn karma whore

Re:This could be used to fight terrorism

[Anonymous Coward]

Exactly, now all we have to do is require terrorists to use spherical luggage that detect when photons hit the inside wall...and fill their body cavities with these spheres also...

you're so smart!

maybe you should read the article before you comment on it...

This is crazy

[CmdrTuco]

I don't understand; you measure one of the entangled photons and thus know what is happening to the other, even though it may be quite some distance away. This is like being able to tell that twin A is wearing a red shirt in Bombay because you see twin B wearing a yellow shirt in New York. How is this information or state transferred between the two particles?

Re:This is crazy

[nerdlyone]

That is the spookiness of quantum mechanics. See here for a summary of quantum teleportation using entangled particles.

Re:This is crazy

[MacDuff]

Knowing the particles are entangled is extra information. If I know bits A and B are either both 0, or both 1 (fully entangled), and I observe bit A to be 0, I know B is 0. No information or state is transferred between the two particles after the initial entanglement.

This can still be performed if, for example, bits A and B are on different HDs, and I ship one across the country. Suddenly, by reading one, I can tell someone across the country what they will read at the address where their bit is on the disk.

Some info for those that don't know...

[Mustang Matt]

http://www.sciam.com/explorations/061796exploratio ns.html

http://users.ox.ac.uk/~jsw/Schroedinger.html

umm.. If we read the article.

[loraksus]

. . .
propose to create holographic images of objects concealed in a spherical chamber. Ideally, a small opening in the chamber wall permits light to enter, but lets no light out. The photons in a beam of light directed through the hole scatter from the enclosed object, and ultimately strike the inner wall of the chamber (see figure).

So it's not sealed, but a small opening. I dunno if I want people making holes in my luggage.

Re:Quantum Holography

[GSpot]

Wow Doc Brown! Nice to see you worked in the "fulx capaitor" AND "dilithum crystals" in the same post.

All you need to get the trifecta is to power this baby with a "Mr. Fusion."

Out.

What's That?!

[Renraku]

"Look! I think its a bomb!"
"Sure does look like one..seize her!"
Five minutes later.
"There was no bomb in here..WTF?"
"It would have been in there if we hadn't looked!"

Re:Quantum Holography

[Anonymous Coward]

I would guess that the dilithium crystal/flux capacitor guy was joking, since both of these things are fictional. Of course, there are "no technological hurdles" to all kinds of impractical things - like laying dominoes from New York to LA.

Re:Quantum Holography

[xlurker]

but what is the technology good for?

If one has to actually first put the object into the sphere, then one (obviously) already has a quite good apprehension
what it looks like...
unless one wants to "see" something that was "created" while in the sphere...?

Oops

[Mustang Matt]

Correct link with no space!

Got to love a Troll!

[Dante]

you need to work on the content though.
Please mod it as a troll.

In Airports? I think not...

[cscx]

Could it lead to quantum luggage scanners at the airport?

I don't believe so. I personally feel the problem with airport security is not the type of equipment used, but the incompetence of some of the security people employed there. You've heard the security breach stories on the news.

"What is that, a hairdryer with a scope on it ?... That looks okay, keep it moving". "Some sort of bowling ball candle ? That's fine, just... we don't want to hold up the line, don't hold up the line"
Jerry Seinfeld on Airport Security

Re:In Airports? I think not...

[furiousgeorge]

"How about this crack squad of savvy, motiviated individuals?"

Luggage detectors of tomorrow

[imrdkl]

In a few years, they wont even need to open your suitcase, just put on VR helmets with the passenger and ask them to explain every piece of luggage as it rolls by on a VR conveyor belt, after being unpacked with detectors and fast graphics cards.

Sure makes repacking a breeze!

Applications?

[base2op]

Forget detecting cancer and airport security. Imagine what this could do for voyeur pr0n! : P

And speaking of psychics, why do I know that the only people that'll read this post will be browsing at -1?

We can already "scan" everybody

[Anonymous Coward]

I don't have a link but it uses a very short-wavelength radar to perform the scan. Anything that isn't flesh shows up quite nicely. Why aren't they being used? Too expensive. I guess the cost of implementing these is more than the loss of several airliners and a few buildings.

Re:We can already "scan" everybody

[boydtel]

Um... they are not being used (to "scan everybody") because you have a constitutionally protected (for now) right to a reasonable expectation of privacy. Lets not go suggesting this stuff! Millimeter radar is used though in some of the baggage screening machines.

Re:We can already "scan" everybody

[Anonymous Coward]

The device looks just like a metal detector booth. You step into it, the operator pushes a button, and the radar image appears on a monitor. What's the difference between the radar and metal detector, constitutionally? Not much, I'd think. As far as rights of privacy goes, make sure the operators don't get to see the people as they pass through, only the radar image. That way whoever is seen on the machine is anonymized. Unless of course, they have something on their person they shouldn't have (knife, boxcutter, or worse).

Faster than light communication

[pete-classic]

I don't really understand quantum entanglement but . . .

Couldn't you use it to communicate instantly over any amount of distance?

Imagine:

You are at point A (say, earth) and I'm at point C (say, a spacecraft) and we have a buoy, at point B, precisely half way between us. Let's say that you and I are one light-year apart, and that buoy has been splitting a beam of photons between the point where I am and the point were you are for the last six months.

You have a photoreceptor oriented 90 degrees out from the beam, and I have a mirror at 45 degrees, hooked up to a solenoid. I type you a message in morse code on a switch that controls current to the solenoid. You see it in real-time.

I'm sure that either 1. there is a really good reason why this won't work in theory or 2. someone else has proposed it.

Can someone give me a reference either way?

-Peter

Re:Faster than light communication

[Anonymous Coward]

On first glance, the problems seem to be:

1) Power -> Bouy solenoid will take more than 1/2 light year to get there.

2) the device works by measuring the time it takes light to strike surface. Therefore it is limited by the speed of light. You probably would be better off sending a radio signal...

Re:Faster than light communication

[Anonymous Coward]

perhaps this stuff will become subspace communications.

Re:Faster than light communication

[SeanCier]

I don't have a reference for you, but I can say that no, quantum entanglement does not allow FTL communication. To do anything interesting, you need to communicate information about the observation you made on one of the particles. Imagine twins -- one male, one female. They go to the two poles; at the North pole, somebody looks at one, and *boom*, she's female and the other one is male -- instantly. The people at the South pole look a microsecond later, and see that their twin is male. Okay... so? The people at the North pole haven't transmitted any information, even if the action occurred *instantly*.

The article doesn't make it clear, but the measurement taken in the chamber must, I have to assume, be transmitted and used in constructing that second image (it doesn't just *happen*; you can't shine a beam of light, even entangled photons, and expect them to magically scatter off nothing. When the first entangled beam is measured, quantities of the second half are determined, but that doesn't make them scattered, since it was *possible* they were in that state already... it has to be possible, that's how quantum physics works). It sounds like the information would be used in a second beam interfering with the intangled beam, but I'm not certain from the article... but I can guarantee that information has to be used.

Re:Faster than light communication

[Mr. Slippery]

Couldn't you use it to communicate instantly over any amount of distance?

No, you couldn't. :-)

Your mirror scenario wouldn't be making any measurements on the incoming photons, I don't see that it has anything to do with entanglement.

Let's look at another example that gets closer to - but turns out not to be - instantaneous communication. It's been a while since I studied this, so real physicists please correct me, but I think I remember the gist of it.

We'll use polarization as an example. Quick review: every photon is polarized at some angle. If it hits a detector that's at the same angle, it passes though; a detector at 90 degrees to its angle, it's blocked; and at some angle in between, it may or may not pass through, but if it does it will now have the new angle of the detector (i.e., a 45 degree photon hitting a 0 degree piece of polarized material has a 50% chance of being blocked at a 50% chance of passing with its polarization at 0 degrees).

The polarization vector is a quantum superposition of the 0 degree and 90 degree states. If two photons are entangled, and one gets measures and "snaps to" one of these states, its entangled partner always "snaps to" the same state. (Or maybe it always snaps to the opposite state. I forget. Doesn't matter for this example.)

Let's say that our entangled photon source is sending out beams that are polarized at 45 degrees (i.e., in a superposition of 0 and 90 degrees). The sender - call her Alice - sets her polarization detector to either 0 degrees (to transmit a "dot") or 90 degrees (to transmit a "dash"), and her photon randomly snaps to one of these polarizations. If it happens to snap to the matching one, it passes thru the polarization detector.

A light-year away, the matching photon in the detector belonging to the receiver (call him Bob) spookily snaps to the same polarization direction. Bob's all set to make a measurement, but which way should be set his polarization detector? If he sets it at 45 degrees, then regardless of whether the photon is at 0 or 90 it has a 50/50 chance of passing through, so he'll see half the photons pass. If he sets it at 0, the incident photon has (from Bob's perspective, not knowing whether the next bit of the message is a "dot" or a "dash") a 50/50 chance of being polarized at 0 at 90 degrees, so he'll see half the photons pass. Same if he sets it at 90.

Even though the photons were linked, and each instantaneously "knew" what was happening with the other one, no information can be recovered from the beam, because what the photons do is still random.

(However, by changing this around a little bit Alice and Bob can generate an unbreakable cryptographic key - search Google for "quantum cryptography".)

Re:Faster than light communication

[achurch]

I have practically no background in quantum physics, but:

Couldn't you, say, devise a system where each "bit" of information was transmitted for a certain length of time? After all, this is basically a serial communication system, so as long as you know the time for a bit, you wouldn't have to know the polarization of every single photon passing through--you could just catch the 0-degree (or 90-degree, either way) photons, and assume that when you weren't getting photons then they were all polarized the other way, giving you a bit of the opposite value.

Or so it seems to my simple mind, anyway... is there a reason this wouldn't work?

Re:Faster than light communication

[redcliffe]

If think you have this wrong. If I have an entangled photon emitter located precisely half way between my two stations. It emits beams of entangled photons towards each of my stations, Alice and Bob.

Alice changes the polarisation at that end to 90 degrees. Simultaniously the other photon of the pair at the other end changes to 90 degree polarization. In this way communication can be acheived.

You just set up on the reciever end a lens that only accepts light with 0 degree polarization. Thus when the other ends sets the polarization on the photon pairs to 90, your end blocks light, and you've now got a 0. If the other end has set the polarization of the pairs to 0, light will pass through your lens, and you will have a 1. This allows you to transmit binary instantaneously, but requires the entangled photon emitter to be exactly half way between the two stations. If it was say 2% out of position, over a distance of 1 light year, your signal at the reciever end would arrive 0.02 years late.

I am not a physicist, but this is what I understand based on my reading of various works on quantum entanglement and teleportation.

Re:Faster than light communication

[salo]

No.

This concept was originally conceived sometime around 1930 by einstein, podolsky, and rosen as an argument intended to torpedo quantum mechanics.

basically they pointed out that quantum mechanics predicts that if you prepared a four state quantum mechanical system (ie 2 qubits) in a certain way (creating an EPR pair) they would exhibit "spooky action at a distance". at the time it was a fundamental principle that cause and effect had to obey the speed of light and therefore quantum mechanics was broken.

turns out there is massive amounts of evidance that cause and effect can be instantaneous over any distance and quantum mechanics goes on to be the most succesful scientific theory in history.

the scenario is this: alice and bob create an EPR pair, and then each takes one to opposite ends of the universe. when alice measures the state of her qubit, bob's qubit instantly becomes a known quantity.

it has been proven that to use this effect for communication requires the communication of classical bits of information (i believe it is the result of alice's measurement) which are governed by the speed of light. hence quantum entanglement can not be used as a truly instant messaging transport.

however, you can use this effect to achieve perfectly secure cryptographic key distribution and this has actually been done several times.

quantum computing is super cool and might actually be practical. check out http://www.qubit.org for some well chosen tutorial papers and links.

Re:Faster than light communication

[Mr. Slippery]

Alice changes the polarisation at that end to 90 degrees.

How? Alice can't reach out and twist that photon. All she can do it rotate her detector, and the photon may or may not - the probability depending on its incident polarization - pass thru and take on the detector's polariztion. That randomness is what makes it impossible to pass information in this way.

Re:Faster than light communication

[redcliffe]

If you change an entangled photon in any way, the other one instantly changes the same way. That's what confused Einstien. Quantum nonlocality, you change one half of the pair here, and instantly the other half changes the same. That's what entanglement and teleportation is all about, IIRC, but IANAP.

David

P.S. Of course, I could be wrong. Any quantum physicist out there wish to confirm this. I'm sure this is what they did in the Bell experiment.

Re:Faster than light communication

[Mr. Slippery]

If you change an entangled photon in any way, the other one instantly changes the same way.

It's more correct to say that if one entangled particle changes, the other changes too. But that only helps you do instantaneous communication if you can change an entangled particle in exactly the way you want. No one's figured out how to do that.

As far as we can tell at present, quantum nonlocality and "spooky action at a distace" exist, but cannot be made to transmit any information.

Looking at a paper I did about ten years ago, I found the following quote from Nick Herbert's Faster Than Light that summarizes the situation:

Eberhard's proof applies to the quantum patterns...[it] guarantees that large-scale quantum patterns will never be observed to be connected faster than light. Bell's theorem, on the other hand, applies to the individual quantum events themselves, and proves that these little quantum jumps must be connected faster than light...Bell's theorem can coexist with Eberhard's proof because they each refer to different aspects of a quantum measurement. Bell's theorem...can also exist with the COP rule forbidding all superluminal connections that can be used for signaling, because these Bell-mandated FTL jumps occur in an utterly random manner.

Re:Faster than light communication

[Tony-A]

The question is whether or not Bob can discern whether Alice is detecting photons (plural) with horizontal or vertical polarization. If he can, then Alice can communicate to Bob.

Re:Faster than light communication

[simon_cockle]

No.

Your example didn't appear to use entanglement but if it did then all you would notice is different random noise to the random noise you would have otherwise received.

You wouldn't be able to make any sense of the new random noise unless you knew the message which was being transmitted. Once you knew the message you could interpret the noise as being the message correctly. But it wouldn't be much use then...

Re:Faster than light communication

[supruzr]

You're essentially right. Although the message (in the form of polarized photons) HAS travelled instantly from an arbitrary distance thanks to the magic of entangled photons, Bob can't determine the message unless he knows which way to orient his polarity detector. So, ironically, he needs to know the message before he can read the message. And to answer your question, I believe that entangled photons always have complimentary polarities.

Re:Quantum Holography

[Anonymous Coward]

I think the idea is that you could then look inside the object that's in the sphere without actually having to take a chainsaw to it.

OT Spheres

[Amazing Quantum Man]

So unless someone is stupid enough to try and sneak a bomb onto a plane in one of these spheres, it's not much use to the security guards

Reminds me of the old joke...

In the early days of Rocket Science(tm), they were trying to figure out how to protect the astronaut from acceleration. So they hired one of the leading physicists of the day to investigate.

A month later, he came back with a solution. He got up in front of the NASA bigwigs, and said, "First, assume a perfectly spherical astronaut..."

Re:OT Spheres

[wass]

Did little story this come before the spherical cows?

My psychic prediction

[schnitzi]

I predict that, far from scoring a point for physicists over psychics, this technology will be used as fodder for psychics as a possible explanation for how remote viewing might have an actual basis in real science.

It doesn't matter that they don't understand the mechanisms behind the proposal.

It doesn't matter that this technology requires extra apparatus that wouldn't be there for a human doing remote viewing.

It doesn't matter that they have not yet firmly established that remote viewing even exists.

If people want to believe in something enough, anything that sounds like supporting evidence will be accepted.

More impressive than 3d

[pete-classic]

You can get an idea of what something is shaped like in more conventional ways. Like X-ray.

What is really impressive is that they can see what the surface of a flat object, like a photograph, looks like. Neat!

-Peter

The True Effects of Quantum Computers

[Klerck]

First, I'd like to point out that quantum computation and quantum encryption are two almost completely separate concepts. Quantum encryption is based on the fact that quantum states cannot be measured without altering. The most common example is the polarization of a photon, but it will work for any quantum state, so long as there exist, effectively, two unique states that can transmit the data.

Quantum computation, however, is much more complex and much more interesting. Quantum computers are based on the concept of quantum entanglement, the ability of a quantum state to exist in a superposition of all of its mutually exclusive states: It's a 1 and a 0. However, this is not as easy to use as one might think. While it's true that if you have n quantum logic gates you have the ability to input 2^n data values simultaneously (as opposed to only 1 piece of data if you have n digital logic gates), this is not going to be the end of classical computing for a few reasons. First, quantum computers have to be perfectly reversible. That means for every output there's an input and vice versa. And there has to be no way of knowing the initial states of the data. You don't process data, you process probabilities in a quantum computer; if you know exactly what any one value is throughout the computation, you can find out all of the values: the superposition ends and you're stuck with a useless chunk of machinery. This means YOU CAN ONLY GET ONE RESULT FROM ANY QUANTUM COMPUTATION, THE END RESULT. You can't see what the data in the middle is or the computer becomes useless. (Landauer's principle makes heat loss data loss. When your processor gets hot, it's losing data. If the same thing happened to a quantum computer, it wouldn't be quantum anymore.) Decoherence is what happens when you randomly lose data to the environment by design, not by choice, and the superposition ends. This is bad for Q.C. Oh, and quantum computers can only do *some* things faster, like prime factorization and discrete logarithms. Not multiplication or addition. Plus, the circuits that would do basic arithmetic would be bigger and slower than what you've currently got.

So what does this all mean? It means that quantum computers are going to provide some advantages (real quick big number factorization), and some disadvantages (that whole RSA standard). The most realistic initial use of quantum computers will be as add-ons to existing super-computers to resolve certain types of NP-Complete headaches that regular math can't simplify yet. At best they will someday be an add-on to your PC; but they will never replace the digital computer.~

If you want more info, check out ahttp://www.qubit.org, it's got some decent tutorials.

Re:The True Effects of Quantum Computers

[Anonymous Coward]

Where the hell is the humor in this?

I want some damn new penis bird stories, maybe say that cmdrtaco was found dead or some other such non-sense.

This is just silly Klerck!

Schroedinger's Cat needs a better box, that's all

[Westacular]

No, we're looking at both. The inside of the sphere is a big optic sensor that records the time each photon hits it, which is compared to the time its mate hits the normal detector.

With regard to Schroedinger's Cat, this is really no different than x-raying the box: its effectively the same as opening the box.

Re:Quantum Holography

[Anonymous Coward]

I am completely wrong, never mind.

But it'd sure make online shopping that much better - see the object in 3D with 100% accurate detail...

You can't make a civil libertarian happy

[Anonymous Coward]

When cops pull over black people because they "look suspicious", the ACLU whines that they don't have probable cause that they're guilty and they can't do that.

When cops use a scanning device so that they only pull over the guilty people, civil libertarians keep whining, but make up a new excuse as to why they're helping the criminals out.

So my question to you is: how do you expect law enforcement to be effective if you strip them of all of their crime fighting tools?

Re:You can't make a civil libertarian happy

[FlowerPotAdmin]

Simple. You look at the problem from another angle. Instead of fighting crime after the fact, try focusing on prevention. Happier citizens = less crime. Of course, that would require a government that actually responded to the needs of its people -- and we couldn't have that, now could we?

You can see through any object

[Anonymous Coward]

If you pass two beams of energy through an object at perpendicular angles then onto walls that would detect timing you could theoretically monitor inside objects by the amount of extra time it takes for the beam at the intersections to hit the monitoring walls.

In the instance of metal, the beam would bounce back. In the instance of clothing or other materials the beam can pass through, the small change in the time it took can create a 2D image at least.

Re:Quantum Holography

[Anonymous Coward]

Perhaps you could borrow such a "laser" from the Alan Parsons project.

Re:Schroedinger's Cat needs a better box, that's a

[the_2nd_coming]

if that is true then it is not real entagelment. I should not have to read what happens to photon a and compair it to photon b to if they were actualy entagled, photon a should tell me what photon b is doing.

Does this allow...

[Explo]

...a new, more efficient porn acquiring method for geeks - because most clothes are not entirely opaque and some light gets to the skin, can this be used to acquire 3D nude holograms of fascinating females that pass by?

Re:Does this allow...

[ostawookiee]

So can they shrink the technology so it fits in a pair of "x-ray" goggles?

Think of the porn!

[jawad]

Wow, all the ideas going through my head are just amazing me. Thieves could use this to see if someone's in a house, and slashdotters could use it to broadcast live porn!

Link to the real thing.

[HughsOnFirst]

Here is a link to the
actual paper itself. It's a PDF file though

Damnit!

[nanojath]

Yeah yeah, it's all funny but it ticks me off that nobody is pointing out that The principle illustrated in Schroedingers "cat" thought experiment are NOT THE SAME as the Heisenberg Uncertainty Principle. In fact, it ticks me off that nobody knows what the Uncertainty Principle is really about and people constantly confuse it with the whole indeterminate quantum particle state and whether does in fact create quantum indeterminacy on the macro scale (if a tree falls in the forest...) issue. Heisenberg's Uncertainty Principle establishes a mathematically defined absolute uncertainty balanced between the momentum and position of a quantum scale particle. The corresponding thought experiment would be the gamma ray microscope.

Re:Damnit!

[nerdlyone]

Who the hell modded that one as "5: informative"? Informative about nanojath being pissed off maybe. Not informative about science. Just my opinion.

Hologram of a suitcase :-/

[karot]

OK, So we put a suitcase into one of these things at an airport, et VIOLA!...

... a hologram of a suitcase! Methinks this one will need work before it replaces the good ol' Airport Xray machine.

Of course quantum entanglement is also how "they" propose to achieve the matter-transporter, so forget looking inside the luggage, we can just send it on ahead :-)

Re:Hologram of a suitcase :-/

[Jburkholder]

>et VIOLA!...

Ah yes, the most-often overlooked of stringed instruments! Mind you, I like a nice cello, myself.

Re:Hologram of a suitcase :-/

[Anonymous Coward]

dumbass

he meant voilà not viola

i solved that one long ago

[Unknown Poltroon]

COurse, the cat werent too happy.....

Re:Quantum Holography

[Halloween Jack]

While the concept behind the technology is sound, we don't yet have sufficiently advanced hardware to complete a working demonstration...Such a motor would need to have an imbedded flux capacitor

Still zipping around time in that hopped-up train, Doc Brown?

Until dilithium crystal lasers become more widespread
Or is that Scotty? Is it mere coincidence that "Prakash Kothari" is an anagram for "A ha, Kirk has port!" University of Ouagadougou, indeed... more like Starfleet Academy.

Total Perspective Vortex

[PyroMosh]

Reminds me a lot of the Total Perspective Vortex from Douglas Adams' The Restaurant at the End of the Universe.

Life imitating art (loosly). DNA, I think would have been plesantly amused to see this.

Re:Total Perspective Vortex

[PyroMosh]

Oops, never mind. I didn't realize they were sending out an active signal to do this with. That's what I get for just skimming the article, I guess. ( :

4th Amendment conflicts with quantum physics

[Anonymous Coward]

First the law of relativity conflicted with quantum physics and now this?!!$#!
Anyway, since your "stuff" exists not just in your house, but everywhere... does this mean that a sphere built around your house can search your things without your permission? If congress can't figure out the Internet, there's absolutely no hope in them even touching this.

Your wifey

[Crufty Crotch]

Trust me, friend... your wife is definitely cheating on you. She just loves my crufty balls.

Similar stuff

[SanLouBlues]

a tad OT, but: Text search for GUENTER NIMTZ on http://www.pbs.org/wgbh/nova/transcripts/2612time. html Similar, but not the same . . .

The real significance:

[Nindalf]

The given example apparatus would not be a practical device in any way. It needs a way to allow photons in, and could just as easily allow photons out; additionally, the inner surface of the sphere needs to be a photon detector with very precise timing. It doesn't see anything a camera inside the sphere couldn't see.

This is about exploring quantum entanglement. When lasers were invented, nobody knew what to do with them. Everybody thought "Death ray!" which was pretty silly in retrospect; that's a minor application. Then, bit by bit, they found thousands of ways to apply them that revolutionized all sorts of practical devices and allowed entirely new ones.

Developing this would be breaking old rules about what is and isn't possible, and though it's hard to guess exactly what it's good for, you can bet it'll be good for some amazing new technologies.

background information about holography

[tcc]

For those of you interrested in holography:

Holography basics (aimed at Highschool students level).

Books and information on Holography

Some more holography Theory>

Meow

[Kenshin]

If the cat meows, would that break the uncertainty principle?

Re:Meow

[Faramir]

No. At this point, there is no established physical way to "break" the uncertainty principle. I'm not sure why it is not the "uncertainty law" at this point--perhaps this is a subtlety of the way the principal was derived. Nevertheless, it has the tenacity of a law of nature, and will not "break". The equation will not be violated--the uncertainty (or change) in position squared times uncertainty (or change) in momentum squared will alwasy be greater than or equal to Plank's constant divided by 2 (dx^2 * dp^2 >= hbar)

Re:Meow

[Anonymous Coward]

Stephen Baxter wrote a good story about some aliens trying to get around the limits imposed by hbar on computing and thermodynamics by recreating the original state of the vacuum, before it went through the phase transition into our vaccuum. Since the relative streangths of the four basic forces are thought to have been more or less a random outcome, they kept on trying until they managed to get hbar to be zero, at witch point you can have infinite processing power. Of course, things don't quite go as planned. The story is from the book Vacuum Diagrams, a book that imho defines the genre of hard science fiction.

Re:Quantum Holography

[Anonymous Coward]

So we're finally getting around to building E. E. Smith, PH.D's "spy ray" (see the Lensman space operas, first published during the 1930s).

Deceptive Summary

[claytronics]

If you look closely at the diagram and article, it does NOT allow you to see objects hidden inside a container. It can see only completely uncovered objects placed in a special, light-sensitive sphere with a hole to let light in. So much for "objects sealed in closed containers"...

Alas, it was too cool to be true.

Take a closer look

[meatpopcicle]

IT JUST CREATES A 3D IMAGE OF A 3D IMAGE!
-theres no X-Ray vision here! For luggage they would be able to say "I think its a suitcase"
-it does seem "spooky" though
-it does have potential uses that could be really cool. Remote surgery, biometrics, 3D video

Actually...

[db48x]

You forget that X-Rays are just a high frequency form of light, and are therefore 'made' of photons, which means that they can probably see into things as well. So yes, a baggage scanner where the bags pass into their chamber would probably not be much trouble, though obviously not something they'll shoot for right off the bat.

Gamers Rejoice...

[darrad]

I can see it now, you climb into a cylinder and fire up the latest edition of Quake...and you are IN THE GAME...the holographic device scans your image and places it into the game, and the output is projected to the walls of the cylinder....talk about a total 3d immersion.....

Re:Quantum Holography

[Anonymous Coward]

nice try. but i can assure you that 0.15 um accuracy movement is easy to do. you can even buy such actuators "off the shelf". try something like 0.15 pm next time (1 pm = 1e-12 m).

Alas, I doubt it

[epepke]

People have been trying to do something like this for 60 years with ideas as clever as yours and some more clever, entirely without success.

What happens is this. There's definitely a correlation. However, the correlation only shows up (i.e. you can detect it) when you take the signals from two or more detectors and, by some more conventional means (like wires) and correlate them. If you only look at one detector, all you ever see is random noise.

This is why people call it spooky. If it were just faster than light, there wouldn't be much of a problem. However, it appears to be correlated, but not at all in the way that our intuitions about causal relationships make much sense of.

I've been looking for a good popular book on QM weirdness for years and haven't found one that's really compelling. The closest I've seen is In Search of Schroedinger's Cat.

One of the definitive experiments that showed that quantum weirdness wasn't due to hidden local variables was Bell's Inequality, which was done in the 1960's. A description of that is in this book.

On the other hand, maybe it's OK that QM is so weird. One of the results is that quantum cryptography is possible. (I believe that the record for distance is about 10 kilometers now.) Using single photons to transmit a message in a certain way, you can ensure that nobody can eavesdrop on the transmission at all without your knowing about it. Of course, it's easier and simpler to bribe the recieving party anyway.

Quantum Consciousness

[Anonymous Coward]

What's really spooky is that some scientists believe that the brain itself is a quantum device. They theorize that the source for the brain's quantum experiences come from the microtubules that seem to function as the nervous system for cells. They believe that they have detected non-local-quantum-field modulations from these microtubules. Some quantum computer chips designers even base their designs on the characteristics of microtubules. The cytoskeleton microtubules are common in nerve cells but can be found in all cells in all animals.

Over 1,700 pages on this topic.
http://www.alltheweb.com/search?cat=web&advanced =1 &type=all&query=microtubules+quantum&jsact=&lang=e nglish&charset=iso-8859-1&wf%5Bn%5D=3&wf%5B0%5D%5B r%5D=%2B&wf%5B0%5D%5Bq%5D=&wf%5B0%5D%5Bw%5D=&wf%5B 1%5D%5Br%5D=%2B&wf%5B1%5D%5Bq%5D=&wf%5B1%5D%5Bw%5D =&wf%5B2%5D%5Br%5D=%2B&wf%5B2%5D%5Bq%5D=&wf%5B2%5D %5Bw%5D=&dincl=&dexcl=&age=&size%5Bp%5D=%3C&size%5 Bv%5D=&size%5Bx%5D=0&hits=100&nooc=off

Photosensitive Sphincter: anyone read the article?

[NickFusion]

Good lhord, did anyone actual read the damn article? Here's a clue: No.

The technology described will not scan your luggage, nor will it make body cavity searches obsolete, unless you have a spherical, photosensitive rectum.

Not a cure for cancer, or a replacement for a cat scan or MRI.

What the technology excels at is showing you what's inside a specially constructed sphere. This information could also be garnered with a sufficiently large hammer.

A cool physics party trick, and some interesting basic research. That's about it.

scanning luggage? what?

[dAzED1]

"Ideally, a small opening in the chamber wall permits light to enter, but lets no light out. The photons in a beam of light directed through the hole scatter from the enclosed object, and ultimately strike the inner wall of the chamber."
One of these days, submitters will read the articles they submit. IF you can think of how that relates to a duffle bag on a conveyor belt, more power to you. I mean...I suppose ultimately it could...in like 50 years or so. Goof.

Yes and No

[ArcSecond]

There is a really good book I read about stuff like this a few years ago, called "Schrodinger's Kittens". To sum it up, the guy says there is ANOTHER way to look at quantum weirdness, other than the "Standard/Copenhagen" model.

The idea is that since photons travel at the speed of light (duh), they don't experience "time", and can actually make a "choice" about the path they are going to take, so that an entangled pair of photons "agree" as to where they will be in the future. This has the affect of looking to us like there is an "instantaneous transmission" of information from one to the other, which would violate causality from the standard view. The "choice" is the ability of the photon to "feel out" all the possible paths it could take, and select an event in the future to which to tie itself to. This might be interpreted as a basis for "fate", which is fine by me, since that's the way I lean anyhow.

Obviously (as IANAP) this explanation is worded poorly and not really an accurate representation of the weird math involved. But, while information is "traveling back in time", I don't think there is a practical way to use this effect as a communications medium. Maybe you could have four entangled beams (two each for two observers)?

Probes?!

[TeknoHog]

The uncertainty principle has nothing to do with the nature of measurement, or probes. It is inherent in the quantum system. It is very sad to see this same confusion again and again.

In quantum mechanics, the momentum distribution of a particle is the Fourier Transform of its position distribution. When the position distribution is narrower, the momentum distribution is wider, and vice versa. This is the basic property of FT. In fact there's a simple counter-argument to the probe effect, because when you hit something with a certain impulse and you know the mass of the particle, you can predict how the hit affects its motion.

[Disclaimer: IAAP]

Re:Probes?!

[statusbar]

I like to explain it this way:

Take a .wav file of a sine wave and edit it with your favourite sound editor. Zoom in so you see 100 cycles. Measure the time 100 cycles takes. From that you can calculate the frequency of your sine wave. At what time did this event occur? Well, the event is spread out over time. So we don't know the accuracy of the timing of the event very well.

Now zoom in more so only 1/2 a waveform shows. Measure it. calculate the frequency. You now have more accuracy in the timing of the event, but less accuracy of the frequency.

Heisenberg's principle is NOT the confusing thing about physics - it is plain reality! The thing that really is the source of the confusion is that the energy of a particle is related to its frequency - Just like the time and frequency were related in my example.

*IANAP*

--jeff

Re:Probes?!

[TeknoHog]

Excellent! You have just explained the basic feature of Fourier Transform. The FT is simply the frequency distribution. That strange thing about quantum mechanics, that energy is frequency (and momentum is inverse wavelength), is pretty weird because it obviously applies to photons, but nobody knows why it works with matter particles as well.

More generally, even if we find a 'theory of everything' we probably can't explain exhaustively why it works. For example, Special Relativity is based on the observation that the speed of light is constant for all observers no matter how they are moving, but this fact has not been explained. Of course, it is irrelevant to practical applications :-)

Re:Probes?!

[gpinzone]

You are confusing accuracy with precision. The precision of the measurements increases/decreases when you zoom in. You have no idea if the measurements are an accurate representation of the source wave, nor should you care for the purposes of this example.

Re:Probes?!

[Faramir]

Inherent, fourier, etc., all true. But...

It certainly does have much to do with measurement, probes, etc. This is called practical reality. The theory of quantum mechanics may not care about measurements (that is a anthropocentric term, and QM is supposed to be from the universal perspective, that doesn't know about the human, linguistic, observational perspective), but the users do. And to the users, this is the practical effect.

If I am confused, so are Griffiths, Morrison/Estle/Lane, and Sakarai, who taught me QM I, QM II, and grad QM. Yes, these are basic properties of the FT, but that is not, to my understanding, how we got there, but rather how we justified what we found.

The probe example is obviously highly inaccurate--I thought the use of a pencil made this obvious--but it is generally illuminating to people who have not studied the equations.

[Disclaimer: IAAP too]

Re:Probes?!

[statusbar]

Correct, but even with infinite precision, once you start reducing your viewport to show less than one cycle of data, you can not know the frequency accurately. There isn't enough information. So you can not measure the timing of the event AND the frequency of the event simultaneously.

Zoom in more, so the window is 1 pico second. Great timing accuracy.

But what is the frequency of the single sample? it is a voltage/level now. That information is lost.

position accuracy and frequency accuracy are mutually exclusive.

--jeff

Re:Probes?!

[gpinzone]

The original argument was not about accuracy at all. It was about how easy/difficult it would be to measure the period and frequency of the sine wave. This has to do with precision not accuracy. When you zoom in, the viewer gains precision for measuring the period, but looses precision of measuring the frequency because the sample size is much smaller.

I think the example would have been clearer if he used an oscilloscope rather than a wave editor since the wave editor can measure the waveform perfectly. Trying to measure a sine wave by fitting them in those "little squares" is a better analogy

Re:Probes?!

[TeknoHog]

That's an interesting point about how FT is used to justify observations. The early theories were based around idealized systems, then we used FT to extend them to higher complexity. But in reality, even the original ideals are something complex, so convolution kicks in. And can we really assume linearity, which is required for FT?

I've also tried to argue why the probing analogy is hopelessly wrong. Let's say when measuring the position, you give the particle a nudge to the right. Perhaps you could estimate how this impulse affects the momentum. In the standard QM picture, the position distribution of the particle collapses to a narrow peak - therefore the momentum spreads out, but this happens in both directions, not just to the right.

I admit there's a fundamental problem if you try to estimate the effect of the nudge on the momemtum. Because you'd have to measure the impulse somehow, and you could not escape the cycle of measurements. In any case, the basic QM which is still assumed correct, explains why the nudge is not the source of momentum uncertainty.

Re:Probes?!

[statusbar]

No, my whole original point is that if you are looking at a partial waveform it is impossible to know the frequency of the full waveform.

The 'position in time' is more accurate because you have a smaller window. Your 'frequency' is not accurate because you don't see it all.

All you can say is that the frequency is less than or equal to X, where X=1/(window time).

So there is no measurement here. It is not a limitation of measurement devices.

The point is that a particle or photon's energy is related to its frequency. To know this frequency you must take time into consideration. The longer time window you use, the less you know the position.

The photon/particle does not HAVE an instantaneous energy level!

Heisenberg is not the problem, nor is it specific to quantum physics.

--jeff

Not entirely new...

[Pig Hogger]

It is possible now to view hidden objects by ultrasonic holography... I believe that this process has even been (gasp!) patented more than 25 years ago...

The object has to be at the bottom of a pool filled with some opaque liquid; a transducer is immersed, bathing the object with ultrasound. Sound waves reflect on the object, and they form an interference pattern on the surface, which is lit by coherent light, thus forming a virtual image of the object.

One caveat, though... Given the ***BIG*** difference of wavelength, the virtual image appears to be quite far, and has to be viewed with a telescope...

Ask Slashdot: Explain this in English please!

[jafac]

better type some random text in here to dodge the lameness filter -
disclaimer: this post really was not intended as a troll or a flame - but if you're going to criticise people for not understanding Heisenberg's Uncertainty Principle, maybe you should help those who don't to do so.

Been there, done that...

[Anonymous Coward]

...used 3D color ultrasound 10 years ago to create an image of a fetus...big deal for this announcement today.

Been There, Done That

[NeuroManson]

And at FAR below the price (even the alleged 'Hologram' arcade game from Sega in 1991 or so was based on the same principle):

http://www.exploratoriumstore.com/miragemaker.ht ml

Original article

[Vadim Makarov]

I'm surprised nobody put a link to the original article.

Abouraddy,A., Saleh,B., Sergienko,A., and Teich,M. Quantum holography (PDF, 169KB, 8pages), Optics Express, 9, 498-505 (2001).

Read the damn thing (if you can :-)), then discuss.

Hit the lights

[Anonymous Coward]

Metallica - Hit The Lights

No life till leather
We are gonna kick some ass tonight
We got the metal madness
When our fans start screaming
It's right well alright
When we start to rock
We never want to stop again

Hit the lights
Hit the lights
Hit the lights

You know our fans are insane
We are gonna blow this place away
with volume higher
Than anything today the only way
When we start to rock
We never want to stop again

Hit the lights
Hit the lights
Hit the lights

With all our screaming
We are gonna rip right through your brain
We got the lethal power
It is causing you sweet pain Oh sweet pain
When we start to rock
We never want to stop again

Hit the lights
Hit the lights
Hit the lights

Uncertainty principle

[haruharaharu]

Basically, a quantum particle - like an electron - exists in a somewhat undefined state. Its location and energy are not fixed, but exist more as a set of probabilities. These probabilitiy fields are calculable and are the basis for electron shell level/sublevel 3d models.

The thing that makes all this interesting is that the certainty that a particle's position and energy level can be determined are limited. The more you define one, the fuzzier the other gets. This is not an observational thing, but an intrinsic property, as has been demonstrated by cooling some Cs atoms to

What Schroedinger's cat is all about is the fact that quantum state (the probability cloud) does not collapse until observed. I suppose that means interaction, though Physicists keep calling observation. The cat is representative of some quantum particle in an indeterminate state. It wanders between quantum energy levels until you observe it. Then the quantum state collapses into one of these levels and interacts. This also has been confirmed (the weird travel in between adjacent energy levels) - Some scientists found that they were able to keep a group of atoms from changing energy levels by constantly observing them, whereas another group, which was observed less frequently, did change levels.

Quantum Holographic Projection Display

[Anonymous Coward]

Quantum Holographic Projection Display
QHPD

Uhh...

[Anonymous Coward]

One thing that's not uncertain: You, my friend, need a woman.

I used to drive a Heisenberg mobile...

[jazdc]

...but every time I looked at the speedometer - I got lost!

Atomic Laser? (Physicist help pls)

[mattr]

IANAP but two of these and an entangled atomic laser = mass duplication / transportation device?

With an atomic laser it is theorized that you can create a matter hologram, whatever that is, supposedly just like the original.

Wonder if it hangs around after you turn off the reference beam? It would be a bitch if you lost the original.. poof!

Re:scanning luggage? what?

[Anonymous Coward]

Have you no sense of humor? I was kidding about the luggage scanner.

Never heard of emitting entangled beams working???

[__aahlyu4518]

"As I see it here this would require two lasers to be emitting entangled beams. I've never heard of a way this can be done."

Never seen ghostbusters ???

scan for anything

[The1Genius]

perhaps we can even get some quantum scanners to locate the Taliban cowering in caves...

Important applications in microscopy research

[luke_]

It's baffling to me that no one seems to have pointed this out, but the important applications of this technology are likely to be in light microscopy, not scanning luggage. Particularly light microscopy of biological tissues. This could be a very important advance.

wait a minute....

[yoinkslap]

according to quantum theory, the Quantum Holography hologram doesnt exist until its observed. but since its in a sealed container, it doesnt really exist at all!