Entangled Photon Production @ 1Mil/Sec (Faster-Than-Light Communication)

[On the Road]

CHAMPAIGN, Ill. — Like virtuosos tuning their violins, researchers at the University of Illinois at Urbana-Champaign have tuned their instruments and harmonized the production of entangled photons, pushing rates to more than 1 million pairs per second.

The brighter and purer entangled states could assist researchers in applications involving quantum information processing – such as quantum computation, teleportation and cryptography – and help scientists better understand the mysterious transition from quantum mechanics to classical physics.

“Entangled states are the quintessential feature of quantum mechanics,” said Paul Kwiat, a John Bardeen Professor of Electrical and Computer Engineering and Physics at Illinois. “All the manifestations of quantum mechanics in the world around us arise from the basic but bizarre coupling that exists between entangled particles.”

For example, the properties of entangled photons are inextricably linked to each other, even if the photons are located on opposite sides of the galaxy. To study this “correlation at a distance,” Kwiat and graduate students Joseph Altepeter and Evan Jeffrey produce pairs of polarization-entangled photons by passing a laser pulse through two adjacent nonlinear crystals.

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http://www.sciencedaily.com/releases/2004/07/040720085840.htm

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Who knows? Maybe some of these ideas are practical after all.

[Dudley_DUright]

1. Interesting article

However, FTL communication is not possible with entangled photons. At each place the polarization state will be random series, it is only after comparing the two lists of data (using slower than light communication) that the correlations become apparent.

[tridim]

2. So is each sample random?

Or is just the root of the data random? If so, couldn't we send a key and then the data? We could also send the data and then send a confirmation response back instantaneously on the same pair. Seems like the data could be correlated that way unless I'm missing something.

[Dudley_DUright]

3. The basic idea is that

the photon polarization is a superposition of two polarization states and when you do a measurement, one of these polarization states is realized with a certain probability (which is the key idea here). Now when you make the measurement one photon, the wavefunction collapses and you are guaranteed to get the same state from the other photon. However, since the state we measure is inherently probabilistic, we can't send information via these correlations.

[tridim]

5. Why can't we alter the polarization of the local photon

at a fixed frequency and measure the phase changes on the other end at the same frequency? It wouldn't matter if the phase is random, the zeros and ones would still be represented by the phase change at the other end at the fixed frequency.

I guess I need to do some more reading. Even if this doesn't work as a method of FTL communication, the pairs ARE communicating with each other instantaneously. Now, if we could harness the photon pair's method of communication that would be significant. I assume we don't yet understand this method?

Slightly off topic. I recently read an article that described how FTL travel could be achieved by crunching up space. It was described as reaching out to a point in space with your hand, grabbing that space and pulling it toward yourself, moving there and then letting it snap back to it's original position. Mind blowing stuff.

[Dudley_DUright]

7. Because you can't control what result you get when you make

a measurement. All QM allows us to do is to predict probabilities.

[Dudley_DUright]

4. BTW

in an example of synchronicity, I was just watching the Daily Show and the rerun of the famous turtle graphic show (as in your sig line) was just on. :-)

[JayS]

10. What about using Morse Code? n/t

n/t

[papau]

6. Why "Faster-Than-Light Communication" - why communication not

transfered.

If I understand correctly, the U of I (where some of my relatives work) has simply done some entangled photons.

Granted we can make an experiment that appears to show faster than light information transfer where we do in effect get information transfered, but it turns out the arrival of the probability field at a given point is the same but the shape of the field makes one seem to arrive before the other.

The entangled protons from Bell's 1963 work are far apart and indeed the info would travel faster than light if there was info we could extract - but there isn't. All we get is the proof of the entanglement.

What am I missing here?

[papau]

8. I should note that Bell in 63 suggested faster than light as an answer

but I thought that was put aside as no information being transfered faster than light.

Since Hawking today says that Bell's other thought about entanglement - multiple universes - are not required by black hole existence - we appear to have no other choice but to say yes - entanglement acts faster than light - but no information is moved.

But Hawking also says that the backhole releases "information" that it has taken in through a QM effect on the event horizon.

I wonder if these two concepts could be combined - if the event horizon effect concept might not also be used to prove the ability, or disprove the abilty, of the release of "information" from entanglement at faster than light speeds.

I did notice that the folks that heard Hawking this week all said they do not understand his concept of "information" and that they were waiting for the equations that would be published at the end of next month.

Something interesting to follow for the fall!

:-)

[On the Road]

9. Is It Possible to Filter the Photons for Polarization?

Even if the original stream of photons were random, a filter would ensure that only photons with a certain polarization got through. I thought that polarization was the quality of interest in the experiments.

Such filters should be available, no? Wouldn't that allow for a more coherent beam of light, allowing communication?