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Physicist Trying To Send a Signal Back In Time
phil reed writes "University of Washington physicist John Cramer is attempting to send a signal back through time."
From the article: "We're going to shoot an ultraviolet laser into a (special type of) crystal, and out will come two. lower-energy photons that are entangled," Cramer said.
For the first phase of the experiment, to be started early next year, they will look for evidence of signaling between the entangled photons. Finding that would, by itself, represent a stunning achievement. Ultimately, the UW scientists hope to test for retrocausality — evidence of a signal sent between photons backward in time.
The test will involve sending one of the photons down 10 miles of fiber optic cable, delaying it by 50 microseconds, then testing a quantum-mechanical aspect of the delayed photon. Due to quantum entanglement, the non-delayed photon would need to reflect the measurement made 50 microseconds later on the delayed photon. In order for this to happen, some kind of signal would need to be sent 50 microseconds back in time from the delayed photon to the non-delayed photon. (Confusing? Quantum physics is like that.)
If only it worked that way. Just because we can prove something is true in quantum physics doesn't mean it can be "upscaled" to the macro-universe. In short, even if this works it's a far cry from *you* being able to go back in time.
Formerly GNU/Anonymous Coward. This message has been determined to cause cancer in laboratory animals.
In short, even if this works it's a far cry from *you* being able to go back in time.
I'd settle for being able to send myself a short message.
LK
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Actually the experiment is designed properly. The thing is, they are already going to misinterpret the results. Quantum entaglement means that at the moment of setting wavefunction of one of the particles, the wavefunction of second particle is immediately changed to "second" possible state.
The key word here is "immediately". Special relativity redefined "the same moment" as "the same interval", i.e. line of constant t^2 - (x/c)^2 instead of plain ol' time t. Entangled states are able to react in classically understood "same moment", without regard to c and limitation of transmitting the signal at most at light speed. Which, by means of special relativity, means travelling back in time (as any transmission of signal or matter with speed greater than light).
If I did any spelling or grammar error, excuse me, I'n not a native English speaker.
There will be no signalling. What the researchers are looking for is a relation between two entangled photons, but the relation can only be found by comparing the results after.
To make a crude analogy, imagine I am sending you a bunch of random numbers, and that by altering something in my lab I can change the values of these random numbers. Then, afterwards I can tell you "look at random numbers #31,57 and 68, they form a message". The manipulation I made is instantaneous, but in order for you to get information out of it, I have to tell you where to look for via a classical communication.
This might not be very clear, maybe Wikipedia is clearer.
In short, what they are trying to do is a nice experiment, and it should work, but it does not mean you can signal backwards in time.
You can't travel back in time to GET the winning numbers for a lottery in the future. You have to SEND the winning numbers back to yourself.
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He's probably not an English speaker. Photons are spelled "foton" in plenty of countries, including Denmark, the Netherlands, southern Europe (eg. fotone in Italy), etc.
Rich.
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