An 'Aspect' of Entanglement

[Graybeard]

Recently on this forum there has been some discussion on the entanglement of particles, non-locality, and causal relations. Many ideas abound about the possibilities opened up by the conclusion that our Universe is non-local. Some are good alternative theories, most are just poor interpretations of Quantum theorems ..... others are just Sci-Fi. This, of course, is my own subjective opinion.

Communication at 'faster-than-light-speed' seems to be one of the most common in the two latter categories.

This post is NOT an explanation of Entanglement, nor an explanation of EPR, nor an explanation of Bell's Theorem.

But, if you are interested in these matters, and you are new to the subject ... then this post may be a useful tool which will enable you to keep your feet on the ground while you research the bigger subject.

Of course, it may be total garbage ... depends on your view.

Many years ago, in my hometown, there were two famous racehorses. Their names were 'Fine Cotton' and 'Bold Personality'. Unfortunately, they were not famous for winning races, but they were 'entangled'.

Lets say that these two horses are entered in a race, a two horse race of ... well ... 5 klms.

Lets say that prior to the start of the race both horses had an equal chance of winning. That is: Fine cotton had a 50% chance of coming first as well as a 50% chance of coming second. Bold Personality had exactly the same.

There are many racehorses in the world, maybe millions. What separates our two horses from all the others is that they are entangled, that is, they are in the same race. No other horse is in the race, therefore other horses are not entangled with Fine Cotton and Bold Personality.

• This is easily imagined. Lets say that Sea Biscuit is racing the same day at the same time in America, his odds effect all the racehorses in the race that he is in. If his odds go up, all the other horse's odds entered in that race are effected and go down or up until the bookies, the pari-mutuel, the tote, or what ever else you call it over there, reaches a balance. Sea biscuit and the other horses in his race are 'entangled', but the change in odds for that race have no effect on our race. Our race is not entangled with theirs.

So now, both our horses are in the starting gates, their odds are 50/50 of either coming first or second. The flag drops, the gates open ... 'and theeeeeiiiir racing !'

Almost immediately, in the first few metres, and becoming more apparent with every stride, it is realised that Bold Personality is streaking away from Fine Cotton. Bold Personality is a flyer, bred from the Marmeluke sires whose only creed is 'get to the front and then stay there'. Fine Cotton is a nag and if he doesn't pick up the pace soon, is in danger of getting 'entangled' with the front runners of the next race.

By the first kilometre, Bold Personality is 500 metres ahead, by the second kilometre he is 1000 metres ahead, and by the turn to the straight he is 3 kilometres ahead.

As Bold Personality crosses the finish line first, Fine Cotton, rolling in his gait, and covered in a lather of sweat, is 3.5 kilometres behind and 50% of the punters are looking very sick, jangling the coins in their pockets to reassure themselves they have a bus fare home.

Now it takes 'light' some measurable time to travel 3.5 kilometres, so there is no way to pass information instantly to Fine Cotton that Bold Personality has come first and that he, Fine Cotton, is going to come second .

But what 'seemingly amazing' thing has happened here ?

At the instant, the very instant, that Bold Personality crossed the finish line, his probability of coming second fell to zero, his probability of coming first climbed to 100%. Simultaneously, at that exact same instant, Fine Cotton's probability of coming first dropped to zero, and his probability of coming second rose to 100%.

Both of these things happened at 'Faster Than Light Speed'. But nothing passed between the two horses, no information, no message, no communication, no magic ray, no Star Trek beam.

So it is with entangled particles. We do not know, because of uncertainty, if either particle will be found with spin-up or spin-down. But we do know that if one is found with spin-up then the other will be found with spin-down, provided that we detect them from the same plane.

The only information that we become privy to, is that when we observe one of the entangled singlet particles as having spin-up, we cause its probability to be in the spin-down state to drop to zero. We collapse its probability wave to a certainty. When its probability wave collapses, because it is entangled with other particles (they are in the same race), their probability waves also collapse to zero (they have no chance of winning the race). This happens instantly, and yet it is no affront to our common sense.

Probability waves do not have mass. Their collapse, or spike, cannot be said to break the speed of light. Special Relativity is not effected or broken.

If you don't find this convincing and you still have a fondness for the idea that something passed between them, then, in order to compare the results, communications between the detector operators via phone call or email still has to be conducted and this happens at slower than light speed. In other words the jockey on Fine Cotton still has 3.5 kilometres to thrash his nag homewards before the probability waves of the two horses can be compared, and in Fine Cottons case, as in every case, this is going to take time. Therefore, it seems apparent to me, that instantaneous communication is still just as impossible as it always was prior to our discovery of entanglement

How did I do with this explanation ? It is not meant to be comprehensive, just an analogy. Your ideas would be appreciated.

cool bananas ... greg

[Profpat]

It's a logical argument Greg, however, when it comes to quantum mechanics some things are counter-intuitive.

There are more things in heaven and earth, Horatio,
Than are dreamt of in your philosophy.
Hamlet Act 1, scene 5, 159–167

To be continued... for now the best evidence supports Bell's Theorem.

Best,

Pat

[Graybeard]

Thanks Pat, but I did not mean to imply that I am against Bell's Theorem, just the reverse.

Rather, that many inferences drawn from Bell's theorem are not thought thru carefully enough before reaching unrealistic conclusions

There are more things in heaven and earth, Horatio, Than are dreamt of in your philosophy.

Maybe so, maybe no, but Bell's Theorem is not a portal to them, nor is it a philosophy

cool bananas ... greg

[austintorn@aol.com]

They (the physicists) have always noted that no information can be passed by these spin polarity correlation happenings…

[ggullet]

with us or agin us

[Graybeard]

with us or agin us

What side is us ??

greg

[Profpat]

They (the physicists) have always noted that no information can be passed by these spin polarity correlation happenings…

Why not, if you can observer it?

1. Introduction
It has long been wondered if faster than light communication might be possible [1] and the
collapse of the quantum wave-function, upon measurement, might be utilized to achieve
this, with due concern for any paradoxes that might result.
Firstly, there is no direct violation of special relativity since it is the quantum wavefunction

that collapses and no energy or matter travels at faster than light speed.(From the ELECTRONIC JOURNAL OF THEORITICAL PHYSICS June 2008 )

AND

Is faster-than-light communication possible using entangled photons
and a double slit?

© 2006 Raymond Jensen

rjensen2@nd.edu

Abstract
A recent experiment by Dopfer was done using entangled photons in which one of
each pair of photons was allowed to pass through a double slit prior to detection.
Depending on how the photon’s doubles were measured on the opposite end, the
photons passing through the double slit either produced an interference pattern or
they produced no interference pattern. The measurements were done with the aid
of a coincidence circuit. It is argued here without any new theory that there is the
possibility that Dopfer’s experiment, after modification by among other things,
removing the coincidence circuit, allows the ability to transmit signals faster than

the speed of light.

I guess all physicists don't agree. Just most.

[Graybeard]

Hi peoples .... some members have PM'd that I have not made my post (thread opener) sufficiently clear.

When I said that a probability wave collapses faster than light, this was tongue in cheek ... this was not meant to imply that they 'travel' faster than light speed .... as probability waves are not the same as water waves, or any other kind of wave ... they are just calculations.

Sorry for the confusion.

cool bananas ... greg

[austintorn@aol.com]

Prof,

If I traveled faster than light, then it would be dark there, unless I brought a flashlight, but that would probably look dark to me, too. So, how about if I just be lazy and sit around on the sofa? This hectic world really has to slow down.

[Steven A Colyer]

They (the physicists) have always noted that no information can be passed by these spin polarity correlation happenings…

Yes, and thanks to Profpat his post as well.

You can RECIEVE information at faster than light speed. What you can't do is SEND information at FTL. That means Orson Scott Card's "ansible" that transmits voice and data simultaneously everywhere in his Ender-verse is impossible, given our early-21st Century knowledge of Physics. Makes for great fiction though.