Quantum Randomness Explained: A Beginner's Guide

[avaxtasafi]

I came across the term 'Quantum Randomness' in another online discussion and was wondering what it actually was? Could anyone explain it to someone with a very sketchy knowledge of physics, if at all possible? Thanks!

 

[caribou]

Quantum randomness is that we can tell what the possibilities are for something to happen, but not which possibility will happen. It seems to be random.

If a particle can freely pick something like, for example, a direction to travel from possibilities like north, east, south, west, up or down, there's no way to tell which direction it would pick or why.

It seems to just randomly choose a direction and off it goes.

 

[dextercioby]

I couldn't explain you in simple,easily comprehendable terms.As a definition,my inner structure could not come up with simple explanations.Though i admit,when in high-school,when the teacher asked to solve some problem as a 12-year old would ,i usually came first...But,in between,i've gotten into really complicated physics of which,apparently,i can get out,or wouldn't get out.
On the other hand,in quantum world,nothing is random.That's because,as a science,its axiomatical structure is built as to be complete and closed wrt to itself.

 

[avaxtasafi]

Thanks for that guys... but is it possible that we just haven't discovered what causes the particle to move north/south/etc.? Could there really be a cause behind this 'randomness' that we're not yet aware of? Or am I simplifying things?

 

[motai]

Thanks for that guys... but is it possible that we just haven't discovered what causes the particle to move north/south/etc.? Could there really be a cause behind this 'randomness' that we're not yet aware of? Or am I simplifying things?

There have been random stabs at this question. The physicist David Bohm suggested an "implicit order" but his theories sway a little from the Copenhagen interpretation and concepts like pilot waves, from what I know so far, are difficult to test experimentally because of the number of hidden variables.

http://en.wikipedia.org/wiki/Bohm_interpretation

 

[caribou]

Thanks for that guys... but is it possible that we just haven't discovered what causes the particle to move north/south/etc.? Could there really be a cause behind this 'randomness' that we're not yet aware of? Or am I simplifying things?

No, you're right. It is possible that what we think is random isn't actually random. Someone could come up with a theory behind the apparent randomness but it's just a lot simpler to just assume that it really is random.

 

[selfAdjoint]

No, you're right. It is possible that what we think is random isn't actually random. Someone could come up with a theory behind the apparent randomness but it's just a lot simpler to just assume that it really is random.

This is just exactly the point of the "hidden variables" theories. The opinion of most quantum physicists is that the Aspect and other experiments testing the Bell inequalities have definitesly killed off the LOCAL hidden variables theories, that is, the ones that obey relativity. This leaves non-local hidden variables theories, of which the most famous is Bohm's theory.

 

[Rhizomorph]

Has anyone read C. S. Unnikrishnan's explanation for quantum correlations (http://arxiv.org/PS_cache/quant-ph/pdf/0001/0001112.pdf )? He's written a few papers on the matter and seems to have developed a convincing proof that such correlations can still be achieved with a local/hidden variables theory. But I've seen no recognition of his findings by anyone else.

 

[NeutronStar]

Has anyone read C. S. Unnikrishnan's explanation for quantum correlations (http://arxiv.org/PS_cache/quant-ph/pdf/0001/0001112.pdf )? He's written a few papers on the matter and seems to have developed a convincing proof that such correlations can still be achieved with a local/hidden variables theory. But I've seen no recognition of his findings by anyone else.

Thanks for pointing the way to that paper! That was great!

 

[ZapperZ]

Has anyone read C. S. Unnikrishnan's explanation for quantum correlations (http://arxiv.org/PS_cache/quant-ph/pdf/0001/0001112.pdf )? He's written a few papers on the matter and seems to have developed a convincing proof that such correlations can still be achieved with a local/hidden variables theory. But I've seen no recognition of his findings by anyone else.

So how many other papers has he "written"? I didn't find anything by him on this in PRL. I'm hoping what you mean by "written" is not just what has appeared in e-print ArXiv. Furthermore, it isn't "convincing" if the experts in the field aren't paying attention to it. People thought the "time-loophole" argument was "convincing", but after people finally got through with it, it isn't anymore.

Zz.

 

[Rhizomorph]

Wow, what sarcasm...

First of all, did you even read it? Second of all, saying something isn't convincing because the "experts" aren't paying attention to it is just, well, ignorant. He makes minimal assumptions (less than Bell, in fact) and his math is sound. So if you want to refute it, go for it (in fact, I'm looking for a refutation of it, that's why I asked about it) - but do so scientifically. Don't just say "oh well must be wrong because no one else talks about it." As for other papers he may or may not have "written" (as you insist on quoting), here are some in journals...

1. Limit on the strength of Intermediate Range forces coupling to isospin, R. Cowsik, N.Krishnan, S. N. Tandon and C. S. Unnikrishnan, Phys. Rev. Lett. 61, 2179, (1988).

2. A satellite-Borne experiment to study the fifth force, R. Cowsik, N.Krishnan, S. N. Tandon C. S. Unnikrishnan and P. Sarawat, Pramana- J. Phys. 32, L303, (1989).

3. Torsion balance experiments for measurement of weak forces in nature, R. Cowsik, N.Krishnan, P. Saraswat, S. N. Tandon, C. S. Unnikrishnan, U. D. Vaishnav. C. Viswanadham and G. P. Puthran, Ind. J. Pure and Appl. Phys. 27, 691, (1989).

4. Strength of Intemediate range forces coupling to isospin, R. Cowsik, N.Krishnan, S. N. Tandon and C. S. Unnikrishnan, Phys. Rev. Lett. 64, 336, (1990).

5. On the anomalous weight reduction in rotating gyroscopes, C. S. Unnikrishnan, Current Science 59, 600, (1990).

6. Search for a fifth force, C. S. Unnikrishnan, Pramana - J. Phys. 41 (supplement), 395, (1993).

7. On naked singularities in spherically symmetric gravitational collapse, C. S. Unnikrishnan, Bull. Astr. Soc. India 21, 413, (1993).

8. Gravitational collapse of inhomogeneous dust: naked singularities, black hole formation and Hawking evaporation, C. S. Unnikrishnan, Bull. Astr. Soc. India 21, 417, (1993).

9. Experimental gravitation in India - progress and challenges, C. S. Unnikrishnan, Classical and Quantum Gravity 11, A195, (1994).

10. Naked singularities in spherically symmetric gravitational collapse - A critique, C. S. Unnikrishnan, General Relativity and Gravitation 26, 665, (1994).

11. Physically motivated proof of the cosmic censorship conjecture, C. S. Unnikrishnan, Phys. Rev. D15, 53, Rapid Comm. R580, (1996).

12. Does a superconductor shield gravity?, C. S. Unnikrishnan, Physica C 266, 133, (1996).

13. Some comments on the two prism tunneling experiment, C. S. Unnikrishnan and Sudha A. Murthy, Phys. Lett. A 221, 1, (1996).

14. Persistent currents and role of whispering gallery modes, C. S. Unnikrishnan, Physica B 223&224, 634, (1996).

15. Comment on ‘Sonoluminescence as quantum vacuum radiation’, C. S. Unnikrishnan and S. Mukhopadhyaya, Phys. Rev. Lett. 77, 4690, (1996).

16. Nuclear Spin dependent parity non-conserving transitions in Ba+ and Ra+, K. P. Geetha, Dilip A. Singh, B. P. Das and C. S. Unnikrishnan, Phys. Rev. A58, Rapid Communications. R16-18, (1998).

17. Do quantum like theories imply observable quantum like effects?, C. S. Unnikrishnan, Current Science 76, 413, (1999).

18. Experimental test of a quantum like theory: Motion of electrons in a uniform magnetic field, in a variable potential well, C. S. Unnikrishnan and C. P. Safvan, Modern Phys. Lett. 14, 479-490, (1999).

19. White light cooling of a He metastable beam, E. Rasel, F. Periera, F. Pavone, F. Perales, C. S. Unnikrishnan, and Michèle Leduc, European Physical Journal D 7, 311, 1999.

20. New limits on the Majorana gravitational shielding from the Zurich G experiment, C. S. Unnikrishnan and G. T. Gillies, Phys. Rev. D 58, Rapid Comm., R16-18, (2000).

21. Popper’s experiment, Signal locality, uncertainty principle and momentum conservation, C. S. Unnikrishnan, Found. Phys. Letters 13, 197, (2000).

22. Origin of complementarity without momentum back-action in atom interferometry experiments, C. S. Unnikrishnan, Phys. Rev. A 62, 015601, (2000).

23. Resolution of nonlocality puzzle in EPR paradox, C. S. Unnikrishnan, Current Science 79, 195, (2000).

24. Quantum correlations from wave-particle unity and locality: Resolution of EPR puzzle, C. S. Unnikrishnan, Annales de la Fondation L. de Broglie (Paris) 25, 363 (2000).

25. Anomalous gravity data during 1997 total solar eclipse do not support hypothesis of gravitational shielding, C. S. Unnikrishnan, A. K. Mohapatra, and G. T. Gillies, Phys. Rev. D 63, 062002, (2001).

26. A unified view of Aharonov-Bohm like phases and some applications, C. S. Unnikrishnan, Pramana 56, 321, (2001).

27. The accelero-magnetic field, Thomas precession and an equivalence principle for the spin, C. S. Unnikrishnan, Mod. Phys. Lett. A 16, 429, (2001).

28. Effcient magneto-optical trapping of a metastable Helium gas, F. Pereira Dos Santos, F. Perales, J. Léonard, A. Sinatra, Junmin Wang, F. Saverio Pavone, E. Rasel, C. S. Unnikrishnan, and Michèle Leduc, Eur. Phys. J. AP 14, 69 (2001).

29. Penning collisions of laser-cooled metastable Helium atoms, F. Pereira Dos Santos, F. Perales, J. Léonard, A. Sinatra, Junmin Wang, F. Saverio Pavone, E. Rasel, C. S. Unnikrishnan, and Michèle Leduc, Eur. Phys. J. D 14, 15 (2001).

30. Bose-Einstein condensation of metastable Helium, F. Pereira Dos Santos, J. Léonard, Junmin Wang, C. J. Barrelet, F. Perales, E. Rasel, C. S. Unnikrishnan, Michèle Leduc, and C. Cohen-Tannoudji, Phys. Rev. Lett. 86, 3459 (2001).

31. Do leptons generate gravity? C. S. Unnikrishnan and G. T. Gillies, Gravitation and Cosmology 7, 251, (2001).

32. Do leptons generate gravity? First constraints from laboratory experiments, C. S. Unnikrishnan and G. T. Gillies, Phys. Lett. A. 288, 161, (2001).

33. Quantum correlations from local amplitudes and the resolution of the EPR nonlocality puzzle, C. S. Unnikrishnan, Optics and Spectroscopy 91, 358, (2001).

34. Interaction free measurements of the second kind, C. S.Unnikrishnan, Optics and Spectroscopy 91, 393, (2001).

35. Is the quantum mechanical description of physical reality complete ? Resolution of the EPR puzzle, C. S. Unnikrishnan, Found. Phys. Lett. 15, 1-25 (2002).

36. Equivalence Principle and quantum mechanics : a theme in harmony, C. S. Unnikrishnan, Mod. Phys. Lett. A17, 1081 (2002).

37. Nano-constraints on the spatial anisotropy of the gravitational constant, C. S. Unnikrishnan and G. T. Gillies, Physics Letters A 305, 26 (2002).

38. Production of Bose-Einstein condensate of metastable helium atoms, F. Pereira Dos Santos, J. Leonard, J. Wang, C. J. Barrelet, F. Perales, E. Rasel, C. S. Unnikrishnan, M. Leduc and C. Cohen-Tannoudji, European Physical Jl. D 19, 103 (2002).

39. Proof of absence of spooky action at a distance in quantum correlations, C. S. Unnikrishnan, (Proc. Winter Institute in Foundations of Quantum Mechanics and Quantum Optics) Pramana 59, 295 (2002).

40. Evidence for the quantum birth of our Universe, C. S. Unnikrishnan, G. T. Gillies and R. C. Ritter, (Proc. Winter Institute in Foundations of Quantum Mechanics and Quantum Optics), Pramana 59, 369 (2002).

41. Comment on "Observation of matter wave beat phenomena in the macrodomain” C. S. Unnikrishnan, to appear in Phys. Rev. E (2004)

He's contributed to some books as well if you'd like me to list them.

 

[ZapperZ]

Wow, what sarcasm...

First of all, did you even read it? Second of all, saying something isn't convincing because the "experts" aren't paying attention to it is just, well, ignorant. He makes minimal assumptions (less than Bell, in fact) and his math is sound. So if you want to refute it, go for it (in fact, I'm looking for a refutation of it, that's why I asked about it) - but do so scientifically. Don't just say "oh well must be wrong because no one else talks about it." As for other papers he may or may not have "written" (as you insist on quoting), here are some in journals...

First of all, if you can get by beyond your chip-on-shoulder part, you would have noticed that I SPECIFICALLY SAID:

I didn't find anything by him on THIS in PRL

"On this" I meant I made a quick look for this author on THIS related topic. I see you didn't find anything by him "on this" either in PRL from the list you gave. So what are you so pissed at? BTW, I wouldn't advertise too much on getting published in "Foundation of Physics Lett." journal. I personally know of someone who is clueless in physics and got published in there on some "theory" that she essentially made up.

Secondly, YOU were the one who claimed that this person has made "convincing" argument for local hidden variables. I simply pointed out that for anything in physics to be "convincing", it must have the consensus of experts in that particular field. This isn't my personal preference, it is what it is. Maybe it is convincing to you. Unfortunately (or fortunately), one person does not qualify for something to be designated as convincing in physics. I find that the existence of spin-charge separation in 2D conductors as "convincing", but I certainly would NOT announce it to everyone that this is so since the consensus isn't there yet! Doing such a thing before it is widely accepted is irresponsible.

Zz.

 

[blip]

If no one recommends an article that they´ve found "convincing" because the rest of the scientific community hasn't approved it as "convincing" then how does an article circulate to being with?

 

[ZapperZ]

If no one recommends an article that they´ve found "convincing" because the rest of the scientific community hasn't approved it as "convincing" then how does an article circulate to being with?

The article needs to be published in a respected peer-reviewed journal. That is one of the surest way to get the attention of as many physicists as possible. That is why most physicists would want to have a paper appearing in Science, Nature, and Physical Review Letters. These are the three most prestigous journals for physics articles. But also because of that, these three have the toughest criteria of any journals for publications, and your manuscript can be reviewed by between 3 to up to 5 referees.

Zz.

 

[Rhizomorph]

Zz, does the lack of "expert" recognition of his paper mean you are unwilling to comment on it? Does anyone have any opinions?

 

[DrChinese]

Zz, does the lack of "expert" recognition of his paper mean you are unwilling to comment on it? Does anyone have any opinions?

Sure, I read it and it is long on semantics and short on substance. There are still no classical local hidden variables so I am not really sure what the point is.

You may recall that Bell's Theorem assumes that any probability must be in the range of 0% to 100%. This is essentially the "classical" portion that most people are concerned with. Once you leave the classical world, all kinds of things are possible anyway. Many worlds, Copenhagen, etc.

This paper does not negate Bell in any way.