Coffee!!: You're lucky enough if you even find the other sock anyway ....

In "Is quantum theory weird enough for the real world?", Richard Webb explains why we might need a new theory of quantum mechanics:

In our day-to-day world, we are accustomed to the idea that two events are unlikely to be correlated unless there is a clear connection of cause and effect. Pulling a red sock onto my right foot in no way ensures that my left foot will also be clad in red - unless I purposely reach into the drawer for another red sock. In 1964, John Bell of the CERN particle physics laboratory near Geneva, Switzerland, described the degree of correlation that classical theories allow. Bell's result relied on two concepts: realism and locality.

Realism amounts to saying that the properties of an object exist prior to, and independent of, measurement. In the classical world, that second sock in my drawer is red regardless of whether or not I "measure" its state by looking at it. Locality is the assumption that these properties are independent of any remote influence.

In the quantum world, these are dangerous assumptions. "It turns out that either one or both of Bell's principles must be wrong," says Brukner. If quantum effects were visible in our everyday world, I might well find that my pulling on a red sock leads to the colour of the sock left in my drawer automatically changing to red.

[ ... ]

A world with this degree of interconnection would be weird indeed. I might find that by selecting a red sock from my drawer in the morning, I had predetermined the colour not just of my other sock, but that of my shirt, underpants and of the bus I ride to work.

( - New Scientist 23 August 2010)

The only time this ever happens in the macro world, in my own life experience, is if someone is fool enough to put dyed clothes in the javel water bleach wash. If you like white, buy it off the rack.

More quantum stories here.

You never know what'll turn up useful ...

In "Science, Spirituality, and Some Mismatched Socks" (Wall Street Journal, May 5, 2009)", Gautam Naik explains how "researchers turn up evidence of 'spooky' quantum behavior and put it to work in encryption and philosophy.":

Last year, Dr. Gisin and colleagues at Geneva University described how they had entangled a pair of photons in their lab. They then fired them, along fiber-optic cables of exactly equal length, to two Swiss villages some 11 miles apart. During the journey, when one photon switched to a slightly higher energy level, its twin instantly switched to a slightly lower one. But the sum of the energies stayed constant, proving that the photons remained entangled. More important, the team couldn't detect any time difference in the changes. "If there was any communication, it would have to have been at least 10,000 times the speed of light," says Dr. Gisin. "Because this is such an unlikely speed, the conclusion is there couldn't have been communication and so there is non-locality."

Right, so there is no common-sense explanation of quantum mechanics. About the encryption?

Some researchers are using the uncertain state of photons to solve real-world problems. When encrypting sensitive data such as a bank transfer, both the sending party and the receiving party must have the same key. The sender needs the key to hide the message and the receiver to reveal it. Since it isn't always practical to exchange keys in person, the key must be sent electronically, too. This means the key (and the messages) may be intercepted and read by an eavesdropper. An electronic key is usually written in the computer binary code of "ones" and "zeros." Quantum physics permits a more sophisticated approach. The same "ones" and "zeros" can now be encoded by using the properties of photons, like spin. If someone intercepts a photon-based message, the spins change. The receiver then knows the key has been compromised. MagiQ Technologies Inc. of Cambridge, Mass., refreshes its quantum keys as often as 100 times a second during a transmission, making it extremely hard to break. It sells its technology to banks and companies. Dr. Gisin is a founder of ID Quantique SA in Switzerland. The company's similar encryption tool is used by online lottery and poker firms to safely communicate winning numbers and winning hands. Votes cast in a recent Swiss federal election were sent in a similar way.

We live in a mysterious world, where uncertainty is better for security than certainty - but at the quantum level only. The person who left his keys stuck in the front door all night is one dumb bunny and can be grateful that most thieves wouldn't expect to get so lucky, which is why he was the first person to discover the problem in the morning.

Time: Can time flow backwards in quantum physics?

In a Viewpoint article, "Weak measurements just got stronger", for This Week in Physics ( April 27, 2009) Sandu Popescu, Physics 2, 32 (2009) In the weird world of quantum mechanics, looking at time flowing backwards allows us to look forward to precision measurements:

In 1964 when Yakir Aharonov, Peter Bergman, and Joel Lebowitz started to think seriously about the issue of the arrow of time in quantum mechanics [1]—whether time only flows from the past to the future or also from the future to the past—none of them could have possibly imagined that their esoteric quest would one day lead to one of the most powerful amplification methods in physics. But in the weird, unpredictable, yet wonderful way in which physics works, one is a direct, logical, consequence of the other. As reported in Physical Review Letters by P. Ben Dixon, David J. Starling, Andrew N. Jordan, and John C. Howell at the University of Rochester this amplification method makes it possible to measure angles of a few hundred femtoradians and displacements of 20 femtometers, about the size of an atomic nucleus [2].

[ ... ]

Viewed from one angle, this story is all about fundamental philosophical ideas. Does the spin indeed have a value larger than 1/2 or is the result simply an error in the imprecise measuring device used? Does the spin indeed have both the x spin component and the z one well defined? And, above all, does time indeed flow in two directions in quantum mechanics? To be sure, the strange outcome of the measurement of Sπ/4 in this pre- and post-selected ensemble could indeed be obtained as an error in the measurement, an error in which the pointer of the measuring apparatus moved more than it should have. The explanation can be fully given by standard quantum mechanics, involving regular past-to-future-only flow of time. But the explanation is cumbersome and involves very intricate interference effects in the measuring device. Assuming that time flows in two directions tremendously simplifies the problem. As far as I can tell, Aharonov, Albert, and Vaidman hold the view that one should indeed accept this strange flow of time. I fully agree. Not everybody agrees though, and this is one of the most profound controversies in quantum mechanics.Viewed from one angle, this story is all about fundamental philosophical ideas. Does the spin indeed have a value larger than 1/2 or is the result simply an error in the imprecise measuring device used? Does the spin indeed have both the x spin component and the z one well defined? And, above all, does time indeed flow in two directions in quantum mechanics? To be sure, the strange outcome of the measurement of Sπ/4 in this pre- and post-selected ensemble could indeed be obtained as an error in the measurement, an error in which the pointer of the measuring apparatus moved more than it should have. The explanation can be fully given by standard quantum mechanics, involving regular past-to-future-only flow of time. But the explanation is cumbersome and involves very intricate interference effects in the measuring device. Assuming that time flows in two directions tremendously simplifies the problem. As far as I can tell, Aharonov, Albert, and Vaidman hold the view that one should indeed accept this strange flow of time. I fully agree. Not everybody agrees though, and this is one of the most profound controversies in quantum mechanics.

Science: Bell's inequality the most profound fact ever discovered?

In response to this post ("Quantum theory: Finally facing up to its threat to special relativity"), friend Malcolm Chisholm writes to say:

I have been wondering when you would blog about Bell's inequality.

Bell's Inequality has its foundation in traditional logic (stuff developed by the scholastic guys of the Middle Ages). It states the following

The number of objects which have parameter A but not parameter B plus the number of objects which have parameter B but not parameter C is greater than or equal to the number of objects which have parameter A but not parameter C.

So for instance, if you have a class of students, then

The number of girls who are not blond plus the number of blond students who are under six feet tall must be greater or equal to the number of girls who are under six feet tall.

This will always be true. It is amazing. You can do it for all kind of populations that possess 3 attributes in the macroscopic world that we inhabit. And yet it can be applied to the domain of quantum entanglement to prove that everything in the universe is utterly connected at a very fundamental level. It really is the most profound fact ever discovered in science

Here is a link for more (and it's Canadian!).

Well, he knows how I will love that!

If Bell's inequality is indeed the most profound fact ever discovered in science, it is interesting (at least to me), that Bell started out wanting to disprove it. He was a follower of Einstein and shared the Einsteinian suspicion of quantum physics.

I read his book and toward the end he finally concedes defeat, in the nicest possible way. I recall it as somewhat touching.

Here's more about Irish physicist John Bell, pictured above. Here are his collected works, Foundations of Quantum Mechanics.

Quantum theory: Finally facing up to its threat to special relativity?

In "Was Einstein Wrong?: A Quantum Threat to Special Relativity" (Scientific American, February 18, 2009), David Z Albert and Rivka Galchen discuss, with commendable frankness, the implications of the fact that the universe is non-local. You are there and I am here, and that's all there is to it, right? Well, not among elementary particles:

... according to quantum mechanics one can arrange a pair of particles so that they are precisely two feet apart and yet neither particle on its own has a definite position.
Furthermore, the standard approach to understanding quantum physics, the so-called Copenhagen interpretation - proclaimed by the great Danish physicist Niels Bohr early last century and handed down from professor to student for generations - insists that it is not that we do not know the facts about the individual particles' exact locations; it is that there simply aren't any such facts. To ask after the position of a single particle would be as meaningless as, say, asking after the marital status of the number five. The problem is not epistemological (about what we know) but ontological (about what is).

[ ... ]

But entanglement also appears to entail the deeply spooky and radically counterintuitive phenomenon called nonlocality - the possibility of physically affecting something without touching it or touching any series of entities reaching from here to there. Nonlocality implies that a fist in Des Moines can break a nose in Dallas without affecting any other physical thing (not a molecule of air, not an electron in a wire, not a twinkle of light) anywhere in the heartland.

Albert and Galchen focus on the problem quantum theory poses for special relativity, pointing out that the problem has long been evaded.

But it strikes me that quantum theory poses other problems as well.

One frequently encounters claims that action at a distance cannot happen when it might be more wisely described as statistically improbable (if you are somewhat largerthan an elementary particle). Statistical improbability is the basis on which lottery fraud is detected, for example. Few will believe that the lucky rabbit's foot did it.

The authors discuss the work of Irish physicist John Bell, who wanted to know whether non-local behaviour was real or only apparent. (One way of dealing with the conflict between special relativity and quantum theory has been to say, with Einstein, that quantum theory is incomplete.) However,

Bell seems to have been the first person to ask himself precisely what that question means. What could make genuine physical nonlocalities distinct from merely apparent ones? He reasoned that if any manifestly and completely local algorithm existed that made the same predictions for the outcomes of experiments as the quantum-mechanical algorithm does, then Einstein and Bohr would have been right to dismiss the nonlocalities in quantum mechanics as merely an artifact of that particular formalism. Conversely, if no algorithm could avoid nonlocalities, then they must be genuine physical phenomena. Bell then analyzed a specific entanglement scenario and concluded that no such local algorithm was mathematically possible.

And so the actual physical world is nonlocal. Period.

For the most part, work that demonstrated that fact was ignored, but Albert and Galchen argue that that is changing:

It took yet another 30 years after the publication of Bell's paper for physicists to finally look these issues squarely in the face. The first clear, sustained, logically flawless and uncompromisingly frank discussion of quantum nonlocality and relativity appeared in 1994, in a book with precisely that title by Tim Maudlin of Rutgers University. His work highlighted how the compatibility of nonlocality and special relativity was a much more subtle question than the traditional platitudes based on instantaneous messages would have us believe. Maudlin's work occurred against the backdrop of a new and profound shift in the intellectual environment.

One hopes that this shift will lead to open-minded examination instead of reassertions of truisms.

See also: Physics: A peek behind the veil of reality earns physicist Templeton Prize