Tuesday, May 05, 2009

Science, Spirituality, and Some Mismatched Socks

This actually is a surprisingly good layman's review of the current state-of-the-art knowledge on quantum entanglement, all coming from, of all places, the Wall Street Journal! It also had a rather amusing anecdote coming from John Bell.

In a 1981 paper, Mr. Bell took a swing at Einstein's notion of "hidden variables" by relating the sock-wearing patterns of his physicist colleague Reinhold Bertlmann. Mr. Bell noted that if he saw one of Mr. Bertlmann's feet coming around the corner and it had a pink sock, he would instantly know, without seeing the other foot, that the second sock wouldn't be pink. To the casual observer that may seem magical, or controlled by "hidden variables," but it was no mystery to Mr. Bell because he knew that Mr. Bertlmann liked to wear mismatched socks.

Not sure if this is true, but it certainly is funny.

There are a couple of very recent development in this area of study that was mentioned in this article. The first is apparent violation of the "speed" of entanglement that was measured by Gisin's group.

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."

I reported this earlier here with the exact citation.

The second was the direct observation of the Hardy's paradox.

In 1990, the English physicist Lucien Hardy devised a thought experiment. The common view was that when a particle met its antiparticle, the pair destroyed each other in an explosion. But Mr. Hardy noted that in some cases when the particles' interaction wasn't observed, they wouldn't annihilate each other. The paradox: Because the interaction had to remain unseen, it couldn't be confirmed.

In a striking achievement, scientists from Osaka University have resolved the paradox. They used extremely weak measurements -- the equivalent of a sidelong glance, as it were -- that didn't disturb the photons' state. By doing the experiment multiple times and pooling those weak measurements, they got enough good data to show that the particles didn't annihilate. The conclusion: When the particles weren't observed, they behaved differently.

In a paper published in the New Journal of Physics in March, the Japanese team acknowledged that their result was "preposterous." Yet, they noted, it "gives us new insights into the spooky nature of quantum mechanics." A team from the University of Toronto published similar results in January.

Again, I've mentioned this in another entry, with not only the exact citation, but also a link to the paper which can be accessed for free.

The issue of "spirituality" as mentioned in the article related to Bernard d'Espagnat and his Templeton prize has already been tackled here. He certainly is a master at having his "wiggle room" in this article. All I can say is that if you make your idea vague enough, you can claim validity with almost anything.



Tom said...

AFAIK "Even when they're miles apart, if the spin of one particle is changed, the spin of the other instantly changes, too."

is wrong, and one of the common misconceptions about entanglement. You can measure the spin and know the partner's spin immediately, but you can't change the spin and have the partner respond instantly — that implies you knew the spin already. Entanglement implies the spin state is unknown until measured, rather than having the spin be a hidden variable. Once you measure it, the entanglement is broken.

ZapperZ said...


Next time I'm being accused of being rather "picky" over some of these news reports, I'll point to this one where I actually let something like this slide! :)