Thursday, July 3, 2008

Can reincarnation save Schrodinger's cat?

Reincarnation can indeed save Schrödinger's cat, reports Zeeya Merali in Nature News (July 2, 2008).

The "cat" is a 1935 thought experiment intended to illustrate the superposition of two states in quantum theory - that is, both states exist until a measurement is attempted, which forces one or other to prevail (live cat or dead cat).

According to WhatIs,

We place a living cat into a steel chamber, along with a device containing a vial of hydrocyanic acid. There is, in the chamber, a very small amount of a radioactive substance. If even a single atom of the substance decays during the test period, a relay mechanism will trip a hammer, which will, in turn, break the vial and kill the cat. The observer cannot know whether or not an atom of the substance has decayed, and consequently, cannot know whether the vial has been broken, the hydrocyanic acid released, and the cat killed. Since we cannot know, the cat is both dead and alive according to quantum law, in a superposition of states. It is only when we break open the box and learn the condition of the cat that the superposition is lost, and the cat becomes one or the other (dead or alive). This situation is sometimes called quantum indeterminacy or the observer's paradox : the observation or measurement itself affects an outcome, so that the outcome as such does not exist unless the measurement is made. (That is, there is no single outcome unless it is observed.)


Now, Nadav Katz at the University of California, Santa Barbara, and his colleagues have performed an experiment in which they pull a quantum state back from the brink of collapse, 'uncollapsing' it and returning it to its unobserved state. Effectively, they have peeked at Schrodinger's cat in its box, but saved it from near-certain death (N. Katz et al.

To physicists raised on the textbook Copenhagen interpretation, any notion of uncollapsing a quantum state seems “astonishing”, says Markus Büttiker, a quantum physicist at the University of Geneva in Switzerland. “On opening the box, Schrödinger's cat is either dead or alive — there is no in between.”

However, a more recent interpretation of quantum mechanics, 'decoherence theory', suggests that collapse does not occur instantaneously. Instead it plays out gradually as the quantum system slowly interacts with its environment (see Nature 453, 22–25; 2008). In 2006, Alexander Korotkov of the University of California, Riverside, and Andrew Jordan, of the University of Rochester in New York, proposed that this may leave open a time period in which experimenters could intervene to halt the collapse (A. N. Korotkov & A. N. Jordan Phys. Rev. Lett. 97, 166805; 2006). They provided blueprints for an experiment to test the idea, which Katz, Korotkov and their colleagues have now done.
Well, if quantum collapse does not occur instantaneously, maybe events are not as certain as many have thought.

Indeed, I wonder if quantum physicists will end up proving CS Lewis's concept in The Great Divorce, where
[B]oth good and evil, when they are full grown, become retrospective. Not only this valley but all their earthly past will have been Heaven to those who are saved. Not only the twilight in the town, but all their life on Earth too, will then be seen by the damned to have been Hell. That is what mortals misunderstand. They say of some temporal suffering, ‘No future bliss can make up for it’, not knowing that Heaven, once attained, will work backwards and turn even that agony into a glory. And of some sinful pleasure they say ‘Let me have but this and I’ll take the consequences”: little dreaming how damnation will spread back and back into their past and contaminate the pleasure of the sin. Both processes begin even before death. The good man’s past begins to change so that his forgiven sins and remembered sorrows take on the quality of Heaven: the bad man’s past already conforms to his badness and is filled only with dreariness. And that is why, at the end of all things, when the sun rises here and the twilight turns to blackness down there, the Blessed will say ‘We have never lived anywhere except in Heaven’, and the Lost, ‘We were always in Hell’. And both will speak truly.” (The Great Divorce, pg. 69)
Actually, I think that the process begins in this life, once you have a few decades under your belt. So even if you don't believe in eternal life, you can still cash in some of those coupons right now.

Save the cat, but get her spayed. And do read The Great Divorce.

(Note: The image of Schrodinger's cat is from SDLY in China.)