3 ms·
From the publication itself: > Note that in the discussed example the reservoir acts as some quantum analogue of the classical Maxwell demon. Namely, having be
by colanderman 10y ago
From the publication itself:
> Note that in the discussed example the reservoir acts as some quantum analogue of the classical Maxwell demon. Namely, having been prepared in a special state, the reservoir is able to decrease the entropy of the system without the energy exchange with it, and can be referred to as a ‘quantum Maxwell demon’ […] In what was discussed above, an electron interaction with the quantum spin does not induce any correlations between the electron and the spin and, therefore, no classical correlations are present. Hence an important distinction between how do quantum and classical Maxwell’s demons operate.
So, it sounds like the "refrigerator-at-a-distance" (and thus energy transmission, when combined with a heat engine) actually (1) is more of a battery, and (2) doesn't interact with classical systems.
Is my reading correct?
- btilly 10y agoI don't think so. There is no energy transmission involved at all. I suspect that there is some entropy transmission, but I didn't see an analysis of that, and the amount is negligible compared to what is already in the quantum mechanical system. Of much greater surprise to me was the claim that an isolated quantum mechanical system neither gains nor loses entropy. I'm almost as astonished at this as I am at the fact that there are no chaotic quantum mechanical systems because quantum mechanical systems evolve linearly, while chaotic ones evolve exponentially. If the latter astonishes you, I recommend reading https://michaelberryphysics.files.wordpress.com/2013/07/berry337.pdf https://michaelberryphysics.files.wordpress.com/2013/07/berr....
- pdonis 10y ago> Of much greater surprise to me was the claim that an isolated quantum mechanical system neither gains nor loses entropy. Why is this surprising? It's a simple consequence of unitarity.
- btilly 10y agoIt surprises me because the universe is an isolated quantum mechanical system that certainly appears to be gaining entropy.
- pdonis 10y agoThe apparent contradiction here should not make you doubt the statement that an isolated quantum system can't gain entropy. It should make you doubt the statement that the universe, or at least the "universe" that appears to us to be gaining entropy, is an isolated quantum mechanical system. In other words, it should make you consider the possibility that we observe an apparent entropy gain because we can only observe a portion of the universe, and that portion is entangled with portions that we can't observe (and might never observe given that the expansion of the universe is accelerating). We never actually observe the pure state of the universe as a whole.