ParticleGrl said:
I once read that the quantum-zeno effect was a killer for ensemble interpretations,
It's not (at least as of 1991)...
but I've never looked at the arguments around this.
Here are 3 relevant papers:
Itano et al, "Quantum Zeno effect"
Phys. Rev. A 41, 2295 (1990)
Abstract:
The quantum Zero effect is the inhibition of transitions between quantum states by frequent measurements of the state. The inhibition arises because the measurement causes a collapse (reduction) of the wave function. If the time between measurements is short enough, the wave function usually collapses back to the initial state. We have observed this effect in an rf transition between two 9Be+ ground-state hyperfine levels. The ions were confined in a Penning trap and laser cooled. Short pulses of light, applied at the same time as the rf field, made the measurements. If an ion was in one state, it scattered a few photons; if it was in the other, it scattered no photons. In the latter case the wave-function collapse was due to a null measurement. Good agreement was found with calculations.
Shortly after, Ballentine published the following refutation of its claims about the effect being due to wave function collapse:
L. E. Ballentine, "Comment on 'Quantum Zeno effect' "
Phys. Rev. A 43, 5165–5167 (1991)
Abstract:
The quantum Zeno effect is not a general characteristic of continuous measurements. In a recently reported experiment [Itano et al., Phys. Rev. A 41, 2295 (1990)], the inhibition of atomic excitation and deexcitation is not due to any ‘‘collapse of the wave function,’’ but instead is caused by a very strong perturbation due to the optical pulses and the coupling to the radiation field. The experiment should not be cited as providing empirical evidence in favor of the notion of ‘‘wave-function collapse.’’
Then came the reply of Itano et al, in which they back-peddle away from the belief that the experiment "proves" wave function collapse:
Itano, et al, Reply to ``Comment on `Quantum Zeno effect'''
Phys. Rev. A 43, 5168-5169, (1991)
Abstract:
Various interpretations of quantum mechanics are valid insofar as they predict the same experimental results. Some invoke ``wave-function collapse'' and some do not. An interpretation based on the collapse postulate provides a simple explanation for a recent experimental demonstration of the quantum Zeno effect [Itano et al., Phys. Rev. A 41, 2295 (1990)], but other interpretations are also valid.
So the Itano experiment does not kill the ensemble interpretation in favour of collapse. They simply use collapse to give a "simple explanation". (Translation: dumbed-down, don't-ask-inconvenient-questions... )
IMHO, the most important bit in all this is the last sentence of the 1st Itano abstract above:
Good agreement was found with calculations.
One might claim that this therefore supports the SU&C* interpretation, but this option wasn't listed in the poll alternatives of this thread.
[*] Shut Up & Calculate.
