My understanding was that many-worlds is indistiguishable by observation from the Copenhagen interpretation. Has this changed?
According to MWI you can put arbitrarily large systems into quantum superposition, whereas according to CI when the system is sufficiently large the wavefunction will collapse.
According to MWI you can put arbitrarily large systems into quantum superposition
Yes and no. According to MWI, there is no theoretical limit to how a large a system in quantum superposition can be, yes. But to keep the system in quantum superposition without making two (or more) words that will never interact with each other again, you’ve to keep them from interacting with the rest of the world (in a way that is linked to the kind of superposition). And practically that is very hard to do for large-scale systems. That’s an issue with quantum computing for example, the more qbits you try to add, the harder it is to keep them isolated.
But the point would remain in that case that there is in principle an experiment to distinguish the theories, even if such an experiment has yet to be performed?
Although (and I admit my understanding of the topic is being stretched here) it still doesn’t sound like the central issue of the existance of parallel universes with which we may no longer interact would be resolved by such an experiment. It seems more like Copenhagen’s latest attempt to define the conditions for collapse would be disproven without particularly necessitating a fundamental change of interpretation.
If we managed to put human-sized systems into superposition, that’d rule out CI AFAICT. And before that, the larger the systems we manage to put into superposition the less likely CI will seem.
Good point. Decoherence makes MWI de facto indistinguishable from CI except that the maximum size of systems you can put into superpositions depends on the temperature rather than gravity/consciousness/whatever.
According to MWI you can put arbitrarily large systems into quantum superposition, whereas according to CI when the system is sufficiently large the wavefunction will collapse.
Yes and no. According to MWI, there is no theoretical limit to how a large a system in quantum superposition can be, yes. But to keep the system in quantum superposition without making two (or more) words that will never interact with each other again, you’ve to keep them from interacting with the rest of the world (in a way that is linked to the kind of superposition). And practically that is very hard to do for large-scale systems. That’s an issue with quantum computing for example, the more qbits you try to add, the harder it is to keep them isolated.
But the point would remain in that case that there is in principle an experiment to distinguish the theories, even if such an experiment has yet to be performed?
Although (and I admit my understanding of the topic is being stretched here) it still doesn’t sound like the central issue of the existance of parallel universes with which we may no longer interact would be resolved by such an experiment. It seems more like Copenhagen’s latest attempt to define the conditions for collapse would be disproven without particularly necessitating a fundamental change of interpretation.
For Copenhagen, yes, but MWI and Copenhagen aren’t the only two interpretations of quantum mechanics worth thinking about.
In truth, you’ll find few physicists who treat the Copenhagen Interpretation as anything but convenient shorthand, not usually for MWI.
If we managed to put human-sized systems into superposition, that’d rule out CI AFAICT. And before that, the larger the systems we manage to put into superposition the less likely CI will seem.
Good point. Decoherence makes MWI de facto indistinguishable from CI except that the maximum size of systems you can put into superpositions depends on the temperature rather than gravity/consciousness/whatever.