From: *Jason Resch* <[email protected] <mailto:[email protected]>>
On Mon, Jul 30, 2018 at 12:29 AM, Bruce Kellett <[email protected] <mailto:[email protected]>> wrote:From: *Jason Resch* <[email protected] <mailto:[email protected]>>On Mon, Jul 30, 2018 at 12:13 AM, Brent Meeker <[email protected] <mailto:[email protected]>> wrote: ?? Quantum computers cannot calculate anything more than classical computers. There are some algorithms that allow a QC to calculate something faster; but the domain and range is the same. So absent that reason does it follow that the wave function is merely a convenient (and very accurate) tool? Tool for what? Predicting probabilities of finally measured values? What then can we say about the intermediate values and the computation itself? Does it exist and happen, or does the final result merely materialize magically like the live or dead cat?Does the spot on the screen behind two slits materialize magically? Or arise as a consequence of the interference in the one world? In many-worlds, all possible screen spots occur in different worlds. But the separation into distinct worlds happens only on decoherence at the screen -- the interference all happens in the original single world. What is the photon in each world interfering with?
It's a wave, so it's interfering with itself. Just like water or sound waves.
It's many shadow partners in other worlds. World is a confusing term unless we define it.
I agree. Frequently, many-worlders follow Deutsch and have a schizophrenic attitude to "worlds" -- they are either any component of any possible superposition, or the semi-classical endpoint of the process of decoherence. In the first case, "worlds", as components of a superposition, can interfere. In the second case, worlds are effectively orthogonal and cannot interfere. Equivocating between these meanings causes endless confusion -- and idiot physics.
I always use the term "world" in the second sense, so worlds are orthogonal and cannot interfere.
We might also say the system of the photon is in many states, while the rest of the system (us, the screen) remain in one state, until we interact with the many-state photon system. So in that sense, you could argue the screen and us are in one world until the decoherence. But the system of the photons can't properly be described as any singe photon system.
Because the photon is a wave. The attempt to eliminate waves or fields from physics in favour of a purely particle ontology failed. Feynman was most disappointed by this, but if you think you can do better than Feynman.........
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