And another quantum-related question. - In The Fabric of the Cosmos by Brian Greene (p. 196), he describes a setup of the two slit experiment where half of the particles have their “which way” information recorded, thus causing decoherence and not showing an interference pattern, and the other half of the particles are not measured, and thus do show an interference pattern. After the fact one can look at which photons were not measured, and these do indeed form the interference pattern.
However, he then goes on to explain an identical setup, with the difference that the decision as to whether to measure the 1⁄2 of the particles can be made many (light) years after the photons register on the screen, and only later, when the person making this decision light years away comes and tells you whether they measured or not, do you see if the unmeasured photons make an interference pattern.
This would all make sense to me IF there was no way to distinguish a totally non-interfering pattern, and a non-interfering pattern overlaid with an interfering one. Intuitively it seems like one WOULD be able to distinguish this, with a pretty high degree of confidence, by subtracting an “average” non-interfering pattern from the total pattern. Is this not the case?
BTW, I have been re-reading the QM sequence every 6 months or so since it was first posted, and get a bit more out of it each time. I am AMAZED at how it has explained things that, before reading it, seemed so freaky and inexplicable to me that it bordered on the supernatural.
And another quantum-related question. - In The Fabric of the Cosmos by Brian Greene (p. 196), he describes a setup of the two slit experiment where half of the particles have their “which way” information recorded, thus causing decoherence and not showing an interference pattern, and the other half of the particles are not measured, and thus do show an interference pattern. After the fact one can look at which photons were not measured, and these do indeed form the interference pattern.
However, he then goes on to explain an identical setup, with the difference that the decision as to whether to measure the 1⁄2 of the particles can be made many (light) years after the photons register on the screen, and only later, when the person making this decision light years away comes and tells you whether they measured or not, do you see if the unmeasured photons make an interference pattern.
This would all make sense to me IF there was no way to distinguish a totally non-interfering pattern, and a non-interfering pattern overlaid with an interfering one. Intuitively it seems like one WOULD be able to distinguish this, with a pretty high degree of confidence, by subtracting an “average” non-interfering pattern from the total pattern. Is this not the case?
BTW, I have been re-reading the QM sequence every 6 months or so since it was first posted, and get a bit more out of it each time. I am AMAZED at how it has explained things that, before reading it, seemed so freaky and inexplicable to me that it bordered on the supernatural.